CN114940762B

CN114940762B - Polymer, preparation method thereof, polymer electrolyte and lithium ion battery

Info

Publication number: CN114940762B
Application number: CN202210550969.0A
Authority: CN
Inventors: 李俊焕; 徐耿标; 韩宜林; 李庆; 杨成林; 郭俊吉; 徐扬海; 李子坤; 任建国; 黄友元; 贺雪琴
Original assignee: Shenzhen Beiteri New Energy Technology Research Institute Co ltd
Current assignee: Shenzhen Beiteri New Energy Technology Research Institute Co ltd
Priority date: 2022-05-18
Filing date: 2022-05-18
Publication date: 2023-06-06
Anticipated expiration: 2042-05-18
Also published as: CN114940762A

Abstract

The application relates to a polymer and a preparation method thereof, a polymer electrolyte and a lithium ion battery, wherein end capping groups of the polymer comprise pyridine groups and epoxy groups, and the existence of the pyridine groups and the epoxy groups can improve the connection action strength of polymer molecular chains and electrode active substances. The polymer, the preparation method thereof, the polymer electrolyte and the lithium ion battery improve the bonding capacity of the polymer electrolyte and the adhesive force of the polymer electrolyte to the pole piece.

Description

Polymer, preparation method thereof, polymer electrolyte and lithium ion battery

Technical Field

The application relates to the technical field of solid electrolytes, in particular to a polymer and a preparation method thereof, a polymer electrolyte and a lithium ion battery.

Background

The lithium ion secondary battery has the advantages of high energy density, long cycle life, no memory effect and the like, has been developed in a rapid manner in recent decades, and is widely applied to the fields of small energy storage devices, electric automobiles, smart grids and the like. However, lithium ion batteries are commonly used as organic small molecule liquid electrolytes, and the lithium ion battery liquid electrolytes generally have safety problems such as lithium dendrite growth, electrolyte leakage, volatilization and the like.

Solid polymer electrolytes such as polyethylene oxide PEO are brittle and difficult to withstand internal and external strains such as bending, stretching and shearing. Solid state electrolytes are considered to be one of the most promising materials for lithium battery applications, and while inorganic ceramic electrolytes have excellent ionic conductivity, lack of flexibility and fragility limit their practical use. The polyoxyethylene-based solid polymer electrolyte has the advantages of easy film formation, good chemical stability and the like, however, the high crystallinity of polyoxyethylene limits the movement of polymer chains and prevents the rapid transmission of lithium ions, so that the ion conductivity at room temperature is generally lower.

During the use of lithium batteries, it is always unavoidable to suffer from various deformations and local stresses, severely limiting the life and reliability of the battery, eventually leading to failure of the battery system. The existing nonaqueous polymer gel electrolyte does not have enough elasticity and self-repairing performance, so that the problems of short circuit, breakage and the like of the electrolyte in the production, transportation and use of a battery are easily caused, and good contact of electrolyte interfaces is difficult to ensure in the circulating process. In the battery cycle process, the pole piece loaded with the active substance expands and contracts in the charge and discharge process, and repeatedly changes back and forth, so that the interface between the polymer electrolyte and the pole piece is easily separated.

Disclosure of Invention

In view of the above, the present application provides a polymer, a method for preparing the same, a polymer electrolyte, and a lithium ion battery, which can improve the adhesion of the polymer electrolyte and improve the adhesion of the polymer electrolyte to a pole piece.

In a first aspect, the present application provides a polymer comprising a polymer backbone and end capping groups, the end capping groups comprising pyridine groups and epoxy groups.

In the scheme, the end-capping group at the tail end of the polymer molecular chain contains an epoxy group and a pyridine group, wherein the epoxy group can perform strong complexation with Lewis acid such as hydrogen ions generated by lithium ions or lithium salt hydrolysis to promote ring opening reaction of the epoxy group, and react with active substances on a pole piece, such as a defect position on the surface of a positive electrode metal oxide, a structural defect position of negative electrode graphite, hydroxyl groups, carboxyl groups or amino groups on adhesive carboxymethyl cellulose and the like to form chemical bond connection, so that the connection strength of the polymer molecular chain and the electrode active substances is improved, and the cohesiveness of a polymer electrolyte is increased.

The pyridine group can increase the electron donating ability of the epoxy group, and improve the electrophilic effect of the epoxy group and Lewis acid, namely the ring-opening reaction activity of the epoxy group; and the pyridine group can be complexed with lithium salt, so that the self-catalytic effect is achieved, the ring-opening reaction of the epoxy groups on the molecular chain can be self-catalyzed, the reaction degree and the reaction rate are improved, and different epoxy groups are connected to form a high-bonding-strength adhesive. The nitrogen atom of the pyridine group has lone pair electrons and can also be used as an electron donor to carry out coordination complexing action with the exposed metal atom of the active metal oxide on the positive electrode, and the interaction between a polymer molecular chain and positive electrode metal ions or negative electrode metal lithium is formed through coordination bonds, so that the adhesion of the polymer electrolyte to the pole piece is improved.

In some possible embodiments, the molecular chain of the polymer is a triblock structure that is a flexible block with the end capping groups-a rigid block-a flexible block with the end capping groups.

In some possible embodiments, the flexible block is selected from the group consisting of polypropylene carbonate, polydimethylsiloxane, poly-n-butyl acrylate, polyethylene glycol.

In some possible embodiments, the rigid block is selected from the group consisting of a polyethylene block, a polypropylene block, a polyacetylene block, a parylene block, a polyphenylene ether.

In some possible embodiments, the polymer has the structural formula I as follows:

wherein R is ₁ Selected from halogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aryl;

R ₂ 、R ₃ each independently selected from the group consisting of substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aryl;

R ₄ selected from the group consisting of substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aryl;

n ₁ the value range is between 5 and 100; n is n ₂ The value range is between 10 and 200.

In some possible embodiments, the R ₂ And R is ₃ Each independently selected from substituted or unsubstituted alkyl, and R ₂ And R is ₃ The ring is formed by C-C connection.

In some possible embodiments, R ₄ Any one selected from ethenyl, propenyl, ethynyl, p-xylyl and phenyl ether.

In some possible embodiments, n ₁ The value range is 10 to 5Between 0; n is n ₂ The value range is 20 to 80.

In some possible embodiments, the polymer has the structural formula I-1 as follows:

wherein R is ₁ Selected from halogen, alkyl, alkenyl, alkynyl, aryl; n is n ₁ The value range is between 5 and 100; n is n ₂ The value range is between 10 and 200.

In a second aspect, the present application provides a polymer electrolyte comprising an electrolyte solution and a polymer as described in the first aspect.

In some possible embodiments, the molecular chain of the polymer is a triblock structure that is a flexible block with end capping groups-a rigid block-a flexible block with end capping groups; in the infrared absorption spectrum, the repeating units in the flexible block of the polymer are at a wavelength of 3000cm ^-1 ～600cm ^-1 The maximum light transmission peak intensity within the range is A ₁ The repeating units in the rigid block of the polymer are at a wavelength of 3000cm ^-1 ～600cm ^-1 The maximum light transmission peak intensity within the range is A ₂ The method comprises the steps of carrying out a first treatment on the surface of the The mass content of the electrolyte in the polymer electrolyte is W%, the peel strength of the polymer electrolyte is T mN/mm, and T satisfies the following relation:

A ₁ /A ₂ -10％≤T/1000W≤A ₁ /A ₂ +10％。

in some possible embodiments, the electrolyte includes an organic solvent and a lithium salt.

In some possible embodiments, the lithium salt comprises at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorophosphate, lithium bis (fluorosulfonyl) imide, lithium bis (oxalato) borate, or lithium difluorooxalato borate.

In some possible embodiments, the concentration of the lithium salt in the electrolyte is 0.5mol/L to 2mol/L.

In some possible embodiments, the organic solvent comprises a carbonate compound.

In some possible embodiments, the organic solvent comprises a carbonate compound including at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, methylethyl carbonate, ethylene carbonate, propylene carbonate, and butylene carbonate.

In some possible embodiments, the carbonate compound is 30% -95% by mass of the electrolyte.

In some possible embodiments, the polymer electrolyte is a polymer electrolyte membrane.

In some possible embodiments, the thickness of the polymer electrolyte membrane is 5 μm to 300 μm.

In some possible embodiments, the tensile strength of the polymer electrolyte membrane is 0.2Mpa to 20Mpa.

In some possible embodiments, the peel strength of the polymer electrolyte membrane is 150mN/mm to 600mN/mm.

In a third aspect, the present application provides a method of preparing a polymer, the method comprising:

heating a first mixed solution containing a blocking agent, an oxidant and a solvent to perform oxidation reaction to obtain a first compound, wherein the blocking agent contains a pyridine group and a cycloolefin group;

the first compound is mixed with at least one monomer or at least one rigid block molecular chain, and heated to perform polymerization reaction to obtain the polymer.

