Patent Application
20250183264
The present application claims priority to and the benefit of Korean Patent Application Nos. 10-2023-0039376, filed on Mar. 26, 2023, and 10-2023-0122041, filed on Sep. 13, 2023, in the Korean Intellectual Property Office, the entire disclosures of which are incorporated by reference herein.
One or more embodiments of the present disclosure relate to a dry electrode, a method for manufacturing the dry electrode, and a lithium battery including the dry electrode.
In order to meet the miniaturization and high performance characteristics of various devices, high energy density is important in addition to miniaturization and weight reduction of lithium batteries. In this regard, high-capacity lithium batteries are important.
In order to implement lithium batteries suitable for the above use, electrodes having a high loading are being studied.
If manufacturing an electrode having a high loading, the possibility of defects such as collapse of an electrode active material layer increases in the process of introducing the electrode active material layer onto an electrode current collector due to an increase in the thickness of the electrode active material layer.
A method of easily introducing an electrode active material layer having a high loading onto an electrode current collector is desired.
One or more embodiments of the present disclosure include a dry electrode and a method for manufacturing the same, wherein the position of a dry electrode film introduced on an electrode current collector may be easily adjusted.
One or more embodiments include a dry electrode and a method for manufacturing the same, wherein various suitable types (or kinds) of dry electrode films may be easily introduced without (or substantially without) damaging an electrode current collector.
One or more embodiments include a method for manufacturing the dry electrode.
One or more embodiments include a lithium battery including the dry electrode.
Additional aspects of embodiments will be set forth in part in the description which follows and, in part, will be apparent from the description, or may be learned by practice of the presented embodiments of the present disclosure.
According to one or more embodiments, a dry electrode includes an electrode current collector, a dry electrode film on one side or two opposing sides of the electrode current collector, and an interlayer between the electrode current collector and the dry electrode film, wherein the interlayer includes an outer peripheral region provided along at least a portion of an outer periphery of the interlayer and an inter-region excluding the outer peripheral region, wherein a thickness of the outer peripheral region is greater than a thickness of the inter-region.
According to one or more embodiments, a method for manufacturing a dry electrode includes providing an interlayer on an electrode current collector to prepare a first laminate, preparing a second laminate by providing, on the first laminate, a dry electrode film having a larger area than an area of the interlayer, wherein the dry electrode film includes a first region on the interlayer, and a second region extending from the first region beyond an outer periphery of the interlayer, and pulling at least a portion of the second region of the dry electrode film to separate the second region from the first region, thereby providing a dry electrode, wherein the interlayer includes an outer peripheral region provided along at least a portion of the outer periphery of the interlayer, and an inter-region excluding the outer peripheral region, wherein a thickness of the outer peripheral region is greater than a thickness of the inter-region.
According to one or more embodiments, a lithium battery includes a positive electrode, a negative electrode, and an electrolyte between the positive electrode and the negative electrode, wherein one or more of the positive electrode and the negative electrode include the above-described dry electrode.
The above and other aspects and features of certain embodiments of the present disclosure will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:
Reference will now be made in more detail to embodiments, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to like elements throughout. In this regard, the present embodiments may have different forms and should not be construed as being limited to the descriptions set forth herein. Accordingly, the embodiments are merely described below, by referring to the figures, to explain aspects of embodiments of the present description. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. Expressions such as “at least one of,” if preceding a list of elements, modify the entire list of elements and do not modify the individual elements of the list.
The subject matter of the present disclosure described hereinafter may be modified in various suitable ways, and may have many examples, and thus, certain examples are illustrated in the drawings, and are described in more detail. The present disclosure, however, should not be construed as limited to the example embodiments set forth herein, and rather, should be understood as covering all modifications, equivalents, or alternatives falling within the scope of the present disclosure.
The terms used herein are used for the purpose of describing example embodiments only, and are not intended to limit the present disclosure. An expression used in the singular encompasses the expression of the plural, unless it has a clearly different meaning in the context. It will be further understood that the terms “comprises” and/or “comprising,” or “includes” and/or “including” if used in this specification, specify the presence of stated features, regions, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components, and/or groups thereof. The sign “/” used herein may be interpreted as “and,” or as “or” depending on the context.
In the drawings, thicknesses may be magnified and/or exaggerated to clearly illustrate various layers and regions. Like reference numbers may refer to like elements throughout the drawings and the following description. It will be understood that if one element, layer, film, section, sheet, etc. is referred to as being “on” another element, it can be directly on the other element or intervening elements may be present therebetween. Although the terms “first,” “second,” etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. Components having substantially the same functional configuration in the present specification and drawings refer to the same reference numerals, and redundant description thereof may not be repeated.
In the present disclosure, the “particle diameter” of a particle represents an average diameter if the particles are spherical and represents an average major axis length if the particles are non-spherical. The particle diameter of the particles may be measured using a particle size analyzer (PSA). The “particle diameter” of particles may be, for example, the average particle diameter. An average particle diameter may be, for example, a median particle diameter (D50). The median particle diameter (D50) refers to the particle size corresponding to the cumulative volume of 50%, calculated from the smallest side of the particle in the size distribution of the particle as measured, for example, by laser diffraction.
The term “metal” used herein includes both metals and metalloids such as silicon and germanium in an elemental or ionic state.
The term “alloy” used herein refers to a mixture of two or more metals.
The term “positive electrode active material” used herein refers to a positive electrode material capable of undergoing lithiation and delithiation.
The term “negative electrode active material” used herein refers to a negative electrode material capable of undergoing lithiation and delithiation.
The terms “lithiation” and “lithiate” used herein refer to a process of adding lithium to a positive electrode active material or a negative electrode active material.
The terms “delithiation” and “delithiate” used herein refer to a process of removing lithium from a positive electrode active material or a negative electrode active material.
The terms “charging” and “charge” used herein refer to a process of providing electrochemical energy to a battery.
The term “discharging” and “discharge” used herein refer to a process of removing electrochemical energy from a battery.
The term “positive electrode” used herein refer to an electrode in which electrochemical reduction and lithiation occur during a discharging process.
The term “negative electrode” used herein refer to an electrode in which electrochemical oxidation and delithiation occurs during the discharge process.
Hereinafter, a dry electrode according to embodiments will be described in more detail.
A dry electrode 500 according to an aspect of embodiments of the present disclosure may include an electrode current collector 100, a dry electrode film 300 on one side or two opposing sides of the electrode current collector 100, and an interlayer 200 between the electrode current collector 100 and the dry electrode film 300, wherein the interlayer 200 includes an outer peripheral region 220 provided along at least a portion of an outer periphery 260 of the interlayer 200 and an inter-region 210 excluding the outer peripheral region 220, wherein the thickness of the outer peripheral region 220 may be greater than the thickness of the inter-region 210. The dry electrode film 300 may include an inter-region 310 on the interlayer 200 and an outer peripheral region 320 on the outer peripheral region 220 of the interlayer 200.
For example, a portion of the dry electrode film 300 may be exposed to the outside of the interlayer 200 in a process of stacking the dry electrode film 300 on the interlayer 200, and a process of removing the exposed dry electrode film 300 may be performed. In this embodiment, a process for distinguishing a region of the dry electrode film 300 on the interlayer 200 and a portion of the dry electrode film 300 exposed to the outside of the interlayer 200 may be beneficial because another interlayer 200 may have a constant thickness, and as a result, there is a problem in that a process for manufacturing a dry electrode 500 may be delayed (e.g., because it is more difficult to identify and/or separate the portion of the dry electrode film that is exposed to the outside of the interlayer).
For example, the thickness of the outer peripheral region 220 of the dry electrode 500 may be greater than the thickness of the inter-region 210, so that a region of the dry electrode film 300 on the interlayer 200 and a region of the dry electrode film 300 exposed to the outside of the interlayer 200 may be more easily distinguished in a process of manufacturing the dry electrode 500. In this regard, without an additional procedure for distinguishing the region on the interlayer 200 of the dry electrode film 300 and the region exposed to the outside of the interlayer 200, the region exposed to the outside of the interlayer 200 of the dry electrode film 300 may be more easily removed, so that the manufacturing efficiency of the dry electrode 500 may be improved. By adjusting a region in which the outer peripheral region 220 is provided, it is possible to more easily form a patterned dry electrode film 300 on the electrode current collector 100.
For example, an outer periphery 260 of an interlayer may mean a boundary line distinguishing a region in which the interlayer is formed and a region in which the interlayer is not formed. The outer periphery 260 may mean a boundary line provided at the outermost portion of the interlayer 200. For example, the outer periphery 260 may include a first outer periphery 261 parallel to a machine X direction and a second outer periphery 262 parallel to a transverse Y direction, as shown in
For example, the machine direction may be, for example, an x direction, the transverse direction is, for example, a y direction, and the thickness direction may be, for example, a z direction. For example, the machine direction may be a direction in which dry electrode films 300a, 300b, and 300 are stretched during the manufacturing of the dry electrode films 300a, 300b, and 300, as shown in
For example, the outer peripheral region 220 may be provided along at least a portion of the outer periphery 260. For example, the outer peripheral region 220 may be continuously or discontinuously provided along at least a portion of the outer periphery 260.
For example, the outer periphery 260 may include the first outer periphery 261 parallel to the machine X direction and the second outer periphery 262 parallel to the transverse Y direction.
