Patent Application
20230395778
This application relates to the field of batteries, and more specifically, to a positive electrode plate for lithium-ion battery, and further relates to a battery, a battery module, a battery pack, and an electric apparatus containing the same.
With the development of the related fields in recent years, rechargeable batteries (also known as secondary batteries) are increasingly used in fields such as consumer goods, new energy vehicles, large-scale energy storage, aerospace, ships and heavy machinery, even serving as the main power and energy supply equipment in these fields. In various available secondary batteries, lithium-ion secondary batteries have received widespread attention due to their excellent performance. However, lithium-ion secondary batteries also have some technical problems that have not been resolved so far. For example, how pre-lithiation technology for lithium-ion battery is improved is one of the great concerns. Generally, the existing pre-lithiation technology for lithium-ion battery is simply applying an additional pre-lithiation layer containing pre-lithiation agents is to the positive electrode active material layer. However, these pre-lithiation agents have strong alkalinity and large particle size, while the pre-lithiation layer is usually required to be thin. In this case, it is difficult to form a uniform pre-lithiation layer, and the non-uniformity of the pre-lithiation layer significantly increases the risk of lithium precipitation and local swelling force of the battery cell during charging and discharging, leading to undesirable service life and power of the battery and significantly increased probability of battery failure. In addition, during battery charging and discharging, electronic isolation oxide is formed after the pre-lithiation agent releases lithium, affecting conductivity of the positive electrode plate and causing performance of the lithium-ion battery to drop. In addition, it is well known in the art that the use of a positive electrode active material having a small particle size and a large BET specific surface area often leads to higher content of entrained impurities and more side reactions, significantly shortening the effective service life of lithium-ion batteries. However, the use of a positive electrode active material having a large particle size and a small BET specific surface area leads to reduced power of batteries. So far, such contradiction has not been well resolved.
Therefore, an improved technical solution is urgently needed in the art to effectively overcome the above problems in an economical and simple manner, achieve excellent pre-lithiation effect, significantly reduce or even eliminate the impact on the performance of batteries caused by a product resulting from the pre-lithiation agents releasing lithium, significantly reduce the risk of crystallization or swelling of batteries, and improve the power efficiency and cycling performance of batteries.
Through a lot of in-depth researches, the inventors of this application have unexpectedly designed a unique technical solution to resolve the foregoing technical problems that urgently need to be resolved in the prior art by specially designing a specific composition of multiple layers in positive electrode plates.
A first aspect of this application provides a positive electrode plate for lithium-ion battery, where the positive electrode plate includes: i) a current collector; ii) at least one capacity layer, where the capacity layer includes a first binder, a first conductive agent, and a first positive electrode active material, the first positive electrode active material having a first median particle size; and ii) at least one power layer, where the power layer includes a second binder, a second conductive agent, a pre-lithiation agent, and a second positive electrode active material, the second positive electrode active material having a second median particle size; where the first median particle size is greater than the second median particle size. In this application, the capacity layer containing the first positive electrode active material and the power layer containing both the pre-lithiation agent and the second positive electrode active material are used, and the median particle sizes of the positive electrode active materials in the two layers are controlled, guaranteeing uniformity of the power layer in a simple and economical manner, and effectively inhibiting the adverse impact on the performance of the battery caused by an electronic isolation oxide generated after the pre-lithiation agent releases lithium. In this way, the risk of crystallization or swelling of batteries is significantly reduced, and power efficiency and cycling performance of batteries are improved.
According to an embodiment of the first aspect of this application, the positive electrode plate includes at least one capacity layer located on at least one surface of the current collector, and at least one power layer located on a surface of the at least one capacity layer facing away from the current collector. To be specific, the capacity layer is on the bottom (inside), and the power layer is on the top (outside). According to another embodiment of the first aspect of this application, the positive electrode plate includes at least one power layer located on at least one surface of the current collector, and at least one capacity layer located on a surface of the at least one power layer facing away from the current collector. To be specific, the capacity layer is on the top (outside), and the power layer is on the bottom (inside). Any one of the foregoing design structures is selected according to the desired use and operating environment of the lithium-ion battery, allowing the lithium-ion battery to better meet the performance requirement.
According to an embodiment of the first aspect of this application, the first median particle size of the first positive electrode active material is 0.8-1.3 μm. According to another embodiment of the first aspect of this application, the second median particle size of the second positive electrode active material is 0.1-0.7 μm, and preferably 0.2-0.45 μm. The particle sizes of the positive electrode active materials in the capacity layer and power layer being specially designed can ensure the energy density of the positive electrode plate while reducing impact on the conductivity caused by a product resulting from a pre-lithiation agent releasing lithium.
According to another embodiment of the first aspect of this application, the first positive electrode active material and the second positive electrode active material are each independently selected from lithium cobaltate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadyl phosphate, lithium vanadate, lithium manganate, positive electrode active material shown in formula I, positive electrode active material shown in formula II, and a combination thereof:
LiNixCoyAzO2 formula I
in formula I, A is selected from one or more of the following elements: manganese, aluminum, copper, zinc, tin, titanium, magnesium, and iron, 0.01≤x≤0.98, 0.01≤y≤0.98, 0.01≤z≤0.98, and x+y+z=1;
LiFe1-m-nMnmBnPO4 formula II
According to another embodiment of the first aspect of this application, the pre-lithiation agent is selected from one or more of the following: Li2M1O2, Li2M2O3, Li2M3O4, Li3M4O4, Li5M5O4, Li5M6O6, Li6M7O4, and LiaCbOc. According to another embodiment of the first aspect of this application, the pre-lithiation agent is Li2M1O2, where M1 is selected from one or more of the following: Cu, Ni, Mn, Fe, Cr, Mo, Zn, Sn, Mg, and Ca. According to another embodiment of the first aspect of this application, the pre-lithiation agent is Li2M2O3, where M2 is selected from one or more of the following: Ni, Co, Fe, Mn, Sn, Cr, Mo, Zr, Si, Cu, and Ru. According to another embodiment of the first aspect of this application, the pre-lithiation agent is Li2M3O4, where M3 is selected from one or more of the following: Ni, Co, Fe, Mn, Sn, Cr, V, and Nb. According to another embodiment of the first aspect of this application, the pre-lithiation agent is Li3M4O4, where M4 is selected from one or more of the following: Cu, Ni, Mn, Fe, Cr, Mo, Zn, Sn, Mg, and Ca. According to another embodiment of the first aspect of this application, the pre-lithiation agent is Li5M5O4, where M5 is selected from one or more of the following: Ni, Co, Fe, Mn, Sn, Cr, and Mo. According to another embodiment of the first aspect of this application, the pre-lithiation agent is Li5M6O6, where M6 is selected from one or more of the following: Cu, Ni, Mn, Fe, Cr, Mo, Zn, Sn, Mg, and Ca. According to another embodiment of the first aspect of this application, the pre-lithiation agent is Li6M7O4, where M7 is selected from one or more of the following: Ni, Co, Mn, Fe, and Ru. According to another embodiment of the first aspect of this application, the pre-lithiation agent is LiaCbOc, where a is an integer 1 or 2, b is an integer 0, 1, 2, 3, or 4, and c is an integer 1, 2, 3, 4, 5, or 6. According to another embodiment of the first aspect of this application, the pre-lithiation agent includes Li2Cu0.5Ni0.5O2, Li5FeO4, and a combination thereof. All the foregoing pre-lithiation agents can be used in the technical solution of this application, so that manufacturing of batteries is highly flexible and appropriate pre-lithiation agent materials can be selected according to battery performance and cost requirements. In other words, the technical solution of this application has a wide application range.
