Gel electrolyte, preparation method thereof, negative electrode, lithium battery and vehicle

Abstract

The application discloses a gel electrolyte, a preparation method thereof, a negative electrode, a lithium battery and a vehicle. The gel electrolyte comprises a lithium salt, an organic solvent and a polymer matrix; the polymer matrix comprises a polymer A and a polymer B, and the structural formula of the polymer B is as follows: Compared with a traditional liquid electrolyte, the gel electrolyte has the characteristics of weak fluidity and poor affinity of the polymer on the lithium metal negative electrode side to the electrolyte, can effectively prevent the contact between the electrolyte and the lithium metal, reduce the consumption of the electrolyte and active lithium, is favorable to promoting the uniform distribution of lithium ions, making the lithium ions uniformly deposit and inhibiting the generation of lithium dendrites, and further improves the cycle life of the battery.

Description

TECHNICAL FIELD

[0001] The present application generally relates to the technical field of lithium battery, and in particular to a gel electrolyte, a preparation method thereof, a negative electrode, a lithium battery and a vehicle. BACKGROUND

[0002] With the wide application of intelligent electronic devices, electric vehicles and large energy storage devices, there is an urgent need for lithium secondary batteries with higher energy density and cycle life. Lithium metal has a high theoretical specific capacity (3860 mAh / g) and a low electrochemical potential (-3.040 V vs. standard hydrogen electrode), and is considered to be the most ideal negative electrode material for the next generation of lithium secondary batteries.

[0003] Currently, lithium metal negative electrodes mainly include the following two problems: (1) lithium ions are prone to non-uniform deposition, resulting in lithium dendrites, which leads to battery short circuit; (2) lithium dendrites have a large specific surface area and high activity, and are prone to react with electrolyte, continuously consuming electrolyte and active lithium, resulting in poor cycle performance and short service life of the battery. The liquid electrolyte in the existing traditional lithium secondary battery has good fluidity, is prone to contact reaction with lithium metal, and thus cannot avoid the above problems of lithium negative electrode. SUMMARY

[0004] In view of the above defects or deficiencies in the prior art, it is desirable to provide a gel electrolyte, a preparation method thereof, a negative electrode, a lithium battery and a vehicle, which has weak fluidity, can prevent the gel electrolyte from contacting with lithium metal, reduces the consumption of lithium metal and gel electrolyte, and at the same time makes lithium ions uniformly distributed and inhibits the generation of lithium dendrites.

[0005] In a first aspect, the present application provides a gel electrolyte, comprising a lithium salt, an organic solvent and a polymer matrix; the polymer matrix comprises a polymer A and a polymer B, and the structural formula of the polymer B is as follows:

[0006]

[0007] wherein R1 is selected from one of hydrogen, halogen, a substituted or unsubstituted C1-C6 alkyl group;

[0008] R2 is selected from a substituted or unsubstituted C0-C6 methylene group, a substituted or unsubstituted C6-C 12 aryl group, a substituted or unsubstituted C6-C 12 cycloalkyl group, a substituted or unsubstituted C2-C 10 alkyl group containing a heteroatom, wherein M is a substituted or unsubstituted C0-C6 methylene group, a substituted or unsubstituted phenyl group, a substituted or unsubstituted cyclohexane group, a substituted or unsubstituted C2-C 10C1-C6 alkyl;

[0009] m is any integer between 1 and 50; n is any integer between 2 and 100000.

[0010] As an optional solution, the substituent is selected from halogen, hydroxyl, amine group, carboxyl, carbonyl, cyano, sulfonic acid group, C1-C6 alkoxy, C1-C6 alkyl, C6-C12 aryl, or C6-C12 cycloalkyl. 12 C6-C12 aryl, or C6-C12 cycloalkyl. 12 C6-C12 aryl, or C6-C12 cycloalkyl.

[0011] As an optional solution, the halogen is selected from one of fluorine, chlorine, and bromine; the amine group is selected from C1-C6 primary amine, C1-C6 alkyl-substituted secondary amine, or tertiary amine; the C1-C6 alkoxy is selected from methoxy or ethoxy; the C1-C6 alkyl is selected from methyl, ethyl, propyl, isopropyl, butyl, or tert-butyl; the C6-C12 aryl is selected from phenyl, naphthyl, or biphenyl; and the C6-C12 cycloalkyl is selected from cyclohexyl or bicyclohexyl. 12 C6-C12 aryl, or C6-C12 cycloalkyl.

[0012] As an optional solution, the polymer A is any at least one polymer having an affinity for organic solvents and lithium salts.

