Unsaturated zwitterion-based polymer, unsaturated zwitterion-based polymer membrane, preparation method and application thereof, and lithium-ion battery

Abstract

The present invention provides an unsaturated zwitterionic polymer, an unsaturated zwitterionic polymer membrane, a preparation method and application thereof, and a lithium-ion battery. The unsaturated zwitterionic polymer provided herein comprises the following raw materials, calculated by weight: 40-70 parts of a polymerizable monomer, 0.1-1 part of a crosslinking agent, 1-10 parts of an unsaturated zwitterionic compound, 20-30 parts of a lithium salt, 5-20 parts of a plasticizer, and 0.1-1 part of an initiator; the crosslinking agent contains an imino group and an unsaturated group. In the present invention, the unsaturated zwitterionic polymer has high ionic conductivity, a wide electrochemical window, and excellent thermal stability. When assembled into a lithium-ion battery using the unsaturated zwitterionic polymer as a solid electrolyte, the resulting lithium-ion battery exhibits improved rate performance and cycling performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium ion batteries, and in particular relates to an unsaturated zwitterion-based polymer, an unsaturated zwitterion-based polymer film, a preparation method and application thereof, and a lithium ion battery. Background Art

[0002] Lithium-ion batteries (LIBs) are batteries with high energy density and long life. They have been widely studied and applied in energy storage devices such as portable electronic products and electric vehicles.

[0003] The electrolytes used in lithium-ion batteries are divided into two categories. One is traditional liquid electrolytes. Although widely used, these liquid electrolytes have safety issues such as leakage and flammability, which have hindered the mass production of lithium-ion batteries. The other is solid electrolytes. Solid electrolytes are non-leakage, non-flammable and non-explosive, and highly safe. Solid-state lithium-ion batteries built based on solid electrolytes fundamentally address the safety issues of traditional liquid lithium-ion batteries and have excellent application prospects.

[0004] Solid-state polymer electrolytes (SPEs) are promising due to their safety, flexibility, scalability, and interfacial compatibility. Polyethylene oxide (PEO) is a commonly used SPE. However, existing SPEs suffer from low ionic conductivity and poor thermal stability, resulting in poor electrochemical performance of solid-state lithium-ion batteries constructed using these electrolytes. Summary of the Invention

[0005] The present invention aims to provide an unsaturated zwitterionic polymer, an unsaturated zwitterionic polymer membrane, a preparation method and application thereof, and a lithium-ion battery. The unsaturated zwitterionic polymer provided by the present invention has high ionic conductivity, a wide electrochemical window, and excellent thermal stability. When used as an electrolyte in a lithium-ion battery, it can improve the rate capability and cycle performance of the lithium-ion battery.

[0006] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0007] The present invention provides an unsaturated zwitterionic polymer, which comprises the following raw materials, calculated by weight:

[0008] 40-70 parts of polymerizable monomers, 0.1-1 parts of crosslinking agents, 1-10 parts of unsaturated zwitterionic compounds, 20-30 parts of lithium salts, 5-20 parts of plasticizers and 0.1-1 parts of initiators; the crosslinking agent contains imino groups and unsaturated groups.

[0009] Preferably, the cross-linking agent includes at least one of acrylamide, N,N-methylenebisacrylamide and polyethylene glycol-bisurethane dimethacrylate; and the polymerizable monomer is a polyethylene glycol acrylate monomer.

[0010] Preferably, the polyethylene glycol acrylate monomer includes at least one of methoxy polyethylene glycol acrylate, ethylene glycol monomethyl ether acrylate and polyethylene glycol methyl ether methacrylate;

[0011] The number average molecular weight of the methoxy polyethylene glycol acrylate is 480 to 10,000; the number average molecular weight of the polyethylene glycol methyl ether methacrylate is 300 to 4,000.

[0012] Preferably, the unsaturated zwitterionic compound comprises at least one of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonatepropyl)ammonium hydroxide, 2-methacryloyloxyethylphosphocholine, and 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate;

[0013] The lithium salt includes at least one of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethanesulfonyl)imide, lithium nitrate, lithium difluorophosphate, and lithium difluorooxalatoborate; the plasticizer includes at least one of ethylene carbonate, propylene carbonate, tetraethylene glycol dimethyl ether, 1-n-butyl-3-methylimidazolium hexafluorophosphate, and 1-allyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide;

[0014] The initiator includes at least one of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-hydroxy-2-methyl-1-phenylpropanone and 1-hydroxycyclohexylphenylketone.

[0015] The present invention provides an unsaturated zwitterion-based polymer membrane, comprising a base membrane and a polymer loaded on the base membrane; the polymer is the unsaturated zwitterion-based polymer described in the above technical solution.

[0016] Preferably, the base membrane is a polyethylene membrane, a polypropylene membrane, a cellulose membrane, a glass fiber membrane, a polyvinylidene fluoride membrane or a polyacrylonitrile membrane; and the loading amount of the polymer on the unsaturated zwitterionic polymer membrane is 85% to 95%.

[0017] The present invention provides a method for preparing the unsaturated zwitterion-based polymer membrane described in the above technical solution, comprising the following steps:

[0018] The base film is immersed in a precursor solution for immersion treatment, and the obtained immersed base film is irradiated with light to in situ polymerize the base film to generate an unsaturated zwitterionic polymer to obtain the unsaturated zwitterionic polymer film; the precursor solution includes the raw materials for preparing the unsaturated zwitterionic polymer described in the above technical solution.

[0019] Preferably, the immersion treatment time is 10 to 20 minutes; the light source of the light irradiation is ultraviolet light, the wavelength of the ultraviolet light is 200 to 380 nm; the light irradiation time is 10 to 60 minutes, and the light intensity of the light irradiation is 50 to 200 mW / cm 2 .

[0020] The present invention provides the use of the unsaturated zwitterion-based polymer described in the above technical solution, the unsaturated zwitterion-based polymer film described in the above technical solution, or the unsaturated zwitterion-based polymer film obtained by the preparation method described in the above technical solution as a solid electrolyte in a lithium-ion battery.

