CN114940762A

CN114940762A - Polymer, preparation method thereof, polymer electrolyte and lithium ion battery

Info

Publication number: CN114940762A
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: 2022-08-26
Anticipated expiration: 2042-05-18
Also published as: CN114940762B

Abstract

The application relates to a polymer and a preparation method thereof, a polymer electrolyte and a lithium ion battery, wherein a terminal group of the polymer comprises a pyridine group and an epoxy group, and the existence of the pyridine group and the epoxy group can improve the connection action strength of a polymer molecular chain and an electrode active substance. The polymer, the preparation method thereof, the polymer electrolyte and the lithium ion battery improve the adhesive capacity of the polymer electrolyte and improve the adhesive force of the polymer electrolyte to a 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, 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 rapidly in recent decades, and is widely applied to the fields of small energy storage equipment, electric automobiles, smart power grids and the like. However, the lithium ion battery is usually used with an organic small molecule liquid electrolyte, and the liquid electrolyte of the lithium battery usually has safety problems such as growth of lithium dendrite and leakage and volatilization of the electrolyte.

Solid polymer electrolytes such as polyethylene oxide (PEO) are brittle and are difficult to bear internal and external strains such as bending, stretching and shearing. Solid state electrolytes are considered to be one of the most promising materials for practical applications of lithium batteries, and although inorganic ceramic electrolytes have excellent ionic conductivity, their lack of flexibility and fragility limits practical applications. The polyoxyethylene-based solid polymer electrolyte has the advantages of easiness in film formation, good chemical stability and the like, however, the high crystallinity of polyoxyethylene limits the movement of a polymer chain, and the rapid transmission of lithium ions is hindered, so that the room-temperature ionic conductivity of the electrolyte is generally low.

During the use of lithium batteries, the lithium batteries are inevitably affected by various deformations and local stresses, which severely limit the life and reliability of the batteries, eventually leading to failure of the battery system. The existing non-aqueous polymer gel electrolyte does not have enough elasticity and self-repairing performance, and the electrolyte is easy to cause the problems of short circuit, breakage and the like in the production, transportation and use of a battery, so that the good contact of an electrolyte interface is difficult to be ensured in the circulating process. In the battery cycle process, the pole piece loaded with the active material can expand and contract in the charging and discharging process and repeatedly change back and forth, so that the interface between the polymer electrolyte and the pole piece is easily separated.

Disclosure of Invention

In view of this, the application provides a polymer, a preparation method thereof, a polymer electrolyte and a lithium ion battery, which can improve the adhesive capacity of the polymer electrolyte and improve the adhesive force of the polymer electrolyte to a pole piece.

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

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

The pyridine group can increase the electron-donating ability of the epoxy group and improve the electrophilic action of the epoxy group and Lewis acid, namely improve the ring-opening reaction activity of the epoxy group; and the pyridine group can be complexed with lithium salt, has an autocatalysis effect, can autocatalyze an epoxy group ring-opening reaction on a molecular chain, improves the reaction degree and the reaction speed, and different epoxy groups are connected to form a bonding material with high bonding strength. The nitrogen atom of the pyridine group has lone pair electrons and can also be used as an electron donor to perform coordination and complexation with the exposed metal atom of the active metal oxide on the anode, and the interaction between the polymer molecular chain and the anode metal ions or the cathode metal lithium is formed through coordination bonds, so that the adhesive force of the polymer electrolyte to the pole piece is improved.

In some possible embodiments, the molecular chain of the polymer is a triblock structure, which is a flexible block having the end-capping group-a rigid block-a flexible block having the end-capping group.

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 a polyethylene block, a polypropylene block, a polyacetylene block, a parylene block, a polyphenylene oxide.

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

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 substituted or unsubstituted alkyl, substituted or unsubstituted alkenyl, substituted or unsubstituted alkynyl, substituted or unsubstituted aryl;

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

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

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

In some possible embodiments, R ₄ Is selected from any one of vinyl, propenyl, ethynyl, p-xylyl and phenyl ether.

In some possible embodiments, n ₁ A value in the range of 10 to 50; n is ₂ The range is between 20 and 80.

In some possible embodiments, the polymer has a structural formula as shown in formula I-1 below:

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

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

In some possible embodiments, the molecular chain of the polymer is a triblock structure, which is a flexible block with end-capping groups-a rigid block-a flexible block with end-capping groups; in the infrared light absorption spectrum, the repeating unit in the flexible block of the polymer has a wavelength of 3000cm ^-1 ～600cm ^-1 The maximum light transmission peak intensity in the range is A ₁ The repeating unit in the rigid block of the polymer has a wavelength of 3000cm ^-1 ～600cm ^-1 The maximum light transmission peak intensity in the range of A ₂ (ii) a 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 includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorophosphate, lithium bistrifluoromethanesulfonylimide, lithium bis (fluorosulfonyl) imide, lithium bisoxalato borate, or lithium difluorooxalato borate.

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

In some possible embodiments, the organic solvent includes a carbonate-based compound.

In some possible embodiments, the organic solvent includes a carbonate-based compound including at least one of ethylene carbonate, propylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, and butylene carbonate.

In some possible embodiments, the carbonate compound is present in the electrolyte in an amount of 30 to 95% by weight.

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

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

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

In some possible embodiments, the polymer electrolyte membrane has a peel strength of 150mN/mm to 600 mN/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 an oxidation reaction to obtain a first compound, wherein the blocking agent contains a pyridine group and a cyclic olefin group;

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 some possible embodiments, the capping agent is selected from at least one of dipyridyl cycloolefins, bromo dipyridyl 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 feasible embodiments, the temperature of the oxidation reaction is 30-100 ℃, and the time of the oxidation reaction is 2-10 h.

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 (2-100): 100.

in some possible embodiments, the monomer is selected from at least one of a carbonate, an alkenoic acid ester, a siloxane, and a 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 temperature of the polymerization reaction is 60 ℃ to 160 ℃, and the time of the polymerization reaction is 5h to 30 h.

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: mixing the first compound, at least one monomer or at least one rigid block molecular chain and an initiator.

In some possible embodiments, the initiator includes at least one of a carbonate, a bisphenol, 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 a rigid block molecular chain to perform secondary polymerization reaction to obtain the polymer with a 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 feasible embodiments, the temperature of the secondary polymerization reaction is 80-160 ℃, and the time of the secondary polymerization reaction is 5-20 h.