Referring to
According to another embodiment, the outer peripheral region 220 may be provided along the second outer periphery 262. The outer peripheral region 220 may be parallel to the transverse direction. For example, the outer peripheral region 220 may be provided along only the second outer periphery 261 parallel to the transverse direction.
Referring to
According to embodiments, the ratio of the area of the outer peripheral region 220 to the total area of the interlayer 200 may be about 1% to about 20%. For example, if the area of the outer peripheral region 220 satisfies the above range, it is easier to distinguish between a region on the interlayer 200 of the dry electrode film 300 and a region outside the interlayer 200 in the process of manufacturing the dry electrode 500. For example, according to embodiments, the ratio of the area of the outer peripheral region 220 to the total area of the interlayer 200 may be about 5% to about 20%, about 1% to about 15%, about 5% to about 15%, about 1% to about 10%, or about 5% to about 10%.
According to embodiments, the ratio of the thickness of the outer peripheral region 220 to the thickness of the inter-region 210 may be greater than about 1 but not more than about 5. For example, if the ratio of the thickness of the outer peripheral region 220 to the thickness of the inter-region 210 satisfies the above ranges, the dry electrode film 300 provided outside the interlayer 200 may be more easily removed.
For example, the ratio of the thickness of the outer peripheral region 220 to the thickness of the inter-region 210 may be greater than about 1 to about 4 or less, greater than about 1 to about 3 or less, or greater than about 1 to about 2 or less.
According to embodiments, the interlayer 200 may be provided, for example, on one side or two opposing sides of the electrode current collector 100.
Referring to
The thickness of the interlayers 200a, 200b, and 200 may be, for example, about 30% or less, about 25% or less, about 20% or less, about 15% or less, about 10% or less, about 5% or less, or about 3% or less of the thickness of the electrode current collector 100.
For example, the thickness of the interlayers 200a, 200b, and 200 may be about 0.01% to about 30%, about 0.1% to about 30%, about 0.5% to about 30%, about 1% to about 25%, about 1% to about 20%, about 1% to about 15%, about 1% to about 10%, about 1% to about 5%, or about 1% to about 3% of the thickness of the electrode current collector 100. The thickness of the interlayers 200a, 200b, and 200 may be, for example, about 10 nm to about 5 μm, about 50 nm to about 5 μm, about 200 nm to about 4 μm, about 500 nm to about 3 μm, about 500 nm to about 2 μm, about 500 nm to about 1.5 μm, or about 700 nm to about 1.3 μm. Because the interlayers 200a, 200b, and 200 may have a thickness in the above ranges, a binding force between the electrode current collector 100 and the dry electrode films 300a, 300b, and 300 is further improved, and an increase in interfacial resistance may be suppressed or reduced.
According to embodiments, the interlayers 200a, 200b, and 200 may include, for example, a binder. Because the interlayers 200a, 200b, and 200 may include a binder, the binding force between the electrode current collector 100 and the dry electrode films 300a, 300b, and 300 may be further improved.
For example, the binder included in the interlayers 200a, 200b, and 200 may be a conductive binder and/or a non-conductive binder. The conductive binder may be, for example, an ionically conductive binder and/or an electronically conductive binder. A binder that has both ionic conductivity and electronic conductivity may belong to both an ionically conductive binder and an electronically conductive binder.
For example, the ionically conductive binder may be polystyrene sulfonate (PSS), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), polyvinyl fluoride (PVF), polyvinylidene fluoride (PVDF), polymethyl methacrylate (PMMA), polyethylene oxide (PEO), polyethylene glycol (PEG), polyacrylonitrile (PAN), polytetrafluoroethene (PTFE), polyethylene dioxythiophene (PEDOT), polypyrrole (PPY), polyacrylonitrile (PAN), polyaniline, polyacetylene, and/or the like.
For example, the ionically conductive binder may include a polar functional group. The ionically conductive binder including a polar functional group may be, for example, nafion, aquivion, flemion, gore, aciplex, morgane ADP, sulfonated poly(ether ether ketone) (SPEEK), sulfonated poly(arylene ether ketone ketone sulfone) (SPAEKKS), sulfonated poly(aryl ether ketone) (SPAEK), poly[bis(benzimidazobenzisoquinolinones)](SPBIBI), poly(styrene sulfonate) (PSS), lithium 9,10-diphenylanthracene-2-sulfonate (DPASLi+), and/or the like. The electronically conductive binder may be, for example, polyacetylene, polythiophene, polypyrrole, poly(p-phenylene), poly(phenylenevinylene), poly(phenylenesulfide), polyaniline, and/or the like. The interlayers 200a, 200b, and 200 may be, for example, a conductive layer (e.g., an electrically conductive layer) including a conductive polymer (e.g., an electrically conductive polymer).
According to embodiments, the binder included in the interlayers 200a, 200b, and 200 may be selected from binders included in the dry electrode film 300a, 300b, and 300 to be further described herein below. For example, the interlayers 200a, 200b, and 200 may include the same binder as the binder included in the dry electrode films 300a, 300b, and 300 to be further described herein below. For example, the binder included in the interlayers 200a, 200b, and 200 may be a fluorine-based binder.
According to embodiments, the fluorine-based binder included in the interlayers 200a, 200b, and 200 may be polyvinylidene fluoride (PVDF). The interlayers 200a, 200b, and 200 are provided, for example, on the electrode current collector 100, for example, in a dry or wet manner. The interlayers 200a, 200b, and 200 may be, for example, a binding layer including a binder.
According to embodiments, the interlayers 200a, 200b, and 200 may further include, for example, a carbon-based conductive material (e.g., a carbon-based electrically conductive material). The carbon-based conductive material included in the interlayers 200A, 200B, and 200 may be selected from carbon-based conductive materials included in the dry electrode films 300A, 300B, and 300. The interlayers 200A, 200B, and 200 may include the same carbon-based conductive material as the carbon-based conductive material included in an electrode active material layer. Because the interlayers 200A, 200B, and 200 include a carbon-based conductive material, the interlayers 200A, 200B, and 200 may be, for example, a conductive layer. The interlayers 200A, 200B, and 200 may be, for example, a conductive layer (e.g., an electrically conductive layer) including a binder and a carbon-based conductive material (e.g., a carbon-based electrically conductive material).
The interlayers 200A, 200B, and 200 may be provided, for example, on the electrode current collector 100 in a dry manner by deposition such as CVD, PVD, and/or the like. The interlayers 200A, 200B, and 200 may be provided, for example, on the electrode current collector 100 in a wet manner by coating such as spin coating, dip coating, and/or the like. The interlayers 200A, 200B, and 200 may be on the electrode current collector 100 by depositing, for example, a carbon-based conductive material on the electrode current collector 100 by deposition.
The dry-coated interlayers 200a, 200b, and 200 may be made of a carbon-based conductive material (e.g., a carbon-based electrically conductive material) and may not include a binder. In some embodiments, the interlayers 200a, 200b, and 200 may be on the electrode current collector 100 by coating and drying a composition including, for example, a carbon-based conductive material (e.g., a carbon-based electrically conductive material), a binder, and a solvent on the surface of the electrode current collector 100. The interlayers 200a, 200b, and 200 may have a single-layered structure or a multi-layered structure including a plurality of layers.
According to embodiments, a composition of the inter-region 210 of the interlayer 200 may be the same as a composition of the outer peripheral region 220. In this embodiment, the interlayer 200 uses a single composition, and thus, the interlayers 200 may all be easily formed on the electrode current collector 100.
According to embodiments, the composition of the inter-region 210 of the interlayer 200 may be different from the composition of the outer peripheral region 220. In this embodiment, the strength of the outer peripheral region 220 of the interlayer 200 may be greater than the strength of the inter-region 210. In this regard, in the process of manufacturing the dry electrode 500, it is possible to more easily distinguish and remove the dry electrode film 300 exposed to the outside of the interlayer 200.
Referring to
According to embodiments, a thickness of a region of the dry electrode films 300a, 300b, and 300 on the inter-region 210 may be greater than a thickness of a region of the dry electrode films 300a, 300b, and 300 on the outer peripheral region 220.
For example, the sum of the thickness of the region on the inter-region 210 of the dry electrode films 300a, 300b, and 300 and the thickness of the inter-region 210 may be the same as the sum of the thickness of the region on the outer peripheral region 220 and the thickness of the outer peripheral region 220. In this regard, the overall thickness of the manufactured dry electrode 500 may be constant (or substantially constant).
Referring to
For example, the dry electrode films 300a, 300b, and 300 are manufactured in a dry manner, and thus, do not include a processing solvent intentionally added. For example, a residual processing solvent is not included in the dry electrode films 300a, 300b, and 300. An unintended trace amount of solvent may remain in the dry electrode films 300a, 300b, and 300, but the solvent is not a processing solvent intentionally added. Therefore, the dry electrode films 300a, 300b, and 300 manufactured from the dry electrode films 300a, 300b, and 300 are distinguished from a wet electrode active material layer manufactured by mixing together an electrode component and a processing solvent and then removing a part or all of the process solvent by drying.
The dry electrode films 300a, 300b, and 300 may include a dry electrode active material. The dry electrode active material may be, for example, an electrode active material that is not impregnated, dissolved, or dispersed in a processing solvent. The dry electrode active material may be, for example, an electrode active material that does not include a processing solvent or that does not come into contact with the processing solvent. The dry electrode active material may be, for example, an electrode active material that does not come into contact with the processing solvent in the process of manufacturing the dry electrode films 300a, 300b, and 300 and the dry electrode 500.