[0021] The present invention provides a lithium-ion battery comprising a positive electrode, a negative electrode and a solid electrolyte; the solid electrolyte is the unsaturated zwitterion-based polymer described in the above technical solution, the unsaturated zwitterion-based polymer film described in the above technical solution, or the unsaturated zwitterion-based polymer film obtained by the preparation method described in the above technical solution.

[0022] The present invention provides an unsaturated zwitterionic polymer, which comprises the following raw materials in parts by mass: 40 to 70 parts of polymer monomers, 0.1 to 1 part of cross-linking agent, 1 to 10 parts of unsaturated zwitterionic compound, 20 to 30 parts of lithium salt, 5 to 20 parts of plasticizer and 0.1 to 1 part of initiator; the cross-linking agent contains imino groups and unsaturated groups. In the present invention, the imino groups in the cross-linking agent have a strong ability to form hydrogen bonds, and there are groups (COC) that can form hydrogen bonds in the structures of the unsaturated zwitterionic compound and the polymerized monomer, thereby forming physical cross-linking points with the unsaturated zwitterionic compound and the polymerized monomer, forming dynamic hydrogen bonds, which can improve the mechanical properties of the unsaturated zwitterionic polymer; at the same time, the obtained unsaturated zwitterionic polymer can have a certain viscoelasticity and can withstand the volume change of the lithium negative electrode during the operation of the lithium-ion battery. At the same time, the polymerized monomer, the unsaturated zwitterionic compound and the plasticizer form a main chain through polymerization reaction, and the positive charge center of the zwitterionic reacts with the anion in the lithium salt to limit the migration of the anion and promote the Li + The migration of anions and Li + The joint regulation of Li +The unsaturated zwitterion-based polymer prepared on this basis can construct a unique zwitterion nanochannel through the synergistic effect of ion-dipole interaction and dynamic hydrogen bonding, resulting in uniform deposition of lithium ions. The dynamic network energy dissipation is beneficial to the anti-puncture of lithium dendrites, thereby effectively inhibiting the growth of lithium dendrites. Furthermore, the present invention uses the unsaturated zwitterion and the anion in the lithium salt, Li + The ion-dipole interaction between the cations in the plasticizer (ionic liquid) constructs the nanochannel of unsaturated zwitterions. Specifically, the ion-dipole interaction can adjust the arrangement of polymer segments, acting as an ion transport channel to promote ion transport. The introduction of ionic liquid promotes the dissociation of lithium salts, thereby improving Li + The ether oxygen segments in the polymerized monomers promote the transport of Li + The synergistic effect of the three can accelerate the transport of lithium ions, improve ionic conductivity, and thus make the resulting unsaturated zwitterionic polymer have high ionic conductivity, a wide electrochemical window, and excellent thermal stability. When the unsaturated zwitterionic polymer of the present invention is used as the electrolyte of a lithium-ion battery, it is beneficial to improve the rate performance and cycle performance of the lithium-ion battery.

[0023] The present invention provides an unsaturated zwitterionic polymer membrane, comprising a base membrane and an unsaturated zwitterionic polymer loaded on the base membrane. In the present invention, the base membrane plays a supporting role, allowing the unsaturated zwitterionic polymer to cover the base membrane, thereby improving the mechanical properties of the unsaturated zwitterionic polymer membrane and improving the anti-dendrite ability of the unsaturated zwitterionic polymer membrane; the carbon-carbon double bonds and imino groups of the crosslinking agent in the unsaturated zwitterionic polymer can form chemical crosslinking points and physical crosslinking points between the unsaturated zwitterionic compound and the polymerized monomer, thereby making the obtained unsaturated zwitterionic polymer membrane have a certain viscoelasticity. When it is assembled into a lithium-ion battery as a solid electrolyte, it can withstand the volume change of the lithium negative electrode during the operation of the lithium-ion battery. The unsaturated zwitterionic polymer membrane provided by the present invention has high ionic conductivity, a wide electrochemical window, excellent thermal stability and excellent interfacial compatibility, and can be used in a wide temperature range. The results of the examples show that the room temperature ionic conductivity of the unsaturated zwitterionic polymer membrane provided by the present invention is 5.35×10 -5 ~12.8×10 -5 S / cm -1 , the anti-oxidation potential is 4.9~5.0V, and the lithium ion migration number is 0.29~0.53.

[0024] The present invention provides a lithium-ion battery, comprising a positive electrode, a negative electrode and a solid electrolyte; the solid electrolyte is the unsaturated zwitterionic polymer or the unsaturated zwitterionic polymer membrane described in the above technical solution. In an embodiment of the present invention, a 2025-type button-type lithium-ion battery (LFP / / Li battery) is assembled using an unsaturated zwitterionic polymer membrane. The LFP / / Li battery is subjected to charge and discharge cycles at different rates at 25°C using a Xinwei battery cycling system. The results show that at room temperature and at a rate of 0.1C, the specific capacity of the LFP / / Li battery is 159mAh / g; at a rate of 0.2C, the specific capacity of the LFP / / Li battery is 158mAh / g; at a rate of 0.5C, the specific capacity of the LFP / / Li is 152mAh / g. g; at a 1C rate, the specific capacity of the LFP / / Li battery was 143 mAh / g; at a 2C rate, the specific capacity of the LFP / / Li battery was 124 mAh / g. When the rates returned to 1C, 0.5C, and 0.2C, the specific capacity of the LFP / / Li battery could still reach 145 mAh / g, 151 mAh / g, and 154 mAh / g, respectively. At a high rate of 0.5C, the first-cycle discharge capacity of the LFP / / Li battery was 143.77 mAh / g, and after 735 cycles, the capacity retention rate was 91%. This shows that the lithium-ion battery of the present invention has excellent rate performance and cycling stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0026] Figure 1 This is a SEM image of the unsaturated zwitterion-based polymer membrane prepared in Example 1;

[0027] Figure 2 This is a temperature-dependent impedance diagram of the unsaturated zwitterion-based polymer membrane prepared in Example 1;

[0028] Figure 3 This is a linear sweep voltammetry curve of the unsaturated zwitterion-based polymer film prepared in Example 1;

