Secondary battery and manufacturing method therefor, and electric device

Abstract

The present invention relates to a secondary battery and a manufacturing method therefor, and an electric device. The secondary battery comprises a negative electrode sheet and a gel electrolyte; the negative electrode sheet contains a negative electrode active material; the negative electrode active material comprises a carbon-containing material; the gel electrolyte comprises a polymer, an organic solvent, and an electrolyte salt; the organic solvent comprises one or more of an ether-based organic solvent, a sulfone-based organic solvent, a phosphate-based organic solvent, and a carbonate-based organic solvent; the polymer comprises one or more of a carbon-oxygen double bond and a carbon-oxygen single bond; and the mass ratio of the polymer in the gel electrolyte is 0.5%-38%.

Description

Secondary battery, preparation method thereof, and power-consuming device Technical Field

[0001] The present application relates to the field of battery technology, and in particular to a secondary battery, a preparation method thereof, and an electrical device. Background Art

[0002] Secondary batteries, with their advantages of low self-discharge, long cycle life, and minimal pollution, are widely used in electric vehicles, portable electronic products, and other fields. However, conventional liquid secondary batteries face the following challenges in practical applications: some electrolyte solvents undergo severe side reactions at the electrode interface, leading to the continuous growth of the solid electrolyte interface film (SEI film), electrolyte decomposition and gas production, increased interfacial impedance, or graphite exfoliation, impacting the battery's rate and cycle performance. Furthermore, liquid organic electrolytes can burn and explode under extreme operating conditions such as overcharging, collision, extrusion, and puncture, posing significant safety risks and necessitating urgent improvements in safety performance.

[0003] Summary of the Invention

[0004] The present application provides a secondary battery, a preparation method thereof, and an electrical device, aiming to improve the rate performance and safety performance of the secondary battery.

[0005] In a first aspect of the present application, a secondary battery is provided, comprising a negative electrode sheet and a gel electrolyte, wherein the negative electrode sheet contains a negative electrode active material, the negative electrode active material includes a carbonaceous material, the gel electrolyte includes a polymer, an organic solvent and an electrolyte salt, the organic solvent includes one or more of an ether organic solvent, a sulfone organic solvent, a phosphate organic solvent and a carbonate organic solvent, the polymer contains one or more of a carbon-oxygen double bond and a carbon-oxygen single bond, and the mass proportion of the polymer in the gel electrolyte is 0.5% to 38%.

[0006] In the above embodiment, the polymer containing at least one of a carbon-oxygen double bond and a carbon-oxygen single bond has a certain polarity and can react with Li + coordination, by inhibiting Li + The combination with the above-mentioned organic solvent molecules changes the Li + The solvation structure of the present invention can significantly inhibit the co-intercalation effect of ether organic solvents, sulfone organic solvents, phosphate organic solvents and carbonate organic solvents on carbon-containing materials; in addition, the mass proportion of the above-mentioned polymer in the gel electrolyte is controlled within a reasonable range, and the synergistic effect of ether organic solvents, sulfone organic solvents, phosphate organic solvents, carbonate organic solvents and the above-mentioned polymer is utilized to improve the conductivity and wettability of the gel electrolyte, so that the rate performance and safety performance of the above-mentioned secondary battery are significantly improved, and the secondary battery has excellent cycle performance.

[0007] In some embodiments, the polymer accounts for 5% to 30% by weight in the gel electrolyte.

[0008] In some embodiments, the polymer accounts for 7% to 20% by weight in the gel electrolyte.

[0009] In some embodiments, the polymer comprises a homopolymer or copolymer of one or more monomer units represented by the structures of Formula I to Formula III:

[0010] Wherein, M1 includes any one of a substituted or unsubstituted carbonyl group and a substituted or unsubstituted ether group, M2 and M3 each independently include any one of a substituted or unsubstituted amide group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, a substituted or unsubstituted heteroalkyl group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted amino group, a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkenylene group and a substituted or unsubstituted arylalkyl group, 1≤n1≤10, 1≤n2≤10, 1≤n3≤10, and * represents a bond.

[0011] In some embodiments, the polymer includes one or more of polyacrylate compounds, polyethylene oxide, and homologues thereof.

[0012] In some embodiments, the polyacrylate compound includes one or more of polymethyl methacrylate, polybutyl acrylate, polymethyl acrylate, and poly(ethylene glycol) diacrylate.

[0013] In some embodiments, the ether organic solvent includes one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, polyethylene glycol dimethyl ether, and crown ether.

[0014] In some embodiments, the sulfone organic solvent includes one or more of dimethyl sulfoxide, phenethyl sulfone, diethyl sulfone, diphenyl sulfone, sulfolane, and bisphenol S.

[0015] In some embodiments, the phosphate ester organic solvent includes one or more of trimethyl phosphate, triethyl phosphate, and tripropyl phosphate.

[0016] In some embodiments, the carbonate organic solvent includes one or more of ethylene carbonate, propylene carbonate, fluoroethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.

[0017] In some embodiments, the carbon-containing material includes one or more of artificial graphite, natural graphite, soft carbon, hard carbon, and silicon-carbon composite materials.

[0018] In some embodiments, the electrolyte salt includes one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalatoborate), lithium difluorooxalatoborate, lithium difluorobis(oxalatophosphate), lithium difluorophosphate, lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis(trifluoromethylsulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, tris(trifluoromethylsulfonyl)methyllithium, and lithium bis(fluorosulfonyl)imide.

[0019] In some embodiments, the gel electrolyte further includes an additive, and the additive includes one or more of fluoroethylene carbonate, vinylene carbonate, lithium difluorooxalatoborate, lithium difluorophosphate, vinyl sulfate, 1,3-propane sultone, tris(trimethylsilane)phosphate, tris(trimethylsilane)borate, propene sultone, fluorobenzene, vinyl ethylene carbonate, and lithium nitrate.

[0020] In some embodiments, the secondary battery further includes a positive electrode sheet, wherein the positive electrode active material in the positive electrode sheet includes one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium manganese oxide, lithium cobalt oxide, ternary materials, lithium nickel manganese oxide, lithium-rich manganese-based materials, sulfur-containing materials, and their respective modified compounds.

[0021] In a second aspect of the present application, a method for preparing a secondary battery is provided, comprising the following steps:

[0022] impregnating the negative electrode sheet with a gel electrolyte precursor comprising a polymer monomer, an organic solvent, and an electrolyte salt, and curing the gel electrolyte precursor to form a gel electrolyte;

[0023] The negative electrode sheet contains a negative electrode active material, which includes a carbonaceous material. The gel electrolyte includes a polymer formed by the organic solvent, the electrolyte salt, and the polymer monomer. The organic solvent includes one or more of an ether organic solvent, a sulfone organic solvent, a phosphate organic solvent, and a carbonate organic solvent. The polymer contains one or more of a carbon-oxygen double bond and a carbon-oxygen single bond. The mass proportion of the polymer in the gel electrolyte is 0.5% to 38%.