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

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

the end-capping group at the end of the molecular chain of the polymer provided by the application contains an epoxy group and a pyridine group; the epoxy group can generate strong complexation with Lewis acid such as hydrogen ions generated by lithium ions or lithium salt hydrolysis and the like to promote the epoxy group to generate ring-opening reaction, and the epoxy group can generate reaction with active substances on the pole piece, such as the defect position on the surface of the positive metal oxide, the structural defect position of the negative graphite, and the like such as hydroxyl, carboxyl or amino on the binder carboxymethyl cellulose, and can form chemical bond connection, thereby improving the connection strength of the polymer molecular chain and the electrode active substances and increasing the caking property of the polymer electrolyte.

The pyridine group can increase the electron-donating ability of the epoxy group and improve the electrophilic action of the epoxy group and Lewis acid, namely improve the ring-opening reaction activity of the epoxy group; and the pyridine group can have an autocatalysis effect after being complexed with lithium salt, can autocatalyze the ring opening reaction of the epoxy group on the molecular chain, improve the reaction degree and the reaction rate, and different epoxy groups are connected to form a bonding material with high bonding strength. The nitrogen atom of the pyridine group has lone pair electrons and can also be used as an electron donor to generate coordination complexation with the exposed metal atom of the active metal oxide on the anode, and the interaction between the polymer molecular chain and the anode metal ion or the cathode metal lithium is formed through coordination bonds, so that the adhesion of the polymer electrolyte to the pole piece is improved.

In some embodiments, the polymer molecular chain is a triblock structure, random flexible blocks are arranged at two ends of the molecular chain, and side chains R in the flexible blocks ₁ The disorder degree of the molecular chain can be increased, the polar group in the flexible block can easily generate a complexing effect or a similar compatible effect with lithium salt and a carbonate organic solvent in electrolyte, the dissolving and absorbing capacity of the flexible block to the lithium salt and the electrolyte can be improved, the flexibility of the flexible block in the molecular chain can be improved, the movement resistance of the terminal group at the tail end of the molecular chain is smaller, and the bonding capacity of the polymer molecular chain is improved.

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 orderly arranged and stacked is easy to generate, the reaction activity is low, the pressure resistance and the safety performance of the polymer film can be improved, the electrolyte cannot be embedded into and permeate into the rigid block, the compatibility of an amorphous area formed by the rigid block and the flexible block is poor, the triblock polymer molecular chain can be promoted to be self-assembled into a layered ordered structure, 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 adopting the end-capping reagent and the oxidant, and the polymer is prepared by utilizing 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 generate strong complexation with Lewis acid to promote the ring-opening reaction of the epoxy group, and the epoxy group can generate reaction with active substances on a pole piece, such as a defect position on the surface of a positive metal oxide, a structural defect position of negative graphite, and an equal hydroxyl group, a carboxyl group or an amino group on a binder carboxymethyl cellulose, so that a chemical bond connection can be formed, the connection effect strength of the polymer molecular chain and an electrode active substance is improved, and the caking property of a polymer electrolyte is improved. 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 have an autocatalysis effect after being complexed with lithium salt, can autocatalyze the ring opening reaction of the epoxy group on the molecular chain, improve the reaction degree and the reaction rate, and different epoxy groups are connected to form a bonding material with high bonding strength. The nitrogen atom of the pyridine group has lone pair electrons and can also be used as an electron donor to perform coordination and complexation with the exposed metal atom of the active metal oxide on the anode, and the interaction between the polymer molecular chain and the anode metal ions or the cathode metal lithium is formed through coordination bonds, so that the adhesive force of the polymer electrolyte to the pole piece is improved.

Drawings

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

FIG. 2 is a graph showing the results of an ion conductivity test of a polymer electrolyte membrane provided in example 1 of the present application;

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

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

Detailed Description

While the following is a description of the preferred embodiments of the present invention, it should be noted that those skilled in the art can make various modifications and improvements without departing from the principle of the embodiments of the present invention, and such modifications and improvements are considered to be within the scope of the embodiments of the present invention.

The embodiment of the application provides a polymer, which comprises a polymer main chain and an end capping group, wherein the end capping group comprises a pyridine group and an epoxy group.

The end-capping group at the end of the molecular chain of the polymer provided by the application contains an epoxy group and a pyridine group; the epoxy group can generate strong complexation with Lewis acid such as hydrogen ions and the like generated by lithium ions or lithium salt hydrolysis, promote the epoxy group to generate ring-opening reaction, and react with active substances on a pole piece, such as the defect position on the surface of a positive metal oxide, the structure defect position of negative graphite, and the like of hydroxyl, carboxyl or amino on binder carboxymethyl cellulose, so that chemical bond connection can be formed, the connection strength of a polymer molecular chain and an electrode active substance is improved, and the caking property of the polymer electrolyte is increased.

The pyridine group can increase the electron-donating capacity of the epoxy group, improve the electrophilic action of the epoxy group and Lewis acid, and promote the reactivity of the epoxy group and external active groups such as hydroxyl and carboxyl, namely improve the ring-opening reactivity of the epoxy group; and the pyridine group can have an autocatalysis effect after being complexed with lithium salt, can autocatalyze the ring opening reaction of the epoxy group on the molecular chain, improve the reaction degree and the reaction rate, and the epoxy groups on different molecular chains are connected to form a bonding material with high bonding strength. The nitrogen atom of the pyridine group has lone pair electrons and a large pi ring, and can also be used as an electron donor to generate electron cloud conjugation or metal coordination complexing action with the exposed metal atom of the active metal oxide on the anode, so that the interaction force between the polymer molecular chain and the anode metal ion or the cathode metal lithium is formed through coordination bonds, and the adhesive property 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, the triblock structure being a flexible block having the end capping group-a rigid block-a flexible block having the end capping group.

In the scheme, the two ends of the molecular chain are provided with the irregular flexible blocks, the molecular chain motion flexibility of the flexible blocks is strong, the peristaltic swing degree of the molecular chain tail end can be improved, and further the contact reaction resistance of the terminal group and the active substance is reduced, so that the terminal group motion resistance at the molecular chain tail end is smaller, meanwhile, the flexible blocks have better viscosity, can generate strong bonding effect with the surface of the active substance, and improve the bonding capability of the polymer molecular chain; the side chain in the flexible block can increase the disorder degree of the molecular chain and improve the adhesive capacity of the polymer molecular chain.