In some possible embodiments, the capping agent is selected from at least one of a bipyridyl cycloolefin, a bromo bipyridyl cyclohexene.

In some possible embodiments, the oxidizing agent is selected from at least one of m-chloroperoxybenzoic acid, hydrogen peroxide.

In some possible embodiments, the mass ratio of the capping agent to the oxidizing agent is 1: (0.1-2).

In some possible embodiments, the oxidation reaction temperature is 30 ℃ to 100 ℃ and the oxidation reaction time is 2 hours to 10 hours.

In some possible embodiments, the solvent is selected from at least one of dichloromethane, toluene, acetonitrile.

In some possible embodiments, the mass ratio of the first compound to the monomer is (2 to 100): 100.

in some possible embodiments, the monomer is selected from at least one of carbonate, acrylate, siloxane, ethylene glycol.

In some possible embodiments, the rigid block molecular chain is selected from at least one of polyethylene, parylene, polyphenylene oxide, polypropylene.

In some possible embodiments, the protective atmosphere comprises at least one of nitrogen, argon, neon, helium.

In some possible embodiments, the polymerization reaction is carried out under a protective atmosphere;

in some possible embodiments, the polymerization reaction temperature is 60 ℃ to 160 ℃ and the polymerization reaction time is 5 hours to 30 hours.

In some possible embodiments, the step of mixing the first compound with at least one monomer or at least one rigid block molecular chain comprises: the first compound, at least one monomer or at least one rigid block molecular chain, and an initiator are mixed.

In some possible embodiments, the initiator comprises at least one of a carbonate, a bisphenol compound, and a nitrile compound.

In some possible embodiments, the mass ratio of the initiator to the monomer is (2-30): 100.

in some possible embodiments, after mixing the first compound with at least one monomer and heating to effect polymerization, the method further comprises: and heating the polymer and the rigid block molecular chain to perform secondary polymerization reaction to obtain the polymer with the triblock structure.

In some possible embodiments, the mass ratio of the polymer to the rigid block molecular chain is (5-100): (10-200).

In some possible embodiments, the temperature of the secondary polymerization reaction is 80 ℃ to 160 ℃ and the time of the secondary polymerization reaction is 5 hours to 20 hours.

In a fourth aspect, the present application provides a lithium ion battery comprising the polymer electrolyte of the first aspect.

The technical scheme of the application has the following beneficial effects:

the end capping group at the tail end of the polymer molecular chain provided by the application contains an epoxy group and a pyridine group; the epoxy group can perform strong complexation with Lewis acid such as hydrogen ions generated by lithium ions or lithium salt hydrolysis, promotes ring opening reaction of the epoxy group, and reacts with active substances on a pole piece, such as a defect position on the surface of a positive electrode metal oxide, a structural defect position of negative electrode graphite, hydroxyl, carboxyl or amino on adhesive carboxymethyl cellulose and the like, so that chemical bond connection can be formed, the connection action strength of a polymer molecular chain and the electrode active substances is improved, and the cohesiveness of a polymer electrolyte is increased.

In some embodiments, the polymer fractionThe sub chain is of a three-block structure, the two ends of the molecular chain are random flexible blocks, and side chains R in the flexible blocks ₁ The disorder degree of the molecular chain can be increased, the polar groups in the flexible block are extremely easy to generate complexation or similar compatibility with lithium salt and carbonate organic solvents in the electrolyte, the dissolving and absorbing capacity of the flexible block to the lithium salt and the electrolyte is improved, the flexibility of the flexible block in the molecular chain can be improved, the movement resistance of the terminal groups positioned at the tail ends of the molecular chain is smaller, and the bonding capacity of the polymer molecular chain is improved.

The polymer film has the advantages that the rigid block is positioned in the middle of the molecular chain, the structure of the rigid block is regular, the molecular chains which are easily orderly arranged and piled up are low in reactivity, the pressure resistance and the safety performance of the polymer film can be improved, electrolyte cannot be embedded and permeated into the rigid block, the compatibility of an amorphous area formed by the rigid block and the flexible block is poor, the self-assembly of the triblock polymer molecular chains into a layered ordered structure can be promoted, and the concentration and the migration rate of lithium ions in the amorphous area are improved.

According to the preparation method of the polymer, the first compound containing the pyridine group and the epoxy group is prepared by using the end-capping agent and the oxidant, and the polymer is prepared by using the first compound and at least one monomer or at least one rigid block molecular chain, so that the tail end of the polymer molecular chain contains the epoxy group and the pyridine group, wherein the epoxy group can be subjected to strong complexation with Lewis acid to promote ring opening reaction of the epoxy group, and the epoxy group can react with active substances on a pole piece, such as the defect position of the surface of a positive electrode metal oxide, the structural defect position of negative electrode graphite, hydroxyl, carboxyl or amino on carboxymethyl cellulose serving as a binder and the like, so that chemical bond connection can be formed, the connection strength of the polymer molecular chain and the electrode active substances is improved, and the cohesiveness of a polymer electrolyte is increased. The pyridine group can increase the electron donating ability of the epoxy group and improve the ring-opening reaction activity of the epoxy group; and the pyridine group can be complexed with lithium salt, so that the self-catalytic effect is achieved, the ring-opening reaction of the epoxy groups on the molecular chain can be self-catalyzed, the reaction degree and the reaction rate are improved, and different epoxy groups are connected to form a high-bonding-strength adhesive. The nitrogen atom of the pyridine group has lone pair electrons and can also be used as an electron donor to carry out coordination complexing action with the exposed metal atom of the active metal oxide on the positive electrode, and the interaction between a polymer molecular chain and positive electrode metal ions or negative electrode metal lithium is formed through coordination bonds, so that the adhesion of the polymer electrolyte to the pole piece is improved.

Drawings

FIG. 1 is an infrared spectrum test chart of a polymer provided in example 1 of the present application;

FIG. 2 is a schematic diagram showing the results of the ionic conductivity test of the polymer electrolyte membrane according to example 1 of the present application;

FIG. 3 is a graph of test results of electrochemical stability windows of the polymer electrolyte membrane provided in example 1 of the present application;

fig. 4 is a schematic diagram showing the test results of the mechanical properties of the polymer electrolyte membrane provided in example 1 of the present application.

Detailed Description

The following description is of the preferred embodiments of the present invention, and it should be noted that, for those skilled in the art, it is possible to make several improvements and modifications without departing from the principle of the embodiments of the present invention, and these improvements and modifications are also considered as the protection scope of the embodiments of the present invention.

Embodiments provide a polymer comprising a polymer backbone and end capping groups, the end capping groups comprising pyridine groups and epoxy groups.

The pyridine group can increase the electron donating ability of the epoxy group, improve the electrophilic effect of the epoxy group and Lewis acid, promote the reactivity of the epoxy group with external active groups such as hydroxyl and carboxyl, namely improve the ring-opening reactivity of the epoxy group; and the pyridine group can be complexed with lithium salt, so that the self-catalytic effect is achieved, the ring-opening reaction of the epoxy groups on the molecular chain can be self-catalyzed, the reaction degree and the reaction rate are improved, and the epoxy groups on different molecular chains are connected to form a high-bonding-strength adhesive. The nitrogen atom of the pyridine group has a lone pair electron and a large pi ring, can also be used as an electron donor, and can generate electron cloud conjugation or metal coordination complexing action with the exposed metal atom of the active metal oxide on the positive electrode, and the interaction force of a polymer molecular chain and positive electrode metal ions or negative electrode metal lithium is formed through coordination bonds, so that the cohesiveness of the polymer electrolyte to the active substances on the pole piece is improved.

In some embodiments, the molecular chain of the polymer is a triblock structure that is a flexible block with the end capping groups-a rigid block-a flexible block with the end capping groups.

In the scheme, the two ends of the molecular chain are random flexible blocks, the molecular chain movement flexibility of the flexible blocks is high, the peristaltic swing degree of the tail end of the molecular chain can be improved, the contact reaction resistance between the tail end group and the active substance is further reduced, the movement resistance of the tail end group at the tail end of the molecular chain is smaller, meanwhile, the flexible blocks have good viscosity, a strong bonding effect can be generated with the surface of the active substance, and the bonding capability of the polymer molecular chain is improved; the side chains in the flexible block can increase the disorder degree of the molecular chains and improve the bonding capability of the polymer molecular chains.

The rigid block is positioned in the middle of the molecular chain, the structure of the rigid block is regular, the molecular chain which is easily orderly arranged and piled up is formed into a regular ordered region, electrolyte cannot be embedded and permeated into the rigid block, the compatibility of an amorphous region formed by the rigid block and the flexible block is poor, the self-assembly of the triblock polymer molecular chain into a layered ordered structure can be promoted, the concentration of lithium ions in the amorphous region is improved, and the adhesive force of the block polymer is further improved.

