The present application claims priority to Korean Patent Application No. 10-2021-0098381, filed Jul. 27, 2021, the entire contents of which is incorporated herein for all purposes by this reference.
The present invention relates to a non-aqueous freestanding ion conductive gel for an electrolyte of a lithium secondary battery and a method of manufacturing the same. More particularly, the present invention relates to a non-aqueous freestanding bi-continuous ion conductive gel obtained by photopolymerizing an ionic liquid and a non-aqueous microemulsion from which water is removed with the use of an ionic liquid with a surface activity, and a method of preparing the same.
Solid electrolytes can solve the stability-related problems of liquid electrolytes and suppress interfacial phenomena such as solid electrolyte interphase (SEI) and lithium dendrites that cause performance degradation at an interfacial area in an electrode. Among these solid electrolytes, a solid electrolyte obtained by adding additives and an ion accelerator to a general-purpose and high-conductivity polymer such as PEO, PAN, epoxy, or acrylate is applied to secondary batteries.
Gel-type solid polymer electrolytes are stable, but are problematic in that ionic conductivity and lithium ion transference number (t+) are low, and mechanical strength is weak.
Therefore, it is necessary to develop a technology for a solid electrolyte having high ionic conductivity, high lithium ion transference number, and excellent mechanical strength and for a method for preparing the same.
One objective of the present invention is to provide a solid electrolyte that can be used in an energy storage device due to high ionic conductivity, high lithium ion transference number, and excellent mechanical strength thereof and to provide a method of preparing the same solid electrolyte.
Another objective of the present invention is to provide a microemulsion that is actually applicable to a lithium secondary battery because water is not used and to provide a non-aqueous freestanding ion conductive gel using the same.
In one aspect of the present invention, there is provided a non-aqueous freestanding ion conductive gel including: a matrix including a hydrophobic polymer formed through polymerization of monomers having an unsaturated double-bond; a domain dispersed in the matrix and including a hydrophilic ionic liquid; and a surface active layer including an ionic liquid having surface activity, in which a portion of a hydrophobic segment in a chain of the ionic liquid having surface activity is positioned in the matrix, and a portion of a hydrophilic segment in the chain is positioned in the domain.
In addition, the non-aqueous freestanding ion conductive gel may have a bi-continuous structure in which the matrix is a continuous phase and the domain is also a continuous phase.
In addition, the domain may form an ion channel.
In addition, the thickness of the ion channel may be controlled by adjusting the content of the ionic liquid having the surface activity.
In addition, the domain may further include a lithium salt.
In addition, the lithium salt may include at least one selected from the group consisting of lithium bistrifluoromethanesulfonylimide (LiN(CF3SO2)2, LiTFSI), lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bisfluorosulfonylimide (Li(FSO2)2N), LiFSI), lithium triflate (LiCF3SO3) lithium difluoro(bis(oxalato))phosphate (LiPF2 (C2O4)2)r lithium tetrafluoro(oxalato)phosphate (LiPF4 (C2O4)), lithium difluoro(oxalato)borate (LiBF2 (C2O4)), and lithium bis(oxalato)borate (LiB(C2O4)2).
In addition, the monomer including an unsaturated double bond may be one represented by Structural Formula 1 below.
In Structural Formula 1,
R1 is a C3-C20 linear or branched alkylene group or a C6-C30 arylene group, and
R2 is each independently a hydrogen atom or a C1-C3 linear or branched alkyl group.
In addition, the ionic liquid having surface activity may include an alkyl group having 8 or more carbon atoms in a chain thereof.
In addition, the ionic liquid having surface activity may include at least one selected from the group consisting of an imidazolium-based ionic liquid, pyridinium-based ionic liquid, a piperidinium-based ionic liquid, a pyrrolidinium-based ionic liquid, an ammonium-based ionic liquid, a phosphonium-based ionic liquid, and a sulfonium-based ionic liquid.
In addition, the hydrophilic ionic liquid may include an alkyl group having 5 or less carbon atoms in a chain thereof.
