Secondary battery, gel electrolyte precursor solution, preparation method, and electric device

Abstract

The present application relates to a secondary battery, a gel electrolyte precursor solution, a preparation method, and an electric device. The secondary battery comprises a gel electrolyte, wherein the gel electrolyte comprises a first gel electrolyte inside an electrode active material layer and a second gel electrolyte outside an electrode sheet; the first gel electrolyte and the second gel electrolyte each independently comprise a cross-linked polymer, a gelling solvent and an electrolyte salt; the cross-linked polymer comprises a carbon-based chain segment; and the gel electrolyte comprises a polymerization inhibition residue.

Description

Secondary battery, gel electrolyte precursor, preparation method and power device

[0001] Related applications

[0002] This application claims priority to Chinese patent application number CN2024103086900, filed on March 18, 2024, entitled “Secondary battery, gel electrolyte precursor, preparation method and electrical device,” the entire text of which is hereby incorporated by reference. Technical Field

[0003] The present application relates to the technical field of secondary batteries, and further to a secondary battery, a gel electrolyte precursor, a preparation method, and an electrical device. Background Art

[0004] The statements herein merely provide background information related to the present application and do not necessarily constitute prior art.

[0005] With the popularity and development of various electronic products such as smartphones, tablets, smart wearables, power tools and electric vehicles, the application of secondary batteries has been involved in all aspects of people's daily life. How to improve the capacity and cycle performance of secondary batteries is of great significance to improving the performance of secondary batteries. Summary of the Invention

[0006] In view of this, according to various embodiments and examples of the present application, the present application provides at least one secondary battery, a gel electrolyte precursor, a preparation method, and an electrical device. The secondary battery has excellent capacity utilization and cycle performance.

[0007] In a first aspect of the present application, a secondary battery is provided, which includes a gel electrolyte, the gel electrolyte including a first gel electrolyte located inside the electrode active material layer and a second gel electrolyte located outside the electrode pole piece; the first gel electrolyte and the second gel electrolyte each independently include a cross-linked polymer, a gelling solvent and an electrolyte salt; the cross-linked polymer includes a carbon-based chain segment; and the gel electrolyte includes an inhibitor residue.

[0008] In some embodiments, a secondary battery is provided, comprising a plurality of electrode sheets; the plurality of electrode sheets include a positive electrode sheet and a negative electrode sheet; any of the electrode sheets independently includes an electrode active material layer;

[0009] The secondary battery includes a gel electrolyte, the gel electrolyte including a first gel electrolyte and a second gel electrolyte, the first gel electrolyte being located inside the electrode active material layer, and the second gel electrolyte being located outside the plurality of electrode sheets; wherein the first gel electrolyte and the second gel electrolyte each independently include a cross-linked polymer, a gelling solvent, and an electrolyte salt;

[0010] The cross-linked polymer includes carbon-based chain segments; the gel electrolyte includes an inhibitory residue, which is a substance generated by an inhibitor after inhibiting a free radical polymerization reaction; and the inhibitor includes an inhibitory group capable of terminating the free radical polymerization reaction.

[0011] The secondary battery has a gel electrolyte fully distributed in the electrode plate. The gel electrolyte can be formed by a gel electrolyte precursor containing an inhibitor, which is then solidified after being infiltrated into the electrode plate and formed. At this time, there may be inhibitor residues in the secondary battery. The inhibitory effect of the inhibitor can be used to inhibit the curing reaction during the infiltration of the electrode plate and the formation stage, thereby controlling the occurrence time of the curing reaction, improving the infiltration effect of the gel electrolyte precursor on the inside of the electrode plate, thereby promoting the gel electrolyte precursor to be fully distributed inside the electrode plate, which is beneficial to promoting the precursor to fully contact and infiltrate with the electrode active particles, and promoting the solidified gel electrolyte to fully contact the electrode active material inside the electrode plate, thereby optimizing the transmission channel of the active ions, thereby promoting the capacity of the positive electrode plate, the negative electrode plate and the battery cell, and also beneficial to suppressing the problem of lithium precipitation at the negative electrode interface and improving the cycle performance of the battery.

[0012] In some embodiments, the mass fraction of the polymerization inhibition residue in the gel electrolyte is 50 ppm to 2000 ppm, and can be optionally 500 ppm to 1000 ppm.

[0013] The content of inhibitor residues in the gel electrolyte is mainly related to the amount of inhibitor used in the preparation process. By controlling the mass fraction of inhibitor residues in the gel electrolyte within the aforementioned range, it is beneficial to better control the start time of the curing reaction, to obtain a better wetting effect, to promote a more complete distribution of the gel electrolyte inside the electrode plate, and to be more conducive to the rapid transmission of active ions inside the electrode plate, which is conducive to achieving better capacity utilization and cycle performance.

[0014] In some embodiments, the inhibitory residue includes a quinone residue of a phenolic inhibitor; wherein the phenolic inhibitor includes an aromatic ring and a phenolic hydroxyl group directly bonded to the aromatic ring; in one molecule of the phenolic inhibitor, the inhibitory group includes one or more phenolic hydroxyl groups.

[0015] In some embodiments, the phenolic polymerization inhibitor includes one or more of the following compounds: phenol, 2,6-di-tert-butylphenol, p-methoxyphenol, 2,6-di-tert-butyl-4-methylphenol, hydroquinone, catechol, 2-nitrohydroquinone, monomethyl hydroquinone, trimethyl hydroquinone, p-tert-butylcatechol, 2,5-di-tert-butylhydroquinone, bisphenol A, 4,4'-dihydroxybiphenyl, 4,4'-butylenebis(6-tert-butyl-3-methylphenol), pyrogallol and 4-bromophenol.

[0016] Phenol polymerization inhibitors are free radical polymerization inhibitors that have a wide range of inhibitory effects on various free radical polymerization monomers. They have good inhibitory effects on polymerization monomers such as acrylates and styrenes, and can quench free radicals generated by the decomposition of initiators.

[0017] In some embodiments, the cross-linked polymer comprises repeating units formed by free radical polymerization of polymerizable monomers; the polymerizable monomers comprise polyene compounds and may or may not comprise monoene compounds, wherein the polyene compounds have multiple polymerizable carbon-carbon double bonds and the monoene compounds have one polymerizable carbon-carbon double bond;

[0018] Optionally, the polyene compound includes one or more of ethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,4-butanediol diacrylate, glycerol dimethacrylate, 1,2-propylene glycol dimethyl acrylate, 1,3-butanediol dimethacrylate, dipropylene glycol diacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, glycerol trimethacrylate, triallyl trimesic acid ester, cyclohexanetriol trimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate and pentaerythritol tetramethacrylate.

[0019] Different monomers can be flexibly selected based on the structural requirements of the cross-linked polymer in the gel electrolyte. These monomers include polyene compounds, and the cross-linked polymer has a network-like cross-linking structure, which gives the gel electrolyte a physical form that combines the solidity of a gel skeleton with the restricted mobility of a gelling solvent. The introduction of monoene compounds allows the distance between adjacent cross-links in the network structure to be adjusted, thereby adjusting the flexibility of the gel electrolyte.

[0020] In some embodiments, the electrode active material layer in the positive electrode sheet is referred to as a positive electrode active material layer, and the electrode active material layer in the negative electrode sheet is referred to as a negative electrode active material layer;

[0021] The volume of the gel electrolyte in the positive electrode active material layer is denoted as V P1 The volume and porosity of the positive electrode active material layer are respectively denoted as V P2 and definition

[0022] The volume of the gel electrolyte in the negative electrode active material layer is denoted as V N1 The volume and porosity of the negative electrode active material layer are respectively denoted as V N2 and definition

[0023] Among them, α P and α N Each independently greater than or equal to 0.85;

[0024] Optionally, α P and α N are each independently greater than or equal to 0.9.

[0025] In some embodiments, the secondary battery includes a separator located between the positive electrode sheet and the negative electrode sheet, and the positive electrode sheet, the negative electrode sheet, and the separator constitute an electrode assembly;

[0026] The α of the positive electrode active material layer located at the innermost side of the electrode assembly P Denoted as α P0 , the α of the negative active material layer located at the innermost side of the electrode assembly N Denoted as α N0 ;

[0027] Among them, α P0 and α N0 Each independently greater than or equal to 0.85;

[0028] Optionally, α P0 and α N0 are each independently greater than or equal to 0.9.

[0029] The degree of distribution of the gel electrolyte in the electrode plate can be measured by the filling factor α P and α N To reflect, α P and α N The higher the value, the more fully the gel electrolyte is distributed inside the electrode plate and the higher the degree of contact with the electrode active material.

[0030] For the electrode assembly, the farther away from the outer surface of the electrode assembly or the closer to the innermost side of the electrode assembly, the more difficult it is for the gel electrolyte precursor to wet the electrode plate. Therefore, the filling factor α of the innermost side of the electrode assembly isP0 and α N0 The higher it is, the more fully the gel electrolyte is distributed inside the electrode sheets in the secondary battery.

[0031] In a second aspect of the present application, a gel electrolyte precursor solution is provided, which includes the following components: a free radical polymerization system, an inhibitor, an electrolyte salt, and an electrolyte solvent;

[0032] The free radical polymerization system includes a polymerizable monomer and an initiator, wherein the initiator can initiate a free radical polymerization reaction of the polymerizable monomer to form a cross-linked polymer; and the inhibitor includes an inhibitory group that can terminate the free radical polymerization reaction of the free radical polymerization system.

[0033] The aforementioned secondary battery including the gel electrolyte can be formed by using the gel electrolyte precursor solution provided in the second aspect of the present application, through impregnation of the electrode, formation and curing.

[0034] In some embodiments, the gel electrolyte precursor satisfies one or more of the following characteristics:

[0035] The mass percentage of the polymerizable monomer in the gel electrolyte precursor solution is 2% to 15%, and can be optionally 8% to 12%;

[0036] The mass fraction of the polymerization inhibitor in the gel electrolyte precursor solution is 50 ppm to 2000 ppm, and can be optionally 500 ppm to 1000 ppm.

[0037] By adjusting the mass percentage of the polymerized monomer in the gel electrolyte precursor solution within the aforementioned range, it is advantageous to provide a relatively stable gel structure while taking into account the transport capability of active ions.

[0038] Adjusting the mass fraction of the inhibitor in the gel electrolyte precursor solution is beneficial to providing sufficient inhibition effect while minimizing the addition amount.

[0039] In some embodiments, the polymerization inhibitor comprises a phenolic polymerization inhibitor; wherein the phenolic polymerization inhibitor comprises an aromatic ring and a phenolic hydroxyl group directly bonded to the aromatic ring; in one molecule of the phenolic polymerization inhibitor, the polymerization inhibitor group comprises one or more phenolic hydroxyl groups.

[0040] In some embodiments, the phenolic polymerization inhibitor satisfies one or more of the following characteristics:

[0041] In one molecule, the phenolic polymerization inhibitor contains 1 to 5 phenolic hydroxyl groups;

[0042] In one molecule, the mass proportion of the phenolic hydroxyl group in the phenolic polymerization inhibitor is 7.5% to 40.5%;

[0043] In one molecule, the phenolic polymerization inhibitor contains one or more aromatic rings; when the number of the aromatic rings is multiple, adjacent aromatic rings are connected by chemical bonds or -C(R1R2)-, wherein R1 and R2 are each independently H or C 1-4 alkyl;

[0044] The molecular weight of the phenolic polymerization inhibitor is less than or equal to 1000 Da.

[0045] In some embodiments, the phenolic polymerization inhibitor satisfies one or more of the following characteristics:

[0046] In one molecule, the phenolic polymerization inhibitor contains 1, 2 or 3 phenolic hydroxyl groups;

[0047] In one molecule, the mass proportion of the phenolic hydroxyl group in the phenolic polymerization inhibitor is 8% to 35%;

[0048] In one molecule, the phenolic polymerization inhibitor contains 1 or 2 aromatic rings; when the number of the aromatic rings is multiple, adjacent aromatic rings are connected by chemical bonds or -C(R1R2)-, wherein R1 and R2 are each independently H or C 1-3 Alkyl, and -C(R1R2)- has 1 to 4 carbon atoms;

[0049] The molecular weight of the phenolic polymerization inhibitor is less than or equal to 500 Da.

[0050] By controlling one or both of the number of phenolic hydroxyl groups contained in the phenolic inhibitor and the mass proportion of phenolic hydroxyl groups in the phenolic inhibitor within the aforementioned range, the inhibition time and the inhibition efficiency can be adjusted, and a more sufficient inhibition effect can be achieved with a more appropriate dosage of the phenolic inhibitor.

[0051] The number of sites for introducing phenolic hydroxyl groups can be adjusted by controlling the number of aromatic rings.

[0052] By controlling the molecular weight of the phenolic polymerization inhibitor within the aforementioned range, the steric hindrance effect can be reduced, thereby making it more conducive for the polymerization inhibitory group to exert its inhibitory effect.

[0053] In some embodiments, any aromatic ring of the phenolic polymerization inhibitor is independently connected with 0, 1 or more non-hydroxyl substituents selected from the group consisting of halogen, nitro, C 1-4 Alkyl and C 1-3 Alkoxy.

[0054] In some embodiments, any aromatic ring in the phenolic polymerization inhibitor is independently connected with 0, 1 or more non-hydroxy substituents selected from the following group: halogen and nitro; the halogen is selected from one or more of fluorine, chlorine and bromine.

[0055] In some embodiments, the phenolic polymerization inhibitor includes one or more of the following compounds: phenol, 2,6-di-tert-butylphenol, p-methoxyphenol, 2,6-di-tert-butyl-4-methylphenol, hydroquinone, catechol, 2-nitrohydroquinone, monomethyl hydroquinone, trimethyl hydroquinone, p-tert-butylcatechol, 2,5-di-tert-butylhydroquinone, bisphenol A, 4,4'-dihydroxybiphenyl, 4,4'-butylenebis(6-tert-butyl-3-methylphenol), pyrogallol and 4-bromophenol.

[0056] In some embodiments, the gel electrolyte precursor satisfies one or more of the following characteristics:

[0057] The mass ratio of the initiator to the polymerization monomer is 0.5% to 10%, and can be optionally 0.5% to 5%;

[0058] The mass ratio of the polymerization inhibitor to the initiator is 0.1% to 50%, and can be optionally 0.1% to 20%;

[0059] The mass ratio of the polymerization inhibitor groups in the polymerization inhibitor to the initiator is 0.01% to 15%, and can be optionally 0.05% to 5%.

[0060] By controlling the mass ratio of the initiator to the polymerization monomer within the aforementioned range, the polymerization monomer is facilitated to fully react and more fully participate in the gelation structure.

[0061] By controlling one or both of the mass ratio of the polymerization inhibitor to the initiator and the mass ratio of the polymerization inhibitor group in the polymerization inhibitor to the initiator within the aforementioned range, the polymerization inhibitor effect can be fully exerted before the start of the curing reaction (including in the wetting and formation stages), and it is also beneficial to control the amount of by-products introduced, and the initiation effect of the initiator can be fully exerted. The polymerization inhibitor can be consumed as quickly as possible during the curing reaction stage, thereby starting the curing reaction as quickly as possible, and it is also beneficial to reduce or avoid residual polymerization monomers, thereby reducing the adverse effects of the reaction between the residual monomers and the electrode on the electrochemical properties of the battery.

[0062] In some embodiments, the gel electrolyte precursor satisfies one or more of the following characteristics:

[0063] The polymerizable monomer includes a polyene compound and may include or exclude a monoene compound, wherein the polyene compound has a plurality of polymerizable carbon-carbon double bonds and the monoene compound has one polymerizable carbon-carbon double bond;

[0064] The initiator includes one or more of an azo initiator and a peroxide initiator.

[0065] In some embodiments, the gel electrolyte precursor satisfies one or more of the following characteristics:

[0066] The structure of the polyene compound is [CH2=C(R 01 )-] k U1, k is an integer greater than or equal to 2, U1 is a k-valent non-aromatic group or a k-valent aromatic group; R 01 Each occurrence is independently H or methyl;

[0067] The polymerizable monomers include monoolefin compounds, and the monoolefin compounds include CH2=C(R0)-R A 、 One or more of; R0 is H or methyl; R A -COOH, -C(=O)-O-R3, -CH(-OR 41 )(-OR 42 ), cyano or phenyl; R3 is C 1-6 Alkyl, substituted C 1-6 Alkyl, tri(C 1-6 Hydrocarbon)silyl or tri(C 1-6 Hydrocarbyloxy)silyl; R 41 and R 42 Each independently is C 1-3 Alkyl; the substituted C 1-6 C in the alkyl group 1-6 The alkyl group is substituted with one or more substituents selected from the group consisting of -OH, halo, epoxy, and cyano;

[0068] The initiator includes an azo initiator, and the azo initiator includes one or more of azobisisobutyronitrile, dimethyl azobisisobutyrate and azobisisoheptanenitrile;

[0069] The initiator includes a peroxide initiator, and the peroxide initiator includes one or more of didodecanoyl peroxide, dibenzamide peroxide, di(2,4-dichlorobenzoyl) peroxide, diacetyl peroxide, dioctanoyl peroxide, dilauroyl peroxide, peroxydicarbonate, diisopropyl peroxydicarbonate, diisobutyl peroxydicarbonate, dicyclohexyl peroxydicarbonate and di(p-tert-butylcyclohexyl) peroxydicarbonate.

[0070] In some embodiments, the structure of U1 is (-C(=O)-O-) k U0 or (-O-) k U0 or a k-valent aromatic group; wherein, U0 is connected to the adjacent oxygen atom through a carbon atom, and U0 is a k-valent alkyl group or a k-valent alkyl group containing one or more ether groups.

[0071] In some embodiments, the polymerizable monomer satisfies one or more of the following characteristics:

[0072] The polyene compound includes one or more of ethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,4-butanediol diacrylate, glycerol dimethacrylate, 1,2-propylene glycol dimethyl acrylate, 1,3-butanediol dimethacrylate, dipropylene glycol diacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, glycerol trimethacrylate, triallyl trimesic acid ester, cyclohexanetriol trimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate and pentaerythritol tetramethacrylate;

[0073] The monoolefin compound includes one or more of styrene, vinylene carbonate, vinyl ethylene carbonate, methyl methacrylate, methyl acrylate, ethyl acrylate, acrylic acid, trimethylsilyl methacrylate, acrolein dimethyl acetal, acrolein diethyl acetal, 2-phenoxyethyl acrylate, 3-perfluorohexyl-2-hydroxypropyl acrylate, trifluoroethyl acrylate, trifluoroethyl methacrylate, propenyl-1,3-sultone, glycidyl methacrylate, acrylamide, (acryloxymethyl) dimethylmethoxysilane, cyanoethyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, 3-(perfluoro-3-methylbutyl) 2-hydroxypropyl acrylate, pentafluorophenol acrylate and acrylonitrile;

[0074] The polymerizable monomer is an ester compound, and any ester structure in the ester compound is independently methyl ester, ethyl ester, propyl ester, trifluoroethyl ester, trimethylsilyl ester, 2-phenoxyethyl ester, glycidyl ester, cyanoethyl ester, hydroxyethyl ester, hydroxypropyl ester or pentafluorophenol ester.

[0075] In some embodiments, at 45° C., the polymerization inhibitor inhibits the free radical polymerization system for a time greater than or equal to 1200 min;

[0076] At 70° C., the initiator can initiate the free radical polymerization system to perform a free radical polymerization reaction within 600 minutes.

[0077] In a third aspect of the present application, a method for preparing a secondary battery is provided, comprising the following steps:

[0078] Providing an electrode assembly located inside the housing, the electrode assembly comprising a plurality of electrode sheets and a separator, the plurality of electrode sheets comprising a positive electrode sheet and a negative electrode sheet, the positive electrode sheet and the negative electrode sheet being separated by the separator; each of the electrode sheets independently comprising an electrode active material layer;

[0079] Injecting the gel electrolyte precursor solution described in the second aspect of the present application into the interior of the housing, and maintaining the temperature at an infiltration temperature T1 to allow the gel electrolyte precursor solution to infiltrate the plurality of electrode plates;

[0080] Performing chemical formation at a chemical formation temperature T2;

[0081] The gel electrolyte precursor solution is subjected to a free radical polymerization reaction at a curing temperature T3 to generate a gel electrolyte, thereby preparing a secondary battery; wherein the gel electrolyte includes a first gel electrolyte located inside the electrode active material layer and a second gel electrolyte located outside the plurality of electrode plates, the first gel electrolyte and the second gel electrolyte each independently including a cross-linked polymer formed by the polymerized monomer, a gelling solvent, and at least a portion of the electrolyte salt, and the gelling solvent includes at least a portion of the electrolyte solvent.