According to another embodiment of the first aspect of this application, a median particle size of the pre-lithiation agent is 5-15 μm, for example, 6-10 μm. Adjustment of the median particle size of the pre-lithiation agent facilitates formation of a uniform and thin power layer, so as to improve the power and service life of batteries and further reduce the risk of lithium precipitation and swelling of battery cells.
According to another embodiment of the first aspect of this application, based on the total weight of the capacity layer, the capacity layer includes 1-30 wt % of the first binder, 0.1-10 wt % of the first conductive agent, and 60-98.5 wt % of the first positive electrode active material. According to another embodiment of the first aspect of this application, based on the total weight of the power layer, the power layer includes 1-30 wt % of the second binder, 0.1-10 wt % of the second conductive agent, 0.1-30 wt % of the pre-lithiation agent, and 50-97 wt % of the second positive electrode active material. According to another embodiment of the first aspect of this application, a percentage of the second conductive agent in the power layer is equal to or greater than a percentage of the first conductive agent in the capacity layer. According to another embodiment of the first aspect of this application, a weight ratio of the power layer and the capacity layer is 1:9 to 9:1. Selection of the foregoing preferred ratio further improves pre-lithiation effect. To be specific, lithium batteries have high first-cycle coulombic efficiency, optimized energy density, and excellent cycle life.
A second aspect of this application provides a lithium-ion battery, where the lithium-ion battery includes a negative electrode plate, an electrolyte, a separator, and the positive electrode plate for lithium-ion battery according to any one of the embodiments in the first aspect. A third aspect of this application provides a battery module containing the lithium-ion battery in the second aspect of this application. A fourth aspect of this application provides a battery pack containing the battery module in the third aspect of this application. The lithium-ion battery, the battery module, and the battery pack achieve excellent pre-lithiation effect due to the use of the positive electrode plate of this application. To be specific, the undesirable battery power caused by a product resulting from a pre-lithiation material releasing lithium is well addressed, the effective service life of the battery is significantly extended, and the battery is secured with stable and excellent efficiency, conductivity, power, and energy density in the effective service life of the battery.
A fifth aspect of this application provides an electric apparatus containing at least one of the lithium-ion battery, the battery module, or the battery pack in any one of the foregoing aspects. The electric apparatus achieves excellent pre-lithiation effect due to the use of the positive electrode plate of this application. To be specific, the undesirable battery power caused by a product resulting from a pre-lithiation material releasing lithium is well addressed, the effective service life of the battery is significantly extended, and the battery is secured with stable and excellent efficiency, conductivity, power, and energy density in the effective service life of the battery, thereby ensuring long-term stable operation of the electric apparatus.
The following specific embodiments describe design details of a positive electrode plate and a lithium-ion battery, battery module, battery pack, and electric apparatus containing the same designed in this application.
“Ranges” disclosed herein are defined in the form of lower and upper limits. Given ranges are defined by selecting lower and upper limits, and the selected lower and upper limits define boundaries of special ranges. Ranges defined in this method may or may not include end values, and any combinations may be used, meaning any lower limit may be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are provided for a specific parameter, it is understood that ranges of 60-110 and 80-120 can also be envisioned. In addition, if minimum values of a range are given as 1 and 2, and maximum values of the range are given as 3, 4, and the following ranges can all be envisioned: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise specified, a value range of “a-b” is a short representation of any combination of real numbers from a to b, where both a and b are real numbers. For example, a value range of “0-5” means that all real numbers in the range of “0-5” are listed herein, and “0-5” is just a short representation of a combination of these values. In addition, a parameter expressed as an integer greater than or equal to 2 is equivalent to disclosure that the parameter is, for example, an integer among 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and the like.
In this application, unless otherwise specified, all the embodiments and preferred embodiments mentioned herein may be combined with each other to form new technical solutions.
In this application, unless otherwise specified, all the technical features and preferred features mentioned herein may be combined with each other to form new technical solutions.
In this application, unless otherwise specified, “contain” and “include” mentioned herein may refer to open or closed inclusion. For example, the terms “contain” and “include” can mean that other unlisted components may also be contained or included, or only listed components may be contained or included.
In the descriptions of this specification, it should be noted that “more than” and “less than” are inclusive of the present number and that “more” in “one or more” means two or more than two, unless otherwise specified.
In the descriptions of this specification, unless otherwise stated, the term “or” is inclusive. For example, the phrase “A or B” means “A, B, or both A and B”. More specifically, any one of the following conditions satisfies the condition “A or B”: A is true (or present) and B is false (or not present); A is false (or not present) and B is true (or present); or both A and B are true (or present).
In this application, the terms “lithium-ion battery” and “lithium-ion secondary battery” are used interchangeably and used to represent lithium-ion batteries that can be repeatedly charged and discharged. In the full text of this application, the terms “negative electrode” and “anode” are used interchangeably, meaning a same electrode in the battery. The terms “positive electrode” and “cathode” are used interchangeably, meaning a same electrode in the battery.
According to an embodiment of this application, a positive electrode plate for lithium-ion battery is developed. The positive electrode plate includes a current collector, at least one capacity layer, and at least one power layer.
According to an embodiment of this application, the current collector is a metal foil, a metal alloy foil, a polymer sheet with a metal coating, or a polymer sheet with a metal alloy coating, where metal in the metal foil and the metal coating is selected from copper, silver, iron, titanium, nickel, and aluminum; metal in the metal alloy foil and the metal alloy coating is selected from copper alloy, nickel alloy, titanium alloy, silver alloy, iron alloy, and aluminum alloy; and the polymer sheet is selected from polypropylene, polyethylene glycol terephthalate, polybutylene terephthalate, polystyrene, and mixtures or copolymers thereof.
In the full text of this application, the “capacity layer” mainly contains a “high gram capacity/high energy” positive active material and serves as a layer to provide a high energy density for batteries. According to an embodiment of this application, the capacity layer includes a first binder, a first conductive agent, and a first positive electrode active material, the first positive electrode active material having a first median particle size. Preferably, based on the total weight of the capacity layer, the capacity layer includes 1-30 wt % of the binder, 0.1-10 wt % of the conductive agent, and 60-95 wt % of the first positive electrode active material. According to an embodiment of this application, the capacity layer does not contain a pre-lithiation agent intentionally added, especially the pre-lithiation agent mentioned in the following description of composition of the power layer.
In this application, compositions of the capacity layer and the power layer, for example, a binder, a conductive agent, and a positive electrode active material, are each defined by prefixes “first” and “second” when being described. This is only to distinguish the compositions in the two layers in expression, but not to limit that the corresponding compositions in the two layers are necessarily different. The protection scope of this application covers embodiments in which same or different types of binders, conductive agents, and/or positive electrode active materials are used in the capacity layer and the power layer, respectively.