The dry electrode active material may be, for example, a dry positive electrode active material.
A positive electrode active material may be, for example, a lithium metal oxide. Any suitable positive electrode active material generally used in the art may be used without limitation.
For example, one or more types (or kinds) of composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and/or a combination thereof may be used as the positive electrode active material, and an example thereof may be a compound represented by any of the following formulas: LiaA1-bB′bD2 (wherein 0.90≤a≤1 and 0≤b≤0.5); LiaE1-bB′bO2-cDc (wherein 0.90≤a≤1, 0≤b≤0.5, and 0≤c≤0.05); LiE2-bB′bO4-cDc (wherein 0≤b≤0.5 and 0≤c≤0.05); LiaNi1-b-cCobB′cDα (wherein 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, and 0<α≤2); LiaNi1-b-cCobB′cO2-aF′α (wherein 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, and 0<α<2); LiaNi1-b-cCobB′cO2-aF′α (wherein 0.90≤a≤1, 0≤b≤0.5, 0≤5c≤0.05, and 0<α<2); LiaNi1-b-cMnbB′cDα (wherein 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, and 0<α≤2); LiaNi1-b-cMnbB′cO2-aF′α (wherein 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, and 0<α<2); LiaNi1-b-cMnbB′cO2-αF′2 (wherein 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, and 0<α<2); and LiaNibEcGdO2 (wherein 0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, and 0.001≤d≤0.1); LiaNibCocMndGeO2 (wherein 0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0 d≤0.5, and 0.001≤e≤0.1); LiaNiGbO2 (wherein 0.90≤a≤1 and 0.001≤b≤0.1); LiaCoGbO2 (wherein 0.90≤a≤1 and 0.001≤b≤0.1); LiaMnGbO2 (wherein 0.90≤a≤1 and 0.001≤b≤0.1); LiaMn2GbO4 (wherein 0.90≤a≤1 and 0.001≤b≤0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiI′O2; LiNiVO4; Li(3-f)J2(PO4)3(0≤f≤2); Li(3-f)Fe2(PO4)3(0≤f≤2); and LiFePO4.
In the above-described Formulas representing a compound, A is Ni, Co, Mn, or a combination thereof; B′ is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F′ is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I′ is Cr, V, Fe, Sc, Y, or a combination thereof; and J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.
A compound in which a coating layer is added to the surface of the above-described compounds may be used, and a mixture of the above-described compounds and the compound added with the coating layer may also be used. The coating layer added to the surface of the above-described compounds may include, for example, a coating element compound such as an oxide and/or hydroxide of a coating element, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a hydroxycarbonate of the coating element. A compound constituting the coating layer may be amorphous and/or crystalline. The coating element included in the coating layer may be Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. A method for providing the coating layer may be selected from any suitable method that does not (e.g., substantially does not) adversely affect the physical properties of the positive electrode active material. The coating method may be, for example, a spray coating method, a dipping method, and/or the like. A detailed description of the coating method is not necessary here because it will be readily understood by those skilled in the art upon reviewing this disclosure.
The positive electrode active material may be, for example, a composite positive electrode active material.
The composite positive electrode active material may include, for example, a core including a lithium transition metal oxide, and a shell provided along the surface of the core, wherein the shell includes at least one first metal oxide represented by Formula MaOb (0<a≤3 and 0<b<4, wherein if a is 1, 2, or 3, b is not an integer), and graphene, wherein the first metal oxide is in a graphene matrix, and the M is at least one metal selected from Groups 2 to 13, 15, and 16 of the Periodic Table of Elements, and the lithium transition metal oxide contains nickel, wherein the content of nickel is about 80 mol % or greater with respect to the total number of moles of the transition metal. The shell including the first metal oxide and the graphene may be on the core of the composite positive electrode active material.
Due to agglomeration, it is difficult to uniformly coat other graphene on the core. For example, the composite positive electrode active material uses a composite including a plurality of first metal oxides in the graphene matrix, thereby allowing the shell to be uniformly (e.g., substantially uniformly) provided on the core while preventing or reducing the agglomeration of graphene. Therefore, by effectively blocking or reducing the contact between the core and an electrolyte solution, a side reaction caused by the contact between the core and the electrolyte is prevented or reduced. The reduction of nickel ions (Ni3+->Ni2+) and cation mixing caused by the electrolyte solution are suppressed or reduced, so that the generation of a resistance layer such as a NiO phase is suppressed or reduced. The elution of nickel ions is also suppressed or reduced. Because the shell including graphene has flexibility, changes in the volume of the composite positive electrode active material during charging and discharging are easily accommodated, thereby suppressing or reducing the occurrence of cracks inside the composite positive electrode active material. Because graphene has high electronic conductivity, the interfacial resistance between the composite positive electrode active material and the electrolyte solution is reduced. Therefore, despite the introduction of the shell including graphene, the internal resistance of a lithium battery is maintained or reduced. Because the first metal oxide has voltage resistance, the deterioration of the lithium transition metal oxide included in the core may be prevented or reduced during charging and discharging at high voltages. As a result, the cycle properties and high-temperature stability of a lithium battery including the composite positive electrode active material are improved. The shell may include, for example, one type (or kind) of first metal oxide or two or more types (or kinds) of different first metal oxides. In the composite positive electrode active material, the lithium transition metal oxide has a high nickel content of about 80 mol % or greater with respect to the total number of moles of the transition metal, and the shell including the first metal oxide and graphene is on the core, so that high discharge capacity and cycle properties may be concurrently (e.g., simultaneously) provided. Therefore, a composite positive electrode active material having a high nickel content of about 80 mol % or greater may provide improved capacity compared to a composite positive electrode active material having a relatively low nickel content, while still providing excellent lifespan properties. A metal included in the first metal oxide may be, for example, one or more selected from Al, Nb, Mg, Sc, Ti, Zr, V, W, Mn, Fe, Co, Pd, Cu, Ag, Zn, Sb, and Se.
The first metal oxide may be, for example, one or more selected from Al2Oz (0<z<3), NbOx (0<x<2.5), MgOx (0<x<1), Sc2Oz (0<z<3), TiOy (0<y<2), ZrOy (0<y<2), V2Oz (0<z<3), WOy (0<y<2), MnOy (0<y<2), Fe2Oz (0<z<3), Co3Ow (0<w<4), PdOx (0<x<1), CuOx (0<x<1), AgOx (0<x<1), ZnOx (0<x<1), Sb2Oz (0<z<3), and SeOy (0<y<2). Because the first metal oxide as described above is in the graphene matrix, the uniformity of the shell on the core is improved, and the voltage resistance of the composite positive electrode active material is further improved. For example, the shell includes Al2Ox (0<x<3) as the first metal oxide. The shell may further include one or more types (or kinds) of second oxide metal represented by Formula MaOc (0<a≤3 and 0<c≤4, wherein if a is 1, 2, or 3, c is an integer). The M is one or more metals selected from Groups 2 to 13, 15 and 16 of the Periodic Table of Elements. For example, the second metal oxide includes the same metal as the metal included in the first metal oxide, and c/a, which the ratio of a and c of the second metal oxide has a greater value than b/a, which is the ratio of a and b of the first metal oxide. For example, c/a>b/a. The second metal oxide is selected from, for example, Al2O3, NbO, NbO2, Nb2O5, MgO, Sc2O3, TiO2, ZrO2, V2O3, WO2, MnO2, Fe2O3, Co3O4, PdO, CuO, AgO, ZnO, Sb2O3, and SeO2. The first metal oxide is a reduction product of the second metal oxide. The first metal oxide is obtained by reducing a part or all of the second metal oxide. Therefore, the first metal oxide has a lower oxygen content, and has a higher oxidation number of the metal than the second metal oxide. For example, the shell includes Al2Ox (0<x<3), which is the first metal oxide, and Al2O3, which is the second metal oxide. In the composite positive electrode active material, for example, the graphene included in the shell and the transition metal of the lithium transition metal oxide included in the core are chemically bound through a chemical bond. A carbon atom C of the graphene included in the shell and a transition metal Me of the lithium transition metal oxide are chemically bound, for example, through a C—O-Me bond (e.g., C—O—Ni bond) using an oxygen atom as a medium (e.g., as a linking atom). The graphene included in the shell and the lithium transition metal oxide included in the core are chemically bonded through a chemical bond, so that the core and the shell are composited. Therefore, it is distinguished from a simple physical mixture of graphene and a lithium transition metal oxide. The first metal oxide and the graphene included in the shell are also chemically bound through a chemical bond. The chemical bond may be, for example, a covalent bond or an ionic bond. The covalent bond is a bond including, for example, at least one selected from an ester group, an ether group, a carbonyl group, an amide group, a carbonate anhydride group, and an acidic anhydride. The ionic bond is a bond including, for example, carboxylic acid ions, ammonium ions, acyl cation groups, and the like. The thickness of the shell is, for example, about 1 nm to about 5 um, about 1 nm to about 1 um, about 1 nm to about 500 nm, about 1 nm to about 200 nm, about 1 nm to about 100 nm, about 1 nm to about 90 nm, about 1 nm to about 80 nm, about 1 nm to about 70 nm, about 1 nm to about 60 nm, about 1 nm to about 50 nm, about 1 nm to about 40 nm, about 1 nm to about 30 nm, about 1 nm to about 20 nm, or about 1 nm to about 10 nm. Because the shell has a thickness in the above ranges, an increase in the internal resistance of the lithium battery including the composite positive electrode active material is suppressed or reduced.