In some embodiments, the flexible block is selected from the group consisting of polypropylene carbonate, polydimethylsiloxane, poly-n-butyl acrylate, polyethylene glycol.

In some embodiments, the rigid block is selected from the group consisting of a polyethylene block, a polypropylene block, a polyacetylene block, a parylene block, a polyphenylene ether.

In some embodiments, the polymer has the structural formula shown in formula I below:

In some embodiments, the alkyl group may be a chain alkyl group, or may be a cyclic alkyl group, which may in turn be a straight chain alkyl group or a branched alkyl group, and the hydrogen located on the ring of the cyclic alkyl group may be further substituted with an alkyl group. The alkyl group may also be cycloalkyl, heteroalkyl, cycloheteroalkyl, heterocycloalkyl, alkylcarbonyl, cycloalkylcarbonyl, heteroalkylcarbonyl, cycloheteroalkylcarbonyl, heterocycloalkylcarbonyl, alkyl ester, cycloalkyl ester, heteroalkyl ester, cycloheteroalkyl ester, or heterocycloalkyl ester.

Preferably, R ₁ Selected from C1-C10 alkyl groups, which may be: methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, sec-butyl, tert-butyl, n-pentyl, isopentyl, and neoPentyl, hexyl, 2-methyl-pentyl, 3-methyl-pentyl, 1, 2-trimethyl-propyl, 3-dimethyl-butyl, heptyl, 2-heptyl, 3-heptyl, 2-methylhexyl, 3-methylhexyl, isoheptyl, octyl, nonyl, decyl, more preferably R ₁ Selected from substituted or unsubstituted C1-C6 alkyl groups.

Alkenyl groups may include cycloalkenyl, heteroalkenyl, cycloheteroalkenyl, heterocycloalkenyl, alkenylcarbonyl, cycloalkenylcarbonyl, heterocycloalkenylcarbonyl, alkenylester, cycloalkenyl, heteroalkenyl, cycloheteroalkinyl, heterocycloalkenyl ester; alkynyl groups may include cycloalkynyl, heteroalkynyl, heterocycloalkynyl; aryl groups may include aralkyl, heteroaryl, alkylsulfonyl, arylsulfonyl, heteroarylsulfonyl, heterocyclylsulfonyl.

In some embodiments, R ₂ And R is ₃ Each independently selected from substituted or unsubstituted alkyl, and R ₂ And R is ₃ The ring is formed by C-C connection.

In some embodiments, R ₂ And R is ₃ Six-membered rings, seven-membered rings, eight-membered rings, etc., are formed by C-C connection, without limitation. Illustratively, R is ₂ And R is ₃ The aliphatic six-membered ring is connected with the epoxy three-membered ring, the structure is stable, and simultaneously, the aliphatic six-membered ring can fix the two carbon atom space configuration of the epoxy three-membered ring, the ring tension of the epoxy three-membered ring is enhanced, the epoxy bond is fully exposed outside, the lone pair electrons on the oxygen atom are exposed outside, and the complexing reaction activity of the epoxy three-membered ring is improved.

n ₁ The value range is between 5 and 100; n is n ₁ Specifically, 5, 8, 10, 15, 20, 28, 30, 40, 50, 80, or 100 may be used, and other values within the above range are not limited thereto. Preferably n ₁ The value range is between 10 and 50.

n ₂ The value range is between 10 and 200; n is n ₂ Specifically, 10, 15, 20, 28, 30, 35, 40, 50, 65, 85, 100, 110, 130, 150, 170, or 200 may be used, and other values within the above range are not limited thereto. Preferably, the method comprises the steps of,n ₁ the value range is 20 to 80.

By controlling n as described above ₁ N is as follows ₂ The molecular chain arrangement structure can be controlled, so that the triblock polymer can comprehensively balance the advantages of each block, the strength of the rigid block and the flexibility of the flexible block are exerted, and further the conductivity and the mechanical property of the polymer electrolyte are considered.

In some embodiments, the flexible blocks on both sides of the polymer molecular chain are flexible chains in which the molecular chain is easily internally rotated and the spatial configuration is free to twist and random coils, and can be polypropylene carbonate, polydimethylsiloxane, poly-n-butyl acrylate, polyethylene glycol and the like.

In some embodiments, the flexible block is a polycarbonate block, specifically may be polypropylene carbonate, the carbonate group in the polycarbonate block is a polar group, the molecular bond angle is larger, the molecular group can be freely stretched, complexation or similar compatibility can be easily generated between the polycarbonate block and lithium salt and carbonate organic solvent in the electrolyte, the dissolving and absorbing capacity of the polycarbonate block to the lithium salt and the electrolyte is improved, the flexibility of the polycarbonate block in a molecular chain can be improved, the movement resistance of the terminal group at the terminal of the molecular chain is smaller, the adhesion capacity of the polymer molecular chain is improved, and the interface stability of the polymer electrolyte and the electrode pole piece is improved.

The polycarbonate blocks form a random region of the polymer, have larger solubility to lithium salt, have larger carbonate group contact constant and large intramolecular polarization, are favorable for complexing the flexible blocks with lithium ions, promote the dissolution and migration of the lithium salt and are favorable for improving the ion conductivity of the polymer electrolyte. Side chain R in a flexible block ₁ The disorder degree of the molecular chains can be increased, and the bonding capability of the polymer molecular chains can be improved.

In some embodiments, the rigid block positioned in the middle of the polymer molecular chain has a regular molecular chain structure, is easy to be orderly arranged and piled up to form a crystal structure, electrolyte and lithium salt are difficult to be embedded into the rigid block molecular chain, and the rigid block is used as a base layer for mechanically supporting the polymer molecular chain, so that the polymer electrolyte has higher conductivity and superior mechanical property.

In some embodiments, the rigid block may be a polyolefin block (e.g., a polyethylene block, a polypropylene block), a polyacetylene block, a parylene block, a polyphenylene ether block, or the like. Preferably, the rigid block is a polyolefin block, so that the reaction activity is low, and the pressure resistance and the safety performance of the polymer electrolyte can be improved; the crystal structure formed by closely stacking the polyolefin blocks makes the lithium salt and electrolyte difficult to participate in the arrangement of the molecular chains, and the molecular chain structure is not dissolved and destroyed, so that the rigid block can bear larger external mechanical force, and the mechanical strength of the polymer electrolyte is facilitated to be provided.

The embodiment of the application provides a polymer electrolyte, which comprises electrolyte and the polymer. The molecular chain of the polymer is a triblock structure, and the triblock structure is a flexible block with end sealing groups, namely a rigid block and a flexible block with end sealing groups.

As an alternative to the present application, in the infrared absorption spectrum, the repeating units in the flexible block of the polymer have a wavelength of 3000cm ^-1 ～600cm ^-1 The maximum light transmission peak intensity within the range is A ₁ The repeating units in the rigid block of the polymer are at a wavelength of 3000cm ^-1 ～600cm ^-1 The maximum light transmission peak intensity within the range is A ₂ The method comprises the steps of carrying out a first treatment on the surface of the The mass content of the electrolyte in the polymer electrolyte is W%, the peel strength of the polymer electrolyte is T mN/mm, and T satisfies the following relation:

A ₁ /A ₂ -10％≤T/1000W≤A ₁ /A ₂ +10％。

in some embodiments, A1 is the maximum light transmission peak intensity of the wavelength corresponding to the chemical bond vibration peak in the repeating unit structure in the infrared light absorption spectrum range of 3000-600cm < -1 >. The repeating units in the flexible block may be specifically polypropylene carbonate (maximum light transmission peak intensity A1 of 2842cm ^-1 ) Polydimethylsiloxane (maximum light transmittance peak intensity A1 of 1008cm ^-1 ) Poly (n-butyl acrylate) (maximum light transmission peak intensity) A1 is 1730cm ^-1 ) Polyethylene glycol (maximum light transmittance peak intensity A1 of 1060 cm) ^-1 )。

The peel strength T and the ratio of the rigid block to the flexible block on the polymer molecular chain have an association relation, the proper ratio of the rigid block to the flexible block can exert the bonding performance of the polymer molecular chain to the maximum extent, meanwhile, the bonding strength of the polymer electrolyte is related to the polymer content and electrolyte content of the electrolyte, and the electrolyte content is too high, so that the ionic conductivity of the polymer electrolyte is improved, but the bonding performance is not improved; if the electrolyte content is too low, the polymer electrolyte is too dry to exert the adhesive property of the polymer. By controlling the three components within the above-described relation, the adhesive property of the polymer electrolyte can be effectively exhibited.