According to an embodiment of this application, the first positive electrode active material for the capacity layer is selected from one or more of the following: lithium cobaltate, lithium iron phosphate, lithium manganese iron phosphate, lithium vanadium phosphate, lithium vanadyl phosphate, lithium vanadate, lithium manganate, positive electrode active material shown in formula I, positive electrode active material shown in formula II, and a combination thereof:
LiNixCoyAzO2 formula I
where A is selected from one or more of the following elements: manganese, aluminum, copper, zinc, tin, titanium, magnesium, and iron, 0.01≤x≤0.98, 0.01≤y≤0.98, 0.01≤z≤0.98, and x+y+z=1. For the positive electrode active material shown in formula I, a value of x may be within the range obtained by using any two of the following values as upper and lower limits respectively: 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.05, 0.06, 0.07, 0.075, 0.08, 0.085, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, ⅓, 0.35, 0.4, 0.45, 0.5, 0 55, 0.6, 0.65, ⅔, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, and 0.99; a value of y may be within the range obtained by using any two of the following values as upper and lower limits respectively: 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.05, 0.06, 0.07, 0.075, 0.085, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, ⅓, 0.35, 0.4, 0.45, 0.5, 0 55, 0.6, 0.65, ⅔, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, and 0.99; and a value of z may be within the range obtained by using any two of the following values as upper and lower limits respectively: 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.05, 0.06, 0.07, 0.075, 0.08, 0.085, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, ⅓, 0.35, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, ⅔, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, and 0.99, where the values of x, y, and z satisfy x+y+z=1.
LiFe1-m-nMnmBnPO4 formula II
in formula II, 0≤m≤1, 0≤n≤0.1, and B is selected from at least one of transition metal elements other than Fe and Mn and non-transition metal elements. For example, for the positive electrode active material shown in formula II, a value of m may be within the range obtained by using any two of the following values as upper and lower limits respectively: 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.05, 0.06, 0.07, 0.075, 0.08, 0.085, 0.09, 0.1, 0.15, 0.2, 0.25, 0.3, ⅓, 0.35, 0.4, 0.45, 0.5, 0 55, 0.65, ⅔, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, and 0.99; a value of n may be within the range obtained by using any two of the following values as upper and lower limits respectively: 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.05, 0.06, 0.07, 0.075, 0.08, 0.085, 0.09, and 0.1; and B may be selected from the following metal elements: Cu, Ni, Cr, Mo, Zn, Sn, Mg, Ca, Co, Zr, Si, Ru, V, Nb, and a combination thereof.
According to another independent embodiment of this application, the capacity layer includes only lithium iron phosphate (LiFePO4) as the first positive electrode active material, that is, the capacity layer does not include the first positive electrode active material other than lithium iron phosphate.
Based on the total weight of the capacity layer, a percentage of the first positive electrode active material may be 60-98.5 wt %, for example, 70-98 wt % or 80-97 wt %. For example, a percentage of the first binder may be within the range obtained by using any two of the following values as upper and lower limits respectively: 60 wt %, 61 wt %, 62 wt %, 63 wt %, 64 wt %, 65 wt %, 66 wt %, 67 wt %, 68 wt %, 69 wt %, 70 wt %, 71 wt %, 72 wt %, 73 wt %, 74 wt %, 75 wt %, 76 wt %, 77 wt %, 78 wt %, 79 wt %, 80 wt %, 81 wt %, 82 wt %, 83 wt %, 84 wt %, 85 wt %, 86 wt %, 87 wt %, 88 wt %, 89 wt %, 90 wt %, 91 wt %, 92 wt %, 93 wt %, 94 wt %, 95 wt %, 96 wt %, 97 wt %, 98 wt %, and 98.5 wt %.
In this application, a median particle size by volume is used to describe a particle size, and the median particle size by volume is measured using a laser scattering particle size analyzer. The particle size can be represented by D10, D50, D90, and D99. “D50=specific value” means that in the total volume set of particles under test, 50% (by volume) particles have a particle size greater than the specific value and the remaining 50% (by volume) particles have a particle size smaller than this particle size. “D10=specific value” means that in the total volume set of particles under test, 10% (by volume) particles have a particle size less than the specific value and the remaining particles have a particle size greater than the specific value. “D90=specific value” means that in the total volume set of particles under test, 90% (by volume) particles have a particle size less than the specific value and the remaining particles have a particle size greater than the specific value. “D99=specific value” means that in the total volume set of particles under test, 99% (by volume) particles have a particle size less than the specific value and the remaining particles have a particle size greater than the specific value. In this application, a median particle size by volume D50 of is used to describe a median particle size of particles. In other words, unless otherwise specified, the terms “median particle size”, “median particle size by volume”, and “volume-based median particle size” all indicate D50 of particles.
According to an embodiment of this application, D10 of the first positive electrode active material is greater than 0.3 μm and less than or equal to 0.6 μm. For example, D10 may be within the range obtained by using any two of the following values as upper and lower limits respectively: 0.31 μm, 0.4 μm, 0.5 μm, and 0.6 μm. According to an embodiment of this application, D90 of the first positive electrode active material is greater than 1.2 μm and less than or equal to 4 μm. For example, D90 may be within the range obtained by using any two of the following values as upper and lower limits respectively: 1.21 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3.0 μm, 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, and 4.0 μm. According to an embodiment of this application, D99 of the first positive electrode active material is greater than 3.0 μm, for example, may be 3.1-8.0 μm. For example, D99 may be within the range obtained by using any two of the following values as upper and lower limits respectively: 3.1 μm, 3.2 μm, 3.3 μm, 3.4 μm, 3.5 μm, 3.6 μm, 3.7 μm, 3.8 μm, 4.0 μm, 4.1 μm, 4.2 μm, 4.3 μm, 4.4 μm, 4.5 μm, 4.6 μm, 4.7 μm, 4.8 μm, 4.9 μm, 5.0 μm, 5.1 μm, 5.2 μm, 5.3 μm, 5.4 μm, 5.5 μm, 5.6 μm, 5.7 μm, 5.8 μm, 5.9 μm, 6.0 μm, 6.1 μm, 6.2 μm, 6.3 μm, 6.4 μm, 6.5 μm, 6.6 μm, 6.7 μm, 6.8 μm, 6.9 μm, 7.0 μm, 7.1 μm, 7.2 μm, 7.3 μm, 7.4 μm, 7.5 μm, 7.6 μm, 7.7 μm, 7.8 μm, 7.9 μm, and 8.0 μm.
According to another independent embodiment of this application, a median particle size by volume (also called volume-based median particle size) D50 of the first positive electrode active material is 0.8-1.3 μm. For example, the median particle size by volume D50 may be within the range obtained by using any two of the following values as upper and lower limits respectively: 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.2 μm, and 1.3 μm. Preferably, D50 of the first positive electrode active material for the capacity layer is greater than D50 of a second positive electrode active material for the power layer. More preferably, the following relationships are satisfied at the same time: D50 of the first positive electrode active material for the capacity layer is greater than D50 of the second positive electrode active material for the power layer, D10 of the first positive electrode active material is greater than D10 of the second positive electrode active material, D90 of the first positive electrode active material is greater than D90 of the second positive electrode active material, and D99 of the first positive electrode active material is greater than D99 of the second positive electrode active material.