In addition, the hydrophilic ionic liquid may include at least one selected from the group consisting of an imidazolium-based ionic liquid, a pyridinium-based ionic liquid, a piperidinium-based ionic liquid, a pyrrolidinium-based ionic liquid, an ammonium-based ionic liquid, a phosphonium-based ionic liquid, and a sulfonium-based ionic liquid.
In addition, the non-aqueous freestanding ion conductive gel may have a thickness of 20 to 200 μm.
In another aspect of the present invention, there is provided an energy storage device including the non-aqueous freestanding ion conductive gel.
In addition, the energy storage device may be any one selected from the group consisting of a transistor, a super capacitor, and a lithium secondary battery.
In addition, the energy storage device may be a lithium secondary battery, and the non-aqueous freestanding ion gel may be used as any one selected from the group consisting of a separator and an electrolyte of a lithium secondary battery.
In a further aspect of the present invention, there is provided a method of preparing a non-aqueous freestanding ion conductive gel, the method including: (a) preparing a microemulsion including a hydrophilic ionic liquid, a monomer having an unsaturated double bond, and a photoinitiator; and (b) photopolymerizing the microemulsion to produce a non-aqueous freestanding ionic liquid gel.
The microemulsion may include 100 parts by weight of the hydrophilic ionic liquid; 10 to 80 parts by weight of the monomer having an unsaturated double bond; and 10 to 50 parts by weight of the ionic liquid having surface activity.
In addition, the microemulsion may contain 0.1 to 1 part by weight of the photoinitiator per 100 parts by weight of the monomer having an unsaturated double bond.
In addition, the non-aqueous freestanding ion conductive gel preparation method may further include, before (a), (a′) preparing a mixture by mixing the hydrophilic ionic liquid with a lithium salt, in which (a) may be a step of preparing the microemulsion containing the mixture, the monomer having an unsaturated double bond, the ionic liquid having surface activity, and the photoinitiator.
In addition, the lithium salt may have a molar concentration of 0.1 to 10 M with respect to the sum of the hydrophilic ionic liquid and the lithium salt.
In addition, before (b), the non-aqueous freestanding ion conductive gel preparation method may further include (b′) injecting the microemulsion into a glass mold.
The non-aqueous freestanding ion conductive gel of the present invention has high ionic conductivity, high lithium ion transference number, and high mechanical strength because an ion conductive region (domain) and a support region (matrix) having mechanical strength are continuously present in an interconnected state.
In addition, the non-aqueous freestanding ion conductive gel of the present invention is actually applicable to a lithium secondary battery because it is prepared from a microemulsion that does not contain water.
In addition, the non-aqueous freestanding ion conductive gel of the present invention can be used for various energy storage devices.
Since the accompanying drawings are for reference in describing exemplary embodiments of the present invention, the technical spirit of the present invention should not be construed as being limited to the accompanying drawings.
Herein after, examples of the present invention will be described in detail with reference to the accompanying drawings in such a manner that the ordinarily skilled in the art can easily implement the present invention.
The description given below is not intended to limit the present invention to specific embodiments. In relation to describing the present invention, when the detailed description of the relevant known technology is determined to unnecessarily obscure the gist of the present invention, the detailed description may be omitted.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention. As used herein, the singular forms “a”, “an”, and “the” are intended to include the plural forms as well unless the context clearly indicates otherwise. It will be further understood that the terms “comprise” or “have” when used in this specification specify the presence of stated features, integers, steps, operations, elements and/or combinations thereof, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, and/or combinations thereof.
Terms including ordinal numbers used in the specification, “first”, “second”, etc. can be used to discriminate one component from another component, but the order or priority of the components is not limited by the terms unless specifically stated. These teams are used only for the purpose of distinguishing a component from another component. For example, without departing from the scope of the present invention, a first component may be referred as a second component, and a second component may be also referred to as a first component.
In addition, when it is mentioned that a component is “famed” or “stacked” on another component, it should be understood such that one component may be directly attached to or directly stacked on the front surface or one surface of the other component, or an additional component may be disposed between them.
Hereinafter, a non-aqueous freestanding ion conductive gel for application to an electrolyte of a lithium secondary battery and a manufacturing method thereof according to the present invention will be described in detail. However, those are described as examples, and the present invention is not limited thereto and is only defined by the scope of the appended claims.
