Gel electrolyte electrode, separator, lithium ion battery, and preparation methods therefor

Abstract

The present invention relates to a gel electrolyte electrode, a separator, a lithium ion battery, and preparation methods therefor. A gel electrolyte lithium ion battery comprises a positive electrode, a negative electrode, a separator, and an electrolyte; at least one of the positive electrode, the negative electrode or the separator comprises a polymer having a boron cross-linked structure; the boron cross-linked structure of the polymer is as shown in one or more of formula 1, formula 2, formula 3 and formula 4, wherein R1 is selected from hydroxyl, alkyl, aryl or heteroaryl, X1, X2 and X3 are each independently selected from one of O and NR2, and R2 is a hydrogen atom or alkyl. The polymer having the boron cross-linked structure can well absorb the electrolyte to swell to form a gel electrolyte, thereby preventing the electrolyte from leaking, and reducing the contact between the electrolyte and an active substance, reducing decomposition of the electrolyte, and improving the high-temperature storage performance and safety of the lithium ion battery.

Description

Gel electrolyte electrode, separator and lithium ion battery and their preparation methods

[0001] Related applications

[0002] This application claims priority to the prior application document with application number 202310790546.0 filed in China on June 29, 2023, and incorporates its entire contents into this document. Technical Field

[0003] The present invention relates to the field of lithium ion batteries, and in particular to a gel electrolyte electrode, a diaphragm and a lithium ion battery and a preparation method thereof. Background Art

[0004] In lithium-ion batteries, using gel electrolytes instead of traditional liquid electrolytes has two advantages: first, it prevents leakage of the electrolyte, reduces the volatilization of the electrolyte solvent, reduces the amount of solvent used, and reduces the risk of combustion and explosion, thereby improving safety performance; second, it reduces the contact between the electrolyte and the surface of the active material, thereby inhibiting the decomposition of the electrolyte, extending the battery life, and also helping to improve safety performance.

[0005] The application of gel electrolytes in lithium-ion batteries mainly includes the following two methods. The first application method is to add a partially crystalline polymer to the electrolyte precursor to form a viscous liquid and apply it to the electrode. The low-boiling point solvent in the electrolyte precursor is then extracted to allow the polymer and the electrolyte to form a physically cross-linked gel. The representative polymer is the copolymer of vinylidene fluoride and hexafluoropropylene P (VDF-co-HFP), and the company that commercializes it is Sony; the second application method is to add a monomer or oligomer containing multiple double bond functional groups together with an initiator to the electrolyte, and then inject the electrolyte into the dry battery cell, and then initiate double bond polymerization by heating or ultraviolet light irradiation to convert the electrolyte into a chemically cross-linked gel, which is the so-called in situ polymerization method. Representative monomers or oligomers are various monomers or oligomers containing acrylate groups or methacrylate groups, and the representative company that commercializes them is Samsung.

[0006] The first application method mentioned above offers a limited selection of polymers, with the only successful example being Sony's PVDF copolymer. However, this approach presents two major challenges: first, the complex process leads to high costs; second, the gel electrolyte contains virtually no low-boiling-point solvents, resulting in low conductivity and limiting the battery's rate capability and low-temperature performance. The second application method offers a wider range of monomers or oligomers, but this approach also presents two major challenges: first, the electrolyte easily gels, requiring only short-term storage at low temperatures; and second, the high viscosity of electrolytes containing monomers or oligomers makes it difficult for the electrolyte to fully penetrate the pores in the electrode, making it incompatible with the low-porosity electrodes required for high-energy-density batteries.

[0007] Summary of the Invention

[0008] The problem to be solved by the present invention is that the production process of gel electrolyte lithium ion batteries in the prior art is complex, the electrolyte is unstable, it is difficult to fully infiltrate the electrodes, the preparation cost is high, and it cannot meet the production requirements of high energy density batteries.

[0009] In response to the above problems, one of the objectives of the present invention is to provide a gel electrolyte lithium ion battery comprising a polymer having a boron cross-linked structure and a preparation method thereof. A second objective of the present invention is to provide a gel electrolyte electrode comprising a polymer having a boron cross-linked structure and a preparation method thereof. A third objective of the present invention is to provide a separator comprising a polymer having a boron cross-linked structure and a preparation method thereof.

[0010] In order to solve the above problems, the technical solutions of the present invention are as follows:

[0011] In a first aspect, in a specific embodiment of the present invention, the present invention provides a gel electrolyte lithium ion battery, comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein at least one of the positive electrode, the negative electrode or the separator comprises a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3 and 4:

[0012] Wherein R1 is selected from one of hydroxyl, alkyl or phenyl, X1, X2, X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or an alkyl.

[0013] In some embodiments of the present invention, the polymer having a boron cross-linked structure is obtained by reacting a boric acid compound with a polymer containing an active hydrogen functional group; preferably, the boric acid compound includes one or more of boric acid, phenylboric acid, phenyldiboric acid, 1,3,5-benzenetriboric acid, alkylboric acid, naphthaleneboric acid and heteroarylboronic acid.

[0014] In some embodiments of the present invention, the polymer having a boron cross-linked structure is obtained by reacting a boric acid compound with a polymer containing an active hydrogen functional group; preferably, the boric acid compound includes one or more of boric acid, phenylboric acid and alkylboric acid.

[0015] Preferably, the polymer containing active hydrogen functional groups includes one or more of hydroxyl-containing polymers, carboxyl-containing polymers, sulfonic acid-containing polymers, sulfuric acid-containing polymers, phosphoric acid-containing polymers, amino-containing polymers and substituted amino-containing polymers.

[0016] In some embodiments of the present invention, the polymer containing active hydrogen functional groups includes one or more of polyolefins containing active hydrogen functional groups, polyethers containing active hydrogen functional groups, polyesters containing active hydrogen functional groups, polyamides containing active hydrogen functional groups, and polycarbonates containing active hydrogen functional groups.

[0017] The polymer in the polymer containing active hydrogen functional groups includes one or more of polyolefins, polyethers, polyesters, polyamides and polycarbonates.

[0018] In some embodiments of the present invention, at 25-60° C., the swelling degree of the polymer having a boron cross-linked structure in the electrolyte is greater than 50%, preferably the swelling degree is 50-10000%; preferably, the swelling loss rate of the polymer having a boron cross-linked structure in the electrolyte is less than 5%.

[0019] In some embodiments of the present invention, the positive electrode includes a current collector and a positive electrode coating material coated on the current collector; preferably, the positive electrode coating material includes a positive electrode active material and a polymer having a boron cross-linked structure;

[0020] And / or, the negative electrode comprises a current collector and a negative electrode coating material coated on the current collector; preferably, the negative electrode coating material comprises a negative electrode active material and a polymer having a boron cross-linked structure;

[0021] And / or, the separator includes a polymer porous membrane and a separator coating material coated on the polymer porous membrane; preferably, the separator coating material includes inorganic particles and a polymer having a boron cross-linked structure.

[0022] In some embodiments of the present invention, the electrolyte comprises an organic solvent and a lithium salt; preferably, the organic solvent is selected from one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and methyl propyl carbonate;

[0023] More preferably, the lithium salt is selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonyl)imide and lithium bis(fluorosulfonyl)imide, preferably lithium hexafluorophosphate.

[0024] The electrolyte further comprises one or more of unsaturated cyclic carbonate, fluorinated cyclic carbonate, cyclic sultone and cyclic sulfate;

[0025] Preferably, the unsaturated cyclic carbonate is selected from vinylene carbonate and / or vinyl ethylene carbonate;

[0026] and / or, the fluorinated cyclic carbonate is selected from at least one of fluoroethylene carbonate, trifluoromethylethylene carbonate or bisfluoroethylene carbonate;

[0027] and / or, the cyclic sultone is selected from at least one of 1,3-propane sultone, 1,4-butane sultone and propenyl-1,3-sultone;

[0028] And / or, the cyclic sulfate is selected from at least one of vinyl sulfate, propylene sulfate, and 4-methylvinyl sulfate.

[0029] In a second aspect, the present invention provides a method for preparing the above-mentioned gel electrolyte lithium ion battery, comprising the following steps: forming a battery core with a positive electrode, a negative electrode, and a separator, placing the battery core in a battery housing, injecting an electrolyte to obtain a semi-finished lithium ion battery, forming and exhausting the semi-finished lithium ion battery, and then sealing the liquid injection port of the battery housing to obtain a gel electrolyte lithium ion battery;

[0030] Wherein, at least one of the positive electrode, negative electrode or separator is prepared according to the following method:

[0031] (1) The positive electrode is prepared by mixing a boric acid compound and a polymer containing an active hydrogen functional group with a positive electrode slurry, coating the slurry on a current collector, and then drying to obtain the positive electrode;

[0032] (2) The negative electrode is prepared by mixing a boric acid compound and a polymer containing an active hydrogen functional group with a negative electrode slurry, coating the slurry on a current collector, and then drying to obtain the negative electrode;

[0033] (3) The diaphragm is prepared by the following steps: mixing a boric acid compound and a polymer containing an active hydrogen functional group with a diaphragm slurry, then coating the slurry on a polymer porous membrane, and then drying to obtain the diaphragm;

[0034] Preferably, the drying temperature is 60-120°C;

[0035] More preferably, based on 100% of the total weight of the positive electrode slurry, the weight percentage of the sum of the weight of the boric acid compound and the polymer containing active hydrogen functional groups is 1-10%; and / or,

[0036] Based on the total weight of the negative electrode slurry being 100%, the sum of the weight of the boric acid compound and the polymer containing active hydrogen functional groups is 1-10% by weight; and / or,

[0037] Based on the total weight of the diaphragm slurry being 100%, the weight percentage of the sum of the weight of the boric acid compound and the polymer containing active hydrogen functional groups is 1-50%.

[0038] In a third aspect, in a specific embodiment of the present invention, the present invention further provides an electrode for a lithium ion battery, comprising a current collector and an electrode material coated on the current collector, wherein the electrode material contains a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3, and 4.

[0039] wherein R1 is selected from one of hydroxyl, alkyl or phenyl, X1, X2, X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or an alkyl;

[0040] Preferably, the electrode is a positive electrode or a negative electrode.

[0041] In a fourth aspect, the present invention further provides a method for preparing the above-mentioned lithium-ion battery electrode, comprising the following steps: mixing a boric acid compound and a polymer containing an active hydrogen functional group with an electrode slurry, coating, and drying to obtain the lithium-ion battery electrode;

[0042] Preferably, the drying temperature is 60-120°C;

[0043] More preferably, based on 100% of the total weight of the electrode slurry, the weight percentage of the sum of the weight of the boric acid compound and the polymer containing active hydrogen functional groups is 1-10%.

[0044] In a fifth aspect, in a specific embodiment of the present invention, the present invention further provides a lithium ion battery separator, which comprises a polymer porous membrane and a separator coating material coated on the polymer porous membrane, wherein the separator coating material contains a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3 and 4,

[0045] wherein R1 is selected from one of hydroxyl, alkyl or phenyl, X1, X2, X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or an alkyl;

[0046] Preferably, the polymer porous membrane is a polyolefin microporous membrane or a non-woven fabric.

[0047] In a sixth aspect, the present invention further provides a method for preparing the above-mentioned lithium-ion battery diaphragm, comprising the following steps: mixing a boric acid compound and a polymer containing an active hydrogen functional group with a diaphragm slurry, coating, and drying to obtain the lithium-ion battery diaphragm;

[0048] Preferably, the drying temperature is 60-120°C;

[0049] Based on the total weight of the diaphragm slurry being 100%, the weight percentage of the sum of the weight of the boric acid compound and the polymer containing active hydrogen functional groups is 1-50%.

[0050] In another embodiment of the present invention, the present invention provides the following specific technical solutions:

[0051] In a specific embodiment of the present invention, the present invention provides a gel electrolyte lithium ion battery, comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein at least one of the positive electrode, the negative electrode or the separator comprises a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3 and 4:

[0052] Wherein, R1 is selected from one of hydroxyl, alkyl, aryl or heteroaryl, X1, X2, X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or an alkyl.

[0053] In some embodiments of the present invention, the gel electrolyte lithium ion battery comprises a positive electrode, a negative electrode, a separator, and an electrolyte, wherein at least one of the positive electrode, the negative electrode, or the separator comprises a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3, and 4:

[0054] Wherein R1 is selected from one of hydroxyl, alkyl or phenyl, X1, X2, X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or an alkyl.

[0055] In some embodiments of the present invention, the electrolyte comprises a positive electrode, a negative electrode, a separator and an electrolyte, wherein when X1, X2 and X3 are each independently selected from O, the group containing O is selected from:

[0056] When X1, X2, and X3 are each independently selected from NR2, the group containing NR2 is selected from

[0057] Wherein, when the group containing O is selected from When , O is directly connected to B, and C is directly connected to the polymer chain;

[0058] When the group containing O is selected from When , O is directly connected to B, and S is directly connected to the polymer chain;

[0059] When the group containing NR2 is selected from When N is directly connected to B, C is directly connected to the polymer chain.

[0060] In a specific embodiment of the present invention, the present invention provides a gel electrolyte lithium ion battery, comprising a current collector and an electrode material coated on the current collector, wherein the electrode material contains a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3, 4, 5, 6, 7, and 8:

[0061] Wherein, R1 is selected from one of hydroxyl, alkyl, phenyl, naphthyl or heteroaryl, X1, X2, X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or an alkyl.

[0062] In some embodiments of the present invention, the polymer having a boron cross-linked structure is obtained by reacting a boric acid compound with a polymer containing an active hydrogen functional group;

[0063] Preferably, the boric acid compound includes one or more of boric acid, phenylboric acid, phenyldiboric acid, 1,3,5-benzenetriboric acid, alkylboric acid, naphthaleneboric acid and heteroarylboronic acid; preferably, the polymer containing an active hydrogen functional group includes one or more of a hydroxyl-containing polymer, a carboxyl-containing polymer, a sulfonic acid-containing polymer, a sulfate-containing polymer, a phosphoric acid-containing polymer, an amino-containing polymer and a substituted amino-containing polymer.

[0064] In some embodiments of the present invention, the boric acid compound includes one or more of boric acid, phenylboric acid and alkylboric acid.

[0065] In some embodiments of the present invention, the polymer containing active hydrogen functional groups includes one or more of polyolefins containing active hydrogen functional groups, polyethers containing active hydrogen functional groups, polyesters containing active hydrogen functional groups, polyamides containing active hydrogen functional groups, and polycarbonates containing active hydrogen functional groups.

[0066] In some embodiments of the present invention, at 25-60° C., the swelling degree of the polymer having a boron cross-linked structure in the electrolyte is greater than 50%, preferably 50-10000%; preferably, the swelling loss rate of the polymer having a boron cross-linked structure in the electrolyte is less than 5%.

[0067] In some embodiments of the present invention, the positive electrode includes a current collector and a positive electrode coating material coated on the current collector; preferably, the positive electrode coating material includes a positive electrode active material and the polymer having a boron cross-linked structure;

[0068] And / or, the negative electrode comprises a current collector and a negative electrode coating material coated on the current collector; preferably, the negative electrode coating material comprises a negative electrode active material and the polymer having a boron cross-linked structure;

[0069] And / or, the separator includes a polymer porous membrane and a separator coating material coated on the polymer porous membrane; preferably, the separator coating material includes inorganic particles and a polymer having a boron cross-linked structure.

[0070] In some embodiments of the present invention, the electrolyte comprises an organic solvent and a lithium salt; preferably, the organic solvent is selected from one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and methyl propyl carbonate;

[0071] More preferably, the lithium salt is selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonyl)imide and lithium bis(fluorosulfonyl)imide, preferably lithium hexafluorophosphate.

[0072] In some embodiments of the present invention, the electrolyte further comprises one or more of unsaturated cyclic carbonates, fluorinated cyclic carbonates, cyclic sultones, and cyclic sulfates;

[0073] Preferably, the unsaturated cyclic carbonate is selected from vinylene carbonate and / or vinyl ethylene carbonate,

[0074] and / or the fluorinated cyclic carbonate is selected from at least one of fluoroethylene carbonate, trifluoromethylethylene carbonate or bisfluoroethylene carbonate,

[0075] and / or the cyclic sultone is at least one selected from 1,3-propane sultone, 1,4-butane sultone and propenyl-1,3-sultone,

[0076] And / or the cyclic sulfate is selected from at least one of vinyl sulfate, propylene sulfate, and 4-methylvinyl sulfate.

