Solid electrolyte diaphragm, preparation method and lithium battery

Abstract

The invention discloses a solid electrolyte diaphragm, a preparation method and a lithium battery. The solid electrolyte diaphragm comprises a base membrane and an electrolyte layer arranged on at least one side of the base membrane, and the electrolyte layer at least covers part of the surface of the base membrane; the electrolyte layer includes a polymer I. A polyacrylonitrile structure in the polymer I endows the electrolyte polymer I with a lithium ion conduction function, and the contact between an electrolyte diaphragm and an electrode is improved; the imide structure endows the electrolyte diaphragm with relatively high mechanical strength, enhances the stability of the polymer I at high temperature, and improves the thermal stability of the electrolyte diaphragm; the inorganic electrolyte group is grafted on the main chain of the polymer I, so that the polymer I forms a three-dimensional network, the ionic conductivity and the ionic mobility of the solid electrolyte diaphragm can be improved, the inorganic electrolyte group can be dispersed more uniformly in an electrolyte layer, and meanwhile, the thermal stability and the strength of the solid electrolyte diaphragm are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solid-state lithium batteries, and particularly relates to a solid-state electrolyte diaphragm, a preparation method thereof and a lithium battery. BACKGROUND

[0002] At present, lithium ion batteries are widely used due to their high specific energy, high working voltage, long cycle life, low self-discharge rate and environmental friendliness. However, the traditional liquid lithium ion battery contains organic carbonate liquid electrolyte, which has poor thermal stability and is flammable. When the battery is misused and generates heat, there are potential safety hazards such as liquid leakage, fire and explosion. Compared with the traditional liquid lithium ion battery, the solid-state lithium battery has higher energy density and higher safety, and has become a research hotspot in the field of lithium batteries.

[0003] One of the key technologies in the solid-state lithium battery is the solid-state electrolyte diaphragm technology. The diaphragm directly affects the energy density, safety, rate performance and high and low temperature performance of the battery. However, due to the limitations of material properties, the solid-state electrolyte diaphragm cannot simultaneously meet the requirements of mechanical strength, high temperature resistance and electrical conductivity.

[0004] Therefore, how to develop a solid-state electrolyte diaphragm that simultaneously meets the requirements of high strength, excellent heat resistance and high ionic conductivity is a problem that needs to be solved in the industry at present. SUMMARY

[0005] The purpose of the present application is to provide a solid-state electrolyte diaphragm, a preparation method thereof and a lithium battery, which aims to solve the problem that the existing solid-state electrolyte diaphragm cannot simultaneously meet the requirements of mechanical strength and electrical conductivity.

[0006] The first embodiment of the present application provides a solid-state electrolyte diaphragm, which comprises a base film and an electrolyte layer arranged on at least one side of the base film, and the electrolyte layer covers at least part of the surface of the base film. The electrolyte layer comprises a polymer I, and the structural formula of the polymer I is shown as formula I:

[0007] Formula I; In the formula, R is an inorganic electrolyte group, m=5-50, and n=5-50.

[0008] In some embodiments, the inorganic electrolyte group comprises at least one of lithium lanthanum titanium oxide, lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide and aluminum titanium lithium phosphate.

[0009] In some embodiments, the mass percentage of the inorganic electrolyte group in the polymer I is 1-10%.

[0010] In some embodiments, the porosity of the base film is 50-70%, and the average pore size of the base film is 0.05-0.5 μm.

[0011] In some embodiments, the base film and the electrolyte layer satisfy: 8 μm≤H1+H2≤35 μm; wherein H1 is the thickness of the base film, and H2 is the thickness of the electrolyte layer.

[0012] In some embodiments, the thickness H1 of the base film satisfies: 5 μm≤H1≤30 μm.

[0013] In some embodiments, the thickness H2 of the electrolyte layer satisfies: 3 μm≤H2≤10 μm.

[0014] In some embodiments, the material of the base film is at least one of polyethylene, polypropylene, polyvinylidene fluoride, and non-woven fabric.