[0013] As an optional solution, the polymer A is selected from at least one of polyethylene oxide, poly(ethylene oxide-co-styrene), poly(ethylene oxide-co-propylene oxide), poly(ethylene oxide-co-ethylene), poly(vinylidene fluoride), poly(vinylidene fluoride-co-hexafluoropropylene), poly(methyl acrylate), poly(methyl methacrylate), poly(methyl methacrylate-co-butyl methacrylate), poly(ethylene carbonate), poly(propylene carbonate), poly(propylene fluorocarbonate), and polyvinylpyrrolidone.

[0014] As an optional solution, the polymer A is selected from at least one of polyethylene oxide, poly(ethylene oxide-co-styrene), poly(ethylene oxide-co-propylene oxide), poly(ethylene oxide-co-ethylene), poly(vinylidene fluoride), poly(vinylidene fluoride-co-hexafluoropropylene), poly(methyl acrylate), poly(methyl methacrylate), poly(methyl methacrylate-co-butyl methacrylate), poly(ethylene carbonate), poly(propylene carbonate), poly(propylene fluorocarbonate), and polyvinylpyrrolidone.

[0015] As an optional solution, the polymer matrix accounts for 10% to 70% of the total mass of the gel electrolyte; the organic solvent accounts for 5% to 50% of the total mass of the gel electrolyte; and the lithium salt accounts for 25% to 40% of the total mass of the gel electrolyte.

[0016] As an optional solution, the lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, and lithium perchlorate.

[0017] As an optional solution, the organic solvent is at least one of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol ethyl methyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol ethyl methyl ether, butanediol dimethyl ether, butanediol diethyl ether, butanediol ethyl methyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol dimethyl ether, tetrapropylene glycol dimethyl ether, dipropylene glycol diethyl ether, tripropylene glycol diethyl ether, tetrapropylene glycol diethyl ether, dibutanediol dimethyl ether, tributanediol dimethyl ether, tetrabutanediol dimethyl ether, dibutanediol diethyl ether, tributanediol diethyl ether, tetrabutanediol diethyl ether, 1,3-dioxolane, 1,4-dioxane, tetrahydrofuran, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 2,2,3,3,4,4,5,5-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, propylene carbonate, ethylene carbonate, diethyl carbonate, or dimethyl carbonate.

[0018] In a second aspect, the present application provides a preparation method of the gel electrolyte of the first aspect, comprising the following processes:

[0019] After the polymer A is dissolved in the solvent, the film is coated on a mold;

[0020] The monomer of the polymer B, the solvent, and the initiator are mixed uniformly to obtain a mixed solution I, the mixed solution I is coated on the surface of the film, and the polymer matrix is obtained by heating or light polymerization and drying;

[0021] The organic solvent and the lithium salt are mixed to obtain a mixed solution II, and the polymer matrix is soaked in the mixed solution II to obtain the gel electrolyte.

[0022] As an optional solution, the thickness of the film is 10-100 μm, and the thickness of the mixed solution I after coating and drying is 0.2-10 μm.

[0023] As an optional solution, the solvent is at least one of tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, diethyl ether, diisopropyl ether, dibutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol ethyl methyl ether, acetone, butanone, ethyl acetate, butyl acetate, ethyl propionate, butyl propionate, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methyl pyrrolidone.

[0024] As an optional solution, the initiator is at least one of azobisisobutyronitrile, azobisisoheptyl nitrile, benzoyl peroxide, lauroyl peroxide, butyl benzoyl peroxide, methyl ethyl ketone peroxide, benzoin dimethyl ether, methyl 4-methylbenzoylbenzoate, 4-phenyl dimethyl ketone, and 2,4,6-trimethyl benzoyl phosphine ethyl ester.

[0025] As an optional solution, the soaking time of the polymer matrix in the mixed solution II is 0.5-12h.

[0026] In a third aspect, the present application provides a negative electrode of a lithium battery, comprising a negative electrode current collector and a negative electrode active material layer on the surface of the negative electrode current collector, the surface of the negative electrode active material layer having an interface protection film, the interface protection film being obtained by formation of the gel electrolyte according to the first aspect.

[0027] In a fourth aspect, the present application provides a lithium battery, comprising the gel electrolyte of the first aspect and / or the negative electrode of the third aspect.

[0028] In a fifth aspect, the present application provides a vehicle, comprising the lithium battery of the fourth aspect.