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 orderly arranged and stacked are easy to generate, a regular ordered region is formed, electrolyte cannot be embedded into and permeate 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 molecular chains of the triblock polymer 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 soft 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:

wherein R is ₁ Selected from the group consisting of 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;

In some embodiments, the alkyl group may be a chain alkyl group or a cyclic alkyl group, the chain alkyl group may be a straight chain alkyl group or a branched alkyl group, and the hydrogen on the ring of the cyclic alkyl group may be further substituted by an alkyl group. Alkyl may also be cycloalkyl, heteroalkyl, cycloheteroalkyl, heterocycloalkyl, alkylcarbonyl, cycloalkylcarbonyl, heteroalkylcarbonyl, cycloheteroalkylcarbonyl, heterocycloalkylcarbonyl, carbalkoxy, cycloalkoxy, heteroalkylester, cycloheteroalkylester, heterocycloalkanoxy.

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

Alkenyl groups may include cycloalkenyl, heteroalkenyl, cycloheteroalkenyl, heterocycloalkenyl, alkenylcarbonyl, cycloalkenylcarbonyl, heteroalkenylcarbonyl, cycloheteroalkenylcarbonyl, heterocycloalkenylcarbonyl, alkenylester group, cycloalkenylester group, heteroalkenylester group, cycloheteroalkenylester group; alkynyl groups may include cycloalkynyl, heteroalkynyl, heterocycloalkynyl; aryl groups may include aralkyl, heteroaryl, alkylsulfonyl, arylsulfonyl, heteroarylsulfonyl, heterocyclylsulfonyl.

In some embodiments, R ₂ And R ₃ Each independently selected from substituted or unsubstituted alkyl, and R ₂ And R ₃ Form a ring through C-C connection.

In some embodiments, R ₂ And R ₃ By C-C connection to form six-membered, seven-membered, eight-membered rings, etcAnd is not limited herein. Illustratively, R ₂ And R ₃ The aliphatic six-membered ring is connected with the epoxy three-membered ring, so that the structure is stable, the aliphatic six-membered ring can fix the space configuration of two carbon atoms of the epoxy three-membered ring, the ring tension of the epoxy three-membered ring is enhanced, the epoxy bond is fully exposed, the lone pair electrons on the oxygen atom are exposed, and the complex reaction activity of the epoxy three-membered ring is improved.

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

n ₂ The value range is between 10 and 200; n is a radical of an alkyl radical ₂ Specifically, the value may be 10, 15, 20, 28, 30, 35, 40, 50, 65, 85, 100, 110, 130, 150, 170, or 200, etc., or may be other values within the above range, which is not limited herein. Preferably, n ₁ The range is between 20 and 80.

By controlling the above n ₁ And n ₂ The value of (2) can control the molecular chain arrangement structure, so that the advantages of each block can be comprehensively balanced by the triblock polymer, the strength of the rigid block and the flexibility of the flexible block are exerted, and the conductivity and the mechanical property of the polymer electrolyte are considered.

In some embodiments, the flexible blocks at both sides of the polymer molecular chain are flexible chains with molecular chain rotation easily, and the spatial configuration is a free-curling random coil, 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, a carbonate group in the polycarbonate block is a polar group, a molecular bond angle is large, the molecular group can freely extend, and is very easy to generate a complexing action or a similar compatibility action with a lithium salt and a carbonate organic solvent in an electrolyte, so that the dissolving and absorbing abilities of the polycarbonate block to the lithium salt and the electrolyte are improved, the flexibility of the polycarbonate block in a molecular chain can be improved, the movement resistance of a terminal group located at the end of the molecular chain is smaller, the adhesive ability of the polymer molecular chain is improved, and the interface stability of a polymer electrolyte and an electrode plate is improved.

The polycarbonate block forms a random area of the polymer, the solubility to lithium salt is high, and the carbonate-based contact constant is high, so that intramolecular polarization is high, the complexation of the flexible block and lithium ions is facilitated, the dissolution and migration of lithium salt are promoted, and the ionic conductivity of the polymer electrolyte is improved. Side chain R in the Flexible Block ₁ The disorder degree of the molecular chain can be increased, and the bonding capability of the polymer molecular chain is improved.

In some embodiments, the rigid block located in the middle of the polymer molecular chain has a regular molecular chain structure and is easy to be orderly arranged and stacked to form a crystal structure, the electrolyte and the lithium salt are difficult to be embedded into the rigid block molecular chain, and the rigid block is used as a base layer for mechanical support of the polymer molecular chain, so that the polymer electrolyte is guaranteed to have higher conductivity and superior mechanical properties.

In some embodiments, the rigid block can be a polyolefin block (e.g., a polyethylene block, a polypropylene block), a polyacetylene block, a parylene block, a polyphenylene ether block, and the like. Preferably, the rigid block is a polyolefin block, has low reaction activity, and can improve the pressure resistance and safety performance of the polymer electrolyte; the crystal structure formed by the polyolefin blocks in close packing enables lithium salt and electrolyte to hardly participate in molecular chain arrangement, and the molecular chain structure cannot be dissolved and damaged, so that the rigid blocks can bear large external mechanical acting force, and the mechanical strength of the polymer electrolyte is favorably provided.

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

As an alternative to the present application, the flexibility of the polymer in the infrared absorption spectrumThe repeating units in the block have a wavelength of 3000cm ^-1 ～600cm ^-1 The maximum light transmission peak intensity in the range is A ₁ The repeating unit in the rigid block of the polymer has a wavelength of 3000cm ^-1 ～600cm ^-1 The maximum light transmission peak intensity in the range is A ₂ (ii) a 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 at the wavelength corresponding to the peak of chemical bond vibration in the repeating unit structure in the infrared absorption spectrum of 3000-600 cm-1. The repeating unit in the soft block may be polypropylene carbonate (maximum light transmittance peak intensity A1 of 2842 cm) ^-1 ) Polydimethylsiloxane (maximum light transmittance peak intensity A1 of 1008 cm) ^-1 ) Poly (n-butyl acrylate) (maximum light transmittance peak intensity A1 1730 cm) ^-1 ) Polyethylene glycol (maximum light transmittance peak intensity A1 is 1060 cm) ^-1 )。

The peeling strength T and the proportion of the rigid block and the flexible block on the polymer molecular chain have an incidence relation, the reasonable matching ratio of the rigid block and the flexible block can exert the adhesive property of the polymer molecular chain to the maximum extent, meanwhile, the adhesive strength of the polymer electrolyte is also related to the polymer content and the electrolyte content of the electrolyte, the electrolyte content is too high, which is beneficial to improving the ionic conductivity of the polymer electrolyte but not beneficial to improving the adhesive property; if the electrolyte content is too low, the polymer electrolyte is too dry to exhibit the adhesive properties of the polymer. By controlling the three components within the above relationship range, the adhesive property of the polymer electrolyte can be effectively exerted.