In some embodiments, the polymer electrolyte comprises a polymer of formula I-1;

in the infrared absorption spectrum, the polymer electrolyte has a wavelength of 1700cm ^-1 ～1750cm ^-1 Carbonate groups in the corresponding polycarbonate blocks in the range, the light transmission peak intensity of the carbonate groups being A ₁ The polymer electrolyte has a wavelength of 2830cm ^-1 ～2880cm ^-1 Methylene in the corresponding polyethylene block in the range, the light transmission peak intensity of the methylene is A ₂ By controlling A ₁ /A ₂ The distribution density of the flexible block and the rigid block can be determined, and the chemical structure of the polymer molecular chain can be controlled, so that the polymer has better supporting strength and adhesion.

In some embodiments, the electrolyte includes an organic solvent and a lithium salt.

The organic solvent includes a carbonate compound including at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, methylethyl carbonate, ethylene carbonate, propylene carbonate, and butylene carbonate. It is understood that the carbonate compound has a carbonate group, and the polar groups (such as amino groups, hydroxyl groups, ester groups, etc.) contained in the polymer main chain have similar miscibility with the carbonate compound, so that the interaction between the organic solvent in the electrolyte and the molecular chain of the polymer can be improved, and the absorption capacity of the polymer to the organic solvent in the electrolyte can be further enhanced.

In some embodiments, the mass percentage of the carbonate compound in the electrolyte is 30% to 95%, specifically, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or 95%, etc., but may be other values within the above range, and the present invention is not limited thereto.

In some embodiments, the lithium salt comprises at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorophosphate, lithium bis (fluorosulfonyl) imide, lithium bis (oxalato) borate, or lithium difluorooxalato borate.

The lithium salt in the polymer electrolyte coordinates with polar groups on molecular chains, can participate in improving the polar degree of the molecular chains at two ends of the polymer, increases the dipole moment in the molecule, has larger difference with a rigid block in the middle, generates obvious incompatibility, and has incompatible molecular repulsive interaction to promote the spontaneous assembly of the molecular chains to form a layered structure, so that the molecular chains at two ends are distributed outside the polymer aggregate, and the aliphatic epoxy groups at the tail ends of the molecular chains are also exposed outside the aggregate, thereby improving the probability of interconnection with the outside, such as pole piece active matters and adjacent aggregate outsides, and further improving the adhesive force of the polymer electrolyte.

In some embodiments, the concentration of the lithium salt in the electrolyte is 0.5mol/L to 2mol/L, specifically, 0.5mol/L, 0.7mol/L, 0.9mol/L, 1.0mol/L, 1.2mol/L, 1.5mol/L, or 2.0mol/L, etc., but may be other values within the above range, and the present invention is not limited thereto.

In some embodiments, the polymer electrolyte has an ionic conductivity of 0.1X10 ^-4 S/cm to 20X 10 ^- ⁴ S/cm; specifically, it may be 1.0X10 ^-4 S/cm、1.5×10 ^-4 S/cm、1.8×10 ^-4 S/cm、2.0×10 ^-4 S/cm、3.0×10 ^- ⁴ S/cm、4.0×10 ^-4 S/cm、5.0×10 ^-4 S/cm、6.0×10 ^-4 S/cm、10×10 ^-4 S/cm、16×10 ^-4 S/cm、19×10 ^-4 S/cm or 20X 10 ^-4 S/cm, etc., may of course be other values within the above-mentioned range, and are not limited thereto. The ionic conductivity of the polymer electrolyte is less than 1.0X10 ^-4 S/cm, is unfavorable for improving the electrochemical performance of the lithium battery.

In some embodiments, the electrochemical stability window of the polymer electrolyte is 4V to 6V; specifically, the voltage may be 4.0V, 4.1V, 4.3V, 4.5V, 5.0V, 5.3V, 5.5V, 5.8V, 5.9V, 5.95V, or 6V, etc., but other values within the above range are also possible, and the present invention is not limited thereto. It can be understood that the electrochemical stability window of the polymer electrolyte membrane is up to more than 4V, has high voltage resistance, can be matched with high voltage electrode materials for use, and improves the power and energy density of the battery.

In some embodiments, the polymer electrolyte has an ion migration number of 0.2 to 0.7; specifically, it may be 0.2, 0.25, 0.32, 0.37, 0.43, 0.45, 0.46, 0.47, 049, 0.50, 0.55, 0.57, 0.6, 0.62, 0.65, 0.68 or 0.7, etc., but it may be any other value within the above range, and the present invention is not limited thereto. Controlling the ion transfer number of the polymer electrolyte within the above range can facilitate the formation of a continuous ion transfer channel of the polymer electrolyte, and can enhance the conduction of effective charges.

In some embodiments, the polymer electrolyte is a polymer electrolyte membrane having a thickness of 5 μm to 300 μm and a tensile strength of 0.2Mpa to 20Mpa.

In some embodiments, the thickness of the polymer electrolyte membrane may be 5 μm, 7 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 100 μm, 150 μm, 180 μm, 200 μm, 250 μm, 280 μm, 300 μm, or the like, although other values within the above range are also possible and are not limited thereto. Too thick a polymer electrolyte membrane may result in a large membrane resistance; the polymer electrolyte membrane is too thin and the membrane layer is easily broken.

In some embodiments, the tensile strength of the polymer electrolyte membrane may be 0.2Mpa, 0.5Mpa, 0.7Mpa, 1.2Mpa, 1.5Mpa, 1.7Mpa, 2.0Mpa, 4.0Mpa, 7Mpa, 8.5Mpa, 9Mpa, 10Mpa, 12Mpa, 15Mpa, 18Mpa, 20Mpa, etc., although other values within the above range are also possible, and are not limited thereto. The tensile strength of the polymer electrolyte membrane is in the range, so that the polymer electrolyte membrane has good mechanical properties, enough elasticity can effectively buffer the external force impact, the pole piece expansion and contraction and other strains of the battery in the electrochemical cycle process of the battery in use, transportation and production, the problems of interface falling, electrolyte layer stripping, breakage and other degradation battery performances caused by internal and external force are avoided, the possibility of short circuit of the lithium battery is reduced, and the stability of the solid battery is enhanced.

In some embodiments, the peel strength of the polymer electrolyte membrane is 150mN/mm to 600mN/mm. Specifically, 150mN/mm, 180mN/mm, 200mN/mm, 250mN/mm, 300mN/mm, 450mN/mm, 520mN/mm, 550mN/mm, 600mN/mm, or the like may be used, and other values within the above range are not limited thereto. The tensile strength of the polymer electrolyte membrane is in the above range, which is advantageous for the efficient exertion of the adhesive property of the polymer electrolyte membrane.

In a third aspect, embodiments herein provide a method of preparing a polymer, the method comprising the steps of:

step S10, heating a first mixed solution containing a blocking agent, an oxidant and a solvent to perform an oxidation reaction to obtain a first compound, wherein the blocking agent contains a pyridine group and a cycloolefin group;

step S20, mixing the first compound with at least one monomer or at least one rigid block molecular chain, and heating to perform polymerization reaction to obtain the polymer.

In the scheme, the first compound containing the pyridine group and the epoxy group is prepared by adopting the end-capping reagent and the oxidant, and the first compound is polymerized with at least one monomer or at least one rigid block molecular chain to obtain the polymer, so that the tail end of the polymer molecular chain contains the epoxy group and the pyridine group, wherein the epoxy group can have a strong complexation with Lewis acid to promote the ring-opening reaction of the epoxy group, and the epoxy group reacts with active substances on the pole piece, such as the defect position of the surface of the positive electrode metal oxide, the structural defect position of the negative electrode graphite, hydroxyl, carboxyl or amino on the adhesive carboxymethyl cellulose and the like, so that chemical bond connection can be formed, the connection strength of the polymer molecular chain and the electrode active substance is improved, and the cohesiveness of the polymer electrolyte is increased. The pyridine group can increase the electron donating ability of the epoxy group and improve the ring-opening reaction activity of the epoxy group; and the pyridine group can be complexed with lithium salt, so that the self-catalytic effect is achieved, the ring-opening reaction of the epoxy groups on the molecular chain can be self-catalyzed, the reaction degree and the reaction rate are improved, and different epoxy groups are connected to form a high-bonding-strength adhesive. The nitrogen atom of the pyridine group has lone pair electrons and can also be used as an electron donor to carry out coordination complexing action with the exposed metal atom of the active metal oxide on the positive electrode, and the interaction between a polymer molecular chain and positive electrode metal ions or negative electrode metal lithium is formed through coordination bonds, so that the adhesion of the polymer electrolyte to the pole piece is improved.

In this variant step S20, if the first compound is mixed with at least one monomer, the polymerization is carried out by heating, so that a polymer containing flexible blocks can be obtained; if the first compound is mixed with at least one molecular chain of a rigid block, the polymerization reaction is carried out by heating, and a polymer containing a rigid block can be obtained.