[0029] The polymer matrix of the gel electrolyte of the present application comprises polymer A and polymer B, wherein polymer A has a large affinity for organic solvents and lithium salts and can dissolve and disperse organic solvents and lithium salts; polymer B can conduct lithium ions but has no affinity for organic solvents, and polymer A and polymer B form a heterogeneous structure. Therefore, the polymer matrix is beneficial to prevent the contact between the electrolyte and lithium metal and reduce the consumption of the electrolyte and active lithium; at the same time, it can make the lithium ions uniformly distributed, so that the lithium ions are uniformly deposited and the generation of lithium dendrites is inhibited, thereby effectively improving the cycle life. DETAILED DESCRIPTION

[0030] The present application will be further described in detail below with reference to the embodiments. It can be understood that the specific embodiments described herein are only used to explain the related application, but not to limit the application. In addition, it should be noted that only the parts related to the application are shown in the embodiments for the convenience of description.

[0031] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the embodiments.

[0032] The gel electrolyte provided by the embodiments of the present application comprises a lithium salt, an organic solvent and a polymer matrix; the polymer matrix comprises polymer A and polymer B, and the structural formula of polymer B is as follows:

[0033]

[0034] wherein R1 is selected from one of hydrogen, halogen, a substituted or unsubstituted C1-C6 alkyl group;

[0035] R2 is selected from a substituted or unsubstituted C0-C6 methylene group, a substituted or unsubstituted C6-C 12 aryl group, and a substituted or unsubstituted C6-C 12Cycloalkyl, substituent-substituted or unsubstituted heteroatom-containing C2-C 10 alkyl, Wherein, M is a C0-C6 methylene group (substituted or unsubstituted), a phenyl group (substituted or unsubstituted), a cyclohexyl group (substituted or unsubstituted), or a C2-C group (substituted or unsubstituted) containing a heteroatom. 10 Alkyl groups;

[0036] m is any integer between 1 and 50; n is any integer between 2 and 100000.

[0037] It should be noted that polymer A has a strong affinity for organic solvents and lithium salts, and can dissolve and disperse them; polymer B can conduct lithium ions, resulting in uniform lithium ion dispersion, but polymer B has no affinity for organic solvents. Polymer A and polymer B form a heterostructure, meaning that polymer A and polymer B are independent of each other and only cross-fused at the interface.

[0038] The polymer matrix, through the combined action of polymer A and polymer B, reduces the fluidity of the electrolyte, effectively preventing contact between the electrolyte and lithium metal, and reducing the consumption of electrolyte and active lithium. At the same time, it can also effectively conduct lithium ions, resulting in uniform lithium ion distribution and uniform lithium ion deposition, which is beneficial for suppressing the formation of lithium dendrites.

[0039] Polymer A can be any existing polymer used to prepare gel electrolytes, and it has an affinity for organic solvents and lithium salts. This application does not limit the specific substances.

[0040] Polymer B can be obtained by polymerization of monomers containing fluoroethoxy groups. The fluoroethoxy groups can effectively conduct lithium ions, but they have no affinity for organic solvents. By controlling the R1 and R2 groups in polymer B, the proportion of fluoroethoxy groups in the entire repeating unit can be adjusted, thus effectively hindering the contact between organic solvents and lithium metal. Furthermore, by controlling the values ​​of m and n, the proportion of fluoroethoxy groups in the entire polymer can be changed, further hindering the contact between organic solvents and lithium metal, and simultaneously improving lithium ion conductivity, thus optimizing electrolyte performance.

[0041] The polymer matrix of the gel electrolyte of the embodiments of the present application comprises polymer A and polymer B, wherein polymer A has a large affinity for organic solvents and lithium salts and can dissolve and disperse organic solvents and lithium salts; polymer B can conduct lithium ions but has no affinity for organic solvents, and polymer A and polymer B form a heterogeneous structure. Therefore, the polymer matrix is beneficial to prevent the contact between the electrolyte and lithium metal, reduce the consumption of the electrolyte and active lithium; at the same time, can make the lithium ions uniformly distributed, make the lithium ions uniformly deposited, inhibit the generation of lithium dendrites, and thus effectively improve the cycle life.

[0042] Further, the substituent is selected from halogen, hydroxyl, amine group, carboxyl, carbonyl, cyano, sulfonic acid group, C1-C6 alkoxy, C1-C6 alkyl, C6-C 12 aryl, or C6-C 12 cycloalkyl. The substituent is beneficial to improve the lithium ion conductivity and viscosity of the gel electrolyte, reduce the flowability of the electrolyte, reduce the consumption of the electrolyte and active lithium, at the same time, make the lithium ions uniformly distributed, is beneficial to the uniform deposition of lithium ions, and inhibit the generation of lithium dendrites.