[0082] By utilizing the inhibitory effect of the polymerization inhibitor contained in the gel electrolyte precursor, the curing reaction can be suppressed during the electrode plate wetting and formation stages, thereby controlling the occurrence time of the curing reaction and improving the wetting effect of the gel electrolyte precursor on the inside of the electrode plate, thereby promoting the full distribution of the gel electrolyte precursor inside the electrode plate, promoting the full contact and infiltration of the precursor and the electrode active particles, optimizing the transmission channel of the active ions, thereby promoting the capacity of the positive electrode plate, the negative electrode plate and the battery cell, and also helping to suppress the problem of lithium plating at the negative electrode interface and improve the cycle performance of the battery.

[0083] In some embodiments, the method for preparing a secondary battery satisfies one or more of the following characteristics:

[0084] The electrolyte salt in the gel electrolyte precursor solution includes an electrolyte lithium salt;

[0085] The curing temperature T3 is higher than the soaking temperature T1;

[0086] The curing temperature T3 is higher than the formation temperature T2;

[0087] The soaking temperature T1 is 10°C to 60°C;

[0088] The formation temperature T2 is 40°C to 60°C;

[0089] The curing temperature T3 is 50°C to 80°C;

[0090] In the step of maintaining the temperature at the infiltration temperature T1 so that the gel electrolyte precursor solution infiltrates the plurality of electrode sheets, the infiltration time is 24 hours to 48 hours;

[0091] In the step of subjecting the gel electrolyte precursor solution to a free radical polymerization reaction at a curing temperature T3 to generate a gel electrolyte, the reaction time of the free radical polymerization reaction is 3 hours to 8 hours;

[0092] The secondary battery described in the first aspect of the present application is prepared.

[0093] In another aspect of the present application, a secondary battery is provided, which is the secondary battery described in the first aspect of the present application, or a secondary battery prepared by the preparation method of the secondary battery described in the third aspect of the present application, and the secondary battery is a lithium-ion secondary battery.

[0094] In a fourth aspect of the present application, an electrical device is provided, comprising 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 third aspect of the present application.

[0095] The details of one or more embodiments and examples of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0096] In order to better describe and illustrate the embodiments, examples, or examples provided in this application, reference may be made to one or more of the accompanying drawings. The additional details or examples used to describe the accompanying drawings should not be considered as limiting the scope of the disclosed application, the embodiments, examples, or examples currently described, and any of the best modes currently understood for these applications. In addition, the same reference numerals are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0097] FIG1 is a schematic diagram of a battery cell according to an embodiment of the present application.

[0098] FIG. 2 is an exploded view of the battery cell according to one embodiment of the present application shown in FIG. 1 .

[0099] FIG3 is a schematic diagram of a battery module according to an embodiment of the present application.

[0100] FIG4 is a schematic diagram of a battery pack according to an embodiment of the present application.

[0101] FIG5 is an exploded view of the battery pack shown in FIG4 according to an embodiment of the present application.

[0102] FIG6 is a schematic diagram of an electric device using a secondary battery as a power source according to an embodiment of the present application.

[0103] Explanation of the accompanying symbols: 1, battery pack; 2, upper box; 3, lower box; 4, battery module; 5, battery cell; 51, shell; 52, electrode assembly; 53, cover plate; 6, electrical device. DETAILED DESCRIPTION

[0104] Below, some embodiments and examples of the secondary battery, gel electrolyte precursor, preparation method and electrical device of the present application are described in detail with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structure are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following description are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0105] " scope " disclosed in the present application can be limited in the form of lower limit and upper limit, and given range is limited by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of special range. The scope limited in this way can be to include end value or not include end value, and any end value can be included or not included independently, and can be arbitrarily combined, that is, any lower limit can form a scope with any upper limit combination. For example, if the scope of 60-120 and 80-110 is listed for specific parameters, it is understood that the scope of 60-110 and 80-120 is also expected. In addition, if minimum range values ​​1 and 2 are listed, and if maximum range values ​​3,4 and 5 are also listed, then the following scope can all be expected: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In the present application, unless otherwise specified, numerical range " ab " represents the abbreviation of any real number combination between a and b, wherein a and b are all real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" are listed herein, and "0-5" is merely an abbreviation for these numerical combinations. Furthermore, when a parameter is expressed as an integer ≥ 2, this is equivalent to listing the parameter as, for example, the integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, and so on. For example, when a parameter is expressed as an integer selected from "2-10", this is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0106] In this application, unless otherwise specified, "about" means within a reasonable range above and below the number, and the fluctuation range may vary depending on the type and value of the number. For example, a range of ±10%, ±5%, ±2%, ±1%, etc. may be allowed. For example, taking "about 20°C" and its approximate value of ±1°C as an example, the approximate values ​​of 19°C, 19.5°C, etc. within the approximate range of "about 20°C" should also be included in the range indicated by "about 20°C". For example, when "about 500Da" means ±10Da, the corresponding fluctuation range is also included in the range of "about 500Da".

[0107] In this application, unless otherwise specified, reference to a "numerical value" includes the number itself and its reasonable approximations. The definition of the "numerical value" may apply to discrete numerical points as well as to the endpoints of a numerical range. In this application, whenever a numerical value or a numerical range is involved, unless otherwise specified, it should be understood that the numerical value covers its reasonable approximations, and the numerical range covers the reasonable approximations of the two endpoints. Those skilled in the art will understand that the acceptable fluctuation range of the relevant approximations can be included in the definition of the numerical value or the numerical range. In this application, unless otherwise specified, "N1" may be reasonably understood as "about N1", and "N1-N2" may be reasonably understood as "about N1 to about N2", wherein N1 and N2 are two unequal numerical values. For example, in some cases, due to one or more factors such as reasonable deviations allowed in the art, instrument control accuracy, etc., it is reasonable to include the approximate values ​​within the approximate range into the range defined by the numerical range; for example, "the temperature is 20°C to 30°C" can be understood as "about 20°C to about 30°C"; further, taking the endpoint "20°C" and its approximate number is ±1°C as an example, the approximate values ​​of 19°C, 19.5°C, etc. within the approximate range of "about 20°C" should also be included in the range indicated by 20°C to 30°C. As a non-limiting example, the percentage content "10%" can be reasonably understood as "about 10%". As another non-limiting example, the percentage content "2% to 10%" can be reasonably understood as "about 2% to about 10%". As another non-limiting example, the percentage content "0%" at least includes "none" and can also include the situation of "below the detection limit".

[0108] In this application, references to "multiple," "multiple," "multiple," "several," and the like, unless otherwise specified, refer to a quantity greater than or equal to two. For example, "one or more" means one or ≥ (greater than or equal to) two. It is understood that references to "any number" of items refer to any suitable combination of multiple items, i.e., any combination of "any number" of items that is not in conflict and that enables the implementation of this application.

[0109] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0110] References to "embodiments" herein mean that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment or implementation of the present application. The appearance of such phrases in various locations in the specification does not necessarily refer to the same embodiment, nor does it necessarily refer to independent or alternative embodiments that are mutually exclusive with other embodiments. It is understood, both explicitly and implicitly, by those skilled in the art that the embodiments described herein may be combined with other embodiments. References to "implementations" herein have a similar understanding.

[0111] Those skilled in the art will appreciate that, in the methods of each embodiment or embodiment, the order in which each step is written does not mean a strict order of execution and constitutes any limitation to the implementation process, and the detailed order of execution of each step should be determined by its function and possible inherent logic. Unless otherwise specified, all steps of the present application can be performed in sequence, or can be performed randomly, or can preferably be performed in sequence. For example, method M includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed in sequence, or steps (b) and (a) performed in sequence. For example, method M may also include step (c), indicating that step (c) can be added to method M in any order, for example, method M may include steps (a), (b) and (c), or steps (a), (c) and (b), or steps (c), (a) and (b), etc.

[0112] In this application, in open technical features or technical solutions described with words such as "contain," "include," and "include," unless otherwise specified, additional members other than the listed members are not excluded, and it can be regarded as providing both closed features or solutions consisting of the listed members and open features or solutions including additional members in addition to the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or not. It can be regarded as providing both the feature or solution of "A consists of a1, a2, and a3" or "A is selected from a1, a2, and a3", and the feature or solution of "A includes not only a1, a2, and a3, but also other members."

[0113] In this application, unless otherwise specified, A (such as B) means that B is a non-limiting example of A, and it can be understood that A is not limited to B.

[0114] In this application, "optionally," "optional," and "optional" mean optional, that is, they refer to either option selected from the two parallel options of "yes" or "no." If multiple "options" appear in a technical solution, unless otherwise specified and there are no contradictions or mutual constraints, each "optional" is independent. Unless otherwise specified, the descriptions "optionally include," "optionally include," etc. in this application, using "optionally include" as an example, mean "may include or not include."

[0115] In this application, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more relevant listed items, and also include any and all combinations of the relevant listed items, wherein any and all combinations include any two relevant listed items, any more relevant listed items, or a combination of all relevant listed items. For example, "A and / or B" means a group consisting of A, B, and "a combination of A and B." Among them, "including A and / or B" can mean "including A, including B, and including A and B", and can also mean "including A, including B, or including A and B", which can be appropriately understood according to the sentence in which it is used.

[0116] As used herein, "combination thereof", "any combination thereof", "any combination thereof" and the like include all suitable combinations of any two or more of the listed items.

[0117] Herein, the word “suitable” in “suitable combination”, “suitable method”, “any suitable method”, etc., shall be based on the technical solution that can implement the present application.

[0118] Herein, the terms "preferred," "better," "more preferable," "suitable," "comparatively better," and "preferable" are used solely to describe preferred implementations or examples and should not be construed as limiting the scope of protection of this application. If multiple "preferred" terms appear in a technical solution, each "preferred" term is considered independent unless otherwise specified and there are no contradictions or mutual constraints.

[0119] In this application, "further", "further", "particularly", "for example", "such as", "example", "for example", etc. are used for descriptive purposes to indicate differences in content, but should not be understood as limiting the scope of protection of this application.

[0120] In this application, the terms "first," "second," "third," "fourth," etc. in "the first aspect," "the second aspect," "the third aspect," "the fourth aspect," etc. are used for descriptive purposes only and should not be understood as indicating or implying relative importance or quantity, nor should they be understood as implicitly indicating the importance or quantity of the indicated technical features. Furthermore, "first," "second," "third," "fourth," etc. serve only as non-exhaustive enumeration and description, and should be understood not to constitute a closed-ended limitation on quantity.

[0121] In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may mean that the first and second features are in direct contact, or that the first and second features are in indirect contact through an intermediary. In this application, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may refer to a relative horizontal positional relationship, or may simply refer to an attachment relationship without limiting the relative horizontal positional relationship.

[0122] In this application, the term "room temperature" generally refers to 4°C to 35°C, and may refer to 20°C ± 5°C. In some embodiments or examples of this application, room temperature refers to 20°C to 30°C.

[0123] In this application, when referring to a data range, if the unit is followed only by the right endpoint, it means that the units of the left and right endpoints are the same. For example, "3~5h" or "3-5h" both mean that the units of the left endpoint "3" and the right endpoint "5" are both hours, and both have the same meaning as "3h~5h". Similarly, descriptions of other parameters such as temperature and size are to be understood in the same manner.

[0124] The weight or mass of the relevant components mentioned in the embodiments or examples of the present application can not only refer to the content of each component, but also represent the proportional relationship of weight or mass between each component. Therefore, as long as the content of the relevant components in accordance with the embodiments or examples of the present application is proportionally enlarged or reduced, it is within the scope described in the present application. Further, the mass involved in the embodiments or examples of the present application can be mass units known to the chemical industry such as micrograms (μg), milligrams (mg), grams (g), kilograms (kg). Unless otherwise specified, the mass ratio is equal to the corresponding weight ratio, such as the mass of substance A is m1 and the weight is W1, the mass of substance B is m2 and the weight is W2, then the mass ratio m1 / m2 of the two is numerically equal to the corresponding weight ratio W1 / W2.

[0125] In this application, unless otherwise specified, wt% represents weight percentage by weight and is numerically equivalent to the corresponding mass percentage by mass. In this application, when a weight percentage is represented by "0", it has the same meaning as "0wt%" and can be used interchangeably.

[0126] In this application, "greater than or equal to", "greater than or equal to", and "≥" have the same meaning and can be used interchangeably; "less than or equal to", "less than or equal to", and "≤" have the same meaning and can be used interchangeably; "greater than" can be equivalently expressed as ">", and "less than" can be equivalently expressed as "<". In this application, unless otherwise specified, "greater than or equal to" and "≥" can be regarded as providing two solutions of "greater than" and "equal to". In this application, unless otherwise specified, "less than or equal to" and "≤" can be regarded as providing two solutions of "less than" and "equal to".

[0127] In this application, exemplary descriptions such as "in some embodiments (or examples)" and "in one embodiment (or example)" may include but are not limited to the following meanings: these solutions can be combined with other solutions in a suitable manner to form new technical solutions.

[0128] In this application, unless otherwise specified, the term "alkyl" refers to a monovalent residue formed by the loss of one hydrogen atom from a saturated hydrocarbon containing a primary (normal) carbon atom, a secondary carbon atom, a tertiary carbon atom, a quaternary carbon atom, or a combination thereof. Phrases containing this term, such as "C 1-6 "Alkyl" refers to an alkyl group containing 1 to 6 carbon atoms, which can be independently C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl or C6 alkyl at each occurrence. 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(CH3)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 (-CH(CH3)2CH2CH 2CH3), 3-methyl-2-pentyl (-CH(CH3)CH(CH3)CH2CH3), 4-methyl-2-pentyl (-CH(CH3)CH2CH(CH3)2), 3-methyl-3-pentyl (-C(CH3)(CH2CH3)2), 2-methyl-3-pentyl (-CH(CH2CH3)CH(CH3)2), 2,3-dimethyl-2-butyl (-C(CH3)2CH(CH3)2) and 3,3-dimethyl-2-butyl (-CH(CH3)C(CH3)3.

[0129] In this application, unless otherwise specified, the term "alkoxy" refers to a group of the structure -O-alkyl, which is an alkyl group as defined above connected to an adjacent group via an oxygen atom. Phrases containing this term, such as "C 1-6 "Alkoxy" means an alkyl moiety containing 1 to 6 carbon atoms, which at each occurrence can be independently C1 alkoxy, C2 alkoxy, C3 alkoxy or C4 alkoxy, C5 alkoxy or C6 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).

[0130] In this application, for atoms, groups, or compound residues that participate in forming a covalent bond, its valence refers to the number of attachment sites of the atom, group, or compound residue that participates in forming a covalent bond. For example, the valence of an alkyl group (-CH3) is monovalent, and the valence of an alkylene group (-CH2-) is divalent. For another example, the valence of groups such as -OH, -CH3, and -CN is monovalent, and the valence of -CH2- and -O- is divalent. For those skilled in the art, it is understood that this "valence" is different from the charge state of an ion.

[0131] As used herein, "halogen" or "halo" refers to F, Cl, Br or I, unless otherwise specified.

[0132] In the present application, unless otherwise specified, the electrode plate can be a positive electrode plate or a negative electrode plate, and the "active material" in the electrode plate refers to a substance that can reversibly embed and release active ions. Unless otherwise specified, "negative electrode active material" refers to a substance used for the negative electrode plate that can reversibly embed and release active ions, also known as a negative electrode active material; "positive electrode active material" refers to a substance used for the positive electrode plate that can reversibly release and embed active ions, also known as a positive electrode active material. When the secondary battery is charging, the active ions are released from the positive electrode and embedded in the negative electrode through the electrolyte; when the secondary battery is discharging, the active ions are released from the negative electrode and embedded in the positive electrode. The active ions are not particularly limited and can be lithium ions. Without limitation, the active ions can be lithium ions, and the secondary battery in this case is a lithium-ion secondary battery.

[0133] In this application, "electrode active material", "electrode active substance", "active material" and "active substance" have the same meaning and can be used interchangeably; "positive electrode active substance" and "positive electrode active material" have the same meaning and can be used interchangeably; "negative electrode active substance" and "negative electrode active material" have the same meaning and can be used interchangeably. "Positive electrode active substance" and "positive electrode active material" have the same meaning and can be used interchangeably; "negative electrode active substance" and "negative electrode active material" have the same meaning and can be used interchangeably.

[0134] In this application, unless otherwise specified, an "active material layer" includes at least one of the positive electrode active material layer of a positive electrode sheet and the negative electrode active material layer of a negative electrode sheet. Depending on the specific circumstances, it can refer to either the positive electrode active material layer or the negative electrode active material layer. It is understood that the positive electrode active material layer contains a positive electrode active material, and the negative electrode active material layer contains a negative electrode active material. In this application, an "electrode active material layer" may also be referred to as an "active material layer."

[0135] By introducing gel electrolytes into secondary batteries, traditional liquid electrolytes are converted into gel state, which is beneficial for fixing the electrolyte and inhibiting electrolyte leakage, and can improve the reliability and cycle life of the battery. It is a secondary battery with great potential. Regarding the introduction of gel electrolytes, a precursor solution is often prepared by adding a gelation reaction system containing a polymerized monomer to the electrolyte, and then the precursor solution is subjected to an in-situ curing reaction to convert the precursor solution into a gel electrolyte. In order to achieve smooth transmission of active ions in the positive and negative electrode sheets during charging and discharging, it is necessary to fully infiltrate the interior of the positive and negative electrode sheets before curing, so that the cured gel electrolyte contacts the electrode active materials inside the positive and negative electrode sheets. The larger the battery cell, the longer the required infiltration time is often, and sometimes high temperature conditions are required for infiltration. Non-limitingly, when introducing gel electrolytes into large soft-pack batteries, hard-shell batteries or high-capacity batteries, a longer infiltration time and high temperature infiltration conditions are usually required to achieve a better infiltration effect. In addition, the battery formation process also usually needs to be carried out under high temperature conditions. However, a long soaking time and high temperature conditions may trigger the curing reaction of the gelation reaction system, which may lead to the problem of premature curing before the in-situ curing reaction process is started. The gel formed by premature curing will hinder the further infiltration of the precursor liquid into the electrode plate, resulting in insufficient infiltration of the precursor liquid into the electrode plate, and then the gel electrolyte formed after curing is incompletely distributed within the electrode plate, which will lead to reduced battery capacity and lithium precipitation at the negative electrode interface (taking the active ions as lithium ions as an example), which will worsen the battery cycle performance. Regarding the problem of lithium precipitation at the negative electrode interface, taking the active ions as lithium ions as an example, it may be that some of the negative electrode active materials inside the negative electrode plate cannot be fully infiltrated by the precursor liquid, resulting in poor contact with the gel electrolyte, and then the negative electrode plate cannot fully accept lithium ions from the positive electrode. The excess lithium ions are deposited on the negative electrode surface to form lithium metal. The lithium metal formed on the negative electrode surface will further react with the electrolyte to form a solid electrolyte interface (SEI) film, consuming the electrolyte, thereby reducing the cycle stability of the battery cell. In addition, during the high-temperature formation stage, the process of forming the SEI film will generate a certain amount of heat. If the battery cell does not dissipate heat in time (for example, the heat dissipation of large battery cells may not be ideal), the battery cell temperature will further increase, which may easily trigger an in-situ curing reaction of the precursor liquid, affecting the SEI film formation and the electrochemical performance of the battery.

[0136] Based on this, according to various embodiments and examples of the present application, the present application provides at least one secondary battery, a gel electrolyte precursor, a preparation method, and an electrical device. The secondary battery has excellent capacity utilization and cycle performance.

[0137] In a first aspect of the present application, a secondary battery is provided, which includes a gel electrolyte, the gel electrolyte including a first gel electrolyte located inside the electrode active material layer and a second gel electrolyte located outside the electrode pole piece; the first gel electrolyte and the second gel electrolyte each independently include a cross-linked polymer, a gelling solvent and an electrolyte salt; the cross-linked polymer includes a carbon-based chain segment; and the gel electrolyte includes an inhibitor residue.