[0024] The above preparation method is simple to operate and easy to mass produce secondary batteries. The polymer containing at least one of a carbon-oxygen double bond and a carbon-oxygen single bond has a certain polarity and can react with Li + coordination, by inhibiting Li + The combination with the above-mentioned organic solvent molecules changes the Li +The solvation structure of the above-mentioned polymer is significantly inhibited, thereby significantly inhibiting the co-embedding effect of ether organic solvents, sulfone organic solvents, phosphate organic solvents and carbonate organic solvents on carbon-containing materials; in addition, the mass proportion of the above-mentioned polymer in the gel electrolyte is controlled within a reasonable range, and the synergistic effect of ether organic solvents, sulfone organic solvents, phosphate organic solvents, carbonate organic solvents and the above-mentioned polymer is utilized to improve the conductivity and wettability of the gel electrolyte, so that the rate performance and safety performance of the above-mentioned secondary battery are significantly improved, and the secondary battery has excellent cycle performance. In addition, in the above-mentioned preparation method, the gel electrolyte precursor can fully infiltrate the negative electrode sheet, which is conducive to the formation of a dense and sufficient solid-solid contact interface after subsequent curing, thereby providing rich Li + The mass transfer interface can further improve the rate performance and kinetic performance of secondary batteries.

[0025] In some embodiments, the secondary battery further comprises a positive electrode sheet and a separator; before the step of impregnating the negative electrode sheet with a gel electrolyte precursor comprising a polymer monomer, an organic solvent, and an electrolyte salt, the step further comprises: laminating or winding the positive electrode sheet, the separator, and the negative electrode sheet to form an electrode assembly;

[0026] After the step of forming the electrode assembly, the electrode assembly is impregnated with the gel electrolyte precursor containing the polymer monomer, the organic solvent, and the electrolyte salt, and the gel electrolyte precursor is cured to form the gel electrolyte.

[0027] In a third aspect of the present application, an electrical device is provided, which includes at least one of the secondary battery described in the first aspect of the present application and the secondary battery prepared by the preparation method described in the second aspect of the present application.

[0028] The electrical device of the present application includes at least one of the secondary battery provided in the present application and the secondary battery prepared by the preparation method provided in the present application, and thus has at least the same advantages as the secondary battery or the preparation method.

[0029] The details of one or more embodiments of the present application are set forth in the description below. Other features, objects, and advantages of the present application will become apparent from the description and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the disclosed drawings without any creative work.

[0031] FIG1 is a rate performance test diagram of the batteries of Example 1 and Comparative Example 7 of the present application.

[0032] FIG2 is a bar graph of the DC internal resistance of the batteries of Example 1 and Comparative Example 7 of the present application.

[0033] FIG3 is a graph showing the first charge and discharge curves of the batteries of Example 11 and Comparative Example 4 of the present application.

[0034] FIG4 is a graph showing the first charge and discharge curves of the batteries of Example 12 and Comparative Example 5 of the present application.

[0035] FIG5 is a graph showing the first charge and discharge curves of the batteries of Example 13 and Comparative Example 6 of the present application. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0037] In this application, terms such as "first aspect," "second aspect," and "third aspect" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor as implicitly indicating the importance or quantity of the technical features indicated. Furthermore, terms such as "first," "second," and "third," etc., are intended only to provide a non-exhaustive enumeration and description and should not constitute a closed-ended limitation on quantity.

[0038] In this application, the terms "optionally," "optional," and "optional" mean optional or dispensable, i.e., they refer to either option being selected from two parallel options: "with" or "without." If a technical solution contains multiple "optional" clauses, each "optional" clause is independent unless otherwise specified and there are no contradictions or constraints.

[0039] In this application, when referring to numerical ranges, unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values ​​of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values ​​of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges subsumed therein.

[0040] In this application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0041] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used in this application and in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in this application includes any and all combinations of one or more related listed items. The term "multiple" in this application means at least two, such as two, three, etc., unless otherwise clearly and specifically limited.

[0042] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0043] The term "monomer unit" refers to a general term for small molecules that can polymerize with the same or other molecules, including organic small molecule compounds that can be polymerized, as well as oligomers or prepolymers of organic small molecule compounds that can be polymerized.

[0044] The term "carbonyl" refers to an organic group including -CO-, wherein -CO- is a carbon-oxygen double bond.

[0045] The term "ether group" refers to an organic group including -COC-, wherein each of -COC- is a carbon-oxygen single bond.

[0046] The term "amido" refers to an organic group including -CON-.

[0047] The term "alkyl" refers to a saturated hydrocarbon containing primary (normal) carbon atoms, secondary carbon atoms, tertiary carbon atoms, quaternary carbon atoms, or combinations thereof. Phrases containing this term, for example, "C1-C9 alkyl" refers to an alkyl group containing 1 to 9 carbon atoms, each occurrence of which can independently be C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, C7 alkyl, C8 alkyl, or C9 alkyl. Suitable examples include, but are not limited to, methyl (Me, -CH3), ethyl (Et, -CH2CH3), 1-propyl (n-Pr, n-propyl, -CH2CH2CH3), 2-propyl (i-Pr, i-propyl, -CH(CH3)2), 1-butyl (n-Bu, n-butyl, -CH2CH2CH2CH3), 2-methyl-1-propyl (i-Bu, i-butyl, -CH2CH(CH3)2), 2-butyl (s-Bu, s-butyl, -CH(C H3)CH2CH3), 2-methyl-2-propyl (t-Bu, t-butyl, -C(CH3)3), 1-pentyl (n-pentyl, -CH2CH2CH2CH2CH3), 2-pentyl (-CH(CH3)CH2CH2CH3), 3-pentyl (-CH(CH2CH3)2), 2-methyl-2-butyl (-C(CH3)2CH2CH3), 3-methyl-2-butyl (-CH(CH3)CH(CH3)2), 3-methyl-1-butyl (- CH2CH2CH(CH3)2), 2-methyl-1-butyl (-CH2CH(CH3)CH2CH3), 1-hexyl (-CH2CH2CH2CH2CH2CH3), 2-hexyl (-CH(CH3)CH2CH2CH2CH3), 3-hexyl (-CH(CH2CH3)(CH2CH2CH3)), 2-methyl-2-pentyl (-C(CH3)2CH2CH2CH3), 3-methyl-2-pentyl (-CH(CH3)CH( )2), 2-methyl-3-pentyl (-CH(CH2CH3)CH(CH3)2), 2,3-dimethyl-2-butyl (-C(CH3)2CH(CH3)2), 3,3-dimethyl-2-butyl (-CH(CH3)C(CH3)3 and octyl (-(CH2)7CH3).

[0048] The term "cycloalkyl" refers to a non-aromatic hydrocarbon group containing ring carbon atoms, which can be a monocyclic alkyl group, a spirocyclic alkyl group, or a bridged cycloalkyl group. Phrases containing this term, for example, "C3-C9 cycloalkyl" refers to a cycloalkyl group containing 3 to 9 carbon atoms, each occurrence of which can be independently C3 cycloalkyl, C4 cycloalkyl, C5 cycloalkyl, C6 cycloalkyl, C7 cycloalkyl, C8 cycloalkyl, or C9 cycloalkyl. Suitable examples include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, and cycloheptyl. In addition, "cycloalkyl" can also contain one or more double bonds. Representative examples of cycloalkyl groups containing double bonds include cyclopentenyl, cyclohexenyl, cyclohexadienyl, and cyclobutadienyl.