Referring to
In addition, the non-aqueous freestanding ion conductive gel may have a bi-continuous structure in which the matrix is a continuous phase and the domain is also a continuous phase.
In addition, the domain may form an ion channel, and the thickness of the ion channel may be controlled depending on the content of the ionic liquid having surface activity.
In addition, the domain may further include a lithium salt.
In addition, the lithium salt may include at least one selected from the group consisting of lithium bistrifluoromethanesulfonylimide (LiN(CF3SO2)2, LiTFSI), lithium perchlorate (LiClO4), lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bisfluorosulfonylimide (Li(FSO2)2N), LiFSI), lithium triflate (LiCF3SO3) lithium difluoro(bis(oxalato))phosphate (LiPF2 (C2O4)2)r lithium tetrafluoro(oxalato)phosphate (LiPF4 (C2O4)), lithium difluoro(oxalato)borate (LiBF2 (C2O4)), and lithium bis(oxalato)borate (LiB(C2O4)2). Preferably, the lithium salt includes lithium bistrifluoromethanesulfonylimide (LiN(CF3SO2)2, LiTFSI).
In addition, the monomer including an unsaturated double bond may be one represented by Structural Formula 1 below.
In Structural Formula 1,
R1 is a C3-C20 linear or branched alkylene group or a C6-C30 arylene group, and
R2 is each independently a hydrogen atom or a C1-C3 linear or branched alkyl group.
Preferably, in Structural Formula 1, R1 is a C6-C18 alkylene group or a C6-C20 arylene group.
More preferably, the monomer including an unsaturated double bond may include 1,12-dodecanediol dimethacrylate.
In addition, the ionic liquid having surface activity may include an alkyl group having 8 or more carbon atoms in a chain thereof.
In addition, the ionic liquid having surface activity may include at least one selected from the group consisting of an imidazolium-based ionic liquid, a pyridinium-based ionic liquid, a piperidinium-based ionic liquid, a pyrrolidinium-based ionic liquid, an ammonium-based ionic liquid, a phosphonium-based ionic liquid, and a sulfonium-based ionic liquid.
The imidazolium-based ionic liquid includes, as cations, at least one selected from the group consisting of 1-methyl-3-octylimidazolium, 1-octyl-2,3-dimethylimidazolium, 1-decyl-3-methylimidazolium, 1-dodecyl-3-methylimidazolium, 1-tetradecyl-3-methylimidazolium, and 1-hexadecyl-3-methylimidazolium, and includes, as anions, at least one selected from the group consisting of chloride, bromide, iodide, hexafluorophosphate, tetrafluoroborate, hexafluoroantimonate, trifluoromethanesulfonate, methylsulfate, ethylsulfate, acetate, thiocyanate, dicyanamide and bis(trifluromethylsulfonyl)imide.
The pyridinium-based ionic liquid includes, as cations, at least one selected from the group consisting of 1-methyl octylpyridinium, 1-octyl-2,3-dimethylpyridinium, 1-decyl methylpyridinium, 1-dodecyl-3-methylpyridinium, 1-tetradecyl methylpyridinium, and 1-hexadecyl-3-methylpyridinium, and includes, as anions, at least one selected from the group consisting of chloride, bromide, iodide, hexafluorophosphate, tetrafluoroborate, hexafluoroantimonate, trifluoromethanesulfonate, methylsulfate, ethylsulfate, acetate, thiocyanate, dicyanamide, and bis(trifluromethylsulfonyl)imid.
The piperidinium-based ionic liquid includes, as cations, at least one selected from the group consisting of 1-methyl-3-octylpiperidinium, 1-octyl-2,3-dimethylpiperidinium, 1-decyl-3-methylpiperidinium, 1-dodecyl-3-methylpiperidinium, 1-tetradecyl-3-methylpiperidinium, and 1-hexadecyl-3-methylpiperidinium, and includes, as anions, at least one selected from the group consisting of chloride, bromide, iodide, hexafluorophosphate, tetrafluoroborate, hexafluoroantimonate, trifluoromethanesulfonate, methylsulfate, ethylsulfate, acetate, thiocyanate, dicyanamide, and bis(trifluromethylsulfonyl)imide.