According to an embodiment of this application, the first binder for the capacity layer may include one or more of the following: polyvinylidene fluoride, polyvinyl alcohol, polyacrylic acid, polymethylacrylic acid, carboxymethyl cellulose (CMC), sodium carboxymethyl cellulose, amylum, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, propylene-ethylene-ethylidene norbornene terpolymer, sulfonate-propylene-ethylene-ethylidene norbornene terpolymer, polystyrene-butadiene rubber (styrene-butadiene rubber, also referred to as SBR), fluorine-containing rubber, polytrifluorochloroethylene, water soluble unsaturated resin SR-1B, sodium alga acid, polyurethane, sodium polyacrylate, sodium polymethacrylate, acrylamide, carboxymethyl chitosan, and mixture or copolymers thereof. Based on the total weight of the capacity layer, a percentage of the first binder may be 1-30 wt %, for example, 1-10 wt % or 2-5 wt %. For example, the percentage of the first binder may be within the range obtained by using any two of the following values as upper and lower limits respectively: 1 wt %, 2 wt %, 3 wt %, 4 wt %, 5 wt %, 6 wt %, 7 wt %, 8 wt %, 9 wt %, 10 wt %, 11 wt %, 12 wt %, 13 wt %, 14 wt %, 15 wt %, 16 wt %, 17 wt %, 18 wt %, 19 wt %, 20 wt %, 21 wt %, 22 wt %, 23 wt %, 24 wt %, 25 wt %, 26 wt %, 27 wt %, 28 wt %, 29 wt %, and 30 wt %.
According to an embodiment of this application, the first conductive agent for the capacity layer may include one or more of the following: superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene graphite, meso-carbon microbeads, soft carbon, hard carbon, carbon fiber, graphene, Super P, furnace black, vapor grown carbon fiber (VGCF), and carbon nanofiber. Based on the total weight of the capacity layer, a percentage of the first conductive agent may be 0.1-10 wt %, for example, 0.5-5 wt % or 1-2 wt %. For example, the percentage of the first conductive agent may be within the range obtained by using any two of the following values as upper and lower limits respectively: 0.1 wt %, 0.2 wt %, 0.3 wt %, 0.4 wt %, 0.5 wt %, 0.6 wt %, 0.7 wt %, 0.8 wt %, 0.9 wt %, 1 wt %, 1.2 wt %, 1.5 wt %, 1.8 wt %, 2 wt %, 3 wt %, 4 wt %, 5 wt %, 6 wt %, 7 wt %, 8 wt %, 9 wt %, and 10 wt %. According to a most preferred embodiment, the first conductive agent contained in the capacity layer is a carbon-based conductive agent, for example, one or more of the foregoing carbon-based conductive agents. Based on the total weight of the capacity layer, the percentage of the first conductive agent is ≤1.3 wt %, for example, 1.2 wt %. Preferably, the percentage of the first conductive agent in the capacity layer is less than the percentage of the second conductive agent in the power layer.
According to another independent embodiment of this application, a compacted density of the capacity layer is higher than a compacted density of the power layer, and a BET specific surface area of the capacity layer is less than a BET specific surface area of the power layer. According to an embodiment of this application, the capacity layer may have a compacted density of ≥2.4 g/cm3, for example, 2.4-3.0 g/cm3. For example, the compacted density may be within the range obtained by using any two of the following values as upper and lower limits respectively: 2.4 g/cm3, 2.5 g/cm3, 2.6 g/cm3, 2.7 g/cm3, 2.8 g/cm3, 2.9 g/cm3, and 3 g/cm3. According to another embodiment of this application, the BET specific surface area of the capacity layer is ≤13 m2/g or is 5-13 m2/g. For example, the BET specific surface area may be within the range obtained by using any two of the following values as upper and lower limits respectively: 5 m2/g, 6 m2/g, 7 m2/g, 8 m2/g, 9 m2/g, 10 m2/g, 11 m2/g, 12 m2/g, and 13 m2/g.
In the full text of this application, the “power layer” mainly contains a “high-power” positive active material and serves a layer to provide a high power for batteries. The power layer according to this application contains both the second positive electrode active material and the pre-lithiation agent, and the particle size of the second positive electrode active material is specially designed so as to provide an excellent electronic conductive network for the pre-lithiation agent, thereby effectively inhibiting or significantly eliminating the impact on the overall conductivity of the positive electrode plate caused by of a product resulting from the pre-lithiation agent releasing lithium. According to an embodiment of this application, the power layer includes a second binder, a second conductive agent, a pre-lithiation agent, and a second positive electrode active material, the second positive electrode active material having a second median particle size. As described above, a second average diameter of the second positive electrode active material is significantly less than a first average diameter of the first positive electrode active material.
According to an embodiment of this application, the second binder for the power layer may include one or more of the first binders listed above that can be used for the capacity layer. Preferably, for the purpose of simplifying a manufacturing process, a same type of binder is used in the power layer and the capacity layer. Based on the total weight of the power layer, a percentage of the second binder may be 1-30 wt %, for example, 1-10 wt % or 2-5 wt %. For example, the percentage of the second binder may be within the range obtained by using any two of the following values as upper and lower limits respectively: 1 wt %, 2 wt %, 3 wt %, 4 wt %, 5 wt %, 6 wt %, 7 wt %, 8 wt %, 9 wt %, 10 wt %, 11 wt %, 12 wt %, 13 wt %, 14 wt %, 15 wt %, 16 wt %, 17 wt %, 18 wt %, 19 wt %, 20 wt %, 21 wt %, 22 wt %, 23 wt %, 24 wt %, 25 wt %, 26 wt %, 27 wt %, 28 wt %, 29 wt %, and 30 wt %.
According to an embodiment of this application, the second conductive agent for the power layer may include one or more of the first conductive agents listed above that can be used for the capacity layer. Preferably, for the purpose of simplifying a manufacturing process, a same type of conductive agent is used in the power layer and the capacity layer. Based on the total weight of the power layer, a percentage of the second conductive agent may be 0.1-10 wt %, for example, 0.5-5 wt % or 1-2 wt %. For example, the percentage of the second conductive agent may be within the range obtained by using any two of the following values as upper and lower limits respectively: 0.1 wt %, 0.2 wt %, 0.3 wt %, 0.4 wt %, 0.5 wt %, 0.6 wt %, 0.7 wt %, 0.8 wt %, 0.9 wt %, 1 wt %, 1.2 wt %, 1.5 wt %, 1.8 wt %, 2 wt %, 3 wt %, 4 wt %, 5 wt %, 6 wt %, 7 wt %, 8 wt %, 9 wt %, and 10 wt %. According to a most preferred embodiment, the second conductive agent contained in the power layer is a carbon-based conductive agent, for example, one or more of the foregoing carbon-based conductive agents. Preferably, based on the total weight of the power layer, the percentage of the second conductive agent is ≥1.4 wt %, for example, 1.45 wt %.
According to an embodiment of this application, the second positive electrode active material for the power layer may include one or more of the first positive electrode active materials listed above that can be used for the capacity layer. Preferably, for the purpose of simplifying a manufacturing process, a same type of positive electrode active material is used in the power layer and the capacity layer. More preferably, lithium iron phosphate is used in both the power layer and the capacity layer as the positive electrode active material.
According to an embodiment of this application, based on the total weight of the power layer, a percentage of the second positive electrode active material may be 50-97 wt %, for example, 70-94 wt % or 80-90 wt %. For example, a percentage of the second binder may be within the range obtained by using any two of the following values as upper and lower limits respectively: 60 wt %, 61 wt %, 62 wt %, 63 wt %, 64 wt %, 65 wt %, 66 wt %, 67 wt %, 68 wt %, 69 wt %, 70 wt %, 71 wt %, 72 wt %, 73 wt %, 74 wt %, 75 wt %, 76 wt %, 77 wt %, 78 wt %, 79 wt %, 80 wt %, 81 wt %, 82 wt %, 83 wt %, 84 wt %, 85 wt %, 86 wt %, 87 wt %, 88 wt %, 89 wt %, 90 wt %, 91 wt %, 92 wt %, 93 wt %, 94 wt %, 95 wt %, 96 wt %, and 97 wt %.