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

in infrared light absorption spectrum, the polymer electrolyte has a wavelength of 1700cm ^-1 ～1750cm ^-1 In the range corresponding to the carbonate group in the polycarbonate block, the light transmission peak intensity of the carbonate group is A ₁ The polymer electrolyte has a wavelength of 2830cm ^-1 ～2880cm ^-1 The light transmission peak intensity of the methylene group corresponding to the methylene group in the polyethylene block 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 molecular chain of the polymer is 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, ethyl methyl carbonate, ethylene carbonate, propylene carbonate, and butylene carbonate. It can be understood that the carbonate compound has a carbonate group, and the polar group (such as amino group, hydroxyl group, ester group, etc.) contained in the polymer main 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.

In some embodiments, the carbonate compound may be present in the electrolyte solution in an amount of 30% to 95% by mass, specifically 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or 95% by mass, or the like, or may have other values within the above range, which is not limited herein.

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

Lithium salt in the polymer electrolyte coordinates with polar groups on the molecular chains, so that the polar degree of the molecular chains at two ends of the polymer can be improved, the dipole moment in the molecules is increased, the difference between the lithium salt and the middle rigid block is large, obvious incompatibility is generated, the incompatible molecular repulsion action promotes the spontaneous assembly of the molecular chains, a layered structure is formed, the molecular chains at two ends are further distributed outside the polymer aggregate, the aliphatic cyclic epoxy groups at the tail ends of the molecular chains are also exposed outside the aggregate, the probability of mutual connection with the outside, such as pole piece active matters and the outside of adjacent aggregates, is improved, and the adhesive force of the polymer electrolyte is further improved.

In some embodiments, the concentration of the lithium salt in the electrolyte solution 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, and the like, and may be other values within the above range, which is not limited herein.

In some embodiments, the polymer electrolyte has an ionic conductivity of 0.1 × 10 ^-4 S/cm to 20X 10 ^- ⁴ S/cm; specifically, it may be 1.0X 10 ^-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., but may be other values within the above range, and is not limited thereto. The ionic conductivity of the polymer electrolyte is less than 1.0 x 10 ^-4 S/cm is not beneficial to improving the electrochemical performance of the lithium battery.

In some embodiments, the polymer electrolyte has an electrochemical stability window of 4V to 6V; specifically, it 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., or may be other values within the above range, and is not limited herein. The polymer electrolyte membrane has an electrochemical stability window of more than 4V, has high voltage resistance, can be matched with a high-voltage electrode material for use, and improves the power and energy density of a battery.

In some embodiments, the polymer electrolyte has an ion transport number of 0.2 to 0.7; specifically, the value 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., or may be other values within the above range, which is not limited herein. Controlling the ion migration number of the polymer electrolyte within the above range can be beneficial to the polymer electrolyte to form a continuous ion migration channel, and can improve the conduction of effective charges.

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

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, or 300 μm, etc., but may be other values within the above range, which is not limited herein. The polymer electrolyte membrane is too thick, which results in a large membrane impedance; 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, or 20Mpa, and the like, and may be other values within the above range, which is not limited herein. The tensile strength of the polymer electrolyte membrane is within the range, which shows that the polymer electrolyte membrane has better mechanical property, and enough elasticity can also effectively buffer the external force impact existing in the use, transportation and production of the solid-state battery and the strain such as expansion and shrinkage of a pole piece in the electrochemical cycle process of the battery, so that the problems of interface falling, electrolyte layer peeling, fracture and the like caused by internal and external forces to deteriorate the battery performance are avoided, the possibility of short circuit of the lithium battery is reduced, and the stability of the solid-state battery is enhanced.

In some embodiments, the polymer electrolyte membrane has a peel strength of 150mN/mm to 600 mN/mm. Specifically, the concentration may be 150mN/mm, 180mN/mm, 200mN/mm, 250mN/mm, 300mN/mm, 450mN/mm, 520mN/mm, 550mN/mm or 600mN/mm, etc., and may be other values within the above range, which is not limited. The tensile strength of the polymer electrolyte membrane is within the above range, which is advantageous for efficiently exhibiting the adhesive properties 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 cyclic olefin group;

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

In the scheme, a first compound containing a pyridine group and an epoxy group is prepared by adopting a blocking agent and an oxidant, and the first compound is polymerized with at least one monomer or at least one rigid block molecular chain to obtain a polymer, so that the tail end of the polymer molecular chain contains the epoxy group and the pyridine group, wherein the epoxy group can generate strong complexation with Lewis acid to promote the ring-opening reaction of the epoxy group, and the epoxy group can react with active substances on a pole piece, such as a defect position on the surface of a positive metal oxide, a structural defect position of negative graphite, hydroxyl, carboxyl or amino on a binder carboxymethyl cellulose, and the like to form a chemical bond connection, so that the connection strength of the polymer molecular chain and an electrode active substance is improved, and the caking property 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 have an autocatalysis effect after being complexed with lithium salt, can autocatalyze the ring opening reaction of the epoxy group on the molecular chain, improve the reaction degree and the reaction rate, and different epoxy groups are connected to form a bonding material with high bonding strength. The nitrogen atom of the pyridine group has lone pair electrons and can also be used as an electron donor to perform coordination and complexation with the exposed metal atom of the active metal oxide on the anode, and the interaction between the polymer molecular chain and the anode metal ions or the cathode metal lithium is formed through coordination bonds, so that the adhesive force of the polymer electrolyte to the pole piece is improved.