[0138] In some embodiments, a secondary battery is provided, comprising a plurality of electrode sheets; the plurality of electrode sheets include a positive electrode sheet and a negative electrode sheet; any electrode sheet independently includes an electrode active material layer;

[0139] The secondary battery includes a gel electrolyte, the gel electrolyte including a first gel electrolyte and a second gel electrolyte, the first gel electrolyte being located inside the electrode active material layer, and the second gel electrolyte being located outside the plurality of electrode plates; wherein the first gel electrolyte and the second gel electrolyte each independently include a cross-linked polymer, a gelling solvent, and an electrolyte salt;

[0140] The cross-linked polymer includes carbon-based chain segments; the gel electrolyte includes an inhibitory residue, which is a substance generated after the inhibitor inhibits a free radical polymerization reaction; the inhibitor includes an inhibitory group capable of terminating the free radical polymerization reaction.

[0141] The secondary battery provided in the present application is a battery including a gel electrolyte.

[0142] In this application, a "gel electrolyte" is a semi-solid electrolyte having the following characteristics: it comprises a gel skeleton, a gelling solvent located within the gel skeleton region, and an electrolyte salt dissolved in the gelling solvent. The gel skeleton is a cross-linked polymer with a three-dimensional network structure. The gelling solvent is bounded within the mesh of the gel skeleton and cannot flow freely, resulting in the electrolyte in the gel skeleton region being a gel-like semi-solid state. The electrolyte salt is dissolved in the gelling solvent and cannot migrate freely throughout the entire gel electrolyte region, but can move over short distances within the confined space of the gel skeleton mesh. Furthermore, the gelling solvent has a certain degree of continuous distribution within the gel skeleton, allowing the gel electrolyte to still conduct active ions. Furthermore, the molecular segments between adjacent crosslinks in the gel skeleton still have a certain degree of flexibility, giving the network structure not only a certain degree of support but also a certain degree of elasticity. However, the segments between these crosslinks are confined between the corresponding nodes of the mesh and cannot diffuse freely in the solvent like free molecules. Therefore, in terms of physical form, the gel electrolyte combines the solidity of the gel skeleton with the restricted fluidity of the gelling solvent, significantly different from traditional electrolytes that are free-flowing and have no fixed shape.

[0143] Traditional electrolytes are liquid electrolytes, also called liquid electrolytes, which include electrolyte salts and solvents. The solvent can flow freely, and the electrolyte salts dissolved in the solvent can migrate freely. The liquid electrolyte as a whole can flow freely and has no fixed shape.

[0144] It can be understood that the mobility of the electrolyte salt in the gel electrolyte is lower than that in the liquid electrolyte.

[0145] In the context of this application, the terms "first" and "second" in "first gel electrolyte" and "second gel electrolyte" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features.

[0146] In this application, "cross-linked polymer" has the well-known meaning in the field of polymer technology. It has a three-dimensional network structure and can produce a certain degree of swelling in the corresponding solvent, but will not dissolve. The degree of swelling depends on the degree of cross-linking of the cross-linked polymer.

[0147] In this application, unless otherwise specified, a "carbon-based segment" refers to a segment composed of carbon atoms, which can be formed by free radical polymerization of unsaturated carbon-carbon double bonds.

[0148] In this application, unless otherwise specified, "inhibitor residue" refers to a substance generated after the polymerization inhibitor inhibits free radical polymerization, and "inhibitor" includes an inhibitory group that can terminate the free radical polymerization reaction. The inhibitor can quench free radicals by containing inhibitory groups, thereby forming an inhibition residue. Among them, the "substance generated after the polymerization inhibitor inhibits free radical polymerization" is generally a by-product of the gelation reaction system that forms the gel electrolyte. For the gelation reaction system in this application, those skilled in the art can usually infer the type and structure of the inhibitor based on the structure of the inhibition residue. The definition of the inhibitor can also be found in the context of this application.

[0149] The secondary battery has a gel electrolyte fully distributed in the electrode plate. The gel electrolyte can be formed by a gel electrolyte precursor containing an inhibitor, which is then solidified after being infiltrated into the electrode plate and formed. At this time, there may be inhibitor residues in the secondary battery. The inhibitory effect of the inhibitor can be used to inhibit the curing reaction during the infiltration of the electrode plate and the formation stage, thereby controlling the occurrence time of the curing reaction, improving the infiltration effect of the gel electrolyte precursor on the inside of the electrode plate, thereby promoting the gel electrolyte precursor to be fully distributed inside the electrode plate, which is beneficial to promoting the precursor to fully contact and infiltrate with the electrode active particles, and promoting the solidified gel electrolyte to fully contact the electrode active material inside the electrode plate, thereby optimizing the transmission channel of the active ions, thereby promoting the capacity of the positive electrode plate, the negative electrode plate and the battery cell, and also beneficial to suppressing the problem of lithium precipitation at the negative electrode interface and improving the cycle performance of the battery.

[0150] In the context of this application, the weight, volume, element distribution and other parameters of the gel electrolyte at different locations can be tested and analyzed based on focused electron beam (FIB) technology, scanning electron microscope (SEM) technology and elemental analysis technology. For example, it can be combined with focused electron beam (FIB) continuous sectioning, cross-section SEM morphology observation, energy dispersive spectroscopy (EDS) element spectrum and three-dimensional reconstruction analysis software analysis. For example, a frozen focused ion beam (FIB) is used to finely slice the sample (the smallest scale can reach nanometer-scale thin slices) to separate the electrode active material layer or gel electrolyte sample. The morphology, structure and element distribution of each layer of the cross section can also be analyzed by scanning electron microscope SEM under FIB continuous sectioning. The three-dimensional structure of the sample can be reconstructed in combination with three-dimensional structure reconstruction software to estimate the mass and / or volume of the sample to be tested. The battery can be disassembled to obtain samples at different locations such as the electrode active material layer sample (including the first gel electrolyte) of the electrode plate and the second gel electrolyte sample outside the electrode plate, and then the weight, volume, element distribution and other parameters can be tested using the above method. As a non-limiting example, the above parameters may be tested and analyzed using a FEI Scios2 HiVac device.

[0151] In some embodiments, the mass fraction of the inhibition residue in the gel electrolyte can be, but is not limited to, 50 ppm to 2000 ppm, and can be optionally 500 ppm to 1000 ppm, or can be any of the following mass fractions or an interval consisting of any two of the following mass fractions: 50 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 800 ppm, 1000 ppm, 1200 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1800 ppm, 2000 ppm, etc.

[0152] In this application, percentages can be converted to ppm (parts per million), 1% = 10,000 ppm, for example, 0.2% = 2,000 ppm, 0.1% = 1,000 ppm, 0.01% = 100 ppm, 0.005% = 50 ppm, etc.

[0153] The content of inhibitor residues in the gel electrolyte is mainly related to the amount of inhibitor used in the preparation process. By controlling the mass fraction of inhibitor residues in the gel electrolyte within the aforementioned range, it is beneficial to better control the start time of the curing reaction, to obtain a better wetting effect, to promote a more complete distribution of the gel electrolyte inside the electrode plate, and to be more conducive to the rapid transmission of active ions inside the electrode plate, which is conducive to achieving better capacity utilization and cycle performance.

[0154] Traditional polymerization inhibitors are mainly used to preserve polymerization monomers. They are usually removed before use. For example, the polymerization monomers are added to the reaction vessel after being removed by alkali treatment (such as sodium hydroxide, potassium hydroxide, etc.). After pretreatment, the mass content of the polymerization inhibitor or polymerization inhibitor residue in the polymerization reaction system is extremely small, usually less than 10 ppm.

[0155] In some embodiments, the polymerization inhibitor residue comprises a quinone residue of a phenolic polymerization inhibitor; wherein the phenolic polymerization inhibitor comprises an aromatic ring and a phenolic hydroxyl group directly bonded to the aromatic ring. Further, in one molecule of the phenolic polymerization inhibitor, the polymerization inhibitor group may comprise one or more phenolic hydroxyl groups. Without limitation, in one molecule of the phenolic polymerization inhibitor, the polymerization inhibitor group comprises 1 to 4 phenolic hydroxyl groups, optionally 1 to 3 phenolic hydroxyl groups, for example, 1, 2, or 3 phenolic hydroxyl groups, and further 1 or 2 phenolic hydroxyl groups.

[0156] In this application, unless otherwise specified, "phenolic polymerization inhibitor" refers to a polymerization inhibitor containing at least one phenolic hydroxyl group. "Quinone residue of phenolic polymerization inhibitor" refers to a quinone product formed after quenching free radicals by a phenolic polymerization inhibitor.

[0157] In this application, unless otherwise specified, "phenolic hydroxyl group" refers to a hydroxyl group directly covalently bonded to an aromatic ring. In this application, unless otherwise specified, "aromatic ring" refers to a ring with aromatic properties, which may be a carbocyclic ring, but is not limited thereto. A non-limiting example of an aromatic carbocyclic ring is a benzene ring.

[0158] In some embodiments, the phenolic hydroxyl group is a hydroxyl group attached to a benzene ring.

[0159] In some embodiments, the polymerization inhibitor residues include quinone residues of a phenolic polymerization inhibitor.

[0160] In some embodiments, the phenolic polymerization inhibitor includes one or more of the following compounds: phenol, 2,6-di-tert-butylphenol, p-methoxyphenol, 2,6-di-tert-butyl-4-methylphenol, hydroquinone, catechol, 2-nitrohydroquinone, monomethylhydroquinone, trimethylhydroquinone, p-tert-butylcatechol, 2,5-di-tert-butylhydroquinone, bisphenol A, 4,4'-dihydroxybiphenyl, 4,4'-butylenebis(6-tert-butyl-3-methylphenol), pyrogallol and 4-bromophenol.

[0161] Phenolic polymerization inhibitors have a broad inhibitory effect on a variety of free radical polymerization monomers, particularly acrylates, styrenes, and other polymerization monomers. They can also quench free radicals generated by the decomposition of initiators. The appropriate inhibitor type can be selected based on the desired inhibition time and efficiency.

[0162] In some embodiments, the cross-linked polymer comprises repeating units formed by free radical polymerization of polymerizable monomers; the polymerizable monomers comprise polyene compounds and may or may not comprise monoene compounds, wherein the polyene compounds have multiple polymerizable carbon-carbon double bonds and the monoene compounds have one polymerizable carbon-carbon double bond;

[0163] Without limitation, the polyene compound may include, but is not limited to, one or more of ethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,4-butanediol diacrylate, glycerol dimethacrylate, 1,2-propylene glycol dimethyl acrylate, 1,3-butanediol dimethacrylate, dipropylene glycol diacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, glycerol trimethacrylate, triallyl trimesic acid ester, cyclohexanetriol trimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, and pentaerythritol tetramethacrylate.

[0164] In this application, unless otherwise specified, "polymerized monomer" refers to the polymerized monomer in the gelation reaction system used to form the gel electrolyte, and the polymerized monomer can form a cross-linked polymer through free radical polymerization. After the free radical polymerization reaction, the polymerized monomer is converted into a repeating unit in the cross-linked polymer.

[0165] In some embodiments, the molecular weight of the polymerized monomer may be less than or equal to 2000 Da, further less than or equal to 1000 Da, further less than or equal to 550 Da, further less than or equal to 500 Da, or any of the following molecular weights or an interval consisting of any two of the following molecular weights: 53 Da, 60 Da, 70 Da, 71 Da, 72 Da, 80 Da, 85 Da, 86 Da, 100 Da, 102 Da, 104 Da, 105 Da, 110 Da, 112 Da, 116 Da, 120 Da, 125 Da, 130 Da, 140 Da, 142 Da, 145 Da, 150 Da, 154 Da, 155 Da, 158 Da, 160 Da, 168 Da, 170 Da, 180 Da, 700 Da, 750 Da, 800 Da, 900 Da, 1000 Da, 1100 Da, 1200 Da, 1250 Da, 1300 Da, 1400 Da, 1500 Da, 1600 Da, 1800 Da, 2000 Da, etc., but are not limited to. In some embodiments, the molecular weight of the polymerizable monomer is selected from 100 Da to 2000 Da, and can also be selected from an interval consisting of any two molecular weights within this range (refer to the molecular weights between 100 Da and 2000 Da listed above).

[0166] In this application, the "molecular weight" of a compound, unless otherwise specified, refers to the molecular mass measured in Daltons (Da), where 1 Dalton is equal to 12 One-twelfth the mass of a C atom. Unless otherwise specified, the average molecular weight of a polymer is greater than or equal to (≥) 1000 Da. 1 kDa = 1000 Da. The average molecular weight of a substance (such as a polymer) with a polydisperse molecular weight may refer to the weight-average molecular weight unless otherwise specified.

[0167] In some embodiments, the polyene compound includes a polyethylene glycol segment -(OCH2CH2) nO-, unless otherwise specified, n is an integer greater than or equal to 2, optionally, n can be an integer from 2 to 20, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, etc. In some embodiments, n is an integer from 2 to 10, optionally an integer from 2 to 6, further optionally 2, 3, 4, 5 or 6, further optionally 2, 3 or 4. The polymerizable monomer can be a polyene compound or a monoene compound.

[0168] In this application, unless otherwise specified, "polyene compound" refers to a compound having multiple polymerizable carbon-carbon double bonds, and "monoene compound" refers to a compound having one polymerizable carbon-carbon double bond, where "polymerizable carbon-carbon double bond" means a carbon-carbon double bond capable of free radical polymerization. Repeating units formed by polyene compounds can participate in forming crosslinking points of a crosslinked polymer, while repeating units formed by monoene compounds can participate in forming linear segments between adjacent crosslinking points.

[0169] In some embodiments, the "polymerizable carbon-carbon double bond" is an alpha carbon-carbon double bond, which refers to a carbon-carbon double bond located at the end group. Non-limitingly, the polymerizable carbon-carbon double bond can be CH2=CH(R 01 )-,R 01 Each occurrence of R is independently H or methyl. 01 is H. In other embodiments, R 01 It is a methyl group.

[0170] Different monomers can be flexibly selected based on the structural requirements of the cross-linked polymer in the gel electrolyte. These monomers include polyene compounds, and the cross-linked polymer has a network-like cross-linking structure, which gives the gel electrolyte a physical form that combines the solidity of a gel skeleton with the restricted mobility of a gelling solvent. The introduction of monoene compounds allows the distance between adjacent cross-links in the network structure to be adjusted, thereby adjusting the flexibility of the gel electrolyte.

[0171] In some embodiments, the electrode active material layer in the positive electrode sheet is referred to as the positive electrode active material layer, and the electrode active material layer in the negative electrode sheet is referred to as the negative electrode active material layer;

[0172] The volume of the gel electrolyte in the positive electrode active material layer is denoted as V P1 , the volume and porosity of the positive electrode active material layer are respectively denoted as V P2 and definition

[0173] The volume of the gel electrolyte in the negative electrode active material layer is denoted as V N1 , the volume and porosity of the negative electrode active material layer are respectively denoted as VN2 and definition

[0174] Among them, α P and α N Each independently greater than or equal to 0.85;

[0175] Optionally, α P and α N are each independently greater than or equal to 0.9.

[0176] The degree of distribution of the gel electrolyte in the electrode plate can be measured by the filling factor α P and α N To reflect, α P Refers to the filling ratio of the gel electrolyte in the internal pores of the positive electrode active material layer, α N Refers to the filling ratio of the gel electrolyte in the internal pores of the negative electrode active material layer. P and α N The higher the value, the more fully the gel electrolyte is distributed inside the electrode plate and the higher the degree of contact with the electrode active material.

[0177] In some embodiments, the secondary battery includes a separator located between a positive electrode sheet and a negative electrode sheet, and the positive electrode sheet, the negative electrode sheet, and the separator constitute an electrode assembly;

[0178] The α-active material layer of the positive electrode located at the innermost side of the electrode assembly P Denoted as α P0 , the α of the negative active material layer located at the innermost side of the electrode assembly N Denoted as α N0 ;

[0179] Among them, α P0 and α N0 Each independently greater than or equal to 0.85;

[0180] Optionally, α P0 and α N0 are each independently greater than or equal to 0.9.

[0181] For the electrode assembly, the farther away from the outer surface of the electrode assembly or the closer to the innermost side of the electrode assembly, the more difficult it is for the gel electrolyte precursor to wet the electrode plate. Therefore, the filling factor α of the innermost side of the electrode assembly is P0 and α N0 The higher it is, the more fully the gel electrolyte is distributed inside the electrode sheets in the secondary battery.

[0182] In this application, the mass and volume of the gel electrolyte in the positive electrode active material layer can be denoted as M and P1 、VP1 The volume and porosity of the positive electrode active material layer can be denoted as V P2 、 The mass and volume of the gel electrolyte in the negative electrode active material layer can be denoted as M N1 、V N1 The volume and porosity of the negative electrode active material layer can be denoted as V N2 、 Further definition: Filling factor of gel electrolyte in the positive electrode active material layer Filling factor of gel electrolyte in negative electrode active material layer α P , α N The theoretical value range of α is 0 to 1. When the value is 0, there is no gel electrolyte in the electrode plate. When the value is 1, the electrode plate is completely filled. P , α N The higher the value of , the more fully the gel electrolyte is distributed inside the electrode plate.

[0183] In this application, unless otherwise specified, the following method can be used to prepare the electrode active material layer samples to be tested: discharge the secondary battery to the nominal lower limit voltage, then disassemble the battery cell to obtain the positive electrode sheet and the negative electrode sheet, and then extract the positive electrode active material layer samples to be tested and the negative electrode active material layer samples to be tested. The nominal lower limit voltage can be determined by conventional testing methods or according to the manufacturer's definition.

[0184] The relevant parameters of the local area of ​​the electrode active material layer (such as the mass M of the local area) can be obtained by focusing electron beam (FIB) technology, scanning electron microscope (SEM) testing and analysis, combined with focusing electron beam (FIB) continuous sectioning, energy dispersive spectroscopy (EDS) element spectrum and three-dimensional reconstruction analysis software. i and volume V i , the mass M of the gel electrolyte in the local area i1 and volume V i1 , the porosity of the local area ), and then obtain α P , α N The FEI Scios 2HiVac device can be used.

[0185] In this application, unless otherwise specified, α P , α N The fill factor can be calculated by selecting several local areas and then taking the average value as the test value. P , α N, several local regions with a certain transverse area can be selected at different transverse positions of the electrode active material layer, and the local regions at the selected transverse positions can be sliced ​​continuously along the thickness direction of the electrode active material layer. Based on the three-dimensional reconstruction results, the filling factor of the local region can be calculated. Filling factor α for different local areas i Take the average value as α P or α N The test value of i1 is the volume of gel electrolyte in the selected local area, V i is the volume of the selected local area, is the porosity of the selected local area.

[0186] In the present application, unless otherwise specified, “several local regions” may refer to at least 3, further such as at least 6, and further such as at least 9 local regions.

[0187] In the present application, unless otherwise specified, the “lateral direction” in “different lateral positions of the electrode active material layer” refers to a direction perpendicular to the thickness direction of the corresponding electrode active material layer.

[0188] For α P and α N , localized regions of the electrode active material layer may be selected at multiple radial locations in the electrode assembly; "multiple radial locations in the electrode assembly" refers to different locations in the electrode assembly from the inside out in three-dimensional space. "Multiple radial locations in the electrode assembly" may include at least two locations among the innermost and outermost portions of the electrode assembly, and locations intermediate between the innermost and outermost portions.

[0189] Taking the electrode assembly of the winding structure as an example, without limitation, they are stacked in the order of "separator-negative electrode sheet-separator-positive electrode sheet" and wound in the same direction around the winding axis to form a multi-layer assembly. From the winding axis to the outer surface of the multi-layer assembly, the negative electrode sheet and the positive electrode sheet are respectively wound into multiple circles. At this time, the positive electrode active material layer portion located in the innermost circle of the multi-layer assembly in the positive electrode sheet can correspond to the "positive electrode active material layer located on the innermost side of the electrode assembly", and the positive electrode active material layer portion located in the outermost circle of the multi-layer assembly can correspond to the "positive electrode active material layer located on the outermost side of the electrode assembly". The portion of the positive electrode active material layer between the inner and outermost circles may correspond to the "positive electrode active material layer located in the middle between the innermost and outermost sides of the multilayer assembly"; the portion of the negative electrode active material layer located in the innermost circle of the multilayer assembly in the negative electrode pole piece may correspond to the "negative electrode active material layer located in the innermost side of the electrode assembly", the portion of the negative electrode active material layer located in the outermost circle of the multilayer assembly may correspond to the "negative electrode active material layer located in the outermost side of the electrode assembly", and the portion of the negative electrode active material layer located between the innermost and outermost circles in the negative electrode pole piece may correspond to the "negative electrode active material layer located in the middle between the innermost and outermost sides of the multilayer assembly". The aforementioned "multilayer assembly" is an electrode assembly with a wound structure.