In some embodiments, the capping agent is selected from at least one of a bipyridyl cyclic olefin, a bromo bipyridyl cyclohexene;

in some embodiments, the oxidizing agent is selected from at least one of m-chloroperoxybenzoic acid, hydrogen peroxide;

in some embodiments, the mass ratio of the capping agent to the oxidizing agent is 1: (0.1-2), specifically, it may be 1:0.1, 1:0.2, 1:0.5, 1:0.7, 1:0.9, 1:1, 1:1.2, 1:1.5 or 1:2, etc., without limitation. The end-capping agent is capable of undergoing an oxidation reaction under the action of an oxidizing agent to produce an end-capping compound having a pyridine group and an epoxy group.

In some embodiments, the oxidation reaction temperature is 30 ℃ to 100 ℃ and the oxidation reaction time is 2 hours to 10 hours; the reaction temperature may be specifically 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃, or 100 ℃, and the reaction time may be specifically 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, or 10 hours, and the like, and the reaction temperature is not limited herein. The oxidation reaction temperature and time are controlled, so that the end-capped compound with pyridine groups and epoxy groups can be generated, and the reaction efficiency is improved.

In some embodiments, the solvent is selected from at least one of dichloromethane, toluene, acetonitrile.

In some embodiments, the mass ratio of the first compound to the monomer is (2 to 100): 100, which may specifically be 2:100, 5:100, 10:100, 20:100, 40:100, 50:100, 60:100, 70:100, 80:100, or 100:100, etc., are not limited herein.

In some embodiments, the monomer is selected from at least one of carbonate, alkenoate, heterocyclic ketone, siloxane, ethylene glycol; specifically, the carbonate may be propylene carbonate, the heterocyclic ketone may be 4-ethyldioxolane, the acrylate may be n-butyl acrylate, and the siloxane may be dimethylsiloxane.

In some embodiments, the rigid block molecular chain is selected from at least one of polyethylene, parylene, polyphenylene oxide, polypropylene.

In some embodiments, the first compound may also be reacted with a polymer prepared from the above monomers to provide a polymer, which may be a flexible block molecular chain. Illustratively, the polymer may be a hydroxyl-bearing polyethylene glycol, hydroxyl-bearing n-butyl polyacrylate, hydroxyl-bearing polydimethylsiloxane, hydroxyl-bearing polypropylene carbonate, and the like.

In some embodiments, the polymerization reaction is conducted under a protective atmosphere comprising at least one of nitrogen, argon, neon, helium;

in some embodiments, the polymerization reaction temperature is 60 ℃ to 160 ℃, the polymerization reaction time is 5h to 30h, specifically, 60 ℃, 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 140 ℃, 160 ℃, or the like, and the polymerization reaction time is 5h, 6h, 7h, 8h, 9h, 10h, 15h, 20h, 30h, or the like, without limitation.

In some embodiments, the step of mixing the first compound with at least one monomer or at least one rigid block molecular chain comprises: mixing the first compound, the monomer or the rigid block molecular chain, and an initiator;

in some embodiments, the initiator comprises at least one of a carbonate, a bisphenol, and a nitrile; the carbonate can be at least one of potassium bicarbonate and potassium carbonate, the bisphenol compound can be at least one of hydroquinone and resorcinol, and the nitrile compound can be at least one of acetonitrile and hexamethylene dinitrile.

In some embodiments, the mass ratio of the initiator to the monomer is (2-30): 100, which may specifically be 2:100, 5:100, 7:100, 9:100, 10:100, 15:100, 20:100, 25:100, or 30:100, etc., is not limited herein.

In some embodiments, step S20 is: the first compound is mixed with at least one monomer, and heated to perform polymerization reaction to obtain the polymer. After step S20, the method further comprises: and heating the polymer and the rigid block molecular chain to perform secondary polymerization reaction to obtain the polymer with the triblock structure.

In some embodiments, the mass ratio of the polymer to the rigid block molecular chain is (5-100): (10-200); specifically, it may be 5:10, 5:20, 5:30, 5:40, 5:50, 10:50, 50:100, 100:100, 100:200, etc., and may be adjusted according to the actual needs of the triblock polymer.

In some embodiments, the rigid block molecular chain may be polyethylene, parylene, polyphenylene oxide, polypropylene, or the like.

In some embodiments, the temperature of the secondary polymerization reaction is 80 ℃ to 160 ℃, the time of the secondary polymerization reaction is 5h to 20h, specifically, 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 140 ℃, 160 ℃ or the like, and the time of the secondary polymerization reaction is 5h, 6h, 7h, 8h, 9h, 10h, 15h, 20h or the like, without limitation.

In a fourth aspect, embodiments of the present application provide a method for preparing a polymer electrolyte, the method comprising the steps of:

Step S100, dissolving a polymer in an organic solvent, heating and stirring to dissolve the polymer, and obtaining a gel polymer;

step S200, coating and forming the gel polymer, and drying to obtain a polymer film;

step S300, immersing the polymer film in electrolyte to obtain a film-shaped polymer electrolyte, wherein the polymer electrolyte comprises a polymer shown in a formula I;

wherein R is ₁ Selected from substituted or unsubstituted alkyl, alkenyl, alkynyl, aryl, halogen;

R ₂ 、R ₃ each independently selected from the group consisting of substituted or unsubstituted hydrogen, alkyl, alkenyl, alkynyl, aryl, halogen; alternatively, R ₂ And R is ₃ Each independently selected from substituted or unsubstituted alkyl, and R ₂ And R is ₃ Forming a ring by C-C connection;

R ₄ selected from substituted or unsubstituted alkenyl, alkynyl, aryl;

And step S10, dissolving the polymer in an organic solvent, and heating and stirring to dissolve the polymer to obtain the gel polymer.

Specifically, the organic solvent includes at least one of acetonitrile, ethyl acetate, tetrahydrofuran, or methylene chloride, and the polymer is preferably a polymer having a triblock structure.

The temperature of the heating and stirring may be 30 to 70 ℃, specifically 30, 40, 45, 50, 55, 60, 65, or 70 ℃, or any other value within the above range, and the present invention is not limited thereto. The heating and stirring time is 1h to 4h, specifically, may be 1h or 2h, or the like, and may be any other value within the above range, which is not limited herein. The heating and stirring time is too short, which is unfavorable for forming a gel polymer which is uniformly mixed.

And step S20, coating and forming the gel polymer, and drying to obtain the polymer film.

In particular embodiments, the gel polymer may be coated on a polytetrafluoroethylene sheet, or on a polytetrafluoroethylene substrate.

The temperature of the drying treatment may be from 50 to 150 ℃, specifically 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃, 120 ℃, 150 ℃, or the like, but may be any other value within the above range, and the drying treatment is not limited thereto.

The drying time is 2h to 12h, specifically, may be 2h, 3h, 4h, 5h, 6h, 8h, 10h, or 12h, or the like, and may be any other value within the above range, which is not limited herein. It will be appreciated that by being sufficiently dry, the formation of a dry polymer film is facilitated.

And step S30, immersing the polymer film in electrolyte to obtain a film-shaped polymer electrolyte.

As an optional technical scheme of the application, the carbonate compound further comprises an electrolyte, and the electrolyte comprises an organic solvent and lithium salt.

The organic solvent comprises a carbonate compound, and the carbonate compound comprises at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, ethylene carbonate, propylene carbonate and butylene carbonate. It is understood that the carbonate compound has a carbonate group, and the polar group (e.g., carbonate group) contained in the flexible block of the polymer molecular chain has similar compatibility with the carbonate compound, so that the interaction between the organic solvent in the electrolyte and the polymer molecular chain can be improved, and the absorption capacity of the polymer to the organic solvent in the electrolyte can be further enhanced.

As an alternative embodiment of the present application, the mass percentage of the carbonate compound in the electrolyte is 30% to 95%, specifically, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75% or 95%, etc., but may be any other value within the above range, and the present invention is not limited thereto.

As an optional technical solution of the present application, the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorophosphate, lithium bis (fluorosulfonyl) imide, lithium bis (oxalato) borate, or lithium difluorooxalato borate.

As an alternative solution of the present application, the concentration of the lithium salt in the electrolyte may be 0.5mol/L to 2mol/L, specifically, 0.5mol/L, 0.7mol/L, 0.9mol/L, 1.0mol/L, 1.2mol/L, 1.5mol/L, or 2.0mol/L, or the like, and of course, other values within the above range may be also possible, which is not limited herein.

As an alternative technical scheme, the soaking time is 1h to 5h, specifically may be 1h, 2h, 3h, 4h or 5h, or the like, and of course may be other values within the above range, which is not limited herein.

In a fifth aspect, embodiments provide a lithium ion battery comprising a polymer electrolyte as described in the first aspect.

In the actual preparation process, the polymer film and the positive and negative electrode plates can be assembled into a battery in a lamination mode, and electrolyte containing lithium salt is injected into the battery to infiltrate and swell.