According to an embodiment of this application, D10 of the second positive electrode active material is ≤0.3 μm, for example <0.3 μm, or 0.1-0.25 μm. For example, D10 may be within the range obtained by using any two of the following values as upper and lower limits respectively: 0.1 μm, 0.15 μm, 0.20 μm, 0.25 μm, 0.28 μm, 0.29 μm, and 0.30 μm; and D10 of the second positive electrode active material is less than D10 of the first positive electrode active material. According to an embodiment of this application, D90 of the second positive electrode active material is ≤1.2 μm, for example <1.2 μm, or 0.5-1.1 μm. For example, D90 may be within the range obtained by using any two of the following values as upper and lower limits respectively: 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1.0 μm, 1.1 μm, 1.15 μm, and 1.20 μm; and D90 of the second positive electrode active material is less than D90 of the first positive electrode active material. According to an embodiment of this application, D99 of the second positive electrode active material is ≤3.0 μm, for example, may be 1.0-3.0 μm. For example, D99 may be within the range obtained by using any two of the following values as upper and lower limits respectively: 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, and 3.0 μm; and D99 of the second positive electrode active material is less than D99 of the first positive electrode active material. According to another independent embodiment of this application, a median particle size by volume (also called volume-based median particle size) D50 of the second positive electrode active material is ≤0.45 μm, or is 0.2-0.45 μm. For example, D50 may be within the range obtained by using any two of the following values as upper and lower limits respectively: 0.20 μm, 0.21 μm, 0.22 μm, 0.23 μm, 0.24 μm, 0.25 μm, 0.26 μm, 0.27 μm, 0.28 μm, 0.29 μm, 0.30 μm, 0.31 μm, 0.32 μm, 0.33 μm, 0.34 μm, 0.35 μm, 0.36 μm, 0.37 μm, 0.38 μm, 0.39 μm, 0.40 μm, 0.41 μm, 0.42 μm, 0.43 μm, 0.44 μm, and 0.45 μm; and D50 of the second positive electrode active material is less than D50 of the first positive electrode active material.
According to an embodiment of this application, the pre-lithiation agent for the capacity layer is selected from one or more of the following: Li2M1O2, where M1 is selected from one or more of the following: Cu, Ni, Mn, Fe, Cr, Mo, Zn, Sn, Mg, and Ca; Li2M2O3, where M2 is selected from one or more of the following: Ni, Co, Fe, Mn, Sn, Cr, Mo, Zr, Si, Cu, and Ru; Li2M3O4, where M3 is selected from one or more of the following: Ni, Co, Fe, Mn, Sn, Cr, V, and Nb; Li3M4O4, where M4 is selected from one or more of the following: Cu, Ni, Mn, Fe, Cr, Mo, Zn, Sn, Mg, and Ca; Li5M5O4, where M5 is selected from one or more of the following: Ni, Co, Fe, Mn, Sn, Cr, Mo, and Al; Li5M6O6, where M6 is selected from one or more of the following: Cu, Ni, Mn, Fe, Cr, Mo, Zn, Sn, Mg, and Ca; Li6M7O4, where M5 is selected from one or more of the following: Ni, Co, Mn, Fe, and Ru; and LiaCbOc, where a is an integer 1 or 2, b is an integer 0, 1, 2, 3, or 4, and c is an integer 1, 2, 3, 4, 5, or 6.
According to an embodiment of this application, the pre-lithiation agent is selected from one or more of the following: Li2NiO2, Li2Cu0.5Ni0.5O2, Li2MoO3, Li5FeO4, Li5Fe0.9Al0.1O4, Li6MnO4, Li6Mn0.5Ru0.5O4, Li2O, Li2O2, Li2C2O4, Li2C4O4, LiC2O2, Li2C3O5, and Li2C4O6. According to a preferred embodiment of this application, the pre-lithiation agent includes Li2Cu0.5Ni0.5O2, Li5FeO4, and a combination thereof.
According to an embodiment of this application, a median particle size by volume D50 of the pre-lithiation agent is 5-15 μm, and preferably 6-10 μm. For example, D50 may be within the range obtained by using any two of the following values as upper and lower limits respectively: 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 11 μm, 12 μm, 13 μm, 14 μm, and 15 μm. According to an embodiment of this application, based on the total weight of the power layer, a percentage of the pre-lithiation agent may be 0.1-30 wt %, for example, 0.5-20 wt % or 1-10 wt %. For example, the percentage of the pre-lithiation agent can be within the range obtained by using any two of the following values as upper and lower limits respectively: 0.1 wt %, 0.2 wt %, 0.5 wt %, 0.8 wt %, 1.0 wt %, 1.2 wt %, 1.5 wt %, 1.8 wt %, 2.0 wt %, 2.2 wt %, 2.5 wt %, 2.8 wt %, 3.0 wt %, 3.2 wt %, 3.5 wt %, 3.8 wt %, 4.0 wt %, 4.2 wt %, 4.5 wt %, 4.8 wt %, 5.0 wt %, 5.2 wt %, 5.5 wt %, 5.8 wt %, 6.0 wt %, 6.2 wt %, 6.5 wt %, 6.8 wt %, 7.0 wt %, 7.2 wt %, 7.5 wt %, 7.8 wt %, 8.0 wt %, 8.2 wt %, 8.5 wt %, 8.8 wt %, 9.0 wt %, 9.2 wt %, 9.5 wt %, 9.8 wt %, 10.0 wt %, 11 wt %, 12 wt %, 13 wt %, 14 wt %, 15 wt %, 16 wt %, 17 wt %, 18 wt %, 19 wt %, 20 wt %, 21 wt %, 22 wt %, 23 wt %, 24 wt %, 25 wt %, 26 wt %, 27 wt %, 28 wt %, 29 wt %, and 30%.
According to another independent embodiment of this application, a compacted density of the power layer is less than a compacted density of the capacity layer, and a BET specific surface area of the power layer is greater than a BET specific surface area of the capacity layer. According to an embodiment of this application, the capacity layer may have a compacted density of ≤2.3 g/cm3, for example, 1.8-2.3 g/cm3. For example, the compacted density may be within the range obtained by using any two of the following values as upper and lower limits respectively: 1.8 g/cm3, 1.9 g/cm3, 2.0 g/cm3, 2.1 g/cm3, 2.2 g/cm3, and 2.3 g/cm3. According to another embodiment of this application, the BET specific surface area of the capacity layer is ≥14 m2/g or is 14-25 m2/g. For example, the BET specific surface area may be within the range obtained by using any two of the following values as upper and lower limits respectively: 14 m2/g, 15 m2/g, 16 m2/g, 17 m2/g, 18 m2/g, 19 m2/g, 20 m2/g, 21 m2/g, 22 m2/g, 23 m2/g, 24 m2/g, and 25 m2/g.
According to an embodiment of this application, a total coating weight of the power layer and the capacity layer (a sum of coating weights of the power layer and the capacity layer per unit area) may be 5-26 g/cm2, for example, 5 g/cm2, 6 g/cm2, 7 g/cm2, 8 g/cm2, 9 g/cm2, 10 g/cm2, 11 g/cm2, 12 g/cm2, 13 g/cm2, 14 g/cm2, 15 g/cm2, 16 g/cm2, 17 g/cm2, 18 g/cm2, 19 g/cm2, 20 g/cm2, 21 g/cm2, 22 g/cm2, 23 g/cm2, 24 g/cm2, 25 g/cm2, or 26 g/cm2. According to another embodiment of this application, a solid weight ratio of the power layer and the high-capacity layer is 1:9 to 9:1, preferably 2:8 (namely, 1:4) to 1:1, and more preferably 2:8 (namely, 1:4) to 1:2. For example, the solid weight ratio of the power layer and the high-capacity layer may be within the range obtained by using any two of the following values as upper and lower limits respectively: 1:9, 1:8, 1:7, 1:6, 1:5, 1:4, 1:3, 1:2, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, and 9:1.