[0029] Figure 4 This is a thermogravimetric curve of the unsaturated zwitterion-based polymer membrane prepared in Example 1;

[0030] Figure 5 1 is a stress-strain curve of the unsaturated zwitterion-based polymer film obtained in Example 1;

[0031] Figure 6 It curve of Li / / Li symmetric battery prepared based on unsaturated zwitterionic polymer and impedance spectrum before and after battery polarization;

[0032] Figure 7 The Li / / Li symmetric battery based on unsaturated zwitterionic polymer was prepared at a current density of 0.1 mA·cm -2 The voltage versus time curve at ;

[0033] Figure 8 This is the rate cycle diagram of the LFP / unsaturated zwitterionic polymer / Li battery assembled in Example 2. DETAILED DESCRIPTION

[0034] The present invention provides an unsaturated zwitterionic polymer, which comprises the following raw materials, calculated by weight:

[0035] 40-70 parts of polymerizable monomers, 0.1-1 parts of crosslinking agents, 1-10 parts of unsaturated zwitterionic compounds, 20-30 parts of lithium salts, 5-20 parts of plasticizers and 0.1-1 parts of initiators; the crosslinking agent contains imino groups and unsaturated groups.

[0036] In the present invention, unless otherwise specified, the raw materials used are commercially available products well known to those skilled in the art or are prepared using methods well known to those skilled in the art.

[0037] The raw materials for preparing the unsaturated zwitterionic polymer described in the present invention include 40 to 70 parts by weight of a polymerizable monomer. In specific embodiments of the present invention, the polymerizable monomer comprises 40, 50, 60, or 70 parts by weight. In the present invention, the polymerizable monomer may be a polyethylene glycol acrylate monomer; the polyethylene glycol acrylate monomer may include at least one of methoxy polyethylene glycol acrylate, ethylene glycol monomethyl ether acrylate, and polyethylene glycol methyl ether methacrylate. In specific embodiments of the present invention, the polymerizable monomer is methoxy polyethylene glycol acrylate, ethylene glycol monomethyl ether acrylate, or polyethylene glycol methyl ether methacrylate. The number average molecular weight of the methoxy polyethylene glycol acrylate described in the present invention may be 480 to 10,000. In specific embodiments of the present invention, the number average molecular weight of the methoxy polyethylene glycol acrylate is 480, 1,000, or 2,000. The number average molecular weight of the polyethylene glycol methyl ether methacrylate of the present invention can be 300 to 4000; in a specific embodiment of the present invention, the number average molecular weight of the polyethylene glycol methyl ether methacrylate is 300, 950 or 2000. In the present invention, the polymerized monomer, the unsaturated zwitterionic compound and the plasticizer form a main chain through a polymerization reaction, and the positive charge center of the zwitterionic compound interacts with the anion in the lithium salt to limit the migration of the anion and promote the Li +The migration of anions and Li + The joint regulation of Li + Uniform deposition; the unsaturated zwitterionic polymer prepared on this basis can construct unique zwitterionic nanochannels through the synergistic effect of ion-dipole interaction and dynamic hydrogen bonding, resulting in uniform deposition of lithium ions. The dynamic network energy dissipation is beneficial to the anti-puncture resistance of lithium dendrites, thereby effectively inhibiting the growth of lithium dendrites.

[0038] The raw materials for preparing the unsaturated zwitterionic polymer of the present invention include 0.1 to 1 parts by weight of the polymerizable monomers; in specific embodiments of the present invention, the weight of the crosslinking agent is 0.2 parts, 0.3 parts, 0.6 parts, 0.8 parts, or 1 part. In the present invention, the crosslinking agent contains an imino group and an unsaturated group; the crosslinking agent may include at least one of acrylamide, N,N-methylenebisacrylamide, and polyethylene glycol-bisurethane dimethacrylate; in specific embodiments of the present invention, the crosslinking agent is acrylamide, N,N-methylenebisacrylamide, or polyethylene glycol-bisurethane dimethacrylate. In the present invention, the NH bonds in the cross-linking agent can form hydrogen bonds, and the unsaturated zwitterionic compound and the polymerized monomer structure contain groups (COC) that can form hydrogen bonds. Therefore, physical cross-linking points can be formed between the unsaturated zwitterionic compound and the polymerized monomer, forming dynamic hydrogen bonds, which can improve the mechanical properties of the unsaturated zwitterionic polymer; at the same time, the obtained unsaturated zwitterionic polymer can also have a certain viscoelasticity, which can withstand the volume change of the lithium negative electrode during the operation of the lithium-ion battery.

[0039] Based on the mass fraction of the polymerized monomer, the raw materials for preparing the unsaturated zwitterionic polymer of the present invention include 1 to 10 parts of unsaturated zwitterionic compounds; in a specific embodiment of the present invention, the mass fraction of the unsaturated zwitterionic compounds is 1 part, 3 parts, 5 parts, 7 parts or 10 parts. In the present invention, the unsaturated zwitterionic compound may include at least one of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl)ammonium hydroxide, 2-methacryloyloxyethyl phosphorylcholine and 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate; in a specific embodiment of the present invention, the unsaturated zwitterionic compound is [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl)ammonium hydroxide, 2-methacryloyloxyethyl phosphorylcholine or 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate. The present invention reacts the unsaturated zwitterionic compound with the anion in the lithium salt, Li +The ion-dipole interaction between the cations in the ionic liquid constructs the nanochannel of unsaturated zwitterions. Specifically, the ion-dipole interaction can adjust the arrangement of the polymer chain segments, acting as an ion transport channel to promote ion transport. The introduction of the plasticizer (ionic liquid) promotes the dissociation of the lithium salt, thereby improving the Li + The ether oxygen segments in the polymerized monomers promote the transport of Li + The synergistic effect of the three can accelerate the transmission of lithium ions and improve the ionic conductivity, thereby making the obtained unsaturated zwitterionic polymer have higher ionic conductivity, wider electrochemical window and excellent thermal stability. Among them, the thermal stability data of the unsaturated zwitterionic polymer is as high as 300℃.