[0077] On the other hand, the present invention also provides a method for preparing the above-mentioned gel electrolyte lithium ion battery, comprising the following steps: forming a battery core with a positive electrode, a negative electrode, and a separator, placing the battery core in a battery housing, injecting an electrolyte to obtain a semi-finished lithium ion battery, forming and exhausting the semi-finished lithium ion battery, and then sealing the liquid injection port of the battery housing to obtain a gel electrolyte lithium ion battery;

[0078] Wherein, at least one of the positive electrode, negative electrode or separator is prepared according to the following method:

[0079] (1) The positive electrode is prepared by mixing a boric acid compound and a polymer containing an active hydrogen functional group with a positive electrode slurry, coating the slurry on a current collector, and then drying to obtain the positive electrode;

[0080] (2) The negative electrode is prepared by mixing a boric acid compound and a polymer containing an active hydrogen functional group with a negative electrode slurry, coating the slurry on a current collector, and then drying to obtain the negative electrode;

[0081] (3) The diaphragm is prepared by the following steps: mixing a boric acid compound and a polymer containing an active hydrogen functional group with a diaphragm slurry, then coating the slurry on a polymer porous membrane, and then drying to obtain the diaphragm;

[0082] Preferably, the drying temperature is 60-120°C;

[0083] More preferably, based on 100% of the total weight of the positive electrode slurry, the weight percentage of the sum of the weight of the boric acid compound and the polymer containing active hydrogen functional groups is 1-10%; and / or,

[0084] Based on the total weight of the negative electrode slurry being 100%, the sum of the weight of the boric acid compound and the polymer containing active hydrogen functional groups is 1-10% by weight; and / or,

[0085] Based on the total weight of the diaphragm slurry being 100%, the weight percentage of the sum of the weight of the boric acid compound and the polymer containing active hydrogen functional groups is 1-50%.

[0086] On the other hand, the present invention also provides an electrode for a lithium ion battery, comprising a current collector and an electrode material coated on the current collector, wherein the electrode material contains a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3, and 4:

[0087] Wherein, R1 is selected from one of hydroxyl, alkyl, aryl or heteroaryl, X1, X2, X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or an alkyl.

[0088] In some embodiments of the present invention, the present invention further provides an electrode for a lithium ion battery, comprising a current collector and an electrode material coated on the current collector, wherein the electrode material contains a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3, and 4.

[0089] wherein R1 is selected from one of hydroxyl, alkyl or phenyl, X1, X2, X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or an alkyl;

[0090] Preferably, the electrode is a positive electrode or a negative electrode.

[0091] In some embodiments of the present invention, when X1, X2, and X3 are each independently selected from O, the group containing O is selected from:

[0092] When X1, X2, and X3 are each independently selected from NR2, the group containing NR2 is selected from

[0093] Wherein, when the group containing O is selected from When , O is directly connected to B, and C is directly connected to the polymer chain;

[0094] When the group containing O is selected from When , O is directly connected to B, and S is directly connected to the polymer chain;

[0095] When the group containing NR2 is selected from When N is directly connected to B, C is directly connected to the polymer chain.

[0096] In some embodiments of the present invention, the present invention further provides an electrode for a lithium ion battery, comprising a current collector and an electrode material coated on the current collector, wherein the electrode material contains a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3, 4, 5, 6, 7, and 8.

[0097] Wherein, R1 is selected from one of hydroxyl, alkyl, phenyl, naphthyl or heteroaryl, X1, X2, X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or an alkyl.

[0098] On the other hand, the present invention also provides a method for preparing the above-mentioned lithium-ion battery electrode, comprising the following steps: mixing a boric acid compound and a polymer containing an active hydrogen functional group with an electrode slurry, coating, and drying to obtain the lithium-ion battery electrode;

[0099] Preferably, the drying temperature is 60-120°C;

[0100] More preferably, based on 100% of the total weight of the electrode slurry, the weight percentage of the sum of the weight of the boric acid compound and the polymer containing active hydrogen functional groups is 1-10%.

[0101] On the other hand, the present invention also provides a lithium ion battery separator, which includes a polymer porous membrane and a separator coating material coated on the polymer porous membrane, wherein the separator coating material contains a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3 and 4:

[0102] Wherein R1 is selected from one of hydroxyl, alkyl, aryl or heteroaryl groups, X1, X2, X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or an alkyl group.

[0103] In some embodiments of the present invention, the above-mentioned lithium ion battery separator comprises a polymer porous membrane and a separator coating material coated on the polymer porous membrane, wherein the separator coating material contains a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3 and 4.

[0104] wherein R1 is selected from one of hydroxyl, alkyl or phenyl, X1, X2, X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or an alkyl;

[0105] Preferably, the polymer porous membrane is a polyolefin microporous membrane or a non-woven fabric.

[0106] In some embodiments of the present invention, in the above-mentioned lithium ion battery separator, when X1, X2, and X3 are each independently selected from O, the group containing O is selected from:

[0107] When X1, X2, and X3 are each independently selected from NR2, the group containing NR2 is selected from

[0108] Wherein, when the group containing O is selected from When , O is directly connected to B, and C is directly connected to the polymer chain;

[0109] When the group containing O is selected from When , O is directly connected to B, and S is directly connected to the polymer chain;

[0110] When the group containing NR2 is selected from When N is directly connected to B, C is directly connected to the polymer chain.

[0111] In some embodiments of the present invention, the present invention further provides a separator for a lithium ion battery, comprising a current collector and an electrode material coated on the current collector, wherein the electrode material contains a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3, 4, 5, 6, 7, and 8.

[0112] Wherein, R1 is selected from one of hydroxyl, alkyl, phenyl, naphthyl or heteroaryl, X1, X2, X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or an alkyl.

[0113] On the other hand, the present invention also provides a method for preparing the above-mentioned lithium-ion battery diaphragm, comprising the following steps: mixing a boric acid compound and a polymer containing an active hydrogen functional group with a diaphragm slurry, coating, and drying to obtain the lithium-ion battery diaphragm;

[0114] Preferably, the drying temperature is 60-120°C;

[0115] Based on the total weight of the diaphragm slurry being 100%, the weight percentage of the sum of the weight of the boric acid compound and the polymer containing active hydrogen functional groups is 1-50%.

[0116] Compared with the prior art, the present invention has the following beneficial effects:

[0117] (1) At least one of the positive electrode, negative electrode or separator of the lithium-ion battery of the present invention contains a polymer having a boron cross-linked structure. The polymer having a boron cross-linked structure can absorb the electrolyte and swell to form a gel electrolyte after contact with the electrolyte. The conventional production process of lithium-ion batteries can be used, which reduces the complexity of the preparation process and the cost of production equipment. It also avoids the problem of adding the gel polymer precursor directly to the electrolyte in the prior art, which causes the electrolyte to be unstable and difficult to wet the electrodes. The invention can meet the needs of high-energy-density batteries.

[0118] (2) The polymer with a boron cross-linked structure can ensure that the polymer will not dissolve in the electrolyte. By selecting a suitable polymer chain, the polymer can absorb the electrolyte well and swell to form a gel electrolyte, thereby preventing electrolyte leakage, reducing the contact between the electrolyte and the surface of the active material, and reducing the decomposition and consumption of the electrolyte;

[0119] (3) The polymer with boron cross-linking structure has Lewis acid properties and can form complexes with anions in the electrolyte, thereby reducing the migration of anions under the action of the electric field and increasing the number of lithium ion migration, which is beneficial to improving the rate charge and discharge performance of gel electrolyte lithium-ion batteries. DETAILED DESCRIPTION

[0120] To make the purpose, technical solutions, and technical effects of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. The embodiments described below are part of the embodiments of the present invention, not all of them. In combination with the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0121] In the description of groups (atomic groups) in this specification, unless substituted or unsubstituted is specified, both groups without substitution and groups with substitution are included. For example, "alkyl" includes not only alkyl groups without substitution (unsubstituted alkyl groups) but also alkyl groups with substitution (substituted alkyl groups).

[0122] In order to better understand the above technical solution, the present invention is further described in detail below.

[0123] In a first aspect, in a specific embodiment of the present invention, the present invention provides a gel electrolyte lithium ion battery, comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein at least one of the positive electrode, the negative electrode or the separator comprises a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3, 4, 5, 6, 7 and 8,

[0124] Wherein, R1 is selected from one of hydroxyl, alkyl, phenyl, naphthyl or heteroaryl, and X1, X2, and X3 are each independently selected from one of the following groups:

[0125] Wherein, R2 is a hydrogen atom or an alkyl group;

[0126] Wherein, when X1, X2, X3 are each independently selected from When , O is directly connected to B, and C is directly connected to the polymer chain;

[0127] When X1, X2, and X3 are independently selected from When , O is directly connected to B, and S is directly connected to the polymer chain;

[0128] When X1, X2, and X3 are independently selected from When N is directly connected to B, C is directly connected to the polymer chain.

[0129] In some embodiments of the present invention, the heteroaryl group is selected from pyridyl, thienyl, pyrrolyl, thiazolyl, oxazolyl, pyrazinyl, pyrimidinyl, furanyl or indolyl.

[0130] In some embodiments of the present invention, the alkyl, phenyl, naphthyl or heteroaryl group may be substituted with one or more substituents, each of which is independently selected from a C1-6 alkyl group, a C1-6 haloalkyl group, a halogen, a C1-6 alkoxy group, a carbonyl group, a benzyloxy group, a cyano group or an ester group.

[0131] In some embodiments of the present invention, the substituents are each independently selected from C1-4 alkyl, C1-4 haloalkyl, halogen, C1-4 alkoxy, carbonyl, benzyloxy, cyano or ester.

[0132] In some embodiments of the present invention, the substituents are each independently selected from methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, fluoromethyl, difluoromethyl, trifluoromethyl, chloromethyl, bromomethyl, bromoethyl, fluoroethyl, chloroethyl, 1,1-difluoroethyl, 1,1-dichloroethyl, fluoropropyl, chloropropyl, trifluoromethyl, 1,1-difluoropropyl, 1,1,1-trifluoropropyl, fluorobutyl, chlorobutyl, 1,1-difluorobutyl alkyl, methyl phthalate ...

[0133] In some specific embodiments of the present invention, R1 is selected from hydroxyl, alkyl, phenyl, naphthyl, pyridinyl, thienyl, pyrrolyl, thiazolyl, oxazolyl, pyrazinyl, pyrimidinyl, furanyl or indolyl; the alkyl, phenyl, naphthyl, pyridinyl, thienyl, pyrrolyl, thiazolyl, oxazolyl, pyrazinyl, pyrimidinyl, furanyl or indolyl may be substituted with one or more substituents; the substituents are each independently selected from C1-6 alkyl, C1-6 haloalkyl, halogen, C1-6 alkoxy, carbonyl, benzyloxy, cyano or ester.

[0134] In some embodiments of the present invention, R1 is selected from hydroxyl, alkyl, phenyl, naphthyl, pyridinyl, thienyl, pyrrolyl, thiazolyl, oxazolyl, pyrazinyl, pyrimidinyl, furanyl or indolyl; the alkyl, phenyl, naphthyl, pyridinyl, thienyl, pyrrolyl, thiazolyl, oxazolyl, pyrazinyl, pyrimidinyl, furanyl or indolyl may be substituted with one or more substituents; the substituents are each independently selected from methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, fluoromethyl, difluoromethyl, trifluoromethyl, chloromethyl, bromomethyl, bromoethyl, fluoroethyl, chloroethyl, 1,1-difluoroethyl , 1,1-dichloroethyl, fluoropropyl, chloropropyl, 1,1-difluoropropyl, 1,1,1-trifluoropropyl, fluorobutyl, chlorobutyl, 1,1-difluorobutyl, fluoro, chloro, bromo, iodo, methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, isopropoxy, tert-butoxy, ketone, formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, benzyloxy, cyano, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, tert-butyl ester, phenyl acetate or dibutyl phthalate.

[0135] In some specific embodiments of the present invention, R1 is selected from hydroxyl, C1-6 alkyl, phenyl, halogen-substituted phenyl, alkyl-substituted phenyl, haloalkyl-substituted phenyl, cyano-substituted phenyl, carbonyl-substituted phenyl, alkoxy-substituted phenyl, naphthyl, pyridyl, thienyl, halogen-substituted thienyl, carbonyl-substituted thienyl, pyrrolyl, thiazolyl, oxazolyl, pyrazinyl, pyrimidinyl, halogen-substituted pyrimidinyl, furanyl, indolyl or ester-substituted indolyl.

[0136] In some specific embodiments of the present invention, R1 is selected from hydroxyl, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, phenyl, fluoro-substituted phenyl, chloro-substituted phenyl, ethylphenyl, n-propylphenyl, isopropylphenyl, butylphenyl, isobutylphenyl, tert-butylphenyl, chlorobenzyl, bromobenzyl, fluoromethyl-substituted phenyl, difluoromethyl-substituted phenyl, trifluoromethyl-substituted phenyl, chloromethyl-substituted phenyl, bromomethyl-substituted phenyl, bromoethyl-substituted phenyl, cyano-substituted phenyl, aldehyde-substituted phenyl, methoxy-substituted phenyl, ethoxy-substituted phenyl, propoxy-substituted phenyl, butoxy-substituted phenyl, naphthyl, pyridyl, thienyl, fluoro-substituted thienyl, chloro-substituted thienyl, keto-substituted thienyl, pyrrolyl, thiazolyl, oxazolyl, pyrazinyl, pyrimidinyl, fluoro-substituted pyrimidinyl, bromo-substituted pyrimidinyl, furanyl, indolyl or tert-butyl ester-substituted indolyl.

[0137] In some embodiments of the present invention, R1 is selected from hydroxy, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, phenyl,

[0138] It should be noted that the dotted line in the above R1 group selection represents a direct connection with B.

[0139] In some embodiments of the present invention, X1, X2, and X3 are each independently selected from one of the following groups:

[0140] Wherein R2 is a hydrogen atom or a C1-6 alkyl group.

[0141] In some embodiments of the present invention, X1, X2, and X3 are each independently selected from one of the following groups:

[0142] wherein R2 is a hydrogen atom, a methyl group, an ethyl group, a propyl group, a n-butyl group, an isobutyl group, a tert-butyl group, a n-pentyl group, an isopentyl group, a neopentyl group, a n-hexyl group, an isohexyl group, a tert-hexyl group or a tert-hexyl group.

[0143] It should be noted that the wavy lines in Formulas 1 to 6 described herein represent polymer chains.

[0144] In some embodiments of the present invention, the polymer chain is selected from one or more of polyolefins, polyethers, polyesters, polyamides, and polycarbonates.

[0145] In a specific embodiment of the present invention, the present invention provides a gel electrolyte lithium ion battery comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein at least one of the positive electrode, the negative electrode or the separator comprises a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3 and 4:

[0146] Wherein R1 is selected from one of hydroxyl, alkyl and phenyl, X1, X2 and X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or an alkyl.

[0147] The alkyl or phenyl group may be substituted with one or more substituents, and the substituents are selected in the same manner as the substituents for the alkyl, phenyl, naphthyl or heteroaryl groups described above.

[0148] In some embodiments of the present invention, R1 is selected from hydroxyl, C1-6 alkyl, phenyl, halogen-substituted phenyl, alkyl-substituted phenyl, haloalkyl-substituted phenyl, cyano-substituted phenyl, carbonyl-substituted phenyl or alkoxy-substituted phenyl.

[0149] In some specific embodiments of the present invention, R1 is selected from hydroxyl, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, phenyl, fluoro-substituted phenyl, chloro-substituted phenyl, ethylphenyl, n-propylphenyl, isopropylphenyl, butylphenyl, isobutylphenyl, tert-butylphenyl, chlorobenzyl, bromobenzyl, fluoromethyl-substituted phenyl, difluoromethyl-substituted phenyl, trifluoromethyl-substituted phenyl, chloromethyl-substituted phenyl, bromomethyl-substituted phenyl, bromoethyl-substituted phenyl, cyano-substituted phenyl, aldehyde-substituted phenyl, methoxy-substituted phenyl, ethoxy-substituted phenyl, propoxy-substituted phenyl or butoxy-substituted phenyl.

[0150] In some specific embodiments of the present invention, X1, X2, and X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or a C1-6 alkyl group.

[0151] In some specific embodiments of the present invention, X1, X2, and X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom, a methyl group, an ethyl group, a propyl group, a n-butyl group, an isobutyl group, a tert-butyl group, a n-pentyl group, an isopentyl group, a neopentyl group, a n-hexyl group, an isohexyl group, a tert-hexyl group, or a tert-hexyl group.

[0152] In some embodiments of the present invention, the polymer having a boron cross-linked structure is obtained by reacting a boric acid compound with a polymer containing an active hydrogen functional group, wherein the boric acid compound includes one or more of boric acid, phenylboric acid, phenyldiboric acid, 1,3,5-benzenetriboric acid, alkylboric acid, naphthaleneboric acid and heteroarylboronic acid.

[0153] In some embodiments of the present invention, the polymer having a boron cross-linked structure is obtained by reacting a boric acid compound with a polymer containing an active hydrogen functional group; wherein the boric acid compound includes one or more of boric acid, phenylboric acid and alkylboric acid.