In some embodiments, the electrolyte is used in an amount of 10% to 90% of the total mass of the polymer electrolyte, specifically 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80% or 90%, etc., although other values within the above range are also possible. Too high an electrolyte content is beneficial to improving the ionic conductivity of the polymer electrolyte, but is not beneficial to improving the cohesiveness; if the electrolyte content is too low, the polymer electrolyte is too dry to exert the adhesive property of the polymer. Preferably, the electrolyte is used in an amount of 40-60% of the total mass of the polymer electrolyte, which is beneficial to the high-efficiency performance of the adhesive property of the polymer electrolyte.

In some embodiments, the positive active material in the positive electrode sheet may be lithium cobaltate, lithium iron phosphate, ternary material, etc., and the negative active material in the negative electrode sheet may be metallic lithium, graphite, silicon-based negative electrode, etc., without limitation.

The following examples are provided to further illustrate embodiments of the invention. The embodiments of the present invention are not limited to the following specific embodiments. The modification can be appropriately performed within the scope of the main claim.

Example 1

(1) About 25g of 3, 6-bipyridyl-1, 4-cyclohexadiene and 17g of m-chloroperoxybenzoic acid are respectively dissolved in 500mL of dichloromethane, heated and mixed uniformly at 50 ℃ and stirred for reaction for 4h. Filtering by a silica gel column, and performing rotary evaporation to obtain the compound A.

(2) Under the nitrogen atmosphere, the compound A is dissolved in 100g of carbonate monomer (propylene carbonate), 2g of potassium bicarbonate and 5g of hydroquinone are added, the reaction temperature is 150 ℃, the mixture is heated for 15 hours, the mixture is cooled to room temperature, anhydrous and anaerobic filtration is carried out to obtain yellow solution, 80g of polyethylene with carboxyl groups at two ends and 100mL of toluene are added into the solution, the mixture is heated for 120 ℃ and reacts for 10 hours, azeotropic condensation is carried out to remove water, the product in a reaction bottle is subjected to silica gel column, rotary evaporation and drying to obtain yellow product, and the polymer P1 is obtained.

(3) Polymer P ₁ (n ₁ ＝20，n ₂ ＝30，R ₁ Methyl) was dissolved in anhydrous dichloromethane (polymer mass: the mass ratio of the solvent is 1g:10 mL), heating to 60 ℃, fully stirring and dissolving, dripping the solution into a polytetrafluoroethylene mould, drying nitrogen to accelerate solvent volatilization and film formation, drying the polymer to film formation, and then placing the polymer in a vacuum oven to be dried at 90 DEG CDrying for 12h to obtain the polymer film.

(4) In a drying room (the relative humidity is lower than 2 percent and the dew point is lower than-40 ℃), the prepared polymer film is overlapped with a positive plate containing high-nickel ternary material and a metallic lithium negative electrode, and then lithium salt-containing LiPF is injected ₆ 1g of electrolyte of dimethyl carbonate/ethylene carbonate (the mass ratio is 1:1) with the concentration of 1.2mol/L, and standing for 48 hours to assemble the battery.

The structural formula of the polymer P1 obtained in this example is shown below, and the properties of the obtained polymer film are shown in Table 1.

Example 2

Compared with example 1, the difference is that:

(2) Under nitrogen atmosphere, dissolving a compound A in 100g of 4-ethyl dioxolane, adding 2g of potassium bicarbonate and 5g of hydroquinone, heating for 15h at a reaction temperature of 150 ℃, cooling to room temperature, performing anhydrous anaerobic filtration to obtain a yellow solution, adding 80g of polyethylene with carboxyl groups at two ends and 100mL of toluene into the solution, heating for 120 ℃ for reaction for 10h, performing azeotropic condensation to remove water, passing the product in a reaction bottle through a silica gel column, performing rotary evaporation, and drying to obtain a yellow product, thereby obtaining a polymer P2 (n) ₁ ＝18，n ₂ ＝30)。

The structural formula of the polymer P2 obtained in this example is shown below, and the properties of the obtained polymer film are shown in table 1.

Example 3

Compared with example 1, the difference is that:

(2) Under nitrogen atmosphere, compound A is dissolved in 50g of carbonic ester monomer (propylene carbonate), 2g of potassium bicarbonate and 5g of hydroquinone are added, the reaction temperature is 150 ℃, the mixture is heated for 15h, cooled to room temperature, anhydrous and anaerobic filtration is carried out to obtain yellow solution, and carboxyl groups at two ends are added into the solutionPolyethylene (n) ₂ =40) 110g and 150mL toluene, heating to 120 ℃, reacting for 10 hours, azeotropically condensing to remove water, passing the product in the reaction bottle through a silica gel column, rotary steaming, and drying to obtain a yellow product, thus obtaining a polymer P3 (n) ₁ ＝10，n ₂ ＝40)。

The structural formula of the polymer P3 obtained in this example is shown below, and the properties of the obtained polymer film are shown in Table 1.

Example 4

Compared with example 1, the difference is that:

(2) Under the nitrogen atmosphere, dissolving a compound A in 25g of carbonate monomer (propylene carbonate), adding 2g of potassium bicarbonate and 5g of hydroquinone, heating at a reaction temperature of 150 ℃ for 15 hours, cooling to room temperature, performing anhydrous anaerobic filtration to obtain a yellow solution, adding 600g and 800mL of toluene of polyethylene (n2=200) with carboxyl groups at both ends into the solution, heating at 120 ℃ for 10 hours, performing azeotropic condensation to remove water, passing a product in a reaction bottle through a silica gel column, performing rotary evaporation, and drying to obtain a yellow product, thereby obtaining a polymer P4 (n) ₁ ＝5，n ₂ ＝200)。

The structural formula of the polymer P4 obtained in this example is shown below, and the properties of the obtained polymer film are shown in Table 1.

Example 5

Compared with example 1, the difference is that:

(2) In order to dissolve the compound A in 500g of carbonate monomer (propylene carbonate) under nitrogen atmosphere, 20g of potassium bicarbonate and 50g of hydroquinone are added, the reaction temperature is 150 ℃, the mixture is heated for 15h, cooled to room temperature and anhydrousFiltering to obtain yellow solution without oxygen, adding 30g of polyethylene (n2=10) with carboxyl groups at two ends and 40mL of toluene into the solution, heating to 120 ℃, reacting for 10 hours, azeotropically condensing to remove water, passing the product in a reaction bottle through a silica gel column, steaming in a rotary way, and drying to obtain yellow product, thus obtaining polymer P5 (n) ₁ ＝100，n ₂ ＝10)。

The structural formula of the polymer P5 obtained in this example is shown below, and the properties of the obtained polymer film are shown in Table 1.

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Example 6

Compared with example 1, the difference is that:

(4) In a drying room (relative humidity is lower than 2%, dew point is lower than-40 ℃), the prepared polymer film (polymer P1) is overlapped with a positive pole piece containing high nickel ternary material and a metallic lithium negative pole, and then lithium salt-containing LiPF is injected ₆ 4g of electrolyte of dimethyl carbonate/ethylene carbonate (the mass ratio is 1:1) with the concentration of 1.2mol/L, and standing for 48h to assemble the battery.

The polymer P1 was obtained in this example, and the properties of the obtained polymer film are shown in Table 1.

Example 7

Compared with example 1, the difference is that:

and (3) in a drying room (the relative humidity is lower than 2 percent and the dew point is lower than-40 ℃), overlapping the prepared polymer film (polymer P1) with a positive electrode plate containing a high-nickel ternary material and a metal lithium negative electrode, and then injecting 1g of electrolyte containing lithium salt LiSSI (concentration is 1.2 mol/L) and methyl ethyl carbonate/dimethyl carbonate/propylene carbonate (mass ratio is 2:2:1), standing for 48 hours, thereby assembling the battery.

Example 8

Compared with example 1, the difference is that:

(1) 30g of 3, 6-bipyridyl-4-bromo-1-cyclohexene, 10g of hydrogen peroxide and 0.1g of methyl rhenium trioxide are respectively dissolved in 500mL of dichloromethane, heated and uniformly mixed at 40 ℃, stirred and reacted for 4 hours, filtered by a silica gel column and steamed by spin to obtain a compound A.

(2) Under nitrogen atmosphere, dissolving a compound A in 100g of polydimethylsiloxane with hydroxyl at the tail end, adding 3g of potassium carbonate and 500g of acetonitrile, heating at the reaction temperature of 80 ℃ for 24 hours, cooling to room temperature, filtering and steaming to obtain a yellow product, adding the product into 80g of parylene with carboxyl at the two ends and 100mL of toluene, heating at 120 ℃ for 10 hours, performing azeotropic condensation to remove water, passing the product in a reaction bottle through a silica gel column, steaming in a rotary manner, and drying to obtain a yellow product, thereby obtaining a polymer P6 (n) ₁ ＝25，n ₂ ＝15)。

The structural formula of the polymer P6 obtained in this example is shown below, and the properties of the obtained polymer film are shown in Table 1.