[0190] Taking a laminated electrode assembly as an example, a separator is provided between any adjacent positive and negative electrode sheets. The resulting laminate structure has a certain thickness along the stacking direction and a certain area in a direction perpendicular to the stacking direction. Therefore, the laminated electrode assembly has a certain volume in three-dimensional space. Furthermore, based on the distance from the outer three-dimensional contour of the laminate structure, the innermost, outermost, and intermediate portions between the innermost and outermost portions can be distinguished. For example, the "positive active material layer located at the innermost portion of the electrode assembly" may correspond to the thickness center along the stacking direction and the area center of the positive electrode sheet located at this thickness center; the "positive active material layer located at the outermost portion of the electrode assembly" may correspond to the extreme ends along the stacking direction and the area edges of the positive electrode sheets located at these extreme ends; the "negative active material layer located at the innermost portion of the electrode assembly" may correspond to the thickness center along the stacking direction and the area center of the negative electrode sheet located at this thickness center; and the "negative active material layer located at the outermost portion of the electrode assembly" may correspond to the extreme ends along the stacking direction and the area edges of the negative electrode sheets located at these extreme ends.

[0191] For α P0 and α N0 , then local areas of multiple electrode active material layers are selected on the innermost side of the electrode assembly.

[0192] In the present application, unless otherwise specified, a number of “local regions” selected at different lateral positions of the electrode active material layer may refer to at least 3, further such as at least 6, and further such as at least 9 local regions.

[0193] In a non-limiting manner, the “certain lateral area” in the “local region having a certain lateral area” may refer to a region greater than or equal to 16 μm. 2 , further such as greater than or equal to 25 μm 2 , further such as greater than or equal to 36μm 2 , further such as greater than or equal to 64μm 2 , further such as greater than or equal to 100μm 2 It can be understood that the local region corresponding to the selected transverse area can cover a plurality of relatively complete pores.

[0194] For a "local region of the electrode active material layer," a slice scan can be performed over the entire or partial thickness of the electrode active material layer within a selected transverse area. The thickness of each local region can be greater than or equal to 4 μm, further such as greater than or equal to 5 μm, further such as greater than or equal to 6 μm, further such as greater than or equal to 8 μm, and further such as greater than or equal to 10 μm.

[0195] In this application, unless otherwise specified, the porosity of the positive electrode active material layer is The average porosity of several (at least three, and further, for example, greater than or equal to 6) local areas in the positive electrode active material layer can be used as the test value. The test value may be an average value of the porosity of several (at least three, for example, greater than or equal to 6) local regions in the negative electrode active material layer.

[0196] In this application, unless otherwise specified, the mass M of the gel electrolyte inside the positive electrode sheet is P1 With volume V P1 , the volume of the positive electrode active material layer V P2 , the mass M of the gel electrolyte inside the negative electrode N1 With volume V P1 , the volume of the negative electrode active material layer V N2 The value can be obtained by selecting several (e.g., at least 3, further e.g., greater than or equal to 6) local areas to calculate the corresponding parameters, taking the average value, and then converting it into the mass, volume, thickness and other parameters of each part obtained by disassembling the battery cell and the proportional coefficient corresponding to the local area.

[0197] In some embodiments, any electrode plate independently includes a current collector and an electrode active material layer disposed on at least one side of the current collector.

[0198] In some embodiments, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector.

[0199] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a positive electrode active material layer disposed on at least one side of the negative electrode current collector.

[0200] The secondary battery provided in this application includes a battery cell.

[0201] In this application, unless otherwise specified, a "battery cell" refers to a basic unit that can achieve the mutual conversion of chemical energy and electrical energy. Further, generally speaking, it includes at least a positive electrode plate, a negative electrode plate, and an electrolyte. During the battery's charge and discharge process, active ions are embedded in and out of the positive and negative electrode plates. The electrolyte plays the role of conducting active ions between the positive and negative electrode plates.

[0202] In one embodiment of the present application, a secondary battery includes a positive electrode sheet, a negative electrode sheet, and an electrolyte, wherein the electrolyte includes at least the aforementioned gel electrolyte. During the battery's charge and discharge processes, active ions are intercalated and deintercalated between the positive and negative electrode sheets. The electrolyte functions to conduct active ions between the positive and negative electrode sheets.

[0203] In one embodiment of the present application, a secondary battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator, wherein the electrolyte includes at least the aforementioned gel electrolyte. During the battery charge and discharge process, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte has the function of conducting active ions between the positive electrode sheet and the negative electrode sheet. The separator is arranged between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through.

[0204] The types of active ions can be as described above.

[0205] The following is some description about the electrolyte in the secondary battery.

[0206] The electrolyte conducts ions between the positive electrode and the negative electrode. The electrolyte in the secondary battery provided herein includes at least the aforementioned gel electrolyte. In some embodiments, the electrolyte in the secondary battery is a gel electrolyte.

[0207] In this application, unless otherwise specified, the gel electrolyte is distributed both inside the electrode active material layer of the electrode sheet and outside the electrode sheet. The gel electrolyte at any location independently includes a cross-linked polymer, a gelling solvent, and an electrolyte salt.

[0208] The gel skeleton in the gel electrolyte can be formed by a polymerization reaction of polymerizable monomers. During the polymerization reaction, a corresponding initiator and / or cross-linking agent can be added.

[0209] The reaction of polymerizable monomers to form the gel skeleton is generally a polymerization reaction, and is also a cross-linking reaction. Monomers that participate in the formation of the gel skeleton through polymerization reactions can be collectively referred to as polymerizable monomers. Polymeric monomers include at least cross-linkable monomers, examples of which include, but are not limited to, polyene compounds. For example, polymerizable monomers may also include chain-extending monomers. Chain-extending monomers can provide linear segments between the cross-linking points of the gel skeleton. Examples of chain-extending monomers include monoene compounds.

[0210] In the present application, the cross-linkable monomer includes a functional group pair that can undergo a cross-linking reaction. Non-limiting examples of functional group pairs that can undergo a cross-linking reaction include multiple carbon-carbon double bonds, and further examples include monomers containing at least 2 carbon-carbon double bonds; such as a cross-linking monomer combination, and further examples include a cross-linking monomer combination including two monomers, one monomer including at least 2 reactive groups F1, and the other monomer including at least 3 reactive groups F2, and F1 and F2 can be coupled to form a covalent bond. Non-limiting examples of carbon-carbon double bonds include CH2=CH-CH2-, CH2=C(CH3)-CH2-, etc. The hydrogen atoms on the carbon-carbon double bonds can be replaced by suitable substituents, as long as they do not affect the cross-linking polymerization reaction. Non-limiting examples of cross-linking monomer combinations include a combination of a polyol or polyamine with a polyisocyanate, which can undergo a coupling reaction between -OH or an amino group (such as -NH2 or >NH) and -NCO to form a polyurethane or polyurea; and a combination of a polyacid and a polyamine, which can undergo a coupling reaction between -COOH and -NH2 or >NH to form a polymer containing an amide bond (-CO-NH- or -CO-N<), etc.

[0211] In the present application, "carbon-carbon double bond" refers to a polymerizable carbon-carbon double bond unless otherwise specified.

[0212] The types of polymerizable monomers may include, but are not limited to, one or more of carbonate monomers, sulfone monomers, isocyanate monomers, amide monomers, nitrile monomers, fluorinated monomers, ether compound monomers, ether segment-containing oligomers, and siloxanes.

[0213] When performing the crosslinking reaction of the crosslinkable monomer, the system may or may not contain an initiator, depending on the requirements of the crosslinking reaction. When an initiator is added, it may include, but is not limited to, one or more of azo initiators (such as azobisisobutyronitrile (AIBN)), peroxide initiators (also known as peroxy initiators), anionic and cationic initiators, organometallic compound initiators, amine catalyst initiators, and organophosphorus initiators. The type and amount of the initiator can be appropriately selected and controlled based on the type and amount of the polymerizable monomers (at least including the crosslinkable monomer).

[0214] In the present application, the compositions of the gel electrolytes at different locations (e.g., the first gel electrolyte and the second gel electrolyte) may be the same or different. The electrolyte salts in the gel electrolytes at different locations may be the same or different. The electrolyte salts in the first gel electrolyte and the second gel electrolyte may be the same or different. The gelling solvents in the gel electrolytes at different locations may be the same or different. The gelling solvents in the first gel electrolyte and the second gel electrolyte may be the same or different.

[0215] In some embodiments, the first gel electrolyte and the second gel electrolyte have the same composition, that is, they have the same type of cross-linked polymer, electrolyte salt and gelling solvent, the molar concentration of the electrolyte salt in the first gel electrolyte and the second gel electrolyte is the same, and the weight proportion of the cross-linked polymer in the first gel electrolyte and the second gel electrolyte is the same; the several "same" here can be understood as being obtained through the same gelation reaction system.

[0216] In some embodiments, the electrolyte salt in the gel electrolyte includes a lithium salt. In this case, the ions that the electrolyte salt can dissociate into include lithium ions, which is more conducive to conducting active lithium ions. In a non-limiting manner, the molar concentration of the electrolyte salt in the gel electrolyte can be 0.4 mol / L to 5 mol / L, but is not limited thereto.

[0217] In some embodiments, the electrolyte salt in the gel electrolyte is an electrolyte lithium salt.

[0218] In some embodiments, the secondary battery is a lithium ion secondary battery, and the electrolyte salt may include an electrolyte lithium salt. In some embodiments, the electrolyte salt in at least one of the first gel electrolyte and the second gel electrolyte includes a lithium salt.

[0219] In some embodiments, the electrolyte lithium salt may include one or more of lithium hexafluorophosphate (LiPF6), lithium tetrafluoroborate (LiBF4), lithium perchlorate (LiClO4), lithium hexafluoroarsenate (LiAsF6), lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide (LiTFSI), lithium trifluoromethanesulfonate (LiTFS), lithium difluorooxalatoborate (LiDFOB), lithium bisoxalatoborate (LiBOB), lithium difluorophosphate (LiPO2F2), lithium difluorobisoxalatophosphate (LiDFOP), and lithium tetrafluorooxalatophosphate (LiTFOP). In some embodiments, the electrolyte lithium salt may include one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bisfluorosulfonyl imide (LiFSI), lithium bistrifluoromethanesulfonyl imide, lithium difluorooxalatoborate, lithium perchlorate, lithium trifluoromethanesulfonyl, etc.

[0220] In some embodiments, the gelling solvent is a non-aqueous solvent, and further can be an organic solvent, and further can include but is not limited to one or more of a carboxylate solvent, a carbonate solvent, and a sulfone solvent. The carboxylate solvent can be a carboxylate or a halogenated carboxylate, and further can be C 2-4 C of alkyl carboxylic acid 1-3 Alkyl ester or its halide. Halide of carboxylic acid ester is also called halocarboxylic acid ester. 1-4 Examples of alkyl carboxylic acids include acetic acid, propionic acid, and butyric acid. 1-3 Examples of alkyl esters include methyl ester, ethyl ester, and propyl ester. Carbonate solvents can be carbonates or their halides. Carbonate halides are also called halogenated carbonates. The halogen substituents in halogenated carboxylates and halogenated carbonates can be fluorine, and the number of halogen substituents can range from 1 to perhalogenated. Taking fluorinated as an example, the number of fluorine atoms in fluorinated carboxylates and fluorinated carbonates can range from 1 to perfluorinated.

[0221] Without limitation, the gelling solvent may include but is not limited to ethylene carbonate (or ethylene carbonate, EC, ), propylene carbonate (or propylene carbonate, PC, ), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), dipropyl carbonate, diphenyl carbonate, dibutyl carbonate, methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), butylene carbonate (BC, ), dimethyl fluorocarbonate, fluoroethylene carbonate, bisfluoroethylene carbonate, diethyl fluorocarbonate, methyl ethyl fluorocarbonate, methyl formate (MF), methyl acetate (MA), ethyl acetate (EA), propyl acetate (PA), methyl propionate (MP), ethyl propionate (EP), propyl propionate (PP), butyl propionate, methyl butyrate (MB), ethyl butyrate (EB), propyl butyrate, 1,4-butyrolactone (GBL), sulfolane (SF), dimethyl sulfone (MSM), ethyl methyl sulfone (EMS) and diethyl sulfone (ESE) One or more.

[0222] In some embodiments, the gelling solvent may include one or more of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, dipropyl carbonate, diphenyl carbonate, dibutyl carbonate, butylene carbonate, fluorodimethyl carbonate, fluoroethylene carbonate, bisfluoroethylene carbonate, fluorodiethyl carbonate, fluoromethyl ethyl carbonate, propyl butyrate, propyl acetate, isopropyl acetate, ethyl propionate, propyl propionate, butyl propionate, isopropyl propionate, ethyl butyrate, methyl ether, propyl ether, butyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, 1,3-dioxolane, tetrahydrofuran, methyltetrahydrofuran, diphenyl ether, crown ether, dimethyl sulfoxide, diphenyl sulfoxide, thionyl chloride, sulfolane, dipropyl sulfone, and the like.

[0223] In some embodiments, the gel electrolyte may optionally include additives. For example, the additives may include negative electrode film-forming additives, positive electrode film-forming additives, and additives that can improve certain battery properties, such as additives that improve battery overcharge performance, and additives that improve battery high or low temperature performance.

[0224] The first gel electrolyte and the second gel electrolyte may independently include or exclude additives. When both include additives, the types of the additives in the two may be the same or different.

[0225] In some embodiments, the additives in the gel electrolyte may include, but are not limited to, vinylene carbonate (VC, ), vinyl ethylene carbonate (VEC, ), fluoroethylene carbonate (FEC), difluoroethylene carbonate (DFEC), trifluoromethylethylene carbonate (TFPC), methylene methanedisulfonate (MMDS), 1-propylene-1,3-sultone (PST), ethylene sulfite (ES), propylene sulfite (PS), diethylene sulfate (DTD), succinonitrile (SN), adiponitrile (AND), sulfonate cyclic quaternary ammonium salt, tris(trimethylsilyl) phosphate (TMSP), tris(trimethylsilyl) borate (TMSB) and anisole.

[0226] The following are some non-limiting descriptions of the positive electrode.

[0227] The positive electrode sheet in the secondary battery provided in the present application includes a positive electrode active material layer, and the positive electrode active material layer includes a positive electrode active substance.

[0228] In the present application, the positive electrode sheet includes a positive electrode current collector and a positive electrode active material layer disposed on at least one surface of the positive electrode current collector. Furthermore, the positive electrode active material layer includes a positive electrode active material.

[0229] Without limitation, the weight percentage of the positive electrode active material in the positive electrode active material layer may be greater than or equal to 80 wt %, further greater than or equal to 85 wt %, and further greater than or equal to 90 wt %.

[0230] As a non-limiting example, the positive electrode current collector has two surfaces facing away from each other in its thickness direction, and the positive electrode active material layer is disposed on either or both of the two facing surfaces of the positive electrode current collector.

[0231] In some embodiments, the positive electrode current collector may be a metal foil or a composite current collector. For example, aluminum foil may be used as the metal foil. In the positive electrode current collector, the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material base layer. The composite current collector may be obtained by forming a metal material on a polymer material substrate. In the positive electrode current collector, non-limiting examples of the metal material may include at least one of aluminum, aluminum alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In a non-limiting manner, in the positive electrode current collector, the polymer material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0232] In some embodiments, the positive electrode sheet includes a positive electrode active material layer, the positive electrode active material layer includes a positive electrode active material, and the positive electrode active material includes a lithium ion active material. When the active ions in the gel electrolyte battery include lithium ions, the electrolyte salt may include a lithium salt that is more compatible with the active ions, thereby facilitating better transport of the active lithium ions.

[0233] In the present application, “lithium ion active material” refers to a positive electrode active material that can provide active lithium ions.

[0234] In some embodiments of the present application, the positive electrode active material includes a lithium ion active material; further, the secondary battery is a lithium ion secondary battery.

[0235] In some embodiments of the present application, the secondary battery is a lithium-ion secondary battery. Lithium-ion secondary batteries utilize the intercalation and deintercalation of lithium ions in electrodes and their transport through electrolytes to achieve charge and discharge. Generally speaking, the active ions in lithium-ion secondary batteries are lithium ions, but this is not limited to this.

[0236] The positive electrode active material may be a positive electrode active material for batteries that is well known in the art. As a non-limiting example, the positive electrode active material or lithium ion active material may include one or more of the following materials or substances: lithium-containing phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. However, the present application is not limited to these materials or substances, and other traditional materials or substances that can be used as positive electrode active materials for batteries may also be used. These positive electrode active materials may be used alone or in combination of two or more. Among them, non-limiting examples of lithium transition metal oxides may include, but are not limited to, one or more of lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, lithium nickel cobalt oxide, lithium manganese cobalt oxide, lithium nickel manganese oxide, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, and their modified compounds. Non-limiting examples of lithium cobalt oxide include LiCoO2; non-limiting examples of lithium nickel oxide include LiNiO2; non-limiting examples of lithium manganese oxide include LiMnO2, LiMn2O4, etc.; non-limiting examples of lithium nickel cobalt manganese oxide include LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2 (also referred to as NCM 333 ), LiNi 0.5 Co 0.2 Mn 0.3 O2 (also referred to as NCM 523 ), LiNi 0.5 Co 0.25 Mn 0.25 O2 (also referred to as NCM 211 ), LiNi 0.6 Co 0.2 Mn 0.2 O2 (also referred to as NCM 622 ), LiNi 0.8 Co 0.1 Mn 0.1 O2 (also referred to as NCM 811 or NCM811) etc. Non-limiting examples of lithium nickel cobalt aluminum oxide include LiNi 0.80 Co 0.15 Al 0.05 O2. Non-limiting examples of olivine-structured lithium-containing phosphates may include, but are not limited to, one or more of lithium iron phosphate, a composite material of lithium iron phosphate and carbon, lithium manganese phosphate, a composite material of lithium manganese phosphate and carbon, lithium manganese iron phosphate, and a composite material of lithium manganese iron phosphate and carbon. Non-limiting examples of lithium iron phosphate include LiFePO4 (also referred to as LFP); non-limiting examples of lithium manganese phosphate include LiMnPO4.

[0237] Taking a battery cell and a secondary battery whose active ions include lithium ions as an example, it is understandable that lithium (Li) is deintercalated and consumed during the charge and discharge process of the battery, and the Li content in the positive electrode plate is different when the battery is discharged to different states. In the exemplary description of the positive electrode active material in this application, unless otherwise specified, the Li content can be the initial state of the material or the non-initial state after the charge and discharge cycle. The positive electrode active material is applied to the positive electrode plate in the battery system. After the charge and discharge cycle, the Li content in the positive electrode active material contained in the positive electrode plate usually changes. Among them, the Li content can be measured using atomic molar content, but is not limited to this. Regarding "Li content is the initial state of the material", the initial state of the material refers to the state before the material is added to the positive electrode slurry. It is understandable that new materials or new substances obtained by appropriate modification on the basis of the listed positive electrode active materials are also within the scope of positive electrode active materials. The aforementioned appropriate modification refers to an acceptable modification method for the positive electrode active material, and a non-limiting example is coating modification.

[0238] In the exemplary descriptions of the positive electrode active material in this application, the oxygen (O) content is only a theoretical value. Lattice oxygen release will cause the atomic molar content of oxygen to change, and the actual O content will fluctuate. The O content can be measured by atomic molar content, but is not limited to this.

[0239] In some embodiments, the positive electrode active material layer optionally includes a binder. As a non-limiting example, the binder may include one or more of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), vinylidene fluoride-tetrafluoroethylene-propylene terpolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene terpolymer, tetrafluoroethylene-hexafluoropropylene copolymer, and fluorine-containing acrylate resin. Typically, the weight percentage of the binder in the positive electrode active material layer may be 0 to 10 wt%, further 0 to 8 wt%, and further 1 wt% to 5 wt%, based on the total weight of the positive electrode active material layer.

[0240] In some embodiments, the positive electrode active material layer optionally includes a conductive agent. As non-limiting examples, the conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Typically, the weight percentage of the conductive agent in the positive electrode active material layer may be 0 to 10 wt %, further 0 to 8 wt %, and even further 0 to 5 wt %, based on the total weight of the positive electrode active material layer.