[0043] In a preferred embodiment, the halogen is selected from one of fluorine, chlorine, and bromine; the amine group is selected from C1-C6 primary amine, C1-C6 alkyl-substituted secondary amine, or tertiary amine; the C1-C6 alkoxy is selected from methoxy or ethoxy; the C1-C6 alkyl is selected from methyl, ethyl, propyl, isopropyl, butyl, or tert-butyl; the C6-C 12 aryl is selected from phenyl, naphthyl, or biphenyl; and the C6-C 12 cycloalkyl is selected from cyclohexyl or bicyclohexyl.

[0044] Further, polymer A is any at least one polymer having an affinity for organic solvents and lithium salts. In a specific embodiment, polymer A is selected from at least one of polyethylene oxide, ethylene oxide-styrene copolymer, ethylene oxide-propylene oxide copolymer, ethylene oxide-ethylene copolymer, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polymethyl acrylate, polymethyl methacrylate, methyl methacrylate-butyl methacrylate copolymer, polyvinyl carbonate, polypropylene carbonate, polyfluorinated propylene carbonate, and polypyrrolidone.

[0045] In other embodiments, the polymer A can also be selected from at least any two monomers of polymers of poly(ethylene oxide), poly(ethylene oxide-co-styrene), poly(ethylene oxide-co-propylene oxide), poly(ethylene oxide-co-ethylene), poly(vinylidene fluoride), poly(vinylidene fluoride-co-hexafluoropropylene), poly(methyl acrylate), poly(methyl methacrylate), poly(methyl methacrylate-co-butyl methacrylate), poly(ethylene carbonate), poly(propylene carbonate), poly(propylene fluorocarbonate), poly(pyrrolidone). For example, polymers of ethylene oxide and poly(ethylene oxide-co-styrene); polymers of methyl acrylate and poly(methyl methacrylate-co-butyl methacrylate), etc.

[0046] Further, the polymer matrix accounts for 10% to 70% of the total mass of the gel electrolyte; the organic solvent accounts for 5% to 50% of the total mass of the gel electrolyte; and the lithium salt accounts for 25% to 40% of the total mass of the gel electrolyte. The content of the polymer matrix in the present embodiment is advantageous to make the electrolyte have suitable flowability, to avoid the contact between the electrolyte and the lithium metal while ensuring reliable transmission and uniform distribution of lithium ions.

[0047] Further, the lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium difluoro(oxalato)borate, lithium bis(oxalato)borate, and lithium perchlorate.

[0048] Further, the organic solvent is selected from at least one of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol monoethyl ether, butylene glycol dimethyl ether, butylene glycol diethyl ether, butylene glycol monoethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol dimethyl ether, tetrapropylene glycol dimethyl ether, dipropylene glycol diethyl ether, tripropylene glycol diethyl ether, tetrapropylene glycol diethyl ether, dibutylene glycol dimethyl ether, tributylene glycol dimethyl ether, tetrabutylene glycol dimethyl ether, dibutylene glycol diethyl ether, tributylene glycol diethyl ether, tetrabutylene glycol diethyl ether, 1,3-dioxolane, 1,4-dioxane, tetrahydrofuran, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 2,2,3,3,4,4,5,5-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, propylene carbonate, ethylene carbonate, diethyl carbonate, or dimethyl carbonate.

[0049] Further, the molecular weight of the polymer B is in the range of 50,000 to 500,000.

[0050] In summary, the gel electrolyte of the present embodiment is advantageous to prevent the contact between the electrolyte and the lithium metal and reduce the consumption of the electrolyte and active lithium; at the same time, it can make the lithium ions uniformly distributed and deposited, inhibit the generation of lithium dendrites, and effectively improve the cycle life.

[0051] Furthermore, by adjusting the chain length of polymer B and the R group, it is beneficial to optimize the performance of the electrolyte.

[0052] In a second aspect, the present invention provides a method for preparing a gel electrolyte according to the first aspect, comprising the following steps:

[0053] After polymer A is dissolved in a solvent, it is coated onto a mold to form a film. The mold can be any type of mold that is resistant to high temperature, organic solvents, and light, and is not specifically limited in this embodiment.

[0054] The monomer, solvent, and initiator of polymer B are mixed evenly to obtain mixture I. Mixture I is coated on the surface of a film, and polymerization is carried out by heating or light irradiation, followed by drying to obtain a polymer matrix. The heating temperature can be any temperature within the safe operating range as long as it can initiate monomer polymerization, prevent polymer A from decomposing, and is safe to operate. The light irradiation can be ultraviolet light, such as 200-400nm ultraviolet light, and this embodiment does not make specific limitations on it.