[0015] The second embodiment of the present application provides a preparation method of a solid-state electrolyte separator, which is used to prepare the solid-state electrolyte separator in any of the above embodiments, and comprises the following steps: adding maleic anhydride and acrylonitrile into a first organic solvent, mixing uniformly, adding a polymerization initiator, heating to perform a first reaction, and obtaining a polymer II; adding an inorganic electrolyte into a second organic solvent, adjusting the pH to alkaline, heating, adding a hydrolyzate of a coupling agent to perform a second reaction, and obtaining a modified inorganic electrolyte; mixing the polymer II and the modified inorganic electrolyte, performing a third reaction, and continuing the reaction after adding acetic anhydride and pyridine, to obtain a polymer I; coating the polymer I on the surface of a base film to obtain the solid-state electrolyte separator; wherein the structural formula of the polymer II is shown in formula II,

[0016] formula II; in which, m=5-50, and n=5-50.

[0017] In some embodiments, the mass ratio of the polymer II and the modified inorganic electrolyte is (90-99):(1-10).

[0018] In some embodiments, the reaction temperature of the first reaction is 40-70 °C, and the reaction time is 2-5 h.

[0019] In some embodiments, the reaction temperature of the second reaction is 70-100 °C, the reaction time is 4-10 h, and the initial pH value is 9-10.

[0020] In some embodiments, the reaction temperature of the third reaction is 15-30℃, and the reaction time is 15-25h.

[0021] In some embodiments, the reaction time of the reaction after adding acetic anhydride and pyridine is 10-20h.

[0022] The third embodiment of the present application provides a lithium battery comprising the solid electrolyte separator in any of the above embodiments, or the solid electrolyte separator prepared by the preparation method in any of the above embodiments. The mechanical strength of the solid electrolyte separator of the lithium battery is 7-25Mpa.

[0023] The present application provides a solid electrolyte separator, which comprises a base film and an electrolyte layer arranged on at least one side of the base film, the electrolyte layer covering at least part of the surface of the base film; the electrolyte layer comprises polymer I. The polyacrylonitrile structure in polymer I endows the electrolyte polymer I with the function of conducting lithium ions, and improves the contact between the electrolyte separator and the electrode; the imide structure endows the electrolyte separator with high mechanical strength, and enhances the stability of polymer I at high temperature, thereby improving the thermal stability of the electrolyte separator; the inorganic electrolyte group is grafted on the main chain of polymer I, so that polymer I forms a three-dimensional network, which not only improves the ionic conductivity and ion transference rate of the solid electrolyte separator, but also makes the inorganic electrolyte group more uniformly dispersed in the electrolyte layer, and at the same time improves the thermal stability and strength of the solid electrolyte separator. The synergistic effect of the three makes the solid electrolyte separator have ideal performance in ionic conductivity, ion transference rate, mechanical strength and thermal stability, etc. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0025] Figure 1 is a test result graph of the solid electrolyte separator provided by the examples and comparative examples of the present application. DETAILED DESCRIPTION

[0026] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0027] In the description of the present application, it is necessary to explain that the meaning of "a plurality of" is two or more than two, unless otherwise explicitly and specifically limited. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features limited by "first", "second" can be explicitly or implicitly included one or more features.

[0028] The compounds of the present application can be synthesized by synthetic routes including processes analogous to those well-known in the chemical arts, particularly in light of the description contained herein. The starting materials are generally available from commercial sources, or are readily prepared using methods well known to those skilled in the art. For the purpose of illustration, the reaction schemes depicted below show possible routes for synthesizing the compounds of the present application and key intermediates. For a more detailed description of the individual reaction steps, see the Example section below. Those skilled in the art will appreciate that other suitable starting materials, reagents and synthetic routes can be used to synthesize the compounds of the present application and various derivatives thereof.

[0029] The following disclosure provides many different embodiments, or examples, for implementing different structures of the present application. For the purpose of simplifying the present application, the constitutions and arrangements of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application.

[0030] For solid-state lithium batteries, researchers have been committed to developing and developing solid-state electrolyte separators with high mechanical strength, good toughness, high ionic conductivity and flexibility to be suitable for solid-state lithium batteries. Then limited by the properties of the material, the performance of the solid-state electrolyte separator is often lacking. For example, oxides can be prepared into dense ceramic sheet separators, but the ceramic sheet is brittle and has low room temperature ionic conductivity, so the applicability is low; the room temperature ionic conductivity of sulfide is high, but it cannot be prepared into a dense film and has poor strength; although the polymer is easy to prepare into a film, the mechanical strength is low, it is easy to be pierced by lithium dendrites, and it cannot resist high temperature.

[0031] The applicant found through research that using a polymer with a special structure to form a solid-state electrolyte coating can prepare a solid-state electrolyte separator with good overall performance.