[0241] In some embodiments, the positive electrode sheet can be prepared by the following method: the components for preparing the positive electrode sheet, such as the positive electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent to form a positive electrode slurry; the positive electrode slurry is coated on at least one side of the positive electrode current collector, and after drying, compacting (compaction can be performed by cold pressing) and other processes, the positive electrode sheet can be obtained. The type of solvent can be selected from but not limited to any one of the aforementioned embodiments, such as N-methylpyrrolidone (NMP). The surface of the positive electrode current collector coated with the positive electrode slurry can be a single surface of the positive electrode current collector or two surfaces of the positive electrode current collector. The solid content of the positive electrode slurry can be 40wt% to 80wt%. The viscosity of the positive electrode slurry at room temperature can be 5000mPa·s to 25000mPa·s. When applying the positive electrode slurry, the unit surface density (single side) of the coating can be 130g / m on a dry weight basis. 2 ~400g / m 2 The compaction density of the positive electrode can be 3.0g / cm 3 ~3.6g / cm 3 , optional 3.3g / cm 3 ~3.5g / cm 3 .

[0242] The "compaction density" involved in this application has a meaning well known in the art and is one of the reference indicators of material energy density. In this application, unless otherwise specified, the compaction density of an electrode pole piece refers to the ratio of the mass of the electrode active material layer to its volume. The compaction density of a positive pole piece refers to the ratio of the mass of the positive active material layer to its volume, and the compaction density of a negative pole piece refers to the ratio of the mass of the negative active material layer to its volume. In this application, unless otherwise specified, for positive and negative pole pieces, the pole piece area before and after cold pressing does not change much, and the corresponding calculation formula for compaction density is:

[0243] Compacted density = coating area density / thickness of electrode active material layer.

[0244] Coating area density = slurry dry weight / electrode active material layer area.

[0245] The double-sided thickness of the electrode active material layer corresponds to the sum of the coating surface density on both sides, and the single-sided thickness corresponds to the single-sided coating surface density; when the electrode active material layers on both sides of the current collector are basically the same, it can be calculated according to the following formula: compaction density = single-sided coating surface density / single-sided thickness of the electrode active material layer.

[0246] The “single-sided” and “double-sided” electrode active material layers refer to the positional distribution relative to the current collector.

[0247] The following are some non-limiting descriptions of the negative electrode.

[0248] The negative electrode plate in the secondary battery provided in the present application includes a negative electrode active material layer, and the negative electrode active material layer includes a negative electrode active substance.

[0249] The negative electrode active material may include negative electrode active materials for batteries that are well known in the art. As non-limiting examples, the negative electrode active material may include one or more of the following materials: artificial graphite, natural graphite, soft carbon, hard carbon, silicon-based materials, tin-based materials, lithium titanate, etc. Silicon-based materials may include one or more of elemental silicon, silicon oxides, silicon-carbon composites, silicon-nitrogen composites, and silicon alloys. Tin-based materials may include one or more of elemental tin, tin oxides, and tin alloys. However, the present application is not limited to these materials, and other traditional materials that can be used as negative electrode active materials for batteries may also be used. These negative electrode active materials may be used alone, or two or more may be used in combination.

[0250] Without limitation, the weight percentage of the negative electrode active material in the negative electrode active material layer may be greater than or equal to 80 wt %, and further may be greater than or equal to 90 wt %.

[0251] In some embodiments, the negative electrode active material includes one or more of a carbon-based material, a silicon-based material, a tin-based material, and lithium titanate, as well as modified forms of any of the foregoing materials, wherein the modified form includes one or more of a doping modification and a coating modification. Both the doping modification method and the coating modification method can adopt or refer to existing modification methods in the art, including but not limited to the selection of element types and doping amounts. Carbon-based materials may include but are not limited to one or more of graphite materials, soft carbon, hard carbon, etc. Graphite materials may include one or more of artificial graphite and natural graphite.

[0252] In some embodiments, the negative electrode active material includes a carbon-based material and a silicon-based material. Without limitation, the combined mass of the carbon-based material and the silicon-based material may account for ≥80% of the total mass of the negative electrode active material, optionally ≥90%, further optionally ≥95%, further optionally ≥96%, and further optionally 100%. The combined mass of the graphite material and the silicon-based material may also account for any of the following percentages, or a percentage greater than or equal to any of the following percentages and less than or equal to 100%, or a range consisting of any two of the following percentages: 80%, 82%, 83%, 84%, 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 98%, and the like. The definition of carbon-based material can be found above. For example, the carbon-based material can be a graphite material. The content of the carbon-based material can also be found in any suitable embodiment described above. Without limitation, the weight proportion of the silicon-based material in the negative electrode active material can be 0-40wt%, further optionally 0-25wt%, and further optionally 3wt%-25wt%. Without limitation, the weight proportion of the silicon element in the negative electrode active material can be 0-40wt%, further optionally 0-25wt%, and further optionally 3wt%-25wt%. Without limitation, the weight proportion of the silicon-based material or the silicon element in the negative electrode active material can be any of the following percentages or a range consisting of any two of the following percentages: 0wt%, 1wt%, 2wt%, 3wt%, 5wt%, 6wt%, 8wt%, 10wt%, 12wt%, 14wt%, 15wt%, 16wt%, 18wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, etc.

[0253] In some embodiments, the negative electrode active material includes a carbon-based material. Without limitation, the mass percentage of the carbon-based material in the negative electrode active material can be ≥80%, optionally ≥90%, further optionally ≥95%, further optionally ≥96%, etc., further optionally 100%, etc. The mass percentage of the carbon-based material in the negative electrode active material can also be any of the following percentages, or greater than or equal to any of the following percentages and less than or equal to 100%, or selected from the interval consisting of any two of the following percentages: 80%, 82%, 83%, 84%, 85%, 86%, 88%, 90%, 92%, 94%, 95%, 96%, 98%, etc. The definition of carbon-based materials can be found above. For example, the carbon-based material can be a graphite material.

[0254] In some embodiments, the negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer disposed on at least one surface of the negative electrode current collector, wherein the negative electrode active material layer includes a negative electrode active material. The negative electrode active material may be as defined above.

[0255] As a non-limiting example, the negative electrode current collector has two surfaces facing each other in its thickness direction, and the negative electrode active material layer is disposed on either or both of the two facing surfaces of the negative electrode current collector.

[0256] In some embodiments, the negative electrode current collector may be a metal foil or a composite current collector. For example, copper foil may be used as the metal foil. In the negative electrode current collector, the composite current collector may include a polymer material base layer and a metal layer formed on at least one surface of the polymer material substrate; the composite current collector may be obtained by forming a metal material on a polymer material substrate. In the negative electrode current collector, non-limiting examples of the metal material may include one or more of copper, copper alloy, nickel, nickel alloy, titanium, titanium alloy, silver and silver alloy. In the negative electrode current collector, non-limiting examples of the polymer material substrate may include one or more of polypropylene (PP), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polystyrene (PS), polyethylene (PE), etc.

[0257] In some embodiments, the negative electrode active material layer may optionally include a binder. As non-limiting examples, the binder may include one or more of styrene-butadiene rubber (SBR), polyacrylic acids (PAAs), sodium polyacrylate (PAAS), polyacrylamide (PAM), polyvinyl alcohol (PVA), sodium alginate (SA), polymethacrylic acid (PMAA), and carboxymethyl chitosan (CMCS). Without limitation, the weight proportion of the binder in the negative electrode active material layer may be 0-10 wt %, further 0-5 wt %, further 1 wt %-5 wt %, and further optionally 1 wt %-3 wt %.

[0258] In some embodiments, the negative electrode active material layer optionally includes a conductive agent. The conductive agent may include one or more of superconducting carbon, acetylene black, carbon black, Ketjen black, carbon dots, carbon nanotubes, graphene, and carbon nanofibers. Without limitation, the weight percentage of the conductive agent in the negative electrode active material layer may be 0 to 15 wt %, further preferably 0 to 10 wt %, and even more preferably 0 to 5 wt %.

[0259] In some embodiments, the negative electrode active material layer may further include other additives, such as thickeners. Non-limiting examples of thickeners include sodium carboxymethyl cellulose (CMC-Na). The weight percentage of the other additives in the negative electrode active material layer may be 0-15 wt %, further 0-10 wt %, further 0-5 wt %, further 0-3 wt %, and further 0-2 wt %.

[0260] In some embodiments, the negative electrode sheet can be prepared by the following method: the components for preparing the negative electrode sheet, such as the negative electrode active material, the conductive agent, the binder and any other components, are dispersed in a solvent (a non-limiting example of the solvent is deionized water) to form a negative electrode slurry; the negative electrode slurry is coated on at least one side of the negative electrode current collector, and after drying, compacting (compaction can be performed by cold pressing), etc., the negative electrode sheet can be obtained. The surface of the negative electrode current collector coated with the negative electrode slurry can be a single surface of the negative electrode current collector or two surfaces of the negative electrode current collector. The solid content of the negative electrode slurry can be 30wt% to 70wt%, and can be optionally 40wt% to 60wt%. The viscosity of the negative electrode slurry at room temperature can be 2000mPa·s to 10000mPa·s, and can be optionally 3000mPa·s to 10000mPa·s. When coating the negative electrode slurry, the unit area density (single side) of the coating can be 35g / m2 on a dry weight basis. 2 ~150g / m 2 The compaction density of the negative electrode can be 1.0g / cm 3 ~2.0g / cm 3 , optional 1.0g / cm 3 ~1.8g / cm 3 .

[0261] The following are some non-limiting descriptions of the release membrane.

[0262] In some embodiments, the secondary battery further includes a separator. The present application has no particular limitation on the type of separator, and any known porous separator with good chemical and mechanical stability can be selected.

[0263] In some embodiments, the material of the separator may include one or more of glass fiber, non-woven fabric, polyethylene, polypropylene, and polyvinylidene fluoride. The separator may be a single-layer film or a multi-layer composite film, without particular limitation. When the separator is a multi-layer composite film, the materials of each layer may be the same or different, without particular limitation.

[0264] In some embodiments, the thickness of the isolation film is 6 μm to 40 μm, and optionally 12 μm to 20 μm.

[0265] The following are some non-limiting descriptions of electrode assemblies, electrochemical energy storage devices, and secondary batteries.

[0266] In some embodiments, the positive electrode sheet, the negative electrode sheet, and the separator can be formed into an electrode assembly through a winding process or a lamination process.

[0267] In some embodiments, the electrochemical energy storage device may include an outer packaging that can be used to encapsulate the electrode assembly and the gel electrolyte precursor solution.

[0268] In some embodiments, the secondary battery may include an outer package that can be used to encapsulate the electrode assembly and the gel electrolyte precursor.

[0269] In some embodiments, the secondary battery is a lithium-ion secondary battery.

[0270] In some embodiments, the secondary battery is a lithium ion secondary battery, the positive electrode active material includes a lithium ion active material, and further, the electrolyte salt may include an electrolyte lithium salt.

[0271] In some embodiments, the outer packaging of the secondary battery can be a hard shell, such as a hard plastic shell, an aluminum shell, a steel shell, etc. The outer packaging of the secondary battery can also be a soft shell, such as a pouch-type soft shell. The material of the soft shell can be plastic. Further, non-limiting examples of plastic can include one or more of polypropylene, polybutylene terephthalate, and polybutylene succinate.

[0272] A secondary battery includes at least one battery cell. A secondary battery may include one or more battery cells.

[0273] The present application has no particular limitation on the shape of the battery cell, which can be cylindrical, square, or any other shape. For example, FIG1 shows a battery cell 5 with a square structure as an example.

[0274] In some embodiments, referring to Figure 2, the outer packaging may include a shell 51 and a cover plate 53. The shell 51 may include a bottom plate and side plates connected to the bottom plate, and the bottom plate and the side plates enclose a receiving cavity. The shell 51 has an opening connected to the receiving cavity, and the cover plate 53 can be covered on the opening to close the receiving cavity. The positive electrode sheet, the negative electrode sheet and the isolation membrane can be formed into an electrode assembly 52 through a winding process or a lamination process. The electrode assembly 52 is encapsulated in the receiving cavity. The gel electrolyte precursor is impregnated in the electrode assembly 52. ​​The number of electrode assemblies 52 contained in the battery cell 5 can be one or more, and those skilled in the art can select according to actual needs.

[0275] The secondary battery may be a battery module 4 or a battery pack 1 .

[0276] A battery module includes at least one battery cell. The number of battery cells contained in a battery module can be one or more, and those skilled in the art can select an appropriate number based on the application and capacity of the battery module.

[0277] FIG3 shows an example battery module 4. Referring to FIG3 , within the battery module 4, multiple battery cells 5 may be arranged sequentially along the length of the battery module 4. Of course, they may also be arranged in any other manner. Furthermore, the multiple battery cells 5 may be secured together using fasteners.

[0278] Optionally, the battery module 4 may further include a housing having an accommodation space, and the plurality of battery cells 5 are accommodated in the accommodation space.

[0279] In some embodiments, the battery modules may be assembled into a battery pack. The battery pack may contain one or more battery modules. Those skilled in the art may select an appropriate number based on the application and capacity of the battery pack.

[0280] Figures 4 and 5 illustrate an example battery pack 1. Referring to Figures 4 and 5 , the battery pack 1 may include a battery box and multiple battery modules 4 disposed within the battery box. The battery box comprises an upper case 2 and a lower case 3. The upper case 2 can be placed over the lower case 3 to form an enclosed space for accommodating the battery modules 4. The multiple battery modules 4 can be arranged in any manner within the battery box.

[0281] In a second aspect of the present application, a gel electrolyte precursor solution is provided, which includes the following components: a free radical polymerization system, an inhibitor, an electrolyte salt, and an electrolyte solvent;

[0282] The free radical polymerization system includes polymerizable monomers and an initiator. The initiator can initiate a free radical polymerization reaction of the polymerizable monomers to form a cross-linked polymer. The inhibitor includes an inhibitory group that can terminate the free radical polymerization reaction of the free radical polymerization system.

[0283] In this application, unless otherwise specified, "gel electrolyte precursor" refers to a liquid system that can form a gel electrolyte through a curing reaction. Unless otherwise specified, the curing reaction is a reaction in which polymerized monomers form cross-linked polymers through free radical polymerization. After the curing reaction, the gel electrolyte precursor transforms from a liquid state to a gel state to form a gel electrolyte. Therefore, the curing reaction is also called a cross-linking reaction or a gelation reaction, and the gel electrolyte precursor can be used as a gelation reaction system. Accordingly, the electrolyte lithium salt in the gel electrolyte precursor is converted into the electrolyte lithium salt in the gel electrolyte included in the secondary battery.

[0284] In this application, unless otherwise specified, a "free radical polymerization system" refers to the raw material system used to form the crosslinked polymer portion of a gel electrolyte, typically comprising at least monomers and an initiator. The definition of "monomers" can be found above. Unless otherwise specified, the "initiator" in a free radical polymerization system is capable of initiating a free radical polymerization reaction of the monomers, thereby converting the monomers into crosslinked polymers. After the gel electrolyte precursor solution undergoes a curing reaction, the crosslinked polymers form the gel backbone of the gel electrolyte.

[0285] The definitions of "polymerization inhibitor" and "polymerization inhibitor group" can be found above.

[0286] The definition of “electrolyte salt” may be found in the context of this application, including the first aspect of this application.

[0287] In some embodiments, the inhibitor inhibits the free radical polymerization system for a time greater than or equal to 1200 minutes (20 hours) at 45° C., optionally, for a time greater than or equal to 2 days (48 hours). Unless otherwise specified, the test pressure is 5 kPa.

[0288] In this application, unless otherwise specified, "test pressure" refers to the pressure of the environment in which the free radical polymerization system is located during the test. The test pressure is used to simulate the negative pressure formed by vacuuming after injecting the gel electrolyte precursor into the dry battery cell and before packaging.

[0289] Those skilled in the art can place the "gel electrolyte precursor solution" at a certain temperature (such as the immersion temperature or the formation temperature) for a certain period of time, and judge whether the "inhibitor has an inhibitory effect during the test period" based on the change in the viscosity of the system.

[0290] Judgment method: When the system viscosity growth ratio (Rη) is less than or equal to 20%, it can be considered that the inhibitor is still effectively inhibiting the free radical polymerization system. It is understood that when the system shows a significant viscosity change or a clear non-flowing gel phase, the inhibitor's inhibitory effect can be considered to have failed.

[0291] In this application, unless otherwise specified, the viscosity of the liquid phase system (which may be a gel electrolyte precursor) can be tested by conventional methods in the art, and can be measured using instruments and methods known in the art. For example, reference can be made to the national standard GB / T10247-2008 "Viscosity Measurement Method", and the test can be performed based on the rotational viscometer in Appendix D of the national standard GB / T10247-2008.

[0292] Unless otherwise specified, the viscosity of a liquid phase system (which can be a gel electrolyte precursor) can be tested using the following method: a certain mass of the sample to be tested is placed in a sample container and tested using a rotational viscometer, model DV2TLV, manufactured by Brookfield. At 25°C, the shear force exerted on the rotor as it rotates continuously at a constant speed in the sample causes the spring to generate torque, which is proportional to the viscosity, giving the viscosity value. The test equipment meets the following test environmental conditions: 1. External environment of the equipment: Temperature: 25°C, Humidity: RH <80%; 2. Internal environment of the equipment: 2 / 3 of the sample container is immersed in a water bath, the medium is water, and the water is used to maintain a constant temperature for the sample.

[0293] Obtaining the test sample: The initial viscosity η0 of the prepared gel electrolyte precursor to be tested is tested; the gel electrolyte precursor to be tested is packaged at a negative pressure of 5kPa, then kept at 45°C for 1200 minutes, cooled to 25°C and the viscosity η1 is tested. The "increase ratio of the system viscosity" Rη = (η1-η0) / η0×100%.

[0294] Analysis method: When Rη≤20%, it is considered that the inhibitor has an inhibitory effect during the test period (5kPa, 45℃ insulation for 1200min), which means that the requirement of "at 45℃, the inhibition time of the inhibitor in inhibiting the free radical polymerization system is greater than or equal to 1200min (20h)" is met.

[0295] In some embodiments, the initiator can initiate the free radical polymerization system to perform a free radical polymerization reaction within 600 min at 70° C. Unless otherwise specified, the test pressure is 5 kPa.

[0296] Judgment method: When the presence of cross-linked polymers can be detected, it is considered that a free radical polymerization reaction has occurred in the free radical polymerization system.

[0297] In this application, unless otherwise specified, the 1 At least one of the following methods is used to analyze whether a cross-linked polymer is formed: H NMR) method, gel permeation chromatography (GPC) method, and high performance liquid chromatography (HPLC) method. 1 When characteristic peaks of cross-linked polymers appear in H NMR (e.g., the characteristic peak of methylene hydrogen in -CH2-C(CH3)(COOCH3)- appears in the methyl methacrylate system), or characteristic peaks of polymers other than monomers appear in gel permeation chromatography (GPC) or high performance liquid chromatography (HPLC), it can be considered that "cross-linked polymers have been formed," and further, it can be considered that "free radical polymerization has occurred in the free radical polymerization system."

[0298] Please refer to the methods in the Examples section below and will not be described in detail here.

[0299] In this application, unless otherwise specified, the "electrolyte solvent" in the gel electrolyte precursor solution can serve as a solvent for the electrolyte salt and a solvent for the polymerized monomers in the free radical polymerization system. After the curing reaction of the gel electrolyte precursor solution, at least a portion of the electrolyte solvent constitutes the gelling solvent of the gel electrolyte (a small amount of volatility may exist, or no volatility is permitted), which is used to bind the electrolyte salt.

[0300] Without limitation, the molar concentration of the electrolyte salt in the gel electrolyte may be 0.5 mol / L to 5 mol / L, but is not limited thereto. The type of the electrolyte salt may be referred to the context of this application.

[0301] The aforementioned secondary battery including the gel electrolyte can be formed by using the gel electrolyte precursor solution provided in the second aspect of the present application, through impregnation of the electrode, formation and curing.

[0302] The distribution uniformity of the gel electrolyte in the lateral direction can be analyzed by comparing the filling factor differences of the gel electrolyte at different lateral positions of the electrode plate, and the distribution uniformity of the gel electrolyte in the thickness direction of the electrode plate can be analyzed by comparing the filling factor differences of the gel electrolyte at different thickness positions of the electrode plate.

[0303] Regarding the uniformity of the distribution of the gel electrolyte in the lateral direction, the aforementioned method can be used: select several local regions with a certain lateral area at different lateral positions of the electrode active material layer, slice the local regions at the selected lateral positions continuously along the thickness direction of the electrode active material layer, and calculate the filling factor of the local region based on the three-dimensional reconstruction results. Then compare the filling factors α of different local areas i The degree of dispersion can be analyzed by using the coefficient of variation to analyze the fill factor α of different local areas. i The coefficient of variation is equal to the ratio of the standard deviation to the mean. The coefficient of variation obtained by counting multiple local areas at different horizontal positions can be recorded as CV i The number of selected local regions can be 3 or more. Coefficient of variation CV i The smaller it is, the lower the degree of dispersion is, indicating that the gel electrolyte is more evenly distributed in different lateral directions.