The content of the composite included the composite positive electrode active material may be about 3 wt % or less, about 2 wt % or less, about 1 wt % or less, about 0.5 wt % or less, or about 0.2 wt % or less of the total weight of the composite positive electrode active material. The content of the composite may be about 0.01 wt % to about 3 wt %, about 0.01 wt % to about 1 wt %, about 0.01 wt % to about 0.7 wt %, about 0.01 wt % to about 0.6 wt %, about 0.1 wt % to about 0.5 wt %, about 0.01 wt % to about 0.2 wt %, about 0.01 wt % to about 0.1 wt %, or about 0.03 wt % to about 0.07 wt % of the total weight of the composite positive electrode active material. Because the composite positive electrode active material includes the composite in the above ranges, the cycle properties of the lithium battery including the composite positive electrode active material are further improved. The average particle diameter of one or more selected from the first metal oxide and the second metal oxide included in the composite may be about 1 nm to about 1 um, about 1 nm to about 500 nm, about 1 nm to about 200 nm, about 1 nm to about 100 nm, about 1 nm to about 70 nm, about 1 nm to about 50 nm, about 1 nm to about 30 nm, about 3 nm to about 30 nm, about 3 nm to about 25 nm, about 5 nm to about 25 nm, about 5 nm to about 20 nm, or about 7 nm to about 20 nm. The first metal oxide and/or the second metal oxide has a particle diameter in the above nano-range, and thus, may be more uniformly distributed in the graphene matrix of the composite. Therefore, the composite may be uniformly (e.g., substantially uniformly) coated on the core without (or substantially without) agglomeration to form a shell. The first metal oxide and/or the second metal oxide has a particle diameter in the above ranges, and thus, may be more uniformly on the core. Therefore, because the first metal oxide and/or the second metal oxide is uniformly (e.g., substantially uniformly) provided on the core, voltage resistance properties may be more effectively exhibited. The average particle diameter of the first metal oxide and the second metal oxide may be measured by using, for example, a measuring device of laser diffraction and/or dynamic light scattering. The average particle diameter is measured by using, for example, a laser scattering particle size distribution meter (e.g., Horiba's LA-920), and is the value of the median particle size (D50) if 50% is accumulated from the small particle side in volume conversion.
The core included in the composite positive electrode active material may include, for example, a lithium transition metal oxide represented by Formulas 1 to 8 below:
LiaCoxMyO2-bAb Formula 1
LiaNixCOyMzO2-bAb Formula 2
LiNixCoyMnzO2 Formula 3
LiNixCoyAlzO2 Formula 4
LiNixCoyMnzAlwO2 Formula 5
LiaNixMnyM′zO2-bAb Formula 6
LiaM1xM2yPO4-bXb Formula 7
LiaM3zPO4 Formula 8
The dry electrode active material may be, for example, a dry negative electrode active material.
The negative electrode active material may be any suitable negative electrode active material used as a negative electrode active material of a lithium battery in the art. For example, one or more selected from the group consisting of a lithium metal, a metal alloyable with lithium, a transition metal oxide, a non-transition metal oxide, and a carbon-based material may be included. The metal alloyable with lithium may be, for example, Si, Sn, Al, Ge, Pb, Bi, Sb, an Si—Y alloy (wherein the Y is an alkali metal, an alkali earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, or a combination thereof, but not Si), an Sn—Y alloy (wherein the Y is an alkali metal, an alkali earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, or a combination thereof, but not Sn), and/or the like. The element Y may be, for example, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, or a combination thereof. The transition metal oxide may be, for example, lithium titanium oxide, vanadium oxide, lithium vanadium oxide, and/or the like. The non-transition metal oxide may be, for example, SnO2, SiOx(0<x<2), and/or the like. The carbon-based material may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. The crystalline carbon may be, for example, graphite such as amorphous, plate-shaped, flake-shaped, spherical, and/or fibrous natural graphite and/or artificial graphite. The amorphous carbon may be, for example, soft carbon (low-temperature fired carbon) and/or hard carbon, mesophase pitch carbide, fired coke, and/or the like.
The dry electrode films 300a, 300b, and 300 include, for example, a dry binder. The dry binder may be, for example, a binder that is not impregnated, dissolved, or dispersed in a processing solvent. The dry binder may be, for example, a binder that does not include a processing solvent or does not come into contact with the processing solvent. The dry binder may be, for example, a binder that does not come into contact with a processing solvent in the process of manufacturing the dry electrode films 300a, 300b, and 300 and the dry electrode. The dry binder may be, for example, a fibrillized binder. The fibrillized binder may serve as a matrix that supports and binds the dry electrode active material and other components included in the dry electrode films 300a, 300b, and 300. It can be confirmed that the fibrillized binder has a fibrous form, for example, from a scanning electron microscope image of the cross-section of the electrode. The fibrillized binder may have an aspect ratio of, for example, about 10 or greater, about 20 or greater, about 50 or greater, or about 100 or greater.
The dry binder may be, but is not limited to, polytetrafluoroethylene (PTFE), polyvinylidene fluoride-hexapropylene (PVDF-HFP) copolymer, polyvinylidene fluoride (PVDF), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, cellulose, polyvinylpyrrolidone, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluorine rubber, and/or a copolymer thereof, but may be any suitable binder used in the manufacture of the dry electrode 500. For example, the dry binder may include a fluorine-based binder. The fluorine-based binder may be, for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride-hexapropylene (PVDF-HFP) copolymer, and/or polyvinylidene fluoride (PVDF).
The content of the dry binder included in the dry electrode films 300a, 300b, and 300 may be, for example, about 1 wt % to about 10 wt %, or about 1 wt % to about 5 wt % with respect to the total weight of the dry electrode films 300a, 300b, and 300. Because the dry electrode films 300a, 300b, and 300 include the dry binder in the above ranges, the binding force of the dry electrode films 300a, 300b, and 300 is improved, and the manufactured dry electrode 500 may maintain a high energy density.
The dry electrode films 300a, 300b, and 300 may further include, for example, a conductive material (e.g., an electrically conductive material). The conductive material may be, for example, a dry conductive material (e.g., a dry electrically conductive material). The dry conductive material may be, for example, a conductive material (e.g., an electrically conductive material) that is not impregnated, dissolved, or dispersed in a processing solvent. The dry conductive material may be, for example, a conductive material (e.g., an electrically conductive material) that does not include a processing solvent or does not come into contact with the processing solvent. The dry conductive material includes, for example, a carbon-based conductive material (e.g., a carbon-based electrically conductive material). The carbon-based conductive material may be, but is not limited to, carbon black, graphite fine particles, natural graphite, artificial graphite, acetylene black, Ketjen black, carbon fiber, carbon nanotubes, and/or the like, and may be any suitable carbon-based conductive material used in the art.
The content of the dry conductive material included in the dry electrode films 300a, 300b, and 300 may be, for example, about 1 wt % to about 10 wt %, or about 1 wt % to about 5 wt % with respect to the total weight of the electrode active material layer. Because the dry electrode films 300a, 300b, and 300 include the dry conductive material in the above ranges, the conductivity (e.g., the electrical conductivity) of the manufactured dry electrode 500 is improved, and the cycle properties of the lithium battery including the dry electrode 500 may be improved.
Materials constituting the electrode current collector 100 may be materials that do not react with lithium, e.g., materials that do not form an alloy or compound with lithium and are conductive. The electrode current collector 100 is, for example, a metal and/or alloy. The electrode current collector 100 may be made of, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), and/or an alloy thereof.
The electrode current collector 100 may have a form selected from, for example, a sheet, a foil, a film, a plate body, a porous body, a mesoporous body, a through-hole-containing body, a polygonal ring body, a mesh body, a foam body, and a non-woven fabric body, but is not necessarily limited to such a form, and may be any suitable form used in the art.
The electrode current collector 100 may have a reduced thickness compared to an electrode current collector 100 included in another electrode. Therefore, the electrode according to embodiments includes a thin-film current collector, and thus, is distinguished from another electrode including a thick-film current collector. Because the electrode according to embodiments may adopt a thin-film current collector having a reduced thickness, the thickness of an electrode active material layer may be relatively increased in the electrode including the thin-film current collector. As a result, the energy density of a lithium battery which adopts the electrode increases. The thickness of the electrode current collector 100 may be, for example, about less than 15 μm, about 14.5 μm or less, or about 14 μm or less. The thickness of the electrode current collector 100 may be, for example, about 0.1 μm to about less than 15 μm, about 1 μm to about 14.5 μm, about 2 μm to about 14 μm, about 3 μm to about 14 μm, about 5 μm to about 14 μm, or about 10 μm to about 14 μm.
The electrode current collector 100 has a reduced surface roughness compared to the electrode current collector 100 included in other electrodes. Because the surface of the electrode current collector 100 may have a reduced surface roughness, the electrode current collector 100 may form a uniform (e.g., substantially uniform) interface with the electrode active material layer and/or the interlayers 200a, 200b, and 200. As a result, local side reactions and/or non-uniform electrode reactions are suppressed or reduced at the interface of the electrode current collector 100 and other layers, and the cycle properties of the lithium battery including the electrode are improved.