[0032] The first embodiment of the present application provides a solid-state electrolyte separator, comprising a base film and an electrolyte layer arranged on at least one side of the base film, the electrolyte layer covering at least part of the surface of the base film; The electrolyte layer comprises a polymer I, and the structural formula of the polymer I is shown as formula I:

[0033] Formula I; In the formula, R is an inorganic electrolyte group, m = 5~50, n = 5~50.

[0034] It is understandable that the polyacrylonitrile structure in polymer I endows the electrolyte polymer I with the function of conducting lithium ions and improves the contact between the electrolyte membrane and the electrode; the imide structure endows the electrolyte membrane with high mechanical strength and enhances the stability of polymer I at high temperatures, thereby improving the thermal stability of the electrolyte membrane; the inorganic electrolyte groups grafted onto the main chain of polymer I form a three-dimensional network, which not only improves the ionic conductivity and ion mobility of the solid electrolyte membrane, but also makes the inorganic electrolyte groups more uniformly dispersed in the electrolyte layer, while improving the thermal stability and strength of the solid electrolyte membrane. The synergistic effect of these three factors results in the solid electrolyte membrane exhibiting ideal performance in terms of ionic conductivity and ion mobility, mechanical strength, and thermal stability. The value of m can be any value or any range between any two of 5, 10, 15, 20, 25, 30, 35, 40, 45, and 50. The value of n can be any value or any range between any two of 5, 10, 15, 20, 25, 30, 35, 40, 45, and 50. When m and n satisfy the above value range, the polyacrylonitrile structure and imide structure / inorganic electrolyte group in polymer I have ideal densities, thereby achieving a balance in terms of conductivity, mechanical strength and thermal stability of the solid electrolyte membrane.

[0035] In some embodiments, the inorganic electrolyte group includes at least one of lithium lanthanum titanium oxide, lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, and lithium aluminum titanium phosphate.

[0036] It is understandable that the inherent crystal structure of the aforementioned inorganic electrolyte groups can provide dedicated pathways for lithium ion migration, resulting in higher room temperature ionic conductivity and chemical stability compared to other inorganic electrolytes. At the same time, the aforementioned inorganic electrolyte groups also have good compatibility with the main chain of polymer I. Through grafting, they can stably combine with the main chain of polymer I to form a three-dimensional network structure, avoiding the aggregation of inorganic phases and giving the electrolyte layer better mechanical strength and stability.

[0037] In some embodiments, the inorganic electrolyte groups in polymer I have a mass percentage of 1 to 10%.

[0038] It is understandable that the mass percentage of inorganic electrolyte groups in polymer I can be any value from 1%, 2%, 4%, 6%, 8%, 10%, or any value within a range of two. By controlling the mass percentage of inorganic electrolyte groups in polymer I to meet the above range, it can be ensured that the inorganic electrolyte groups are sufficient to form an effective lithium-ion conduction network in the electrolyte layer. At the same time, it avoids the possibility that excessively high proportions will cause the inorganic electrolyte groups to easily agglomerate, thereby destroying the three-dimensional network structure of polymer I, leading to decreased flexibility and increased brittleness of the solid electrolyte separator, and affecting battery assembly and cycle performance.

[0039] In some embodiments, the porosity of the base membrane is 50-70%, and the average pore size of the base membrane is 0.05-0.5 μm.

[0040] It is understandable that the porosity of the base membrane can be any value or a range between any two of 50%, 55%, 60%, 65%, and 70%, and the average pore size of the base membrane can be any value or a range between any two of 0.05μm, 0.1μm, 0.2μm, 0.3μm, 0.4μm, and 0.5μm. By providing a base membrane with high porosity and large pore size, the solid electrolyte in the electrolyte layer coated on the base membrane surface can penetrate into the pores of the base membrane. On the one hand, the solid electrolyte penetrating deep into the pores of the base membrane can form a continuous ion conduction network, reducing path interruptions in the lithium ion transport process. At the same time, the ordered structure of the base membrane pores can also guide the directional migration of lithium ions, avoiding the problem of disordered ion transport in conventional polymer electrolytes. On the other hand, when the porosity and average pore size of the base membrane meet the above-mentioned value range, the base membrane itself has a certain mechanical support. After the solid electrolyte penetrates into the pores of the base membrane, it not only retains the flexibility of the base membrane, but also enhances the mechanical strength of the base membrane, thereby improving the overall tear resistance and puncture resistance of the solid electrolyte separator, and thus reducing the risk of failure caused by lithium dendrites during battery operation.