The pyrrolidinium-based ionic liquid includes, as cations, at least one selected from the group consisting of 1-methyl-3-octylpyrrolidinium, 1-octyl-2,3-dimethylpyrrolidinium, 1-decyl-3-methylpyrrolidinium, 1-dodecyl-3-methylpyrrolidinium, 1-tetradecyl-3-methylpyrrolidinium, and 1-hexadecyl methylpyrrolidinium, and includes, as anions, at least one selected from the group consisting of chloride, bromide, iodide, hexafluorophosphate, tetrafluoroborate, hexafluoroantimonate, trifluoromethanesulfonate, methylsulfate, ethylsulfate, acetate, thiocyanate, dicyanamide, and bis(trifluromethylsulfonyl)imide.
The ammonium-based ionic liquid includes, as cations, at least one selected from the group consisting of 1-methyl-3-octylammonium, 1-octyl-2,3-dimethylammonium, 1-decyl-3-methylammonium, 1-dodecyl-3-methylammonium, 1-tetradecyl-3-methylammonium, and 1-hexadecyl-3-methylammonium, and includes, as anions, at least one selected from the group consisting of chloride, bromide, iodide, hexafluorophosphate, tetrafluoroborate, hexafluoroantimonate, trifluoromethanesulfonate, methylsulfate, ethylsulfate, acetate, thiocyanate, dicyanamide, and bis(trifluromethylsulfonyl)imid.
The phosphonium-based ionic liquid includes, as cations, at least one selected from the group consisting of 1-methyl-3-octylphosphonium, 1-octyl-2,3-dimethylphosphonium, 1-decyl-3-methylphosphonium, 1-dodecyl-3-methylphosphonium, 1-tetradecyl-3-methylphosphonium, and 1-hexadecyl-3-methylphosphonium, and includes, as anions, at least one selected from the group consisting of chloride, bromide, iodide, hexafluorophosphate, tetrafluoroborate, hexafluoroantimonate, trifluoromethanesulfonate, methylsulfate, ethylsulfate, acetate, thiocyanate, dicyanamide, and bis(trifluromethylsulfonyl)imide.
The sulfonium-based ionic liquid includes, as cations, at least one selected from the group consisting of 1-methyl octylsulfonium, 1-octyl-2,3-dimethylsulfonium, 1-decyl methylsulfonium, 1-dodecyl-3-methylsulfonium, 1-tetradecyl-3-methylsulfonium, and 1-hexadecyl-3-methylsulfonium, and includes, as anions, at least one selected from the group consisting of chloride, bromide, iodide, hexafluorophosphate, tetrafluoroborate, hexafluoroantimonate, trifluoromethanesulfonate, methylsulfate, ethylsulfate, acetate, thiocyanate, dicyanamide, and bis(trifluromethylsulfonyl)imide.
In addition, the hydrophilic ionic liquid may include an alkyl group having 5 or less carbon atoms.
In addition, the hydrophilic ionic liquid may include at least one selected from the group consisting of an imidazolium-based ionic liquid, a pyridinium-based ionic liquid, a piperidinium-based ionic liquid, a pyrrolidinium-based ionic liquid, an ammonium-based ionic liquid, a phosphonium-based ionic liquid, and a sulfonium-based ionic liquid.
The imidazolium-based ionic liquid includes, as cations, at least one selected from the group consisting of 1-methyl ethylimidazolium, 1-ethyl-2,3-dimethylimidazolium, 1-butyl methylimidazolium, 1-pentyl-3-methylimidazolium, and 1-pentyl-3-ethylimidazolium, and includes, as anions, at least one selected from the group consisting of chloride, bromide, iodide, hexafluorophosphate, tetrafluoroborate, hexafluoroantimonate, trifluoromethanesulfonate, methylsulfate, ethylsulfate, acetate, thiocyanate, dicyanamide, and bis(trifluromethylsulfonyl)imide.