A maximum roughness depth Rmax of the surface of the electrode current collector 100 may be, for example, about 3 μm or less, about 2 μm or less, about 1 μm or less, about 0.5 um or less, or about 0.1 um or less. The maximum roughness depth Rmax of the surface of the electrode current collector 100 may be, for example, about 10 nm to about 3 μm, about 10 nm to about 2 μm, about 10 nm to about 1 μm, about 10 nm to about 0.5 μm, or about 10 nm to about 0.1 μm.
A mean roughness Ra of the surface of the electrode current collector 100 may be, for example, about 2 μm or less, about 1 μm or less, about 0.5 um or less, or about 0.1 um or less. The mean roughness Ra of the surface of the electrode current collector 100 may be, for example, about 10 nm to about 2 μm, about 10 nm to about 1 μm, about 10 nm to about 0.5 μm, or about 10 nm to about 0.1 μm.
A root mean square (RMS) roughness Rq of the surface of the electrode current collector 100 may be, for example, about 2 μm or less, about 1 μm or less, about 0.5 um or less, or about 0.1 um or less. The root mean square (RMS) roughness Rq of the surface of the electrode current collector 100 may be, for example, about 10 nm to about 2 μm, about 10 nm to about 1 μm, about 10 nm to about 0.5 μm, or about 10 nm to about 0.1 μm.
The electrode current collector 100 may include, for example, a base film and a metal layer on one side or two opposing sides of the base film. The electrode current collector 100 may include a substrate, and the substrate may have, for example, a structure including a base film and a metal layer on one side or two opposing sides of the base film. The above-described interlayer may be additionally on the metal layer. The base film may include, for example, a polymer. The polymer may be, for example, a thermoplastic polymer. The polymer may include, for example, polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), polybutylene terephthalate (PBT), polyimide (PI), or a combination thereof. Because the base film includes the thermoplastic polymer, the base film may melt in the event of a short circuit and suppress or reduce a rapid increase in the current. The base film may be, for example, an insulator (e.g., an electrical insulator). The metal layer may include, for example, copper (Cu), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), and/or an alloy thereof. The metal layer acts as an electrochemical fuse and may be cut in the event of an overcurrent to perform a short-circuit prevention function. The limit current and the maximum current may be adjusted by adjusting the thickness of the metal layer. The metal layer may be plated and/or deposited on the base film. If the thickness of the metal layer is reduced, the limit current and/or the maximum current of the electrode current collector 100 is reduced, so that the stability of the lithium battery in the event of a short circuit may be improved. A lead tab may be added on the metal layer for external connection. The lead tab may be welded to the metal layer or the metal layer/base film laminate by ultrasonic welding, laser welding, spot welding, and/or the like. During welding, the base film and/or metal layer may melt and the metal layer may be electrically connected to the lead tab. To make welding between the metal layer and the lead tab more robust, a metal chip may be added between the metal layer and the lead tab. The metal chip may be a chip of the same material as the metal of the metal layer The metal chip may be, for example, metal foil and/or metal mesh. The metal chip may be, for example, aluminum foil, copper foil, and/or SUS foil. By providing the metal chip on the metal layer and welding the same to the lead tab, the lead tab may be welded to the metal chip/metal layer laminate or the metal chip/metal layer/base film laminate. During welding, the metal layer or the metal layer/metal chip laminate may be electrically connected to the lead tab while the base film, the metal layer, and/or the metal chip are melted. A metal chip and/or a lead tab may be added onto a portion of the metal layer. The thickness of the base film may be, for example, about 1 μm to about 50 μm, about 1.5 μm to about 50 μm, about 1.5 μm to about 40 μm, or about 1 μm to about 30 μm. Because the base film may have a thickness in the above ranges, the weight of the electrode assembly may be more effectively reduced. The melting point of the base film may be, for example, about 100° C. to about 300° C., about 100° C. to about 250° C., or about 100° C. to about 200° C. Because the base film may have a melting point in the above ranges, the base film may be melted and easily coupled to the lead tab in the process of welding the lead tab. Surface treatment such as corona treatment may be performed on the base film in order to improve adhesion between the base film and the metal layer. The thickness of the metal layer may be, for example, about 0.01 μm to about 3 μm, about 0.1 μm to about 3 μm, about 0.1 μm to about 2 μm, or about 0.1 μm to about 1 μm. Because the metal layer may have a thickness in the above ranges, stability of the electrode assembly may be ensured while conductivity (e.g., electrical conductivity) is maintained. The thickness of the metal chip may be, for example, about 2 μm to about 10 μm, about 2 μm to about 7 μm, or about 4 μm to about 6 μm. Because the metal chip may have a thickness in the above ranges, connection between the metal layer and the lead tab may be more easily performed. Because the electrode current collector 100 may have a structure as described above, it is possible to reduce the weight of the electrode and consequently improve the energy density. The electrode current collector 100 may be, for example, a positive electrode current collector. The electrode current collector 100 may be, for example, a negative electrode current collector.
Referring to
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The first laminate 250 may be manufactured by, for example, the following method.
The process of providing one or more interlayers 200a, 200b, and 200 on one side or two opposing sides of the electrode current collector 100 to prepare the first laminate 250 includes, for example, providing the electrode current collector 100, and providing the interlayers 200a, 200b, and 200 on one side or two opposing sides of the electrode current collector 100. Materials of the electrode current collector 100 refer to the electrode current collector 100 section described above. The positive electrode current collector may be, for example, aluminum foil. The negative electrode current collector may be, for example, copper foil. The process of providing one or more interlayers 200a, 200b, and 200 on one side or two opposing sides of the electrode current collector 100 is to provide the interlayers 200a, 200b, and 200 on one side or two opposing sides of the electrode current collector 100 in a dry or wet manner. Dry coating, for example, coats a carbon-based conductive material (e.g., a carbon-based electrically conductive material) and/or a precursor thereof on one side or two opposing sides of the electrode current collector 100 by deposition and/or the like. Deposition is performed at a temperature of room temperature to a high temperature and at a pressure of atmospheric pressure to vacuum. The interlayers 200a, 200b, and 200 provided by the dry coating may not include a binder if the interlayers 200a, 200b, and 200 are made of a carbon-based conductive material (e.g., a carbon-based electrically conductive material). Wet coating, for example, coats a carbon-based conductive material (e.g., a carbon-based electrically conductive material) and a composition including a binder on one side or two opposing sides of the electrode current collector 100. The composition includes, for example, a carbon-based conductive material (e.g., a carbon-based electrically conductive material), a binder, and a processing solvent. The carbon-based conductive material and the binder refer to the electrode section described above. The processing solvent may be selected from solvents used for preparing an electrode slurry. The processing solvent is removed by drying after the composition is coated on the electrode current collector 100. A coating method is not limited to spin coating, dip coating, and the like, and may be any suitable coating method used in the art.
For example, a method for providing the outer peripheral region 220 in the interlayer 200 is not limited, and may be applied without limitation as long as it is possible to form the thickness of the outer peripheral region 220 to be greater than the thickness of the inter-region 210. For example, the interlayer 200 may be formed by coating one type (or kind) of interlayer-providing composition on the electrode current collector 100. In this embodiment, in order to form the outer peripheral region 220, a relatively excessive amount of the interlayer-providing composition may be applied along the outer periphery 260 of the interlayer to form the outer peripheral region 220.
For example, the interlayer 200 may be formed by using two types (or kinds) of interlayer-providing compositions. In this embodiment, a first interlayer-providing composition may be applied along the outer periphery 260 to form the outer peripheral region 220, and then a second interlayer-providing composition may be applied on the remaining region excluding the portion in which the outer peripheral region was formed to form the inter-region 210.
Referring to
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For example, because the outer peripheral region 220 of the interlayer 200 is provided along the outer periphery 260 of the interlayer 200, the cut lines 600a, 600b, and 600 may be formed on at least a portion of the boundary between the first region A1 and the second region A2 in the process of providing and roll-pressing the dry electrode films 300a, 300b, and 300 on the first laminate 250. In dry electrode films 300a, 300b, and 300, the cut lines 600a, 600b, and 600 may be provided, for example, along at least a portion of the outer periphery of the interlayers 200a, 200b, and 200. Because the cut lines 600a, 600b, and 600 may be provided along at least a portion of the outer periphery of the interlayers 200a, 200b, and 200, a process of introducing the cut lines 600a, 600b, and 600 into the dry electrode films 300a, 300b, and 300 may be simplified. As a result, a process of manufacturing a dry electrode 500 may be simplified. For example, because the cut lines 600a, 600b, and 600 are provided along a portion of the outer periphery of the interlayers 200a, 200b, and 200, the dry electrode films 300a, 300b, and 300 may be easily prepared in a simple process. For example, the cut lines 600a, 600b, and 600 may be provided along the entirety of the outer periphery of the interlayers 200a, 200b, and 200. Because the cut lines 600a, 600b, and 600 may be provided along the entirety of the outer periphery of the interlayers 200a, 200b, and 200, the second region A2 can be more effectively separated from the first region A1. For example, the cut lines 600a, 600b, and 600 may be provided along the entirety of the outer periphery of the interlayers 200a, 200b, and 200, the dry electrode films 300a, 300b, and 300 having various suitable types (or kinds) of patterns may be easily prepared.