[0304] Similarly, regarding the uniformity of the distribution of the gel electrolyte in the thickness direction of the electrode sheet, the aforementioned method can be referred to: select a local area with a certain transverse area in the electrode active material layer, slice the selected local area continuously along the thickness direction of the electrode active material layer to obtain different thickness layers, and calculate the filling factor of the different thickness layers of the local area based on the three-dimensional reconstruction results. Among them, V j1 is the volume of gel electrolyte in a single thickness layer, V i is the volume of a single thickness layer, is the porosity of a single thickness layer; then compare the filling factors α of layers with different thicknesses j The coefficient of variation (CV j ), characterizes the discrete degree of filling factor of different thickness layers. The number of thickness layers can be 3 or more. Coefficient of variation CV j The smaller it is, the lower the degree of dispersion is, which means that the gel electrolyte is more evenly distributed at different thickness positions.

[0305] For the embodiment of the secondary battery prepared by using the gel electrolyte precursor solution provided in the second aspect of the present application, a corresponding comparative example is obtained by omitting only the polymerization inhibitor in the gel electrolyte precursor solution based on the embodiment.

[0306] By comparing the CV of the examples with the comparative examples i , according to the "CV of the embodiment i Less than the CV of the control example i "It can be confirmed that by setting the polymerization inhibitor in the gel electrolyte precursor, the distribution uniformity of the gel electrolyte in the secondary battery at different lateral positions of the electrode plate is improved. The coefficient of variation CV of the positive electrode plate i Can be recorded as CV Pi , coefficient of variation CV of the negative electrode i Can be recorded as CV Ni .

[0307] By comparing the CV of the examples with the comparative examples j , according to the "CV of the embodiment j Less than the CV of the control example j "It can be confirmed that by setting the polymerization inhibitor in the gel electrolyte precursor, the distribution uniformity of the gel electrolyte at different thickness positions of the electrode sheet in the secondary battery is improved. The coefficient of variation CV of the positive electrode sheet j Can be recorded as CV Pj , coefficient of variation CV of the negative electrode j Can be recorded as CV Nj .

[0308] It is understood that the positive electrode sheet of the embodiment is compared with the positive electrode sheet of the comparative example, and the negative electrode sheet of the embodiment is compared with the negative electrode sheet of the embodiment. It is also understood that the positive electrode sheet or negative electrode sheet at similar positions of the electrode assembly of the embodiment and the comparative example can be selected for analysis, for example, the innermost, outermost and middle positions of the electrode assembly can be selected for analysis respectively.

[0309] In addition, the gel electrolyte precursor provided in the second aspect of the present application is recorded as the "example precursor", and the precursor corresponding to the example precursor with the inhibitor omitted is recorded as the "control precursor". The example precursor and the control precursor are respectively absorbed by different capillaries, and the capillaries are set on the surface of the electrode plate. The descending speed of the example precursor and the control precursor is compared to reflect the wettability of the precursor to the electrode plate. The faster the descending speed, the better the wettability of the precursor to the electrode plate. For example, the positive electrode plate and the negative electrode plate in Example 1 below can be used to compare the difference in wettability to the positive electrode plate and the difference in wettability to the negative electrode plate.

[0310] The gel electrolyte precursor provided in the second aspect of the present application has improved wettability to both the positive electrode sheet and the negative electrode sheet compared to the precursor without adding a polymerization inhibitor.

[0311] In some embodiments, the mass percentage of the polymerized monomer in the gel electrolyte precursor solution can be, but is not limited to, 2% to 15%, optionally 8% to 12%, or any of the following percentages or an interval consisting of any two of the following percentages: 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc.

[0312] In some embodiments, the mass fraction of the polymerization inhibitor in the gel electrolyte precursor solution can be, but is not limited to, 50 ppm to 2000 ppm, and can be optionally 500 ppm to 1000 ppm. It can also be any of the following mass fractions or an interval consisting of any two of the following mass fractions: 50 ppm, 150 ppm, 200 ppm, 250 ppm, 300 ppm, 400 ppm, 500 ppm, 600 ppm, 800 ppm, 1000 ppm, 1200 ppm, 1400 ppm, 1500 ppm, 1600 ppm, 1800 ppm, 2000 ppm, etc.

[0313] In some embodiments, the gel electrolyte precursor solution satisfies one or more of the following characteristics (any numerical parameter in the following characteristics can also be selected from any appropriate value or range in the context):

[0314] The mass percentage of the polymerized monomer in the gel electrolyte precursor solution is 2% to 15%, and can be optionally 8% to 12%;

[0315] The mass fraction of the polymerization inhibitor in the gel electrolyte precursor solution is 50 ppm to 2000 ppm, and can be optionally 500 ppm to 1000 ppm.

[0316] By adjusting the mass percentage of the polymerized monomer in the gel electrolyte precursor solution within the aforementioned range, it is advantageous to provide a relatively stable gel structure while taking into account the transport capability of active ions.

[0317] Adjusting the mass fraction of the inhibitor in the gel electrolyte precursor solution is beneficial to providing sufficient inhibition effect while minimizing the addition amount.

[0318] In some embodiments, the polymerization inhibitor comprises a phenolic polymerization inhibitor. As defined above, a phenolic polymerization inhibitor comprises an aromatic ring and a phenolic hydroxyl group directly bonded to the aromatic ring. Within a molecule of the phenolic polymerization inhibitor, the polymerization inhibitory group may comprise one or more phenolic hydroxyl groups. See also the definition above.

[0319] In some embodiments, in one molecule, the phenolic polymerization inhibitor contains 1 to 5 phenolic hydroxyl groups, for example, 1, 2, 3, 4 or 5, further 1, 2 or 3, and further 1 or 2.

[0320] In some embodiments, in one molecule, the mass proportion of phenolic hydroxyl groups in the phenolic polymerization inhibitor can be but not limited to 7.5% to 40.5%, optionally 8% to 35%, and can also be any of the following percentages or an interval consisting of any two of the following percentages: 7.5%, 8%, 10%, 12%, 14%, 15%, 16%, 18%, 20%, 22%, 24%, 25%, 28%, 30%, 32%, 34%, 35%, 36%, 38%, 40%, 40.5%, etc.

[0321] By controlling one or both of the parameters, such as the number of phenolic hydroxyl groups contained in the phenolic polymerization inhibitor and the mass proportion of the phenolic hydroxyl groups in the phenolic polymerization inhibitor, within the aforementioned range, the inhibition time and the inhibition efficiency can be adjusted, and a more sufficient inhibition effect can be achieved with a more appropriate dosage of the phenolic polymerization inhibitor.

[0322] In some embodiments, in one molecule, the number of aromatic rings contained in the phenolic polymerization inhibitor is 1 or more, optionally 1 or 2. When the number of aromatic rings is multiple, adjacent aromatic rings are connected by chemical bonds or -C(R1R2)-, wherein R1 and R2 are each independently H or C 1-4 Alkyl, each independently H or C 1-3 Alkyl, further each independently selected from H, methyl, ethyl or propyl, further each independently selected from H, methyl or ethyl, further each independently selected from H or methyl. In some embodiments, R1 and R2 are each independently selected from H, methyl, ethyl, propyl or butyl, further each independently selected from H, methyl, ethyl, n-propyl or n-butyl, further each independently selected from H, methyl, ethyl or n-propyl. In some embodiments, R1 and R2 are the same. In some embodiments, R1 and R2 are both H, methyl, ethyl or n-propyl, further each independently selected from H, methyl or ethyl, further each independently selected from methyl. In some embodiments, -C(R1R2)- is -CH(CH3)-, -CH(CH2CH3)- or -CH(CH2CH2CH3)-. In some embodiments, -C(R1R2)- is -CH(CH2CH2CH3)-. In some embodiments, -C(R1R2)- is -C(CH3)2- or -CH(CH2CH2CH3)-.

[0323] In some embodiments, -C(R1R2)- has 1 to 4 carbon atoms.

[0324] In some embodiments, the phenolic polymerization inhibitor contains 1 or 2 aromatic rings; when the number of aromatic rings is multiple, adjacent aromatic rings are connected by chemical bonds or -C(R1R2)-, wherein R1 and R2 are each independently H or C 1-3 The alkyl group -C(R1R2)- has 1 to 4 carbon atoms.

[0325] The number of sites for introducing phenolic hydroxyl groups can be adjusted by controlling the number of aromatic rings.

[0326] In some embodiments, the molecular weight of the phenolic polymerization inhibitor is less than or equal to 1000Da, optionally, less than or equal to 500Da, and can also be any of the following molecular weights or an interval consisting of any two of the following molecular weights: 94Da, 100Da, 150Da, 160Da, 180Da, 200Da, 250Da, 300Da, 400Da, 500Da, 600Da, 700Da, 750Da, 800Da, 900Da, 1000Da, etc.

[0327] By controlling the molecular weight of the phenolic polymerization inhibitor within the aforementioned range, the steric hindrance effect can be reduced, thereby making it more conducive for the polymerization inhibitory group to exert its inhibitory effect.

[0328] In some embodiments, the phenolic polymerization inhibitor satisfies one or more of the following characteristics (any numerical parameter in the following characteristics can also be selected from any appropriate numerical value or range in the context):

[0329] In one molecule, the number of phenolic hydroxyl groups contained in the phenolic polymerization inhibitor is 1 to 5, which can be 1, 2 or 3;

[0330] In one molecule, the mass proportion of the phenolic hydroxyl group in the phenolic polymerization inhibitor is 7.5% to 40.5%, and can be optionally 8% to 35%;

[0331] In one molecule, the phenolic polymerization inhibitor contains one or more aromatic rings, which can be 1 or 2. When the number of aromatic rings is multiple, adjacent aromatic rings are connected by chemical bonds or -C(R1R2)-, wherein R1 and R2 are each independently H or C 1-4 Alkyl, each independently H or C 1-3 Alkyl, further each independently, -C(R1R2)- has 1 to 4 carbon atoms;

[0332] The molecular weight of the phenolic polymerization inhibitor is less than or equal to 1000 Da, optionally, less than or equal to 500 Da.

[0333] In some embodiments, any aromatic ring in the phenolic polymerization inhibitor is independently connected with 0, 1 or more (optionally 2 to 5, further optionally 2, 3, 4 or 5, further optionally 2 or 3, further optionally 2) non-hydroxyl substituents selected from the following group: halogen, nitro, C 1-4 Alkyl (optionally methyl, ethyl, propyl or butyl, further optionally methyl or tert-butyl) and C 1-3 Alkoxy (optionally methoxy, ethoxy or propoxy, further optionally methoxy). Wherein, halogen can be selected from one or more of fluorine, chlorine and bromine. In some embodiments, halogen is bromine.

[0334] In some embodiments, any aromatic ring in the phenolic polymerization inhibitor is independently connected with 0, 1 or more (optionally 2 to 5, further optionally 2, 3, 4 or 5, further optionally 2 or 3, further optionally 2) non-hydroxy substituents selected from the following group: halogen and nitro; the halogen is selected from one or more of fluorine, chlorine and bromine, and can be bromine.

[0335] In some embodiments, the number of substituents attached to any aromatic ring in the phenolic polymerization inhibitor is 0 to 5, and can be 0, 1, 2, 3, 4 or 5.

[0336] In the present application, unless otherwise specified, “the number of non-hydroxyl substituents attached to any aromatic ring in the phenolic polymerization inhibitor” refers to the number of non-hydroxyl substituents excluding “phenolic hydroxyl groups”.

[0337] Without limitation, the phenolic polymerization inhibitor may include, but is not limited to, one or more of the following compounds: phenol, 2,6-di-tert-butylphenol, p-methoxyphenol, 2,6-di-tert-butyl-4-methylphenol, hydroquinone, catechol, 2-nitrohydroquinone, monomethyl hydroquinone, trimethyl hydroquinone, p-tert-butylcatechol, 2,5-di-tert-butylhydroquinone, bisphenol A, 4,4'-dihydroxybiphenyl, 4,4'-butylenebis(6-tert-butyl-3-methylphenol), pyrogallol and 4-bromophenol.

[0338] The polymerization inhibitor can be selected from commercially available polymerization inhibitors (such as phenolic polymerization inhibitors), or can be synthesized using conventional methods of organic chemical synthesis according to the structural design in this application. Those skilled in the art can identify the structure of the polymerization inhibitor and its polymerization inhibition residue by one or more of the following detection methods, including but not limited to: Fourier transform infrared (FT-IR) spectroscopy, ultraviolet spectroscopy, hydrogen nuclear magnetic resonance (H-NMR) spectroscopy, and the like. 1H NMR) method, X-ray diffraction (XRD) method, gel permeation chromatography (GPC) method, high performance liquid chromatography (HPLC) method, mass spectrometry, single crystal X-ray diffraction (SCXRD) method, inductively coupled plasma spectroscopy (ICP) method, etc. The sample preparation methods and testing methods of these testing methods are known to those skilled in the art, and the testing parameters can be appropriately adjusted according to the specific structure of the compound and the characteristics of the sample.

[0339] In some embodiments, the mass ratio of the initiator to the polymerization monomer can be but is not limited to 0.5% to 10%, optionally 0.5% to 5%, and can also be any of the following percentages or an interval consisting of any two of the following percentages: 0.5%, 0.6%, 0.8%, 1%, 1.5%, 1.6%, 1.8%, 2%, 2.5%, 3%, 3.5%, 4%, 5%, 6%, 7%, 7.5%, 8%, 9%, 10%, etc.

[0340] In some embodiments, the mass ratio of the polymerization inhibitor to the initiator can be, but is not limited to, 0.1% to 50%, optionally 0.1% to 20%, or any of the following percentages or an interval consisting of any two of the following percentages: 0.1%, 0.2%, 0.25%, 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.5%, 1.6%, 1.8%, 2%, 2.5%, 3%, 3.5%, 4%, 5%, 6%, 7%, 7.5%, 8%, 9%, 10%, 12%, 15%, 16%, 18%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, etc. The mass ratio of the polymerization inhibitor to the initiator may also be selected from the following ranges: 0.1% to 30%, 0.25% to 30%, 0.25% to 20%, 0.5% to 20%, and the like.

[0341] In some embodiments, the mass ratio of the inhibitory group in the inhibitor to the initiator can be, but is not limited to, 0.01% to 15%, optionally 0.05% to 5%, or any of the following percentages or an interval consisting of any two of the following percentages: 0.01%, 0.02%, 0.04%, 0.05%, 0.06%, 0.08%, 0.1%, 0.12%, 0.15%, 0.16%, 0.18%, 0.2%, 0.25%, 0.3%, 0.4%, 0.5%, 0.6%, 0.8%, 1%, 1.5%, 1.6%, 1.8%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 6%, 7%, 7.5%, 8%, 9%, 10%, 12%, 15%, etc. The mass ratio of the polymerization inhibitor group in the polymerization inhibitor to the initiator can also be selected from the following ranges: 0.01% to 8%, 0.05% to 8%, etc.

[0342] In some embodiments, the gel electrolyte precursor satisfies one or more of the following characteristics (any numerical parameter in the following characteristics may also be selected from any appropriate numerical value or range in the context):

[0343] The mass ratio of the initiator to the polymerization monomer is 0.5% to 10%, and can be optionally 0.5% to 5%;

[0344] The mass ratio of the polymerization inhibitor to the initiator is 0.1% to 50%, and can be optionally 0.1% to 20%;

[0345] The mass ratio of the polymerization inhibitor group in the polymerization inhibitor to the initiator is 0.01% to 15%, and can be optionally 0.05% to 5%.

[0346] By controlling the mass ratio of the initiator to the polymerization monomer within the aforementioned range, the polymerization monomer is facilitated to fully react and more fully participate in the gelation structure.

[0347] By controlling one or both of the mass ratio of the polymerization inhibitor to the initiator and the mass ratio of the polymerization inhibitor group in the polymerization inhibitor to the initiator within the aforementioned range, the polymerization inhibitor effect can be fully exerted before the start of the curing reaction (including in the wetting and formation stages), and it is also beneficial to control the amount of by-products introduced, and the initiation effect of the initiator can be fully exerted. The polymerization inhibitor can be consumed as quickly as possible during the curing reaction stage, thereby starting the curing reaction as quickly as possible, and it is also beneficial to reduce or avoid residual polymerization monomers, thereby reducing the adverse effects of the reaction between the residual monomers and the electrode on the electrochemical properties of the battery.

[0348] In some embodiments, the polymerizable monomer includes a polyene compound and may or may not include a monoene compound, wherein the polyene compound has multiple polymerizable carbon-carbon double bonds and the monoene compound has one polymerizable carbon-carbon double bond.

[0349] In some embodiments, the polyene compound comprises a structure of [CH2=C(R 01 )-] k U1, k is an integer greater than or equal to 2, U1 is a k-valent non-aromatic group or a k-valent aromatic group; R 01 Each occurrence is independently H or methyl. Without limitation, k can be an integer selected from 2 to 6, and further can be 2, 3 or 4. In some embodiments, k is equal to 2. In other embodiments, k is equal to 3. In other embodiments, k is equal to 4. R 01 The definition of can be found above. In some embodiments, R 01 is H. In other embodiments, R 01 It is a methyl group.

[0350] In some embodiments, the structure of U1 is (-C(=O)-O-)k U0 or (-O-) k U0 or a k-valent aromatic group; wherein, U0 is connected to the adjacent oxygen atom through a carbon atom, and U0 is a k-valent alkyl group or a k-valent alkyl group containing one or more ether groups.

[0351] In some embodiments, the k-valent aryl group is a k-valent phenyl group. In this case, the polyene compound is a k-valent phenyl group.

[0352] In some embodiments, the structure of U1 is (-C(=O)-O-) k In some embodiments, the polyene compound comprises an acrylate polyene compound. In some embodiments, the terminal alkenyl group in the acrylate polyene compound constitutes a part of the acrylate group, and may further constitute a part of the acrylate group or the methacrylate group.

[0353] In some embodiments, the structure of U1 is (-O-) k In some embodiments, the polyene compound comprises an ether polyene compound.

[0354] In this application, unless otherwise specified, “polyene compound” and “polyene compound” have the same meaning and can be used interchangeably.

[0355] In some embodiments, the structure of U1 is a divalent phenyl group. In some embodiments, the polyene compound comprises divinylbenzene.

[0356] In this application, unless otherwise specified, "ether group" has a well-known meaning in the art and refers to an oxy group (-O-) connected to two carbon atoms. Unless otherwise specified, the k terminal atoms of a "k-valent alkyl group containing one or more ether groups" are all carbon atoms.

[0357] Without limitation, the polyene compound may include, but is not limited to, one or more of ethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,4-butanediol diacrylate, glycerol dimethacrylate, 1,2-propylene glycol dimethyl acrylate, 1,3-butanediol dimethacrylate, dipropylene glycol diacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, glycerol trimethacrylate, triallyl trimesate, cyclohexanetriol trimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, and pentaerythritol tetramethacrylate. See also the above definition.

[0358] In some embodiments, the polymerizable monomer includes a monoolefin compound. Without limitation, the monoolefin compound may include but is not limited to CH2=C(R0)-R A 、 One or more of; R0 is H or methyl; R A -COOH, -C(=O)-O-R3, -CH(-OR 41 )(-OR 42 ), cyano or phenyl; R3 is C 1-6 Alkyl, substituted C 1-6 Alkyl, tri(C 1-6 Hydrocarbon)silyl or tri(C 1-6 Hydrocarbyloxy)silyl; R 41 and R 42 Each independently is C 1-3 Alkyl (optionally methyl, ethyl or propyl, further preferably methyl or ethyl, further preferably); substituted C 1-6 C in the alkyl group 1-6 The alkyl group is substituted by one or more substituents selected from the group consisting of -OH, halogen, epoxy and cyano. Without limitation, the halogen group may be fluorine, chlorine or bromine, optionally fluorine. 1-6 Alkyl, substituted C 1-6 The "C" in the alkyl group 1-6 "Alkyl" can be each independently but not limited to C 1-4 Alkyl, optionally C 1-3 Alkyl can also be methyl, ethyl or propyl. 1-6 Hydrocarbon) silicon group "C 1-6 The hydrocarbon group may be, but is not limited to, C 1-6 Alkyl, further C 1-4 Alkyl, further can be C 1-3 Alkyl can also be methyl, ethyl or propyl. 1-6 "C" in the alkoxy) silicon group 1-6 The "alkoxy" may be but is not limited to "C 1-6 "Alkoxy" can further be methoxy, ethoxy or propoxy, and can further be methoxy.

