CN118185277A - Film material, film, lithium ion battery and preparation method of lithium ion battery - Google Patents

Abstract

Film material, film, lithium ion battery and preparation method of lithium ion battery. The film layer material comprises: polyethylene glycol dimethacrylate, sulfonamide compound and lithium salt. The sulfonamide compound can be used as a dispersing agent, so that the sulfonamide compound, polyethylene glycol dimethacrylate and lithium salt can be a uniform system. The sulfonamide compound can also be used as a plasticizer, intermolecular acting force exists between the sulfonamide compound and ether bond in polyethylene glycol dimethacrylate, and the intermolecular acting force can be used for the glass transition temperature of the polyethylene glycol dimethacrylate, so that the chain segment movement of the polyethylene glycol dimethacrylate is effectively promoted, and the film material has better Li+ conductivity. The film material has larger Li+ conductivity, and when the film material is applied to a lithium ion battery, a stable interface can be formed between the film formed by the film material and the anode/cathode, and the interface cannot be degraded along with deposition/stripping of lithium in the battery cycle process.

Description

Membrane material, membrane, lithium ion battery and method for preparing lithium ion battery

Technical Field

The present application relates to the field of lithium-ion batteries, and in particular to membrane materials, membrane layers, lithium-ion batteries, and methods for preparing lithium-ion batteries.

Background technique

Lithium ion cells and batteries include: positive electrode, negative electrode and electrolyte. Lithium ion batteries rely on the reciprocating stripping or deposition of lithium ions (Li+) between the positive electrode and the negative electrode to achieve battery charging or discharging.

Usually, the positive electrode and the negative electrode are connected by an electrolyte. As an important component of lithium-ion batteries, the electrolyte plays the role of conducting Li+ and current between the positive electrode and the negative electrode.

Existing electrolytes mostly use high molecular weight polymers, which have poor dispersion properties and require the addition of small molecule solvents to disperse them. The presence of small molecule solvents will have an adverse effect on the cycle performance of lithium-ion batteries. High molecular weight polymers have low Li+ conductivity.

Summary of the invention

The embodiments of the present application provide a membrane material, a membrane, a lithium ion battery and a method for preparing a lithium ion battery. The membrane material includes polyethylene glycol dimethacrylate, a sulfonamide compound and a lithium salt, so that the membrane material has a high Li+ conductivity.

A first aspect of an embodiment of the present application provides a membrane material, including: polyethylene glycol dimethacrylate, a sulfonamide compound and a lithium salt.

In this implementation, the sulfonamide compound can be used as a polyethylene glycol dimethacrylate dispersant, so that the sulfonamide compound, polyethylene glycol dimethacrylate and lithium salt can form a uniform system. The membrane material provided by this implementation does not need to use a small molecule solvent, so there will be no problems caused by the residual small molecule solvent.

Sulfonamide compounds can also be used as plasticizers for polyethylene glycol dimethacrylate. There is an intermolecular force between the sulfonamide compounds and the ether bonds in polyethylene glycol dimethacrylate. This intermolecular force can increase the glass transition temperature of polyethylene glycol dimethacrylate, thereby effectively promoting the segment movement of polyethylene glycol dimethacrylate, so that the film material has better Li+ conductivity. Since the glass transition temperature of polyethylene glycol dimethacrylate is reduced, the film material provided by the present implementation can show a large Li+ conductivity at room temperature, low temperature and high temperature.

The film material has a large Li+ conductivity. When it is applied to a lithium-ion battery, a serious charge layer will not be formed between the film formed by the film material and the positive/negative electrode of lithium ions. The film formed by the film material can form a stable interface with the positive/negative electrode, and the interface will not deteriorate with the deposition/stripping of lithium during the battery cycle. The thin film material provided in the embodiment of the present application has the effect of stabilizing lithium deposition/stripping.

The polyethylene glycol dimethacrylate in the film material can undergo a cross-linking reaction, so that the film material is converted into a film/cross-linking system with a certain toughness. The film/cross-linking system can be applied to lithium-ion batteries to inhibit the growth of lithium dendrites.

In combination with the first implementation manner of the first aspect, the film layer material may further include: ethylene glycol monomethyl ether methacrylate.

In this implementation, ethylene glycol monomethyl ether methacrylate can serve as an end group for polyethylene glycol dimethacrylate to undergo a cross-linking reaction, thereby terminating the cross-linking reaction of polyethylene glycol dimethacrylate. The relative molecular weight of the cross-linking system formed after the cross-linking of the film material can be controlled by controlling the content of polyethylene glycol dimethacrylate and polyethylene glycol monomethyl ether methacrylate.

In combination with the second implementation of the first aspect, the molar ratio of polyethylene glycol dimethacrylate (PEGDMA) to polyethylene glycol monomethyl ether methacrylate (PEGMA) is 1:10 to 10:1.

In this implementation, the molar ratio of PEGDMA to PEGMA can be greater than or equal to 1:10. Compared with the implementation in which the molar ratio of PEGDMA to PEGMA is less than 1:10, the membrane material provided by this implementation contains more PEGDMA, and more PEGDMA can be cross-linked to obtain a cross-linked system with a loose structure. Therefore, the membrane material provided by this implementation has a loose cross-linked system after cross-linking, and the cross-linked membrane material has a larger Li ⁺ conductivity.

The molar ratio of PEGDMA to PEGMA can be less than or equal to 10:1. Compared with the implementation method in which the molar ratio of PEGDMA to PEGMA is greater than 10:1, the membrane material provided by this implementation method contains more PEGMA, and PEGMA can be used as an end group during the cross-linking reaction of the membrane material to terminate the cross-linking reaction. This implementation method can reduce the problem of local crystallization caused by the formation of a cross-linking system with a large degree of cross-linking during the cross-linking process.

The molar ratio of PEGDMA to PEGMA can be between 1:10 and 10:1, taking into account both the larger Li ⁺ conductivity of the membrane material and the reduction of the local crystallization problem of the membrane material after cross-linking.

In combination with the third implementation of the first aspect, the molecular structure of the sulfonamide compound is an asymmetric structure.

In this implementation, the molecular structure of the sulfonamide compound is an asymmetric structure. Sulfonamide compounds with an asymmetric molecular structure are not easy to be closely stacked between molecules, and the sulfonamide compounds have greater plasticizing properties.

In combination with the fourth implementation of the first aspect, the substituent of the sulfonamide compound includes: any one of a methyl group, an ethyl group or an ether group.

In this implementation, the substituent of the sulfonamide compound includes any one of methyl, ethyl or ether groups. The sulfonamide compound containing methyl, ethyl or ether group substituents is not easy to crystallize, thereby ensuring that the sulfonamide compound has a greater plasticizing property.

In combination with the fifth implementation of the first aspect, the lithium salt includes: lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethyl)sulfonyl imide.

In this implementation, the lithium salt includes: lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethyl)sulfonyl imide. Both lithium bis(fluorosulfonyl)imide and lithium bis(trifluoromethyl)sulfonyl imide have fluoride ions ( ^{F- )} , which can react with lithium metal in the negative electrode during the charge and discharge process to form a SEI containing lithium fluoride on the surface of the negative electrode. The SEI containing lithium fluoride can achieve uniform deposition of Li ⁺ in the negative electrode, or uniform stripping of Li in the negative electrode.

Lithium bis(fluorosulfonyl)imide has a large solubility in polyethylene oxide polymers, thereby ensuring that there are more lithium ions in the membrane material. The polyethylene oxide polymers include polyethylene glycol dimethacrylate, or polyethylene glycol dimethacrylate and ethylene glycol monomethyl ether methacrylate.

In combination with the sixth implementation of the first aspect, the mass ratio of lithium bis(fluorosulfonyl)imide (LiFSI) to lithium bis(trifluoromethyl)sulfonyl imide (LiTFSI) is in the range of 1:2 to 2:1.

In this implementation, the mass ratio of LiTFSI to LiFSI can be less than or equal to 2: 1. Compared with the implementation in which the mass ratio of LiTFSI to LiFSI is greater than 2: 1, the membrane material provided by this implementation contains more LiFSI, that is, more Li ⁺ is dissolved in the polyethylene oxide polymer, and the membrane material has a larger Li ⁺ conductivity.

The mass ratio of LiTFSI to LiFSI can be greater than or equal to 1:2. Compared with the implementation method in which the mass ratio of LiTFSI to LiFSI is less than 12, the membrane material provided by this implementation method contains more LiTFSI. That is, more ^F- is dissolved in the polyethylene oxide polymer. When the membrane material is applied to a lithium-ion battery, more SEI containing LiF can be formed. Polyethylene oxide polymers include: polyethylene glycol dimethacrylate, or polyethylene glycol dimethacrylate and ethylene glycol monomethyl ether methacrylate. The mass ratio of LiTFSI to LiFSI can be 1:2 to 2:1, which can improve the Li ⁺ conductivity of the membrane material and the ^F- content in the membrane material.

In combination with the seventh implementation of the first aspect, the mass fraction of the sulfonamide compound is between 40% and 60%. In this implementation, the mass fraction of the sulfonamide compound in the film material can be greater than or equal to 40%. Compared with the film material with a mass fraction of the sulfonamide compound less than 40%, the film material provided by this implementation contains more sulfonamide compounds, and the plasticizing properties of more sulfonamide compounds on the polyethylene oxide polymer are more significant, thereby making the polyethylene oxide polymer have a larger chain segment movement, and accordingly, the film material has a larger Li+ conductivity. The polyethylene oxide polymer includes: polyethylene glycol dimethacrylate, or includes polyethylene glycol dimethacrylate and ethylene glycol monomethyl ether methacrylate.

The mass fraction of the sulfonamide compound in the film material can be less than or equal to 60%. Compared with the film material with a mass fraction of the sulfonamide compound greater than 60%, the film material provided by the present implementation contains less sulfonamide compounds. Fewer sulfonamide compounds can make the film material have greater viscosity, and in the formation process of the lithium-ion battery, the film material provided by the present implementation is less difficult to coat on the surface of the solid electrolyte.

The mass fraction of the sulfonamide compound can be 40% to 60%, which can take into account both the viscosity of the membrane material and the Li+ conductivity of the membrane material.

In combination with the eighth implementation of the first aspect, the relative molecular mass of polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate is between 300 and 600.

In this implementation, the relative molecular mass of polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate can be greater than or equal to 300. Compared with the implementation using polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate with a relative molecular mass less than 300, the membrane material in this implementation uses polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate with a larger relative molecular mass. The cross-linking system formed after cross-linking of the membrane material provided by this implementation has greater toughness, and when applied to lithium-ion batteries, the cross-linking system can have a strong inhibitory effect on lithium dendrites.

The relative molecular mass of polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate is less than or equal to 600. Compared with the implementation method using polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate with a relative molecular mass greater than 600, the membrane material in this implementation method uses polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate with a smaller relative molecular mass. The membrane material provided by this implementation method has greater fluidity, and the technical difficulty of combining the membrane material with the lithium-ion battery injection process is relatively low.

The relative molecular weight of polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate can be 300-600, which can take into account the fluidity of the film material and the toughness of the cross-linked system formed after cross-linking.

In combination with the ninth implementation of the first aspect, the degree of polymerization of polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate is 4-12.

In this implementation, the degree of polymerization of polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate may be greater than or equal to 4. Compared with the implementation using polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate having a degree of polymerization less than 4, the membrane material in this implementation uses polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate with a larger degree of polymerization, and the cross-linking system structure formed after cross-linking of polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate with a larger degree of polymerization is loose, the chain segment movement of the cross-linking system is more significant, and the Li+ conductivity of the cross-linking system is larger.

The degree of polymerization of polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate may be less than or equal to 12. Compared with the implementation method using polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate having a degree of polymerization greater than 12, the membrane material in this implementation method uses polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate having a smaller degree of polymerization, and the membrane material provided by this implementation method has greater fluidity, and the technical difficulty of combining the membrane material with the lithium-ion battery injection process is relatively small.

The degree of polymerization of polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate can be 4 to 12, which can take into account both the fluidity of the membrane material and the Li+ conductivity of the cross-linked membrane material.

In combination with the tenth implementation manner of the first aspect, the molar ratio of the ether bonds contained in polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate to the lithium ions contained in the lithium salt is 10-30.

In this implementation, the molar ratio of ether bonds to Li+ in the membrane material can be greater than or equal to 10. Compared with the implementation in which the molar ratio of ether bonds to Li+ in the membrane material is less than 10, the membrane material provided by this implementation contains more ether bonds, and more ether bonds can make the membrane material have a greater Li+ conductivity.