In step S20 of this embodiment, if the first compound is mixed with at least one monomer and heated to cause polymerization, a polymer containing a flexible block can be obtained; when the first compound is mixed with at least one kind of rigid block molecular chain and heated to cause polymerization reaction, a polymer containing a rigid block can be obtained.

In some embodiments, the capping agent is selected from at least one of a dipyridyl cycloalkene, a bromodipyridyl cyclohexene;

in some embodiments, the oxidizing agent is selected from at least one of meta-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., and is not limited thereto. The end-capping reagent can generate oxidation reaction under the action of an oxidant to generate an end-capping compound with a pyridine group and an epoxy group.

In some embodiments, the oxidation reaction temperature is 30 ℃ to 100 ℃, and the oxidation reaction time is 2h to 10 h; the reaction temperature may be 30 ℃, 40 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃ or 100 ℃ and the like, and the reaction time may be 2h, 3h, 4h, 5h, 6h, 7h, 8h or 10h and the like, which is not limited herein. By controlling the temperature and time of the oxidation reaction, the end-capping compound with pyridine groups and epoxy groups can be generated, and the reaction efficiency can be 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 (2-100): 100 may be 2:100, 5:100, 10:100, 20:100, 40:100, 50:100, 60:100, 70:100, 80:100, or 100:100, and the like, which is not limited herein.

In some embodiments, the monomer is selected from at least one of a carbonate, an alkenoic acid ester, a heterocyclic ketone, a siloxane, a glycol; specifically, the carbonate may be propylene carbonate, the heterocyclic ketone may be 4-ethyldioxolanone, the alkenoic acid ester 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 polyethylene glycol having a hydroxyl group, a poly-n-butyl acrylate having a hydroxyl group, a polydimethylsiloxane having a hydroxyl group, a polypropylene carbonate having a hydroxyl group, or 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 temperature is 60 ℃ to 160 ℃, the polymerization time is 5h to 30h, specifically 60 ℃, 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 140 ℃ or 160 ℃ and the like, and the polymerization time can be 5h, 6h, 7h, 8h, 9h, 10h, 15h, 20h, 30h and the like, which are not limited herein.

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 adiponitrile.

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

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

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

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 second polymerization reaction is 80 ℃ to 160 ℃, the time of the second polymerization reaction is 5h to 20h, specifically 80 ℃, 90 ℃, 100 ℃, 110 ℃, 120 ℃, 140 ℃ or 160 ℃ and the like, and the time of the second polymerization reaction can be 5h, 6h, 7h, 8h, 9h, 10h, 15h, 20h and the like, which are not limited herein.

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

step S100, dissolving a polymer in an organic solvent, heating and stirring to dissolve the polymer, so as to obtain a gel polymer;

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

step S300, soaking the polymer film in an 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 substituted or unsubstituted hydrogen, alkyl, alkenyl, alkynyl, aryl, halogen; or, R ₂ And R ₃ Each independently selected from substituted or unsubstituted alkyl, and R ₂ And R ₃ Form a ring through C-C connection;

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

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

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

As an alternative embodiment of the present invention, the temperature of the heating and stirring is 30 ℃ to 70 ℃, specifically 30 ℃, 40 ℃, 45 ℃, 50 ℃, 55 ℃, 60 ℃, 65 ℃ or 70 ℃, and the like, and may be other values within the above range, which is not limited herein. The heating and stirring time is 1h to 4h, specifically 1h or 2h, and the like, and may be other values within the above range, which is not limited herein. The heating and stirring time is too short, which is not favorable for forming a gel polymer with uniform mixing.

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

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

As an alternative embodiment of the present invention, the temperature of the drying process is 50 ℃ to 150 ℃, specifically 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃, 120 ℃ or 150 ℃, and may be other values within the above range, which is not limited herein.

The drying time is 2h to 12h, specifically 2h, 3h, 4h, 5h, 6h, 8h, 10h, or 12h, and may be other values within the above range, which is not limited herein. It will be appreciated that by drying sufficiently, it is advantageous to form a dry polymer film.

Step S30 is to soak the polymer film in an electrolytic solution to obtain a film-like polymer electrolyte.

As an optional technical solution of the present application, the carbonate compound further includes an electrolyte, and the electrolyte includes an organic solvent and a 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, ethyl methyl carbonate, ethylene carbonate, propylene carbonate and butylene carbonate. It can be understood that the carbonate compound has a carbonate group, and the polar group (e.g., the 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 invention, the content of the carbonate compound in the electrolyte solution may be 30% to 95% by mass, specifically 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, or 95%, and may be other values within the above range, which is not limited herein.

As an alternative solution, the lithium salt includes at least one of lithium hexafluorophosphate, lithium tetrafluoroborate, lithium difluorophosphate, lithium bistrifluoromethanesulfonylimide, lithium bis (fluorosulfonyl) imide, lithium bisoxalato borate, or lithium difluorooxalato borate.

As an alternative embodiment of the present invention, 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, and the like, and may be other values within the above range, which is not limited herein.

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

In a fifth aspect, embodiments of the present application 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 be soaked and swelled.

In some embodiments, the amount of the electrolyte solution is 10% to 90% of the total mass of the polymer electrolyte, specifically 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, or 90%, and the like, and may be other values within the above range. The electrolyte content is too high, which is beneficial to improving the ionic conductivity of the polymer electrolyte but not beneficial to improving the caking property; if the electrolyte content is too low, the polymer electrolyte is too dry to exhibit the adhesive properties of the polymer. Preferably, the dosage of the electrolyte is 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 plate may be lithium cobaltate, lithium iron phosphate, ternary material, etc., and the negative active material in the negative electrode plate may be metallic lithium, graphite, silicon-based negative electrode, etc., which are not limited herein.

The following examples are intended to illustrate the invention in more detail. The embodiments of the present invention are not limited to the following specific embodiments. The present invention can be modified and implemented as appropriate within the scope of the main claim.

Example 1

(1) Respectively dissolving about 25g of 3, 6-dipyridyl-1, 4-cyclohexadiene and 17g of m-chloroperoxybenzoic acid in 500mL of dichloromethane, heating and uniformly mixing at 50 ℃, and stirring for reacting for 4 hours. Filtering the mixture by a silica gel column, and performing rotary evaporation to obtain the compound A.