The pyridinium-based ionic liquid includes, as cations, at least one selected from the group consisting of 1-methyl-3-ethylpyridinium, 1-ethyl-2,3-dimethylpyridinium, 1-butyl-3-methylpyridinium, 1-pentyl-3-methylpyridinium, and 1-pentyl-3-ethylpyridinium, and includes, as anions, at least one selected from the group consisting of chloride, bromide, iodide, hexafluorophosphate, tetrafluoroborate, hexafluoroantimonate, trifluoromethanesulfonate, methylsulfate, ethylsulfate, acetate, thiocyanate, dicyanamide, and bis(trifluromethylsulfonyl)imid.
The piperidinium-based ionic liquid includes, as cations, at least one selected from the group consisting of 1-methyl-3-ethylpiperidinium, 1-ethyl-2,3-dimethylpiperidinium, 1-butyl-3-methylpiperidinium, 1-pentyl-3-methylpiperidinium, and 1-pentyl-3-ethylpiperidinium, and includes, as anions, at least one selected from the group consisting of chloride, bromide, iodide, hexafluorophosphate, tetrafluoroborate, hexafluoroantimonate, trifluoromethanesulfonate, methylsulfate, ethylsulfate, acetate, thiocyanate, dicyanamide, and bis(trifluromethylsulfonyl)imide.
The pyrrolidinium-based ionic liquid includes, as cations, at least one selected from the group consisting of 1-methyl ethylpyrrolidinium, 1-ethyl-2,3-dimethylpyrrolidinium, 1-butyl-3-methylpyrrolidinium, 1-pentyl-3-methylpyrrolidinium, and 1-pentyl-3-ethylpyrrolidinium, and includes, as anions, at least one selected from the group consisting of chloride, bromide, iodide, hexafluorophosphate, tetrafluoroborate, hexafluoroantimonate, trifluoromethanesulfonate, methylsulfate, ethylsulfate, acetate, thiocyanate, dicyanamide, and bis(trifluromethylsulfonyl)imide.
The ammonium-based ionic liquid includes, as cations, at least one selected from the group consisting of 1-methyl-3-ethylammonium, 1-ethyl-2,3-dimethylammonium, 1-butyl-3-methylammonium, 1-pentyl-3-methylammonium, and 1-pentyl-3-ethylammonium, and includes, as anions, at least one selected from the group consisting of chloride, bromide, iodide, hexafluorophosphate, tetrafluoroborate, hexafluoroantimonate, trifluoromethanesulfonate, methylsulfate, ethylsulfate, acetate, thiocyanate, dicyanamide, and bis(trifluromethylsulfonyl)imid.
The phosphonium-based ionic liquid includes, as cations, at least one selected from the group consisting of 1-methyl ethylphosphnium, 1-ethyl-2,3-dimethylphosphnium, 1-butyl methylphosphnium, 1-pentyl-3-methylphosphnium, and 1-pentyl ethylphosphnium, and includes, as anions, at least one selected from the group consisting of chloride, bromide, iodide, hexafluorophosphate, tetrafluoroborate, hexafluoroantimonate, trifluoromethanesulfonate, methylsulfate, ethylsulfate, acetate, thiocyanate, dicyanamide, and bis(trifluromethylsulfonyl)imide.
The sulfonium-based ionic liquid includes, as cations, at least one selected from the group consisting of 1-methyl-3-ethylsulfonium, 1-ethyl-2,3-dimethylsulfonium, 1-butyl-3-methylsulfonium, 1-pentyl-3-methylsulfonium, and 1-pentyl-3-ethylsulfonium, and includes, as anions, at least one selected from the group consisting of chloride, bromide, iodide, hexafluorophosphate, tetrafluoroborate, hexafluoroantimonate, trifluoromethanesulfonate, methylsulfate, ethylsulfate, acetate, thiocyanate, dicyanamide, and bis(trifluromethylsulfonyl)imide.
In addition, the non-aqueous freestanding ion conductive gel may have a thickness of 20 to 200 μm and preferably a thickness of 130 to 160 μm. When the thickness is smaller than 20 μm, it is not preferable because it is too thin to have sufficient mechanical strength. When the thickness exceeds 200 μm, it is not preferable because the ion conductivity decreases as the moving distance increases.