The molar ratio of ether bonds to Li+ in the membrane material can be less than or equal to 30. Compared with the implementation method in which the molar ratio of ether bonds to Li+ in the membrane material is greater than 30, the membrane material provided by this implementation method contains fewer ether bonds, that is, the relative molecular mass of polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate in the membrane material is smaller, or the degree of polymerization of polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate is smaller. Accordingly, the viscosity of the membrane material provided by this implementation method is lower, and the technical difficulty of combining the membrane material with the lithium-ion battery injection process is lower.

As a feasible implementation method, the molar ratio of ether bonds to Li+ in the membrane material can be 10 to 30, which can take into account both the viscosity of the membrane material and the Li+ conductivity of the membrane material.

In combination with the eleventh implementation manner of the first aspect, the concentration of the lithium salt is less than or equal to 25%.

In this implementation, the sulfonamide compound has a plasticizing effect on polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate, thereby effectively promoting the segment movement of polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate, thereby improving the migration performance of Li+ in polyethylene glycol dimethacrylate/ethylene glycol monomethyl ether methacrylate. Therefore, the mass fraction of lithium salt used in the membrane material provided in the embodiment of the present application can be less than or equal to 25%, and the membrane material can also have a large Li+ conductivity.

In combination with the twelfth implementation manner of the first aspect, the membrane layer material has fluidity.

In this implementation, the membrane material has fluidity, so that the membrane material can be used in conjunction with the lithium-ion battery injection process.

In combination with the thirteenth implementation manner of the first aspect, the membrane layer material also includes: a diaphragm material.

In this implementation, the membrane material also includes a diaphragm material, and the diaphragm material has the function of allowing Li+ to pass through and isolating e-. Therefore, the membrane material also has the function of allowing Li+ to pass through and isolating e-.

A second aspect of an embodiment of the present application provides a film layer, which adopts the film layer material provided by the first aspect.

Among them, the effect that can be brought about by any implementation method of the second aspect can refer to the effect brought about by any possible implementation method of the above-mentioned first aspect.

In combination with the first implementation manner of the second aspect, the membrane layer has self-supporting properties.

In this implementation, the film layer has self-supporting properties. When the film layer is applied between the positive electrode and the negative electrode of the lithium-ion battery, the conduction problem between the positive electrode and the negative electrode of the lithium-ion battery caused by wrinkles in the film layer can be reduced.

A third aspect of an embodiment of the present application provides a lithium-ion battery, including: a positive electrode, a negative electrode, and a composite solid electrolyte, wherein the composite solid electrolyte is arranged between the positive electrode and the negative electrode, and the composite solid electrolyte adopts the membrane material provided in the thirteenth implementation method of the first aspect.

In the present implementation, the composite solid electrolyte uses a membrane material including polyethylene glycol dimethacrylate, a sulfonamide compound, a lithium salt and a diaphragm material.

The composite solid electrolyte uses membrane materials, wherein the membrane materials include: diaphragm materials. The diaphragm materials have the function of allowing lithium ions to pass through and blocking electrons. Therefore, the composite solid electrolyte also has the function of allowing lithium ions to pass through and blocking electrons.

Sulfonamide compounds can be used as polyethylene glycol dimethacrylate dispersants, so that sulfonamide compounds, lithium salts, and membrane materials can form a uniform system. The membrane material provided by this implementation does not need to use small molecule solvents, so there will be no problems caused by residual small molecule solvents.

Sulfonamide compounds can also be used as plasticizers for polyethylene glycol dimethacrylate. There is an intermolecular force between the sulfonamide compounds and the ether bonds in polyethylene glycol dimethacrylate. This intermolecular force can increase the glass transition temperature of polyethylene glycol dimethacrylate, thereby effectively promoting the chain segment movement of polyethylene glycol dimethacrylate, so that the composite solid electrolyte has better Li+ conductivity.

Composite solid electrolytes have a large Li+ conductivity. When used in lithium-ion batteries, no serious charge layer will be formed between the composite solid electrolyte and the positive/negative electrode. Composite solid electrolytes can form a stable interface with the positive/negative electrode, which will not deteriorate with the deposition/stripping of lithium during the battery cycle, so that lithium-ion batteries have stable cycle performance.

The composite solid electrolyte has a certain toughness and can inhibit the growth of lithium dendrites on the negative electrode surface. Therefore, the lithium-ion battery provided by this implementation can use a lithium metal negative electrode with a higher specific capacity, thereby ensuring that the lithium-ion battery has a higher energy density.

The negative electrode is in contact with the composite solid electrolyte. The composite solid electrolyte does not contain metals such as lanthanum and zirconium. Even if the negative electrode of the lithium-ion battery uses lithium metal, the composite solid electrolyte and lithium metal have fewer side reactions. The composite solid electrolyte and the lithium metal negative electrode can still have a relatively stable interface after multiple charge and discharge cycles, and the lithium-ion battery can still have a small interface impedance after multiple charge and discharge cycles.

The fourth aspect of the embodiment of the present application provides a lithium-ion battery comprising: a positive electrode, a negative electrode, a solid electrolyte and at least one protective layer. The solid electrolyte is arranged between the positive electrode and the negative electrode; the protective layer is arranged between the solid electrolyte and the positive electrode, and/or between the solid electrolyte and the negative electrode, and the protective layer adopts the film material provided in the first aspect.

In the present implementation, the protective layer adopts a film material including polyethylene glycol dimethacrylate, a sulfonamide compound and a lithium salt.

Sulfonamide compounds can be used as polyethylene glycol dimethacrylate dispersants, so that sulfonamide compounds and lithium salts can form a uniform system. The membrane material provided by this implementation does not need to use small molecule solvents, so there will be no problems caused by residual small molecule solvents.

Sulfonamide compounds can also be used as plasticizers for polyethylene glycol dimethacrylate. There is an intermolecular force between the sulfonamide compounds and the ether bonds in polyethylene glycol dimethacrylate. This intermolecular force can increase the glass transition temperature of polyethylene glycol dimethacrylate, thereby effectively promoting the chain segment movement of polyethylene glycol dimethacrylate, so that the protective layer has better Li+ conductivity.

The protective layer has a large Li+ conductivity. When it is used in lithium-ion batteries, no serious charge layer will be formed between the protective layer and the positive/negative electrode. The protective layer and the positive/negative electrode can form a stable interface, which will not deteriorate with the deposition/stripping of lithium during the battery cycle, so that the lithium-ion battery has stable cycle performance.

The protective layer has a certain toughness to inhibit the growth of lithium dendrites. Therefore, the protective layer can protect the solid electrolyte. The lithium-ion battery provided by this implementation can use a lithium metal negative electrode with a higher specific capacity, thereby ensuring that the lithium-ion battery has a higher energy density.

The protective layer does not contain metals such as lanthanum and zirconium. Even if the negative electrode of the lithium-ion battery uses lithium metal, the protective layer and the lithium metal have less side reactions. The protective layer and the lithium metal negative electrode can still have a relatively stable interface after multiple charge and discharge cycles, and the lithium-ion battery can still have a small interface impedance after multiple charge and discharge cycles.

A fifth aspect of an embodiment of the present application provides a method for preparing a lithium-ion battery, comprising: adding an initiator to the film material provided in the first aspect to obtain a polymer precursor; using a positive electrode, a negative electrode and a polymer precursor to form a lithium-ion battery; the lithium-ion battery comprises: a positive electrode, a negative electrode, and a composite solid electrolyte arranged between the positive electrode and the negative electrode, and the composite solid electrolyte is formed by the film material.

In combination with the first implementation method of the fifth aspect, the steps of forming a lithium-ion battery using a positive electrode, a negative electrode and a polymer precursor include: treating the polymer precursor so that the polymer precursor forms a composite solid electrolyte; assembling the positive electrode, the negative electrode and the composite solid electrolyte to obtain a lithium-ion battery.

In combination with the second implementation method of the fifth aspect, the steps of forming a lithium-ion battery using a positive electrode, a negative electrode and a polymer precursor include: assembling the positive electrode, the negative electrode and the polymer precursor; and processing the polymer precursor so that the polymer precursor forms a composite solid electrolyte.

Among them, the effect that can be brought about by any implementation method of the fifth aspect can refer to the effect brought about by any possible implementation method of the first aspect mentioned above.

A sixth aspect of an embodiment of the present application provides a method for preparing a lithium-ion battery, comprising: adding an initiator to the film material provided in the thirteenth implementation method of the first aspect to obtain a polymer precursor; using a positive electrode, a negative electrode, a solid electrolyte and a polymer precursor to form a lithium-ion battery, the lithium-ion battery comprising: a positive electrode, a negative electrode, a solid electrolyte and at least one protective layer, the solid electrolyte is arranged between the positive electrode and the negative electrode, at least one protective layer is formed by the film material, and the protective layer is arranged between the solid electrolyte and the positive electrode, and/or, between the solid electrolyte and the negative electrode.

In combination with the first implementation method of the sixth aspect, the steps of forming a lithium-ion battery using a positive electrode, a negative electrode and a solid electrolyte coated with a polymer precursor on the surface include: coating a polymer precursor on the surface of the solid electrolyte; treating the polymer precursor so that the polymer precursor forms a protective layer; assembling the positive electrode, the negative electrode and the solid electrolyte with a protective layer on the surface to obtain a lithium-ion battery.

In combination with the second implementation method of the sixth aspect, the steps of forming a lithium-ion battery using a positive electrode, a negative electrode, a solid electrolyte and a polymer precursor include: assembling the positive electrode, the negative electrode, the solid electrolyte and the polymer precursor; processing the polymer precursor so that the polymer precursor forms a protective layer.

Among them, the effect that can be brought about by any implementation method of the sixth aspect can refer to the effect brought about by any possible implementation method of the above-mentioned first aspect.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of a lithium-ion battery;

FIG2 is a graph showing the gram capacity of negative electrode materials for lithium-ion batteries and the theoretical volume energy density that can be achieved;

FIG3 is a diagram showing the experimental results of the prior art 1;

FIG4 is a diagram showing the experimental results of the second prior art;

FIG5 is a diagram showing the experimental results of the prior art three;

FIG6 is a diagram showing the experimental results of the prior art four;

FIG7 is a schematic diagram of a film material provided in an embodiment of the present application;

FIG8A is the structural formula of PEGMA;

FIG8B is the structural formula of PEGDMA;

FIG9 is a cross-linking system formed by PEGDMA and PEGMA provided in an embodiment of the present application;

FIG10 is a structural formula of a sulfonamide compound provided in an embodiment of the present application;

FIG11 is a schematic diagram of a lithium-ion battery;

FIG12 is a graph showing the cycling performance test results of the first lithium ion battery and the second lithium ion battery;

FIG13 is a graph showing the cycle performance test results of a third lithium-ion battery;

FIG14 is an ionic conductivity-temperature curve of a fourth lithium ion battery;

FIG15 is a schematic diagram of a protective layer provided in an embodiment of the present application;

FIG16 is a schematic diagram of a protective layer/composite solid electrolyte provided in an embodiment of the present application;

FIG17 is a schematic diagram of a composite solid electrolyte provided in an embodiment of the present application;

FIG18 is a schematic diagram of a lithium-ion battery provided in an embodiment of the present application;

FIG19 is a diagram showing the impedance test results of Li|LLZO|Li and Li|PE|LLZO|PE|Li;

FIG20 is a graph showing the test results of Li|LLZO|Li cycle performance;

FIG21 is a graph showing the test results of Li|PE|LLZO|PE|Li cycle performance;

FIG22 is a schematic diagram of a lithium-ion battery provided in an embodiment of the present application;

FIG23 is a graph showing the test results of Li|composite PE|Li cycle performance;

FIG24 is a graph showing the test results of Li|composite PE|Li cycle performance;

FIG25 is a flow chart of a method for preparing an ion battery provided in an embodiment of the present application;

FIG26 is a process flow chart of the preparation method provided in FIG25 ;

FIG27 is a preparation process of sulfonamide compounds provided in an embodiment of the present application;

FIG28 is a cross-sectional view of a lithium-ion battery provided in an embodiment of the present application;

FIG29 is a cross-sectional view of a battery cell provided in an embodiment of the present application;

FIG30 is a flow chart of a method for preparing an ion battery provided in an embodiment of the present application;

FIG31 is a process flow chart of the preparation method provided in FIG30 ;

FIG32 is a cross-sectional view of a lithium-ion battery provided in an embodiment of the present application;

FIG33 is a cross-sectional view of a battery cell provided in an embodiment of the present application.