[0154] The heteroaryl group in the heteroarylboronic acid is selected from pyridyl, pyrazinyl, pyrimidinyl, furyl, pyrrolyl, thienyl, thiazolyl or oxazolyl.

[0155] The phenyl, alkyl, naphthyl, and heteroaryl groups in the phenylboronic acid, alkylboronic acid, naphthaleneboronic acid, and heteroarylboronic acid may be substituted with one or more substituents. The substituents are selected in the same manner as the substituents for the alkyl, phenyl, naphthyl, and heteroaryl groups described above.

[0156] Preferably, phenylboronic acid includes but is not limited to 5-chloro-2-methoxyphenylboronic acid, 4-cyanophenylboronic acid, 5-formyl-2-methoxyphenylboronic acid, 4-isopropylphenylboronic acid, 2-chloro-4-methylphenylboronic acid, 3-chloro-5-trifluoromethylphenylboronic acid or 4-benzyloxy-3-methoxyphenylboronic acid; preferably, phenyldiboronic acid includes but is not limited to 1,3-phenyldiboronic acid and / or 1,4-phenyldiboronic acid; preferably, alkylboronic acid includes but is not limited to methylboronic acid, ethylboronic acid, propylboronic acid, isopropylboronic acid, n-butylboronic acid, isobutylboronic acid, tert-butylboronic acid or fluoromethylboronic acid; preferably, naphthaleneboronic acid includes but is not limited to 1-naphthaleneboronic acid, 2-naphthaleneboronic acid, 1,5-dinaphthylboronic acid or 2,6-dinaphthylboronic acid; preferably, heteroarylboronic acid includes but is not limited to 3-pyridineboronic acid, 2-fluoro-3-pyridineboronic acid, 2-bromopyridine-4-boronic acid, 2-thiopheneboronic acid, (4-fluorothiophen-2-yl)boronic acid, 5-acetyl-2-thiopheneboronic acid, 2-chlorothiophene-3-boronic acid, 2-furanboronic acid, 2-pyrroleboric acid, 3-quinolineboronic acid, 2-imidazoleboronic acid or N-(BOC)-7-fluoroindole-2-boronic acid.

[0157] Preferably, the polymer containing active hydrogen functional groups includes one or more of hydroxyl-containing polymers, carboxyl-containing polymers, sulfonic acid-containing polymers, sulfate-containing polymers, phosphate-containing polymers, amino-containing polymers and substituted amino-containing polymers.

[0158] Specifically, the present invention obtains an electrode or a diaphragm containing a polymer having a boron cross-linked structure by mixing a boric acid compound and a polymer containing an active hydrogen functional group with an electrode slurry or a diaphragm slurry, coating, and drying. After coating, the boric acid compound and the polymer containing an active hydrogen functional group undergo a dehydration reaction during a high-temperature baking process. An example of the reaction is shown below:

[0159] wherein R2 is a hydrogen atom or an alkyl group.

[0160] It should be noted that the wavy lines in the molecular formulas described herein represent polymer chains.

[0161] In some embodiments of the present invention, the polymer chain is selected from one or more of polyolefins, polyethers, polyesters, polyamides, and polycarbonates.

[0162] In some embodiments of the present invention, the polymer containing an active hydrogen functional group is selected from one or more of polyolefins containing an active hydrogen functional group, polyethers containing an active hydrogen functional group, polyesters containing an active hydrogen functional group, polyamides containing an active hydrogen functional group, and polycarbonates containing an active hydrogen functional group. The polymer containing an active hydrogen functional group includes one or more of polyolefins, polyethers, polyesters, polyamides, and polycarbonates. Active hydrogen functional group-containing polyolefins, active hydrogen functional group-containing polyethers, active hydrogen functional group-containing polyesters, active hydrogen functional group-containing polyamides, and active hydrogen functional group-containing polycarbonates are classified according to the different main chain structures. The structural formula of the active hydrogen functional group-containing polyolefin is, for example, shown in Formula 24, the structural formula of the active hydrogen functional group-containing polyether is, for example, shown in Formula 25 or Formula 26, the structural formula of the active hydrogen functional group-containing polyester is, for example, shown in Formula 27, Formula 28, Formula 29, or Formula 30, the structural formula of the active hydrogen functional group-containing polycarbonate is, for example, shown in Formula 31 or Formula 32, and the structural formula of the active hydrogen functional group-containing polyamide is, for example, shown in Formula 33 or Formula 34.

[0163] Wherein R3, R4, and R5 are each independently selected from a hydrocarbon group or a substituted hydrocarbon group containing one or more elements of oxygen, nitrogen, sulfur, phosphorus or halogen, R6 is selected from a hydrocarbon group or a substituted hydrocarbon group containing one or more of oxygen, nitrogen, sulfur, phosphorus and halogen, X is selected from one of -OH and -NHR2 (wherein R2 is a hydrogen atom or an alkyl group), m and l are both integers greater than or equal to 1, and n is an integer greater than or equal to 2.

[0164] Wherein R is the portion of a small molecule polyol or an oligomer polyol without a hydroxyl group, R7 is a hydrocarbylene group or a substituted hydrocarbylene group containing one or more elements of oxygen, nitrogen, sulfur, phosphorus, and halogens, R8 is a secondary hydrocarbylene group or a substituted secondary hydrocarbylene group containing one or more elements of oxygen, nitrogen, sulfur, phosphorus, and halogens, X is selected from one of -OH and -NHR2 (wherein R2 is a hydrogen atom or an alkyl group), m and l are integers greater than or equal to 1, and n is an integer greater than or equal to 2.

[0165] Where R is the part after removing the hydroxyl group of small molecule polyol or oligomer polyol, R9, R 11 ,R 12 is an alkylene group or a substituted alkylene group containing one or more elements of oxygen, nitrogen, sulfur, phosphorus, or halogen, R 10 ,R 13 ,R 14is a hydrocarbyl group or a substituted hydrocarbyl group containing one or more of oxygen, nitrogen, sulfur, phosphorus, or halogen. X is selected from one of -OH and -NHR2 (wherein R2 is a hydrogen atom or an alkyl group), Y1 and Y2 are selected from one of -H, -OH, and -NHR2, and at least one of them is not -H (wherein R2 is a hydrogen atom or an alkyl group), m and l are integers greater than or equal to 1, and n is an integer greater than or equal to 2.

[0166] Where R is the small molecule polyol or oligomer polyol with the hydroxyl group removed. 15 is an alkylene group or a substituted alkylene group containing one or more elements of oxygen, nitrogen, sulfur, phosphorus, or halogen, R 16 is a hydrocarbyl group or a substituted hydrocarbyl group containing one or more of oxygen, nitrogen, sulfur, phosphorus, or halogen. X is selected from one of -OH and -NHR2 (wherein R2 is a hydrogen atom or an alkyl group), m and l are integers greater than or equal to 1, and n is an integer greater than or equal to 2.

[0167] where R 17 ,R 18 ,R 19 is a hydrocarbylene group or a substituted hydrocarbylene group containing one or more elements of oxygen, nitrogen, sulfur, phosphorus, or halogen, and n is an integer greater than or equal to 2.

[0168] The synthetic route for polyolefins containing active hydrogen functional groups is to obtain them by free radical polymerization of double-bond-containing monomers in the presence of an initiator. Common double-bond-containing monomers include acrylonitrile, acrylates, methacrylates, cyanoacrylates, N-vinyl pyrrolidone, vinyl pyridine, N,N-dimethylacrylamide, etc. In addition, in order to introduce active hydrogen-containing functional groups into the polymer chain, it is necessary to introduce monomers containing active hydrogen and double bonds to copolymerize with the above common double-bond-containing monomers. Monomers containing active hydrogen and double bonds include acrylic acid, acrylamide, hydroxyethyl acrylate, hydroxyethyl methacrylate, ethylene glycol monovinyl ether, vinyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, 2-hydroxyethyl methacrylate phosphate, etc.

[0169] The synthetic route of polyethers containing active hydrogen functional groups is to obtain polyether polyols by ring-opening polymerization of epoxy monomers initiated by polyols. Representative polyols include ethylene glycol, propylene glycol, trimethylolpropane, pentaerythritol, etc., and representative epoxy monomers include ethylene oxide, propylene oxide, 1,3-dioxolane, glycidol, epichlorohydrin, etc.

[0170] The synthesis routes of polyesters containing active hydrogen functional groups are divided into two categories. The main chain of one category is obtained by the ring-opening polymerization of lactone monomers initiated by polyols, polycarboxylic acids or hydroxycarboxylic acid-containing initiators. The synthesis routes are respectively to use polyols, polycarboxylic acids or hydroxycarboxylic acid-containing compounds as initiators to initiate the ring-opening polymerization of lactone monomers to obtain polyester polyols or polyester polyacids or polyesters containing multiple hydroxyl groups and carboxylic acids at the same time. Representative polyols include ethylene glycol, glycerol, trimethylolpropane, pentaerythritol, inositol, etc. Representative polycarboxylic acids include succinic acid, triacrylic acid, pyromellitic acid, butanetetracarboxylic acid, pyromellitic acid, etc. Representative initiators containing hydroxycarboxylic acids include glycolic acid, malic acid, citric acid, tartaric acid, etc. Representative lactone monomers include glycolide, lactide, δ-valerolactone, ε-caprolactone, etc.; the main chain of another type is obtained by the condensation reaction of diacid monomers and diol monomers, and its synthesis route is to obtain polyester polyols by the condensation reaction of diacid monomers and diol monomers. Representative diacids include succinic acid, adipic acid, terephthalic acid, etc., and representative diols include ethylene glycol, 1,3-propylene glycol, 1,6-hexanediol, etc.

[0171] The synthetic route of polycarbonates containing active hydrogen functional groups is to obtain polycarbonate polyols by ring-opening polymerization of cyclic carbonate monomers initiated by polyols. Representative polyols include ethylene glycol, propylene glycol, trimethylolpropane, pentaerythritol, etc., and representative cyclic carbonate monomers include ethylene carbonate, propylene carbonate, etc.

[0172] The synthesis routes of polyamides containing active hydrogen functional groups are divided into two categories. The main chain of one category is obtained by ring-opening polymerization of caprolactam monomers initiated by alkali metals or water to obtain polyamides with amino groups and carboxylate groups at both ends, and representative alkali metal initiators include sodium hydroxide and sodium methoxide. The main chain of the other category is obtained by condensation polymerization of dibasic acid monomers and diamine monomers. The synthesis route is to obtain polyamide by condensation polymerization of dibasic acid monomers and diamine monomers. Representative dibasic acids include succinic acid, adipic acid, terephthalic acid, etc., and representative diamines include ethylenediamine, hexamethylenediamine, polyetheramine, p-phenylenediamine, etc.

[0173] It should be noted that the electrode slurry in the present invention refers to a fluid formed by mixing and evenly dispersing materials such as electrode active materials, conductive agents, and binders in a solvent. The diaphragm slurry refers to a fluid formed by mixing and dispersing materials such as inorganic particles and binders in a solvent.

[0174] In some embodiments of the present invention, the polymer containing active hydrogen functional groups includes but is not limited to one or more of the following polymers:

[0175] Oligomer 11 (polyethylene glycol PEG400), oligomer 12 (polyethylene glycol PEG1000), oligomer 13 (polypropylene glycol PPG2000) and oligomer 14 (polypropylene glycol PPG4000).

[0176] In some embodiments of the present invention, the polymer having a boron cross-linked structure in the positive electrode is obtained by reacting one or more of oligomer 1, oligomer 3, oligomer 4, oligomer 5, oligomer 6, oligomer 7 or oligomer 14 with a boric acid compound; preferably, based on the total weight of the positive electrode slurry as 100%, the weight percentage of the sum of the weight of the polymer containing active hydrogen functional groups and the boric acid compound is 1-10%, preferably 2-7%.

[0177] In some embodiments of the present invention, based on the total weight of the positive electrode slurry being 100%, the weight percentage of the sum of the weight of the polymer containing active hydrogen functional groups and the boric acid compound can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or within a numerical range consisting of any two of the above specific values ​​as endpoints. It should be understood that in specific embodiments, any of the above ranges can be combined with any other ranges.

[0178] In some embodiments of the present invention, the polymer having a boron cross-linked structure in the negative electrode is obtained by reacting one or more of oligomer 8, oligomer 9, oligomer 11, oligomer 12, or oligomer 13 with a boric acid compound. Preferably, based on 100% of the total weight of the negative electrode slurry, the weight percentage of the sum of the weight of the polymer containing active hydrogen functional groups and the boric acid compound is 1-10%, preferably 2-9%.

[0179] In some embodiments of the present invention, based on the total weight of the negative electrode slurry being 100%, the weight percentage of the sum of the weight of the polymer containing active hydrogen functional groups and the boric acid compound can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, or within a numerical range consisting of any two of the above specific values ​​as endpoints. It should be understood that in specific embodiments, any of the above ranges can be combined with any other ranges.

[0180] In some embodiments of the present invention, the polymer having a boron cross-linked structure in the separator is obtained by reacting one or more of oligomer 8, oligomer 9, oligomer 10, or oligomer 11 with a boric acid compound. Preferably, based on 100% of the total weight of the separator slurry, the weight percentage of the sum of the weight of the polymer containing active hydrogen functional groups and the boric acid compound is 1-50%, preferably 5-15%, and more preferably 5-12%.

[0181] In some embodiments of the present invention, based on the total weight of the positive electrode slurry as 100%, the weight percentage of the sum of the weight of the polymer containing active hydrogen functional groups and the boric acid compound can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, or within a numerical range consisting of any two of the above specific values ​​as endpoints. It should be understood that in specific embodiments, any of the above ranges can be combined with any other ranges.

[0182] In some embodiments of the present invention, the molar ratio of the polymer containing active hydrogen functional groups to the boric acid compound is 0.1-50:1, preferably 0.1-20:1, and more preferably 0.1-2:1.

[0183] In some embodiments of the present invention, at 25-60°C, the boron-crosslinked polymer has a swelling degree greater than 50% in the electrolyte, preferably a swelling loss rate of less than 5%, more preferably a swelling degree of 50-10,000%, further preferably a swelling degree of 100% to 5,000%, and even more preferably a swelling degree of 100% to 1,000%. When the swelling degree is less than 50%, the conductivity of the gel electrolyte formed by the boron-crosslinked polymer is very low, the internal resistance of the battery increases, and thus affects the charge and discharge rate performance and low-temperature cycle performance of the battery; when the swelling degree is greater than 10,000%, the mechanical properties of the boron-crosslinked polymer deteriorate, and the polymer may even dissolve in the electrolyte, losing its function as a gel electrolyte.

[0184] It should be noted that the swelling degree described in the present invention refers to the ratio of the mass difference before and after the polymer with a boron cross-linking structure is immersed in the electrolyte to the mass of the polymer before immersion. The specific test method is: the polymer with a boron cross-linking structure is made into a circular film sheet with a thickness of 30μm and a size of 16mm*16mm, the mass of the film is weighed, the film is immersed in 10g of electrolyte, and stored at 60°C after sealing. The film is taken out every 8 hours, the electrolyte on the surface is wiped off, the thickness is measured and weighed, and then it is put back into the electrolyte and sealed and continued to be stored at 60°C until the thickness and mass of the film remain unchanged after three consecutive tests. It is considered that the polymer film with a boron cross-linking structure has reached a swelling equilibrium state. The swelling degree is calculated according to the following formula:

[0185] In the above formula, m0 represents the mass of the polymer membrane with a boron cross-linked structure before immersion in the electrolyte, and m1 represents the mass of the polymer membrane with a boron cross-linked structure when the membrane reaches swelling equilibrium after immersion in the electrolyte.

[0186] The swelling loss rate described in the present invention refers to the ratio of the mass loss caused by the partial dissolution of the polymer into the electrolyte when the polymer with a boron cross-linked structure swells in the electrolyte to the mass of the polymer before swelling. The specific test method is: the polymer with a boron cross-linked structure is made into a circular film sheet with a thickness of 30 μm and a size of 16 mm * 16 mm, the mass of the film is weighed, the film is immersed in 10 g of electrolyte, sealed and stored at 60 ° C, the film is taken out every 8 hours, the electrolyte on the surface is wiped off, the thickness is measured and weighed, and then the film is put back into the electrolyte and sealed and continued to be stored at 60 ° C until the thickness and mass of the film remain unchanged after three consecutive tests, the excess electrolyte and lithium salt on the film are rinsed off with solvent dimethyl carbonate (DMC), and the film is completely dried in an oven, the mass of the remaining film after drying is weighed, and the swelling loss rate is calculated according to the following formula:

[0187] In the above formula, m0 represents the mass of the polymer membrane with a boron cross-linked structure before immersion in the electrolyte, and the unit is g; m2 represents the mass of the polymer membrane with a boron cross-linked structure remaining after immersion in the electrolyte and then washing and drying, and the unit is g.