[0049] The term "alkoxy" refers to a group having an -O-alkyl group, i.e., an alkyl group as defined above connected to a parent core structure via an oxygen atom. Phrases containing this term, for example, "C1-C9 alkoxy" means that the alkyl portion contains 1 to 9 carbon atoms, and each occurrence can be independently C1 alkoxy, C4 alkoxy, C5 alkoxy, C6 alkoxy, C7 alkoxy, C8 alkoxy or C9 alkoxy. Suitable examples include, but are not limited to, methoxy (-O-CH3 or -OMe), ethoxy (-O-CH2CH3 or -OEt) and tert-butoxy (-OC(CH3)3 or -OtBu).

[0050] The term "alkenyl" refers to a group containing at least one unsaturated site, i.e., a carbon-carbon sp 2 A hydrocarbon containing a positive, secondary, tertiary or cyclic carbon atom of a double bond. Phrases containing this term, for example, "C2-C9 alkenyl" refers to an alkenyl group containing 2 to 9 carbon atoms, each occurrence of which can be independently C2 alkenyl, C3 alkenyl, C4 alkenyl, C5 alkenyl, C6 alkenyl, C7 alkenyl, C8 alkenyl or C9 alkenyl. Suitable examples include, but are not limited to, vinyl (-CH=CH2), allyl (-CH2CH=CH2), cyclopentenyl (-C5H7) and 5-hexenyl (-CH2CH2CH2CH2CH=CH2).

[0051] The term "aryl" refers to an aromatic hydrocarbon group derived from an aromatic ring compound by removing a hydrogen atom. It can be a monocyclic aromatic group, a condensed aromatic group, or a polycyclic aromatic group. For polycyclic aromatic groups, at least one of them is an aromatic ring system. For example, "C6-C 20 "Aryl" refers to an aromatic group containing 6 to 20 carbon atoms, each occurrence of which can be independently C6 aromatic, C 10 Aryl, C 14 Aryl, C 18 Aryl or C 20 Suitable examples include, but are not limited to, benzene, biphenyl, naphthalene, anthracene, phenanthrene, perylene, triphenylene, and derivatives thereof.

[0052] The term "heteroaryl" means that at least one carbon atom in an aryl group is replaced by a non-carbon atom, which may be a nitrogen atom, an oxygen atom, or a sulfur atom. For example, "C3-C 10 The term "heteroaryl" refers to a heteroaryl group containing 3 to 10 carbon atoms, which, at each occurrence, is independently C3 heteroaryl, C4 heteroaryl, C5 heteroaryl, C6 heteroaryl, C7 heteroaryl or C8 heteroaryl. Suitable examples include, but are not limited to, furan, benzofuran, thiophene, benzothiophene, pyrrole, pyrazole, triazole, imidazole, oxazole, oxadiazole, thiazole, tetrazole, indole, carbazole, pyrroloimidazole, pyrrolopyrrole, thienopyrrole, thienothiophene, furopyrrole, furofuran, thienofuran, benzisoxazole, benzisothiazole, benzimidazole, pyridine, pyrazine, pyridazine, pyrimidine, triazine, quinoline, isoquinoline, o-naphthyridine, quinoxaline, phenanthridine, primidine, quinazoline and quinazolinone.

[0053] The term "heteroalkyl" refers to an alkyl group in which at least one carbon atom is replaced by a non-carbon atom, such as an N atom, an O atom, an S atom, or the like. For example, if the carbon atom connected to the parent core structure in the alkyl group is replaced by a non-carbon atom, the resulting heteroalkyl group is an alkoxy group (e.g., -OCH3, etc.), an amine (e.g., -NHCH3, -N(CH3)2, etc.), or a thioalkyl group (e.g., -SCH3). If the carbon atom not connected to the parent core structure in the alkyl group is replaced by a non-carbon atom, the resulting heteroalkyl group is an alkyl ether (e.g., -CH2CH2-O-CH3, etc.), an alkylamine (e.g., -CH2NHCH3, -CH2N(CH3)2, etc.), or a thioalkyl ether (e.g., -CH2-S-CH3). If the terminal carbon atom of the alkyl group is replaced by a non-carbon atom, the resulting heteroalkyl group is a hydroxyalkyl group (e.g., -CH2CH2-OH), an aminoalkyl group (e.g., -CH2NH2), or an alkylthiol group (e.g., -CH2CH2-SH). Phrases containing this term, for example, "C1-C9 heteroalkyl" means a heteroalkyl group containing 1 to 9 carbon atoms, which at each occurrence can be independently C2 heteroalkyl, C3 heteroalkyl, C4 heteroalkyl, C5 heteroalkyl, C7 heteroalkyl, C8 heteroalkyl or C9 heteroalkyl.

[0054] The term "heterocyclyl" refers to a cycloalkyl group in which at least one carbon atom is replaced by a non-carbon atom, which may be a nitrogen atom, an oxygen atom, an sulfur atom, or the like, and may be a saturated ring or a partially unsaturated ring. Phrases containing this term, for example, "C4-C9 heterocyclyl" refers to a heterocyclyl group containing 4 to 9 carbon atoms, each occurrence of which may be independently C4 heteroalkyl, C6 heteroalkyl, C7 heteroalkyl, C8 heteroalkyl, or C9 heteroalkyl. Suitable examples include, but are not limited to, dihydropyridyl, tetrahydropyridyl (piperidyl), tetrahydrothienyl, sulfur-oxidized tetrahydrothienyl, tetrahydrofuranyl, tetrahydroquinolinyl, tetrahydroisoquinolinyl, and dihydroindolinyl.

[0055] The term "amino" refers to a derivative of ammonia having the structural characteristics of the formula -N(X)2, wherein each "X" is independently H, substituted or unsubstituted alkyl, substituted or unsubstituted cycloalkyl, substituted or unsubstituted heterocyclyl, etc. Non-limiting types of amino groups include -NH2, -N(alkyl), -NH(alkyl), -N(cycloalkyl), -NH(cycloalkyl), -N(heterocyclyl), -NH(heterocyclyl), -N(aryl), -NH(aryl), -N(alkyl)(aryl), -N(alkyl)(heterocyclyl), -N(cycloalkyl)(heterocyclyl), -N(aryl)(heteroaryl), -N(alkyl)(heteroaryl), and the like.

[0056] The term "alkylene" refers to a hydrocarbon group derived from an alkyl group by removing a hydrogen atom to form a two-radical center, which can be a saturated branched alkyl group or a saturated straight-chain alkyl group. For example, "C1-C9 alkylene" means that the alkyl portion contains 1 to 9 carbon atoms, and each occurrence can be independently C1 alkylene, C4 alkylene, C5 alkylene, C6 alkylene, C7 alkylene, C8 alkylene, or C9 alkylene. Suitable examples include, but are not limited to, methylene (-CH2-), 1,1-ethyl (-CH(CH3)-), 1,2-ethyl (-CH2CH2-), 1,1-propyl (-CH(CH2CH3)-), 1,2-propyl (-CH2CH(CH3)-), 1,3-propyl (-CH2CH2CH2-), and 1,4-butyl (-CH2CH2CH2CH2-).