Detailed ways

The technical solutions in the embodiments of the present application will be described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all of the embodiments.

In the following, the terms "first", "second", etc. are used only for descriptive purposes to distinguish between identical or similar items with substantially identical functions and effects, and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", etc. may explicitly or implicitly include one or more of the features.

Also, in the description of the present application, unless otherwise specified, “plurality” means two or more than two.

In addition, in this application, directional terms such as "upper", "lower", "left", "right", "horizontal" and "vertical" are defined relative to the positions of the components in the drawings. It should be understood that these directional terms are relative concepts. They are used for relative description and clarification, and they can change accordingly according to the changes in the positions of the components in the drawings. Unless otherwise clearly specified and limited, the term "connection" should be understood in a broad sense, for example: "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium.

Meanwhile, in the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a concrete manner for ease of understanding.

First, the concepts involved in the embodiments of the present application are explained:

Energy density is defined as the amount of electrical energy stored per unit mass/volume of a lithium-ion battery.

Specific capacity refers to the amount of electricity that can be discharged by a unit mass of lithium-ion battery/positive electrode/negative electrode. Specific capacity is positively correlated with energy density. Specific capacity can include surface capacity and gram capacity.

Segmental motion, small-scale structural units such as segments, branches or side groups in macromolecules, internal rotation conformational changes and local molecular motion.

Glass transition temperature (Tg) refers to the temperature corresponding to the transition from glass state to highly elastic state. Tg is the lowest temperature at which molecular chain segments can move. With the continuous expansion of the electrochemical energy storage market and the power battery market, future application scenarios such as electric vehicles (EV) and energy storage fields have increasing requirements for the performance of secondary batteries (rechargeable batteries).

Lithium ion batteries (lithium ion cells and batteries) are secondary batteries that use lithium-containing compounds as positive electrodes. During the charge and discharge process, the lithium ions (Li+) ionized from the positive electrode are stripped and deposited back and forth between the positive and negative electrodes to achieve charge and discharge.

Room temperature, temperature is between 20℃ and 30℃.

Low temperature means the temperature is less than 20℃. High temperature means the temperature is greater than 30℃.

Please refer to FIG1 , a lithium ion cell and battery comprises a positive electrode 11, a negative electrode 12 and an electrolyte 13. The lithium ion cell and battery realizes charging/discharging by back and forth stripping and deposition of Li+ between the positive electrode 11 and the negative electrode 12.

The electrolyte 13 may include a solid electrolyte or a liquid electrolyte. Organic electrode liquid is a commonly used liquid electrolyte.

The organic electrode solution may include: a high-purity organic solvent and an electrolyte lithium salt, wherein the electrolyte lithium salt may be lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ) or the like.

The ternary cathode material or lithium iron phosphate (LiFePO ₄ ) cathode|organic electrolyte|graphite anode is a relatively mature lithium-ion battery. The energy density of the lithium-ion battery can reach 280Wh/kg to 300Wh/kg. Among them, the ternary cathode material can be but not limited to: lithium cobalt oxide (LiCoO ₂ ) lithium nickel cobalt manganese oxide (LiNi _x Co _y Mn _1-xy O ₂ ).

Lithium-ion batteries using organic electrode liquids can be called organic electrode liquid system lithium-ion batteries. The energy density of existing organic electrode liquid system lithium-ion batteries has reached its limit and it is difficult to break through the bottleneck.

On the one hand, the materials used for the positive electrode and the negative electrode have almost reached the limits of their respective theoretical specific capacities. On the other hand, the safety performance of lithium-ion batteries decreases as the positive/negative electrode materials with high activity and high specific capacity are used.

In order to adapt to different application scenarios, the energy density of lithium-ion batteries needs to be further improved. For example, in the application scenario of electric aircraft, the energy density of the battery needs to reach more than 400Wh/kg.

Further improvements can be made to the materials used in the negative electrode to further increase the energy density of lithium-ion batteries.

Since lithium metal has extremely high specific capacity (the specific capacity of lithium metal can reach 3860mAh/g) and low redox potential (the reduction potential of lithium metal can reach -3.04Vvs), the use of lithium metal in the negative electrode of lithium-ion batteries can greatly improve the energy density of lithium-ion batteries. Figure 2 shows the gram capacity of lithium-ion battery negative electrode materials and the theoretical volume energy density that can be achieved.

It can be seen that the negative electrode using graphite: the gram capacity can reach 680Wh/L, and the theoretical volume energy density can reach 360mAh/g. The negative electrode using graphite and 15% silicon oxide (SiOx): the gram capacity can reach 800Wh/L, and the theoretical volume energy density can reach 600mAh/g. The negative electrode using silicon: the gram capacity can reach 1005Wh/L, and the theoretical volume energy density can reach 2000mAh/g. The negative electrode using lithium metal: the gram capacity can reach 1000Wh/L, and the theoretical volume energy density can reach 3000mAh/g.

Since lithium metal has high chemical activity, applying lithium metal as the negative electrode material to a specific lithium-ion battery system also requires overcoming more problems. In the embodiment of the present application, the negative electrode using lithium metal can be referred to as a lithium metal negative electrode.

For example, due to the active chemical properties of lithium metal, side reactions easily occur when it comes into contact with electrolytes, resulting in low coulombic efficiency of lithium-ion batteries. Coulombic efficiency is defined as the ratio of the discharge capacity of a lithium-ion battery to the charge capacity during the same cycle.

Please continue to refer to FIG. 1 , for another example: in a lithium-ion battery using an organic electrolyte as an electrolyte, a separator 14 needs to be provided between the positive electrode 11 and the negative electrode 12. The separator 14 serves to isolate the positive electrode from the negative ^electrode , thereby ensuring electrical isolation between the positive electrode and the negative electrode.

During the charge and discharge process of the lithium-ion battery, the Li ⁺ in the lithium metal negative electrode 12 can combine with ^e- to form lithium atoms (Li). As the amount of Li gradually increases, lithium dendrites will grow on the surface of the lithium metal negative electrode 12. Among them, the lithium dendrites are branch-like lithium metals. The growth of lithium dendrites will penetrate the diaphragm 14, causing the positive electrode 11 to be conductive with the lithium metal negative electrode 12, and the lithium-ion battery will short-circuit. Therefore, lithium-ion batteries with lithium metal negative electrode/organic electrolyte systems have safety hazards.

One feasible method to apply lithium metal anode to lithium-ion battery system and solve the battery safety performance once and for all is to use solid electrolyte electrode (SSE) instead of organic electrolyte to form an all-solid-state lithium-ion battery.

Although solid electrolytes can solve the safety problem of lithium-ion batteries by replacing organic electrolytes, they also introduce the problem of poor contact at the solid-solid interface (the interface between the lithium metal negative electrode and the solid electrolyte). Especially during the lithium ion cycle, as the lithium metal negative electrode and the solid electrolyte surface undergo a reciprocating process of lithium stripping and deposition, the problem of poor contact at the solid-solid interface will continue to intensify.

In addition, the use of solid electrolytes cannot fundamentally prevent the growth of lithium dendrites. Lithium dendrites may penetrate the solid electrolyte to make the positive electrode 11 and the lithium metal negative electrode 12 conductive, causing a short circuit in the lithium-ion battery.

For example: Li ₇ La ₃ Zr ₂ O ₁₂ garnet type ceramic (LLZO) is a commonly used solid electrolyte material. When LLZO is used as a solid electrolyte, the relative density of LLZO is compacted to 98%, and lithium dendrites can still penetrate the solid electrolyte.

The prior art discloses some implementation schemes for suppressing the effects of lithium dendrites on lithium-ion batteries. The following is an explanation of the method for suppressing the effects of lithium dendrites on lithium-ion batteries in conjunction with specific drawings:

Prior art 1:

Prior art 1 discloses a membrane material, which can be used as a protective layer material in lithium-ion batteries. The protective layer is in contact with the lithium metal negative electrode, which can inhibit the formation of lithium dendrites on the surface of the lithium metal negative electrode and protect the solid electrolyte.

Please refer to FIG. 3 , in which (a) is a scanning electron microscope (SEM) of the negative electrode 31, the protective layer 32 and the solid electrolyte layer 33 in the lithium-ion battery at a scale of 3 μm. FIG. 3 (b) is a SEM of the protective layer and the solid electrolyte layer in the lithium-ion battery disclosed in the prior art 1 at a scale of 1 μm. Among them, the protective layer adopts the membrane material disclosed in the prior art 1. The protective layer 32 plays a role in protecting the solid electrolyte layer 33 to reduce the damage to the solid electrolyte layer 33 caused by the lithium dendrites generated nearby.

As can be seen from FIG. 3 (a) and FIG. 3 (b), the protective layer 32 is located between the negative electrode 31 and the solid electrolyte layer 33. The protective layer 32 is made of a polyethylene oxide/polyethylene oxide/polyethylene glycol (PEO)-PAS copolymer.

The chemical formula of PAS can be found in (iii) of Figure 3. It can be seen from (iii) of Figure 3 that the side chain of PAS itself has a sulfonic acid group 34, which can be combined with Li ⁺ 35, and no additional lithium salt or plasticizer is added to the material used in the protective layer.

Please refer to (iv) in Figure 3. (iv) in Figure 3 is the ion conductivity (conductivity)/lithium ion transfer number (transfer number)-temperature (temperature) curve of the protective layer; it can be seen that the ion conductivity of the protective layer can reach 10 ^-6 S/cm at room temperature.

The film material disclosed in the prior art 1 has the following problems:

(1) The formation of the protective layer requires the addition of a solvent to disperse PEO and PAS. After the protective layer is formed, the small molecule solvent is removed by heating. The above process is prone to small molecule solvent residues. The residue of small molecule solvents will affect the lithium ion cycle performance.

(2) When the protective film formed by the film material provided by the prior art 1 is applied to a lithium-ion battery, the interface impedance of the lithium metal negative electrode 31 - protective layer 32 - solid electrolyte layer 33 is relatively large, which can reach 600Ω·cm ² .

(3) The synthesis of PAS monomer is difficult and the cost of precursor is high.

Prior art 2:

Prior art 2 discloses a membrane material, which can be used as a solid electrolyte interface (SEI) material in lithium-ion batteries. SEI contacts the lithium metal negative electrode, which can inhibit the formation of lithium dendrites on the surface of the lithium metal negative electrode and play a role in protecting the diaphragm.

Please refer to FIG. 4 (a) and FIG. 4 (b), FIG. 4 (a) is a schematic diagram of a lithium metal negative electrode 41, a SEI 42 and a liquid electrolyte 43 in a lithium-ion battery.

Figure 4 (ii) is a scanning electron microscope image of the membrane material used for SEI42 in Figure 4 (a). Among them, (A) SEM of the membrane material at a scale of 100nm. (B) SEM of the membrane material at a scale of 50nm. (C) SEM of the membrane material at a scale of 2μm (top view). (D) SEM of the cross section of the membrane material at a scale of 2μm.

It can be seen that the membrane material includes: polyvinylidene fluoride (PVDF) matrix 421 and mesoporous silicon 422. Mesoporous silicon 422 can improve the Young's modulus of the PVDF matrix 421, so that SEI42 has higher toughness, and SEI42 can better inhibit the growth of lithium dendrites.

Li ⁺ can pass through the mesopores of the mesoporous silicon 422 and be deposited at the lithium metal negative electrode 41. For details, please refer to (iii) and (iv) in FIG. 4. (iii) in FIG. 4 is a schematic diagram of a lithium ion battery, wherein the SEI of the lithium ion battery adopts the membrane material disclosed in the second prior art. Li ⁺ can pass through the SEI42 and be deposited at the lithium metal negative electrode 41.

For details, please refer to (iv) in FIG4 , which is a schematic diagram of the membrane material. It can be seen that the mesopores of the mesoporous silicon 422 are larger than the particle size of Li ⁺ , and Li ⁺ can pass through the mesopores of the mesoporous silicon 422 and deposit on the lithium metal negative electrode 31.

The film materials disclosed in the prior art have the following problems:

(1) When the membrane material disclosed in the second prior art is used as SEI, it needs to be combined with a liquid electrolyte 43 with a high concentration of lithium salt.

(2) The film material needs to be coated on the surface of the lithium metal negative electrode 41. The above process is suitable for laboratory research at the buckle level and is difficult to apply to soft-pack batteries.

Existing technology three:

Prior art three discloses a solid electrolyte.

Please refer to FIG. 5 (a), which is a schematic diagram of a lithium-ion battery. The lithium-ion battery uses a solid electrolyte disclosed in prior art 3. It can be seen that the lithium-ion battery includes: a positive electrode 51, a solid electrolyte 52 and a negative electrode 53.