[0188] In some embodiments of the present invention, the electrolyte comprises a non-aqueous organic solvent and a lithium salt; preferably, the non-aqueous organic solvent is selected from one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and methyl propyl carbonate; further preferably, the lithium salt is selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonyl)imide and lithium bis(fluorosulfonyl)imide.

[0189] In some embodiments of the present invention, the electrolyte further comprises one or more of unsaturated cyclic carbonates, fluorinated cyclic carbonates, cyclic sultones, and cyclic sulfates.

[0190] In some embodiments of the present invention, the positive electrode includes a current collector and a positive electrode coating material coated on the current collector. The current collector can be various current collectors familiar to those skilled in the art, such as aluminum foil, carbon-coated aluminum foil, and aluminum-plated polymer film; the positive electrode coating material includes the above-mentioned polymer having a boron cross-linked structure and a positive electrode active substance.

[0191] It is understood that the above-mentioned positive electrode coating material also includes a positive electrode conductor and a binder; the above-mentioned positive electrode active material is not limited to lithium nickel cobalt manganese oxide (LiNi x Co y Mn 1-x-yO2, where 0 < x < 1.0, 0 < y < 1.0), lithium cobaltate (LiCoO2), lithium nickelate (LiNiO2), lithium manganate (LiMn2O4), or one or more of them; the positive electrode conductive agent includes, but is not limited to, one or more of carbon black, carbon nanotubes (CNT), flake graphite, Ketjen black, and VGCF; the binder includes, but is not limited to, one or more of polyvinylidene fluoride (PVDF), copolymers of vinylidene fluoride (VF2), and polyimide.

[0192] In some embodiments of the present invention, the negative electrode includes a current collector and a negative electrode coating material coated on the current collector. The current collector can be various current collectors well-known to those skilled in the art, such as copper foil, carbon-coated copper foil, and copper-plated polymer film; the negative electrode coating material includes the above-mentioned polymer having a boron cross-linked structure and a negative electrode active material.

[0193] It can be understood that the above-mentioned negative electrode coating material further includes a negative electrode conductive agent and a binder; the above-mentioned negative electrode active material includes, but is not limited to, artificial graphite (C), silicon carbide, silicon oxide, or mesophase carbon microspheres; the conductive agent includes, but is not limited to, one or more of carbon black, carbon nanotubes (CNT), flake graphite, Ketjen black, and VGCF; the binder includes, but is not limited to, one or more of styrene-butadiene rubber latex (SBR), sodium carboxymethyl cellulose (CMC), and polyacrylic acid polymers (PAA).

[0194] In some embodiments of the present invention, the separator includes a polymer porous membrane and a separator coating material coated on the polymer porous membrane; the above-mentioned separator coating material includes the above-mentioned polymer having a boron cross-linked structure and inorganic particles. It can be understood that the above-mentioned separator coating material further includes a binder, and the binder includes, but is not limited to, one or more of polyvinylidene fluoride (PVDF), styrene-butadiene rubber latex (SBR), and sodium carboxymethyl cellulose (CMC); the inorganic particles include, but are not limited to, at least one of alumina, boehmite, calcium carbonate, hydrotalcite, montmorillonite, spinel, titanium dioxide, silicon dioxide, zirconia, and silicon carbide.

[0195] Second, the present invention also provides a method for preparing the above gel electrolyte lithium-ion battery, including the following steps: forming an electrode core with the positive electrode, negative electrode, and separator and placing it in a battery casing, then injecting an electrolyte to obtain a semi-finished lithium-ion battery, and subjecting the semi-finished lithium-ion battery to formation and degassing, and then sealing the liquid injection port of the battery casing to obtain a gel electrolyte lithium-ion battery;

[0196] Wherein, at least one of the positive electrode, negative electrode, or separator is prepared by the following method:

[0197] (1) The positive electrode is prepared by mixing a boric acid compound and a polymer containing an active hydrogen functional group with a positive electrode slurry, coating the slurry on a current collector, and then drying to obtain the positive electrode; preferably, the drying temperature is 60-120°C;

[0198] (2) The negative electrode is prepared by mixing a boric acid compound and a polymer containing an active hydrogen functional group with a negative electrode slurry, coating the slurry on a current collector, and then drying to obtain the negative electrode; preferably, the drying temperature is 60-120°C;

[0199] (3) The diaphragm is prepared by the following steps: mixing a boric acid compound and a polymer containing an active hydrogen functional group with a diaphragm slurry, then coating the slurry on a polymer porous membrane, and then drying to obtain the diaphragm; preferably, the drying temperature is 60-120°C.

[0200] It should be noted that the electrode slurry mentioned in the present invention refers to a fluid formed by mixing and uniformly dispersing electrode active materials, conductive agents, binders and other materials in a solvent, and the diaphragm slurry refers to a fluid formed by mixing and dispersing inorganic particles, binders and other materials in a solvent.

[0201] In some embodiments of the present invention, based on the total weight of the positive electrode slurry being 100%, the sum of the weight of the boric acid compound and the polymer containing active hydrogen functional groups accounts for 1-10% by weight of the positive electrode slurry;

[0202] Based on the total weight of the negative electrode slurry being 100%, the sum of the weight of the boric acid compound and the polymer containing active hydrogen functional groups accounts for 1-10% by weight of the negative electrode slurry;

[0203] Based on the total weight of the diaphragm slurry being 100%, the weight percentage of the sum of the weight of the boric acid compound and the polymer containing active hydrogen functional groups is 1-50%.

[0204] In a third aspect, the present invention further provides an electrode for a lithium-ion battery, comprising a current collector and an electrode material coated on the current collector, wherein the electrode material contains a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3, 4, 5, 6, 7, and 8.

[0205] Wherein, R1 is selected from one of hydroxyl, alkyl, phenyl, naphthyl or heteroaryl, and X1, X2, and X3 are each independently selected from one of the following groups:

[0206] Wherein, R2 is a hydrogen atom or an alkyl group;

[0207] Wherein, when X1, X2, X3 are each independently selected from When , O is directly connected to B, and C is directly connected to the polymer chain;

[0208] When X1, X2, and X3 are independently selected from When , O is directly connected to B, and S is directly connected to the polymer chain;

[0209] When X1, X2, and X3 are independently selected from When N is directly connected to B, C is directly connected to the polymer chain.

[0210] In some embodiments of the present invention, the heteroaryl group is selected from pyridyl, thienyl, pyrrolyl, thiazolyl, oxazolyl, pyrazinyl, pyrimidinyl, furanyl or indolyl.

[0211] In some embodiments of the present invention, the alkyl, phenyl, naphthyl or heteroaryl group may be substituted with one or more substituents, each of which is independently selected from a C1-6 alkyl group, a C1-6 haloalkyl group, a halogen, a C1-6 alkoxy group, a carbonyl group, a benzyloxy group, a cyano group or an ester group.

[0212] In some embodiments of the present invention, the substituents are each independently selected from C1-4 alkyl, C1-4 haloalkyl, halogen, C1-4 alkoxy, carbonyl, benzyloxy, cyano or ester.

[0213] In some embodiments of the present invention, the substituents are each independently selected from methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, fluoromethyl, difluoromethyl, trifluoromethyl, chloromethyl, bromomethyl, bromoethyl, fluoroethyl, chloroethyl, 1,1-difluoroethyl, 1,1-dichloroethyl, fluoropropyl, chloropropyl, trifluoromethyl, 1,1-difluoropropyl, 1,1,1-trifluoropropyl, fluorobutyl, chlorobutyl, 1,1-difluorobutyl alkyl, methyl phthalate ...

[0214] In some specific embodiments of the present invention, R1 is selected from hydroxyl, alkyl, phenyl, naphthyl, pyridinyl, thienyl, pyrrolyl, thiazolyl, oxazolyl, pyrazinyl, pyrimidinyl, furanyl or indolyl; the alkyl, phenyl, naphthyl, pyridinyl, thienyl, pyrrolyl, thiazolyl, oxazolyl, pyrazinyl, pyrimidinyl, furanyl or indolyl may be substituted with one or more substituents; the substituents are each independently selected from C1-6 alkyl, C1-6 haloalkyl, halogen, C1-6 alkoxy, carbonyl, benzyloxy, cyano or ester.

[0215] In some embodiments of the present invention, R1 is selected from hydroxyl, alkyl, phenyl, naphthyl, pyridinyl, thienyl, pyrrolyl, thiazolyl, oxazolyl, pyrazinyl, pyrimidinyl, furanyl or indolyl; the alkyl, phenyl, naphthyl, pyridinyl, thienyl, pyrrolyl, thiazolyl, oxazolyl, pyrazinyl, pyrimidinyl, furanyl or indolyl may be substituted with one or more substituents; the substituents are each independently selected from methyl, ethyl, propyl, isopropyl, n-butyl , isobutyl, tert-butyl, fluoromethyl, difluoromethyl, trifluoromethyl, chloromethyl, bromomethyl, bromoethyl, fluoroethyl, chloroethyl, 1,1-difluoroethyl, 1,1-dichloroethyl, fluoropropyl, chloropropyl, 1,1-difluoropropyl, 1,1,1-trifluoropropyl, fluorobutyl, chlorobutyl, 1,1-difluorobutyl, fluoro, chloro, bromo, iodo, methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, isopropoxy, tert-butoxy, ketone, formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, benzyloxy, cyano, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, tert-butyl phthalate, phenyl acetate, or dibutyl phthalate.

[0216] In some specific embodiments of the present invention, R1 is selected from hydroxyl, C1-6 alkyl, phenyl, halogen-substituted phenyl, alkyl-substituted phenyl, haloalkyl-substituted phenyl, cyano-substituted phenyl, carbonyl-substituted phenyl, alkoxy-substituted phenyl, naphthyl, pyridyl, thienyl, halogen-substituted thienyl, carbonyl-substituted thienyl, pyrrolyl, thiazolyl, oxazolyl, pyrazinyl, pyrimidinyl, halogen-substituted pyrimidinyl, furanyl, indolyl or ester-substituted indolyl.

[0217] In some specific embodiments of the present invention, R1 is selected from hydroxyl, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, phenyl, fluoro-substituted phenyl, chloro-substituted phenyl, ethylphenyl, n-propylphenyl, isopropylphenyl, butylphenyl, isobutylphenyl, tert-butylphenyl, chlorobenzyl, bromobenzyl, fluoromethyl-substituted phenyl, difluoromethyl-substituted phenyl, trifluoromethyl-substituted phenyl, chloromethyl-substituted phenyl, bromomethyl-substituted phenyl, bromoethyl-substituted phenyl, cyano-substituted phenyl, aldehyde-substituted phenyl, methoxy-substituted phenyl, ethoxy-substituted phenyl, propoxy-substituted phenyl, butoxy-substituted phenyl, naphthyl, pyridyl, thienyl, fluoro-substituted thienyl, chloro-substituted thienyl, keto-substituted thienyl, pyrrolyl, thiazolyl, oxazolyl, pyrazinyl, pyrimidinyl, fluoro-substituted pyrimidinyl, bromo-substituted pyrimidinyl, furanyl, indolyl or tert-butyl ester-substituted indolyl.

[0218] In some embodiments of the present invention, R1 is selected from hydroxy, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, phenyl,

[0219] It should be noted that the dotted line in the above R1 group selection represents a direct connection with B.

[0220] In some embodiments of the present invention, X1, X2, and X3 are each independently selected from one of the following groups:

[0221] Wherein R2 is a hydrogen atom or a C1-6 alkyl group.

[0222] In some embodiments of the present invention, X1, X2, and X3 are each independently selected from one of the following groups:

[0223] Wherein, R2 is a hydrogen atom, a methyl group, an ethyl group, a propyl group, a n-butyl group, an isobutyl group, a tert-butyl group, a n-pentyl group, an isopentyl group, a neopentyl group, a n-hexyl group, an isohexyl group, a tert-hexyl group or a tert-hexyl group.

[0224] It should be noted that the wavy lines in Formulas 1 to 6 described herein represent polymer chains.

[0225] In some embodiments of the present invention, the polymer chain is selected from one or more of polyolefins, polyethers, polyesters, polyamides, and polycarbonates.

[0226] In a specific embodiment of the present invention, the present invention also provides an electrode for a lithium ion battery, which includes a current collector and an electrode coating material coated on the current collector, wherein the electrode coating material contains a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3 and 4.

[0227] wherein R1 is selected from one of hydroxyl, alkyl or phenyl, X1, X2, X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or an alkyl;

[0228] The alkyl or phenyl group may be substituted with one or more substituents, and the substituents are selected in the same manner as the substituents for the alkyl, phenyl, naphthyl or heteroaryl groups described above.

[0229] In some embodiments of the present invention, R1 is selected from hydroxyl, C1-6 alkyl, phenyl, halogen-substituted phenyl, alkyl-substituted phenyl, haloalkyl-substituted phenyl, cyano-substituted phenyl, carbonyl-substituted phenyl or alkoxy-substituted phenyl.

[0230] In some specific embodiments of the present invention, R1 is selected from hydroxyl, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, phenyl, fluoro-substituted phenyl, chloro-substituted phenyl, ethylphenyl, n-propylphenyl, isopropylphenyl, butylphenyl, isobutylphenyl, tert-butylphenyl, chlorobenzyl, bromobenzyl, fluoromethyl-substituted phenyl, difluoromethyl-substituted phenyl, trifluoromethyl-substituted phenyl, chloromethyl-substituted phenyl, bromomethyl-substituted phenyl, bromoethyl-substituted phenyl, cyano-substituted phenyl, aldehyde-substituted phenyl, methoxy-substituted phenyl, ethoxy-substituted phenyl, propoxy-substituted phenyl or butoxy-substituted phenyl.

[0231] In some specific embodiments of the present invention, X1, X2, and X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or a C1-6 alkyl group.

[0232] In some specific embodiments of the present invention, X1, X2, and X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom, a methyl group, an ethyl group, a propyl group, a n-butyl group, an isobutyl group, a tert-butyl group, a n-pentyl group, an isopentyl group, a neopentyl group, a n-hexyl group, an isohexyl group, a tert-hexyl group, or a tert-hexyl group.

[0233] In some embodiments of the present invention, the polymer having a boron cross-linked structure is obtained by reacting a boric acid compound with a polymer containing an active hydrogen functional group; wherein the boric acid compound includes one or more of boric acid, phenylboric acid, phenyldiboric acid, 1,3,5-benzenetriboric acid, alkylboric acid, naphthaleneboric acid and heteroarylboronic acid.

[0234] In some embodiments of the present invention, the polymer having a boron cross-linked structure is obtained by reacting a boric acid compound with a polymer containing an active hydrogen functional group, wherein the boric acid compound includes one or more of boric acid, phenylboric acid and alkylboric acid, and the polymer containing an active hydrogen functional group includes one or more of a hydroxyl-containing polymer, a carboxyl-containing polymer, a sulfonic acid-containing polymer, a sulfate-containing polymer, a phosphate-containing polymer, an amino-containing polymer and a substituted amino-containing polymer.

[0235] Specifically, the present invention is to mix a boric acid compound and a polymer containing an active hydrogen functional group with an electrode slurry, then coat the slurry on a current collector, and then dry to obtain the electrode; preferably, the drying temperature is 60-120°C;

[0236] It should be noted that, as needed, when the boric acid compound and the polymer containing active hydrogen functional groups are mixed with the positive electrode slurry, the positive electrode of the lithium ion battery is obtained; when the boric acid compound and the polymer containing active hydrogen functional groups are mixed with the negative electrode slurry, the negative electrode of the lithium ion battery is obtained.

[0237] In some embodiments of the present invention, at 25-60°C, the boron-crosslinked polymer has a swelling degree greater than 50% in the electrolyte, preferably a swelling loss rate less than 5%, more preferably a swelling degree of 50-10,000%, further preferably a swelling degree of 100% to 5,000%, and even more preferably a swelling degree of 100% to 1,000%. When the swelling degree is less than 50%, the conductivity of the gel electrolyte formed by the polymer is very low, the internal resistance of the battery increases, thereby affecting the battery's charge and discharge rate performance and low-temperature cycling performance. When the swelling degree is greater than 10,000%, the mechanical properties of the boron-crosslinked polymer deteriorate and it may even dissolve in the electrolyte, losing its gel electrolyte function.

[0238] In a fourth aspect, the present invention also provides a method for preparing the above-mentioned lithium-ion electrode, comprising the following steps: mixing a boric acid compound and a polymer containing an active hydrogen functional group with an electrode slurry, then coating the slurry on a current collector, and then drying to obtain the electrode; preferably, the drying temperature is 60-120°C.

[0239] In some embodiments of the present invention, the electrode slurry comprises one or more of an active material, a conductive agent, a binder, and a solvent, wherein the active material is a positive electrode active material or a negative electrode active material.

[0240] In some embodiments of the present invention, based on 100% of the total weight of the electrode slurry, the weight percentage of the sum of the weight of the boric acid compound and the polymer containing active hydrogen functional groups is 1-10%.