[0057] The term "alkenylene" refers to a hydrocarbon group having two monovalent radical centers derived from an alkenyl group by removing a hydrogen atom, which can be an unsaturated branched hydrocarbon group or an unsaturated straight-chain hydrocarbon group. For example, "C2-C9 alkenylene" means that the alkenyl portion contains 2 to 9 carbon atoms, and each occurrence can be independently C2 alkenylene, C4 alkenylene, C5 alkenylene, C6 alkenylene, C7 alkenylene, C8 alkenylene, or C9 alkenylene. Suitable examples include, but are not limited to, 1,2-vinyl (-CH=CH-).

[0058] The term "arylalkyl" refers to a hydrocarbon group derived from an alkyl group in which at least one hydrogen atom bonded to a carbon atom is replaced by an aryl group. The aryl portion may include 5 to 20 carbon atoms, and the alkyl portion may include 1 to 9 carbon atoms. Suitable examples include, but are not limited to, benzyl, 2-phenyleth-1-yl, naphthylmethyl, 2-naphthyleth-1-yl, naphthobenzyl, and 2-naphthophenyleth-1-yl.

[0059] One embodiment of the present application provides a secondary battery, which includes a negative electrode sheet and a gel electrolyte, wherein the negative electrode sheet contains a negative electrode active material, the negative electrode active material includes a carbonaceous material, the gel electrolyte includes a polymer, an organic solvent and an electrolyte salt, the organic solvent includes one or more of an ether organic solvent, a sulfone organic solvent, a phosphate organic solvent and a carbonate organic solvent, the polymer includes one or more of a carbon-oxygen double bond and a carbon-oxygen single bond, and the mass proportion of the polymer in the gel electrolyte is 0.5% to 38%.

[0060] In the above embodiment, the polymer containing at least one of a carbon-oxygen double bond and a carbon-oxygen single bond has a certain polarity and can react with Li + coordination, by inhibiting Li + The combination with the above-mentioned organic solvent molecules changes the Li + The solvation structure of the present invention can significantly inhibit the co-intercalation effect of ether organic solvents, sulfone organic solvents, phosphate organic solvents and carbonate organic solvents on carbon-containing materials; in addition, the mass proportion of the above-mentioned polymer in the gel electrolyte is controlled within a reasonable range, and the synergistic effect of ether organic solvents, sulfone organic solvents, phosphate organic solvents, carbonate organic solvents and the above-mentioned polymer is utilized to improve the conductivity and wettability of the gel electrolyte, so that the rate performance and safety performance of the above-mentioned secondary battery are significantly improved, and the secondary battery has excellent cycle performance.

[0061] If the mass proportion of the polymer in the gel electrolyte is higher than 38%, the conductivity of the gel electrolyte is too low, the impedance of the secondary battery is too large, normal charge and discharge cannot be achieved, and the capacity is too low; if the mass proportion of the polymer in the gel electrolyte is lower than 0.5%, it is insufficient to protect the negative electrode. The carbon-containing material in the negative electrode sheet will be solvent-co-embedded under the action of the liquid electrolyte, resulting in the destruction of the carbon-containing material structure, causing the secondary battery to fail and the capacity to decay rapidly. It is understood that the mass proportion of the polymer in the gel electrolyte includes but is not limited to: 0.5%, 1%, 3%, 5%, 7%, 9%, 10%, 12%, 14%, 16%, 18%, 20%, 22%, 24%, 26%, 28%, 30%, 32%, 36%, 38%.

[0062] In this application, "carbon-containing material" refers to a material containing carbon and which can be embedded in or released from Li + .

[0063] In some embodiments, the polymer accounts for 5% to 30% by weight in the gel electrolyte, thereby further improving the rate performance and safety performance of the secondary battery.

[0064] In some embodiments, the polymer accounts for 7% to 20% by weight in the gel electrolyte, thereby further improving the rate performance and safety performance of the secondary battery.

[0065] In some embodiments, the polymer comprises a homopolymer or copolymer of one or more monomer units of the structures shown in Formula I to Formula III:

[0066] Wherein, M1 includes any one of a substituted or unsubstituted carbonyl group and a substituted or unsubstituted ether group, M2 and M3 each independently include any one of a substituted or unsubstituted amide group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, a substituted or unsubstituted heteroalkyl group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted amino group, a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkenylene group and a substituted or unsubstituted arylalkyl group, 1≤n1≤10, 1≤n2≤10, 1≤n3≤10, and * represents a bond. Thus, the rate performance, cycle performance and safety performance of the secondary battery can be further improved. M1 includes any one of a substituted or unsubstituted carbonyl group and a substituted or unsubstituted ether group, that is, M1 contains a polar oxygen atom with a lone pair of electrons. It can be understood that n1 includes but is not limited to: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, n2 includes but is not limited to: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and n3 includes but is not limited to: 1, 2, 3, 4, 5, 6, 7, 8, 9, 10.

[0067] In some embodiments, M2 and M3 are each independently selected from any one of a substituted or unsubstituted amide group, a substituted or unsubstituted alkyl group, and a substituted or unsubstituted alkoxy group. The above groups can increase the oxygen electron cloud density of the monomer unit of the polymer, promote the reaction with Li + The binding of Li + The solvation effect of the secondary battery can further improve the rate performance and safety performance of the secondary battery.

[0068] In some embodiments, the polymer includes one or more of polyacrylate compounds, polyethylene oxide, and homologues thereof. These polymers can be synergistically combined with ether organic solvents, sulfone organic solvents, phosphate organic solvents, and carbonate organic solvents to significantly inhibit solvent co-intercalation in the graphite anode, thereby improving the rate capability, cycle performance, and safety of the secondary battery. Optionally, the organic solvent includes an ether organic solvent.

[0069] It should be noted that polyethylene oxide and its homologues refer to polyethylene oxide (PEO) and polyethylene oxide homologues, and polyethylene oxide homologues include but are not limited to homopolymers or copolymers formed by polymerization of monomers such as butylene oxide and 1,3-dioxolane.

[0070] In some embodiments, the polyacrylate compound includes one or more of polymethyl methacrylate (PMMA), polybutyl acrylate (PBA), polymethyl acrylate (PMA), and poly(ethylene glycol) diacrylate. The above-mentioned types of polymers can be synergistically combined with ether organic solvents, sulfone organic solvents, phosphate organic solvents, and carbonate organic solvents to further improve the conductivity and wettability of the gel electrolyte, thereby further improving the rate performance, cycle performance, and safety performance of the secondary battery. Optionally, the organic solvent includes an ether organic solvent.

[0071] In some embodiments, the organic solvent includes an ether organic solvent. Ether organic solvents co-intercalate into the graphite negative electrode of traditional liquid secondary batteries, causing exfoliation and destruction of the graphite structure, affecting the battery's rate and cycle performance. However, the above-mentioned embodiments of the present application utilize the synergistic effect of the polymer and the ether organic solvent to greatly improve the rate performance and cycle performance of the secondary battery.