[0041] In some embodiments, the base film and the electrolyte layer satisfy the following: 8μm≤H1+H2≤35μm; Where H1 is the thickness of the base film and H2 is the thickness of the electrolyte layer.

[0042] It is understandable that the value of H1+H2 can be any value from 8μm, 12μm, 18μm, 24μm, 30μm, 35μm, or any value within a range of any two values. H1+H2 represents the total thickness of the solid electrolyte membrane. By controlling the thickness of the base membrane and the electrolyte layer and satisfying the above value range, it can be ensured that the thickness of the base membrane is sufficient to provide reliable mechanical support and structural stability, and that the electrolyte layer can guarantee the high efficiency of lithium-ion conduction. At the same time, it ensures that the overall thickness of the solid electrolyte membrane is moderate, avoiding the problem of energy density reduction due to excessive membrane thickness.

[0043] In some embodiments, the thickness H1 of the base film satisfies: 5μm≤H1≤30μm.

[0044] It is understandable that the value of H1 can be any value from 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, or any value within a range of any two values. When the thickness H1 of the base film meets the above value range, it can further ensure that the thickness of the base film can provide reliable mechanical support and structural stability, while avoiding the problem of energy density reduction caused by excessive base film thickness.

[0045] In some embodiments, the thickness H2 of the electrolyte layer satisfies: 3μm≤H2≤10μm.

[0046] It is understandable that the value of H2 can be any value from 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, and 10μm, or any value within a range of any two values. When the thickness H2 of the electrolyte layer meets the above range, it can further ensure the high efficiency of lithium-ion conduction in the electrolyte layer, while avoiding the increase in interfacial impedance caused by an excessively thick electrolyte layer.

[0047] In some embodiments, the base film is made of at least one of polyethylene, polypropylene, polyvinylidene fluoride, and nonwoven fabric.

[0048] The second embodiment of this application provides a method for preparing a solid electrolyte membrane, used to prepare the solid electrolyte membrane in any of the above embodiments, comprising the following steps: Maleic anhydride and acrylonitrile were added to the first organic solvent, mixed evenly, and a polymerization initiator was added. The mixture was heated to carry out the first reaction to obtain polymer II. The inorganic electrolyte is added to a second organic solvent, the pH is adjusted to alkaline, the temperature is raised, and the hydrolysate of the coupling agent is added to carry out a second reaction to obtain the modified inorganic electrolyte. Polymer II was mixed with a modified inorganic electrolyte and subjected to a third reaction. Acetic anhydride and pyridine were added and the reaction continued to obtain polymer I. Polymer I was coated onto the surface of the base membrane to obtain a solid electrolyte membrane; The structural formula of polymer II is shown in Formula II.

[0049] Formula II; In the formula, m = 5~50, n = 5~50.

[0050] Understandably, this application prepares polymer II via the polymerization of maleic anhydride and acrylonitrile. The reaction conditions are mild and easily controlled, stably generating a polymer precursor with a specific structure. Subsequently, the inorganic electrolyte is modified with a coupling agent, ensuring stable grafting of the inorganic electrolyte onto the polymer backbone and solving the problem of uneven dispersion of the inorganic phase. Then, acetic anhydride and pyridine promote the imidization reaction, improving the mechanical strength and thermal stability of polymer I. The entire preparation process is mild, requires no complex equipment, and is conducive to industrial production.

[0051] In some embodiments, the mass ratio of polymer II to modified inorganic electrolyte is (90~99):(1~10).

[0052] It is understandable that when the mass ratio of polymer II to modified inorganic electrolyte meets the above range, it can ensure that the modified inorganic electrolyte is fully grafted, while avoiding excessive density of inorganic electrolyte groups in polymer I, which would lead to poor structural stability of polymer I.

[0053] In some embodiments, the reaction temperature of the first reaction is 40~70°C, and the reaction time is 2~5h.

[0054] It is understood that the reaction temperature of the first reaction can be any value or a range between any two of 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, and 70℃, and the reaction time of the first reaction can be any value or a range between any two of 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, and 5h. By controlling the reaction temperature and reaction time of the first reaction to meet the above ranges, it can be ensured that maleic anhydride and acrylonitrile are fully polymerized to produce polymer II with uniform molecular weight.