Please refer to FIG5(2), which is a schematic diagram of a solid electrolyte, wherein the solid electrolyte 52 is made of polyethylene glycol monomethyl ether methacrylate (PEGMA) 521 and bis(trifluoromethyl)sulfonyl imide (LiTFSI) 522.

Please refer to (iii) in Figure 5, which is a schematic diagram of the solid electrolyte synthesis process in (ii) in Figure 5. The formation process of the solid electrolyte 52 is: PEGMA521 and LiTFSI522 are dispersed in dimethyl sulfoxide (DMSO), and azobisisobutyronitrile (Azobisisobutyronitrile, AIBN) is used as an initiator to form the solid electrolyte 52 by in-situ cross-linking.

The polymer provided by the prior art three has the following problems:

(1) The lithium ion conductivity of the solid electrolyte 52 at room temperature (20°C to 30°C) is 2.7×10 ^-5 S/cm.

(2) The solid electrolyte 52 uses a high concentration of LISTFSI, which increases the cost of the solid electrolyte 52 and requires the additional addition of DMSO dispersant to form a uniform solution. DMSO may affect the cycle performance of the lithium-ion battery.

Prior art four:

Prior art 4 discloses a polymer electrolyte membrane. The morphology of the polymer electrolyte membrane can be seen in (a) of FIG. 6 . It can be seen that the polymer electrolyte membrane is in the form of a thin film. The polymer electrolyte membrane is obtained by cross-linking polyethylene glycol diacrylate (PEGDA), LiTFSI or lithium borate bis(oxalate) (LiBOB), and succinonitrile (SN) system.

Figure 6 (ii) is the lithium ion conductivity-temperature curve of the polymer electrolyte membrane. It can be seen that the lithium ion conductivity of the polymer electrolyte membrane can reach 0.76mS/cm at room temperature.

The polymer electrolyte membrane provided by the prior art 4 is applied as a solid electrolyte to a lithium-ion battery (the material used for the positive electrode of the lithium-ion battery is nickel-cobalt-aluminum oxide). The cycle performance of the lithium-ion battery is tested, and the experimental results obtained can be referred to (iii) in Figure 6, which shows that the lithium-ion battery has a better cycle performance.

The polymer electrolyte membrane provided by the prior art 4 has the following problems:

(1) SN is used as a plasticizer in polymer electrolyte membranes. This plasticizer easily forms plasticized crystals at low temperatures or under stress, changing the physical properties of the system.

(2) The polymer electrolyte membrane is soft, has low mechanical strength, and is difficult to self-support. Specifically, referring to (a) in FIG6 , it can be seen that the polymer electrolyte membrane is soft, has low mechanical strength, and is difficult to self-support.

(3) The polymer electrolyte membrane uses PEGDA. When the molecular weight of PEGDA is too high or the polymerization degree is too large, the local crystallization of the cross-linked system will show brittleness.

Existing electrolytes mostly use high molecular weight polymers, which have poor dispersion properties and require the addition of small molecule solvents to disperse them. The presence of small molecule solvents will have an adverse effect on the cycle performance of lithium-ion batteries. High molecular weight polymers have low Li ⁺ conductivity.

In order to solve the technical problems existing in the prior art, the present application provides a membrane material. The membrane material can be used as a protective layer between lithium metal and solid electrolyte. Referring to FIG. 7 , the membrane material includes: lithium salt 71, polyethylene glycol dimethacrylate 72 and sulfonamide compound 73.

Among them, lithium salt is used to provide Li ⁺ . Polyethylene glycol dimethacrylate 72 is used as the matrix of the membrane material. Polyethylene glycol dimethacrylate 72 contains ether bonds (COC), and each ether bond can be called a site. Polyethylene glycol dimethacrylate 72 molecules have segmental motion, which can drive the displacement of Li ⁺ between different sites, thereby realizing the migration of Li ⁺ .

In this implementation, the sulfonamide compound 73 can be used as a dispersant for the polyethylene glycol dimethacrylate 72, so that the sulfonamide compound 73, the polyethylene glycol dimethacrylate 72 and the lithium salt 71 can form a uniform system. The membrane material provided by this implementation does not need to use a small molecule solvent, so there will be no problems caused by the residual small molecule solvent.

There is an intermolecular force between the sulfonamide compound 73 and the ether bond in the polyethylene glycol dimethacrylate 72, and this intermolecular force can reduce the glass transition temperature of the polyethylene glycol dimethacrylate 72, thereby effectively promoting the segment movement of the polyethylene glycol dimethacrylate 72, and then improving the Li ⁺ conductivity of the film material. Since the glass transition temperature of the polyethylene glycol dimethacrylate 72 is reduced, the film material provided in the embodiment of the present application can show a large Li ⁺ conductivity at room temperature, low temperature and high temperature.

The film material has a large Li ⁺ conductivity. When it is applied to a lithium-ion battery, a serious charge layer will not be formed between the film formed by the film material and the positive/negative electrode of lithium ions. The film formed by the film material can form a stable interface with the positive/negative electrode, and the interface will not deteriorate with the deposition/stripping of lithium during the battery cycle. The thin film material provided in the embodiment of the present application has the effect of stabilizing lithium deposition/stripping.

The membrane material can undergo a cross-linking reaction, and the cross-linked system (membrane layer) obtained after cross-linking has a certain toughness and can inhibit the growth of lithium dendrites.

As a feasible implementation method, the membrane material has fluidity, so that the membrane material can be used in conjunction with the lithium-ion battery injection process.

The following is a further description of the components of the film material provided in the embodiments of the present application:

The membrane layer material includes: lithium salt 71.

In the embodiment of the present application, the lithium salt 71 is used to provide Li ⁺ .

The lithium salt 71 may include one of lithium bis(oxalatoborate) (LiBOB), lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), and lithium imide (LiFNFSI), or a mixture of the two or more thereof.

As a feasible implementation, the lithium salt 71 may also include lithium bis(trifluoromothanesulfonyl)imide (LiTFSI). LiTFSI contains fluoride ions (F ^- ).

^F- can react with lithium metal (Li) in the negative electrode during the charge and discharge process to form a SEI containing lithium fluoride (LiF) on the surface of the negative electrode. The SEI containing LiF can achieve uniform deposition of Li ⁺ in the negative electrode or uniform stripping of Li in the negative electrode.

Considering that the Li ⁺ conductivity of the membrane material is positively correlated with the Li ⁺ content in the membrane material, the greater the Li ⁺ content in the membrane material, the greater the lithium ion conductivity of the membrane material; the smaller the Li ⁺ content in the membrane material, the smaller the lithium ion conductivity of the membrane material.

Since the solubility of LiTFSI in polyethylene glycol dimethacrylate 72 is relatively low, the content of Li ⁺ in the membrane material will be limited if the lithium salt only contains LiTFSI.

In order to ensure the content of Li ⁺ in the membrane material. As a feasible implementation method, the lithium salt may include: LiTFSI and lithium bis(fluorosulfonyl)imide (LiFSI). Among them, the solubility of LiFSI in polyethylene glycol dimethacrylate 72 is greater than the solubility of LiTFSI in polyethylene glycol dimethacrylate 72. Therefore, in this implementation method, the lithium salt 71 includes: LiTFSI and LiFSI to ensure the content of Li ⁺ in the membrane material.

Under the premise that the mass of lithium salt 71 is constant, the greater the mass of LiFSI, the more Li ⁺ is dissolved in polyethylene glycol dimethacrylate 72, the greater the Li ⁺ content in the final film material, and the greater the Li ⁺ conductivity of the film material.

As a feasible implementation, the mass ratio of LiTFSI to LiFSI can be less than or equal to 2:1. Compared with the implementation in which the mass ratio of LiTFSI to LiFSI is greater than 2:1, the film material provided by this implementation contains more LiFSI. That is, more Li ⁺ is dissolved in polyethylene glycol dimethacrylate 72, and the film material has a larger Li ⁺ conductivity.

Under the premise of a certain mass of lithium salt, the greater the mass of LiTFSI, the more ^F- is dissolved in polyethylene glycol dimethacrylate 72, and the more SEI containing LiF can be formed when the membrane material is used in lithium-ion batteries.

As a feasible implementation, the mass ratio of LiTFSI to LiFSI can be greater than or equal to 1:2. Compared with the implementation in which the mass ratio of LiTFSI to LiFSI is less than 12, the film material provided by this implementation contains more LiTFSI. That is, more ^F- is dissolved in polyethylene glycol dimethacrylate 72. When the film material is used in a lithium-ion battery, more SEI containing LiF can be formed.

In order to take into account both the Li ⁺ conductivity of the membrane material and the ^F- content in the membrane material, as a feasible implementation method, the mass ratio of LiTFSI to LiFSI can be 1:2 to 2:1.

In the embodiment of the present application, the film layer material further includes: polyethylene glycol dimethacrylate 72 (poly-(ethylene glycol) dimethacrylate, PEGDMA).

Polyethylene glycol dimethacrylate 72 contains ether bonds (COC), and each ether bond can be called a site. Polyethylene glycol dimethacrylate 72 is used as the matrix of the membrane material. The polyethylene glycol dimethacrylate 72 molecule has segmental motion, which can drive the displacement of Li ⁺ between different sites, thereby realizing the migration of Li ⁺ .

As a feasible implementation method, the membrane layer material may include: polyethylene glycol monomethyl ether methacrylate (poly (ethylene glycol) methacrylate, PEGMA) 74.

The structural formula of PEGMA can be found in Figure 8A. It can be seen that PEGMA has a site for binding Li ⁺ . PEGMA also has a carbon-carbon double bond (C=C). PEGMA can be used as an end group during the cross-linking reaction of the membrane material to terminate the cross-linking reaction.

The structural formula of PEGDMA can be found in Figure 8B. It can be seen that PEGDMA has a site for binding Li ⁺ , and PEGDMA also has two carbon-carbon double bonds. PEGDMA can be used as a chain element in the cross-linking reaction of the membrane material, using two carbon-carbon double bonds to form a cross-linking system.

The cross-linking system formed by PEGDMA and PEGMA can be seen in Figure 9. It can be seen that PEGDMA serves as the chain link of the cross-linking system, and PEGMA serves as the end group of the cross-linking system.

As a feasible implementation, the molar ratio of PEGDMA to PEGMA can be greater than or equal to 1:10. Compared with the implementation in which the molar ratio of PEGDMA to PEGMA is less than 1:10, the membrane material provided by this implementation contains more PEGDMA, and more PEGDMA can be cross-linked to obtain a cross-linked system with a loose structure. Therefore, the membrane material provided by this implementation has a loose cross-linked system after cross-linking, and the cross-linked membrane material has a larger Li+ conductivity.

As a feasible implementation method, the molar ratio of PEGDMA to PEGMA can be less than or equal to 10:1. Compared with the implementation method in which the molar ratio of PEGDMA to PEGMA is greater than 10:1, the membrane material provided by this implementation method contains more PEGMA, and PEGMA can be used as an end group during the cross-linking reaction of the membrane material to terminate the cross-linking reaction. This implementation method can reduce the problem of local crystallization caused by the formation of a cross-linking system with a large degree of cross-linking during the cross-linking process. Therefore, the membrane material provided by this implementation method can avoid the occurrence of problem (3) in the fourth prior art.

In order to take into account both the Li+ conductivity of the cross-linked membrane material and reduce the crystallization problem of the cross-linked membrane material, as a feasible implementation method, the molar ratio of PEGDMA to PEGMA can be 1:10 to 10:1.

8A and 8B, PEGDMA and PEGMA can be referred to as polyethylene oxide polymers. Unless otherwise specified, the polyethylene oxide polymers in the embodiments of the present application include polyethylene glycol dimethacrylate, or polyethylene glycol dimethacrylate and ethylene glycol monomethyl ether methacrylate.

Considering that the more ether bonds there are in the membrane material, the more sites there are for Li+ transfer, and the better the Li+ conductivity of the membrane material.

Under the premise that the content of Li+ in the membrane material is constant, as a feasible implementation, the molar ratio of ether bonds to Li+ in the membrane material can be greater than or equal to 10. Compared with the implementation in which the molar ratio of ether bonds to Li+ in the membrane material is less than 10, the membrane material provided by this implementation contains more ether bonds, and more ether bonds can make the membrane material have a greater Li+ conductivity.

Considering that the more ether bonds there are in the membrane material, the greater the relative molecular mass of the polyethylene oxide polymer (72, 74) in the membrane material, or the greater the degree of polymerization of the polyethylene oxide polymer (72, 74), the greater the viscosity of the corresponding membrane material, the greater the technical difficulty of combining the membrane material with the lithium ion battery injection process.