[0040] Based on the weight percentage of the polymerizable monomers, the raw materials for preparing the unsaturated zwitterionic polymer of the present invention include 20 to 30 parts by weight of a lithium salt. In specific embodiments, the weight percentage of the lithium salt is 20, 23, 26, or 30 parts. In the present invention, the lithium salt may include at least one of lithium bis(trifluoromethylsulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium nitrate, lithium difluorophosphate, and lithium difluorooxalatoborate. In specific embodiments, the lithium salt is a mixture of lithium bis(trifluoromethylsulfonyl)imide and lithium difluorooxalatoborate. In the present invention, when the lithium salt is a mixture of lithium bis(trifluoromethylsulfonyl)imide and lithium difluorooxalatoborate, the weight ratio of the lithium bis(trifluoromethylsulfonyl)imide to lithium difluorooxalatoborate may be 8 to 10:1. The present invention does not specifically limit the source of the lithium salt; commercially available products known to those skilled in the art may be used.

[0041] Based on the mass fraction of the polymerized monomers, the raw materials for preparing the unsaturated zwitterionic polymer of the present invention include 5 to 20 parts of a plasticizer; in a specific embodiment of the present invention, the mass fraction of the plasticizer is 5 parts, 10 parts, 15 parts or 20 parts. In the present invention, the plasticizer may include at least one of ethylene carbonate, propylene carbonate, tetraethylene glycol dimethyl ether, 1-n-butyl-3-methylimidazolium hexafluorophosphate and 1-allyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide; in a specific embodiment of the present invention, the plasticizer is ethylene carbonate, propylene carbonate, tetraethylene glycol dimethyl ether, 1-n-butyl-3-methylimidazolium hexafluorophosphate or 1-allyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide. In the present invention, the molar ratio of the unsaturated zwitterionic compound to the plasticizer can be 1:2 to 16; in specific embodiments of the present invention, the molar ratio of the unsaturated zwitterionic compound to the plasticizer is 1:2, 1:4, 1:6, 1:10, or 1:16. In the present invention, the plasticizer is a non-volatile ionic liquid that promotes the movement of polymer segments and the dissociation of lithium salts, significantly improving ionic conductivity without compromising safety. By limiting the molar ratio of the unsaturated zwitterionic compound to the plasticizer to the above range, the present invention can promote the construction of unsaturated zwitterionic nanochannels, accelerate the transport of lithium ions, and thereby improve ionic conductivity.

[0042] Based on the mass fraction of the polymerizable monomers, the raw materials for preparing the unsaturated zwitterionic polymer of the present invention include 0.1 to 1 parts of an initiator; in specific embodiments of the present invention, the mass fraction of the initiator is 0.1 parts, 0.3 parts, 0.6 parts, 0.8 parts, or 1 parts. The initiator of the present invention may be a photoinitiator. In the present invention, the initiator may include at least one of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-hydroxy-2-methyl-1-phenylpropanone, and 1-hydroxycyclohexylphenyl ketone; in specific embodiments of the present invention, the initiator is phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-hydroxy-2-methyl-1-phenylpropanone, or 1-hydroxycyclohexylphenyl ketone.

[0043] The main chain segment of the unsaturated zwitterionic polymer of the present invention is ether oxygen, wherein the number of repeating units of ether oxygen is 9.

[0044] The unsaturated zwitterionic polymer of the present invention has high ionic conductivity and a wide electrochemical window, and has excellent thermal stability; when used as an electrolyte for a lithium-ion battery, it is beneficial to improve the rate performance and cycle performance of the lithium-ion battery.

[0045] The present invention also provides an unsaturated zwitterion-based polymer membrane, comprising a base membrane and a polymer loaded on the base membrane; the polymer is the unsaturated zwitterion-based polymer described in the above technical solution.

[0046] In the present invention, the base membrane can be a polyethylene film (PE), a polypropylene film (PP), a cellulose film, a glass fiber membrane, a polyvinylidene fluoride (PVDF) membrane, or a polyacrylonitrile (PAN) membrane; in specific embodiments of the present invention, the base membrane can be a cellulose film or a glass fiber membrane. In the present invention, the base membrane plays a supporting role, allowing the unsaturated zwitterionic polymer to be coated on the base membrane, thereby improving the mechanical properties of the unsaturated zwitterionic polymer membrane and improving the anti-dendrite ability of the unsaturated zwitterionic polymer membrane. Furthermore, the present invention uses a base membrane with a large porosity, which allows the precursor solution to fully penetrate into the base membrane.

[0047] In the present invention, the loading amount of the polymer on the unsaturated zwitterion-based polymer membrane may be 85% to 95%. In a specific embodiment of the present invention, the loading amount of the polymer on the unsaturated zwitterion-based polymer membrane is 85%, 90% or 95%.

[0048] In the present invention, the thickness of the unsaturated zwitterion-based polymer membrane may be 30 to 80 μm; in a specific embodiment of the present invention, the thickness of the unsaturated zwitterion-based polymer membrane is 30 μm, 50 μm or 80 μm.

[0049] The unsaturated zwitterion-based polymer membrane provided by the present invention has high ionic conductivity, a wide electrochemical window, superior thermal stability and excellent interfacial compatibility, and can be used in a wide temperature range. The results of the examples show that the room temperature ionic conductivity of the unsaturated zwitterion-based polymer membrane provided by the present invention is 5.35×10 -5 ~12.8×10 -5 S / cm -1 , the anti-oxidation potential is 4.9~5.0V, and the lithium ion migration number is 0.29~0.53.

[0050] The present invention also provides a method for preparing the unsaturated zwitterion-based polymer membrane described in the above technical solution, comprising the following steps:

[0051] The base film is immersed in a precursor solution for immersion treatment, and the obtained immersed base film is irradiated with light to in situ polymerize the base film to generate an unsaturated zwitterionic polymer to obtain the unsaturated zwitterionic polymer film; the precursor solution includes the raw materials for preparing the unsaturated zwitterionic polymer described in the above technical solution.