[0055] In some embodiments, the reaction temperature of the second reaction is 70~100℃, the reaction time is 4~10h, and the initial pH value is 9~10.

[0056] It is understood that the reaction temperature of the second reaction can be any value or a range between any two of 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, and 100℃, and the reaction time of the second reaction can be any value or a range between any two of 4h, 5h, 6h, 7h, 8h, 9h, and 10h. By controlling the reaction temperature, reaction time, and initial pH value of the second reaction to meet the above-mentioned ranges, an optimal reaction environment can be provided for the modification of inorganic electrolytes, ensuring that the reaction proceeds fully.

[0057] In some embodiments, the reaction temperature of the third reaction is 15~30°C, and the reaction time is 15~25h.

[0058] It is understandable that the reaction temperature of the third reaction can be any value or a range between any two of 15℃, 18℃, 21℃, 24℃, 27℃, and 30℃, and the reaction time of the third reaction can be any value or a range between any two of 15h, 17h, 19h, 21h, 23h, and 25h.

[0059] In some embodiments, the reaction time after the addition of acetic anhydride and pyridine is 10-20 h.

[0060] It is understandable that the reaction time following the addition of acetic anhydride and pyridine can be any value from 10h, 12h, 14h, 16h, 18h, and 20h, or any value within a range of two of these values. By controlling the reaction temperature and reaction time of the third and subsequent reactions to meet the above range, sufficient imidization can be ensured, thereby improving the mechanical strength and thermal stability of polymer I.

[0061] In some embodiments, the first organic solvent is N,N-dimethylpyrrolidone, the second organic solvent is N,N-dimethylpyrrolidone, the coupling agent is γ-aminopropyltriethoxysilane (KH550), and the polymerization initiator is azobisisobutyronitrile.

[0062] In some embodiments, the hydrolysate of the coupling agent can be obtained by hydrolysate preparation methods commonly used in the art. Taking KH550 as an example, the preparation method of its hydrolysate can be: Slowly add KH550 dropwise into the ethanol / isopropanol-water system and stir for 10-30 minutes. Prepare and use immediately.

[0063] Specifically, the method for preparing the solid electrolyte membrane provided in this application can be achieved through the following steps: S1. Maleic anhydride and acrylonitrile are added to a reaction vessel containing N,N-dimethylpyrrolidone and mixed evenly. Azobisisobutyronitrile is then added, and the temperature is raised to 40~70℃. The reaction is carried out for 2~5 hours to obtain polymer II. S2. Add the inorganic electrolyte to N,N-dimethylpyrrolidone solvent, stir and disperse, adjust the pH to 9-10, raise the temperature to 70-100℃, add the prepared KH550 hydrolysate dropwise, react for 4-10 hours, wash and dry to obtain the amino-modified inorganic electrolyte.

[0064] S3. Mix polymer II and modified inorganic electrolyte, stir at 15~30℃ for 15~25h, then add acetic anhydride and pyridine for imidization, continue stirring for 10~20h, finally wash several times with ethanol, and filter to obtain polymer I. S4. Add polymer I to N,N-dimethylpyrrolidone solvent, stir for 1-3 hours, then coat it onto the surface of the base membrane and dry it to obtain a solid electrolyte membrane.

[0065] The third embodiment of this application provides a lithium battery, including the solid electrolyte separator in any of the above embodiments, or including the solid electrolyte separator prepared by the preparation method in any of the above embodiments; The mechanical strength of the solid electrolyte separator in lithium batteries is 7~25 MPa.

[0066] The following description, in conjunction with specific embodiments, illustrates a solid electrolyte separator, its preparation method, and a lithium battery provided in this application: Example 1: S1. Add 9.8g of maleic anhydride and 5.3g of acrylonitrile to a reaction vessel containing N,N-dimethylpyrrolidone, mix well, add 0.02g of azobisisobutyronitrile, and heat to 60℃. React for 3h to obtain polymer II. S2. Lithium lanthanum zirconium tantalum oxide was added to N,N-dimethylpyrrolidone solvent, stirred and dispersed, pH was adjusted to 9.5, temperature was raised to 85℃, and the prepared hydrolysate of KH550 was added dropwise. The reaction was carried out for 7 hours, washed and dried to obtain amino-modified lithium lanthanum zirconium tantalum oxide.