(2) Dissolving a compound A in 100g of carbonate monomer (propylene carbonate) in a nitrogen atmosphere, adding 2g of potassium bicarbonate and 5g of hydroquinone, heating at the reaction temperature of 150 ℃, cooling to room temperature, filtering to obtain a yellow solution in an anhydrous and oxygen-free manner, adding 80g of polyethylene with carboxyl at two ends and 100mL of toluene into the solution, heating at the temperature of 120 ℃, reacting for 10 hours, carrying out azeotropic condensation to remove water, passing the product in a reaction bottle through a silica gel column, carrying out rotary evaporation, and drying to obtain a yellow product, thereby obtaining a polymer P1.

(3) The polymer P is ₁ (n ₁ ＝20，n ₂ ＝30，R ₁ Methyl group) in anhydrous dichloromethane (polymer mass: the mass ratio of the solvent is 1 g: 10mL) is heated to 60 ℃, fully stirred and dissolved, the solution is dripped into a polytetrafluoroethylene mold, dry nitrogen is blown to accelerate solvent volatilization to form a film, and after the polymer is dried to form a film, the film is placed in a vacuum oven to be dried for 12 hours at 90 ℃ 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 minus 40 ℃), the prepared polymer film is superposed with a positive pole piece containing a high-nickel ternary material and a metal lithium negative pole, and then lithium salt LiPF is injected ₆ 1g of electrolyte (the concentration is 1.2mol/L) and dimethyl carbonate/ethylene carbonate (the mass ratio is 1: 1), standing for 48 hours, and assembling the battery.

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

Example 2

Compared with example 1, the difference is that:

(2) dissolving the compound A in 100g of 4-ethyl dioxy heterocyclic pentanone under the nitrogen atmosphere, adding 2g of potassium bicarbonate and 5g of hydroquinone, reacting at the temperature of 150 ℃, heating for 15 hours, cooling to room temperature, and filtering without water and oxygen to obtain a yellow solutionAdding 80g of polyethylene with carboxyl at two ends and 100mL of toluene into the solution, heating to 120 ℃, reacting for 10h, removing water by azeotropic condensation, passing the product in a reaction bottle through a silica gel column, performing rotary evaporation, and drying to obtain a yellow product, thus obtaining the 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 resulting polymer film are shown in Table 1.

Example 3

Compared with example 1, the difference is that:

(2) dissolving the compound A in 50g of carbonate monomer (propylene carbonate) in nitrogen atmosphere, adding 2g of potassium bicarbonate and 5g of hydroquinone, heating at the reaction temperature of 150 ℃ for 15h, cooling to room temperature, filtering in anhydrous and oxygen-free manner to obtain yellow solution, adding polyethylene (n) with carboxyl at two ends into the solution ₂ 40)110g and 150mL of toluene, heating to 120 ℃, reacting for 10h, removing water by azeotropic condensation, passing the product in the reaction bottle through a silica gel column, performing rotary evaporation, and drying to obtain a yellow product, thus obtaining the 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 resulting polymer film are shown in Table 1.

Example 4

Compared with example 1, the difference is that:

(2) dissolving the compound A in 25g of carbonate monomer (propylene carbonate) in nitrogen atmosphere, adding 2g of potassium bicarbonate and 5g of hydroquinone, reacting at 150 ℃, heating for 15h,cooling to room temperature, filtering without water and oxygen to obtain a yellow solution, adding 600g of polyethylene (n2 ═ 200) with carboxyl at two ends and 800mL of toluene into the solution, heating to 120 ℃, reacting for 10h, carrying out azeotropic condensation to remove water, passing the product in a reaction bottle through a silica gel column, carrying out rotary evaporation and drying to obtain a yellow product, and obtaining the polymer P4(n 3578 ═ 200) ₁ ＝5，n ₂ ＝200)。

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

Example 5

Compared with example 1, the difference is that:

(2) dissolving a compound A in 500g of carbonate monomer (propylene carbonate) under a nitrogen atmosphere, adding 20g of potassium bicarbonate and 50g of hydroquinone, reacting at 150 ℃, heating for 15h, cooling to room temperature, filtering without water and oxygen to obtain a yellow solution, adding 30g of polyethylene (n2 ═ 10) with carboxyl groups at two ends and 40mL of toluene into the solution, heating at 120 ℃, reacting for 10h, carrying out azeotropic condensation to remove water, passing the product in a reaction bottle through a silica gel column, carrying out rotary evaporation and drying to obtain a yellow product, and obtaining a polymer P5(n 5) 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.

Example 6

Compared with example 1, the difference is that:

(4) in a drying room (the relative humidity is lower than 2 percent, the dew point is lower than minus 40 ℃), the prepared polymer film (polymer P1) is superposed with a positive pole piece containing a high-nickel ternary material and a metal lithium negative pole, and then lithium-containing salt LiPF is injected ₆ 4g of an electrolyte solution (concentration: 1.2mol/L) of dimethyl carbonate/ethylene carbonate (mass ratio: 1), and the mixture was left to standAnd 48h, assembling the battery.

This example gives polymer P1, the properties of the resulting polymer film being shown in Table 1.

Example 7

Compared with example 1, the difference is that:

in a drying room (the relative humidity is lower than 2 percent, the dew point is lower than minus 40 ℃), the prepared polymer film (polymer P1) is superposed with a positive pole piece containing a high-nickel ternary material and a metal lithium negative pole, 1g of electrolyte containing lithium salt LiFSI (the concentration is 1.2mol/L) and ethyl methyl carbonate/dimethyl carbonate/propylene carbonate (the mass ratio is 2: 2: 1) is injected, and the battery is assembled after standing for 48 hours.

Example 8

Compared with example 1, the difference is that:

(1) respectively dissolving 30g of 3, 6-dipyridyl-4-bromo-1-cyclohexene, 10g of hydrogen peroxide and 0.1g of methyl rhenium trioxide in 500mL of dichloromethane, heating and mixing uniformly at 40 ℃, stirring for reacting for 4 hours, filtering by a silica gel column, and performing rotary evaporation to obtain a compound A.