[0052] In the present invention, the method for preparing the precursor solution comprises the following steps: first mixing a polymerizable monomer, a crosslinker, an unsaturated zwitterionic compound, a lithium salt, and a plasticizer to obtain a first material; and second mixing an initiator with the first material to obtain the precursor solution. The temperature of the first mixing process can be 25 to 40°C; in specific embodiments of the present invention, the temperature of the first mixing process is 25°C, 26°C, or 30°C. In the present invention, the first mixing process can be performed under stirring conditions, which can be mechanical stirring; the stirring speed can be 300 to 500 rpm, and the stirring time can be 2 to 4 hours. In specific embodiments of the present invention, during the first mixing process, the stirring speed is 300 rpm, 400 rpm, or 500 rpm, and the stirring time is 2 hours, 3 hours, or 4 hours. The temperature of the second mixing process can be 25 to 40°C; in specific embodiments of the present invention, the temperature of the second mixing process is 25°C, 26°C, or 30°C. In the present invention, the second mixing can be performed under stirring conditions, which can be mechanical stirring; the stirring speed can be 300-500 rpm, and the stirring time can be 1-2 hours. In specific embodiments of the present invention, when performing the second mixing, the stirring speed is 300 rpm, 400 rpm, or 500 rpm, and the stirring time is 1 hour, 1.5 hours, or 2 hours. By controlling the stirring speed, temperature, and time, the present invention can achieve more uniform mixing of the components.

[0053] The lithium salt concentration in the precursor solution of the present invention can be 1 to 5 mol / L. In specific embodiments, the lithium salt concentration in the precursor solution is 1 mol / L, 1.5 mol / L, or 3 mol / L. Limiting the lithium salt concentration to this range can increase the lithium salt content in the unsaturated zwitterionic polymer and avoid low ionic conductivity due to insufficient lithium salt.

[0054] After obtaining the precursor solution, the present invention immerses the base film in the precursor solution for an impregnation treatment to obtain an impregnated base film. In the present invention, the impregnation treatment temperature can be 20-35°C, and the duration can be 10-20 minutes. In specific embodiments of the present invention, the impregnation treatment temperature is 20°C, 25°C, 30°C, or 35°C, and the duration is 10 minutes, 15 minutes, or 20 minutes. The present invention uses the impregnation treatment to transfer the raw materials for preparing the unsaturated zwitterionic polymer to the base film.

[0055] After obtaining the impregnated base film, the present invention sandwiches the impregnated base film between two glass plates and irradiates the film with light to in-situ polymerize the unsaturated zwitterionic polymer on the base film. In the present invention, the light source for the light irradiation can be ultraviolet light, the wavelength of the ultraviolet light can be 200 to 380 nm, the light irradiation time can be 10 to 60 minutes, and the light intensity of the light irradiation can be 50 to 200 mW / cm 2 In a specific embodiment of the present invention, the wavelength of the ultraviolet light is 365 nm; the light irradiation time is 10 min, 15 min, 20 min, 30 min or 60 min; the light irradiation intensity is 50 mW / cm 2 , 100mW / cm 2 、150mW / cm 2 or 200mW / cm 2 The present invention limits the light source, wavelength, duration, and intensity of the light irradiation to the aforementioned ranges, which enables the crosslinking reaction to proceed more fully and further improves the electrochemical properties of the resulting product. In the present invention, after the light irradiation is completed, the glass plate is removed to obtain the unsaturated zwitterion-based polymer membrane.

[0056] The present invention also provides the use of the unsaturated zwitterion-based polymer described in the above technical solution, the unsaturated zwitterion-based polymer film described in the above technical solution, or the unsaturated zwitterion-based polymer film obtained by the preparation method described in the above technical solution as a solid electrolyte in a lithium-ion battery.

[0057] The present invention also provides a lithium-ion battery comprising a positive electrode, a negative electrode and a solid electrolyte; the solid electrolyte is the unsaturated zwitterion-based polymer described in the above technical solution, the unsaturated zwitterion-based polymer film described in the above technical solution, or the unsaturated zwitterion-based polymer film obtained by the preparation method described in the above technical solution.

[0058] In the present invention, the solid electrolyte can be interposed between the positive electrode and the negative electrode. In the present invention, the positive electrode can include lithium iron phosphate (LFP) material or a nickel-cobalt-manganese ternary material; the nickel-cobalt-manganese ternary material can be NCM811 or NCM622. In a specific embodiment of the present invention, the positive electrode is lithium iron phosphate. The method for preparing the lithium iron phosphate material can include the following steps: mixing lithium iron phosphate, carbon black, polyvinylidene fluoride, and an organic solvent, stirring to obtain a slurry; coating the slurry on an aluminum material, and drying the resulting material to obtain the lithium iron phosphate material. In the present invention, the mass ratio of lithium iron phosphate, carbon black, and polyvinylidene fluoride can be 80:10:10; the organic solvent can include N-methylpyrrolidone. The stirring can be magnetic stirring, and the stirring time can be 24 hours. The drying temperature can be 120°C and the drying time can be 24 hours. The diameter of the lithium iron phosphate material can be 13 mm. In the present invention, the negative electrode may comprise a metal material, a graphite material, or a silicon-based material; the metal material may be a lithium sheet or a zinc sheet. The graphite material may be graphite or carbon nanotubes; the graphite may be natural graphite or artificial graphite. The silicon-based material may be a single silicon material or a silicon compound material; the silicon compound material may be a silicon-carbon composite material.

[0059] In the present invention, the lithium-ion battery can be a button battery; the button battery can be a 2025-type button battery. The present invention has no particular limitation on the preparation method of the lithium-ion battery, and the technical solution for preparing lithium-ion batteries well known to those skilled in the art can be used.