[0241] In a fifth aspect, the present invention further provides a lithium-ion battery separator, comprising a polymer porous membrane and a separator coating material coated on the polymer porous membrane, wherein the separator coating material contains a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3, 4, 5, 6, 7 and 8.

[0242] wherein R1 is selected from one of hydroxyl, alkyl, phenyl, naphthyl or heteroaryl, and X1, X2, and X3 are each independently selected from one of the following groups:

[0243] Wherein, R2 is a hydrogen atom or an alkyl group;

[0244] Wherein, when X1, X2, X3 are each independently selected from When , O is directly connected to B, and C is directly connected to the polymer chain;

[0245] When X1, X2, and X3 are independently selected from When , O is directly connected to B, and S is directly connected to the polymer chain;

[0246] When X1, X2, and X3 are independently selected from When N is directly connected to B, C is directly connected to the polymer chain.

[0247] In some embodiments of the present invention, the heteroaryl group is selected from pyridyl, thienyl, pyrrolyl, thiazolyl, oxazolyl, pyrazinyl, pyrimidinyl, furanyl or indolyl.

[0248] In some embodiments of the present invention, the alkyl, phenyl, naphthyl or heteroaryl group may be substituted with one or more substituents, each of which is independently selected from a C1-6 alkyl group, a C1-6 haloalkyl group, a halogen, a C1-6 alkoxy group, a carbonyl group, a benzyloxy group, a cyano group or an ester group.

[0249] In some embodiments of the present invention, the substituents are each independently selected from C1-4 alkyl, C1-4 haloalkyl, halogen, C1-4 alkoxy, carbonyl, benzyloxy, cyano or ester.

[0250] In some embodiments of the present invention, the substituents are each independently selected from methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, fluoromethyl, difluoromethyl, trifluoromethyl, chloromethyl, bromomethyl, bromoethyl, fluoroethyl, chloroethyl, 1,1-difluoroethyl, 1,1-dichloroethyl, fluoropropyl, chloropropyl, trifluoromethyl, 1,1-difluoropropyl, 1,1,1-trifluoropropyl, fluorobutyl, chlorobutyl, 1,1-difluorobutyl alkyl, methyl phthalate ...

[0251] In some specific embodiments of the present invention, R1 is selected from hydroxyl, alkyl, phenyl, naphthyl, pyridinyl, thienyl, pyrrolyl, thiazolyl, oxazolyl, pyrazinyl, pyrimidinyl, furanyl or indolyl; the alkyl, phenyl, naphthyl, pyridinyl, thienyl, pyrrolyl, thiazolyl, oxazolyl, pyrazinyl, pyrimidinyl, furanyl or indolyl may be substituted with one or more substituents; the substituents are each independently selected from C1-6 alkyl, C1-6 haloalkyl, halogen, C1-6 alkoxy, carbonyl, benzyloxy, cyano or ester.

[0252] In some embodiments of the present invention, R1 is selected from hydroxyl, alkyl, phenyl, naphthyl, pyridinyl, thienyl, pyrrolyl, thiazolyl, oxazolyl, pyrazinyl, pyrimidinyl, furanyl or indolyl; the alkyl, phenyl, naphthyl, pyridinyl, thienyl, pyrrolyl, thiazolyl, oxazolyl, pyrazinyl, pyrimidinyl, furanyl or indolyl may be substituted with one or more substituents; the substituents are each independently selected from methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, fluoromethyl, difluoromethyl, trifluoromethyl, chloromethyl, bromomethyl, bromoethyl, fluoroethyl, chloroethyl, 1,1-difluoroethyl , 1,1-dichloroethyl, fluoropropyl, chloropropyl, 1,1-difluoropropyl, 1,1,1-trifluoropropyl, fluorobutyl, chlorobutyl, 1,1-difluorobutyl, fluoro, chloro, bromo, iodo, methoxy, ethoxy, propoxy, butoxy, pentyloxy, hexyloxy, isopropoxy, tert-butoxy, ketone, formaldehyde, acetaldehyde, propionaldehyde, benzaldehyde, benzyloxy, cyano, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, tert-butyl ester, phenyl acetate or dibutyl phthalate.

[0253] In some specific embodiments of the present invention, R1 is selected from hydroxyl, C1-6 alkyl, phenyl, halogen-substituted phenyl, alkyl-substituted phenyl, haloalkyl-substituted phenyl, cyano-substituted phenyl, carbonyl-substituted phenyl, alkoxy-substituted phenyl, naphthyl, pyridyl, thienyl, halogen-substituted thienyl, carbonyl-substituted thienyl, pyrrolyl, thiazolyl, oxazolyl, pyrazinyl, pyrimidinyl, halogen-substituted pyrimidinyl, furanyl, indolyl or ester-substituted indolyl.

[0254] In some specific embodiments of the present invention, R1 is selected from hydroxyl, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, phenyl, fluoro-substituted phenyl, chloro-substituted phenyl, ethylphenyl, n-propylphenyl, isopropylphenyl, butylphenyl, isobutylphenyl, tert-butylphenyl, chlorobenzyl, bromobenzyl, fluoromethyl-substituted phenyl, difluoromethyl-substituted phenyl, trifluoromethyl-substituted phenyl, chloromethyl-substituted phenyl, bromomethyl-substituted phenyl, bromoethyl-substituted phenyl, cyano-substituted phenyl, aldehyde-substituted phenyl, methoxy-substituted phenyl, ethoxy-substituted phenyl, propoxy-substituted phenyl, butoxy-substituted phenyl, naphthyl, pyridyl, thienyl, fluoro-substituted thienyl, chloro-substituted thienyl, keto-substituted thienyl, pyrrolyl, thiazolyl, oxazolyl, pyrazinyl, pyrimidinyl, fluoro-substituted pyrimidinyl, bromo-substituted pyrimidinyl, furanyl, indolyl or tert-butyl ester-substituted indolyl.

[0255] In some embodiments of the present invention, R1 is selected from hydroxy, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, phenyl,

[0256] It should be noted that the dotted line in the above R1 group selection represents a direct connection with B.

[0257] In some embodiments of the present invention, X1, X2, and X3 are each independently selected from one of the following groups:

[0258] Wherein R2 is a hydrogen atom or a C1-6 alkyl group.

[0259] In some embodiments of the present invention, X1, X2, and X3 are each independently selected from one of the following groups:

[0260] wherein R2 is a hydrogen atom, a methyl group, an ethyl group, a propyl group, a n-butyl group, an isobutyl group, a tert-butyl group, a n-pentyl group, an isopentyl group, a neopentyl group, a n-hexyl group, an isohexyl group, a tert-hexyl group or a tert-hexyl group.

[0261] It should be noted that the wavy lines in Formulas 1 to 6 described herein represent polymer chains.

[0262] In some embodiments of the present invention, the polymer chain is selected from one or more of polyolefins, polyethers, polyesters, polyamides, and polycarbonates.

[0263] In a specific embodiment of the present invention, the present invention also provides a lithium ion battery separator, which includes a polymer porous membrane and a separator coating material coated on the polymer porous membrane, wherein the separator coating material contains a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3 and 4.

[0264] wherein R1 is selected from one of hydroxyl, alkyl or phenyl, X1, X2, X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or an alkyl;

[0265] Preferably, the polymer porous membrane is a polyolefin microporous membrane or a non-woven fabric.

[0266] The alkyl or phenyl group may be substituted with one or more substituents, and the substituents are selected in the same manner as the substituents for the alkyl, phenyl, naphthyl or heteroaryl groups described above.

[0267] In some embodiments of the present invention, R1 is selected from hydroxyl, C1-6 alkyl, phenyl, halogen-substituted phenyl, alkyl-substituted phenyl, haloalkyl-substituted phenyl, cyano-substituted phenyl, carbonyl-substituted phenyl or alkoxy-substituted phenyl.

[0268] In some specific embodiments of the present invention, R1 is selected from hydroxyl, methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert-butyl, phenyl, fluoro-substituted phenyl, chloro-substituted phenyl, ethylphenyl, n-propylphenyl, isopropylphenyl, butylphenyl, isobutylphenyl, tert-butylphenyl, chlorobenzyl, bromobenzyl, fluoromethyl-substituted phenyl, difluoromethyl-substituted phenyl, trifluoromethyl-substituted phenyl, chloromethyl-substituted phenyl, bromomethyl-substituted phenyl, bromoethyl-substituted phenyl, cyano-substituted phenyl, aldehyde-substituted phenyl, methoxy-substituted phenyl, ethoxy-substituted phenyl, propoxy-substituted phenyl or butoxy-substituted phenyl.

[0269] In some specific embodiments of the present invention, X1, X2, and X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or a C1-6 alkyl group.

[0270] In some specific embodiments of the present invention, X1, X2, and X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom, a methyl group, an ethyl group, a propyl group, a n-butyl group, an isobutyl group, a tert-butyl group, a n-pentyl group, an isopentyl group, a neopentyl group, a n-hexyl group, an isohexyl group, a tert-hexyl group, or a tert-hexyl group.

[0271] In some embodiments of the present invention, the polymer having a boron cross-linked structure is obtained by reacting a boric acid compound with a polymer containing an active hydrogen functional group, wherein the boric acid compound includes one or more of boric acid, phenylboric acid, phenyldiboric acid, 1,3,5-benzenetriboric acid, alkylboric acid, naphthaleneboric acid and heteroarylboronic acid.

[0272] In some embodiments of the present invention, the polymer having a boron cross-linked structure is obtained by reacting a boric acid compound with a polymer containing an active hydrogen functional group; wherein the boric acid compound includes one or more of boric acid, phenylboric acid and alkylboric acid.

[0273] The heteroaryl group in the heteroarylboronic acid is selected from pyridyl, pyrazinyl, pyrimidinyl, furyl, pyrrolyl, thienyl, thiazolyl or oxazolyl.

[0274] The phenyl, alkyl, naphthyl, and heteroaryl groups in the phenylboronic acid, alkylboronic acid, naphthaleneboronic acid, and heteroarylboronic acid may be substituted with one or more substituents. The substituents are selected in the same manner as the substituents for the alkyl, phenyl, naphthyl, and heteroaryl groups described above.

[0275] Preferably, phenylboronic acid includes but is not limited to 5-chloro-2-methoxyphenylboronic acid, 4-cyanophenylboronic acid, 5-formyl-2-methoxyphenylboronic acid, 4-isopropylphenylboronic acid, 2-chloro-4-methylphenylboronic acid, 3-chloro-5-trifluoromethylphenylboronic acid or 4-benzyloxy-3-methoxyphenylboronic acid; preferably, phenyldiboronic acid includes but is not limited to 1,3-phenyldiboronic acid and / or 1,4-phenyldiboronic acid; preferably, alkylboronic acid includes but is not limited to methylboronic acid, ethylboronic acid, propylboronic acid, isopropylboronic acid, n-butylboronic acid, isobutylboronic acid, tert-butylboronic acid or fluoromethylboronic acid; preferably, naphthaleneboronic acid includes but is not limited to 1-naphthaleneboronic acid, 2-naphthaleneboronic acid, 1,5-dinaphthylboronic acid or 2,6-dinaphthylboronic acid; preferably, heteroarylboronic acid includes but is not limited to 3-pyridineboronic acid, 2-fluoro-3-pyridineboronic acid, 2-bromopyridine-4-boronic acid, 2-thiopheneboronic acid, (4-fluorothiophen-2-yl)boronic acid, 5-acetyl-2-thiopheneboronic acid, 2-chlorothiophene-3-boronic acid, 2-furanboronic acid, 2-pyrroleboric acid, 3-quinolineboronic acid, 2-imidazoleboronic acid or N-(BOC)-7-fluoroindole-2-boronic acid.

[0276] The polymer containing active hydrogen functional groups includes one or more of hydroxyl-containing polymers, carboxyl-containing polymers, sulfonic acid-containing polymers, sulfate-containing polymers, phosphate-containing polymers, amino-containing polymers and substituted amino-containing polymers.

[0277] The polymer containing active hydrogen functional groups includes one or more of polyolefins containing active hydrogen functional groups, polyethers containing active hydrogen functional groups, polyesters containing active hydrogen functional groups, polyamides containing active hydrogen functional groups, and polycarbonates containing active hydrogen functional groups. Preferably, the polymer in the polymer containing active hydrogen functional groups includes one or more of polyolefins, polyethers, polyesters, polyamides, and polycarbonates.

[0278] Specifically, the present invention obtains a diaphragm containing a polymer with a boron cross-linked structure by mixing a boric acid compound and a polymer containing an active hydrogen functional group with a diaphragm slurry, coating, and drying.

[0279] In some embodiments of the present invention, at 25-60°C, the boron-crosslinked polymer has a swelling degree greater than 50% in the electrolyte, preferably a swelling loss rate less than 5%, more preferably a swelling degree of 50-10,000%, further preferably a swelling degree of 100% to 5,000%, and even more preferably a swelling degree of 100% to 1,000%. When the swelling degree is less than 50%, the conductivity of the gel electrolyte formed by the polymer is very low, the internal resistance of the battery increases, thereby affecting the battery's charge and discharge rate performance and low-temperature cycling performance. When the swelling degree is greater than 10,000%, the mechanical properties of the boron-crosslinked polymer deteriorate and it may even dissolve in the electrolyte, losing its gel electrolyte function.

[0280] In a sixth aspect, the present invention also provides a method for preparing the above-mentioned lithium-ion battery diaphragm, comprising the following steps: mixing a boric acid compound and a polymer containing an active hydrogen functional group with a diaphragm slurry, then coating the slurry on a polymer porous membrane, and then drying to obtain the diaphragm; preferably, the drying temperature is 60-120°C.

[0281] In some embodiments of the present invention, the diaphragm slurry contains inorganic particles and / or a binder and a solvent.

[0282] Based on the total weight of the diaphragm slurry being 100%, the sum of the weights of the boric acid compound and the polymer containing active hydrogen functional groups accounts for 1-50% of the weight of the diaphragm slurry.

[0283] The present application will be further described below with reference to the following examples. It should be understood that these examples are only used to illustrate the present application and are not intended to limit the scope of the present application.

[0284] The raw material or reagent used in the present invention are all purchased from the market mainstream manufacturers, and those who do not specify the manufacturer or those who do not specify the concentration are all the raw materials or reagents of the analytical grade that can be routinely obtained. As long as the desired effect can be played, there are no particular restrictions. The instrument and equipment used in the present embodiment are all purchased from the main manufacturers in the market. As long as the desired effect can be played, there are no particular restrictions. In the present embodiment, those who do not specify specific technology or conditions are carried out according to the technology or conditions described in the document in this area or according to the product specification.

[0285] Reagents:

[0286] Adipic acid, ethylene glycol, hexamethylenediamine, ethylenediamine, acrylonitrile, butyl acrylate, glycidyl methacrylate, p-styrenesulfonic acid, acrylic acid, acrylamide, triethylene glycol, polyethylene glycol PEG400, polyethylene glycol PEG1000, polypropylene glycol PPG2000, polypropylene glycol PPG4000, polyethylene glycol PEG50000, decaglycerol, dipentaerythritol, pentaerythritol, caprolactone, N,N-dimethylformamide, sulfuric acid, ethylene carbonate, propylene carbonate, boric acid, phenylboric acid, 1,4-phenylenediboric acid, trimesic acid, pyromellitic acid, chlorosulfonic acid, LiNi 0.8 Co 0.1 Mn 0.1 O2, conductive agent (Super Li), PVDF binder ( 5130), N-methylpyrrolidone, artificial graphite, sodium carboxymethyl cellulose, styrene-butadiene rubber emulsion (SBR) (solid content 50%), alumina powder, polyethylene porous film, lithium hexafluorophosphate, ethylene carbonate (EC), ethyl methyl carbonate (EMC), vinylene carbonate, 1,3-propane sultone, etc. were purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0287] LiNi 0.8 Co 0.1 Mn 0.1 O2 was purchased from Hubei Rongbai Lithium Battery Materials Co., Ltd.;

[0288] Conductive agent (Super Li), PVDF binder ( 5130) was purchased from SOLVAY (SHANGHAI) Co., Ltd;

[0289] Artificial graphite was purchased from Tianjin Better New Energy Technology Co., Ltd.

[0290] Styrene-butadiene rubber latex (SBR) (solid content 50%), alumina powder, polyethylene porous film, lithium hexafluorophosphate, ethylene carbonate (EC), ethyl methyl carbonate (EMC), and vinylene carbonate were purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0291] Hereinafter, the present invention will be described in more detail using various preparation examples, embodiments, and comparative examples, but the technical scope of the present invention is not limited to these examples. It should be noted that, unless otherwise specifically stated, all percentages, parts, and ratios used in the present invention are by mass.