[0067] S3. Add 0.3g of modified lithium lanthanum zirconium tantalum oxide to polymer II prepared in S1, stir at 15°C for 20h, then add 0.05g of acetic anhydride and 0.05g of pyridine for chemical imidization, continue stirring for 15h, finally wash three times with ethanol, filter, and obtain polymer I. The polymer structure is shown in Formula I-1:

[0068] Formula I-1.

[0069] S4. Add polymer I to N,N-dimethylpyrrolidone solvent, stir for 2 hours, and then coat it onto the surface of a 7μm polyethylene base membrane. The base membrane has a porosity of 60% and an average pore size of 0.2μm. After drying, a 10μm solid electrolyte membrane is obtained.

[0070] Example 2: S1. Add 9.8g of maleic anhydride and 5.3g of acrylonitrile to a reaction vessel containing N,N-dimethylpyrrolidone, mix well, add 0.02g of azobisisobutyronitrile, and heat to 60℃. React for 3h to obtain polymer II. S2. Lithium lanthanum zirconium tantalum oxide was added to N,N-dimethylpyrrolidone solvent, stirred and dispersed, pH was adjusted to 9.5, temperature was raised to 85℃, and the prepared hydrolysate of KH550 was added dropwise. The reaction was carried out for 7 hours, washed and dried to obtain amino-modified lithium lanthanum zirconium tantalum oxide.

[0071] S3. Add 0.9g of modified lithium lanthanum zirconium tantalum oxide to polymer II prepared in S1, stir at 15°C for 20h, then add 0.05g of acetic anhydride and 0.05g of pyridine for chemical imidization, continue stirring for 15h, finally wash three times with ethanol, filter, and obtain polymer I.

[0072] S4. Add polymer I to N,N-dimethylpyrrolidone solvent, stir for 2 hours, and then coat it onto the surface of a 7μm polyethylene base membrane. The base membrane has a porosity of 60% and a pore size of 0.2μm. After drying, a 10μm solid electrolyte membrane is obtained.

[0073] Example 3: S1. Add 9.8g of maleic anhydride and 5.3g of acrylonitrile to a reaction vessel containing N,N-dimethylpyrrolidone, mix well, add 0.02g of azobisisobutyronitrile, and heat to 60℃. React for 3h to obtain polymer II. S2. Lithium lanthanum zirconium tantalum oxide was added to N,N-dimethylpyrrolidone solvent, stirred and dispersed, pH was adjusted to 9.5, temperature was raised to 85℃, and the prepared hydrolysate of KH550 was added dropwise. The reaction was carried out for 7 hours, washed and dried to obtain amino-modified lithium lanthanum zirconium tantalum oxide.

[0074] S3. Add 1.5g of modified lithium lanthanum zirconium tantalum oxide to polymer II prepared in S1, stir at 15°C for 20h, then add 0.05g of acetic anhydride and 0.05g of pyridine for chemical imidization, continue stirring for 15h, finally wash three times with ethanol, filter, and obtain polymer I.

[0075] S4. Add polymer I to N,N-dimethylpyrrolidone solvent, stir for 2 hours, and then coat it onto the surface of a 7μm polyethylene base membrane. The base membrane has a porosity of 60% and an average pore size of 0.2μm. After drying, a 10μm solid electrolyte membrane is obtained.

[0076] Example 4: S1. Add 9.8g of maleic anhydride and 5.3g of acrylonitrile to a reaction vessel containing N,N-dimethylpyrrolidone, mix well, add 0.02g of azobisisobutyronitrile, and heat to 60℃. React for 3h to obtain polymer II. S2. Lithium lanthanum zirconium tantalum oxide was added to N,N-dimethylpyrrolidone solvent, stirred and dispersed, pH was adjusted to 9.5, temperature was raised to 85℃, and the prepared hydrolysate of KH550 was added dropwise. The reaction was carried out for 7 hours, washed and dried to obtain amino-modified lithium lanthanum zirconium tantalum oxide.

[0077] S3. Add 0.9g of modified lithium lanthanum zirconium tantalum oxide to polymer II prepared in S1, stir at 15°C for 20h, then add 0.05g of acetic anhydride and 0.05g of pyridine for chemical imidization, continue stirring for 15h, finally wash three times with ethanol, filter, and obtain polymer I.