Under the premise that the content of Li+ in the membrane material is constant. As a feasible implementation method, the molar ratio of ether bonds to Li+ in the membrane material can be less than or equal to 30. Compared with the implementation method in which the molar ratio of ether bonds to Li+ in the membrane material is greater than 30. The membrane material provided by this implementation method contains fewer ether bonds, that is, the relative molecular mass of the polyethylene oxide polymer (72, 74) in the membrane material is smaller, or the degree of polymerization of the polyethylene oxide polymer (72, 74) is smaller. Accordingly, the viscosity of the membrane material provided by this implementation method is lower, and the technical difficulty of combining the membrane material with the lithium-ion battery injection process is relatively small.

In order to take into account both the viscosity of the membrane material and the Li+ conductivity of the membrane material, as a feasible implementation method, the molar ratio of ether bonds to Li+ in the membrane material can be 10 to 30.

When the membrane material is applied to lithium-ion batteries, the polyethylene oxide polymers (72, 74) in the membrane material can be cross-linked to obtain a cross-linked system (membrane layer). The cross-linked system has a certain toughness and can inhibit the growth of lithium dendrites. The molecules in the cross-linked system have segmental motion, which can drive the displacement of Li+ between different sites, thereby realizing the migration of Li+.

Considering that the greater the degree of polymerization of the polyethylene oxide polymers (72, 74), the looser the cross-linked system structure formed after the polyethylene oxide polymers (72, 74) are cross-linked, the more significant the chain segment movement of the cross-linked system, and the greater the Li+ conductivity of the cross-linked system.

As a feasible implementation, the degree of polymerization of the polyethylene oxide polymer (72, 74) is greater than or equal to 4. Compared with the implementation of the polyethylene oxide polymer (72, 74) with a degree of polymerization less than 4, the membrane material in this implementation adopts a polyethylene oxide polymer (72, 74) with a larger degree of polymerization. The cross-linked system structure formed by the polyethylene oxide polymer (72, 74) with a larger degree of polymerization is loose after cross-linking, the chain segment movement of the cross-linked system is more significant, and the Li+ conductivity of the cross-linked system is larger. In the embodiment of the present application, the cross-linked system can also be referred to as the membrane material or membrane layer after cross-linking.

Considering that the greater the degree of polymerization of the polyethylene oxide polymers (72, 74), the lower the fluidity of the polyethylene oxide polymers (72, 74), the lower the fluidity of the final membrane material, and the greater the technical difficulty of combining the membrane material with the lithium-ion battery injection process.

As a feasible implementation, the degree of polymerization of the polyethylene oxide polymer (72, 74) can be less than or equal to 12. Compared with the implementation using polyethylene oxide polymers (72, 74) with a degree of polymerization greater than 12, the membrane material in this implementation uses polyethylene oxide polymers (72, 74) with a smaller degree of polymerization, the membrane material has greater fluidity, and the technical difficulty of combining the membrane material with the lithium ion battery injection process is relatively low.

In order to take into account both the fluidity of the membrane material and the Li+ conductivity of the cross-linked membrane material, as a feasible implementation method, the degree of polymerization of the polyethylene oxide polymer (72, 74) can be 4-12.

Considering that the larger the relative molecular mass of the polyethylene oxide polymers (72, 74), the stronger the toughness of the cross-linked system formed after the polyethylene oxide polymers (72, 74) are cross-linked, the stronger the toughness of the cross-linked system, the stronger the inhibitory effect of the cross-linked system on lithium dendrites.

As a feasible implementation, the relative molecular weight of the polyethylene oxide polymer (72, 74) can be greater than or equal to 300. Compared with the implementation using polyethylene oxide polymers (72, 74) with a relative molecular weight less than 300, the membrane material in this implementation uses polyethylene oxide polymers (72, 74) with a larger relative molecular weight. The cross-linked system formed after cross-linking of the membrane material provided by this implementation has greater toughness. When applied to lithium-ion batteries, the cross-linked system can have a strong inhibitory effect on lithium dendrites.

Considering that the larger the relative molecular mass of the polyethylene oxide polymers (72, 74), the smaller the fluidity of the polyethylene oxide polymers (72, 74), the smaller the fluidity of the film material finally obtained.

As a feasible implementation, the relative molecular mass of the polyethylene oxide polymer (72, 74) is less than or equal to 600. Compared with the implementation using polyethylene oxide polymers (72, 74) with a relative molecular mass greater than 600, the membrane material in this implementation uses polyethylene oxide polymers (72, 74) with a smaller relative molecular mass. The membrane material provided by this implementation has greater fluidity, and the technical difficulty of combining the membrane material with the lithium ion battery injection process is relatively low.

In order to take into account both the fluidity of the membrane material and the toughness of the cross-linked system formed after cross-linking, as a feasible implementation method, the relative molecular weight of the polyethylene oxide polymer (72, 74) can be 300-600.

In the embodiment of the present application, the membrane layer material further includes: a sulfonamide compound 73.

Please refer to Figure 10, which is a structural formula of a sulfonamide compound provided in a feasible implementation. It should be noted that Figure 10 is only an exemplary introduction of a molecular structural formula of a sulfonamide compound 73 with an asymmetric structure, and the above molecular structural formula does not constitute a limitation.

In Fig. 10, _R1 , _R2 , _R3 , and _R4 are substituents of the sulfonamide compound 73. In the embodiment of the present application, the types of the substituents of the sulfonamide compound 73 are not specifically limited.

In order to prevent the sulfonamide compound 73 from reducing its plasticizing properties due to crystallization, as a feasible implementation method, the substituent of the sulfonamide compound 73 can be a short-chain substituent. The short-chain substituent can be, but is not limited to, any one of a methyl group, an ethyl group or an ether group.

As a feasible implementation method, sulfonamide compound 73 has an asymmetric molecular structure.

Generally, sulfonamide compounds with symmetrical molecular structures are prone to close stacking of molecules to form a local structure of plasticized crystals. This plasticized crystal structure is usually formed at low temperatures or under stress. The formation of plasticized crystals will reduce the plasticizing properties of sulfonamide compounds.

Sulfonamide compound 73 has an asymmetric molecular structure. Compared with sulfonamide compounds with symmetric molecular structures, sulfonamide compound 73 with an asymmetric molecular structure is not easy to form close stacking between molecules, and sulfonamide compound 73 is not easy to form a local structure of plasticized crystals. Therefore, sulfonamide compound 73 has greater plasticizing performance.

The plasticizing properties of the sulfonamide compound 73 are specifically manifested as follows: there is an intermolecular force between the sulfonamide compound 73 and the ether bonds in the polyethylene oxide polymers (72, 74), and this intermolecular force can reduce the glass transition temperature of the polyethylene oxide polymers, so that the polyethylene oxide polymers (72, 74) have greater chain segment movement at both low and room temperatures, and the film material has greater Li+ conductivity at both room and low temperatures.

Problem (1) in the solution provided by the prior art 2 and problem (2) in the solution provided by the prior art 3 point out the need to use a high concentration of lithium salt. In the membrane material provided by the embodiment of the present application, the plasticizing property of the sulfonamide compound 73 on the polyethylene oxide polymer (72, 74) can improve the migration performance of Li ⁺ in the polyethylene oxide polymer (72, 74). Therefore, the mass fraction of the lithium salt used in the membrane material provided by the embodiment of the present application can be less than or equal to 25%.

In the embodiment of the present application, the sulfonamide compound 73 also acts as a dispersant. Specifically, the sulfonamide compound 73 can make the polyethylene oxide polymer (72, 74) and the lithium salt 71 mixed to form a uniform solution. Compared with the problem (1) in the solution provided in the prior art one and the problem (2) in the solution provided in the prior art three. The membrane material provided in the embodiment of the present application does not require the introduction of additional small molecule dispersants. When the membrane material provided in the embodiment of the present application is applied to a lithium ion battery, there will be no problem of residual small molecule solvents affecting the cycle performance of the lithium ion battery. Therefore, the membrane material provided in the embodiment of the present application is applied to a lithium ion battery, and the lithium ion battery can have better cycle performance.

Considering that the greater the mass fraction of the sulfonamide compound 73 in the membrane material, the more significant the plasticizing property of the sulfonamide compound 73 on the polyethylene oxide polymer (72, 74), the more significant the segment movement of the polyethylene oxide polymer (72, 74), and the greater the Li ⁺ conductivity of the membrane material.

As a feasible implementation, the mass fraction of the sulfonamide compound 73 in the film material can be greater than or equal to 40%. Compared with the film material having a mass fraction of the sulfonamide compound 73 less than 40%, the film material provided by the present implementation contains more sulfonamide compounds 73, and more sulfonamide compounds 73 have more significant plasticizing properties on the polyethylene oxide polymers (72, 74), thereby making the polyethylene oxide polymers (72, 74) have better segment motion, and accordingly, the film material has a greater Li ⁺ conductivity.

Considering that the greater the mass fraction of the sulfonamide compound 73 in the membrane material, the smaller the viscosity of the membrane material, the greater the difficulty in coating the membrane material on the surface of the solid electrolyte during the formation of the lithium-ion battery.

As a feasible implementation, the mass fraction of the sulfonamide compound 73 in the membrane material can be less than or equal to 60%. Compared with the membrane material having a mass fraction of the sulfonamide compound 73 greater than 60%, the membrane material provided by this implementation contains less sulfonamide compound 73. Less sulfonamide compound 73 can make the membrane material have greater viscosity, and in the formation process of the lithium-ion battery, the membrane material provided by this implementation is less difficult to coat on the surface of the solid electrolyte.

In order to take into account both the viscosity of the membrane material and the Li ⁺ conductivity of the membrane material, as a feasible implementation method, the mass fraction of the sulfonamide compound 73 can be 40% to 60%.

As a feasible implementation method, the membrane layer material may also include: diaphragm material.

In the embodiment where the membrane material includes a diaphragm material, the material composed of lithium salt, polyethylene oxide polymer (72, 74), and sulfonamide compound can be referred to as a polymer material.

The diaphragm material has the function of allowing Li ⁺ to pass through and isolating e ^- , so that the membrane layer containing the diaphragm material has the function of allowing Li ⁺ to pass through and isolating e ^- . The diaphragm material includes: polypropylene (PP), celluloid or other porous lithium-ion battery diaphragm materials.

Among the materials currently disclosed for preparing solid electrolytes, the content of lithium salt is between 8% and 35%. Among them, the corresponding lithium ion conductivity of the material with less lithium salt content is lower. The sulfonamide compound in the film material provided in the embodiment of the present application can be used as a plasticizer for polyethylene glycol dimethacrylate, and there is an intermolecular force between the sulfonamide compound and the ether bond in polyethylene glycol dimethacrylate. This intermolecular force can increase the glass transition temperature of polyethylene glycol dimethacrylate, thereby effectively promoting the segment movement of polyethylene glycol dimethacrylate, so that the film material has better Li ⁺ conductivity. The lithium salt of the film material provided in the embodiment of the present application can be controlled to be less than 25%, and the lithium ion conductivity of the film material can reach 6.2× ^10-4 S/cm at room temperature.

At present, the disclosed materials for preparing solid electrolytes are used in lithium-ion batteries. The cycle performance test of lithium-ion batteries needs to be carried out at high temperatures. The membrane material provided in the embodiments of the present application is applied to lithium-ion batteries, and the battery performance test can be carried out at room temperature.

The film material has a large Li ⁺ conductivity. When it is applied in a lithium-ion battery, no serious charge layer will be formed between the film layer formed by the film material and the positive/negative electrode of the lithium ion. The film layer and the positive/negative electrode can form a stable interface, and the interface will not deteriorate with the deposition/stripping of lithium during the battery cycle. The thin film material provided in the embodiment of the present application has the effect of stabilizing lithium deposition/stripping. The specific mechanism of action may be the three-dimensional lithium deposition sites formed after the cross-linking of the film material, which makes the deposition of lithium metal more uniform; another possible explanation is that the fluorine element in the lithium salt will react with lithium metal during the charge and discharge process to form a LiF-rich SEI film on the surface of lithium metal, thereby achieving uniform deposition and stripping of lithium metal. This makes the lithium-ion battery have stable cycle performance. For example: it can cycle for 1400 hours at a current density of 0.2mA/ ^cm2 .

The sulfonamide compound in the membrane material provided in the embodiment of the present application can be used as a polyethylene oxide polymer dispersant, so that the sulfonamide compound, polyethylene oxide polymer, and lithium salt can form a uniform system. The membrane material provided in this implementation does not need to use a small molecule solvent, so there will be no problems caused by the residue of the small molecule solvent.