Example 9

Compared with example 1, the difference is that:

(1) 30g of 3, 6-bipyridyl-4-bromo-1-cyclohexene, 10g of hydrogen peroxide and 0.1g of methyl rhenium trioxide were each dissolved in 500mL of methylene chloride, in the presence of

Heating and mixing uniformly, stirring and reacting for 4 hours, filtering by a silica gel column, and performing rotary evaporation to obtain the compound A. />

(2) Under nitrogen atmosphere, dissolving a compound A in 100g of poly (n-butyl acrylate) with hydroxyl at the tail end, adding 3g of potassium carbonate and 500g of acetonitrile, heating at 80 ℃ for 24 hours, cooling to room temperature, filtering and rotary evaporating to obtain a yellow product, adding the product into 80g of polyphenyl ether with carboxyl at the two ends and 100mL of toluene, heating at 120 ℃ for 10 hours, performing azeotropic condensation to remove water, passing the product in a reaction bottle through a silica gel column, rotary evaporating and drying to obtain a yellow product, and obtaining a polymer P7 (n) ₁ ＝15，n ₂ ＝15)。

The structural formula of the polymer P7 obtained in this example is shown below, and the properties of the obtained polymer film are shown in Table 1.

Example 10

(1) 30g of 3, 6-bipyridyl-4-bromo-1-cyclohexene, 10g of hydrogen peroxide and 0.1g of methyl rhenium trioxide are respectively dissolved in 500mL of dichloromethane, heated and mixed uniformly at 40 ℃ and stirred for reaction for 4h. Filtering by a silica gel column, and performing rotary evaporation to obtain the compound A.

(2) Under the nitrogen atmosphere, dissolving the compound A in 100g of polyethylene glycol with hydroxyl at the tail end, adding 3g of potassium carbonate and 500g of acetonitrile, heating for 24 hours at the reaction temperature of 80 ℃, cooling to room temperature, and filtering and rotary steaming to obtain a yellow product;

(3) Adding the product into polypropylene 80g and 100mL toluene with carboxyl groups at both ends, heating to 120 ℃, reacting for 10h, azeotropically condensing to remove water, passing the product in a reaction bottle through a silica gel column, rotary steaming, and drying to obtain a yellow product, thus obtaining a polymer P8 (n) ₁ ＝50，n ₂ ＝25)。

The structural formula of the polymer P8 obtained in this example is shown below, and the properties of the obtained polymer film are shown in Table 1.

Example 11

Compared with example 1, the difference is that:

(2) Under the nitrogen atmosphere, the compound A is dissolved in 100g of carbonate monomer (propylene carbonate), 2g of potassium bicarbonate and 5g of hydroquinone are added, the reaction temperature is 150 ℃, the mixture is heated for 15 hours, cooled to room temperature, anhydrous and anaerobic filtration is carried out to obtain yellow solution, and the yellow product is obtained after rotary evaporation and drying, namely the polymer P9.

The molecular chain backbone of the polymer P9 has no rigid blocks, no polyethylene blocks and only polycarbonate blocks, i.e.n ₂ ＝0。

The structural formula of the polymer P9 obtained in this example is shown below, and the properties of the obtained polymer film are shown in Table 1.

Example 12

Compared with example 1, the difference is that:

(2) Under the nitrogen atmosphere, dissolving the compound A in 80g of polyethylene with carboxyl groups at two ends and 100mL of toluene, adding 2g of potassium bicarbonate and 5g of hydroquinone, heating for 15h at a reaction temperature of 150 ℃, passing the product in a reaction bottle through a silica gel column, steaming in a rotary way, and drying to obtain a yellow product, namely a polymer P10.

The molecular chain of the polymer P10 has no flexible block, and only the polyethylene block has no polycarbonate block, i.e., n1=0.

The structural formula of the polymer P10 obtained in this example is shown below, and the properties of the obtained polymer film are shown in Table 1.

Example 13

Compared with example 1, the difference is that:

about 25g of 3, 6-bipyridyl-1, 3-cyclopentadiene and 17g of m-chloroperoxybenzoic acid are respectively dissolved in 500mL of dichloromethane, heated and mixed uniformly at 50 ℃ and stirred for reaction for 4h. Filtering by a silica gel column, and performing rotary evaporation to obtain the compound A. The polymer P11 (n) ₁ ＝20，n ₂ The structural formula of =30) is as follows, and properties of the obtained polymer film are shown in table 1.

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Comparative example 1

Compared with example 1, the difference is that:

(2) Adding 2g of potassium bicarbonate and 5g of hydroquinone into 100g of propylene carbonate, heating at a reaction temperature of 150 ℃ for 15 hours, cooling to room temperature, performing anhydrous anaerobic filtration to obtain a yellow solution, adding 80g of polyethylene with carboxyl groups at two ends and 100mL of toluene into the solution, heating at 120 ℃ for 10 hours, performing azeotropic condensation to remove water, passing the product in a reaction bottle through a silica gel column, performing rotary evaporation, and drying to obtain a yellow product, namely a polymer P11.

The molecular chain end of the polymer P12 has no epoxy group and pyridine group, and the molecular chain of the polymer is a copolymer of polyethylene and polycarbonate.

The structural formula of the polymer P12 obtained in this comparative example is shown below, and the properties of the obtained polymer film are shown in Table 1.

Test method

(1) The method for testing the ion conductivity comprises the following steps:

the sample of the polymer electrolyte membrane is clamped by two stainless steel sheets and placed in a 2016 type battery shell, the electrochemical alternating current impedance spectroscopy is adopted in an electrochemical workstation (BioLogic Science Instruments) to measure the lithium ion conductivity, the frequency range is 0.1 Hz-100 kHz, the sigma is the ion conductivity according to sigma=L/(R.times.S), the L is the electrolyte thickness, the S is the contact area of the electrolyte membrane and an electrode, and the R is the impedance measured by an impedance meter.

(2) Test method of electrochemical stability window:

the sample of the polymer electrolyte membrane is clamped by a stainless steel sheet and a lithium sheet and is placed in a 2016 type battery shell, an electrochemical working window is measured by linear volt-ampere scanning by an electrochemical working station (BioLogic Science Instruments), the initial potential is open-circuit voltage, the highest potential is 6V, and the scanning speed is 10mV/s.

(3) The method for testing the migration number of lithium ions comprises the following steps:

and (5) characterizing the migration number of the lithium ions by adopting a timing current steady-state method. Specifically, a sample of the polymer electrolyte membrane was sandwiched between two lithium sheets and placed in a 2016 cell housing to assemble a button-type symmetrical non-blocking cell, which was tested at a VSP potentiostat (BioLogic Science Instruments) electrochemical workstation. In an initial state, under a constant voltage DeltaV (set to 10 mV), charged substances in the system can migrate, and a concentration difference is formed between the two electrodes, and an initial current Io is recorded; over time, the concentration difference between the two electrodes increases, the ion migration slows down, the current decreases, a process called polarization; when steady state is reached, only cations migrate and the steady state current Iss is recorded. Before and after the timing current test, the Iss of the battery in the initial state and the steady state needs to be tested respectively, and the corresponding impedances Ro and Rss are recorded.

According to the formula

And obtaining the migration number of lithium ions.

(4) Method for testing peel strength and tensile strength of polymer electrolyte membrane:

the polymer gel electrolyte was tested for peel strength according to IPC-TM-6502.8 using the Shimadzu AG-X50N peel machine. The mirror surface steel plate is wiped by alcohol, the double-sided tape is stuck on the mirror surface copper plate, the adhesive tape is firmly bonded with the steel plate without bubbles in the adhesive tape sticking process, the polymer gel electrolyte is coated on the pole piece, the coated pole piece is cut into 25mm small strips of 220mm, one surface of the coated electrolyte is bonded on the steel plate by the double-sided tape, the pole piece is parallel to the steel plate, the automatic press roller instrument is used for rolling back and forth for 3 times, the stripping machine is opened, the stripping speed is set to be 100mm/min, the lower clamp clamps the steel plate, the upper clamp clamps the pole piece, zero clearing and starting test are carried out, each material is tested for 5 times, and the average value is obtained. According to the formula: t=p/B, where T represents peel strength (mN/mm), P represents average peel force (mN), and B represents sample test width (mm).

The tensile strength and elongation at break were measured according to GB/T1040-1992, type II specimens using a universal tester (Intron 5565) at a tensile speed of 500mm/min.

(5) Method for testing A1/A2 of polymer

Opening an infrared spectrometer, preheating for half an hour, uniformly coating a dried polymer sample on transparent glass, and then testing a sample test surfaceDirectly put on ATR (attenuated total reflect) sampler, rotate the sampler fixing button to press the sample, take air as background, at 4000cm ^-1 -500cm ^-1 Scanning for three times in a range, and collecting attenuated total reflection infrared spectrums of samples to obtain maximum light transmission peak intensities A1 and A2 of the related flexible block and rigid block.