(2) Dissolving a compound A in 100g of polydimethylsiloxane with hydroxyl at the tail end in a nitrogen atmosphere, adding 3g of potassium carbonate and 500g of acetonitrile, heating at the reaction temperature of 80 ℃, 24h, cooling to room temperature, filtering, performing rotary evaporation to obtain a yellow product, adding the product into 80g of parylene with carboxyl at two ends and 100mL of toluene, heating at the temperature of 120 ℃, reacting 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, thus obtaining a polymer P6(n is obtained (n is ₁ ＝25，n ₂ ＝15)。

The structural formula of the polymer P6 obtained in this example is shown below, and the properties of the resulting 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 methyltrioxorhenium were each dissolved in 500mL of dichloromethane, and the resulting solution was added

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

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

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

Example 10

(1) 30g of 3, 6-dipyridyl-4-bromo-1-cyclohexene, 10g of hydrogen peroxide and 0.1g of methyltrioxorhenium were dissolved in 500mL of dichloromethane, and the mixture was heated and mixed uniformly at 40 ℃ and reacted for 4 hours with stirring. Filtering the mixture by a silica gel column, and performing rotary evaporation to obtain the compound A.

(2) Dissolving the compound A in 100g of polyethylene glycol with hydroxyl at the tail end under the nitrogen atmosphere, adding 3g of potassium carbonate and 500g of acetonitrile, reacting at the temperature of 80 ℃, heating for 24h, cooling to room temperature, filtering, and carrying out rotary evaporation to obtain a yellow product;

(3) adding the product into 80g of polypropylene with carboxyl at two ends and 100mL of toluene, heating to 120 ℃, reacting for 10h, carrying out azeotropic condensation to remove water, passing the product in a reaction bottle through a silica gel column, carrying out rotary evaporation, 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 resulting polymer film are shown in Table 1.

Example 11

Compared with example 1, the difference is that:

(2) dissolving the compound A in 100g of carbonate monomer (propylene carbonate) in a nitrogen atmosphere, adding 2g of potassium bicarbonate and 5g of hydroquinone, heating at the reaction temperature of 150 ℃ for 15h, cooling to room temperature, filtering in anhydrous and oxygen-free manner to obtain a yellow solution, and performing rotary evaporation and drying to obtain a yellow product, namely a polymer P9.

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

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

Example 12

Compared with example 1, the difference is that:

(2) dissolving the compound A in 80g of polyethylene with carboxyl at two ends and 100mL of toluene in a nitrogen atmosphere, adding 2g of potassium bicarbonate and 5g of hydroquinone, reacting at 150 ℃, heating for 15h, 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 P10.

The molecular chain of the polymer P10 has no flexible block, and the molecular chain has only a polyethylene block and has no polycarbonate block, namely n1 is 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-dipyridyl-1, 3-cyclopentadiene and 17g of m-chloroperoxybenzoic acid were dissolved in 500mL of dichloromethane, heated and mixed uniformly at 50 ℃ and reacted for 4 hours with stirring. Filtering the mixture by a silica gel column, and performing rotary evaporation to obtain the compound A. Polymer P11 (n) obtained in this example ₁ ＝20，n ₂ ═ 30) is as follows, and the properties of the resulting polymer film are shown in table 1.

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, reacting at the temperature of 150 ℃, heating for 15h, cooling to room temperature, filtering without water and oxygen to obtain a yellow solution, adding 80g of polyethylene with carboxyl groups at two ends and 100mL of methylbenzene into the solution, heating at the temperature of 120 ℃, reacting for 10h, removing water by azeotropic condensation, 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) Ion conductivity test method:

a sample of the polymer electrolyte membrane was sandwiched between two stainless steel sheets and placed in a 2016 type cell housing, and the lithium ion conductivity was measured by electrochemical ac impedance spectroscopy at an electrochemical workstation (BioLogic Science Instruments) in a frequency range of 0.1Hz to 100kHz, according to σ ═ L/(R × S), σ is the ionic conductivity, L is the electrolyte thickness, S is the area of the electrolyte membrane in contact with the electrode, and R is the impedance measured by an impedance meter.

(2) Test method of electrochemical stability window:

a sample of the polymer electrolyte membrane was sandwiched between a stainless steel sheet and a lithium sheet, and placed in a 2016 type battery case, and an electrochemical working window was measured by linear voltammetric scanning using an electrochemical workstation (BioLogic Science Instruments) at an initial potential of open circuit voltage, a maximum potential of 6V, and a scanning speed of 10 mV/s.

(3) The test method of the transference number of the lithium ions comprises the following steps:

and (3) representing the transference number of the lithium ions by using a timing current steady state method. Specifically, a button-type symmetric non-blocking cell was assembled by sandwiching a polymer electrolyte membrane sample with two lithium sheets, placed in a 2016 cell housing, and tested in a VSP potentiostat (BioLogic Science Instruments) electrochemical workstation. In an initial state, under a constant voltage delta V (set to be 10mV), charged substances in a system can migrate, a concentration difference starts to be formed between two electrodes, and an initial current Io is recorded; as time goes on, the concentration difference between the two electrodes increases, the ion migration slows down, and the current decreases, a process called polarization; when steady state is reached, only cations migrate and the steady state current Iss is recorded at this time. Before and after the timing current test, the battery Iss in an initial state and a steady state needs to be tested respectively, and corresponding impedances Ro and Rss are recorded.

According to the formula

The transference number of lithium ions is obtained.

(4) Test methods of peel strength and tensile strength of polymer electrolyte membrane:

the peel strength of the polymer gel electrolyte was measured by IPC-TM-6502.8 method using Peelerator Shimadzu AG-X50N. Wiping a mirror surface steel plate by alcohol, pasting a double-sided adhesive tape on a mirror surface copper plate, ensuring that the adhesive tape is firmly bonded with the steel plate without air bubbles in the adhesive tape pasting process, coating polymer gel electrolyte on a pole piece, cutting the coated pole piece into small strips with the thickness of 25mm × 220mm, bonding one side coated with the electrolyte on the steel plate by the double-sided adhesive tape, enabling the pole piece to be parallel to the steel plate, rolling 3 times back and forth by an automatic roller instrument, opening a stripping machine, setting the stripping speed to be 100mm/min, clamping the steel plate by a lower clamp, clamping the pole piece by an upper clamp, resetting, starting a test, testing each material for 5 times, and averaging. According to the formula: t ═ P/B, where T denotes peel strength (mN/mm), P is average peel force (mN), and B is sample test width (mm).