The length of perforations of the cut lines 600a, 600b, 600 may be about 40% or less, about 35% or less, or about 30% or less of the total length of the boundary between the first region A1 and the second region A2, for example. The length of the cut lines 600a, 600b, and 600 may be, for example, about 40% or less, about 35% or less, or about 30% or less of the total length of the outer periphery of the interlayers 200a, 200b, and 200. The length of the cut lines 600a, 600b, and 600 may be, for example, about 40% or less, about 35% or less, or about 30% or less of the total length of the dry electrode films 300a, 300b, and 300 in a machine direction. The length of the cut lines 600a, 600b, and 600 may be, for example, about 40% or less, about 35% or less, or about 30% or less of the total length of the dry electrode films 300a, 300b, and 300 in a transverse direction. For example, if the dry electrode films 300a, 300b, and 300 include the cut lines 600a, 600b, and 600, a portion of the second region A2 is pulled along the cut lines 600a, 600b, and 600 and separated from the first region A1, so that the manufacture of the dry electrode 500 may be more easily performed.
Referring to
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The machine direction is a direction in which the dry electrode films 300a, 300b, and 300 are stretched during the manufacturing of the dry electrode films 300a, 300b, and 300. Referring to
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Because the second region A2 is separated from the first region A1 along the outer periphery of the interlayers 200a, 200b, and 200, the dry electrode films 300a, 300b, and 300 may be selectively on the interlayers 200a, 200b, and 200. Depending on the position and/or shape of the interlayers 200a, 200b, and 200, the position and/or shape of the dry electrode films 300a, 300b, and 300 on the interlayers 200a, 200b, and 200 may be selected.
For example, on the interlayers 200a, 200b, and 200 having a rectangular shape, the dry electrode films 300a, 300b, and 300 having the same shape as the shape of the interlayers 200a, 200b, and 200 and having a larger area than the area of the same are provided, and the dry electrode films 300a, 300b, and 300 include the first region A1 of the same shape and area as those of the interlayers 200a, 200b, and 200 and the second region A2 extending from the first region A1 beyond the outer periphery 260 of the interlayers 200a, 200b, and 200 and provided around the first region A1. The second region A2 of the dry electrode films 300a, 300b, and 300 is pulled, so that the second region A2 is selectively separated from the first region A1 along the outer periphery of the interlayers 200a, 200b, and 200, and the dry electrode films 300a, 300b, and 300 having the same shape and area as those of the interlayers 200a, 200b, and 200 are on the interlayers 200a, 200b, and 200.
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In the dry electrode 500 manufactured by the method for manufacturing the dry electrode 500 according to embodiments, if measuring the surface and interfacial measuring analysis system (SAICAS), the dry electrode films 300a, 300b, 300 have a rate of change in vertical relative binding force FVR of about 300% or less, about 250% or less, about 200% or less, about 150% or less, or about 140% or less, according to a depth from a first point spaced apart by about 5% from the surface of the dry electrode films 300a, 300b, and 300 in the direction of the electrode current collector 100 to a second point spaced apart by about 5% from the surface of the electrode current collector 100 with respect to the total thickness of the dry electrode films 300a, 300b, and 300.
The rate of change in vertical relative binding force is calculated from Equation 1 below. An embodiment of a method for measuring the SAICAS is demonstrated with respect to, for example, Evaluation Example 1.
In the dry electrode 500, if measuring the surface and interfacial measuring analysis system (SAICAS), the rate of change in vertical relative binding force of the dry electrode films 300a, 300b, and 300 is about 300% or less, so that the uniformity of distribution of components of the dry electrode films 300a, 300b, and 300 in the dry electrode 500 is improved. Because side reactions and an increase in internal resistance caused by non-uniform distribution of components in the dry electrode films 300a, 300b, and 300 are suppressed or reduced, the reversibility of an electrode reaction may be improved. Therefore, even in a dry electrode 500 having a high loading, cycle properties of a lithium battery are improved. The rate of change in vertical relative binding force of the dry electrode films 300A, 300B, and 300 may be, for example, about 10% to about 300%, about 20% to about 250%, about 30% to about 200%, about 40% to about 160%, about 50% to about 150%, or about 60% to about 140%.
In the dry electrode 500 manufactured by the method for manufacturing the dry electrode 500 according to embodiments, if measuring the surface and interfacial measuring analysis system (SAICAS), the dry electrode films 300a, 300b, 300 may have a horizontal binding force ratio of about 50% or greater of a second horizontal binding force FHA2 at a second point spaced apart by about 10% from the surface of the electrode current collector 100 to a first horizontal binding force FHA1 at a first point spaced apart by about 10% in the direction of the electrode current collector 100 from the surface of the dry electrode films 300a, 300b, and 300 with respect to the total thickness of the dry electrode films 300a, 300b, and 300.
The horizontal binding force ratio is represented by, for example, Equation 2 below.
In an electrode, if measuring the SAICAS, the horizontal binding force ratio may be about 50% or greater, thereby further improving the uniformity of distribution of components in the electrode. Because the electrode may have a horizontal binding force ratio in the above range, cycle properties of a lithium battery employing the electrode may be further improved. The horizontal binding force ratio may be, for example, about 50% to about 300%, about 50% to about 250%, about 50% to about 200%, about 50% to about 150%, or about 50% to about 100%.
The dry electrode films 300a, 300b, and 300 may be prepared by, for example, the following method.
First, a dry electrode active material, a dry conductive material (e.g., a dry electrically conductive material), and a dry binder are mixed together in a dry manner to prepare a mixture.
The dry mixing means mixing in a state in which a processing solvent is not included. The processing solvent may be, for example, a solvent used in the preparation of an electrode slurry. The processing solvent may be, for example, water, NMP, and/or the like, but is not limited thereto, and is not limited as long as it is a processing solvent used in the preparation of an electrode slurry. The dry mixing may be performed by using a stirrer at a temperature of about 25° C. to about 65° C. at a rotational speed of about 10 rpm to about 10000 rpm, or about 100 rpm to about 10000 rpm. The dry mixing may be performed by using a stirrer for about 1 minute to about 200 minutes, or about 1 minute to about 150 minutes.
The dry mixing may be performed, for example, more than one time. First, the dry electrode active material, the dry conductive material, and the dry binder may be subjected to primary dry mixing to prepare a first mixture. The primary dry mixing may be performed, for example, at a temperature of about 25° C. to about 65° C. at a rotational speed of about 2000 rpm or lower for about 15 minutes or less. The primary dry mixing may be performed, for example, at a temperature of about 25° C. to about 65° C. at a rotational speed of about 500 rpm to about 2000 rpm for about 5 minutes to about 15 minutes. The dry electrode active material, the dry conductive material, and the dry binder may be uniformly (e.g., substantially uniformly) mixed together by the primary dry mixing. Subsequently, the dry electrode active material, the dry conductive material, and the dry binder may be subjected to secondary dry mixing to prepare a second mixture. The secondary dry mixing may be performed, for example, at a temperature of about 25° C. to about 65° C. at a rotational speed of about 3000 rpm or higher for about 10 minutes or more. The secondary dry mixing may be performed, for example, at a temperature of about 25° C. to about 65° C. at a rotational speed of about 3000 rpm to about 9000 rpm for about 10 minutes to about 60 minutes. A dry mixture including a fibrillated dry binder may be obtained by the secondary dry mixing.
The stirrer may be, for example, a kneader. The stirrer includes, for example, a chamber, one or more rotation axes provided and rotating inside the chamber, and a blade rotatably coupled to the rotation axis and provided in a longitudinal direction of the rotation axis. The blade may be, for example, one or more selected from a ribbon blade, a sigma blade, a jet (Z) blade, a dispersion blade, and a screw blade. Because the blade is included, a mixture in a dough-like form may be prepared by effectively mixing together the electrode active material, the dry conductive material, and the dry binder without a solvent (e.g., without a processing solvent). The prepared mixture may be introduced into an extrusion device and extruded in the form of a sheet. The pressure at the time of the extrusion may be, for example, about 4 mPa to about 100 Mpa, or about 10 Mpa to about 90 Mpa. The obtained mixture may be in the form of a film. In some embodiments, the obtained mixture may be the dry electrode films 300a, 300b, and 300.
The dry conductive material may be, but is not limited to, carbon black, graphite fine particles, natural graphite, artificial graphite, acetylene black, Ketjen black, carbon fiber, carbon nanotubes, metal powder, metal fiber, and/or metal tubes of metals such as copper, nickel, aluminum, silver, and/or the like, a conductive polymer such as a polyphenylene derivative, and/or the like, and may be any suitable conductive material (e.g., electrically conductive material) used in the art. The conductive material may be, for example, a carbon-based conductive material (e.g., a carbon-based electrically conductive material).
The dry binder may be, but is not necessarily limited to, a vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), a mixture of the aforementioned polymers, a styrene-butadiene rubber-based polymer, and/or the like, and the solvent may be, but is not necessarily limited to, N-methylpyrrolidone (NMP), acetone, water, and/or the like, and any suitable dry binder and any suitable solvent used in the art may be used.
It is also possible to add a plasticizer and/or pore providing agent to the composition of an electrode active material to form pores inside an electrode plate.
The contents of the electrode active material, the dry conductive material, and the dry binder used in the electrode active material layer may be at any suitable levels generally used in a lithium battery.
A positive electrode uses a positive electrode active material as the electrode active material. The positive electrode active material refers to the electrode section described above. A negative electrode uses a negative electrode active material as the electrode active material. The negative electrode active material refers to the electrode section described above.
According to another embodiment, a lithium battery 1 (
The lithium battery 1 is, for example, a lithium ion battery, a lithium solid battery, a lithium air battery, or the like.