[0060] In a specific embodiment of the present invention, LFP material is used as the positive electrode, Li sheet is used as the negative electrode, and unsaturated zwitterionic polymer film is used as the solid electrolyte; the solid electrolyte is placed between the positive electrode and the negative electrode to assemble a 2025 type button battery (LFP / / Li battery). The present invention uses the Xinwei battery circulation system to perform charge and discharge cycles on the LFP / / Li battery at different rates at 25°C. The results show that at room temperature, the specific capacity of the LFP / / Li battery is 159mAh / g at a rate of 0.1C; the specific capacity of the LFP / / Li battery is 158mAh / g at a rate of 0.2C; the specific capacity of the LFP / / Li battery is 152mAh / g at a rate of 0.5C; and the specific capacity of the LFP / / Li battery is 14 at a rate of 1C. At a 2C rate, the specific capacity of the LFP / / Li battery was 124 mAh / g. When the rates returned to 1C, 0.5C, and 0.2C, the specific capacity of the LFP / / Li battery could still reach 145 mAh / g, 151 mAh / g, and 154 mAh / g, respectively. At a high rate of 0.5C, the first-cycle discharge capacity of the LFP / / Li battery was 143.77 mAh / g, and after 735 cycles, the capacity retention rate was 91%. This shows that the lithium-ion battery assembled with the unsaturated zwitterionic polymer membrane as the solid electrolyte has excellent rate performance and cycling stability.

[0061] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0062] The methoxy polyethylene glycol acrylate used in the examples has a number average molecular weight of 480 and was purchased from Aladdin Biochemical Technology Co., Ltd.

[0063] The cellulose membrane used in the examples was purchased from Liaoyuan Hongtu Lithium Battery Membrane Technology Co., Ltd.

[0064] Example 1

[0065] 480 mg of methoxy polyethylene glycol acrylate, 2.1 mg of N,N-methylenebisacrylamide, 11.5 mg of 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate, 121.9 mg of 1-allyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 196.5 mg of lithium bis(trifluoromethanesulfonylimide) and 19.7 mg of lithium difluorooxalatoborate were mixed and stirred at 400 rpm for 4 hours at 25° C. to obtain a first material; 4 mg of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide was added to the first material, and the mixture was stirred at 400 rpm for 1 hour at 25° C. to obtain a precursor solution.

[0066] A cellulose membrane with a diameter of 16 mm was immersed in the precursor solution for 10 minutes to obtain an impregnated cellulose membrane; the impregnated cellulose membrane was sandwiched between two glass plates and illuminated at a wavelength of 365 nm and an intensity of 150 mW / cm 2 After irradiation under ultraviolet light for 20 minutes, the glass plate was removed, and the unsaturated zwitterion-based polymer was loaded on the base membrane to obtain an unsaturated zwitterion-based polymer membrane with a thickness of 39 μm.

[0067] Figure 1 The SEM image of the unsaturated zwitterion-based polymer membrane prepared in Example 1 is shown in FIG. Figure 1 It can be seen that the surface of the unsaturated zwitterion-based polymer membrane prepared in Example 1 has obvious texture, indicating that the obtained polymer has a cross-linked network structure; combined with the performance test results, it can be seen that the linear macromolecules can be transformed into a three-dimensional network structure after cross-linking, which can improve the strength, heat resistance and chemical stability of the unsaturated zwitterion-based polymer membrane.

[0068] The conductivity of the unsaturated zwitterion-based polymer membrane obtained in Example 1 was tested under different temperature conditions (30-80° C.). The trend of the conductivity change with temperature is shown in FIG. Figure 2 As shown. Figure 2 It can be seen that the unsaturated zwitterionic polymer membrane prepared in Example 1 has good ionic conductivity at different temperatures, and the ionic conductivity can reach 1.28×10 -4 S cm -1 .

[0069] The electrochemical window of the unsaturated zwitterion-based polymer membrane obtained in Example 1 is as follows: Figure 3 As shown. Figure 3 It can be seen that the anti-oxidation potential of the unsaturated zwitterion-based polymer membrane prepared in Example 1 is 5.0V.

[0070] The thermogravimetric curve of the unsaturated zwitterion-based polymer membrane obtained in Example 1 is as follows: Figure 4 As shown. Figure 4 It can be seen that the unsaturated zwitterion-based polymer membrane begins to decompose at 300°C, which is conducive to the use of the unsaturated zwitterion-based polymer membrane in a wider temperature range.

[0071] The stress-strain curve of the unsaturated zwitterion-based polymer membrane obtained in Example 1 is shown in FIG. Figure 5 As shown. Figure 5 It can be seen that the stress of the unsaturated zwitterion-based polymer membrane is 3.36 MPa and the strain is 9.1%.

[0072] The unsaturated zwitterion-based polymer membrane obtained in Example 1 was used as the electrolyte, and lithium sheets were used as the positive electrode sheet and the negative electrode sheet to assemble a Li / / Li symmetrical battery.

[0073] The It curve of the Li / / Li symmetric battery prepared based on the unsaturated zwitterionic polymer membrane and the impedance results before and after battery polarization are shown in Figure 2. Figure 6 As shown. Figure 6 It can be seen that the lithium ion transference number of the unsaturated zwitterion-based polymer membrane prepared in Example 1 at room temperature is 0.53.

[0074] The voltage variation curve of the Li / / Li symmetric battery prepared based on unsaturated zwitterionic polymer membrane under constant current conditions is shown in the figure. Figure 7 As shown. Figure 7 It can be seen that the unsaturated zwitterion-based polymer membrane can be used at 0.1 mA cm -2 Lithium plating and stripping can be stably carried out under the above conditions for 2000 h, and the overpotential is reduced from the initial 39 mV to 13 mV, which confirms that the unsaturated zwitterionic polymer membrane prepared in Example 1 has good interfacial compatibility.

[0075] Example 2

[0076] A mixture of 80% lithium iron phosphate (LFP), 10% carbon black, and 10% polyvinylidene fluoride (PVDF, as a binder) containing the positive electrode active material (mass fraction) was added to N-methylpyrrolidone and magnetically stirred for 24 hours to form a viscous slurry. The slurry was then coated on aluminum foil and placed in a vacuum drying oven for 24 hours at 120°C. After drying, the temperature was adjusted to room temperature and the resulting material was cut into circular electrodes with a diameter of 13 mm to obtain the positive electrode. An unsaturated zwitterionic polymer membrane (as a solid electrolyte) was assembled with the positive electrode and the negative electrode (lithium) to form a 2025-type button cell (LFP / unsaturated zwitterionic polymer membrane / Li battery, referred to as LFP / / Li battery).