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 500 mm/min.

(5) Test method for A1/A2 of polymer

Opening infrared spectrometer, preheating for half an hour, uniformly coating dried polymer sample on transparent glass, directly placing sample test surface on ATR (attenuated total reflectance) sampler, rotating sampler fixing button, pressing sample against air background at 4000cm ^-1 -500cm ^-1 Scanning within the range, scanning for three times, and collecting the attenuated total reflection infrared spectrum of the sample to obtain the 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 is clear from the results in FIG. 1, the 2842cm infrared spectrum of the polymer electrolyte membrane obtained in example 1 was found to be ^-1 、1710cm ^-1 Infrared peaks corresponding to carbonate and methylene, respectively, and conversion to polymerThe optical structures are corresponding. As can be seen from the results of fig. 2, the polymer electrolyte thin film has high lithium ion conductivity and can rapidly conduct lithium ions. From the results shown in fig. 3, the electrochemical stability window of the polymer electrolyte thin film shows that the polymer electrolyte has high voltage resistance, and can be used with high voltage electrode materials to improve the power and energy density of the battery. The results shown in fig. 4 show that 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, prevent separation during the cyclic expansion and contraction process, and improve the operation stability of the battery.

As is apparent from the data in Table 1, the lithium ion conductivity of the polymer electrolyte membranes of examples 1 to 10 was as high as 4.5X 10 ^-4 S/cm and above, the electrochemical window reaches 4.6V and above, and the ion transfer number reaches 0.42 and above.

The reason is that the epoxy three-membered ring group at the end of the polymer molecular chain in the polymer electrolyte can undergo a ring-opening reaction and react with metal ions in the electrode active material or groups such as hydroxyl on the surface of the diaphragm, and the reaction activity is extremely strong under the self-catalysis of aliphatic six-membered ring tension and pyridyl, so that the interface of the polymer electrolyte has high adhesion. Under the interface voltage of the pole piece and the electrolyte in the charging and discharging processes of the battery, the pyridine group at the tail end of the polymer molecular chain is induced to initiate the epoxy group to generate ring-opening polymerization to form a chemical bond, so that firm adhesion is generated.

The polymer molecular chain in the polymer electrolyte contains a large number of carbonate structural units, so that the flexibility is high, the bonding capability of the polymer molecular chain can be improved, and the adhesive force of the groups at the tail end of the molecular chain and the interfaces of pole pieces and the like can be improved; and the carbonate structural unit can be mutually adsorbed with carbonates with similar structures in an 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 on 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 polyethylene block has low reaction activity, the pressure resistance and the safety performance of the polymer film can be improved, electrolyte cannot be embedded into and permeate 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 ordered structure is promoted, and the concentration and the migration rate of lithium ions in an amorphous area are improved.

Whereas the polymer molecular chain P9 in example 11 has only a flexible block (polycarbonate block) and no rigid block, the flexibility of the polymer molecular chain is greatly reduced, and the tensile strength and peel strength of the polymer electrolyte are reduced compared to example 1.

The polymer molecular chain P10 in example 12 has only a rigid block (polyethylene block) and no flexible block, the molecular chain structure is regular, the dissolving and absorbing capacity for the electrolyte is greatly reduced, the lithium ion conductivity is greatly reduced, the molecular chain lacks the flexible block, the flexibility is reduced, and the peel strength is reduced compared with example 1.

In the comparative example 1, the two ends of the polymer molecular chain P11 have no epoxy group and pyridine group, and only have a polyethylene block and a polycarbonate block, so that the complexation of the polymer molecular chain and the active substance on the pole piece is reduced, the tensile strength and the peel strength of the polymer electrolyte are reduced, and the adhesion of the polymer electrolyte to the pole piece is reduced.

Although the present application has been described with reference to the preferred embodiments, it is not intended to limit the scope of the claims, and many possible variations and modifications may be made by one skilled in the art without departing from the spirit of the present application.

Claims

1. A polymer comprising a polymer backbone and end-capping groups, wherein the end-capping groups comprise a pyridine group and an epoxy group.

2. The polymer according to claim 1, wherein the molecular chain of the polymer has a triblock structure, wherein the triblock structure is a flexible block having the end-capping group-a rigid block-a flexible block having the end-capping group.

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

a. the flexible block is selected from polypropylene carbonate, polydimethylsiloxane, poly (n-butyl acrylate) and polyethylene glycol;

b. the rigid block is selected from a polyethylene block, a polypropylene block, a polyacetylene block, a parylene block and polyphenyl ether;

c. the structural formula of the polymer is shown as the following formula I:

4. The polymer of claim 3, wherein the polymer satisfies at least one of the following characteristics:

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

b.R ₄ any one of vinyl, propenyl, ethynyl, p-xylyl and phenyl ether;

c.n ₁ the value range is between 10 and 50; n is ₂ A range of values between 20 and 80;

d. the structural formula of the polymer is shown as the following formula I-1:

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

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

6. The polymer electrolyte according to claim 5, wherein the molecular chain of the polymer has a triblock structure, which is a flexible block having an end capping group-a rigid block-a flexible block having an end capping group; in the infrared light absorption spectrum, the repeating unit in the flexible block of the polymer has a wavelength of 3000cm ^-1 ～600cm ^-1 The maximum light transmission peak intensity in the range is A ₁ The repeating unit in the rigid block of the polymer has a wavelength of 3000cm ^-1 ～600cm ^-1 The maximum light transmission peak intensity in the range is A ₂ (ii) a 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％。

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

a. the polymer electrolyte is a polymer electrolyte membrane;

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

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

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

8. A method of making a polymer, the method comprising:

and 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.

9. The method of claim 8, wherein the method satisfies at least one of the following characteristics:

a. the end capping agent is selected from at least one of dipyridyl cyclic olefin and bromo dipyridyl cyclohexene;

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

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

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

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

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

g. the monomer is selected from at least one of carbonate, alkenoic acid ester, siloxane and glycol;

h. the rigid block molecular chain is selected from at least one of polyethylene, parylene, polyphenylene oxide and polypropylene;

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

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

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

said step of mixing said 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;

the initiator comprises at least one of a carbonate, a bisphenol, and a nitrile;

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

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

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

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

10. A lithium ion battery comprising the polymer electrolyte according to any one of claims 4 to 9.