The lithium battery 1 is manufactured by, for example, the following example method, but is not necessarily limited to such a method and the method may be adjusted according to desired or required conditions.
First, according to the above-described method for manufacturing the dry electrode 500, one or both of the positive electrode and the negative electrode may be manufactured. For example, if one electrode of the positive electrode and the negative electrode is manufactured by the above-described method for manufacturing an electrode, the other electrode may be manufactured by a manufacturing method utilizing a wet manner. For example, the other electrode may be manufactured by preparing an electrode slurry including an electrode active material, a conductive material (e.g., an electrically conductive material), a binder, and a solvent, and coating and drying the prepared electrode slurry on the electrode current collector 100. A conductive material (e.g., an electrically conductive material) and a binder included in an electrode manufactured in a wet manner may be selected from the conductive material and the binder used in the manufacture of the dry electrode 500 described above.
A separator to be inserted between the positive electrode and the negative electrode is prepared.
The separator may be any suitable separator generally used in a lithium battery. As the separator, for example, a separator that has low resistance to ion movement of an electrolyte and excellent electrolyte solution moisture retention ability may be used. The separator may be selected from, for example, glass fiber, polyester, Teflon, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or a combination thereof, and may be in the form of a non-woven or woven fabric. A windable separator such as polyethylene, polypropylene, and/or the like may be used in a lithium ion battery, and a separator having excellent organic electrolyte solution impregnation ability may be used in a lithium ion polymer battery.
The separator may be manufactured by the following example method, but is not necessarily limited to such a method and the method may be adjusted according to desired or required conditions.
First, a separator composition is prepared by mixing together a polymer resin, a filler, and a solvent. The separator composition is directly coated and dried in an upper portion of an electrode to form a separator. For example, the separator composition is cast and dried on a support, and then a separator film peeled off from the support is stacked in the upper portion of the electrode to form a separator.
A polymer used in the preparation of the separator is not limited, and any suitable polymer used in a binder of an electrode plate may be used. For example, a vinylidene fluoride/hexafluoropropylene copolymer, polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, or a mixture thereof may be used.
The electrolyte is prepared.
The electrolyte may be, for example, an organic electrolyte solution. The organic electrolyte solution may be prepared by dissolving a lithium salt in an organic solvent.
The organic solvent may be any suitable organic solvent used in the art. The organic solvent may be, for example, propylene carbonate, ethylene carbonate, fluoroethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, methylpropyl carbonate, ethylpropyl carbonate, methylisopropyl carbonate, dipropyl carbonate, dibutyl carbonate, benzonitrile, acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyrolactone, dioxolane, 4-methyldioxolane, N, N-dimethylformamide, dimethylacetamide, dimethylsulfoxide, dioxane, 1,2-dimethoxyethane, sulfolane, dichloroethane, chlorobenzene, nitrobenzene, diethylene glycol, dimethylether, a mixture thereof, and/or the like.
The lithium salt may be any suitable lithium salt used in the art. The lithium salt may be, for example, LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiCF3SO3, Li(CF3SO2)2N, LiC4F9SO3, LiAlO2, LiAlCl4, LiN(CxF2x+1SO2)(CyF2y+1SO2)(where x, y are natural numbers), LiCl, LiI, a mixtures thereof, and/or the like.
For example, the electrolyte may be a solid electrolyte. The solid electrolyte may be, for example, boron oxide, lithium oxynitride, and/or the like, but is not limited thereto, and may be any suitable solid electrolyte used in the art. The solid electrolyte may be formed on the negative electrode by, for example, sputtering and/or the like, and/or a separate solid electrolyte sheet is stacked on the negative electrode. The solid electrolyte may be, for example, an oxide-based solid electrolyte and/or a sulfide-based solid electrolyte.
Referring to
Referring to
Referring to
A pouch-type lithium battery corresponds to that using a pouch as a battery case in the lithium batteries of
Lithium batteries have excellent lifespan properties and high-rate properties, and thus, are used, for example, in electric vehicles (Evs). Lithium batteries have excellent lifespan characteristics and high rate characteristics. Due to these characteristics, lithium batteries are used, for example, in electric vehicles (Evs). For example, the lithium batteries are used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). The lithium batteries are used in fields that utilize or require large amounts of power storage. For example, lithium batteries are used in electric bicycles, power tools, and the like.
A plurality of lithium batteries may be stacked to form a battery module, and a plurality of battery modules may form a battery pack. Such a battery pack may be used in any suitable device that utilizes or requires high capacity and high output. For example, the battery pack may be used in laptops, smartphones, electric vehicles, and the like. The battery module may include, for example, a plurality of batteries and a frame that hold the same. The battery pack may include, for example, a plurality of battery modules and a bus bar for connecting the same. The battery module and/or the battery pack may further include a cooling device. A plurality of battery packs may be controlled by a battery management system. The battery management system may include a battery pack and a battery control device connected to the battery pack.
The present disclosure is described in more detail with reference to the following examples and comparative examples. However, the examples are merely illustrative of embodiments of the present disclosure, and the scope of the present disclosure is not limited thereto.
LiNi0.91Co0.05Al0.04O2 (hereinafter, referred to as NCA91) having an average particle diameter (D50) of about 15 μm as a dry positive electrode active material, a carbon conductive material (Denka Black) as a dry conductive material, and polytetrafluoroethylene (PTFE) as a dry binder were introduced into a blade mixer at a weight ratio of 96:1.8:2.2, and then subjected to primary dry mixing at 25° C. at a rate of 1000 rpm for 10 minutes to prepare a first mixture in which the positive electrode active material, the conductive material, and the binder were uniformly mixed together.
Subsequently, to allow fibrillization of the dry binder to proceed, the first mixture was further mixed at 25° C. at a rate of 5000 rpm for 20 minutes to prepare a second mixture. No solvent was used in the preparation of the first mixture and the second mixture. The prepared second mixture was introduced into an extruder and extruded to prepare a positive electrode active material layer in a sheet shape. The pressure at the time of the extrusion pressure was about 50 MPa. The extrusion direction corresponds to a machine direction.
The prepared positive electrode active material layer sheet was roll-pressed to prepare a dry positive electrode film. The dry positive electrode film was a self-standing film. The pressure at the time of the roll-pressing was about 3 ton/cm2.
On one side of a 12 μm-thick aluminum thin-film positive electrode current collector, a first laminate including a carbon layer was prepared as an interlayer.
The length of the carbon layer was equal to the length of the positive electrode current collector in the machine direction. The width of the carbon layer was about 90% of the width of the positive electrode current collector in a transverse direction. The carbon layer was provided in the center of the positive electrode current collector by being spaced apart by about 5% from each of both ends of the positive electrode current collector in the transverse direction.
The carbon layer had the same length as the length of the positive electrode current collector in the machine direction, and further included an outer peripheral region provided in a region up to 5% from each of both ends of the carbon layer, wherein the ratio of the thickness of the outer peripheral region to the thickness of a central region excluding the outer peripheral region was about 2.
The carbon layer was prepared by coating and then drying a composition including a carbon conductive material (Denka Black) and polyvinylidene fluoride (PVDF) on an aluminum thin film. The thickness of the carbon layer on one side of the aluminum thin film was about 1 μm.
A dry positive electrode film was on one side on which the carbon layer of the first laminate was provided to prepare a second laminate. The thickness of the dry positive electrode film was about 100 μm.
The area of the dry positive electrode film was the same as that of the positive electrode current collector. The dry positive electrode film included a first region on the carbon layer and a second region on the positive electrode current collector. The second region was provided extending from the first region beyond the outer periphery of the carbon layer.
The second region of the dry positive electrode film was bent by 180 degrees at one end in a longitudinal direction of the dry positive electrode film, and then pulled in the longitudinal direction along a cut line of the dry positive electrode film.
The second region was separated from the first region of the dry positive electrode film from one end to the other end in the longitudinal direction of the dry positive electrode film to completely remove the second region of the dry positive electrode film on the positive electrode current collector. A dry positive electrode active material layer was provided only on the carbon layer, and a dry positive electrode free of the dry positive electrode active material layer was prepared on the positive electrode current collector.
In the process of removing the second region of the dry positive electrode film, no damage was done to the positive electrode current collector. The dry positive electrode active material layer was free of a burr or a recessed portion provided adjacent to the outer periphery thereof.
A scanning electron microscope image of a cut surface of the dry positive electrode active material layer after removing the second region of the dry positive electrode film is shown in
A coin cell was manufactured by using the positive electrode prepared above, lithium metal as a counter electrode, a PTFE separator, and a solution in which 1.3 M LiPF6 was dissolved in ethylene carbonate (EC)+ethylmethyl carbonate (EMC)+dimethyl carbonate (DMC) (3:4:3 volume ratio) as an electrolyte.
A dry positive electrode and a lithium battery were manufactured in substantially the same manner as in Example 1, except that the ratio of the thickness of the outer peripheral region to the thickness of the inter-region of the interlayer was changed to 1.5.
A dry positive electrode and a lithium battery were manufactured in substantially the same manner as in Example 1, except that the ratio of the thickness of the outer peripheral region to the thickness of the inter-region of the interlayer was changed to 1.2.
A dry positive electrode and a lithium battery were manufactured in substantially the same manner as in Example 1, except that the ratio of the thickness of the outer peripheral region to the thickness of the inter-region of the interlayer was changed to 2.5.