[0077] At 25°C, the LFP / / Li battery was tested for charge and discharge cycles at different rates using the Xinwei battery cycling system. The results are as follows: Figure 8 As shown. Figure 8 It can be seen that at room temperature, the specific capacity of the LFP / / Li battery is 159mAh / g at a rate of 0.1C; the specific capacity of the LFP / / Li battery is 158mAh / g at a rate of 0.2C; the specific capacity of the LFP / / Li battery is 152mAh / g at a rate of 0.5C; the specific capacity of the LFP / / Li battery is 143mAh / g at a rate of 1C; the specific capacity of the LFP / / Li battery is 124mAh / g at a rate of 2C; when returning to the rates of 1C, 0.5C, and 0.2C respectively, the specific capacity of the LFP / / Li battery can still reach 145mAh / g, 151mAh / g, and 154mAh / g respectively. It can be seen that the obtained button battery has excellent rate performance.

[0078] The LFP / unsaturated zwitterionic polymer membrane / Li battery assembled in Example 2 had a first-cycle discharge capacity of 143.77 mAh / g at a high rate of 0.5 C, and a capacity retention rate of 91% after 735 cycles.

[0079] Example 3

[0080] 480 mg of methoxy polyethylene glycol acrylate, 2.1 mg of N,N-methylenebisacrylamide, 11.5 mg of 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate, 81.3 mg of 1-allyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 186.2 mg of lithium bis(trifluoromethanesulfonylimide) and 18.6 mg of lithium difluorooxalatoborate were mixed and stirred at 400 rpm for 4 hours at 25° C. to obtain a first material; 4 mg of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide was added to the first material, and the mixture was stirred at 400 rpm for 1 hour at 25° C. to obtain a precursor solution.

[0081] A cellulose membrane with a diameter of 16 mm was immersed in the precursor solution for 10 minutes to obtain an impregnated cellulose membrane; the impregnated cellulose membrane was sandwiched between two glass plates and illuminated at a wavelength of 365 nm and an intensity of 150 mW / cm 2 After irradiation under ultraviolet light for 20 minutes, the glass plate was removed, and the unsaturated zwitterion-based polymer was loaded on the base membrane to obtain an unsaturated zwitterion-based polymer membrane with a thickness of 41 μm.

[0082] The conductivity, lithium ion transference number and antioxidant potential of the unsaturated zwitterion-based polymer membrane prepared in Example 3 were tested according to the conditions of Example 1. The results showed that the room temperature ionic conductivity of the unsaturated zwitterion-based polymer membrane prepared in Example 3 was 6.55×10 -5 S cm -1, the lithium ion transference number at room temperature is 0.49, and the anti-oxidation potential is 4.9V.

[0083] Example 4

[0084] 480 mg of methoxy polyethylene glycol acrylate, 2.1 mg of N,N-methylenebisacrylamide, 11.5 mg of 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate, 162.5 mg of 1-allyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 206.8 mg of lithium bis(trifluoromethanesulfonylimide) and 20.68 mg of lithium difluorooxalatoborate were mixed and stirred at 400 rpm for 4 hours at 25° C. to obtain a first material; 4 mg of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide was added to the first material, and the mixture was stirred at 400 rpm for 1 hour at 25° C. to obtain a precursor solution.

[0085] A cellulose membrane with a diameter of 16 mm was immersed in the precursor solution for 10 minutes to obtain an impregnated cellulose membrane; the impregnated cellulose membrane was sandwiched between two glass plates and illuminated at a wavelength of 365 nm and an intensity of 150 mW / cm 2 After irradiation under ultraviolet light for 20 minutes, the glass plate was removed, and the unsaturated zwitterion-based polymer was loaded on the base membrane to obtain an unsaturated zwitterion-based polymer membrane with a thickness of 40 μm.

[0086] The conductivity, lithium ion transference number and antioxidant potential of the unsaturated zwitterion-based polymer membrane prepared in Example 4 were tested according to the conditions of Example 1. The results showed that the room temperature ionic conductivity of the unsaturated zwitterion-based polymer membrane prepared in Example 4 was 5.35×10 -5 S cm -1 , the lithium ion migration number at room temperature is 0.29, and the anti-oxidation potential is 4.95V.

[0087] Comparative Example 1

[0088] 480 mg of methoxy polyethylene glycol acrylate, 2.1 mg of N,N-methylenebisacrylamide, 11.5 mg of 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate, 165.6 mg of lithium bistrifluoromethylsulfonyl imide and 16.56 mg of lithium difluorooxalatoborate were mixed, and the mixture was stirred at 400 rpm for 4 hours at 25° C. to obtain a first material; 4 mg of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide was added to the first material, and the mixture was stirred at 400 rpm for 1 hour at 25° C. to obtain a precursor solution.

[0089] A cellulose membrane with a diameter of 16 mm was immersed in the precursor solution for 10 minutes to obtain an impregnated cellulose membrane; the impregnated cellulose membrane was sandwiched between two glass plates and illuminated at a wavelength of 365 nm and an intensity of 150 mW / cm 2 The film was irradiated under ultraviolet light for 20 min, and the glass plate was removed after irradiation to obtain a polymer film with a thickness of 40 μm.

[0090] The conductivity and lithium ion transference number of the polymer film prepared in Comparative Example 1 were tested according to the conditions of Example 1. The results showed that the room temperature ionic conductivity of the polymer film prepared in Comparative Example 1 was 3.15×10 -5 S cm -1 The lithium ion transfer number at room temperature is 0.38, the conductivity is low, the interface impedance is large, and the charge and discharge capacity of the button battery at room temperature is low, only about 30mAh / g. This is due to the low ion conductivity, which leads to the Li + The transmission between the positive and negative electrodes becomes difficult; the large interface impedance will cause the power attenuation of the button battery, thereby reducing the available capacity of the button battery; in addition, the uncontrollable dendrite growth will cause a large volume expansion and low reversibility, and the local ion depletion to form a space charge layer (SCL) will also accelerate the growth of Li dendrites.