[0055] An organic solvent and a lithium salt are mixed to obtain mixture II. The polymer matrix is ​​then immersed in mixture II to obtain a gel electrolyte. The concentration of mixture II ranges from 0.5 to 10 mol / L.

[0056] For example,

[0057] Polyethylene oxide (PEO) (i.e. polymer A) with a molecular weight of 600,000 was dissolved in acetonitrile to obtain a 10 wt% solution. The solution was then coated onto a polytetrafluoroethylene mold and dried to obtain a polymer film with a thickness of 50 micrometers.

[0058] Will The monomers of polymer B and benzoin dimethyl ether are dissolved in ethylene glycol dimethyl ether to obtain mixture I. Mixture I is coated on the surface of a polymer film and polymerized under ultraviolet light to obtain polymer B. After vacuum drying at 60°C, a polymer bilayer film is obtained, which is the polymer matrix. The film thickness of polymer A is 50 micrometers and the film thickness of polymer B is 3 micrometers.

[0059] Lithium difluorosulfonylimide was dissolved in 1,3-dioxolane and dimethyl ethylene glycol (DOL / DME) in a volume ratio of 1:1 to prepare a 1 mol / L mixed solution II. The polymer matrix was then immersed in mixed solution II for 2 hours, and the residual solution on the surface was wiped off to obtain the electrolyte.

[0060] Further, the thickness of the film (i.e., polymer A) is 10-100 μm, and the thickness of the mixed solution I after coating and drying (i.e., polymer B) is 0.2-10 μm. The thickness of polymer A disclosed in the present embodiment is advantageous for the amount of liquid absorbed and the strength of the gel electrolyte to be moderate, while reducing the concentration polarization and improving the energy density of the battery. The thickness range of polymer B can effectively prevent the contact of the organic solvent with the lithium metal and does not affect the transport of lithium ions.

[0061] Further, the solvent is selected from at least one of tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, diethyl ether, diisopropyl ether, dibutyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether, acetone, butanone, ethyl acetate, butyl acetate, ethyl propionate, butyl propionate, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methyl pyrrolidone.

[0062] Further, the initiator is selected from one of azobisisobutyronitrile, azobisisoheptyl nitrile, benzoyl peroxide, lauroyl peroxide, butyl benzoyl peroxide, methyl ethyl ketone peroxide, benzoin dimethyl ether, methyl o-benzoylbenzoate, 4-phenyl dimethyl ketone, and 2,4,6-trimethyl benzoyl phosphinic acid ethyl ester.

[0063] Further, the soaking time of the polymer matrix in the mixed solution II is 0.5-12 h. The preferred soaking time is 2-4 h, the conductivity of the gel electrolyte can reach a high level, but there is no risk of extrusion overflow, and the strength of the gel electrolyte can be maintained at an appropriate level.

[0064] In a third aspect, the present application provides a negative electrode of a lithium battery, comprising a negative electrode current collector and a negative electrode active material layer on the surface of the negative electrode current collector, the surface of the negative electrode active material layer having an interface protection film, the interface protection film being formed by the gel electrolyte according to the first aspect. Thus, the negative electrode has all the features and advantages of the electrolyte described above, which will not be repeated here.

[0065] In a fourth aspect, the present application provides a lithium battery, comprising the gel electrolyte of the first aspect and / or the negative electrode of the third aspect. Thus, the lithium battery has all the features and advantages of the electrolyte and / or the negative electrode described above, which will not be repeated here. In general, the lithium battery has a good cycle life.

[0066] The negative electrode of the lithium battery can be a silicon negative electrode, such as pure silicon, silicon oxide or silicon-carbon composite material. The negative electrode of the lithium battery can also be a metal lithium negative electrode, etc.

[0067] The positive electrode of the lithium battery can be a ternary nickel-cobalt-manganese material, for example, LiNi 0.33 Co 0.33 Mn0.33 O2 (NCM111 type), LiNi 0.4 Co 0.2 Mn 0.4 O2 (NCM424 type), LiNi 0.5 Co 0.2 Mn 0.3 O2 (NCM523 type), LiNi 0.6 Co 0.2 Mn 0.2 O2 (NCM622 type), LiNi 0.8 Co 0.1 Mn 0.1 O2 (NCM811 type).

[0068] In a fifth aspect, the present application provides a vehicle comprising the lithium battery of the third aspect. For example, the vehicle can comprise a plurality of battery packs each comprising the lithium battery described above. The vehicle thus has all the features and advantages of the lithium battery described above, which will not be repeated here.

[0069] The present application will be described in detail below with reference to specific examples. It should be noted that the following specific examples are for illustrative purposes only and do not limit the scope of the present application in any way. In addition, unless otherwise specified, the methods not specifically described in terms of conditions or steps are conventional methods, and the reagents and materials used are commercially available.