A dry positive electrode film was prepared in substantially the same manner as in Example 1.
A first laminate was prepared in substantially the same manner as in Example 1, except that an interlayer including an inter-region and an outer peripheral region was formed on both sides of a 12 μm-thick aluminum thin-film positive electrode current collector.
A dry positive electrode film was on both sides of the first laminate to prepare a second laminate.
The machine-direction length of the dry positive electrode film was the same as the machine-direction length of the first laminate. The transverse-direction length of the dry positive electrode film was about 120% of the transverse-direction length of the first laminate. The two dry positive electrode films were in direct contact with each other in a region beyond both ends of the first laminate in the transverse direction. The dry positive electrode film included a first region on the interlayer and a second region extending from the first region beyond the outer periphery of the interlayer. The first region of the dry positive electrode film is in contact with the interlayer, and the second region of the dry positive electrode film is not in contact with the interlayer. The thickness of the dry positive electrode film on one side of the positive electrode current collector was about 100 μm.
In this embodiment, by means of the outer peripheral region, a cut line was formed on the dry positive electrode film along the boundary between the first region and the second region on the side surface of one end in the longitudinal direction of the dry positive electrode film.
The second region of the dry positive electrode film was bent by 180 degrees at one end in a longitudinal direction of the dry positive electrode film, and then pulled in the longitudinal direction along a cut line of the dry positive electrode film.
The second region was separated from the first region of the dry positive electrode film from one end to the other end in the longitudinal direction of the dry positive electrode film to completely remove the second region of the dry positive electrode film. A dry positive electrode in which a dry positive electrode active material layer was provided only on the first laminate was prepared.
In the process of removing the second region of the dry positive electrode film, no damage was done to the positive electrode current collector. The dry positive electrode active material layer was free of a burr or a recessed portion provided adjacent to the outer periphery thereof.
A coin cell was manufactured by using the positive electrode prepared above, lithium metal as a counter electrode, a PTFE separator, and a solution in which 1.3 M LiPF6 was dissolved in ethylene carbonate (EC)+ethylmethyl carbonate (EMC)+dimethyl carbonate (DMC) (3:4:3 volume ratio) as an electrolyte.
A mixture in which LiNi0.91Co0.05Al0.04O2 (hereinafter referred to as NCA91) with an average particle diameter (D50) of about 0.91 μm as a positive electrode active material, a carbon conductive material (Denka Black) as a conductive material, and polytetrafluoroethylene (PTFE) as a binder were mixed together at a weight ratio of 96:1.8:2.2 and mixed together with N-methylpyrrolidone (NMP) in an agate mortar to prepare a slurry for providing a positive electrode active material layer. The slurry was bar coated on one side of an aluminum-foil positive electrode current collector to a thickness of about 12 μm, dried at room temperature, and then dried once again under the conditions of vacuum and 120° C. to prepare a positive electrode active material layer, thereby preparing a laminate. The prepared laminate was roll-pressed to prepare a positive electrode. The pressure at the time of the roll-pressing was about 3.0 ton/cm2. The thickness of the positive electrode active material layer of the positive electrode of Comparative Example 1 was the same as the thickness of the positive electrode active material layer of the positive electrode of Example 1.
On a side surface of one end in a longitudinal direction of the wet positive electrode, a cut line was introduced onto a wet positive electrode active material layer in the same position and form as those of the dry positive electrode. Based on the cut line, a central portion in a transverse direction of the wet positive electrode was defined as a first region, and an end portion in the transverse direction of the wet positive electrode was defined as a second region. The second region of the wet positive electrode active material layer was bent by 180 degrees at one end in the longitudinal direction of the wet positive electrode, and then pulled along the longitudinal direction of the wet positive electrode.
Because the positive electrode active material layer prepared in a wet manner was hard, the positive electrode active material layer cracked in the process of separating the second region, and thus, was not be able to be applied as a positive electrode.
Therefore, in order to perform a charge/discharge experiment, the second region was separated from the first region of the positive electrode active material layer using a laser cutter to prepare a positive electrode.
A lithium battery was manufactured in substantially the same manner as Example 1, except that the above wet positive electrode was used instead of the dry positive electrode.
A positive electrode was manufactured in substantially the same manner as in Example 1, except that a carbon layer having a uniform thickness was formed on an aluminum thin film having a thickness of about 12 μm to prepare a first electrode body.
On a side surface of one end in a longitudinal direction of the dry positive electrode, a cut line was introduced onto a dry positive electrode active material layer in the same position and form as those of the dry positive electrode of Example 1. Based on the cut line, a central portion in a transverse direction of the dry positive electrode was defined as a first region, and an end portion in the transverse direction of the dry positive electrode was defined as a second region. The second region of the dry positive electrode active material layer was bent by 180 degrees at one end in the longitudinal direction of the dry positive electrode, and then pulled along the longitudinal direction of the dry positive electrode to remove the second region.
In this embodiment, because an additional procedure was performed to introduce the cut line, the number of dry electrodes to be manufactured per unit time was reduced compared to Example 1.
A positive electrode was manufactured in substantially the same manner as in Example 1, except that a carbon layer having a uniform thickness was formed on an aluminum thin film having a thickness of about 12 μm to prepare a first electrode body.
Thereafter, a central portion in a transverse direction of the dry positive electrode was defined as a first region, and an end portion in the transverse direction of the dry positive electrode was defined as a second region. The second region of the dry positive electrode active material layer was bent by 180 degrees at one end in the longitudinal direction of the dry positive electrode, and then pulled along the longitudinal direction of the dry positive electrode to remove the second region.
In this case, the number of dry electrodes to be manufactured per unit time was similar to that of Example 1, but because there was no cut line, the first region was partially cracked in the process of removing the second region.
A dry electrode film and a positive electrode current collector/interlayer laminate were prepared in substantially the same manner as in Example 1.
A dry positive electrode was manufactured in substantially the same manner as in Example 1, except that the second region was separated from the first region of the positive electrode active material layer using a laser cutter along the boundary between the first region and the second region on the side surface of one end in the longitudinal direction of the dry positive electrode. In the process of removing the second region of the positive electrode active material layer, the positive electrode current collector was damaged by the laser. A burr and/or a recessed portion located adjacent to the outer periphery of the dry positive electrode active material layer was formed.
A dry electrode film and a positive electrode current collector/interlayer laminate were prepared in substantially the same manner as in Example 5.
A dry positive electrode was manufactured in substantially the same manner as in Example 5, except that the second region was separated from the first region of the positive electrode active material layer using a laser cutter along the boundary between the first region and the second region on the side surface of one end in the longitudinal direction of the dry positive electrode. In the process of removing the second region of the positive electrode active material layer, the positive electrode current collector was damaged by the laser. A burr and/or a recessed portion located adjacent to the outer periphery of the dry positive electrode active material layer was formed.
Lithium batteries manufactured in Examples 1 to 4, Comparative Example 1, and Comparative Example 3 were charged with a constant current at about 25° C. with a current of about 0.1 C rate until the voltage reached about 4.4 V (vs. Li), and then cut off at a current of about 0.05 C rate while maintaining about 4.4 V in a constant voltage mode. Subsequently, the lithium batteries were discharged with a constant current of 0.1 C rate until the voltage reached about 2.8 V (vs. Li) during the discharge (formation cycle).
The lithium batteries that had undergone the formation cycle were charged at about 25° C. with a current of about 0.5 C rate until the voltage reached about 4.4 V (vs. Li). Subsequently, the lithium batteries were discharged with a constant current of 0.5 C rate until the voltage reached about 2.8 V (vs. Li) during the discharge, and such a cycle was repeated under the same conditions until the 100th cycle (100 repetitions).
In all charge/discharge cycles, a 10-minute stop time was provided after every charge/discharge cycle. A part of the room-temperature cycling test results is shown in Table 1 below. The capacity retention rate at the 100th cycle is defined by Equation 3 below.
As shown in Table 1, the lithium batteries of Examples 1 to 4 have improved room-temperature lifespan properties compared to the lithium battery of Comparative Example 1.
The lithium battery including the wet electrode of Comparative Example 1 had poor lifespan properties compared to the lithium batteries including the dry electrodes of Examples 1 to 4.
The wet electrode of Comparative Example 1 was determined to have reduced lifespan properties due to an increase in side reactions caused by the burr and/or the recessed portion of the electrode current collector formed adjacent to the outer periphery of the phosphorus active material layer by the laser cutting.
Because the dry electrode of Comparative Example 3 did not include an outer periphery region, the second region was removed in the absence of a cut line, and during the process, the first region was partially cracked, which was determined to have caused degradation in lifespan properties.
According to one aspect of embodiments, by selectively removing a dry electrode film by using the difference in the thickness of interlayers, it is possible to provide various suitable types (or kinds) of electrode active material layers without damaging an electrode current collector during a dry electrode manufacturing process.
According to another aspect of embodiments, by providing an interlayer between an electrode current collector and a dry electrode film, it is possible to easily adjust the position and shape of the dry electrode film introduced onto the electrode current collector.
It should be understood that embodiments described herein should be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features or aspects within each embodiment should typically be considered as available for other similar features or aspects in other embodiments. While one or more embodiments have been described with reference to the figures, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present disclosure as defined by the following claims, and equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2023-0039376 | Mar 2023 | KR | national |
| 10-2023-0122041 | Sep 2023 | KR | national |