[0359] In some embodiments, R3 is C 1-6 Alkyl, can also be but not limited to C 1-4 Alkyl, optionally C 1-3 The alkyl group may also be methyl, ethyl or propyl.

[0360] In some embodiments, R0 is H. In other embodiments, R0 is methyl.

[0361] Without limitation, the monoolefin compound may include, but is not limited to, one or more of styrene, vinylene carbonate, vinylethylene carbonate, methyl methacrylate, methyl acrylate, ethyl acrylate, acrylic acid, trimethylsilyl methacrylate, acrolein dimethyl acetal, acrolein diethyl acetal, 2-phenoxyethyl acrylate, 3-perfluorohexyl-2-hydroxypropyl acrylate, trifluoroethyl acrylate, trifluoroethyl methacrylate, allyl-1,3-sultone, glycidyl methacrylate, acrylamide, (acryloxymethyl)dimethylmethoxysilane, cyanoethyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, 3-(perfluoro-3-methylbutyl) 2-hydroxypropyl acrylate, pentafluorophenol acrylate, and acrylonitrile.

[0362] In some embodiments, the polymerizable monomer is an ester compound. In a non-limiting manner, any one of the ester structures in the ester compound can independently be methyl ester, ethyl ester, propyl ester, trifluoroethyl ester, trimethylsilyl ester, 2-phenoxyethyl ester, glycidyl ester, cyanoethyl ester, hydroxyethyl ester, hydroxypropyl ester or pentafluorophenol ester. In some embodiments, any one of the ester structures in the ester compound can independently be one or more of methyl ester, ethyl ester and propyl ester. In some embodiments, the ester structure in the ester compound is methyl ester.

[0363] Without limitation, the initiator may include, but is not limited to, one or more of an azo initiator and a peroxide initiator.

[0364] In some embodiments, the initiator comprises an azo initiator. Without limitation, the azo initiator may include but is not limited to one or more of azobisisobutyronitrile, dimethyl azobisisobutyrate, and azobisisoheptanenitrile.

[0365] In some embodiments, the initiator comprises a peroxide initiator. In a non-limiting manner, the peroxide initiator may include but is not limited to didodecanoyl peroxide, dibenzamide peroxide, di(2,4-dichlorobenzoyl) peroxide, diacetyl peroxide, dioctanoyl peroxide, dilauroyl peroxide, peroxydicarbonate, diisopropyl peroxydicarbonate, diisobutyl peroxydicarbonate, dicyclohexyl peroxydicarbonate and one or more of di(p-tert-butylcyclohexyl)peroxydicarbonate.

[0366] In a third aspect of the present application, a method for preparing a secondary battery is provided, comprising the following steps:

[0367] S100: Providing an electrode assembly located inside a housing, the electrode assembly comprising a plurality of electrode sheets and a separator, the plurality of electrode sheets comprising a positive electrode sheet and a negative electrode sheet, the positive electrode sheet and the negative electrode sheet being separated by the separator; each electrode sheet independently comprising an electrode active material layer;

[0368] S200: injecting the gel electrolyte precursor solution described in the second aspect of the present application into the interior of the housing, and maintaining the temperature at an infiltration temperature T1 so that the gel electrolyte precursor solution infiltrates the plurality of electrode plates;

[0369] S300: forming at a forming temperature T2;

[0370] S400: subjecting the described gel electrolyte precursor solution to a free radical polymerization reaction at a curing temperature T3 to generate a gel electrolyte, thereby preparing the secondary battery described in the first aspect of the present application; wherein, the gel electrolyte includes a first gel electrolyte located inside the electrode active material layer and a second gel electrolyte located outside the plurality of electrode plates, the first gel electrolyte and the second gel electrolyte each independently including a cross-linked polymer formed by polymerized monomers, a gelling solvent and at least a portion of an electrolyte salt, and the gelling solvent includes at least a portion of an electrolyte solvent.

[0371] By utilizing the inhibitory effect of the polymerization inhibitor contained in the gel electrolyte precursor, the curing reaction can be suppressed during the electrode plate wetting and formation stages, thereby controlling the occurrence time of the curing reaction and improving the wetting effect of the gel electrolyte precursor on the inside of the electrode plate, thereby promoting the full distribution of the gel electrolyte precursor inside the electrode plate, promoting the full contact and infiltration of the precursor and the electrode active particles, optimizing the transmission channel of the active ions, thereby promoting the capacity of the positive electrode plate, the negative electrode plate and the battery cell, and also helping to suppress the problem of lithium plating at the negative electrode interface and improve the cycle performance of the battery.

[0372] In some embodiments, the electrolyte salt in the gel electrolyte precursor solution includes an electrolyte lithium salt.

[0373] In some embodiments, the curing temperature T3 is higher than the soaking temperature T1.

[0374] In some embodiments, the curing temperature T3 is higher than the forming temperature T2.

[0375] In some embodiments, the soaking temperature T1 is 10°C to 60°C, optionally 20°C to 60°C, further optionally 40°C to 60°C, and can also be any of the following temperatures or a range consisting of any two of the following temperatures: 10°C, 15°C, 20°C, 30°C, 40°C, 50°C, 60°C, etc. Without limitation, in the step of soaking the plurality of electrode sheets by soaking the gel electrolyte precursor solution at the soaking temperature T1, the soaking time can be 24 hours to 48 hours, and can also be any of the following durations or a range consisting of any two of the following durations: 24 hours, 28 hours, 30 hours, 32 hours, 35 hours, 36 hours, 40 hours, 45 hours, 48 ​​hours, etc.

[0376] In some embodiments, the formation temperature T2 is 40°C to 60°C, and can also be any one of the following temperatures or a range consisting of any two of the following temperatures: 40°C, 45°C, 50°C, 55°C, 60°C, etc.

[0377] In some embodiments, the curing temperature T3 is 50°C to 80°C, optionally 60°C to 80°C, or any of the following temperatures or a range consisting of any two of the following temperatures: 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C, etc.

[0378] In some embodiments, in the step of subjecting the gel electrolyte precursor solution to a free radical polymerization reaction at a curing temperature T3 to generate a gel electrolyte, the reaction time for the free radical polymerization reaction is 3 hours to 8 hours, and can also be any of the following time lengths or an interval consisting of any two of the following time lengths: 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, etc.

[0379] In some embodiments, the soaking temperature T1 and the forming temperature T2 are 45°C, and the curing temperature is 70°C.

[0380] In some embodiments, the secondary battery described in the first aspect of the present application is prepared.

[0381] In another aspect of the present application, a secondary battery is provided, which is the secondary battery described in the first aspect of the present application, or a secondary battery prepared by the preparation method of the secondary battery described in the third aspect of the present application, and the secondary battery is a lithium-ion secondary battery.

[0382] In a fourth 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 third aspect of the present application.

[0383] In some embodiments, the present application further provides an electrical device, which includes a secondary battery of any embodiment provided in the present application. The secondary battery can be used as a power source for the electrical device, or as an energy storage unit for the electrical device. The electrical device may include mobile devices, electric vehicles, electric trains, ships and satellites, energy storage systems, etc., but are not limited thereto. Among them, mobile devices may be, for example, mobile phones, laptops, etc.; electric vehicles may be, for example, pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, electric motorcycles, electric tools, etc., but are not limited thereto. The electrical device can also be used in military equipment, aerospace and other fields, and can also be used in energy storage power supply systems such as hydropower, thermal power, wind power and solar power stations.

[0384] As an electrical device, a secondary battery can be selected according to its usage requirements.

[0385] Figure 6 shows an example of an electric device 6. The electric device is a pure electric vehicle, a hybrid electric vehicle, or a plug-in hybrid electric vehicle. To meet the electric device's requirements for high power and high energy density of secondary batteries, a battery pack or battery module may be used.

[0386] Another example device may be a mobile phone, a tablet computer, a notebook computer, etc. Such a device is generally required to be lightweight and thin, and may use a secondary battery as a power source.

[0387] Below, some embodiments of the present application are described. The embodiment described below is exemplary, is only used to explain the present application, and cannot be construed as limiting the present application. In the embodiment, if no technology or conditions are indicated, it is carried out according to the description above, or according to the technology or conditions described in the document in this area, or according to the product specification. Reagents used or instruments that do not indicate manufacturers are conventional products that can be obtained commercially, or can be synthesized in a conventional manner by commercially available products.

[0388] Unless otherwise specified, in the following examples and comparative examples, raw materials with the same chemical formula are from the same synthesis batch or the same product number, or are prepared according to the same stoichiometric ratio and in accordance with the same method.

[0389] In the following examples, room temperature refers to 20°C to 30°C.

[0390] It should be noted that the polymerized monomers involved in the following examples and comparative examples were pretreated by alkali washing (5 wt % NaOH aqueous solution), water washing, distillation and drying before use.

[0391] In the following examples, elemental analysis, structural identification and content analysis of the inhibition residues in the gel electrolyte can be performed by one or more of the following detection methods, including but not limited to: FIB-SEM combined with EDS analysis, Fourier transform infrared (FT-IR) spectroscopy, ultraviolet spectroscopy, hydrogen nuclear magnetic resonance ( 1 H NMR) method, gel permeation chromatography (GPC) method, high performance liquid chromatography (HPLC) method, mass spectrometry method, etc. The sample preparation methods and test methods of these test methods are known to those skilled in the art, and the test parameters can be appropriately adjusted according to the specific structure of the compound and the characteristics of the sample. Unless otherwise specified, the gel electrolyte sample in the positive electrode active material layer, the gel electrolyte sample in the negative electrode active material layer, and the gel electrolyte sample outside the positive and negative electrode sheets can be extracted respectively, and the mass fraction of the inhibition residue at the three locations is obtained and the average value is taken as the test value of the mass fraction of the inhibition residue in the gel electrolyte of the secondary battery.

[0392] Example 1.

[0393] (1) Preparation of negative electrode sheet

[0394] A silicon-carbon composite negative electrode material (silicon content is 20wt%), a conductive agent (acetylene black), and a binder (carboxymethyl cellulose) are mixed in a weight ratio of 97:2:1, deionized water is added and stirred evenly to obtain a negative electrode slurry; the negative electrode slurry is coated on both sides of the copper foil, dried, cold pressed, and punched to obtain a negative electrode sheet.

[0395] (2) Preparation of positive electrode sheet

[0396] The nickel-cobalt-manganese ternary positive electrode material (NCM811), the conductive agent acetylene black, and the binder polyvinylidene fluoride (PVDF) are thoroughly stirred and mixed in an N-methylpyrrolidone (NMP) solvent system in a weight ratio of 94:3:3, and then coated on both sides of the aluminum foil. The cathode sheet is then dried and cold-pressed to obtain the cathode sheet, which is then cut into corresponding sizes for later use.

[0397] (3) Selection of isolation membrane

[0398] The isolation film is a polyolefin PE isolation film coated with a double-sided aluminum oxide layer.

[0399] (4) Preparation of dry cells

[0400] The negative electrode sheet, isolation membrane and positive electrode sheet obtained by punching are stacked in sequence to obtain an electrode assembly, and then glued, connected to the electrode ears, packaged with aluminum-plastic film, and hot pressed to obtain a dry battery cell with one side open in the form of a small soft package.

[0401] (5) Preparation of gel electrolyte precursor solution

[0402] The carbonate solvents ethylene carbonate (EC), diethyl carbonate (DEC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of EC:

[0403] DEC:EMC=1:1:1 mixture, stir evenly, add 1.0mol / L lithium hexafluorophosphate, dissolve to form basic electrolyte. Add 10wt% polyethylene glycol diacrylate monomer (weight average molecular weight M w The precursor solution of the gel electrolyte was prepared by mixing 1000 ppm (corresponding to 0.1 wt%) of hydroquinone with a mass fraction of about 500 Da and 0.2 wt% of azobisisobutyronitrile as an initiator.

[0404] Among them, the calculation basis of the weight proportion of the polymerization monomer (polyethylene glycol diacrylate), the weight proportion of the initiator (azobisisobutyronitrile initiator) and the mass fraction of the polymerization inhibitor (hydroquinone) are all the prepared gel electrolyte precursor solution.

[0405] (6) Preparation of cells containing gel electrolyte precursor

[0406] The gel electrolyte precursor solution obtained in step (5) is injected into the dry cell obtained in step (4). The injection coefficient is 2.5 g / Ah. After injection, negative pressure is drawn to seal the cell.

[0407] (7) Preparation of gel electrolyte-containing battery cells to obtain secondary batteries.

[0408] The battery cell obtained in step (6) was immersed at 45° C. for 30 hours (h), and chemically formed at 45° C. After the chemical formation, it was high-temperature cured at 70° C. for 5 hours to obtain a battery cell containing a gel electrolyte (a secondary battery, further a lithium-ion secondary battery).

[0409] Example 2-4. Changing the amount of polymerization inhibitor

[0410] Examples 2-4 use a method substantially the same as that of Example 1 to prepare gel electrolyte precursors and secondary batteries (containing gel electrolyte cells), except that the amounts of polymerization inhibitors used are different and the amount of hydroquinone added in step (5) is changed.

[0411] Example 5-7. Changing the type of polymerization inhibitor

[0412] Examples 5-7 use a method basically the same as Example 1 to prepare a gel electrolyte precursor solution and a secondary battery (containing a gel electrolyte cell), except that the types of polymerization inhibitors are different, and the hydroquinone in step (5) is replaced by 2-nitrohydroquinone (Example 5), catechol (Example 6), and p-tert-butylcatechol (Example 7), respectively.

[0413] Examples 8-14. Changing one or more parameters of the type, molecular weight, amount of the polymerization monomer and the type and amount of the initiator.

[0414] Examples 8-14 use methods substantially the same as those of Example 1 to prepare gel electrolyte precursors and secondary batteries (including gel electrolyte cells), with the difference being that one or more parameters including the type, molecular weight, and amount of the polymerization monomer and the type and amount of the initiator are different.

[0415] In Example 13, the initiator BPO is dibenzoyl peroxide.

[0416] Comparative Examples 1-5: No polymerization inhibitor was added.

[0417] Comparative Examples 1-5 respectively use methods basically the same as those in Example 1, Example 11, Example 12, Example 13 and Example 14 to prepare gel electrolyte precursor solutions and secondary batteries (containing gel electrolyte cells), except that no polymerization inhibitor is added and the basic electrolyte in Example 1 is used instead of the gel electrolyte precursor solution.

[0418] The parameters of Examples 1-14 and Comparative Examples 1-5 can also be referred to Table 1, Table 2 and Table 3. In the "Molecular Weight" column, when the polyene compound has polyethylene glycol units, the corresponding weight average molecular weight M w , “about 500 Da” means ±10 Da.

[0419] Table 1.

[0420] Table 2.

[0421] Table 3. Relevant parameters in gel electrolyte precursor solution

[0422] Testing and analysis methods

[0423] 1. Material structure and composition testing methods

[0424] Define the filling factor of gel electrolyte in the positive electrode active material layer Filling factor of gel electrolyte in negative electrode active material layer V P1 、V P2 、 V N1 、V N2 and The definition of can be found in the previous text. P , α N The theoretical value range of α is 0 to 1. When the value is 0, there is no gel electrolyte in the electrode, and when the value is 1, the electrode is completely filled. P , α N The higher the value of , the more fully the gel electrolyte is distributed inside the electrode plate.

[0425] The α-active material layer of the positive electrode located at the innermost side of the electrode assembly P Denoted as α P0 , the α of the negative active material layer located at the innermost side of the electrode assembly N Denoted as α N0 α P0 and α N0 The higher it is, the more fully the gel electrolyte is distributed inside the electrode plate.

[0426] Prepare the electrode active material layer samples to be tested using the following method: discharge the secondary battery to the nominal lower voltage limit, then disassemble the battery cell to obtain the positive and negative electrode sheets. Then, extract the positive and negative active material layer samples to be tested. The nominal lower voltage limit can be determined using conventional testing methods or according to the manufacturer's definition.

[0427] The following parameters of the local area of ​​the electrode active material layer were obtained by focusing electron beam (FIB) technology, scanning electron microscope (SEM) test analysis, and combined with focusing electron beam (FIB) continuous sectioning, energy dispersive spectroscopy (EDS) element spectrum and three-dimensional reconstruction analysis software, and then the α P , α N , α P0 and α N0 Test value: quality M of the local area i and volume V i , the mass M of the gel electrolyte in the local area i1 and volume V i1 , the porosity of the local area Fill factor of local area

[0428] For α P and α N , several (≥3) local areas of the electrode active material layer are selected at at least three radial positions of the electrode assembly, and "at least three radial positions" include at least the innermost side, the outermost side, and the middle part between the innermost side and the outermost side of the electrode assembly.

[0429] For α P0 and α N0 Several (≥3) local areas of the electrode active material layer are selected at different transverse positions on the innermost side of the electrode assembly, and "transverse" refers to a direction perpendicular to the thickness direction of the corresponding electrode active material layer.

[0430] The lateral area of ​​the "local region of the electrode active material layer" is greater than or equal to 25 μm 2 , thickness is greater than or equal to 10μm.

[0431] You can also get a CV Pi 、CV Ni 、CV Pj 、CV Nj The statistical analysis results (the definitions of these parameters can be found in the previous article) are used to analyze the distribution uniformity of the gel electrolyte in the positive and negative electrodes at different lateral positions and at different electrode thickness positions.

[0432] The above parameters were tested and analyzed using a FEI Scios 2HiVac instrument. The detailed method employed was as follows: Utilizing the nanometer spatial dynamic resolution of a FIB-SEM and layer-by-layer cutting technology, the three-dimensional structure of the sample was reconstructed. EDS elemental spectroscopy was then used to determine the distribution and proportion of each element. Finally, software-based quantitative analysis yielded the relevant parameters.

[0433] 2. Test and analysis of the inhibitory effect of the inhibitor on the gelation reaction system (gel electrolyte precursor solution).

[0434] (1) Determine whether the inhibitor has an inhibitory effect during the test period.

[0435] The viscosity of the gel electrolyte precursor solution was measured using the following method: a certain mass of the sample to be tested was placed in a sample container and tested using a Brookfield DV2TLV rotational viscometer. At 25°C, the shear force exerted on the rotor as it rotated continuously at a constant speed within the sample caused a spring torque to be generated. This torque is proportional to the viscosity, providing the viscosity value. The test equipment met the following environmental conditions: 1. External environment: Temperature: 25°C, Humidity: RH <80%; 2. Internal environment: The sample container was two-thirds submerged in a water bath containing water, which was used to maintain the sample temperature.

[0436] Obtaining the test sample: The initial viscosity η0 of the prepared gel electrolyte precursor to be tested is tested; the gel electrolyte precursor to be tested is packaged at a negative pressure of 5kPa, then kept at 45°C for 1200 minutes, cooled to 25°C and the viscosity η1 is tested. The "increase ratio of the system viscosity" Rη = (η1-η0) / η0×100%.

[0437] Analysis method: When Rη ≤ 20%, the inhibitor is considered to have an inhibitory effect during the test period (5kPa, 45°C, 1200 minutes). This means that the requirement of "at 45°C, the inhibitor inhibits the free radical polymerization system for a time greater than or equal to 1200 minutes (20 hours)" is met. If the system shows a significant viscosity change or a distinct non-flowing gel phase, the inhibitor's inhibitory effect is considered to have failed.

[0438] (2) Determine whether a free radical polymerization reaction has occurred in the free radical polymerization system.

[0439] Acquisition of test samples: The chemical composition of the polymerized monomers in the initial state of the prepared gel electrolyte precursor solution to be tested was tested; the gel electrolyte precursor solution to be tested was sealed at a negative pressure of 5kPa, then kept at 70°C for 600 minutes, and then cooled to 25°C to test the formation of cross-linked polymers.

[0440] The following method was used to test the chemical composition changes of the gel electrolyte precursor solution: According to the hydrogen nuclear magnetic resonance ( 1 The "whether a cross-linked polymer is formed" is analyzed by at least one method selected from the group consisting of H NMR, gel permeation chromatography (GPC), and high performance liquid chromatography (HPLC).