[0072] In some embodiments, the ether organic solvent includes one or more of ethylene glycol dimethyl ether (DME), ethylene glycol diethyl ether (DEE), tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether (TTE), polyethylene glycol dimethyl ether (PEGDME), and crown ether. This can further improve the rate performance, cycle performance, and safety performance of the secondary battery.

[0073] In some embodiments, the sulfone organic solvent includes one or more of dimethyl sulfoxide (DMSO), phenethyl sulfone, diethyl sulfone, diphenyl sulfone, sulfolane, and bisphenol S. This can further improve the high voltage stability, cycle performance, and safety performance of the secondary battery. Bisphenol S is also known as 4,4'-dihydroxydiphenyl sulfone.

[0074] In some embodiments, the carbonate organic solvent includes one or more of ethylene carbonate (EC), propylene carbonate (PC), fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), and diethyl carbonate (DEC). This can further improve the cycle performance and wide temperature range performance of the secondary battery.

[0075] In some embodiments, the phosphate organic solvent includes one or more of trimethyl phosphate (TMP), triethyl phosphate (TEP), and tripropyl phosphate (TPP). This can further improve the flame retardancy and safety performance of the secondary battery.

[0076] In some embodiments, the carbon-containing material includes one or more of artificial graphite, natural graphite, soft carbon, hard carbon, and a silicon-carbon composite material.

[0077] In some embodiments, the electrolyte salt includes one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium bis(oxalatoborate) (LiBOB), lithium difluorooxalatoborate (LiDFOB), lithium difluorobis(oxalatophosphate) (LiDFOP), lithium difluorophosphate (LiPO2F2), lithium hexafluoroantimonate (LiSbF6), lithium hexafluoroarsenate (LiAsF6), lithium bis(trifluoromethylsulfonyl)imide (LiN(SO2CF3)2), lithium bis(pentafluoroethylsulfonyl)imide (LiN(SO2C2F5)2), tris(trifluoromethylsulfonyl)methyl lithium (LiC(SO2CF3)3), and lithium bis(fluorosulfonyl)imide (LiN(SO2F)2).

[0078] In some embodiments, the gel electrolyte further includes an additive, and the additive includes one or more of fluoroethylene carbonate (FEC), vinylene carbonate (VC), lithium difluorooxalatoborate (LiODFB), lithium difluorophosphate (LiPO2F2), vinyl sulfate (DTD), 1,3-propane sultone (1,3-PS), tris(trimethylsilane) phosphate, tris(trimethylsilane) borate, propene sultone, fluorobenzene, vinyl ethylene carbonate and lithium nitrate (LiNO3).

[0079] In some embodiments, the negative electrode sheet further comprises a conductive agent and a binder. Optionally, the conductive agent includes, but is not limited to, one or more of carbon nanotubes, graphene, and carbon black. Optionally, the binder includes, but is not limited to, one or more of polyvinylidene fluoride binders, rubber binders, and sodium carboxymethyl cellulose binders.

[0080] In some embodiments, the secondary battery further comprises a positive electrode sheet, wherein the positive electrode active material in the positive electrode sheet comprises one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium manganese oxide, lithium cobalt oxide, ternary materials, lithium nickel manganese oxide, lithium-rich manganese-based materials, sulfur-containing materials and their respective modified compounds. The above-mentioned ternary materials include the chemical formula LiNi x Co y Mn z O2 material, wherein x+y+z=1. The above-mentioned modified compound includes but is not limited to doping modification using one or more elements of Al, Zr, Mg, Ti, Si, and F. Optionally, the sulfur-containing material includes but is not limited to one or more of a sulfur positive electrode and a sulfur composite positive electrode, for example, a sulfur-carbon positive electrode, a sulfur-polyacrylonitrile composite positive electrode (SPAN), and the like.

[0081] In some embodiments, the secondary battery further comprises a separator. Optionally, the base film of the separator includes but is not limited to a polyethylene-based film, a polypropylene-based film, a polyimide-based film, and the like.

[0082] Another embodiment of the present application provides a method for preparing a secondary battery, comprising the following steps:

[0083] impregnating the negative electrode sheet with a gel electrolyte precursor comprising a polymer monomer, an organic solvent, and an electrolyte salt, and curing the gel electrolyte precursor to form a gel electrolyte;

[0084] The negative electrode sheet contains a negative electrode active material, which includes a carbon-containing material. The gel electrolyte includes a polymer formed by an organic solvent, an electrolyte salt and a polymer monomer. The organic solvent includes one or more of an ether organic solvent, a sulfone organic solvent, a sulfone organic solvent and a carbonate organic solvent. The polymer contains one or more of a carbon-oxygen double bond and a carbon-oxygen single bond. The mass proportion of the polymer in the gel electrolyte is 0.5% to 38%.

[0085] The above preparation method is simple to operate and easy to mass produce secondary batteries. The polymer containing at least one of a carbon-oxygen double bond and a carbon-oxygen single bond has a certain polarity and can react with Li + coordination, by inhibiting Li + The combination with the above-mentioned organic solvent molecules changes the Li +The solvation structure of the above-mentioned polymer is significantly inhibited from co-embedding the carbonaceous material with ether organic solvents, sulfone organic solvents and carbonate organic solvents; in addition, the mass proportion of the above-mentioned polymer in the gel electrolyte is controlled within a reasonable range, and the synergistic effect of the ether organic solvents, sulfone organic solvents, sulfone organic solvents and carbonate organic solvents with the above-mentioned polymers is utilized to improve the conductivity and wettability of the gel electrolyte, so that the rate performance and safety performance of the above-mentioned secondary battery are significantly improved, and the secondary battery has excellent cycle performance. In addition, in the above-mentioned preparation method, the gel electrolyte precursor can fully infiltrate the negative electrode sheet, which is conducive to the formation of a dense and sufficient solid-solid contact interface after subsequent curing, thereby providing rich Li + The mass transfer interface can further improve the rate performance and kinetic performance of secondary batteries.

[0086] In some embodiments, the secondary battery further comprises a positive electrode sheet and a separator; before the step of impregnating the negative electrode sheet with a gel electrolyte precursor comprising a polymer monomer, an organic solvent, and an electrolyte salt, the step further comprises: laminating or winding the positive electrode sheet, the separator, and the negative electrode sheet to form an electrode assembly;

[0087] After the step of forming the electrode assembly, a gel electrolyte precursor containing a polymer monomer, an organic solvent, and an electrolyte salt is used to impregnate the electrode assembly, and the gel electrolyte precursor is cured to form a gel electrolyte. It can be understood that the separator is located between the positive electrode sheet and the negative electrode sheet.