In the embodiments of this application, the capacity layer and the power layer on the current collector may be prepared by mixing respective components of each layer and other optional additives with a solvent or dispersant, for example, N-methylpyrrolidone (NMP) or deionized water, to form a slurry, and applying the slurry in sequence, followed by drying and cold pressing, to form a positive electrode plate including the current collector, the capacity layer, and the power layer. For example, other additives optionally contained in the capacity layer and the power layer are a thickener, a PTC thermistor material, and the like. The slurry can be applied using a conventional coating technique, for example, curtain coating, blade coating, tape casting coating, or gravure roll coating.
According to an embodiment of this application, the capacity layer and the power layer are in direct contact with each other, without any other layer therebetween. According to another embodiment of this application, one or more additional intermediate layers are optionally disposed between the capacity layer and the power layer. For example, the intermediate layer may be a conductive primer layer (which may be composed of a binder and a conductive agent, for example, the binder and conductive agent listed in the foregoing description of the capacity layer), or may contain any other auxiliary agents known in the art, or may optionally contain same or different positive electrode active materials.
The positive electrode plate described in the foregoing embodiments of this application can be used in lithium-ion batteries. In an embodiment of this application, the lithium-ion battery includes a positive electrode plate, a negative electrode plate, a separator, an electrolyte, and the like. During battery charging and discharging, active ions are intercalated and deintercalated between the positive electrode plate and the negative electrode plate. The electrolyte migrates ions between the positive electrode plate and the negative electrode plate.
The lithium-ion battery of this application includes the negative electrode plate, where the negative electrode plate includes a negative electrode current collector and a negative electrode film layer provided on at least one surface of the negative electrode current collector, and the negative electrode film layer includes a negative electrode active material, a binder, a conductive agent, and another optional additive. In an embodiment of this application, examples of the negative electrode active material include one or more of the following: natural graphite, artificial graphite, soft carbon, hard carbon, silicon-based material, tin-based material, and lithium titanate. The silicon-based material may be selected from one or more of elemental silicon, silicon oxide, and a silicon-carbon composite. The tin-based material may be selected from one or more of elemental tin, tin-oxygen compounds, and tin alloys. In an example, the conductive agent may include one or more of superconducting carbon, carbon black (for example, acetylene black and Ketjen black), carbon dots, carbon nanotubes, graphene, and carbon nanofibers. The binder may include styrene-butadiene rubber (SBR), water soluble unsaturated resin SR-1B, poly acrylic acid (PAA), polymethylacrylic acid (PMAA), polyacrylic acid sodium (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), and carboxymethyl chitosan (CMCS). Other optional additives are, for example, thickeners (for example, carboxymethyl cellulose CMC and sodium carboxymethyl cellulose CMC-Na), PTC thermistor materials, and the like.
According to an embodiment of this application, the negative electrode plate can be prepared by dispersing the negative electrode active material, binder, conductive agent, other optional additives, and the like in a solvent, and stirring to form a uniform slurry with a specified solid percentage, where the solvent may be N-methylpyrrolidone (NMP) or deionized water, and based on a total weight of the prepared slurry, the solid percentage of the slurry may be 30-80 wt %, for example, 50-70 wt %, or 55-65 wt %; and applying the slurry on the negative electrode current collector, followed by drying and optionally cold pressing, to form the negative electrode plate, where the negative electrode current collector may be a metal foil or a composite current collector, for example, the metal foil may be a copper foil, a silver foil, an iron foil, or a foil made of alloys of the foregoing metal. The composite current collector may include a polymer matrix and a metal layer formed on at least one surface of the polymer matrix, and may be formed by forming a metal material (such as copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver, and silver alloy) on the polymer matrix (for example, a matrix of polypropylene PP, polyethylene glycol terephthalate PET, polybutylene terephthalate PBT, polystyrene PS, polyethylene PE, and copolymers thereof).
In addition, in the battery of this application, the negative electrode plate does not exclude additional functional layers other than the negative electrode active material layer. For example, in some embodiments, the negative electrode plate according to this application may further include a conductive primer layer (for example, consisting of the conductive agent and binder described above that can be used for the negative electrode active material layer) sandwiched between the negative electrode current collector and the negative electrode active material layer and disposed on the surface of the negative electrode current collector. In some other embodiments, the negative electrode plate according to this application may further include a protective layer covering the surface of the negative electrode active material layer.
The electrolyte migrates ions between the positive electrode plate and the negative electrode plate. The electrolyte may be selected from at least one of a solid electrolyte and a liquid electrolyte (or electrolyte solution). In some embodiments, the electrolyte is a liquid electrolyte. The electrolyte includes an electrolytic salt and a solvent. In some embodiments, the electrolytic salt may be selected from one or more of LiPF6 (lithium hexafluorophosphate), LiBF4 (lithium tetrafluoroborate), LiClO4 (lithium perchlorate), LiAsF6 (lithium hexafluoroborate), LiFSI (lithium bis(fluorosulfonyl)imide), LiTFSI (lithium bis-trifluoromethanesulfonimide), LiTFS (lithium trifluoromethanesulfonat), LiDFOB (lithium difluorooxalatoborate), LiBOB (lithium bisoxalatoborate), LiPO2F2 (lithium difluorophosphate), LiDFOP (lithium difluorophosphate), and LiTFOP (lithium tetrafluoro oxalate phosphate). In an embodiment of this application, the solvent may be selected from one or more of the following: ethylene carbonate (EC), propylene carbonate (PC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), butylene carbonate (BC), fluoroethylene carbonate (FEC), methylmethyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), methyl butyrate (MB), ethyl butyrate (EB), 1,4-butyrolactone (GBL), tetramethylene sulfone (SF), methyl sulfone (MSM), ethyl methyl sulfone (EMS), and diethyl sulfone (ESE), and preferably a mixture of two or more of the foregoing solvents, for example, a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC), and more preferably a mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) at a volume ratio of 1:1. In an embodiment of this application, based on the total weight of the electrolyte, a percentage of the solvent is 60-99 wt %, for example, 65-95 wt %, 70-90 wt %, 75-89 wt %, or 80-85 wt %, or within a value range defined by any one of the upper limits and any one of the lower limits. In an embodiment of this application, based on the total weight of the liquid electrolyte, a percentage of the electrolyte is 1-40 wt %, for example, 5-35 wt %, 10-30 wt %, 11-25 wt %, or 15-20 wt %, or within a value range defined by any one of the upper limits and any one of the lower limits.
In an embodiment of this application, the electrolyte may further optionally include an additive. For example, the additive may include one or more of the following: a negative electrode film forming additive and a positive electrode film forming additive, or may include an additive capable of improving some performance of batteries, for example, an additive for improving over-charge performance of batteries, an additive for improving high-temperature performance of batteries, or an additive for improving low-temperature performance of batteries.