In the film material provided in the embodiment of the present application, the polyethylene oxide polymer can undergo a cross-linking reaction, so that the film material is converted into a solid film. The effect of the film material provided in the embodiment of the present application is described below with reference to specific examples:

Example 1: The contents of the components of the film layer material can be found in Table 1.

Table 1

Components Mass fraction (%) PEGMA (Mn = 550 g/mol) 6 PEGDMA (Mn = 500 g/mol) 17 Sulfonamide compounds (EMSA) 52 LiTFSI 15 LiFSI 10

The comparative example is: polyethylene glycol diacrylate (PEGDA) + 30% lithium salt.

The cross-linked polymerized product of the membrane material provided in Example 1 and the cross-linked polymerized product of the comparative example are respectively applied as solid electrolytes to the lithium-ion battery provided in FIG. 11 .

For the sake of distinction, the lithium-ion battery using the membrane material provided in the embodiment of the present application is referred to as a first lithium-ion battery, and the lithium-ion battery using the comparative example is referred to as a second lithium-ion battery.

The cycle performance of the first lithium ion battery and the second lithium ion battery was tested at 70° C. and a current density of 200 mAh/cm ^2. The test results can be seen in FIG12 .

FIG12 (a) is a potential-cycle time curve of the first lithium ion battery. FIG12 (b) is a potential-cycle time curve of the second lithium ion battery. It can be seen that the first lithium ion battery has better cycle performance. The second lithium ion battery has poor cycle performance.

Second, the formation of solid electrolyte in lithium-ion battery requires the addition of small molecule solvent or dispersant, so the small molecule solvent or dispersant needs to be removed after the solid electrolyte is formed. The residual small molecule solvent or dispersant will affect the cycle performance of lithium-ion battery.

The membrane material provided in the embodiment of the present application does not require the addition of a small molecule solvent or dispersant, so there is no need to add a solvent volatilization process after the cross-linking polymerization of the membrane material, and there will be no small molecule solvent residue. Therefore, the solid electrolyte formed by the membrane material provided in the embodiment of the present application is applied to a lithium-ion battery, and the lithium-ion battery can have good cycle performance.

The membrane material provided in Example 1 is applied as a liquid electrolyte to the lithium ion battery provided in FIG. 11 to obtain a third lithium ion battery.

The cycle performance of the third lithium-ion battery was tested at a current density of 0.05 mAh/cm ² and a current density of 0.2 mAh/cm ^2. The test results can be seen in FIG13 .

Figure 13 (a) is a potential-cycle time curve of the third lithium ion battery at a current density of 0.05 mAh/cm ^2. Figure 13 (b) is a potential-cycle time curve of the third lithium ion battery at a current density of 0.2 mAh/cm ^2. It can be seen that the membrane material provided in the embodiment of the present application is applied as a liquid electrolyte in a lithium ion battery, and the lithium ion battery can also have good cycle performance.

Embodiment 2:

The membrane layer obtained by cross-linking a membrane material having a molar ratio of LiFSI to LiTFSI of 1:1 and a molar ratio of ether bonds to lithium ions of 20 was used as a solid electrolyte in the lithium ion battery provided in FIG. 11 to obtain a fourth lithium ion battery.

The lithium ion migration number and interface impedance of the fourth lithium ion battery were tested. The test results can be seen in Figure 14. 70%, 30%, and 50% in Figure 14 are the mass fractions of EMSA/PEGDA in the system composed of EMSA and PEGDA.

Figure 14 (a) is an ionic conductivity-temperature curve of the fourth lithium ion battery. Figure 14 (b) is an interface impedance-temperature curve of the fourth lithium ion battery.

The room temperature lithium ion conductivity of the cross-linked system obtained by cross-linking PEGDA with the addition of EMSA is increased from the original 10 ^-6 S/cm to 10 ^-5 S/cm (without EMSA) to 10 ^-4 S/cm.

After adding EMSA, the interface impedance between the solid electrolyte and the lithium metal negative electrode is also improved to a certain extent with the increase of EMSA content. Specifically, it can be seen from (ii) in Figure 14 that the interface impedance of the lithium ion battery with 70% EMSA is less than that of the lithium ion battery with 50% EMSA at 20°C to 30°C.

The present application also provides a membrane layer, which is used to protect the solid electrolyte. Please refer to Figure 15, which is a schematic diagram of the membrane layer provided in the present application. The membrane layer uses the membrane layer material provided in the present application, and the membrane layer material may include: lithium salt, polyethylene oxide polymer and sulfonamide compound.

The film layer adopts the film layer material provided in the embodiment of the present application, so the film layer has the effects of the above-mentioned film layer material.

The membrane layer provided in the embodiment of the present application can be used as a protective layer of a solid electrolyte in a lithium-ion battery. The protective layer can be arranged between the positive electrode and the solid electrolyte, and/or between the negative electrode and the solid electrolyte of the lithium-ion battery.

The solid electrolyte may be, but is not limited to, an oxide ceramic solid electrolyte material, a sulfide solid electrolyte material, or the like.

As a feasible implementation, the protective layer has self-supporting properties, please refer to Figure 16. Figure 16 is a schematic diagram of a protective layer provided by a feasible embodiment. It can be seen that the protective layer 162 is clamped by the clip 161, and the protective layer 162 can be independently supported, that is, the protective layer 162 has self-supporting properties.

In this implementation, the protective layer 162 has a self-supporting property. When the protective layer 162 is applied to a lithium-ion battery, the protective layer 162 has a self-supporting property and is not prone to wrinkles. Therefore, the problem of conduction between the positive and negative electrodes of the lithium-ion battery caused by wrinkles in the protective layer 162 can be reduced. The protective layer 162 provided in the embodiment of the present application can overcome the problem (2) in the fourth prior art.

The protective layer 162 has a certain toughness after being cross-linked with the film material provided in the embodiment of the present application. Therefore, the protective layer 162 can inhibit the growth of lithium dendrites, and further reduce the problem of short circuit between the positive electrode and the negative electrode caused by lithium dendrites penetrating the solid electrolyte to a certain extent.

The protective layer provided in the embodiment of the present application does not contain metals such as lanthanum and zirconium. Even if it is used in a lithium-ion battery using a lithium metal negative electrode, the protective layer and the lithium metal have fewer side reactions. The protective layer has a large Li ⁺ conductivity, and no serious charge layer is formed between the protective layer and the negative electrode. The protective layer and the negative electrode can form a stable interface, and the interface will not deteriorate with the deposition/stripping of lithium during the battery cycle. After multiple cycles of charge and discharge, the protective layer provided in the embodiment of the present application can still have a relatively stable interface with the lithium metal negative electrode. The lithium-ion battery using the protective layer provided in the embodiment of the present application can still have a small interface impedance after multiple cycles of charge and discharge.

The present application also provides a membrane layer. Please refer to FIG. 17, which is a schematic diagram of the membrane layer provided in the present application. The membrane layer uses the membrane layer material provided in the present application. The membrane layer material includes: a diaphragm material, a lithium salt, a polyethylene oxide polymer, and a sulfonamide compound.

The film layer provided in the embodiment of the present application can be used as a composite solid electrolyte in a lithium-ion battery. The composite solid electrolyte can be arranged between the positive electrode and the negative electrode of the lithium-ion battery. Compared with the solid electrolyte of LLZO, the composite solid electrolyte provided in the embodiment of the present application does not contain metals such as lanthanum zirconium. Even if it is used in a lithium-ion battery using a lithium metal negative electrode, the composite solid electrolyte has fewer side reactions with lithium metal. The composite solid electrolyte has a large Li+ conductivity, and a serious charge layer will not be formed between the composite solid electrolyte and the positive electrode/negative electrode. The composite solid electrolyte and the positive electrode/negative electrode can form a stable interface, which will not deteriorate with the deposition/stripping of lithium during the battery cycle. After multiple cycles of charge and discharge, the composite solid electrolyte provided in the embodiment of the present application can still have a relatively stable interface with the positive electrode/negative electrode. The lithium-ion battery using the composite solid electrolyte provided in the embodiment of the present application can still have a small interface impedance after multiple cycles of charge and discharge.

As a feasible implementation, the composite solid electrolyte has self-supporting properties, please refer to Figure 16. Figure 16 is a schematic diagram of a composite solid electrolyte provided by a feasible embodiment. It can be seen that the composite solid electrolyte 162 is clamped by the clamp 161, and the composite solid electrolyte 162 can be independently supported, that is, the composite solid electrolyte 162 has self-supporting properties. The membrane layer provided by this implementation can overcome the problem (2) in the fourth prior art.

In this implementation, the composite solid electrolyte has self-supporting properties, and the composite solid electrolyte is applied between the positive electrode and the negative electrode in the lithium-ion battery. The composite solid electrolyte is not prone to wrinkles, so the conduction problem between the positive electrode and the negative electrode of the lithium-ion battery caused by the wrinkles of the composite solid electrolyte can be reduced.

The present application also provides a lithium-ion battery, as shown in FIG18 , which includes a positive electrode 181 , a negative electrode 182 , a solid electrolyte 183 , and at least one protective layer 184 . The solid electrolyte 183 is disposed between the positive electrode 181 and the negative electrode 182 .

It is worth noting that FIG18 only exemplarily shows the stacking relationship between the positive electrode 181, the negative electrode 182, the solid electrolyte 183 and the protective layer 184. In actual application, the positive electrode 181, the negative electrode 182, the solid electrolyte 183 and the protective layer 184 are bonded together according to the stacking relationship shown in FIG18.

Please refer to (a) in FIG. 18 . As a feasible implementation method, the protective layer 184 is disposed between the solid electrolyte 183 and the positive electrode 181 .

Please refer to (ii) in FIG. 18 . As a feasible implementation method, the protective layer 184 is disposed between the solid electrolyte 183 and the negative electrode 182 .

Please refer to (iii) in FIG. 18 , as a feasible implementation method, one protective layer 184 (1) is disposed between the solid electrolyte 183 and the positive electrode 181 , and another protective layer 184 (2) is disposed between the solid electrolyte 183 and the negative electrode 182 .

In the lithium-ion battery provided in the embodiment of the present application, a solid electrolyte 183 is disposed between the positive electrode 181 and the negative electrode 182, and the solid electrolyte 183 allows Li+ to pass through and isolates e-, thereby ensuring electrical isolation between the positive electrode 181 and the negative electrode 182.

The protective layer 184 is made of the film material provided in the embodiment of the present application, which may include: lithium salt, polyethylene oxide polymer and sulfonamide compound.

Polyethylene oxide polymers as the matrix of the membrane material contain ether bonds. Ether bonds can be used as sites to combine with lithium salts to provide Li+. Polyethylene oxide polymer molecules have segmental motion, which can drive the displacement of Li+ between different sites, thereby realizing the migration of Li+ between the positive and negative electrodes.

Sulfonamide compounds can also be used as plasticizers for polyethylene oxide polymers. There is an intermolecular force between sulfonamide compounds and the ether bonds in polyethylene oxide polymers. This intermolecular force can reduce the glass transition temperature of polyethylene oxide polymers, thereby effectively promoting the chain segment movement of polyethylene oxide polymers, so that the protective layer 184 has better Li ⁺ conductivity.

The protective layer 184 has a large Li ⁺ conductivity. When it is used in a lithium-ion battery, no serious charge layer is formed between the protective layer 184 and the positive electrode 181/negative electrode 182. The protective layer 184 and the positive electrode 181/negative electrode 182 can form a stable interface, which will not deteriorate with the deposition/stripping of lithium during the battery cycle, so that the lithium-ion battery has stable cycle performance.

The protective layer 184 is formed by cross-linking the film material, and the protective layer 184 is in a solid state. Compared with lithium-ion batteries using liquid electrolytes, the lithium-ion batteries provided in the embodiments of the present application can avoid safety issues caused by leakage of liquid electrolytes.

The protective layer 184 has a certain toughness, which can inhibit the growth of negative electrode lithium dendrites and play a role in protecting the solid electrolyte 183, thereby improving the safety performance of the lithium-ion battery.

The protective layer 184 formed by the cross-linked film material has a certain toughness, and the protective layer 184 can inhibit the growth of lithium dendrites and protect the solid electrolyte 183. Therefore, the lithium ion battery provided in the embodiment of the present application can use a lithium metal negative electrode with a higher specific capacity. This ensures that the lithium ion battery provided in the embodiment of the present application has a higher energy density.