The test results of examples 1 to 13 and comparative example 1 are shown in table 1 below:

TABLE 1

As can be seen from the results of FIG. 1, the polymer electrolyte membrane produced in example 1 has an infrared spectrum of 2842cm ^-1 、1710cm ^-1 The infrared peaks correspond to carbonate groups and methylene groups, respectively, and to the chemical structure of the polymer. As can be seen from the results of fig. 2, the polymer electrolyte membrane has high lithium ion conductivity and can rapidly conduct lithium ions. As can be seen from the results of fig. 3, the electrochemical stability window of the polymer electrolyte thin film shows that the polymer electrolyte has high voltage resistance, can be used with high voltage electrode materials, and improves the power and energy density of the battery. As can be seen from the results of fig. 4, the polymer electrolyte film has high peel strength and excellent adhesion, and can ensure the adhesion between the polymer electrolyte and the positive and negative electrode materials, avoid detachment during cyclic expansion and contraction, and improve the operation stability of the battery.

From the data in Table 1, it can be seen that the polymer electrolyte membranes of examples 1 to 10 can have lithium ion conductivities as high as 4.5X10 ^-4 S/cm and above, the electrochemical window reaches 4.6V and above, and the ion migration number reaches 0.42 and above.

This is because the epoxy three-membered ring group at the end of the polymer molecule chain in the polymer electrolyte can undergo a ring opening reaction, and react with a metal ion in an electrode active material or a hydroxyl group on the surface of a separator, and the like, and the reaction activity is extremely strong under the self-catalytic action of aliphatic six-membered ring tension and a pyridyl group, so that the interface of the polymer electrolyte has high adhesive force. And under the interface voltage of the pole piece and the electrolyte in the charge and discharge process of the battery, inducing pyridine groups at the tail ends of polymer molecular chains to initiate ring-opening polymerization of epoxy groups to form chemical bonds, so that firm adhesion is generated.

The polymer molecular chain in the polymer electrolyte contains a large number of carbonate structural units, has higher flexibility, can improve the bonding capacity of the polymer molecular chain, and improves the adhesive force of the groups at the tail end of the molecular chain and interfaces such as pole pieces; and the carbonate structural unit can be mutually adsorbed with carbonates with similar structures in the organic solvent of the electrolyte, so that the liquid absorption performance of the carbonate electrolyte is improved, the absorption and liquid storage capacity of the polymer film to the electrolyte is enhanced, and the conductivity of the polymer electrolyte is improved.

The middle block of the polymer molecular chain is a regular and ordered polyethylene block, the reactivity of the polyethylene block is low, the pressure resistance and the safety performance of the polymer film can be improved, electrolyte can not be embedded and permeated into the polyethylene block, the compatibility with flexible blocks (polycarbonate blocks) positioned at two ends of the molecular chain is poor, the self-assembly of the polymer molecular chain into a layered and ordered structure is promoted, and the concentration and the migration rate of lithium ions in an amorphous region are improved.

In example 11, the polymer molecular chain P9 had only a flexible block (polycarbonate block) and no rigid block, and the flexibility of the polymer molecular chain was significantly reduced, and the tensile strength and peel strength of the polymer electrolyte were reduced as compared with example 1.

The polymer molecular chain P10 in example 12 had only a rigid block (polyethylene block), no flexible block, and the molecular chain structure was regular, and the electrolyte dissolution and absorption ability was greatly reduced, resulting in a great reduction in lithium ion conductivity, a lack of flexible blocks in the molecular chain, a reduction in flexibility, and a reduction in peel strength as compared with example 1.

The polymer molecular chain P11 of comparative example 1 has no epoxy group and pyridine group at both ends, only a polyethylene block and a polycarbonate block, and the complexation of the polymer molecular chain with the active material on the pole piece decreases, the tensile strength and peel strength of the polymer electrolyte decreases, and the adhesion of the polymer electrolyte to the pole piece decreases.

While the preferred embodiment has been described, it is not intended to limit the scope of the claims, and any person skilled in the art can make several possible variations and modifications without departing from the spirit of the invention, so the scope of the invention shall be defined by the claims.

Claims

1. A polymer comprising a polymer backbone and end capping groups, the end capping groups comprising pyridine groups and epoxy groups;

the molecular chain of the polymer is in a triblock structure, and the triblock structure is a flexible block with the end capping group, namely a rigid block and a flexible block with the end capping group;

the flexible block is selected from polycarbonate, polydimethylsiloxane, poly-n-butyl acrylate and polyethylene glycol, and the rigid block is selected from polyolefin, polyacetylene, parylene and polyphenyl ether.

2. A polymer comprising a polymer backbone and end capping groups, the end capping groups comprising pyridine groups and epoxy groups; the molecular chain of the polymer is in a triblock structure, and the triblock structure is a flexible block with the end capping group, namely a rigid block and a flexible block with the end capping group;

The structural formula of the polymer is shown in the following formula I:

wherein R is ₁ Selected from halogen, substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstitutedSubstituted alkynyl, substituted or unsubstituted aryl;

the R is ₂ And R is ₃ Each independently selected from substituted or unsubstituted alkyl, and R ₂ And R is ₃ Forming a ring by C-C connection;

3. The polymer of claim 2, wherein the polymer meets at least one of the following characteristics:

a.R ₄ any one selected from ethenyl, propenyl, ethynyl, p-xylyl and phenyl ether;

b.n ₁ the value range is between 10 and 50; n is n ₂ The value range is 20 to 80;

c. the structural formula of the polymer is shown in the following formula I-1:

4. A polymer electrolyte comprising an electrolyte solution and the polymer according to any one of claims 1 to 3.

5. The polymer electrolyte according to claim 4, wherein the molecular chain of the polymer is a triblock structure of a flexible block having a terminal group-a rigid block-a flexible block having a terminal group; repetition in the flexible block of the polymer in the infrared absorption spectrumThe unit has a wavelength of 3000cm ^-1 ～600cm ^-1 The maximum light transmission peak intensity within the range is A ₁ The repeating units in the rigid block of the polymer are at a wavelength of 3000cm ^-1 ～600cm ^-1 The maximum light transmission peak intensity within the range is A ₂ The method comprises the steps of carrying out a first treatment on the surface of the The mass content of the electrolyte in the polymer electrolyte is W%, the peel strength of the polymer electrolyte is T mN/mm, and T satisfies the following relation:

A ₁ /A ₂ -10％≤T/1000W≤A ₁ /A ₂ +10％。

6. the polymer electrolyte according to any one of claims 4 to 5, wherein the polymer electrolyte satisfies at least one of the following characteristics:

a. the polymer electrolyte is a polymer electrolyte membrane;

b. the thickness of the polymer electrolyte membrane is 5 μm to 300 μm;

c. the tensile strength of the polymer electrolyte membrane is 0.2Mpa to 20Mpa;

d. the peel strength of the polymer electrolyte membrane is 150mN/mm to 600mN/mm.

7. A method of preparing the polymer of claim 1 or 2, comprising:

mixing the first compound with at least one monomer or at least one rigid block molecular chain, and heating to perform polymerization reaction to obtain the polymer.

8. The method of preparing a polymer according to claim 7, wherein the method satisfies at least one of the following characteristics:

a. the end capping agent is selected from at least one of bipyridyl cycloolefin and bromo bipyridyl cyclohexene;

b. the oxidant is at least one selected from m-chloroperoxybenzoic acid and hydrogen peroxide;

c. the mass ratio of the end capping agent to the oxidant is 1: (0.1-2);

d. the oxidation reaction temperature is 30-100 ℃, and the oxidation reaction time is 2-10 h;

e. the solvent is selected from at least one of dichloromethane, toluene and acetonitrile;

f. the mass ratio of the first compound to the monomer is (2-100): 100;

g. the polymerization reaction is carried out under a protective atmosphere;

h. the protective atmosphere comprises at least one of nitrogen, argon, neon and helium;

i. The temperature of the polymerization reaction is 60-160 ℃, and the time of the polymerization reaction is 5-30 h;

j. the step of mixing the first compound with at least one monomer or at least one rigid block molecular chain comprises: mixing the first compound, at least one monomer or at least one rigid block molecular chain, and an initiator;

k. the initiator comprises at least one of carbonate, bisphenol compound and nitrile compound;

and l, the mass ratio of the initiator to the monomer is (2-30): 100;

after mixing the first compound with at least one monomer and heating to polymerize, the method further comprises: heating the polymer and a rigid block molecular chain to perform a secondary polymerization reaction to obtain a polymer with a triblock structure;

and n, the mass ratio of the polymer to the rigid block molecular chain is (5-100): (10-200);

and o, the temperature of the secondary polymerization reaction is 80-160 ℃, and the time of the secondary polymerization reaction is 5-20 h.

9. A lithium ion battery, characterized in that it comprises a polymer electrolyte according to any one of claims 4 to 6.