[0292] Preparation Example 1

[0293] 1.1 Preparation of oligomers

[0294] 146 g of adipic acid (1 mol) and 68.2 g of ethylene glycol (1.1 mol) were added to a reactor at a molar ratio of adipic acid to ethylene glycol of 1:1.1. 0.86 g of p-toluenesulfonic acid was added as a catalyst. The reaction was carried out under vacuum at 160° C. for 10 h, washed with deionized water, and then dried at 90° C. for 5 h to obtain a hydroxyl-containing polyester oligomer 1, the structural formula of which is as follows:

[0295] 1.2 Preparation of polymers with boron cross-linked structures

[0296] 180 g of oligomer 1 (0.1 mol) and 4.2 g of boric acid (0.067 mol) were added to a reactor in a molar ratio of oligomer 1 to boric acid of 3:2. Then, 100% of methylpyrrolidone (NMP) relative to the total mass of the reaction raw materials was added as a solvent. The mixture was stirred and dissolved at room temperature. The temperature was raised to 80° C. and vacuumed to remove water. After about 8 hours, almost no water was precipitated. The vacuuming and heating were stopped, and the solvent NMP was removed by vacuum drying to obtain a polymer with a boron cross-linked structure.

[0297] Preparation Example 2

[0298] 2.1 Preparation of oligomers

[0299] 13.6 g of dried pentaerythritol (0.1 mol) and 91.5 g of caprolactone monomer (0.8 mol) were added to a reactor at a molar ratio of pentaerythritol to caprolactone of 1:8. 100% of N,N-dimethylformamide (DMF) was added as a solvent relative to the total mass of the reaction raw materials. 0.3% of sulfuric acid was added as a catalyst relative to the total mass of the reaction raw materials. The mixture was reacted at 100° C. for 24 h and then vacuum dried at 90° C. for 5 h to obtain a hydroxyl-containing polyester oligomer 2, the structural formula of which is as follows:

[0300] 2.2 Preparation of polymers with boron cross-linked structures

[0301] 105 g of oligomer 2 (0.1 mol) and 8.24 g of boric acid (0.13 mol) were added to the reactor in a molar ratio of oligomer 2 to boric acid of 3:4. NMP was then added as a solvent in an amount of 100% relative to the total mass of the reaction raw materials. The mixture was fully stirred and dissolved at room temperature. The mixture was heated to 90°C and vacuum-dried to remove water. After about 8 hours, almost no water was precipitated. The vacuuming and heating were stopped, and the solvent NMP was removed by vacuum drying to obtain a polymer with a boron cross-linked structure.

[0302] Preparation Example 3

[0303] 3.1 Preparation of oligomers

[0304] 2.54 g of dried dipentaerythritol (0.01 mol) and 183.6 g of propylene carbonate monomer (1.8 mol) were added to a reactor, with a molar ratio of dipentaerythritol to propylene carbonate being 1:180. 150% of NMP relative to the total mass of the reaction raw materials was added as a solvent, and 0.3% of stannous octoate relative to the total mass of the reaction raw materials was added as a catalyst. The reaction was carried out at 90° C. under nitrogen protection for 12 h. The reaction was stopped and cooled to 0° C., followed by the addition of 6.99 g of chlorosulfonic acid HSO 3 Cl (0.06 mol), with a molar ratio of chlorosulfonic acid to dipentaerythritol being 6:1. The product was washed with water and dried to obtain a sulfate-containing polycarbonate oligomer 3, the structural formula of which is as follows:

[0305] 3.2 Preparation of polymers with boron cross-linked structures

[0306] 768 g of oligomer 3 (0.04 mol) and 15 g of phenylboric acid (0.12 mol) were added to the reactor in a molar ratio of oligomer 3 to phenylboric acid of 1:3. NMP was then added as a solvent in an amount of 100% relative to the total mass of the reaction raw materials. The mixture was fully stirred and dissolved at room temperature. The mixture was heated to 100° C. and vacuum-dried to remove water. After about 10 hours, almost no water was precipitated. The vacuuming and heating were stopped, and the solvent NMP was removed by vacuum drying to obtain a polymer with a boron cross-linked structure.

[0307] Preparation Example 4

[0308] 4.1 Preparation of oligomers

[0309] 31 g of dried ethylene glycol (0.5 mol) and 264 g of ethylene carbonate monomer (3 mol) were added to a reactor at a molar ratio of ethylene glycol to ethylene carbonate of 1:6. 100% of DMF as a solvent and 0.5% of stannous octoate as a catalyst were added relative to the total mass of the reaction raw materials. The mixture was reacted at 90° C. under nitrogen protection for 12 h. Subsequently, 98 g of phosphoric acid (1 mol) was added at a molar ratio of phosphoric acid to ethylene glycol of 2:1. The mixture was reacted at 90° C. overnight and vacuum dried to obtain a polycarbonate oligomer 4 containing a phosphoric acid group, the structural formula of which is as follows:

[0310] 4.2 Preparation of polymers with boron cross-linked structures

[0311] 150 g of oligomer 4 (0.2 mol) and 16.5 g of boric acid (0.27 mol) were added to the reactor, with a molar ratio of oligomer 4 to boric acid of 0.74. NMP was then added as a solvent in an amount of 100% relative to the total mass of the reaction raw materials. The mixture was fully stirred and dissolved at room temperature. The temperature was raised to 100° C. and vacuumed to remove water. After about 10 hours, almost no water was precipitated. The vacuuming and heating were stopped, and the solvent NMP was removed by vacuum drying to obtain a polymer with a boron cross-linked structure.

[0312] Preparation Example 5

[0313] 5.1 Preparation of oligomers

[0314] 105 g of dried trimesic acid (0.5 mol) and 64 g of hexamethylenediamine (0.55 mol) were added to a reactor at a molar ratio of 1:1.1. The mixture was reacted at 250° C. under vacuum for 12 h to obtain a polyamide oligomer 5 containing amino and carboxyl groups. The structural formula is as follows:

[0315] 5.2 Preparation of polymers with boron cross-linked structures

[0316] 63.6 g of oligomer 5 (0.02 mol) and 10 g of 1,4-phenylenediboronic acid (0.06 mol) were added to a reactor in a molar ratio of oligomer 5 to 1,4-phenylenediboronic acid of 1:3. NMP was then added as a solvent in an amount of 100% relative to the total mass of the reaction raw materials. The mixture was fully stirred and dissolved at room temperature. The temperature was raised to 100° C. and vacuum-dried to remove water. After about 10 hours, almost no water was precipitated. The vacuuming and heating were stopped, and the solvent NMP was removed by vacuum drying to obtain a polymer with a boron cross-linked structure.

[0317] Preparation Example 6

[0318] 6.1 Preparation of oligomers

[0319] 267 g of dried pyromellitic acid (1.05 mol) and 60 g of ethylenediamine (1 mol) were added to a reaction kettle at a molar ratio of 1.05:1. The mixture was reacted at 250° C. under vacuum for 12 h to obtain a carboxyl-containing polyamide oligomer 6, with the following structural formula:

[0320] 6.2 Preparation of Polymers with Boron Crosslinking Structures

[0321] 123 g of oligomer 6 (0.02 mol) and 36 g of 1,4-phenylenediboronic acid (0.215 mol) were added to a reactor in a molar ratio of oligomer 6 to 1,4-phenylenediboronic acid of 1:10.75. NMP was then added as a solvent in an amount of 200% relative to the total mass of the reaction raw materials. The mixture was fully stirred and dissolved at room temperature. The temperature was raised to 100° C. and vacuumed to remove water. After about 10 hours, almost no water was precipitated. The vacuuming and heating were stopped, and the solvent NMP was removed by vacuum drying to obtain a polymer with a boron cross-linked structure.

[0322] Preparation Example 7

[0323] 7.1 Preparation of oligomers

[0324] 24 g of dibenzoyl peroxide (BPO, 0.1 mol), 85 g of acrylamide (AM, 1.2 mol), 230 g of butyl acrylate (BA, 1.8 mol) and 183 g of p-styrenesulfonic acid (SSA, 1 mol) were added to a reactor in a molar ratio of BPO, AM, BA and SSA of 1:12:18:10. NMP was then added as a solvent in an amount of 200% relative to the total mass of the raw materials. The mixture was reacted at 80° C. under nitrogen protection for 10 h. The reaction was stopped and the mixture was vacuum dried to obtain a polyolefin oligomer 7 containing amino groups and sulfonic acid groups, the structural formula of which is as follows:

[0325] 7.2 Preparation of Polymers with Boron Crosslinking Structures

[0326] 100 g of oligomer 7 (0.02 mol) and 9.3 g of boric acid (0.15 mol) were added to a reactor in a molar ratio of oligomer 7 to boric acid of 1:7.5. Then, 200% of NMP relative to the total mass of the reaction raw materials was added as a solvent. The mixture was fully stirred and dissolved at room temperature. The temperature was raised to 100° C. and vacuumed to remove water. After about 8 hours, almost no water was precipitated. The vacuuming and heating were stopped, and the solvent NMP was removed by vacuum drying to obtain a polymer with a boron cross-linked structure.

[0327] Preparation Example 8

[0328] 8.1 Preparation of oligomers

[0329] 16.4 g of dibenzoyl peroxide (AIBN, 0.1 mol), 53 g of acrylonitrile (AN, 1.0 mol), 142 g of glycidyl methacrylate (GMA, 1.0 mol) and 36 g of acrylic acid (AA, 0.5 mol) were added to a reactor, with the molar ratio of AIBN, AN, GMA and AA being 1:10:10:5. NMP was then added as a solvent in an amount of 200% relative to the total mass of the reaction raw materials. The reaction was carried out at 80° C. under nitrogen protection for 10 h. Water was then added in an amount of 50% relative to the total mass of the reaction raw materials, and the reaction was refluxed at 100° C. The reaction was stopped after the solution became completely transparent, and the solution was vacuum dried to obtain a polyolefin oligomer 8 containing hydroxyl and carboxyl groups, the structural formula of which is as follows:

[0330] 8.2 Preparation of Polymers with Boron Crosslinking Structures

[0331] 100 g of oligomer 8 (0.04 mol) and 20 g of boric acid (0.323 mol) were added to a reactor with a molar ratio of oligomer 8 to boric acid of 0.124:1. Water in an amount of 200% relative to the total mass of the reaction raw materials was added as a solvent, and the mixture was fully stirred and dissolved at room temperature. The mixture was heated to 100° C. and vacuum-dried to remove water. After about 8 hours, almost no water was precipitated. The vacuuming and heating were stopped, and the solvent NMP was removed by vacuum drying to obtain a polymer with a boron cross-linked structure.

[0332] Preparation Example 9

[0333] 9.1 Preparation of oligomers

[0334] 80 g of polyethylene glycol (PEG400, 0.2 mol) and 49 g of 1,3-propane sultone (1,3-PS, 0.4 mol) were added to a reactor at a molar ratio of PEG to 1,3-PS of 1:2. 100% of NMP relative to the total mass of the reaction raw materials was added as a solvent. The reaction was carried out at 40° C. for 24 h. The solvent NMP and water were removed, and the mixture was vacuum-dried to obtain a sulfonic acid group-containing polyether oligomer 9, whose structural formula is as follows:

[0335] 9.2 Preparation of Polymers with Boron Crosslinking Structures

[0336] 129 g of oligomer 9 (0.2 mol) and 16.6 g of 1,4-phenylenediboronic acid (0.1 mol) were added to a reactor in a molar ratio of 2:1. Water (100% by weight relative to the total mass of the reaction raw materials) was then added as a solvent. The mixture was stirred and dissolved at room temperature. The temperature was raised to 100° C. and vacuumed to remove water. After about 8 hours, almost no water was precipitated. The vacuuming and heating were stopped to obtain a polymer with a boron cross-linked structure.

[0337] Preparation Example 10

[0338] 10.1 Preparation of oligomers

[0339] Oligomer 10 is a polyether decaglycerol (commercially available) containing multiple hydroxyl groups, and its molecular structure is as follows:

[0340] 10.2 Preparation of Polymers with Boron Crosslinking Structures

[0341] 76 g of oligomer 10 (0.1 mol) and 12.36 g of boric acid (0.2 mol) were added to a reactor in a molar ratio of oligomer 10 to boric acid of 1:2. Water in an amount of 100% relative to the total mass of the reaction raw materials was added as a solvent, and the mixture was fully stirred and dissolved at room temperature. The mixture was heated to 100° C. and vacuumed to remove water. After about 8 hours, almost no water was precipitated. The vacuuming and heating were stopped to obtain a polymer with a boron cross-linked structure.

[0342] Preparation Example 11

[0343] 11.1 Preparation of Oligomers

[0344] Oligomer 11 is polyethylene glycol PEG400 (commercially available).

[0345] 11.2 Preparation of Polymers with Boron Crosslinking Structures

[0346] 80 g of oligomer 11 (0.2 mol) and 9 g of boric acid (0.146 mol) were added to the reactor, with the molar ratio of oligomer 11 to boric acid being 1.37:1. Water in an amount of 100% relative to the total mass of the reaction raw materials was then added as a solvent, and the mixture was fully stirred and dissolved at room temperature. The mixture was heated to 100° C. and vacuumed to remove water. After about 8 hours, almost no water was precipitated. The vacuuming and heating were stopped to obtain a polymer with a boron cross-linked structure.

[0347] Preparation Example 12

[0348] 12.1 Preparation of Oligomers

[0349] Oligomer 12 is polyethylene glycol PEG1000 (commercially available).

[0350] 12.2 Preparation of Polymers with Boron Crosslinking Structures

[0351] 100 g of oligomer 12 (0.1 mol) and 4 g of boric acid (0.064 mol) were added to the reactor with a molar ratio of oligomer 12 to boric acid of 1.56:1. Water in an amount of 100% relative to the total mass of the reaction raw materials was added as a solvent, and the mixture was fully stirred and dissolved at room temperature. The mixture was heated to 100° C. and vacuumed to remove water. After about 8 hours, almost no water was precipitated. The vacuuming and heating were stopped to obtain a polymer with a boron cross-linked structure.

[0352] Preparation Example 13

[0353] 13.1 Preparation of Oligomers

[0354] Oligomer 13 is polypropylene glycol PPG2000 (commercially available).

[0355] 13.2 Preparation of Polymers with Boron Crosslinking Structures

[0356] 20 g of oligomer 13 (0.01 mol) and 0.36 g of boric acid (0.006 mol) were added to a reactor with a molar ratio of oligomer 13 to boric acid of 1.67:1. Water in an amount of 100% relative to the total mass of the reaction raw materials was added as a solvent, and the mixture was fully stirred and dissolved at room temperature. The mixture was heated to 100°C and vacuumed to remove water. After about 8 hours, almost no water was precipitated. The vacuuming and heating were stopped to obtain a polymer with a boron cross-linked structure.

[0357] Preparation Example 14

[0358] 14.1 Preparation of Oligomers

[0359] Oligomer 14 is polypropylene glycol PPG4000 (commercially available).

[0360] 14.2 Preparation of Polymers with Boron Crosslinking Structures

[0361] 40 g of oligomer 14 (0.01 mol) and 0.36 g of boric acid (0.006 mol) were added to a reactor at a molar ratio of oligomer 14 to boric acid of 1.67:1. Water in an amount of 100% relative to the total mass of the reaction raw materials was added as a solvent, and the mixture was fully stirred and dissolved at room temperature. The mixture was heated to 100° C. and vacuumed to remove water. After about 8 hours, almost no water was precipitated. The vacuuming and heating were stopped to obtain a polymer with a boron cross-linked structure.

[0362] Preparation Example 15

[0363] 15.1 Preparation of Oligomers

[0364] Oligomer 15 is polyethylene glycol PEG50000 (commercially available).

[0365] 15.2 Preparation of Polymers with Boron Crosslinking Structures

[0366] 500 g of oligomer 15 (PEG50000, 0.01 mol) and 0.3 g of boric acid (0.005 mol) were added to a reactor at a molar ratio of oligomer 15 to boric acid of 2:1. Water in an amount of 100% relative to the total mass of the reaction raw materials was added as a solvent, and the mixture was fully stirred and dissolved at room temperature. The mixture was heated to 100° C. and vacuumed to remove water. After about 8 hours, almost no water was precipitated. The vacuuming and heating were stopped to obtain a polymer with a boron cross-linked structure.

[0367] Preparation Example 16

[0368] 16.1 Preparation of Oligomers

[0369] Oligomer 16 is a polyether triethylene glycol TEG (commercially available) containing two hydroxyl groups, and its molecular structure is as follows:

[0370] 16.2 Preparation of Polymers with Boron Crosslinking Structures

[0371] 200 g of oligomer 16 (TEG, 1.33 mol) and 55 g of boric acid (0.89 mol) were added to a reactor in a molar ratio of oligomer 16 to boric acid of 3:2. Water in an amount of 100% relative to the total mass of the reaction raw materials was added as a solvent, and the mixture was fully stirred and dissolved at room temperature. The mixture was heated to 100°C and vacuumed to remove water. After about 8 hours, almost no water was precipitated. The vacuuming and heating were stopped to obtain a polymer with a boron cross-linked structure.