[0091] Comparative Example 2

[0092] 480 mg of methoxy polyethylene glycol acrylate, 2.1 mg of N,N-methylenebisacrylamide, 121.9 mg of 1-allyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide, 161.5 mg of lithium bis(trifluoromethanesulfonyl)imide and 16.15 mg of lithium difluorooxalatoborate were mixed, and the mixture was stirred at 400 rpm for 4 hours at 25° C. to obtain a first material; 4 mg of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide was added to the first material, and the mixture was stirred at 400 rpm for 1 hour at 25° C. to obtain a precursor solution.

[0093] A cellulose membrane with a diameter of 16 mm was immersed in the precursor solution for 10 minutes to obtain an impregnated cellulose membrane; the impregnated cellulose membrane was sandwiched between two glass plates and illuminated at a wavelength of 365 nm and an intensity of 150 mW / cm 2 The film was irradiated under ultraviolet light for 20 min, and the glass plate was removed to obtain a polymer film with a thickness of 50 μm.

[0094] The conductivity and lithium ion transference number of the polymer membrane prepared in Comparative Example 2 were tested according to the conditions of Example 1. The results showed that the room temperature ionic conductivity of the polymer membrane prepared in Comparative Example 2 was 8.63×10 -5 S cm -1The lithium ion transference number at room temperature is 0.33. This is because the lack of zwitterions allows both anions and lithium ions in the button cell to move freely, which in turn leads to a decrease in the lithium ion transference number. Furthermore, the addition of plasticizers promotes the movement of polymer chains and the dissociation of lithium salts, thereby improving ionic conductivity.

[0095] In summary, the unsaturated zwitterion-based polymer membrane provided by the present invention has high room-temperature ionic conductivity, a wide electrochemical window and excellent thermal stability. The lithium iron phosphate battery assembled using the unsaturated zwitterion-based polymer membrane as a solid electrolyte has excellent rate performance and cycle performance.

[0096] Although the above embodiment provides a detailed description of the present invention, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the scope of protection of the present invention.

Claims

1. An unsaturated zwitterionic polymer, characterized in that Calculated by mass, it includes the following preparation raw materials: 40-70 parts of polymerizable monomers, 0.1-1 parts of cross-linking agents, 1-10 parts of unsaturated zwitterionic compounds, 20-30 parts of lithium salts, 5-20 parts of plasticizers, and 0.1-1 parts of initiators; the cross-linking agent contains imino groups and unsaturated groups; the polymerizable monomers and the unsaturated zwitterionic compounds respectively contain ether bond groups capable of forming hydrogen bonds with the imino groups in the cross-linking agent in their structures; and the plasticizer is an ionic liquid.

2. The unsaturated zwitterionic polymer according to claim 1, characterized in that The cross-linking agent includes N,N-methylenebisacrylamide; and the polymerizable monomer is a polyethylene glycol acrylate monomer.

3. The unsaturated zwitterionic polymer according to claim 2, characterized in that The polyethylene glycol acrylate monomer includes at least one of methoxy polyethylene glycol acrylate, ethylene glycol monomethyl ether acrylate and polyethylene glycol methyl ether methacrylate; The number average molecular weight of the methoxy polyethylene glycol acrylate is 480 to 10,000; the number average molecular weight of the polyethylene glycol methyl ether methacrylate is 300 to 4,000.

4. The unsaturated zwitterionic polymer according to claim 1, characterized in that The unsaturated zwitterionic compound includes at least one of [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfonic acid propyl)ammonium hydroxide, 2-methacryloyloxyethyl phosphorylcholine, and 3-[[2-(methacryloyloxy)ethyl]dimethylammonium]propionate; The lithium salt includes at least one of lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethylsulfonyl)imide, lithium nitrate, lithium difluorophosphate and lithium difluorooxalatoborate; The plasticizer includes at least one of 1-n-butyl-3-methylimidazolium hexafluorophosphate and 1-allyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide; The initiator includes at least one of phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide, 2-hydroxy-2-methyl-1-phenylpropanone and 1-hydroxycyclohexylphenylketone.

5. An unsaturated zwitterion-based polymer membrane, characterized in that The invention comprises a base film and a polymer loaded on the base film; the polymer is the unsaturated zwitterion-based polymer according to any one of claims 1 to 4.

6. The unsaturated zwitterion-based polymer membrane according to claim 5, characterized in that The base membrane is a polyethylene membrane, a polypropylene membrane, a cellulose membrane, a glass fiber membrane, a polyvinylidene fluoride membrane or a polyacrylonitrile membrane; and the loading amount of the polymer on the unsaturated zwitterionic polymer membrane is 85% to 95%.

7. The method for preparing the unsaturated zwitterion-based polymer membrane according to any one of claims 5 to 6, comprising the following steps: The base film is immersed in a precursor solution for immersion treatment, and the obtained immersed base film is irradiated with light to in situ polymerize the base film to generate an unsaturated zwitterionic polymer to obtain the unsaturated zwitterionic polymer film; the precursor solution includes the raw materials for preparing the unsaturated zwitterionic polymer according to any one of claims 1 to 4.

8. The preparation method according to claim 7, characterized in that The immersion treatment time is 10 to 20 minutes; the light source of the light irradiation is ultraviolet light, the wavelength of the ultraviolet light is 200 to 380 nm; the light irradiation time is 10 to 60 minutes, and the light intensity of the light irradiation is 50 to 200 mW / cm 2 .

9. Use of the unsaturated zwitterion-based polymer according to any one of claims 1 to 4, the unsaturated zwitterion-based polymer film according to any one of claims 5 to 6, or the unsaturated zwitterion-based polymer film prepared by the method according to any one of claims 7 to 8 as a solid electrolyte in a lithium-ion battery.

10. A lithium-ion battery comprising a positive electrode, a negative electrode and a solid electrolyte; the solid electrolyte is the unsaturated zwitterion-based polymer membrane according to any one of claims 5 to 6 or the unsaturated zwitterion-based polymer membrane prepared by the method according to any one of claims 7 to 8.

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