[0441] Analytical method: When H NMR ( 1When characteristic peaks of cross-linked polymers appear in H NMR (e.g., the characteristic peak of methylene hydrogen in -CH2-C(CH3)(COOCH3)- appears in the methyl methacrylate system), or when characteristic peaks of polymers other than monomers appear in gel permeation chromatography (GPC) or high-performance liquid chromatography (HPLC), it is considered whether "cross-linked polymers have been formed" and furthermore, it is considered that "free radical polymerization has occurred in the free radical polymerization system."

[0442] 3. Test and analysis of battery capacity utilization rate and capacity retention rate.

[0443] The theoretical design capacity of the battery's positive electrode is designated as C0. The battery is cycled between 2.8V and 4.3V at a charge / discharge rate of 0.5C. The discharge capacity of the battery at the first cycle is defined as C1, and the discharge capacity at the 500th cycle is defined as C2. The capacity utilization rate of the battery cell is then defined as C1 / C0 × 100%, and the capacity retention rate of the battery cell after 500 cycles is defined as C2 / C1 × 100%.

[0444] The test results can be found in Table 4, “Capacity utilization rate” and “Capacity retention rate after 500 cycles”.

[0445] 4. Observation of lithium precipitation

[0446] The battery was charged and discharged between 2.8V and 4.3V at a charge and discharge rate of 0.5C. After 500 cycles, it was fully charged and the battery was disassembled to observe the lithium deposition at the negative electrode interface.

[0447] Test and analysis results

[0448] Inhibitors were added to the gel electrolyte precursors of Examples 1-14, and the electrode assemblies were infiltrated and then cured to prepare secondary batteries containing gel electrolytes. These batteries all had excellent capacity and cycle performance. In addition, after 500 cycles of the secondary batteries prepared in Examples 1-14, no significant lithium deposition was observed at the negative electrode interface.

[0449] However, the gel electrolyte precursor solutions of Comparative Examples 1 to 5 did not contain any polymerization inhibitor. As a result, it was found that lithium deposition was obvious at the negative electrode interface, and the capacity and cycle performance were significantly deteriorated.

[0450] The phenolic polymerization inhibitors used in Examples 1-14 all formed polymerization inhibition residues mainly including quinone residues, wherein the mass fraction of the quinone residues in the prepared gel electrolyte of the secondary battery satisfied 50 ppm to 2000 ppm, and further satisfied 500 ppm to 1000 ppm.

[0451] According to the “Material Structure and Composition Test Method”, the α in Examples 1-14 P , α N , αP0 , α N0 All meet ≥0.9, while α in Comparative Examples 1-5 P , α N All are lower than 0.8, and the α in Comparative Examples 1-5 P0 , α N0 Both are below 0.75.

[0452] It can be seen that after adding the polymerization inhibitor to the gel electrolyte precursor, the wetting effect of the gel electrolyte precursor on the electrode plate is significantly improved, the infiltration of the electrode active material layer is more sufficient, and the capacity and cycle performance of the battery are significantly improved.

[0453] CV according to Examples and Comparative Examples Pi 、CV Ni 、CV Pj 、CV Nj Compared with the analysis results of the , adding the polymerization inhibitor to the gel electrolyte precursor solution improves the distribution uniformity of the resulting gel electrolyte at different lateral locations of the positive and negative electrode sheets, and significantly improves the distribution uniformity of the resulting gel electrolyte at different thickness locations of the positive and negative electrode sheets. For example, the results of Examples 1, 11, 12, 13, and 14 are compared with the corresponding Comparative Examples 1-5.

[0454] The gel electrolyte precursors prepared with the polymerization inhibitors of Examples 1-14 are free radical polymerization systems, and all meet the following two characteristics:

[0455] (1) At 45°C, the polymerization time of the inhibitor in inhibiting the free radical polymerization system is greater than or equal to 1200 minutes;

[0456] (2) At 70°C, the initiator can initiate the free radical polymerization system to undergo free radical polymerization reaction within 600 minutes.

[0457] It can be seen that the introduction of the polymerization inhibitor into the gel electrolyte precursor solution promotes the solidified gel electrolyte to fully contact the electrode active material inside the electrode plate, thereby optimizing the transmission channel of the active ions, promoting the capacity of the positive electrode plate, the negative electrode plate and the battery cell, and is also beneficial to suppressing the problem of lithium plating at the negative electrode interface and improving the cycle performance of the battery.

[0458] Table 4.

[0459] The description of each embodiment and example above tends to emphasize the differences between each embodiment and example, and the same or similar aspects can be referenced to each other. For the sake of brevity, this article will not go into details. The technical features of the embodiments and examples described above can be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments and examples 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. It should be noted that the present application is not limited to the above embodiments and examples. The above embodiments and examples are only examples. Within the scope of the technical solution of this application, embodiments and examples with essentially the same composition as the technical idea and the same effects are included in the technical scope of this application. The above-described embodiments and examples only express several embodiments of the present application, and their descriptions are relatively detailed, but they cannot be understood as limiting the scope of the patent. In addition, without departing from the scope of the subject matter of this application, various modifications that can be thought of by those skilled in the art to the embodiments or examples, and other methods of combining some of the constituent elements in the embodiments or examples are also included in the scope of this application.

Claims

1. A secondary battery comprising a plurality of electrode sheets; the plurality of electrode sheets comprising a positive electrode sheet and a negative electrode sheet; any of the electrode sheets independently comprising an electrode active material layer; The secondary battery includes a gel electrolyte, the gel electrolyte includes a first gel electrolyte and a second gel electrolyte, the first gel electrolyte is located inside the electrode active material layer, and the second gel electrolyte is located outside the plurality of electrode plates; wherein, The first gel electrolyte and the second gel electrolyte each independently include a cross-linked polymer, a gelling solvent, and an electrolyte salt; The cross-linked polymer includes carbon-based chain segments; the gel electrolyte includes an inhibitory residue, which is a substance generated by an inhibitor after inhibiting a free radical polymerization reaction; and the inhibitor includes an inhibitory group capable of terminating the free radical polymerization reaction.

2. The secondary battery according to claim 1, wherein The mass fraction of the polymerization inhibition residue in the gel electrolyte is 50 ppm to 2000 ppm; optionally 500 ppm to 1000 ppm.

3. The secondary battery according to claim 1 or 2, wherein The polymerization inhibitor residue comprises a quinone residue of a phenolic polymerization inhibitor; wherein the phenolic polymerization inhibitor comprises an aromatic ring and a phenolic hydroxyl group directly bonded to the aromatic ring; in one molecule of the phenolic polymerization inhibitor, the polymerization inhibitor group comprises one or more phenolic hydroxyl groups; Optionally, the phenolic polymerization inhibitor includes one or more of the following compounds: phenol, 2,6-di-tert-butylphenol, p-methoxyphenol, 2,6-di-tert-butyl-4-methylphenol, hydroquinone, catechol, 2-nitrohydroquinone, monomethyl hydroquinone, trimethyl hydroquinone, p-tert-butylcatechol, 2,5-di-tert-butylhydroquinone, bisphenol A, 4,4'-dihydroxybiphenyl, 4,4'-butylenebis(6-tert-butyl-3-methylphenol), benzyltriol and 4-bromophenol.

4. The secondary battery according to any one of claims 1 to 3, wherein The cross-linked polymer comprises repeating units formed by free radical polymerization of polymerizable monomers; the polymerizable monomers comprise polyene compounds and may or may not comprise monoene compounds, wherein the polyene compounds have a plurality of polymerizable carbon-carbon double bonds and the monoene compounds have a single polymerizable carbon-carbon double bond; Optionally, the polyene compound includes one or more of ethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,4-butanediol diacrylate, glycerol dimethacrylate, 1,2-propylene glycol dimethyl acrylate, 1,3-butanediol dimethacrylate, dipropylene glycol diacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, glycerol trimethacrylate, triallyl trimesic acid ester, cyclohexanetriol trimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate and pentaerythritol tetramethacrylate.

5. The secondary battery according to any one of claims 1 to 4, wherein The electrode active material layer in the positive electrode sheet is referred to as the positive electrode active material layer, and the electrode active material layer in the negative electrode sheet is referred to as the negative electrode active material layer; The volume of the gel electrolyte in the positive electrode active material layer is denoted as V P1 The volume and porosity of the positive electrode active material layer are respectively denoted as V P2 and definition The volume of the gel electrolyte in the negative electrode active material layer is denoted as V N1 The volume and porosity of the negative electrode active material layer are respectively denoted as V N2 and definition Among them, α P and α N Each independently greater than or equal to 0.85; Optionally, α P and α N are each independently greater than or equal to 0.

9.

6. The secondary battery according to claim 5, wherein The secondary battery includes a separator located between the positive electrode sheet and the negative electrode sheet, and the positive electrode sheet, the negative electrode sheet and the separator constitute an electrode assembly; The α of the positive electrode active material layer located at the innermost side of the electrode assembly P Denoted as α P0 , the α of the negative active material layer located at the innermost side of the electrode assembly N Denoted as α N0 ; Among them, α P0 and α N0 Each independently greater than or equal to 0.85; Optionally, α P0 and α N0 are each independently greater than or equal to 0.

9.

7. A gel electrolyte precursor solution comprising the following components: a free radical polymerization system, an inhibitor, an electrolyte salt, and an electrolyte solvent; in, The free radical polymerization system includes a polymerizable monomer and an initiator, wherein the initiator can initiate a free radical polymerization reaction of the polymerizable monomer to form a cross-linked polymer; and the polymerization inhibitor includes an inhibitory group that can terminate the free radical polymerization reaction of the free radical polymerization system.

8. The gel electrolyte precursor according to claim 7, which satisfies one or more of the following characteristics: The mass percentage of the polymerizable monomer in the gel electrolyte precursor solution is 2% to 15%; The mass fraction of the polymerization inhibitor in the gel electrolyte precursor solution is 50 ppm to 2000 ppm.

9. The gel electrolyte precursor according to claim 7 or 8, which satisfies one or more of the following characteristics: The mass percentage of the polymerizable monomer in the gel electrolyte precursor solution is 8% to 12%; The mass fraction of the polymerization inhibitor in the gel electrolyte precursor solution is 500ppm to 1000ppm.

10. The gel electrolyte precursor solution according to any one of claims 7 to 9, wherein The polymerization inhibitor includes a phenolic polymerization inhibitor; wherein the phenolic polymerization inhibitor includes an aromatic ring and a phenolic hydroxyl group directly bonded to the aromatic ring; in one molecule of the phenolic polymerization inhibitor, the polymerization inhibitor group includes one or more phenolic hydroxyl groups.

11. The gel electrolyte precursor solution according to claim 10, wherein The phenolic polymerization inhibitor meets one or more of the following characteristics: In one molecule, the phenolic polymerization inhibitor contains 1 to 5 phenolic hydroxyl groups; In one molecule, the mass proportion of the phenolic hydroxyl group in the phenolic polymerization inhibitor is 7.5% to 40.5%; In one molecule, the phenolic polymerization inhibitor contains one or more aromatic rings; when the number of the aromatic rings is multiple, adjacent aromatic rings are connected by chemical bonds or -C(R1R2)-, wherein R1 and R2 are each independently H or C 1-4 alkyl; The molecular weight of the phenolic polymerization inhibitor is less than or equal to 1000 Da.

12. The gel electrolyte precursor solution according to claim 10 or 11, wherein The phenolic polymerization inhibitor meets one or more of the following characteristics: In one molecule, the phenolic polymerization inhibitor contains 1, 2 or 3 phenolic hydroxyl groups; In one molecule, the mass proportion of the phenolic hydroxyl group in the phenolic polymerization inhibitor is 8% to 35%; In one molecule, the phenolic polymerization inhibitor contains 1 or 2 aromatic rings; when the number of the aromatic rings is multiple, adjacent aromatic rings are connected by chemical bonds or -C(R1R2)-, wherein R1 and R2 are each independently H or C 1-3 Alkyl, and -C(R1R2)- has 1 to 4 carbon atoms; The molecular weight of the phenolic polymerization inhibitor is less than or equal to 500 Da.

13. The gel electrolyte precursor solution according to any one of claims 10 to 12, wherein Any aromatic ring in the phenolic polymerization inhibitor is independently connected with 0, 1 or more non-hydroxyl substituents selected from the following groups: halogen, nitro, C 1-4 Alkyl and C 1-3 Alkoxy.

14. The gel electrolyte precursor solution according to any one of claims 10 to 13, wherein Any aromatic ring in the phenolic polymerization inhibitor is independently connected with 0, 1 or more non-hydroxy substituents selected from the following group: halogen and nitro; the halogen is selected from one or more of fluorine, chlorine and bromine.

15. The gel electrolyte precursor solution according to any one of claims 10 to 13, wherein The phenolic polymerization inhibitor includes one or more of the following compounds: phenol, 2,6-di-tert-butylphenol, p-methoxyphenol, 2,6-di-tert-butyl-4-methylphenol, hydroquinone, catechol, 2-nitrohydroquinone, monomethyl hydroquinone, trimethyl hydroquinone, p-tert-butylcatechol, 2,5-di-tert-butylhydroquinone, bisphenol A, 4,4'-dihydroxybiphenyl, 4,4'-butylenebis(6-tert-butyl-3-methylphenol), pyrogallol and 4-bromophenol.

16. The gel electrolyte precursor according to any one of claims 7 to 15, which satisfies one or more of the following characteristics: The mass ratio of the initiator to the polymerization monomer is 0.5% to 10%; The mass ratio of the polymerization inhibitor to the initiator is 0.1% to 50%; The mass ratio of the polymerization inhibitor groups in the polymerization inhibitor to the initiator is 0.01% to 15%.

17. The gel electrolyte precursor according to claim 16, which satisfies one or more of the following characteristics: The mass ratio of the initiator to the polymerization monomer is 0.5% to 5%; The mass ratio of the polymerization inhibitor to the initiator is 0.1% to 20%; The mass ratio of the polymerization inhibitor groups in the polymerization inhibitor to the initiator is 0.05% to 5%.

18. The gel electrolyte precursor according to any one of claims 7 to 17, which satisfies one or more of the following characteristics: The polymerizable monomers include polyolefin compounds and may include or exclude monoolefin compounds, wherein: The polyene compound has a plurality of polymerizable carbon-carbon double bonds, and the monoene compound has one polymerizable carbon-carbon double bond; The initiator includes one or more of an azo initiator and a peroxide initiator.

19. The gel electrolyte precursor according to any one of claims 18, which satisfies one or more of the following characteristics: The structure of the polyene compound is [CH2=C(R 01 )-] k U1, k is an integer greater than or equal to 2, U1 is a k-valent non-aromatic group or a k-valent aromatic group; R 01 Each occurrence is independently H or methyl; The polymerizable monomers include monoolefin compounds, and the monoolefin compounds include CH2=C(R0)-R A 、 One or more of; R0 is H or methyl; R A -COOH, -C(=O)-O-R3, -CH(-OR 41 )(-OR 42 ), cyano or phenyl; R3 is C 1-6 Alkyl, substituted C 1-6 Alkyl, tri(C 1-6 Hydrocarbon)silyl or tri(C 1-6 Hydrocarbyloxy)silyl; R 41 and R 42 Each independently is C 1-3 Alkyl; the substituted C 1-6 C in the alkyl group 1-6 The alkyl group is substituted with one or more substituents selected from the group consisting of -OH, halo, epoxy, and cyano; The initiator includes an azo initiator, and the azo initiator includes one or more of azobisisobutyronitrile, dimethyl azobisisobutyrate and azobisisoheptanenitrile; The initiator includes a peroxide initiator, and the peroxide initiator includes one or more of didodecanoyl peroxide, dibenzamide peroxide, di(2,4-dichlorobenzoyl) peroxide, diacetyl peroxide, dioctanoyl peroxide, dilauroyl peroxide, peroxydicarbonate, diisopropyl peroxydicarbonate, diisobutyl peroxydicarbonate, dicyclohexyl peroxydicarbonate and di(p-tert-butylcyclohexyl) peroxydicarbonate.

20. The gel electrolyte precursor solution according to claim 19, wherein The structure of U1 is (-C(=O)-O-) k U0 or (-O-) k U0 or k valent aromatic group; Wherein, U0 is connected to the adjacent oxygen atom through a carbon atom, and U0 is a k-valent alkyl group or a k-valent alkyl group containing one or more ether groups.

21. The gel electrolyte precursor solution according to any one of claims 18 to 19, wherein The polymerizable monomer satisfies one or more of the following characteristics: The polyene compound includes one or more of ethylene glycol diacrylate, ethylene glycol dimethacrylate, polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, 1,4-butanediol dimethacrylate, 1,6-hexanediol dimethacrylate, 1,4-butanediol diacrylate, glycerol dimethacrylate, 1,2-propylene glycol dimethyl acrylate, 1,3-butanediol dimethacrylate, dipropylene glycol diacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, glycerol trimethacrylate, triallyl trimesic acid ester, cyclohexanetriol trimethacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate and pentaerythritol tetramethacrylate; The monoolefin compound includes one or more of styrene, vinylene carbonate, vinyl ethylene carbonate, methyl methacrylate, methyl acrylate, ethyl acrylate, acrylic acid, trimethylsilyl methacrylate, acrolein dimethyl acetal, acrolein diethyl acetal, 2-phenoxyethyl acrylate, 3-perfluorohexyl-2-hydroxypropyl acrylate, trifluoroethyl acrylate, trifluoroethyl methacrylate, propenyl-1,3-sultone, glycidyl methacrylate, acrylamide, (acryloxymethyl) dimethylmethoxysilane, cyanoethyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, 3-(perfluoro-3-methylbutyl) 2-hydroxypropyl acrylate, pentafluorophenol acrylate and acrylonitrile; The polymerizable monomer is an ester compound, and any ester structure in the ester compound is independently methyl ester, ethyl ester, propyl ester, trifluoroethyl ester, trimethylsilyl ester, 2-phenoxyethyl ester, glycidyl ester, cyanoethyl ester, hydroxyethyl ester, hydroxypropyl ester or pentafluorophenol ester.

22. The gel electrolyte precursor solution according to any one of claims 7 to 21, wherein At 45° C., the polymerization inhibitor inhibits the free radical polymerization system for a time greater than or equal to 1200 min; At 70° C., the initiator can initiate the free radical polymerization system to perform a free radical polymerization reaction within 600 minutes.

23. A method for preparing a secondary battery, comprising the following steps: Providing an electrode assembly located inside the housing, the electrode assembly comprising a plurality of electrode sheets and a separator, the plurality of electrode sheets comprising a positive electrode sheet and a negative electrode sheet, the positive electrode sheet and the negative electrode sheet being separated by the separator; each of the electrode sheets independently comprising an electrode active material layer; injecting the gel electrolyte precursor solution according to any one of claims 7 to 22 into the interior of the housing, and maintaining the temperature at an infiltration temperature T1 so that the gel electrolyte precursor solution infiltrates the plurality of electrode plates; Performing chemical formation at a chemical formation temperature T2; The gel electrolyte precursor solution is subjected to a free radical polymerization reaction at a curing temperature T3 to generate a gel electrolyte, thereby preparing the secondary battery; wherein, The gel electrolyte includes a first gel electrolyte located inside the electrode active material layer and a second gel electrolyte located outside the plurality of electrode plates, the first gel electrolyte and the second gel electrolyte each independently including a cross-linked polymer formed from the polymerized monomer, a gelling solvent, and at least a portion of the electrolyte salt, the gelling solvent including at least a portion of the electrolyte solvent.

24. The method for preparing a secondary battery according to claim 23, which satisfies one or more of the following characteristics: The electrolyte salt in the gel electrolyte precursor solution includes an electrolyte lithium salt; The curing temperature T3 is higher than the soaking temperature T1; The curing temperature T3 is higher than the formation temperature T2; The soaking temperature T1 is 10°C to 60°C; The formation temperature T2 is 40°C to 60°C; The curing temperature T3 is 50°C to 80°C; In the step of maintaining the temperature at the infiltration temperature T1 so that the gel electrolyte precursor solution infiltrates the plurality of electrode sheets, the infiltration time is 24 hours to 48 hours; In the step of subjecting the gel electrolyte precursor solution to a free radical polymerization reaction at a curing temperature T3 to generate a gel electrolyte, the reaction time of the free radical polymerization reaction is 3 hours to 8 hours; The secondary battery according to any one of claims 1 to 6 is prepared. 25 . A secondary battery, which is the secondary battery according to claim 1 , or the secondary battery prepared by the method for preparing a secondary battery according to claim 23 or 24 , wherein the secondary battery is a lithium ion secondary battery.

26. An electrical device comprising at least one of the secondary battery according to any one of claims 1 to 6 and 25 and the secondary battery prepared by the preparation method according to claim 23 or 24.

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