[0070] Example 1

[0071] (1) Preparation of electrolyte:

[0072] Polyethylene oxide (PEO) with a molecular weight of 600,000 (i.e. polymer A) was dissolved in acetonitrile to obtain a 10wt% solution, and then the solution was coated in a polytetrafluoroethylene mold to obtain a polymer film with a thickness of 50 microns after drying;

[0073] The monomer of polymer B (polymer B monomer) and benzoin dimethyl ether were dissolved in ethylene glycol dimethyl ether to obtain a mixed solution I, and the mixed solution I was coated on the surface of the polymer film and polymerized under ultraviolet light to obtain polymer B After vacuum drying at 60°C, a polymer double-layer film was obtained, i.e. a polymer matrix, wherein the film thickness of polymer A was 50 microns and the film thickness of polymer B was 3 microns; Lithium bisfluorosulfonylimide was dissolved in 1,3-dioxolane and ethylene glycol dimethyl ether (DOL / DME) at a volume ratio of 1:1 to prepare a 1 mol / L solution, and then the polymer matrix was immersed in the solution for 2 hours, and the residual solution on the surface was wiped off to obtain a gel electrolyte.

[0074] ​

[0075] (2) Half-cell preparation

[0076] A CR2025 button cell was assembled in an argon-filled glove box (O2 content < 0.5 ppm, H2O < 0.5 ppm), in which the positive electrode was a lithium iron phosphate electrode, the negative electrode was a 25 μm lithium foil, the electrolyte was the above-mentioned gel electrolyte, and the separator was a 14 μm PE separator.

[0077] Example 2

[0078] This example differs from Example 1 in that the structure of polymer B is as follows,

[0079]

[0080] Example 3

[0081] This example differs from Example 1 in that the structure of polymer B is as follows,

[0082]

[0083] Example 4

[0084] This example differs from Example 1 in that the structure of polymer B is as follows,

[0085]

[0086] Example 5

[0087] This example differs from Example 1 in that the film thickness of polymer B is 0.5 μm.

[0088] Example 6

[0089] This example differs from Example 1 in that the film thickness of polymer B is 10 μm.

[0090] Example 7

[0091] This example differs from Example 1 in that the film thickness of polymer A is 10 μm.

[0092] Example 8

[0093] This example differs from Example 1 in that the film thickness of polymer A is 100 μm.

[0094] Example 9

[0095] This example differs from Example 1 in that polymer A is an ethylene oxide-propylene oxide copolymer with a molecular weight of 600,000.

[0096] Example 10

[0097] The difference between this example and Example 1 is that the polymer matrix is soaked in 1 mol / L DOL / DME (1:1) solution for 0.5 h.

[0098] Example 11

[0099] The difference between this example and Example 1 is that the polymer matrix is soaked in 1 mol / L DOL / DME (1:1) solution for 12 h.

[0100] Comparative Example 1

[0101] The difference between this comparative example and Example 1 is that no polymer matrix is included, and only the electrolyte is 1 mol / L DOL / DME (1:1) solution.

[0102] Comparative Example 2

[0103] The difference between this comparative example and Example 1 is that the negative electrode is a 25 μm thick lithium foil with a 3 μm thick polymer matrix adhered to it, and it is soaked in 1 mol / L DOL / DME (1:1) solution.

[0104] Comparative Example 3

[0105] The difference between this comparative example and Example 1 is that a 50 μm thick polyethylene oxide film is prepared and soaked in 1 mol / L DOL / DME (1:1) solution for 2 h, and the surface residual solution is wiped off to obtain the electrolyte.

[0106] The lithium batteries obtained in the above examples and comparative examples are subjected to the following performance tests to characterize the electrochemical performance of the gel electrolyte.

[0107] The test procedure is as follows: The test method is as follows: 10 batteries each of the batteries prepared in each example and comparative example are taken, and the batteries are subjected to charge-discharge cycle tests at 0.5 C on a LAND CT 2001C secondary battery performance testing device at 25±1°C. The procedure is as follows: stand for 5 min; constant current charge to 3.8 V cutoff; stand for 5 min; constant current discharge to 2.7 V, which is 1 cycle. Repeat the procedure, and when the battery capacity is lower than 80% of the initial discharge capacity during the cycle, the cycle is terminated, and the cycle number is the cycle life of the battery. The test results are shown in Table 1.