[0088] In the above embodiment, the sufficient infiltration of the gel electrolyte precursor into the positive electrode sheet and the negative electrode sheet is conducive to the formation of a dense and sufficient solid-solid contact interface after subsequent curing, thereby providing rich Li + The mass transfer interface further improves the rate performance and kinetic performance of the secondary battery. Optionally, the positive electrode active material in the positive electrode sheet includes one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium manganese oxide, lithium cobalt oxide, ternary materials, lithium nickel manganese oxide, lithium-rich manganese-based materials, sulfur-containing materials and their respective modified compounds. The above-mentioned ternary materials include the chemical formula LiNi x Co y Mn z O2 materials, wherein x+y+z=1. The modified compounds include but are not limited to those modified by doping with one or more elements selected from the group consisting of Al, Zr, Mg, Ti, Si, and F.

[0089] In some embodiments, the gel electrolyte precursor further comprises an initiator. Optionally, the initiator comprises one or more of AIBN (azobisisobutyronitrile), AMBN (azobisisovaleronitrile), AVBN (azobisisoheptanenitrile), ACVA (azobiscyanovaleric acid), BPO (dibenzoyl peroxide), and AAPH (azobisisobutyramidine hydrochloride).

[0090] In some embodiments, the method of curing the gel electrolyte precursor includes one or more of thermal initiation and ultraviolet light initiation. Optionally, the curing temperature is 20° C. to 100° C., and the curing time is 2 hours to 48 hours.

[0091] Another embodiment of the present application provides an electrical device comprising at least one of the secondary battery described above and the secondary battery produced by the preparation method described above. The electrical device may include any device or apparatus powered by a battery, such as, but not limited to, a mobile phone, a laptop computer, an electric vehicle, a ship, a satellite, an energy storage device, or a smart home appliance.

[0092] The electrical device of the present application includes at least one of the secondary battery provided in the present application and the secondary battery prepared by the preparation method provided in the present application, and thus has at least the same advantages as the secondary battery or the preparation method.

[0093] To further illustrate the present application, the technical solutions of the present application are described in detail below with reference to specific examples. Where specific techniques or conditions are not specified in the examples, the techniques or conditions described in the literature in the art or in accordance with the product instructions were used. Reagents or instruments used, for which the manufacturer is not specified, are all commercially available conventional products.

[0094] Example 1

[0095] 1) Preparation of liquid electrolyte:

[0096] Organic solvents (ethylene carbonate (EC) and ethylene glycol dimethyl ether (DME)) are mixed with lithium salt (LiPF6) to obtain a liquid electrolyte, wherein the mass ratio of the two organic solvents is EC:DME = 1:2, and the mass proportion of lithium salt in the liquid electrolyte is 13%.

[0097] 2) Preparation of gel electrolyte precursor:

[0098] After the prepared liquid electrolyte is evenly mixed with 15% mass fraction (mass percentage of polymer monomer in the gel electrolyte precursor) of polymer monomer, 1wt% (mass percentage of polymer monomer) of crosslinker PEGDMA and 0.5wt% of free radical initiator AIBN (azoisobutylonitrile) (mass percentage of polymer monomer) are added to obtain a gel electrolyte precursor, the polymer monomer is methyl methacrylate (MMA), and the polymer in the gel electrolyte precursor is polymethyl methacrylate (PMMA).

[0099] 3) Preparation of positive electrode materials:

[0100] The positive electrode active materials NCM811 (LiNi 0.8 Co 0.1 Mn 0.1 O2), conductive carbon black Super-P and binder polyvinylidene fluoride (PVDF), which are then dispersed in N-methyl-2-pyrrolidone (NMP) to obtain a positive electrode slurry. The slurry is evenly coated on both surfaces of the aluminum foil in the thickness direction. After drying, rolling and vacuum drying, and welding aluminum lead wires with an ultrasonic welder, a positive electrode sheet is obtained. The thickness of the positive electrode sheet is between 120 and 150 μm. The loading capacity of the positive electrode active material is about 17.5 mg / cm 2 .

[0101] 4) Preparation of negative electrode materials:

[0102] The negative electrode active material, artificial graphite, conductive carbon black Super-P, and binders styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC), were mixed in a mass ratio of 94:1:2.5:2.5 and then dispersed in deionized water to produce a negative electrode slurry. The slurry was coated on both surfaces of the copper foil in the thickness direction, dried, rolled, and ultrasonically welded with nickel lead wires to form a negative electrode sheet. The double-sided coating weight of the negative electrode sheet was 19.8 mg / cm 2 , compacted density is 1.65g / cm 3 .

[0103] 5) Preparation of battery cells:

[0104] A polyethylene microporous membrane with a thickness of 20 μm is placed between the positive electrode sheet and the negative electrode sheet as a separator. The sandwich structure consisting of the positive electrode sheet, the negative electrode sheet and the separator is then wound. The wound body is flattened and placed in an aluminum-plastic film. After the positive and negative electrode lead wires are led out respectively, the aluminum-plastic film is hot-pressed and sealed to obtain a battery cell to be injected with liquid.

[0105] 6) Injection and in-situ polymerization of battery cells:

[0106] In a glove box maintained at a dew point below -40°C, the prepared gel electrolyte precursor was injected into the battery cell at a rate of 2.5g / Ah. After the gel precursor fully soaked the cell, it was clamped with a clamp and then placed in an oven at 60°C for 8 hours to polymerize, resulting in a fully cured gel battery.

[0107] 7) Battery formation:

[0108] Charge at 0.05C constant current for 180min, charge at 0.1C constant current for 180min, leave it for 24h, then shape and seal it, then further charge at 0.2C constant current to 4.2V, leave it at room temperature for 24h, and discharge at 0.2C constant current to 3.0V.

[0109] Examples 2-7

[0110] The process is basically the same as Example 1, except that in step 2), when preparing the gel electrolyte precursor, the mass fraction of the polymer monomer MMA is changed, as specifically described in Table 1.

[0111] Examples 8-10

[0112] The process is basically the same as Example 1, except that: in step 1), when preparing the liquid electrolyte, an equal amount of carbonate organic solvent is used to replace the ether organic solvent DME in Example 1, as described in Table 1.

[0113] The carbonate organic solvent used in Example 8 is dimethyl carbonate (DMC), the carbonate organic solvent used in Example 9 is ethyl methyl carbonate (EMC), and the carbonate organic solvent used in Example 10 is diethyl carbonate (DEC).

[0114] Examples 11-13

[0115] The method is basically the same as Example 1, except that: in step 1), when preparing the liquid electrolyte, the type of organic solvent is changed, as described in Table 2;

[0116] The organic solvent in Example 11 is propylene carbonate (PC) and ethyl methyl carbonate (EMC) in a mass ratio of 1:2, the organic solvent in Example 12 is ethylene carbonate (EC) and trimethyl phosphate (TMP) in a mass ratio of 1:2, and the organic solvent in Example 13 is ethylene carbonate (EC) and dimethyl sulfoxide (DMSO) in a mass ratio of 1:2.

[0117] Comparative Example 1

[0118] The process was essentially the same as Example 1, except that step 2) was omitted and step 6) was replaced by: In a glove box maintained at a dew point below -40°C, the liquid electrolyte prepared in step 1) of Example 1 was injected into the battery cell at a rate of 2.5 g / Ah. After the liquid electrolyte fully soaked the cell, it was clamped with a heavy duty clamp and then placed in an oven at 60°C for 8 hours to produce a battery, as described in Table 1.