Since the positive electrode 181 and/or the negative electrode 182 in the lithium-ion battery provided in the embodiment of the present application are in contact with the protective layer 184. The protective layer 184 does not contain metals such as lanthanum and zirconium. Even if the negative electrode 182 of the lithium-ion battery uses lithium metal, the protective layer 184 has fewer side reactions with the lithium metal, and the protective layer 184 has a larger Li ⁺ conductivity. A serious charge layer will not be formed between the protective layer 184 and the positive electrode 181/negative electrode 182. The lithium-ion battery provided in the embodiment of the present application can still have a relatively stable interface after multiple charge and discharge cycles. The lithium-ion battery provided in the embodiment of the present application can still have a small interface impedance after multiple charge and discharge cycles.

The lithium-ion battery provided in the embodiment of the present application is further described below in conjunction with specific drawings:

As an implementation, in the lithium-ion battery provided in FIG18 , the positive electrode 181 is LiFeO ₄ ; the negative electrode 182 is lithium metal; the solid electrolyte 183 is LLZO; and the protective layer 184 is the film material (PE) provided in the embodiment of the present application. The lithium-ion battery provided in this implementation can be referred to as Li|PE|LLZO|PE|Li.

In Comparative Example 1, LLZO is disposed between the positive electrode and the negative electrode. The lithium ion battery provided in Comparative Example 1 can be expressed as Li|LLZO|Li.

The impedance of Li|LLZO|Li and Li|PE|LLZO|PE|Li was tested, and the test results can be seen in Figure 19.

Figure 19 (a) is a Li|LLZO|Li imaginary impedance-real impedance curve. Figure 19 (b) is a Li|PE|LLZO|PE|Li imaginary impedance-real impedance curve.

In Figure 19 (a), the imaginary impedance of Li|LLZO|Li in the range of 2000 ohm.cm ² to 5000 ohm.cm ² is the interface impedance between the solid electrolyte and the lithium metal negative electrode. It can be seen that the interface impedance of Li|LLZO|Li is 2020 Ω.cm ² .

The imaginary impedance of Li|PE|LLZO|PE|Li in the range of 200 ohm.cm ² to 650 ohm.cm ² in FIG. 19 (B) is the interface impedance between the protective layer and the lithium metal negative electrode. It can be seen that the interface impedance of Li|PE|LLZO|PE|Li is 300 Ω.cm ^2. The lithium ion battery provided by this implementation has a small interface impedance.

The lithium-ion battery protective layer provided by this implementation does not contain any extra small molecule solvent or dispersant molecules, so there is no need to add an additional solvent volatilization process after cross-linking, and there will be no small molecule solvent residue. The residual solvent molecules or small molecule polymer reaction precursors may affect the performance of the battery during the cycle.

The cycle performance of Li|LLZO|Li and Li|PE|LLZO|PE|Li was tested, and the test results can be seen in Figures 20 and 21.

Figure 20 (a) is the potential-cycle time relationship curve of Li|LLZO|Li at 40°C and a surface capacity of 0.1 mAh/ ^cm2 . Figure 20 (b) is a schematic diagram of LLZO after Li|LLZO|Li cycled for 120 hours.

As can be seen from Figure 20 (a), after about 30 hours of cycling, Li|LLZO|Li experienced a short circuit. In Figure 20 (b), a large amount of byproducts with lithium metal were deposited on the surface of LLZO.

Figure 21 (a) is the potential-cycle time relationship curve provided by Li|PE|LLZO|PE|Li at 40°C and surface capacity of 0.1 mAh/ ^cm2 . It can be seen that after 800 hours of cycling at a higher temperature (40°C), Li|PE|LLZO|PE|Li still has good cycle performance, that is, after multiple charge and discharge cycles, the protective layer and the lithium metal negative electrode can still have a relatively stable interface.

The potential-cycle time relationship curves obtained from the two experiments are almost the same. It can be seen that the lithium-ion battery provided in the embodiment of the present application has repeatability.

Figure 21 (ii) is the potential-cycle time relationship curve provided by Li|PE|LLZO|PE|Li at 25°C and a surface capacity of 0.1 mAh/ ^cm2 . It can be seen that after 1000 hours of cycling at room temperature (25°C), Li|PE|LLZO|PE|Li still has good cycle performance, that is, after multiple charge and discharge cycles, the protective layer and the lithium metal negative electrode can still have a relatively stable interface.

Li|PE|LLZO|PE|Li showed a smaller potential (0.05V) in the cycle performance test, compared with other polymer systems in previous literature (the overpotential is large and very unstable, and the potential will continue to expand as the cycle progresses). The protective layer in Li|PE|LLZO|PE|Li adopts the film material provided in the embodiment of the present application. The film material has a large Li+ conductivity and lithium ion migration number, and will not produce a serious charge layer during the battery cycle. Therefore, the overpotential measured by Li|PE|LLZO|PE|Li is small. The protective layer can form a stable interface with the lithium metal negative electrode, and the interface will not deteriorate with the deposition/stripping of lithium during the battery cycle. After multiple charge and discharge cycles of Li|PE|LLZO|PE|Li, the protective layer and the lithium metal negative electrode can still have a relatively stable interface.

The present application also provides a lithium-ion battery. Referring to FIG. 22 , the lithium-ion battery includes: a positive electrode 221, a negative electrode 222; and a composite solid electrolyte 223. The composite solid electrolyte 223 can be disposed between the positive electrode 221 and the negative electrode 222. The composite solid electrolyte 223 uses the membrane material provided in the present application, and the membrane material includes: lithium salt, polyethylene oxide polymer, diaphragm material, and sulfonamide compound.

It is worth noting that FIG22 only exemplarily shows the stacking relationship between the positive electrode 221, the negative electrode 222, and the composite solid electrolyte 223. In actual application, the positive electrode 221, the negative electrode 222, and the composite solid electrolyte 223 are bonded together according to the stacking relationship shown in FIG22.

The diaphragm material has the function of allowing Li ⁺ to pass through and isolating e ^- . Therefore, the composite solid electrolyte 223 has the function of allowing Li ⁺ to pass through and isolating e ^- , thereby ensuring the electrical isolation between the positive electrode 221 and the negative electrode 222.

Sulfonamide compounds can be used as polyethylene glycol dimethacrylate dispersants, so that sulfonamide compounds, polyethylene glycol dimethacrylate and lithium salt can form a uniform system. The membrane material provided by this implementation does not need to use small molecule solvents, so there will be no problems caused by residual small molecule solvents.

Sulfonamide compounds can also be used as plasticizers for polyethylene glycol dimethacrylate. There is an intermolecular force between sulfonamide compounds and the ether bonds in polyethylene glycol dimethacrylate. This intermolecular force can increase the glass transition temperature of polyethylene glycol dimethacrylate, thereby effectively promoting the chain segment movement of polyethylene glycol dimethacrylate, so that the composite solid electrolyte has better Li ⁺ conductivity.

The composite solid electrolyte 223 has a large Li ⁺ conductivity. When it is used in a lithium-ion battery, no serious charge layer is formed between the composite solid electrolyte 223 and the positive electrode/negative electrode. The composite solid electrolyte 223 and the positive electrode/negative electrode can form a stable interface, which will not deteriorate with the deposition/stripping of lithium during the battery cycle, so that the lithium-ion battery has a stable cycle performance.

The composite solid electrolyte 223 is formed by cross-linking the membrane material. The composite solid electrolyte 223 is solid. Compared with the lithium-ion battery using liquid electrolyte, the lithium-ion battery provided in the embodiment of the present application can reduce the safety problems caused by leakage of liquid electrolyte.

The composite solid electrolyte 223 has a certain toughness and can inhibit the growth of negative electrode lithium dendrites. Therefore, the lithium-ion battery provided in the embodiment of the present application can use a lithium metal negative electrode with a higher specific capacity, thereby ensuring that the lithium-ion battery has a higher energy density.

The positive electrode 221/negative electrode 222 of the lithium-ion battery provided in the embodiment of the present application is in contact with the composite solid electrolyte 223. The composite solid electrolyte 223 does not contain metals such as lanthanum and zirconium. Even if the negative electrode 222 of the lithium-ion battery adopts lithium metal, the composite solid electrolyte 223 and the lithium metal have fewer side reactions. After multiple cycles of charge and discharge, the composite solid electrolyte 223 and the positive electrode 221/negative electrode 222 can still have a relatively stable solid-solid interface. The lithium-ion battery provided by the embodiment of the present application can still have a small interface impedance after multiple cycles of charge and discharge.

The lithium-ion battery provided in the embodiment of the present application is further described below in conjunction with specific drawings:

As a feasible implementation method, the separator material in the lithium-ion battery provided in FIG22 can be referred to as composite PE, and the lithium-ion battery provided in FIG22 can be referred to as a Li|composite PE|Li symmetric battery. The cycle performance of the Li|composite PE|Li symmetric battery was tested at 25°C and 40°C. The test results can be found in FIG23 and FIG24.

Figure 23 (a) is the potential-cycle time curve provided by the Li|composite PE|Li symmetric battery at 40°C and a surface capacity of 2 mAh/cm ^2. It can be seen that after 1100 cycles at a relatively high temperature (40°C), the Li|composite PE|Li symmetric battery still has good cycle performance, that is, after multiple charge and discharge cycles, the composite solid electrolyte and the positive electrode 221/negative electrode 222 can still have a relatively stable solid-solid interface.

FIG23 (ii) shows another Li|composite PE|Li symmetric battery at 40°C and a surface capacity of 2 mAh/ ^cm2 , and shows a potential-cycle time curve provided by Li|composite PE|Li. The relationship curve provided by FIG23 (i) is almost the same as the relationship curve provided by FIG23 (ii). It can be seen that the lithium-ion battery provided in the embodiment of the present application has repeatability.

Figure 24 (a) is the potential-cycle time curve provided by Li|composite PE|Li for the Li|composite PE|Li symmetric battery at 25°C and a surface capacity of 2 mAh/ ^cm2 . It can be seen that after 1100 hours of cycling at 25°C, Li|composite PE|Li still has good cycle performance, that is, after multiple charge and discharge cycles, the composite solid electrolyte and the positive electrode 221/negative electrode 222 can still have a relatively stable solid-solid interface.

FIG24 (ii) shows another Li|composite PE|Li symmetric battery at 25°C and a surface capacity of 2 mAh/ ^cm2 , and shows a potential-cycle time curve provided by Li|composite PE|Li. The relationship curve provided by FIG24 (i) is almost the same as the relationship curve provided by FIG24 (ii). It can be seen that the lithium-ion battery provided in the embodiment of the present application has repeatability.

The present application also provides a method for preparing a lithium ion battery. Please refer to FIG. 25 and FIG. 26. FIG. 25 is a flow chart of the method for preparing a lithium ion battery, and FIG. 26 is a process flow chart of the method for preparing a lithium ion battery provided in FIG. 25. The method for preparing a lithium ion battery includes:

S251: adding an initiator to the film layer material to obtain a polymer precursor.

The membrane layer materials include: polyethylene oxide polymers, lithium salts, and sulfonamide compounds.

As a feasible implementation method, the molecular structure of the sulfonamide compound is an asymmetric structure. The present application embodiment also provides a preparation process of a sulfonamide compound with an asymmetric molecular structure, and the details can be referred to FIG. 27 .

The specific synthesis steps of sulfonamide compounds may include:

(1) Slowly add sulfamoyl chloride dropwise into a mixed solution of sulfamoyl chloride/triethylamine (Et ₃ N)/dichloromethane (DCM).

(2) Stirring the reaction at room temperature for 1 hour;

(3) washing with hydrochloric acid, sodium bicarbonate solution, and sodium chloride solution in sequence to remove unreacted raw materials and formed salts; wherein the raw materials include unreacted sulfamoyl chloride, ethylmethylamine, triethylamine, dichloromethane, etc. The salts may include sodium bicarbonate, sodium chloride, etc.

(3) drying the solvent to obtain a sulfonamide compound.

Sulfonamide compounds with asymmetric molecular structures are not easy to form close stacking between molecules, and sulfonamide compounds are not easy to form local structures of plasticized crystals. Plasticized crystals will reduce the plasticizing properties of sulfonamide compounds. Therefore, sulfonamide compounds have greater plasticizing properties.

In the embodiment of the present application, the initiator is a compound that decomposes into free radicals when heated, which can be used to initiate a cross-linking reaction of the polyethylene oxide polymer, so that the polyethylene oxide polymer forms a cross-linking system. The initiator can be, but is not limited to, azobisisobutyronitrile (AIBN).

The morphology of the polymer precursor can be referred to (I) in FIG26 , wherein the polymer precursor is in liquid state.

S252: Forming a lithium-ion battery using a positive electrode, a negative electrode and a polymer precursor.