[0108] Table 1 Performance test results of half-batteries prepared in Examples 1-11 and Comparative Examples 1-3

[0109]

[0110]

[0111] From the results shown in Table 1, the following conclusions can be drawn:

[0112] From the test results of Examples 1-11 and Comparative Example 1, it can be concluded that the cycle life performance of the half-cells assembled with the gel electrolytes of Examples 1-11 is superior to that of the half-cell of Comparative Example 1. There is no polymer matrix in the half-cell of Comparative Example 1, and thus the gel electrolytes of the examples of the present application are beneficial to improve the performance of the battery.

[0113] From the test results of Example 1 and Examples 2-4, it can be concluded that different R groups and m values have little effect on the performance of the polymer, and the polymer structures disclosed in the examples of the present application can effectively improve the performance of the battery.

[0114] From the test results of Example 1 and Examples 5-8, it can be concluded that the thickness range of the gel electrolytes disclosed in the present application is beneficial to improve the cycle life of the half-cell. On the one hand, the range of the gel electrolytes disclosed in the present application can dissolve and disperse organic solvents and lithium salts, reducing the flowability of the electrolyte; on the other hand, it is beneficial to prevent the contact between the electrolyte and lithium metal, reducing the consumption of the electrolyte and active lithium.

[0115] From the test results of Example 1 and Example 9, it can be concluded that different polymer types have little effect on the performance of the gel electrolyte, and the polymers disclosed in the examples of the present application can effectively improve the performance of the battery.

[0116] From the test results of Example 1 and Examples 10-11, it can be concluded that the time range of the polymer matrix soaked in the electrolyte disclosed in the present application is beneficial to improve the cycle life of the half-cell.

[0117] From the test results of Examples 1-11 and Comparative Examples 2-3, it can be concluded that the cycle life of the half-cells of Examples 1-11 is superior to that of the half-cells of Comparative Examples 2-3. The polymer matrix of Comparative Examples 2-3 only includes one kind of polymer. Therefore, it can be known that the polymers disclosed in the present application can improve the performance of the battery due to the synergistic effect of polymer A and polymer B, which reduces the flowability of the electrolyte, prevents the contact between the electrolyte and lithium metal, reduces the consumption of the electrolyte and active lithium; at the same time, it can also effectively conduct lithium ions, making the distribution of lithium ions uniform, and then the uniform deposition of lithium ions is beneficial to inhibit the generation of lithium dendrites.

[0118] The above description is merely preferred embodiments of the present application and a description of the principles of the technology used. Those skilled in the art should understand that the scope of the application disclosed in the present application is not limited to the technical solutions formed by the specific combinations of the above technical features, and also covers other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the inventive concept. For example, the above features are replaced with the technical features disclosed in the present application (but not limited to) having similar functions to form a technical solution.

Claims

1. A gel electrolyte, characterized in that, It includes a lithium salt, an organic solvent, and a polymer matrix; the polymer matrix includes polymer A and polymer B, and the structural formula of polymer B is as follows: R1 is selected from one of hydrogen, halogen, substituted or unsubstituted C1-C6 alkyl groups; R2 is selected from the methylene group of C0-C6 with or without the substituent, or the C6-C6 group with or without the substituent. 12 The aryl group, the substituents, or the unsubstituted C6-C 12 cycloalkyl groups, substituted or unsubstituted C2-C groups containing heteroatoms 10 alkyl, , Wherein, M is a C0-C6 methylene group (substituted or unsubstituted), a phenyl group (substituted or unsubstituted), a cyclohexyl group (substituted or unsubstituted), or a C2-C group (substituted or unsubstituted) containing a heteroatom. 10 Alkyl groups; m is any integer between 1 and 50; n is any integer between 2 and 100000; The polymer A is selected from at least one of the following: polyethylene oxide, ethylene oxide-styrene copolymer, ethylene oxide-propylene oxide copolymer, ethylene oxide-ethylene copolymer, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polymethyl acrylate, polymethyl methacrylate, methyl methacrylate-butyl methacrylate copolymer, polyvinyl carbonate, polypropylene carbonate, polyfluoropropylene carbonate, and polypyrrolidone.

2. The gel electrolyte according to claim 1, characterized in that, The substituents are selected from halogens, hydroxyl groups, amino groups, carboxyl groups, carbonyl groups, cyano groups, sulfonic acid groups, C1-C6 alkoxy groups, C1-C6 alkyl groups, and C6-C6 alkyl groups. 12 aryl or C6-C 12 cycloalkyl groups.