[0119] Comparative Examples 2-3

[0120] The process is basically the same as Example 1, except that in step 2), when preparing the gel electrolyte precursor, the mass fraction of the polymer monomer MMA is changed, as specifically described in Table 1.

[0121] Comparative Examples 4-6

[0122] The process was essentially the same as Example 1, except that the type of organic solvent was changed during the preparation of the liquid electrolyte in step 1), step 2) was omitted, and step 6) was replaced by injecting the prepared liquid electrolyte into the battery cell in a glove box maintained at a dew point below -40°C at a rate of 2.5 g / Ah. After the liquid electrolyte fully soaked the cell, it was clamped with a heavy-duty clamp and then placed in an oven at 60°C for 8 hours to produce a battery, as described in Table 2.

[0123] Comparative Example 7

[0124] The process is essentially the same as Example 1, except that: Step 1) a commercial liquid electrolyte is selected, wherein the composition of the commercial liquid electrolyte is an organic solvent with a mass ratio of EC:DMC = 1:2 and a lithium salt (LiPF6) of 1 mol / L; Step 2) is omitted; and Step 6) is replaced by: In a glove box with a dew point controlled below -40°C, the commercial liquid electrolyte is injected into the battery cell at a rate of 2.5 g / Ah. After the liquid electrolyte fully soaks the battery cell, the cell is clamped with a heavy duty clamp and then placed in an oven at 60°C for 8 hours to obtain a battery.

[0125] Performance Testing

[0126] (1) First coulombic efficiency and first charge-discharge curve

[0127] During the battery formation step, the charge capacity is recorded as Q1, the discharge capacity as Q2, and the initial coulombic efficiency as Q1 / Q2. These performance parameters reflect the extent of side reactions between the electrolyte and the electrodes during the initial charge. The charge and discharge curves during the battery formation step are the battery's initial charge and discharge curves.

[0128] (2) Capacity retention after 300 cycles

[0129] At 30°C, the formed battery was charged at a constant current of 0.5C to 4.2V, then charged at a constant voltage until the current dropped to 0.05C, and then discharged at a constant current of 1C to 2.8V. This cycle was repeated for 300 cycles, and the discharge capacity at the 300th cycle was recorded.

[0130] Capacity retention (%) = (discharge capacity at the 300th cycle / initial nominal capacity of the battery) × 100%. Here, the initial nominal capacity of the battery is 1700 mAh.

[0131] (3) 2C specific capacity

[0132] At 30°C, the formed battery was charged to 4.2V at a constant current of 0.5C, then charged at a constant voltage until the current dropped to 0.05C, and then charged at 2C (2C = 7.5mA / cm 2) was discharged at a constant current to 2.8 V, and the battery discharge capacity Q3 was recorded. Q3 was divided by the mass of all positive electrode active materials to obtain the battery specific capacity at 2C.

[0133] (4) Graphite co-embedding degree

[0134] At 30°C, the formed battery was charged to 4.2V at a constant current of 0.5C, then charged at a constant voltage until the current dropped to 0.05C, and transferred to a glove box with a pure argon atmosphere for full-charge disassembly. The fully charged graphite negative electrode was photographed, and its surface color and morphology were observed.

[0135] If the graphite shows a full golden matte appearance and there is no obvious damage or powdering of the graphite material, it is recorded as "non-co-embedded";

[0136] If the graphite shows a full golden matte appearance and the graphite material is slightly damaged and powdered, it will be recorded as "slight co-embedding";

[0137] If the graphite is not full golden yellow, or is mostly black or coppery, and the graphite material is severely damaged and powdered, it will be recorded as "severe co-embedding".

[0138] (5) Rate performance

[0139] At 30°C, the formed battery was charged to 4.2V at 0.2C constant current, then charged at constant voltage until the current dropped to 0.05C, and then charged at 0.2C, 0.5C, 1C, and 2C (1C = 3.75mA / cm 2 ) to 2.8V, and record the battery discharge capacity at different rates. After each discharge, use 0.2C constant current and constant voltage to fully charge to 4.2V, with a cutoff current of 0.05C to prepare for the next discharge.

[0140] (6) DC internal resistance (DCIR)

[0141] After the battery SOC is adjusted to 50% and reaches steady state, charge / discharge with 0.1C / 0.1C (I1), 0.5C / 0.5C (I2), and 1C / 1C (I3) for 10 seconds each, and record the instantaneous voltage U1, U2, and U3 after 10 seconds of each charge and discharge. Three groups of corresponding data are obtained, namely (U1, I1), (U2, I2), and (U3, I3). These three points are linearly fitted, and the slope obtained is DCIR.

[0142] The battery performance test results of each embodiment and comparative example are shown in Table 1 and Table 2. In Table 1 and Table 2, “ / ” indicates that the parameter does not exist.

[0143] Table 1

[0144] Table 2

[0145] From Table 1 and Table 2, we can see the following:

[0146] It can be found from Examples 1-7 and Comparative Examples 1-3 that when the mass proportion of polymer PMMA in the gel electrolyte is 0.5% to 38%, PMMA competes with DME for Li coordination, resulting in Li + It does not carry DME molecules into the graphite interlayer, thus maintaining good charge and discharge performance. However, when the mass proportion of polymer PMMA in the gel electrolyte reaches 40% or even 60%, although it can still inhibit the co-embedding of DME, the extremely low liquid content and conductivity bring about large internal resistance and polarization, resulting in battery failure during 2C discharge.

[0147] Through Examples 1 and 8-10, it can be found that when the mass proportion of the polymer PMMA in the gel electrolyte is 15%, and the ether organic solvent DME in the electrolyte solvent component is replaced by linear carbonates DMC, EMC, and DEC, the cycle performance and 2C specific capacity of the battery will be affected to a certain extent. This is due to the lower dielectric constant and weaker lithium salt dissociation ability of the linear carbonate. At the same time, since the above-mentioned linear carbonate does not have the ultra-low viscosity of DME, it is not sufficient to form a sufficient solid-solid interface during the battery infiltration and curing process, resulting in a larger overall internal resistance, so it does not have the relatively excellent cycle performance and rate discharge performance of Example 1.

[0148] 1-2 , it can be found from Example 1 and Comparative Example 7 that the synergistic combination of the polymer PMMA of Example 1 and the ether organic solvent DME can significantly improve the rate performance of the battery and reduce the internal resistance of the battery.

[0149] In addition, a needle puncture safety test was conducted on the batteries of Examples 1-10 and Comparative Examples 1-3. It was found that the batteries of Examples 1-6 did not catch fire, explode, or emit smoke within 5 minutes of puncture, and only experienced a temperature increase. The batteries of Example 7 experienced mild combustion and no explosion within 5 minutes of puncture. The batteries of Examples 8-10 experienced no fire, explosion, or smoke within 5 minutes of puncture, and only experienced a temperature increase. This indicates that the batteries of Examples 1-10 exhibit excellent safety performance. The battery of Comparative Example 1 experienced a severe explosion within 5 minutes of puncture. The batteries of Comparative Examples 2-3 experienced no fire, explosion, or smoke within 5 minutes of puncture, and only experienced a temperature increase.