The present invention provides an energy storage device including the non-aqueous freestanding ion conductive gel.
In addition, the energy storage device may be any one selected from the group consisting of a transistor, a super capacitor, and a lithium secondary battery.
In addition, the energy storage device may be a lithium secondary battery, and the non-aqueous freestanding ion gel may be used as any one selected from the group consisting of a separator and an electrolyte of a lithium secondary battery.
The present invention provides a method of preparing a non-aqueous freestanding ion conductive gel, the method including: (a) preparing a microemulsion including a hydrophilic ionic liquid, monomer having an unsaturated double bond, and a photoinitiator; and (b) photopolymerizing the microemulsion to produce a non-aqueous freestanding ionic liquid gel.
The microemulsion may include 100 parts by weight of the hydrophilic ionic liquid; 10 to 80 parts by weight of the monomer having an unsaturated double bond; and 10 to 50 parts by weight of the ionic liquid having surface activity.
Specifically, the microemulsion may include 10 to 80 parts by weight of the monomer having an unsaturated double bond and preferably 30 parts by weight of the monomer having an unsaturated double bond per 100 parts by weight of the hydrophilic ionic liquid. When the amount of the monomer having an unsaturated double bond is smaller than 30 parts by weight, the mechanical strength of the non-aqueous freestanding ion conductive gel is weak, so that when applied to a lithium secondary battery, lithium dendrites causes a short circuit, which is not preferable. When the amount exceeds 80 parts by weight, the ionic conductivity of the non-aqueous freestanding ion conductive gel is insufficient, which is not preferable.
Specifically, the microemulsion may include 10 to 50 parts by weight of the ionic liquid having surface activity and preferably 10 to 30 parts by weight of the ionic liquid having surface activity, per 100 parts by weight of the hydrophilic ionic liquid. When the amount of the ionic liquid having surface activity is less than 10 parts by weight, the microemulsion is not formed and the two immiscible liquids are present separately, which is not preferable because ion channels are not famed. When the amount exceeds 50 parts by weight, it is undesirable because the ionic liquid having surface activity cannot be completely dissolved because the amount is excessive.
In addition, the microemulsion may contain 0.1 to 1 part by weight of the photoinitiator per 100 parts by weight of the monomer having an unsaturated double bond. When the amount of the photoinitiator is less than 0.1 part by weight, it is not preferable because a non-aqueous freestanding ion conductive gel is not formed from the microemulsion. When the amount exceeds 1 part by weight, photopolymerization occurs excessively, thereby increasing crosslinking density and decreasing ionic conductivity, which are not preferable.
The non-aqueous freestanding ion conductive gel preparation method may further include, before (a), (a′) preparing a mixture by mixing the hydrophilic ionic liquid with a lithium salt, in which (a) may be a step of preparing the microemulsion containing the mixture, the monomer having an unsaturated double bond, the ionic liquid having surface activity, and the photoinitiator
In addition, the molar concentration of the lithium salt with respect to the sum of the hydrophilic ionic liquid and the lithium salt may be in the range of 0.1 to 10 M, preferably in the range of 0.5 to 5 M, and most preferably in the range of 0.7 to 1.5 M. When the concentration of the lithium salt is lower than 0.1 M, the ionic conductivity of the non-aqueous freestanding ion conductive gel is insufficient, which is undesirable. When the concentration exceeds 10 M, an increase in the effect of the lithium salt is insignificant compared to an increase in the amount of the lithium salt used. In addition, it is not desirable because an excessive amount of the lithium salt is not dissolved.
In addition, before (b), the non-aqueous freestanding ion conductive gel preparation method may further include (b′) injecting the microemulsion into a glass mold.
Hereinafter, a preferred example of the present invention will be described. However, the example is for illustrative purposes, and the scope of the present invention is not limited thereto.
A 1M-concentration lithium solution was obtained by dissolving lithium bis(trifluoromethanesulfonyl)imide (LiTFSi) as a lithium salt in 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (C2MIM TFSi) as a hydrophilic ionic liquid.