In an embodiment of this application, the battery further includes a separator, where the separator separates a positive electrode side of the battery from a negative electrode side, and provides selective transmission or barrier for substances of different types, sizes and charges in the system. For example, the separator is an electronic insulator, which physically separates the positive electrode active material of the battery from the negative electrode active material of the battery, preventing internal short circuit and forming an electric field in a given direction, and which allows ions in the battery to migrate between the positive and negative electrodes through the separator. In an embodiment of this application, a material for preparing the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride, and may be a porous film or a non-porous film, and preferably a polyethylene-polypropylene porous film. The separator may be a single-layer film or a multilayer composite film. When the separator is a multilayer composite thin film, each layer may be made of the same or different materials.
In an embodiment of this application, the above positive electrode plate, negative electrode plate, and separator may be made into an electrode assembly/a bare cell through winding or lamination.
In an embodiment of this application, the lithium-ion battery may include an outer package, or a housing. The outer package may be used for packaging the electrode assembly and the electrolyte. In some embodiments, the outer package of the battery may be a hard shell, for example, a hard plastic shell, an aluminum shell, or a steel shell. In some other examples, the outer package of the battery may alternatively be a soft pack, for example, a soft pouch. A material of the soft pack may be plastic, for example, one or more of polypropylene (PP), polybutylene terephthalate (PBT), polybutylene succinate (PBS), and the like.
The battery according to this application may be cylindrical, rectangular, or of any other shapes.
According to an embodiment of this application, after the battery is assembled and the electrolyte is injected into the battery, the battery is subjected to conventional formation, so that a solid electrolyte interface layer (SEI film) is formed on a surface of the negative electrode, thereby obtaining a battery meeting product requirements.
In an embodiment of this application, a plurality of batteries may be assembled into a battery module, the battery module includes two or more batteries, and a quantity of batteries included in the battery module depends on application of the battery module land parameters of a single battery module.
In an embodiment of this application, two or more battery modules may be assembled into a battery pack, and a quantity of battery modules included in the battery pack depends on application of the battery pack and parameters of a single battery module. The battery pack may include a battery box and a plurality of battery modules disposed in the battery box, where the battery box includes an upper box body and a lower box body, the upper box body can cover and fits well with the lower box body to form an enclosed space for accommodating the battery modules. The two or more battery modules may be arranged in the battery box in a required manner.
Electric Apparatus
In an embodiment of this application, the electric apparatus according to this application includes at least one of the battery, the battery module, or the battery pack according to this application. The battery, the battery module, or the battery pack may be used as a power source for the electric apparatus or an energy storage unit of the electric apparatus. The electric apparatus includes, but is not limited to, a mobile digital device (for example, a mobile phone or a notebook computer), an electric vehicle (for example, a battery electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, an electric bicycle, an electric scooter, an electric golf vehicle, or an electric truck), an electric train, a ship, a satellite, an energy storage system, and the like.
In another example, the apparatus may be a mobile phone, a tablet computer, a laptop computer, or the like. The apparatus usually needs to be light and thin, and a battery may be used as a power source.
How the positive electrode plate prepared according to the embodiments of this application influences performance of electric apparatuses is characterized hereinafter based on specific examples. However, it should be noted in particular that the scope of protection of this application is defined by the claims without being limited to the above embodiments.
Various raw materials described in Table 1 below are used in the examples. Unless otherwise specified, the raw materials used in the examples of this application are all commercially available products.
The particle sizes recorded in this application are measured using a laser scattering particle size analyzer.
In the following Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-4, Li5FeO4 is used as a pre-lithiation agent to prepare lithium-ion batteries and characterize performance thereof.
In Example 1-1, the lithium-ion battery was obtained by the following steps.
Step 1: Preparation of Capacity Layer
In this step, the first positive electrode active material lithium iron phosphate (with a D50 of 1.2 μm), the conductive agent acetylene black, and the binder polyvinylidene fluoride were weighed according to a solid weight ratio of 97:1:2, and these raw materials were mixed in N-methylpyrrolidone to form an uniform slurry with a solid percentage of 62 wt %. In a coating cavity, the slurry was applied on a 60 μm thick aluminum foil current collector, followed by drying and cold pressing, to form a capacity layer. The capacity layer has a coating weight of 15.6 g/cm2 and a compacted density of 2.5 g/cm3.
Step 2: Preparation of Power Layer
In this step, the second positive electrode active material lithium iron phosphate (with a D50 of 0.4 μm), the pre-lithiation agent Li5FeO4 (with a D50 of 5 μm), the conductive agent acetylene black, and the binder polyvinylidene fluoride were weighed according to a solid weight ratio of 94.5:2.5:1:2, and these raw materials were mixed in N-methylpyrrolidone to form an uniform slurry with a solid percentage of 60 wt %. In a coating cavity, the slurry was applied on the capacity layer prepared in Step 1, followed by drying and cold pressing, to form a power layer. The power layer has a coating weight of 4 g/cm2 and a compacted density of 2.3 g/cm3. Thus, the positive electrode plate including the current collector, the capacity layer, and the power layer was prepared. A weight ratio of lithium iron phosphate contained in the power layer and lithium iron phosphate contained in the capacity layer is 2:8.
Step 3: Preparation of Negative Electrode Plate
In this step, the negative electrode active material artificial graphite, the conductive agent acetylene black, and the binder styrene-butadiene rubber, and the thickener sodium carboxymethyl cellulose were weighed according to a solid weight ratio of 96.5:0.7:1.8:1, and these raw materials were mixed in deionized water to form an uniform slurry with a solid percentage of 56 wt %. In a coating cavity, the slurry was applied on a 60 μm thick copper foil current collector, followed by drying and cold pressing, to form a negative electrode plate. A coating weight of the coating layer on the current collector is 10.1 g/cm2.
Step 4: Preparation of Battery
In this step, the positive electrode plate, the separator, and the negative electrode plate were stacked in sequence, to form a laminated structure. The laminated structure was placed in an aluminum battery housing, the electrolyte was injected into the aluminum battery housing, and the housing was packaged. The electrolyte was a lithium hexafluorophosphate electrolyte solution with a concentration of 1.1 M in an EC:DEC=1:1(V:V) solvent mixture. The lithium-ion battery in Example 1 was prepared. In this example and each of the following examples and comparative examples, five batteries were made in parallel for a parallel test of high-temperature storage performance.
In Example 1-2, the lithium-ion battery was obtained through the same steps in Example 1-1, except that in the step of preparing the power layer of the positive electrode plate, the solid weight ratio of the second positive electrode active material lithium iron phosphate, the pre-lithiation agent Li5FeO4, the conductive agent acetylene black, and the binder polyvinylidene fluoride was 96:1:1:2. In addition, the coating weight of the capacity layer was changed correspondingly, so that the weight ratio of lithium iron phosphate contained in the power layer and lithium iron phosphate contained in the capacity layer was kept at 2:8.
In Example 1-3, the lithium-ion battery was obtained through the same steps in Example 1-1, except that in the step of preparing the power layer of the positive electrode plate, the solid weight ratio of the second positive electrode active material lithium iron phosphate, the pre-lithiation agent Li5FeO4, the conductive agent acetylene black, and the binder polyvinylidene fluoride was 87:10:1:2. In addition, the coating weight of the capacity layer was changed correspondingly, so that the weight ratio of lithium iron phosphate contained in the power layer and lithium iron phosphate contained in the capacity layer was kept at 2:8.