[0372] It should be noted that there is no particular limitation on the amount of solvents such as water, DMF, and NMP used in the above preparation examples, as long as they can achieve a dissolving effect and facilitate subsequent drying, and can be, for example, 100%-500% relative to the total mass of the reaction raw materials.

[0373] The following method was used to test the properties of the polymer having a boron cross-linked structure. The test results are shown in Table 1.

[0374] (1) Determination of molecular weight and molecular weight distribution of oligomers: The absolute molecular weight and molecular weight distribution of oligomers were determined by gel permeation chromatography-laser light scattering (GPC-MALLS) method. The gel permeation chromatography instrument was a 1515GPC gel permeation chromatography instrument from Waters, USA, and the light scattering detector was a DAWN HELEOS-II light scattering detector from Wyatt, USA.

[0375] (2) Determination of swelling degree:

[0376] A boron-crosslinked polymer was made into a 30μm thick, 16mm*16mm circular film. The film was weighed and immersed in 10g of electrolyte. The film was sealed and stored at 60°C. Every 8 hours, the film was removed, the electrolyte on the surface was wiped off, the thickness was measured and weighed, and the film was returned to the electrolyte, sealed, and stored at 60°C. If the film thickness and mass remain unchanged after three consecutive tests, the boron-crosslinked polymer film is considered to have reached swelling equilibrium. The swelling degree is calculated according to the following formula:

[0377] In the above formula, m0 represents the mass of the polymer membrane with a boron cross-linked structure before immersion in the electrolyte, and m1 represents the mass of the polymer membrane with a boron cross-linked structure when the membrane reaches swelling equilibrium after immersion in the electrolyte.

[0378] The electrolyte was prepared as follows: lithium hexafluorophosphate (LiPF6) was dissolved in a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (the volume ratio of EC to EMC was 3:7) in a glove box with a dew point below -40°C to prepare an electrolyte with a LiPF6 concentration of 1.2 mol / L. Then, 1.5% of the weight of the entire electrolyte, vinylene carbonate (VC) and 1% of 1,3-propane sultone (1,3-PS) were added to obtain the required electrolyte.

[0379] (3) Determination of swelling loss rate:

[0380] A polymer with a boron cross-linked structure was made into a 30 μm thick, 16 mm * 16 mm circular film. The mass of the film was weighed and immersed in 10 g of electrolyte. The film was sealed and stored at 60 ° C. The film was taken out every 8 hours, the electrolyte on the surface was wiped off, the thickness was measured and weighed, and then it was returned to the electrolyte and sealed and continued to be stored at 60 ° C. After three consecutive tests, the thickness and mass of the film remained unchanged. The excess electrolyte and lithium salt on the film were rinsed with dimethyl carbonate (DMC) solvent and completely dried in an oven. The mass of the remaining film after drying was weighed, and the swelling loss rate was calculated according to the following formula:

[0381] In the above formula, m0 represents the mass of the polymer membrane with a boron cross-linked structure before immersion in the electrolyte, and the unit is g; m2 represents the mass of the polymer membrane with a boron cross-linked structure remaining after immersion in the electrolyte and then washing and drying, and the unit is g.

[0382] The electrolyte was prepared as follows: lithium hexafluorophosphate (LiPF6) was dissolved in a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (the volume ratio of EC to EMC was 3:7) in a glove box with a dew point below -40°C to prepare an electrolyte with a LiPF6 concentration of 1.2 mol / L. Then, 1.5% of the weight of the entire electrolyte, vinylene carbonate (VC) and 1% of 1,3-propane sultone (1,3-PS) were added to obtain the required electrolyte.

[0383] Example 1

[0384] 1. Battery production

[0385] 1.1 Preparation of positive electrode plate

[0386] The positive electrode active material LiNi 0.8 Co0.1 Mn 0.1 O2, carbon black conductive agent (Super Li), PVDF binder ( 5130) were mixed in a double planetary mixer at a weight ratio of 96.5:1.5:2. The total weight of the positive electrode active material, carbon black conductive agent, and binder was 1 kg. 0.5 kg of N-methylpyrrolidone (NMP) was added and thoroughly stirred. 20 g (0.011 mol, of which the molar amount of hydroxyl groups was 0.022 mol) of oligomer 1 and 0.467 g (0.007 mol) of boric acid were then added. Stirring was continued and filtered through a filter to obtain a slurry with a solid content of 65%. The slurry was then applied to both sides of a 12 μm thick aluminum foil using an extrusion coater. After baking and hot roller pressing, a positive electrode plate was obtained. The surface density of the coating on one side of the positive electrode plate was 20 mg / cm 2 The thickness of the single-side coating was 58 μm, and the obtained positive electrode plate was placed in a vacuum oven at 120° C. and dried for more than 24 hours to obtain a positive electrode.

[0387] 1.2 Preparation of negative electrode

[0388] The negative electrode active material artificial graphite, carbon black conductive agent (Super Li) and sodium carboxymethyl cellulose (CMC) were mixed in a weight ratio of 97:1.5:1.5 and then put into a double planetary mixer. The total weight of the negative electrode active material, carbon black conductive agent and sodium carboxymethyl cellulose was 1 kg. 0.8 kg of deionized water (DIW) was added and the solid content was set to 50%. After thorough stirring, 50% solid content styrene-butadiene rubber emulsion (SBR) accounting for 1% of the total solid weight of the negative electrode material was added. Then 40 g of oligomer 11 (PEG400, 0.10 mol) and 4.5 g of boric acid (0.073 mol) were added. After continued stirring, the mixture was filtered through a filter to obtain a slurry with a solid content of 45%. The slurry was then applied to both sides of a copper foil with a thickness of 6 μm using an extrusion coater. After baking and hot roller pressing, a negative electrode plate was obtained. The surface density of the single-sided coating of the negative electrode plate was 13 mg / cm 2 The single-side coating thickness is 79 μm, and the obtained negative electrode plate is placed in a vacuum oven at 120°C and dried for more than 24 hours.

[0389] 1.3 Preparation of diaphragm

[0390] Alumina powder (D50 of 1.5 μm) and sodium carboxymethyl cellulose (CMC) were mixed in a weight ratio of 99.25:0.75 and added to 1.5 kg of deionized water (DIW). The total weight of the alumina powder and sodium carboxymethyl cellulose (CMC) was 1 kg. The mixture was stirred and ground in a stirred grinder until the alumina particle size was less than 2 μm. The mixture was then transferred to a stirred tank. A styrene-butadiene rubber (SBR) emulsion with a solid content of 50% was added, accounting for 1.2% of the total solid weight of the diaphragm coating material. 40 g of oligomer 10 (0.053 mol) and 6.5 g of boric acid (0.11 mol) were then added. After stirring, the mixture was filtered through a filter to obtain a slurry with a solid content of 10%. The slurry was then coated on one surface of a 9 μm thick polyethylene porous film (porosity 45%) by gravure printing. This step was repeated to apply the slurry to the other surface of the polyethylene porous film. After drying, a composite porous membrane with a single-side inorganic coating thickness of 3 μm and a total thickness of 15 μm was obtained. The obtained membrane was dried in a vacuum oven at 80° C. for more than 48 hours.

[0391] 1.4 Preparation of dry cells

[0392] The positive plate, the negative plate, and the separator are cut into a certain shape, wherein the size of the active material area on the positive plate is 48 mm × 44 mm, the size of the active material area on the negative plate is 52 mm × 46 mm, and the size of the separator is 56 mm × 50 mm, and a current collector lead-out portion is left on each of the positive plate and the negative plate; then, they are stacked layer by layer in the order of negative plate, separator, positive plate, separator, negative plate, ..., for a total of 18 positive plates and 19 negative plates, with the outermost layer being the negative plate; then, the current collector lead-out portions of the positive plates are welded together with an ultrasonic welder, and the positive tabs are welded on; the current collector lead-out portions of the negative plates are welded together with an ultrasonic welder, and the negative tabs are welded on, thereby obtaining a laminated body.

[0393] The above-mentioned laminated body is placed in a packaging bag made of two pieces of aluminum-plastic film after shelling, and the hot melt adhesive on the tab is welded to the packaging bag by hot melting. The tab is led out of the packaging bag, and an air bag and a liquid injection port are left on one side of the packaging bag to obtain a dry battery cell.

[0394] 1.5 Preparation of electrolyte

[0395] In a glove box with a dew point below -40°C, lithium hexafluorophosphate (LiPF6) was dissolved in a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) (the volume ratio of EC to EMC was 3:7) to prepare an electrolyte with a LiPF6 concentration of 1.2 mol / L. Then, 1.5% of vinylene carbonate (VC) and 1% of 1,3-propane sultone (1,3-PS) were added to the electrolyte to obtain the required electrolyte.

[0396] 1.6 Preparation of batteries

[0397] In a glove box maintained at a dew point below -40°C, the electrolyte was injected into the dry cell through the injection port. After 24 hours of stagnation, the injection port outside the airbag was sealed using a vacuum heat sealer, and the gas in the cell was simultaneously extracted to complete the battery. The weight of the unformed cell was weighed and the weight of the dry cell was subtracted to obtain the weight of the injected electrolyte.

[0398] 1.7 Battery Formation

[0399] The battery cell is formed using a charging and discharging device. First, it is charged to 3.6V at a constant current of 0.05C. Then, it is sealed by vacuum exhausting with a vacuum heat sealer and the airbag is cut off. Then, it is charged to 4.2V at a constant current of 0.2C. Then, it is charged at a constant voltage until the current drops to 0.05C. Then, it is discharged to 3.0V at a constant current of 0.2C. Thus, a formed battery cell is obtained, which is the gel electrolyte lithium ion battery of the present invention.

[0400] 2. Battery testing

[0401] 2.1 First discharge capacity test

[0402] At room temperature, the formed batteries were charged at a constant current of 1C to 4.2V, then charged at a constant voltage until the current dropped to 0.05C. They were then discharged at a constant current of 1C to 3.0V to obtain the initial discharge capacity (Ah). Some batteries were then subjected to high-temperature storage testing, while others were subjected to charge-discharge cycle testing.

[0403] 2.2 High temperature storage test

[0404] The battery was charged at room temperature at a constant current of 1C to 4.2V, and then charged at a constant voltage until the current dropped to 0.05C. The battery was then transferred to a 60°C oven and stored for 7 days. The thickness of the test battery was taken out and the thickness expansion rate was calculated by comparing it with the thickness before high-temperature storage, that is, thickness expansion rate = (battery thickness after high-temperature storage - battery thickness before high-temperature storage) / battery thickness before high-temperature storage * 100%;

[0405] After the battery cools to room temperature, discharge it at a constant current of 1C to 3.0V. The obtained discharge capacity is compared with the discharge capacity before high-temperature storage to calculate the capacity retention rate, that is, capacity retention rate = discharge capacity after high-temperature storage / discharge capacity before high-temperature storage * 100%;

[0406] The battery was then charged to 4.2V at a constant current of 1C, then charged at a constant voltage until the current dropped to 0.05C, and then discharged to 3.0V at a constant current of 1C. The resulting discharge capacity was compared with the discharge capacity before high-temperature storage to obtain the capacity recovery rate, i.e., capacity recovery rate = discharge capacity after high-temperature storage after charging and discharging again / discharge capacity before high-temperature storage * 100%.

[0407] 2.3 Charge and discharge cycle test

[0408] At room temperature, the battery was charged at a constant current of 1C to 4.2V, then charged at a constant voltage until the current dropped to 0.05C, and then discharged at a constant current of 1C to 3.0V. This cycle was repeated for 1000 cycles, and the discharge capacity retention rate was calculated by comparing the last discharge capacity with the first discharge capacity.

[0409] 2.4 Acupuncture test

[0410] The battery puncture safety test was conducted in accordance with GB / T 31485-2015. A steel needle with a diameter of 8 mm was inserted into the battery at a speed of 25 mm / s perpendicular to the plate and remained there for 1 hour.

[0411] The above test results are shown in Table 2.

[0412] Example 2

[0413] The following steps were the same as in Example 1, except that 30 g of oligomer 7 (0.006 mol) and 2.79 g of boric acid (0.045 mol) were added during the production of the positive electrode plate, 50 g of oligomer 12 (PEG1000, 0.05 mol) and 2 g of boric acid (0.032 mol) were added during the production of the negative electrode plate, and 80 g of oligomer 10 (0.105 mol) and 26.3 g of boric acid (0.426 mol) were added during the production of the diaphragm.

[0414] The battery was tested according to the test method of Example 1, and the test results are shown in Table 2.

[0415] Example 3

[0416] The preparation process was the same as in Example 1, except that 30 g of oligomer 3 (0.011 mol) and 4 g of phenylboric acid (0.033 mol) were added during the production of the positive electrode plate, 20 g of oligomer 13 (PPG2000, 0.01 mol) and 0.41 g of boric acid (0.0067 mol) were added during the production of the negative electrode plate, and oligomer 10 and boric acid were not added during the production of the diaphragm.

[0417] The battery was tested according to the test method of Example 1, and the test results are shown in Table 2.

[0418] Example 4

[0419] The preparation process was the same as in Example 1, except that 50 g of oligomer 6 (0.008 mol) and 14.63 g of 1,4-phenylenediboronic acid (0.089 mol) were added during the production of the positive electrode plate, 50 g of oligomer 12 (PEG1000, 0.05 mol) and 2 g of boric acid (0.032 mol) were added during the production of the negative electrode plate, and oligomer 10 and boric acid were not added during the production of the diaphragm.

[0420] The battery was tested according to the test method of Example 1, and the test results are shown in Table 2.

[0421] Example 5

[0422] The process was the same as in Example 1 except that 25 g of oligomer 4 (0.033 mol) and 2.75 g of boric acid (0.044 mol) were added during the production of the positive electrode plate, oligomer 11 and boric acid were not added during the production of the negative electrode plate, and 100 g of oligomer 11 (PEG400, 0.25 mol) and 11.25 g of boric acid (0.183 mol) were added during the production of the diaphragm.

[0423] The battery was tested according to the test method of Example 1, and the test results are shown in Table 2.

[0424] Example 6

[0425] The process was the same as in Example 1, except that 50 g of oligomer 5 (0.016 mol) and 7.86 g of 1,4-phenylenediboronic acid (0.047 mol) were added during the production of the positive electrode plate, oligomer 11 and boric acid were not added during the production of the negative electrode plate, and 50 g of oligomer 9 (0.077 mol) and 6.43 g of 1,4-phenylenediboronic acid (0.039 mol) were added during the production of the separator.

[0426] The battery was tested according to the test method of Example 1, and the test results are shown in Table 2.

[0427] Example 7

[0428] The process was the same as in Example 1, except that 80 g of oligomer 9 (0.124 mol) and 10.3 g of 1,4-phenylenediboronic acid (0.062 mol) were added during the production of the negative electrode plate, 50 g of oligomer 9 (0.078 mol) and 6.43 g of 1,4-phenylenediboronic acid (0.039 mol) were added during the production of the separator, and oligomer 1 and boric acid were not added during the production of the positive electrode plate.

[0429] The battery was tested according to the test method of Example 1, and the test results are shown in Table 2.

[0430] Example 8

[0431] The same procedures as in Example 1 were employed except that 50 g of oligomer 12 (PEG1000, 0.05 mol) and 2 g of boric acid (0.032 mol) were added during the production of the negative electrode plate, 50 g of oligomer 8 (0.02 mol) and 10 g of boric acid (0.161 mol) were added during the production of the diaphragm, and oligomer 1 and boric acid were not added during the production of the positive electrode plate.

[0432] The battery was tested according to the test method of Example 1, and the test results are shown in Table 2.

[0433] Example 9

[0434] The process was the same as in Example 1 except that 20 g of oligomer 14 (PPG4000, 0.005 mol) and 0.18 g of boric acid (0.003 mol) were added during the production of the positive electrode plate, oligomer 11 and boric acid were not added during the production of the negative electrode plate, and oligomer 10 and boric acid were not added during the production of the separator.

[0435] The battery was tested according to the test method of Example 1, and the test results are shown in Table 2.

[0436] Example 10

[0437] The process was the same as in Example 1 except that 80 g of oligomer 8 (0.032 mol) and 16 g of boric acid (0.26 mol) were added during the production of the negative electrode plate, oligomer 1 and boric acid were not added during the production of the positive electrode plate, and oligomer 10 and boric acid were not added during the production of the separator.

[0438] The battery was tested according to the test method of Example 1, and the test results are shown in Table 2.

[0439] Example 11

[0440] The preparation process was the same as that of Example 1, except that 50 g of oligomer 9 (0.077 mol) and 6.43 g of 1,4-phenylenediboronic acid (0.039 mol) were added during the preparation of the separator, oligomer 1 and boric acid were not added during the preparation of the positive electrode plate, and oligomer 11 and boric acid were not added during the preparation of the negative electrode plate.