The lithium-ion battery comprises: a positive electrode, a negative electrode, and a composite solid electrolyte disposed between the positive electrode and the negative electrode, wherein the composite solid electrolyte is formed by a membrane material. The membrane material comprises: a polyethylene oxide polymer, a lithium salt, a diaphragm material, and a sulfonamide compound.

The steps of forming a lithium-ion battery using a positive electrode, a negative electrode and a polymer precursor include: S11 to S12.

S11: treating a polymer precursor so that the polymer precursor forms a composite solid electrolyte.

The processing of the polymer precursor may be achieved by, but is not limited to, heat treatment or light irradiation.

During the heat treatment or light irradiation process, the initiator mixed in the film material will form free radicals. Under the action of the free radicals, the polyethylene oxide polymer in the polymer precursor undergoes a cross-linking reaction, and the polymer precursor forms a composite solid electrolyte. The morphology of the composite solid electrolyte can be seen in (II A) in Figure 26.

S12: Assemble the positive electrode, the negative electrode and the composite solid electrolyte to obtain a lithium-ion battery.

The formed lithium-ion battery can be seen in (3A) of Figure 26.

As a feasible implementation method, a positive electrode, a negative electrode and a polymer precursor are used to form a lithium-ion battery, and the implementation method may include S21 to S22.

S21: Assemble the positive electrode, negative electrode and polymer precursor.

Please refer to (2B) in FIG. 26 , where it can be seen that the positive electrode and the negative electrode are spaced apart, and a polymer precursor is injected between the positive electrode and the negative electrode.

The following is an explanation of the assembly process of the positive electrode, the negative electrode and the polymer precursor in conjunction with a specific example. Please refer to Figure 28 for a cross-sectional view of a lithium-ion battery. The polymer precursor can be injected between the positive electrode and the negative electrode of the lithium-ion battery.

Please refer to FIG. 29 which is a cross-sectional view of a battery cell, in which a polymer precursor may be injected between the positive electrode and the negative electrode of the battery cell.

S22: treating the polymer precursor so that the polymer precursor forms a composite solid electrolyte.

During the heat treatment or light irradiation, the initiator mixed in the polymer precursor will form free radicals. Under the action of the free radicals, the polyethylene oxide polymer in the polymer precursor undergoes a cross-linking reaction, and the polymer precursor is converted into a composite solid electrolyte. The formed lithium-ion battery can be seen in (3B) in Figure 26.

The lithium-ion battery prepared in the embodiment of the present application includes: a positive electrode, a negative electrode, and a composite solid electrolyte disposed between the positive electrode and the negative electrode. The composite solid electrolyte is formed by a polymer precursor, and the polymer precursor includes a film material and an initiator. The film material (including a diaphragm material) includes: a polyethylene oxide polymer, a lithium salt, a diaphragm material, and a sulfonamide compound.

The effects that can be brought about by the preparation method can refer to the effects brought about by any possible implementation method of the above-mentioned membrane material/membrane/lithium-ion battery.

The present application also provides a method for preparing a lithium-ion battery, please refer to Figures 30 and 31. Figure 30 is a flow chart of the method for preparing a lithium-ion battery, and Figure 31 is a process flow chart of the method provided in Figure 30. The method comprises:

S301: adding an initiator to the film layer material to obtain a polymer precursor.

The specific implementation process can be found in the above embodiments, which will not be described in detail here.

S302: Forming a lithium-ion battery using a positive electrode, a negative electrode, a solid electrolyte and a polymer precursor.

The process of forming a lithium-ion battery using a positive electrode, a negative electrode, a solid electrolyte and a polymer precursor may include S31 to S33:

S31: coating a polymer precursor on at least one surface of the solid electrolyte.

The morphology of the solid electrolyte coated with a polymer precursor can be seen in (a) of Figure 31.

S32: treating the polymer precursor so that the polymer precursor forms a protective layer.

The processing of the polymer precursor may be achieved by, but is not limited to, heat treatment or light irradiation.

During the heat treatment or light irradiation, the initiator generates free radicals. Under the action of the free radicals, the polyethylene oxide polymer undergoes a cross-linking reaction, so that the polyethylene oxide polymer forms a cross-linking system (solid state), and the film material forms a protective layer.

The morphology of the protective layer and the solid electrolyte can be referred to in (2A) of FIG31. (2A) of FIG31 is only an example of forming a protective layer on the surface of the solid electrolyte adjacent to the positive electrode and the surface adjacent to the negative electrode. In the process of actual application, the protective layer can be formed only on the surface of the solid electrolyte adjacent to the positive electrode, or only on the surface of the solid electrolyte adjacent to the negative electrode.

S33: Assemble a positive electrode, a negative electrode and a solid electrolyte having a protective layer on the surface to obtain a lithium-ion battery.

The formed lithium-ion battery can be seen in (3A) of Figure 31.

The process of forming a lithium-ion battery using a positive electrode, a negative electrode and a solid electrolyte coated with a polymer precursor may include S41 to S42:

S41: Assemble the positive electrode, negative electrode, polymer precursor and solid electrolyte.

Please refer to (2B) in FIG. 31 , where it can be seen that the positive electrode and the negative electrode are spaced apart, and a solid electrolyte is disposed between the positive electrode and the negative electrode. The solid electrolyte can electrically isolate the positive electrode from the negative electrode. A polymer precursor is added between the positive electrode and the solid electrolyte, and between the negative electrode and the solid electrolyte.

The following is an explanation of the assembly process of the positive electrode, the negative electrode and the composite precursor in conjunction with a specific example. Please refer to FIG32 for a cross-sectional view of a lithium-ion battery. A solid electrolyte may be provided between the positive electrode and the negative electrode of the lithium-ion battery, and a polymer precursor may be injected between the positive electrode and the solid electrolyte, and between the negative electrode and the solid electrolyte.

Please refer to Figure 33, which is a cross-sectional view of a battery cell. A solid electrolyte may be provided between the positive electrode and the negative electrode, and a polymer precursor may be injected between the positive electrode and the solid electrolyte, and between the negative electrode and the solid electrolyte.

S42: treating the polymer precursor so that the polymer precursor forms a protective layer.

During the heat treatment or light irradiation, the initiator generates free radicals. Under the action of the free radicals, the polyethylene oxide polymer undergoes a cross-linking reaction, so that the polyethylene oxide polymer forms a cross-linking system (solid state), and the film material forms a protective layer. The formed lithium-ion battery can be referred to (three B) in Figure 31.

The lithium-ion battery prepared in the embodiment of the present application includes: a positive electrode, a negative electrode, a solid electrolyte and at least one protective layer. The solid electrolyte is arranged between the positive electrode and the negative electrode, and the at least one protective layer is formed by a polymer precursor. The protective layer is arranged between the solid electrolyte and the positive electrode, and/or between the solid electrolyte and the negative electrode. The protective layer is formed by a polymer precursor, and the polymer precursor includes a film material and an initiator. The film material includes: polyethylene oxide polymers, lithium salts and sulfonamide compounds.

The effects that can be brought about by the preparation method can refer to the effects brought about by any possible implementation method of the above-mentioned membrane material/membrane/lithium-ion battery.

In the description of this specification, specific features, structures, materials or characteristics may be combined in an appropriate manner in any one or more embodiments or examples.

The above are only specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims (24)

1. A film material, which is used to form a film, characterized in that the film material comprises: Polyethylene glycol dimethacrylate; Sulfonamide compounds; Lithium salts. 2. The film material according to claim 1 is characterized in that it also includes: polyethylene glycol monomethyl ether methacrylate. 3 . The film material according to claim 2 , characterized in that the molar ratio of the polyethylene glycol dimethacrylate to the polyethylene glycol monomethyl ether methacrylate is 1:10 to 10:1. 4 . The membrane material according to claim 1 , wherein the molecular structure of the sulfonamide compound is an asymmetric structure. 5 . The membrane material according to claim 1 , wherein the substituent of the sulfonamide compound comprises any one of a methyl group, an ethyl group or an ether group. 6 . The membrane material according to claim 1 , wherein the lithium salt comprises lithium bis(trifluoromethyl)sulfonyl imide and lithium bis(trifluoromethyl)sulfonyl imide. 7 . The membrane material according to claim 6 , wherein the mass ratio of the lithium bis(fluorosulfonyl)imide to the lithium bis(trifluoromethyl)sulfonylimide is in the range of 1:2 to 2:1. 8. The film material according to any one of claims 1 to 7, characterized in that the mass fraction of the sulfonamide compound is 40% to 60%. 9 . The film material according to claim 2 , wherein the relative molecular mass of the polyethylene glycol dimethacrylate/the polyethylene glycol monomethyl ether methacrylate is between 300 and 600. 10 . The film material according to claim 2 , wherein the degree of polymerization of the polyethylene glycol dimethacrylate/polyethylene glycol monomethyl ether methacrylate is 4 to 12. 11. The membrane material according to any one of claims 2 to 10, characterized in that, in the membrane material, the molar ratio of ether bonds to lithium ions is 10 to 30, the ether bonds are provided by the polyethylene glycol dimethacrylate and the polyethylene glycol monomethyl ether methacrylate, and the lithium ions are provided by the lithium salt. 12 . The film material according to claim 1 , wherein the concentration of the lithium salt is less than or equal to 25%. 13 . The film material according to claim 1 , wherein the film material has fluidity. 14. The membrane material according to any one of claims 1 to 13, further comprising: a diaphragm material. 15. A film layer, characterized in that the film layer comprises the film layer material according to any one of claims 1 to 14 and an initiator, and the initiator is used to solidify the film layer material. The membrane layer according to claim 15 , characterized in that the membrane layer has self-supporting properties. 17. A lithium ion battery, characterized by comprising: a positive electrode and a negative electrode; A composite solid electrolyte, wherein the composite solid electrolyte is arranged between the positive electrode and the negative electrode, and the materials used in the composite solid electrolyte include: the film material and the initiator according to claim 14. 18. A lithium ion battery, characterized by comprising: a positive electrode and a negative electrode; A solid electrolyte, wherein the solid electrolyte is disposed between the positive electrode and the negative electrode; At least one protective layer, the protective layer is arranged between the solid electrolyte and the positive electrode, and/or between the solid electrolyte and the negative electrode, and the material used for the protective layer includes: the membrane material and initiator according to any one of claims 1 to 12. 19. A method for preparing a lithium ion battery, comprising: An initiator is added to the film layer material described in claim 14 to obtain a polymer precursor, and a positive electrode, a negative electrode and the polymer precursor are used to form a lithium ion battery; the lithium ion battery comprises: a positive electrode, a negative electrode, and a composite solid electrolyte arranged between the positive electrode and the negative electrode, and the composite solid electrolyte is formed by the film layer material. 20. The preparation method according to claim 19, characterized in that the step of using the positive electrode, the negative electrode and the polymer precursor to form a lithium ion battery comprises: Treating the polymer precursor so that the polymer precursor forms the composite solid electrolyte; The positive electrode, the negative electrode and the composite solid electrolyte are assembled to obtain the lithium-ion battery. 21. The preparation method according to claim 19, characterized in that the step of using the positive electrode, the negative electrode and the polymer precursor to form a lithium ion battery comprises: Assembling the positive electrode, the negative electrode and the polymer precursor; The polymer precursor is processed so that the polymer precursor forms the composite solid electrolyte. 22. A method for preparing a lithium ion battery, comprising: Adding an initiator to the film material according to any one of claims 1 to 13 to obtain a polymer precursor; A lithium-ion battery is formed by using a positive electrode, a negative electrode, a solid electrolyte and the polymer precursor. The lithium-ion battery includes: the positive electrode, the negative electrode, the solid electrolyte and at least one protective layer. The solid electrolyte is arranged between the positive electrode and the negative electrode. The at least one protective layer is formed by the film material. The protective layer is arranged between the solid electrolyte and the positive electrode, and/or between the solid electrolyte and the negative electrode. 23. The preparation method according to claim 22, characterized in that the step of forming a lithium-ion battery using a positive electrode, a negative electrode and a solid electrolyte coated with the polymer precursor comprises: coating a polymer precursor on the surface of the solid electrolyte; treating the polymer precursor so that the polymer precursor forms the protective layer; The positive electrode, the negative electrode and the solid electrolyte having the protective layer on the surface are assembled to obtain the lithium ion battery. 24. The preparation method according to claim 22, characterized in that the step of forming a lithium ion battery using a positive electrode, a negative electrode, a solid electrolyte and the polymer precursor comprises: Assembling a positive electrode, a negative electrode, a solid electrolyte and the polymer precursor; The polymer precursor is treated so that the polymer precursor forms the protective layer.