In Example 1-4, the lithium-ion battery was obtained through the same steps in Example 1-1, except that in the step of preparing the power layer of the positive electrode plate, the solid weight ratio of the second positive electrode active material lithium iron phosphate, the pre-lithiation agent Li5FeO4, the conductive agent acetylene black, and the binder polyvinylidene fluoride was 77:20:1:2. In addition, the coating weight of the capacity layer was changed correspondingly, so that the weight ratio of lithium iron phosphate contained in the power layer and lithium iron phosphate contained in the capacity layer was kept at 2:8.
In Example 1-5, the lithium-ion battery was obtained through the same steps in Example 1-1, except that the coating weights of the power layer and the capacity layer were adjusted to make the weight ratio of lithium iron phosphate contained in the power layer and lithium iron phosphate contained in the capacity layer be 5:5 while keeping the total coating weight of the power layer and the capacity layer unchanged.
In Example 1-6, the lithium-ion battery was obtained through the same steps in Example 1-1, except that the coating weights of the power layer and the capacity layer were adjusted to make the weight ratio of lithium iron phosphate contained in the power layer and lithium iron phosphate contained in the capacity layer be 8:2 while keeping the total coating weight of the power layer and the capacity layer unchanged.
In Comparative Example 1-1, the lithium-ion battery was obtained through the same steps in Example 1-1, except that in the positive electrode plate, only the capacity layer, but no power layer, was formed on the current collector, and the coating weight of the capacity layer in Comparative Example 1-1 was equal to the sum of the coating weights of the capacity layer and the power layer in Example 1-1.
In Comparative Example 1-2, the lithium-ion battery was obtained through the same steps in Comparative Example 1-1, except that lithium iron phosphate with a D50 of 1.2 μm in Comparative Example 1-1 was all replaced by the same weight of lithium iron phosphate with a D50 of 0.4 μm.
In Comparative Example 1-3, the lithium-ion battery was obtained through the same steps in Example 1-1, except that during preparation of the power layer, solid raw materials used were the second positive electrode active material lithium iron phosphate (with a D50 of 0.4 μm), the conductive agent acetylene black, and the binder polyvinylidene fluoride at a solid weight ratio of 97:1:2, without the pre-lithiation agent.
In Comparative Example 1-4, the lithium-ion battery was obtained through the same steps in Example 1-1, except that during preparation of the power layer, lithium iron phosphate with a D50 of 1.2 μm was used as the second positive electrode active material. In other words, in Comparative Example 1-4, same lithium iron phosphate with a D50 of 1.2 μm was used in the capacity layer and the power layer.
Performance Characterization of Battery
The following techniques were used to test the performance of the batteries prepared in Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-4.
Specific Charge/Discharge Capacity:
At room temperature (25° C.), the battery was charged to an end-of-charge voltage at a constant current of 0.33 C, and charged to 0.05 C at a constant voltage. Measurement was performed to obtain a charging capacity Ec0, and a specific charge capacity was obtained by dividing Ec0 by a mass of the positive electrode active material of the battery. In other words, specific charge capacity (mAh/g)=first-cycle charge capacity/mass of positive electrode active material.
The foregoing charged battery was taken and discharged to an end-of-discharge voltage at a constant current of 0.33 C, and measurement was performed to obtain a discharge capacity Ed0. The specific discharge capacity was obtained by dividing Ed0 by the mass of the positive electrode active material of the battery. In other words, specific discharge capacity (mAh/g)=first-cycle discharge capacity/mass of positive electrode active material.
The specific charge capacity test and the specific discharge capacity test were repeated five times each; and the average values of test results were the specific charge capacity and the specific discharge capacity in Table 1.
Calculation of Volumetric Energy Density of Battery
Parameters of internal dimensions of the battery, length a, width b, and height c, were measured. Each battery was charged at room temperature to a voltage of 3.65 V at 1 C, and then discharged to a voltage of 2.5 V at 1 C, and the discharge energy measured at that time was S0.
Volumetric energy density of battery=S0/(a×b×c)
High-Temperature Storage Performance Test of Battery
For each example, five batteries were tested in parallel. Each battery was charged at room temperature to a voltage of 3.65 V at 1 C, and then discharged to a voltage of 2.5 V at 1 C, and a reversible capacity measured at that time was E0. The battery in a fully charged state was placed in an oven at 60° C. for 100 days. After being taken out, the battery was immediately tested for its reversible capacity recorded as En. The capacity retention rate E of the battery stored at 60° C. for 100 days was calculated according to the following formula, and results were summarized in Table 1 below.
ε=(En−E0)/E0×100%
Direct-Current Resistance Test
The secondary battery under test was charged at room temperature to a voltage of 3.65 V at 1 C, and then discharged to a voltage of 2.5 V at 1 C, and the reversible capacity measured at that time was E0.
The secondary battery under test was charged at room temperature to a voltage of 3.65 V at 0.33 C, discharged for 90 min at 0.33 C, and then discharged for 30 s at 4 C. The resistance at the 30-th second was calculated according to the following formula.
DCR=(Uinitial−Uend)/I
It can be learned from the characterization results in Table 1 that, as compared with the comparative examples, all examples of this application show better capacity retention rate after the batteries are stored at 60° C. for 100 days, and achieve good specific charge/discharge capacity and energy density, well meeting the market requirements for lithium-ion batteries in such aspects.
It can be learned from the characterization results in Table 2 that, as compared with the comparative examples, resistance of the batteries prepared in the examples of this application has a much lower resistance at the 30-th second. This indicates that in this application, the particle sizes of the anode active materials in the capacity layer and power layer being specially designed can effectively inhibit an increase in battery resistance caused by delithiation commonly existing in the prior art, thereby significantly improving the performance of the batteries.
In Examples 2-1 to 2-6, the lithium-ion batteries were obtained by using same steps in Examples 1-1 to 1-6 respectively, except that during preparation of the power layer, the same weight of Li2Ni0.5Cu0.5O2, instead of Li5FeO4, was used as the pre-lithiation agent.
In Comparative Example 2-1, the lithium-ion battery was obtained through the same steps in Comparative Example 1-4, except that during preparation of the power layer, the same weight of Li2Ni0.5Cu0.5O2, instead of Li5FeO4, was used as the pre-lithiation agent.
The specific charge capacity, specific discharge capacity, volumetric energy density, capacity retention ratio, and direct-current resistance of the lithium-ion batteries prepared in Examples 2-1 to 2-6 and Comparative Example 2-1 were characterized according to the foregoing steps, and summarized in Table 2. To compare the performance of the batteries more intuitively, the characterization results of the foregoing comparative examples 1-1 to 1-3 in which no pre-lithiation agent is used are also listed in Table 3.
It can be learned from the characterization results in Table 3 that, as compared with the comparative examples, after the pre-lithiation agent is replaced, all examples of this application also show significantly better capacity retention rate than the comparative examples, and also have good specific charge/discharge capacity and energy density, well meeting market requirements for lithium-ion batteries in such aspects.
It can be learned from the characterization results in Table 4 that, as compared with the comparative examples, after the pre-lithiation agent is replaced, the batteries prepared in the examples of this application also achieve a much lower direct-current resistance at the 30-th second. This indicates that the particle sizes of the anode active materials in the capacity layer and power layer being specially designed can effectively inhibit an increase in battery resistance caused by delithiation commonly existing in the prior art, thereby significantly improving the performance of the batteries.
The present application is a continuation of International Application No. PCT/CN2022/074723, filed Jan. 28, 2022, which is incorporated herein by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/CN2022/074723 | Jan 2022 | US |
| Child | 18234891 | US |