3. The gel electrolyte according to claim 2, characterized in that, The halogen is selected from fluorine, chlorine, and bromine; the amino group is selected from C1-C6 primary amines, C1-C6 alkyl-substituted secondary or tertiary amines; the C1-C6 alkoxy group is selected from methoxy or ethoxy; the C1-C6 alkyl group is selected from methyl, ethyl, propyl, isopropyl, butyl, or tert-butyl; the C6-C... 12 The aryl group is selected from phenyl, naphthyl, or biphenyl; the C6-C 12 The cycloalkyl group is selected from cyclohexyl or bicyclohexyl.

4. The gel electrolyte according to claim 1, characterized in that, The polymer A is selected from the polymer obtained by polymerizing monomers of at least two of the following polymers: polyethylene oxide, ethylene oxide-styrene copolymer, ethylene oxide-propylene oxide copolymer, ethylene oxide-ethylene copolymer, polyvinylidene fluoride, vinylidene fluoride-hexafluoropropylene copolymer, polymethyl acrylate, polymethyl methacrylate, methyl methacrylate-butyl methacrylate copolymer, ethylene carbonate, polypropylene carbonate, polyfluoropropylene carbonate, and polypyrrolidone.

5. The gel electrolyte according to any one of claims 1-3, characterized in that, The polymer matrix accounts for 10% to 70% of the total mass of the gel electrolyte; the organic solvent accounts for 5% to 50% of the total mass of the gel electrolyte; and the lithium salt accounts for 25% to 40% of the total mass of the gel electrolyte.

6. The gel electrolyte according to any one of claims 1-3, characterized in that, The lithium salt is selected from at least one of lithium bis(trifluoromethanesulfonyl)imide, lithium bis(fluorosulfonyl)imide, lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium tetrafluoroborate, lithium difluorooxalate borate, lithium dioxalate borate, and lithium perchlorate.

7. The gel electrolyte according to any one of claims 1-3, characterized in that, The organic solvent is selected from ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, propylene glycol methyl ethyl ether, butanediol dimethyl ether, butanediol diethyl ether, butanediol methyl ethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol diethyl ether, tetraethylene glycol diethyl ether, dipropylene glycol dimethyl ether, tripropylene glycol dimethyl ether, tetrapropylene glycol dimethyl ether, dipropylene glycol diethyl ether, tripropylene glycol diethyl ether, tetrapropylene glycol diethyl ... The ether, dibutylene glycol dimethyl ether, tributylene glycol dimethyl ether, tetrabutylene glycol dimethyl ether, dibutylene glycol diethyl ether, tributylene glycol diethyl ether, tetrabutylene glycol diethyl ether, 1,3-dioxolane, 1,4-dioxane, tetrahydrofuran, 1,1,2,2-tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, 2,2,3,3,4,4,5,5-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, propylene carbonate, ethylene carbonate, diethyl carbonate, or dimethyl carbonate.

8. A method for preparing a gel electrolyte as described in any one of claims 1-7, characterized in that, The process includes the following: After dissolving the polymer A in a solvent, it is coated onto a mold to form a film; The monomer, solvent and initiator of polymer B are mixed evenly to obtain mixture I. Mixture I is coated on the surface of the film, polymerized by heating or light irradiation, and dried to obtain the polymer matrix. The organic solvent and the lithium salt are mixed to obtain mixture II, and the polymer matrix is ​​immersed in mixture II to obtain the gel electrolyte.

9. The method according to claim 8, characterized in that, The thickness of the membrane is 10~100μm, and the thickness of the mixed liquid I after coating and drying is 0.2~10μm.

10. The method according to claim 8, characterized in that, The solvent is selected from at least one of tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, diethyl ether, propyl ether, butyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl ether, acetone, butanone, ethyl acetate, butyl acetate, ethyl propionate, butyl propionate, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, and N-methylpyrrolidone.

11. The method according to claim 8, characterized in that, The initiator is selected from one of azobisisobutyronitrile, azobisisoheptanenitrile, benzoyl peroxide, lauroyl peroxide, butyl peroxide, methyl ethyl ketone peroxide, benzoin dimethyl ether, methyl o-benzoylbenzoate, 4-phenyl dimethyl ketone, and ethyl 2,4,6-trimethylbenzoylphosphonate.

12. The method according to claim 8, characterized in that, The polymer matrix is ​​immersed in the mixture II for 0.5 to 12 hours.

13. A negative electrode for a lithium battery, characterized in that, It includes a negative electrode current collector and a negative electrode active material layer located on the surface of the negative electrode current collector, wherein the surface of the negative electrode active material layer has an interface protective film, and the interface protective film is formed by gel electrolyte according to any one of claims 1-7.

14. A lithium battery, characterized in that, include: The gel electrolyte according to any one of claims 1-7 and / or the negative electrode according to claim 13.

15. A vehicle, characterized in that, Including the lithium battery as described in claim 14.

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