[0150] Combined with Figures 3-5, it can be found from Examples 11-13 and Comparative Examples 4-6 that in highly polar electrolytes such as PC, TMP, and DMSO, when the polymer PMMA accounts for 15% by mass in the gel electrolyte, it can alleviate its damage to the graphite structure. In Comparative Examples 4-6, PC and DMSO have the greatest degree of damage to graphite, resulting in the battery being completely destroyed during the first cycle of charging, and the polarization is too large during the first discharge, resulting in no Li + It can be released, and the discharge capacity is zero, while the liquid electrolyte based on TMP can only release a capacity of 70.4 mAh / g; and it can be seen from Examples 11-13 that when the mass proportion of polymer PMMA in the gel electrolyte is 15%, it can release a higher capacity and provide a higher first coulombic efficiency than its liquid counterpart, indicating that PMMA can inhibit the damage of strong polar organic solvents such as PC, TMP, and DMSO to the graphite structure to a certain extent.

[0151] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0152] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A secondary battery, which includes a negative electrode sheet and a gel electrolyte. The negative electrode sheet contains a negative electrode active material, and the negative electrode active material includes a carbon-containing material. The gel electrolyte includes a polymer, an organic solvent, and an electrolyte salt. The organic solvent includes one or more of an ether organic solvent, a sulfone organic solvent, a phosphate organic solvent, and a carbonate organic solvent. The polymer contains one or more of a carbon-oxygen double bond and a carbon-oxygen single bond, and the mass ratio of the polymer in the gel electrolyte is 0.5% to 38%.

2. The secondary battery according to claim 1, wherein, The mass ratio of the polymer in the gel electrolyte is 5% to 30%, and can be optionally 7% to 20%.

3. The secondary battery according to any one of claims 1 to 2, wherein, The polymer includes a homopolymer or copolymer of one or more monomer units having the structures shown in Formula I to Formula III: Wherein, M1 includes any one of a substituted or unsubstituted carbonyl group and a substituted or unsubstituted ether group, and M2 and M3 each independently include any one of a substituted or unsubstituted amide group, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkoxy group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aryl group, a substituted or unsubstituted heteroaryl group, a substituted or unsubstituted heteroalkyl group, a substituted or unsubstituted heterocyclic group, a substituted or unsubstituted amino group, a substituted or unsubstituted alkylene group, a substituted or unsubstituted alkenylene group, and a substituted or unsubstituted arylalkyl group. 1 ≤ n1 ≤ 10, 1 ≤ n2 ≤ 10, 1 ≤ n3 ≤ 10, and * represents a bonding site.

4. The secondary battery according to any one of claims 1 to 3, wherein, The polymer includes one or more of polyacrylate compounds, polyethylene oxide and its homologues.

5. The secondary battery according to claim 4, wherein, The polyacrylate compounds include one or more of polymethyl methacrylate, polybutyl acrylate, poly(methyl acrylate), and poly(ethylene glycol) diacrylate.

6. The secondary battery according to any one of claims 1 to 5, wherein, The ether organic solvents include one or more of ethylene glycol dimethyl ether, ethylene glycol diethyl ether, tetrafluoroethyl-2,2,3,3-tetrafluoropropyl ether, polyethylene glycol dimethyl ether, and crown ether.

7. The secondary battery according to any one of claims 1 to 6, wherein, The sulfone organic solvents include one or more of dimethyl sulfoxide, phenyl ethyl sulfone, diethyl sulfone, diphenyl sulfone, sulfolane, and bisphenol S.

8. The secondary battery according to any one of claims 1 to 7, wherein, The phosphate organic solvents include one or more of trimethyl phosphate, triethyl phosphate, and tripropyl phosphate.

9. The secondary battery according to any one of claims 1 to 8, wherein, The carbonate organic solvents include one or more of ethylene carbonate, propylene carbonate, fluorinated ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate, and diethyl carbonate.

10. The secondary battery according to any one of claims 1 to 9, wherein, The carbon-containing material includes one or more of artificial graphite, natural graphite, soft carbon, hard carbon, and silicon-carbon composite materials.

11. The secondary battery according to any one of claims 1 to 10, wherein, The electrolyte salts include one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(oxalato)borate, lithium difluoro(oxalato)borate, lithium difluorodioxalato phosphate, lithium difluorophosphate, lithium hexafluoroantimonate, lithium hexafluoroarsenate, lithium bis(trifluoromethanesulfonyl)imide, lithium bis(pentafluoroethylsulfonyl)imide, lithium tris(trifluoromethylsulfonyl)methyl, and lithium bis(fluorosulfonyl)imide.

12. The secondary battery according to any one of claims 1 to 11, wherein, The gel electrolyte further includes an additive, and the additive includes one or more of fluoroethylene carbonate, vinylene carbonate, lithium difluoro(oxalato)borate, lithium difluorophosphate, ethylene sulfate, 1,3 - propanesultone, tris(trimethylsilyl) phosphate, tris(trimethylsilyl) borate, propene sultone, fluorobenzene, vinyl ethylene carbonate, and lithium nitrate.

13. The secondary battery according to any one of claims 1 to 12, wherein, It further includes a positive electrode sheet, and the positive electrode active material in the positive electrode sheet includes one or more of lithium iron phosphate, lithium manganese iron phosphate, lithium manganate, lithium cobaltate, ternary materials, lithium nickel manganese oxide, lithium - rich manganese - based materials, sulfur - containing materials, and their respective modified compounds.

14. A method for preparing a secondary battery, which includes the following steps: Using a gel electrolyte precursor containing a polymer monomer, an organic solvent, and an electrolyte salt to infiltrate a negative electrode sheet, and curing the gel electrolyte precursor to form a gel electrolyte; The negative electrode sheet contains a negative electrode active material, the negative electrode active material includes a carbon - containing material, the gel electrolyte includes a polymer formed by the organic solvent, the electrolyte salt, and the polymer monomer, the organic solvent includes one or more of ether - type organic solvents, sulfone - type organic solvents, phosphate - type organic solvents, and carbonate - type organic solvents, the polymer includes one or more of carbon - oxygen double bonds and carbon - oxygen single bonds, and the mass ratio of the polymer in the gel electrolyte is 0.5% - 38%.

15. The preparation method according to claim 14, wherein The secondary battery further includes a positive electrode sheet and a separator; before the step of using a gel electrolyte precursor containing a polymer monomer, an organic solvent, and an electrolyte salt to infiltrate the negative electrode sheet, it further includes: laminating or winding the positive electrode sheet, the separator, and the negative electrode sheet to form an electrode assembly; After the step of forming the electrode assembly, using the gel electrolyte precursor containing the polymer monomer, the organic solvent, and the electrolyte salt to infiltrate the electrode assembly, and curing the gel electrolyte precursor to form the gel electrolyte.

16. An electrical device, which includes at least one of the secondary batteries described in any one of claims 1 to 13 and the secondary batteries prepared by the preparation method described in any one of claims 14 to 15.

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