[0441] The battery was tested according to the test method of Example 1, and the test results are shown in Table 2.

[0442] Example 12

[0443] The preparation process was the same as in Example 1, except that 50 g of oligomer 9 (0.077 mol) and 5.5 g of 2-fluoro-3-pyridineboric acid (0.039 mol) were added during the diaphragm preparation process, oligomer 1 and boric acid were not added during the positive plate preparation process, and oligomer 11 and boric acid were not added during the negative plate preparation process.

[0444] The battery was tested according to the test method of Example 1, and the test results are shown in Table 2.

[0445] Example 13

[0446] The process was the same as in Example 1 except that 80 g of oligomer 8 (0.032 mol) and 27 g of 1,3,5-benzenetriboric acid (0.13 mol) were added during the production of the negative electrode plate, oligomer 1 and boric acid were not added during the production of the positive electrode plate, and oligomer 10 and boric acid were not added during the production of the separator.

[0447] The battery was tested according to the test method of Example 1, and the test results are shown in Table 2.

[0448] Comparative Example 1

[0449] The process is the same as that of Example 1 except that oligomer 1 and boric acid are not added during the production of the positive electrode plate, oligomer 11 and boric acid are not added during the production of the negative electrode plate, and oligomer 10 and boric acid are not added during the production of the separator.

[0450] The battery was tested according to the test method of Example 1, and the test results are shown in Table 2.

[0451] Comparative Example 2

[0452] The process was the same as that of Example 9 except that 50 g of oligomer 15 (PEG50000, 0.001 mol) and 0.03 g of boric acid (0.0005 mol) were added during the preparation of the positive electrode plate.

[0453] The battery was tested according to the test method of Example 1, and the test results are shown in Table 2.

[0454] Comparative Example 3

[0455] The process was the same as that of Example 10 except that 20 g of oligomer 16 (TEG, 0.133 mol) and 5.5 g of boric acid (0.089 mol) were added during the preparation of the negative electrode plate.

[0456] The battery was tested according to the test method of Example 1, and the test results are shown in Table 2.

[0457] Comparative Example 4

[0458] The process was the same as that of Example 1 except that 120 g of oligomer 14 (0.03 mol) and 12 g of boric acid (0.02 mol) were added during the production of the positive electrode plate.

[0459] The battery was tested according to the test method of Example 1, and the test results are shown in Table 2.

[0460] Comparative Example 5

[0461] The process was the same as that of Example 1 except that 1 g of oligomer 9 (0.0016 mol) and 0.13 g of 1,4-phenylenediboronic acid (0.0008 mol) were added during the preparation of the separator.

[0462] The battery was tested according to the test method of Example 1, and the test results are shown in Table 2.

[0463] Table 1 Basic parameters of polymers with boron cross-linked structures Note: The cross-linked polymer of Preparation Example 15 dissolved during the test.

[0464] Table 2 Battery performance test results

[0465] As shown in Table 1, the oligomers used in Preparation Examples 1-14 have molecular weights ranging from 400 to 19,200 and all contain multiple functional groups reactive with boric acid. These oligomers undergo esterification with boric acid or phenylboronic acid to form boron-crosslinked polymers. At 60°C, the boron-crosslinked polymers exhibit swelling degrees in the electrolyte of 59-6,700%, all exceeding 50%, and swelling loss rates of less than 5%. The oligomers used in Preparation Examples 15 and 16 have molecular weights of 50,000 and 150, respectively, and both contain only two hydroxyl groups reactive with boric acid. The swelling loss rate of the boron-crosslinked polymer in Preparation Example 15 reaches 92%, indicating that the polymer is substantially soluble in the electrolyte. The boron-crosslinked polymer in Preparation Example 16 exhibits a swelling degree of only 17%, and its low liquid absorption rate leads to poor ionic conductivity.

[0466] As can be seen from Table 2, the lithium ion batteries obtained by adding the oligomer of the present invention and boric acid to the coating material of the electrode or separator in Examples 1-13 have a high-temperature storage thickness expansion rate of 2.3-3.3%, a high-temperature storage capacity retention rate of 89-93%, a high-temperature storage capacity recovery rate of 93-97%, and a room-temperature cycle capacity retention rate of 88-92% after 1000 cycles. The needle penetration test results show that none of the batteries will catch fire or explode. In Comparative Example 1, neither the oligomer nor boric acid of the present invention was added to the electrode or the diaphragm. Its various high-temperature storage properties were worse than those of Example 1, and a fire occurred in the needle penetration test. In Comparative Example 2, oligomer 15 was added to the positive electrode. The polymer with a boron cross-linked structure produced after the reaction swelled too much and even dissolved in the electrolyte. Its various high-temperature storage properties were worse than those of Example 9, and the capacity retention during the cycle was less than 50%. A fire occurred in the needle penetration test. In Comparative Example 3, oligomer 16 was added to the negative electrode. The polymer with a boron cross-linked structure produced after the reaction swelled too little. Its various high-temperature storage properties were significantly worse than those of Example 10, and a fire occurred in the needle penetration test. In Comparative Example 4, more than 10% of oligomer and boric acid were added to the electrode. Although the battery did not catch fire or explode in the needle penetration test, the capacity retention during the cycle was less than 50%. In Comparative Example 5, 1‰ of oligomer and boric acid were added to the diaphragm. The electrochemical performance and needle penetration safety of the battery were not significantly different from those of Comparative Example 1.

[0467] Therefore, the high-temperature storage performance and safety of the lithium-ion battery containing the polymer having a boron cross-linked structure of the present invention in the electrode coating material or the diaphragm coating material are significantly improved.

[0468] In summary, the present invention adds a polymer containing active hydrogen functional groups and a boric acid compound to the positive electrode, negative electrode or separator, and forms a polymer with a cross-linked structure through an esterification cross-linking reaction. After contacting with the electrolyte, the polymer can absorb the electrolyte and swell to form a gel electrolyte. The traditional production process of lithium-ion batteries can be used, avoiding the problems of complicated process or unstable electrolyte and difficulty in wetting the electrodes caused by adding gel polymers or their precursors to the electrolyte in the prior art, and can meet the needs of high-energy density batteries; at the same time, the use of gel electrolyte instead of liquid electrolyte can reduce the leakage of electrolyte and volatilization of solvent and reduce the contact between electrolyte and the surface of active material, thereby improving the high-temperature cycle performance and safety performance of lithium batteries, extending the service life of lithium batteries, and reducing the risk of fire and explosion of lithium batteries, and has great application prospects.

[0469] Although the present application discloses the preferred embodiments as above, it is not intended to limit the claims. Any person skilled in the art can make a number of possible changes and modifications without departing from the concept of the present application. Therefore, the scope of protection of the present application shall be based on the scope defined by the claims of the present application. The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any modification, equivalent replacement and improvement made within the spirit and principle of the present invention shall be included in the scope of protection of the present invention.

Claims

1. A gel electrolyte lithium ion battery, characterized in that: The invention comprises a positive electrode, a negative electrode, a separator and an electrolyte, wherein at least one of the positive electrode, the negative electrode or the separator comprises a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3 and 4, Wherein, R1 is selected from one of hydroxyl, alkyl, aryl or heteroaryl, X1, X2, X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or an alkyl.

2. The gel electrolyte lithium ion battery according to claim 1, characterized in that: The invention comprises a positive electrode, a negative electrode, a separator and an electrolyte, wherein at least one of the positive electrode, the negative electrode or the separator comprises a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3 and 4, Wherein R1 is selected from one of hydroxyl, alkyl or phenyl, X1, X2, X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or an alkyl.

3. The gel electrolyte lithium ion battery according to claim 1 or 2, characterized in that: The invention comprises a positive electrode, a negative electrode, a separator and an electrolyte, wherein when X1, X2 and X3 are each independently selected from O, the group containing O is selected from: When X1, X2, and X3 are each independently selected from NR2, the group containing NR2 is selected from Wherein, when the group containing O is selected from When , O is directly connected to B, and C is directly connected to the polymer chain; When the group containing O is selected from When , O is directly connected to B, and S is directly connected to the polymer chain; When the group containing NR2 is selected from When N is directly connected to B, C is directly connected to the polymer chain.

4. The gel electrolyte lithium ion battery according to any one of claims 1 to 3, characterized in that: The polymer having a boron cross-linked structure is obtained by reacting a boric acid compound with a polymer containing an active hydrogen functional group; Preferably, the boric acid compound includes one or more of boric acid, phenylboric acid, phenyldiboric acid, 1,3,5-benzenetriboric acid, alkylboric acid, naphthaleneboric acid and heteroarylboric acid; preferably, the polymer containing active hydrogen functional groups includes one or more of hydroxyl-containing polymers, carboxyl-containing polymers, sulfonic acid-containing polymers, sulfate-containing polymers, phosphoric acid-containing polymers, amine-containing polymers and substituted amine-containing polymers.

5. The gel electrolyte lithium ion battery according to claim 4, characterized in that: The boric acid compound includes one or more of boric acid, phenylboric acid and alkylboric acid.

6. The gel electrolyte lithium ion battery according to claim 4, characterized in that: The polymer containing active hydrogen functional groups includes one or more of polyolefin containing active hydrogen functional groups, polyether containing active hydrogen functional groups, polyester containing active hydrogen functional groups, polyamide containing active hydrogen functional groups and polycarbonate containing active hydrogen functional groups.

7. The gel electrolyte lithium ion battery according to any one of claims 1 to 6, characterized in that: At 25-60° C., the swelling degree of the polymer having a boron cross-linked structure in the electrolyte is greater than 50%, preferably 50-10000%; preferably, the swelling loss rate of the polymer having a boron cross-linked structure in the electrolyte is less than 5%.

8. The gel electrolyte lithium ion battery according to any one of claims 1 to 7, characterized in that: The positive electrode comprises a current collector and a positive electrode coating material coated on the current collector; preferably, the positive electrode coating material comprises a positive electrode active material and the polymer having a boron cross-linked structure; And / or, the negative electrode comprises a current collector and a negative electrode coating material coated on the current collector; preferably, the negative electrode coating material comprises a negative electrode active material and the polymer having a boron cross-linked structure; And / or, the separator comprises a polymer porous membrane and a separator coating material coated on the polymer porous membrane; preferably, the separator coating material comprises inorganic particles and a polymer having a boron cross-linked structure.

9. The gel electrolyte lithium ion battery according to any one of claims 1 to 8, characterized in that: The electrolyte comprises an organic solvent and a lithium salt; preferably, the organic solvent is selected from one or more of ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate and methyl propyl carbonate; More preferably, the lithium salt is selected from one or more of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium bis(trifluoromethylsulfonyl)imide and lithium bis(fluorosulfonyl)imide, preferably lithium hexafluorophosphate.

10. The gel electrolyte lithium ion battery according to claim 9, characterized in that: The electrolyte further comprises one or more of unsaturated cyclic carbonate, fluorinated cyclic carbonate, cyclic sultone and cyclic sulfate; Preferably, the unsaturated cyclic carbonate is selected from vinylene carbonate and / or vinyl ethylene carbonate, and / or the fluorinated cyclic carbonate is selected from at least one of fluoroethylene carbonate, trifluoromethylethylene carbonate or bisfluoroethylene carbonate, and / or the cyclic sultone is at least one selected from 1,3-propane sultone, 1,4-butane sultone and propenyl-1,3-sultone, And / or the cyclic sulfate is selected from at least one of vinyl sulfate, propylene sulfate and 4-methylvinyl sulfate.

11. The method for preparing a gel electrolyte lithium ion battery according to any one of claims 1 to 10, characterized in that: The method comprises the following steps: forming a battery core with a positive electrode, a negative electrode and a separator, placing the battery core in a battery shell, injecting an electrolyte to obtain a semi-finished lithium ion battery, forming and exhausting the semi-finished lithium ion battery, and sealing the injection port of the battery shell to obtain a gel electrolyte lithium ion battery; Wherein, at least one of the positive electrode, negative electrode or separator is prepared according to the following method: (1) The positive electrode is prepared by the following steps: mixing a boric acid compound and a polymer containing an active hydrogen functional group with a positive electrode slurry, then coating the slurry on a current collector, and then drying to obtain the positive electrode; (2) The negative electrode is prepared by the following steps: mixing a boric acid compound and a polymer containing an active hydrogen functional group with a negative electrode slurry, then coating the slurry on a current collector, and then drying to obtain the negative electrode. pole; (3) The diaphragm is prepared by the following steps: mixing a boric acid compound and a polymer containing an active hydrogen functional group with a diaphragm slurry, then coating the slurry on a polymer porous membrane, and then drying to obtain the diaphragm; Preferably, the drying temperature is 60-120°C; More preferably, based on 100% of the total weight of the positive electrode slurry, the weight percentage of the sum of the weight of the boric acid compound and the polymer containing active hydrogen functional groups is 1-10%; and / or, Based on the total weight of the negative electrode slurry being 100%, the sum of the weights of the boric acid compound and the polymer containing active hydrogen functional groups is 1-10% by weight; and / or, Based on the total weight of the diaphragm slurry being 100%, the weight percentage of the sum of the weight of the boric acid compound and the polymer containing active hydrogen functional groups is 1-50%.

12. An electrode for a lithium ion battery, characterized in that: It includes a current collector and an electrode material coated on the current collector, wherein the electrode material contains a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3 and 4: Wherein, R1 is selected from one of hydroxyl, alkyl, aryl or heteroaryl, X1, X2, X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or an alkyl.

13. The lithium ion battery electrode according to claim 12, characterized in that: It includes a current collector and an electrode material coated on the current collector, wherein the electrode material contains a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3 and 4: Wherein R1 is selected from one of hydroxyl, alkyl or phenyl, X1, X2, X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or an alkyl; Preferably, the electrode is a positive electrode or a negative electrode.

14. The lithium ion battery electrode according to claim 12 or 13, characterized in that: When X1, X2, and X3 are each independently selected from O, the group containing O is selected from: When X1, X2, and X3 are each independently selected from NR2, the group containing NR2 is selected from Wherein, when the group containing O is selected from When , O is directly connected to B, and C is directly connected to the polymer chain; When the group containing O is selected from When , O is directly connected to B, and S is directly connected to the polymer chain; When the group containing NR2 is selected from When N is directly connected to B, C is directly connected to the polymer chain.

15. The method for preparing an electrode for a lithium ion battery according to any one of claims 12 to 14, characterized in that: The method comprises the following steps: mixing a boric acid compound and a polymer containing an active hydrogen functional group with an electrode slurry, and coating and drying the mixture to obtain the lithium ion battery electrode; Preferably, the drying temperature is 60-120°C; More preferably, based on 100% of the total weight of the electrode slurry, the weight percentage of the sum of the weight of the boric acid compound and the polymer containing active hydrogen functional groups is 1-10%.

16. A separator for a lithium ion battery, characterized in that: The invention comprises a polymer porous membrane and a diaphragm coating material coated on the polymer porous membrane, wherein the diaphragm coating material contains a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3 and 4, Wherein R1 is selected from one of hydroxyl, alkyl, aryl or heteroaryl groups, X1, X2, X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or an alkyl group.

17. The lithium ion battery separator according to claim 16, characterized in that It includes a polymer porous membrane and a diaphragm coating material coated on the polymer porous membrane, wherein the diaphragm coating material contains a polymer having a boron cross-linked structure, and the boron cross-linked structure of the polymer is one or more of the following formulas 1, 2, 3 and 4: Wherein R1 is selected from one of hydroxyl, alkyl or phenyl, X1, X2, X3 are each independently selected from one of O and NR2, wherein R2 is a hydrogen atom or an alkyl; Preferably, the polymer porous membrane is a polyolefin microporous membrane or a non-woven fabric.

18. The separator of the lithium ion battery according to claim 16 or 17, characterized in that: When X1, X2, and X3 are each independently selected from O, the group containing O is selected from: When X1, X2, and X3 are each independently selected from NR2, the group containing NR2 is selected from Wherein, when the group containing O is selected from When , O is directly connected to B, and C is directly connected to the polymer chain; When the group containing O is selected from When , O is directly connected to B, and S is directly connected to the polymer chain; When the group containing NR2 is selected from When N is directly connected to B, C is directly connected to the polymer chain.

19. The method for preparing a lithium ion battery separator according to any one of claims 16 to 18, characterized in that: The method comprises the following steps: mixing a boric acid compound and a polymer containing an active hydrogen functional group with a diaphragm slurry, coating and drying to obtain the diaphragm of the lithium ion battery; Preferably, the drying temperature is 60-120°C; Based on the total weight of the diaphragm slurry being 100%, the weight percentage of the sum of the weight of the boric acid compound and the polymer containing active hydrogen functional groups is 1-50%.

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