60% by weight of C2MIM TFSi containing 1 M of lithium salt, 30% by weight of 1,12-dodecanediol dimethacrylate (C12-DMA) having an unsaturated double bond, which is a monomer, 10% by weight of 1-methyl-3-tetradecylimidazolium, which is an ionic liquid having surface activity, and 1% by weight C12-DMA, which is a photoinitiator, were mixed, and the mixture was stirred at room temperature for one day to prepare a transparent microemulsion.
The microemulsion was injected into a glass mold and photopolymerized through a light exposure machine to prepare a non-aqueous freestanding ion conductive gel (thickness: 130 to 160 μm).
A non-aqueous freestanding ion conductive gel was prepared in the same manner as in Example 1, except that 15% by weight of the ionic liquid having surface activity was used instead of 10% by weight of the ionic liquid having surface activity.
A non-aqueous freestanding ion conductive gel was prepared in the same manner as in Example 1, except that 20% by weight of the ionic liquid having surface activity was used instead of 10% by weight of the ionic liquid having surface activity.
A non-aqueous freestanding ion conductive gel was prepared in the same manner as in Example 1, except that 25% by weight of the ionic liquid having surface activity was used instead of 10% by weight of the ionic liquid having surface activity.
A non-aqueous freestanding ion conductive gel was prepared in the same manner as in Example 1, except that 30% by weight of the ionic liquid having surface activity was used instead of 10% by weight of the ionic liquid having surface activity.
A half-cell was manufactured by using the non-aqueous freestanding ion conductive gel prepared in Example 1 was used as an electrolyte, lithium iron phosphate (LFP) as a cathode material, and lithium. The LFP cathode electrode material was prepared by mixing a cathode active material (LiFePO4), a conductive material, and a binder (PVDF) at a weight ratio of 8:1:1, adding a small amount of NMP solvent to obtain a slurry, applying the slurry to an aluminum current collector, drying the resulting structure, and compressing the structure through hot pressing.
Referring to
In addition, it was confirmed that the microemulsion prepared according to the present invention was maintained in a state in which the system was not broken even for several months.
Through the small-angle X-ray scattering (SAXS) analysis using X-rays scattered at a small angle in the range of 0.001° to 5° shows the presence of a structure having a size of several to tens of nanometers. From the position, sharpness, and gradient of the peak (Q), it is possible to know structural information (form factor) and interaction (structure factor) between internal structures.
Referring to
In addition, a broad peak was detected at Q=0.16 Å−1 (38.3 Å) by comparing the SAXS analysis of each sample in the state of a microemulsion solution (liquid, before curing). Through this, it is confirmed that a solid polymer electrolyte having a bi-continuous structure was formed from a self-assembled structure of a bi-continuous microemulsion composed of an ionic liquid having surface activity, which is a solution phase.
Referring to
In detail, impedance was measured using electrochemical impedance spectroscopy (EIS), ionic conductivity was measured using Equation 1 below, and mechanical strength was measured through a tensile strength test using a universal tensile machine (UTM).
In Equation 1,
σ is ionic conductivity,
d is the thickness of an electrolyte,
R is the resistance value (impedance) of an electrolyte through EIS, and
A is the area of an electrolyte (diameter of 16 mm).
Referring to Table 1 and
In addition, the mechanical strength of the non-aqueous freestanding ion conductive gel prepared according to the example of the present invention is 0.6 to 0.8 MPa, which is similar to that of the solid polymer electrolyte. That is, the non-aqueous freestanding ion conductive gel according to the example of the present invention is higher in ionic conductivity than and is similar in mechanical strength to the solid polymer electrolyte.
Lithium ion transference numbers t+ can be found with reference to
In Equation 2,
Iss is a current value when the current is constant after polarization (steady state),
I0 is an initial current value (before polarization),
Rss is a resistance value when the current is constant after polarization,
R0 is a resistance value (before polarization), and
V is a voltage (10 mV) applied.
Referring to
Referring to Table 1 and
Referring to
Referring to
Referring to
The scope of the present invention is defined by the following claims rather than the above detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as falling into the scope of the present invention.
Number | Date | Country | Kind |
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10-2021-0098381 | Jul 2021 | KR | national |