[0078] S4. Add polymer I to N,N-dimethylpyrrolidone solvent, stir for 2 hours, and then coat it onto the surface of a 7μm polyethylene base membrane. The base membrane has a porosity of 55% and an average pore size of 0.2μm. After drying, a 10μm solid electrolyte membrane is obtained.

[0079] Example 5: S1. Add 9.8g of maleic anhydride and 5.3g of acrylonitrile to a reaction vessel containing N,N-dimethylpyrrolidone, mix well, add 0.02g of azobisisobutyronitrile, and heat to 60℃. React for 3h to obtain polymer I. S2. Lithium lanthanum zirconium tantalum oxide was added to N,N-dimethylpyrrolidone solvent, stirred and dispersed, pH was adjusted to 9.5, temperature was raised to 85℃, and the prepared hydrolysate of KH550 was added dropwise. The reaction was carried out for 7 hours, washed and dried to obtain amino-modified lithium lanthanum zirconium tantalum oxide.

[0080] S3. Add 0.9g of modified lithium lanthanum zirconium tantalum oxide to polymer II prepared in S1, stir at 15°C for 20h, then add 0.05g of acetic anhydride and 0.05g of pyridine for chemical imidization, continue stirring for 15h, finally wash three times with ethanol, filter, and obtain polymer I.

[0081] S4. Add polymer I to N,N-dimethylpyrrolidone solvent, stir for 2 hours, and then coat it onto the surface of a 7μm polyethylene base membrane. The base membrane has a porosity of 65% and an average pore size of 0.2μm. After drying, a 10μm solid electrolyte membrane is obtained.

[0082] Example 6: S1. Add 9.8g of maleic anhydride and 5.3g of acrylonitrile to a reaction vessel containing N,N-dimethylpyrrolidone, mix well, add 0.02g of azobisisobutyronitrile, and heat to 60℃. React for 3h to obtain polymer II. S2. Add lithium aluminum titanium phosphate to N,N-dimethylpyrrolidone solvent, stir and disperse, adjust pH to 9.5, raise temperature to 85℃, add the prepared KH550 hydrolysate dropwise, react for 7h, wash and dry to obtain amino-modified lithium lanthanum zirconium tantalum oxide.

[0083] S3. Add 0.9g of modified lithium lanthanum zirconium tantalum oxide to polymer II prepared in S1, stir at 15°C for 20h, then add 0.05g of acetic anhydride and 0.05g of pyridine for chemical imidization, continue stirring for 15h, finally wash three times with ethanol, filter, and obtain polymer I.

[0084] S4. Add polymer I to N,N-dimethylpyrrolidone solvent, stir for 2 hours, and then coat it onto the surface of a 7μm polyethylene base membrane. The base membrane has a porosity of 60% and a pore size of 0.2μm. Dry the membrane to obtain a 10μm solid electrolyte membrane.

[0085] Comparative Example 1: Comparative Example 1 is a commercially available ceramic diaphragm with a diameter of 10 μm.

[0086] The solid electrolyte membranes prepared in the above embodiments and comparative examples were subjected to performance testing, including the following steps: Mechanical strength test method: Refer to GB / T36363-2018 standard, and test the mechanical strength of the composite solid electrolyte diaphragm at a rate of 10 mm / min under universal tensile test.

[0087] Ionic conductivity test: The ionic conductivity of the electrolyte is calculated by assembling a symmetrical cell with a steel sheet as the blocking electrode on an electrochemical workstation at a frequency range of 0.1 Hz to 106 Hz, according to the following working time: σ = L / (R×S), where σ is the ionic conductivity of the composite solid electrolyte membrane, L is the thickness of the composite solid electrolyte membrane, S is the area of ​​the composite solid electrolyte membrane, and R is the bulk resistance of the composite solid electrolyte membrane.

[0088] The results obtained are as follows Figure 1 As shown.

[0089] according to Figure 1 As can be seen, the solid electrolyte membrane obtained by adopting the solution provided in this application has good performance in both mechanical strength and ionic conductivity. Compared with ceramic membrane, the solid electrolyte membrane in the embodiments of this application has a significant improvement in overall performance.

[0090] The foregoing has provided a detailed description of a solid electrolyte separator and its preparation method, as well as a lithium battery, provided in the embodiments of this application. Specific examples have been used in this application to illustrate the principles and implementation methods of this application. The descriptions of the above embodiments are only for the purpose of helping to understand the technical solutions and core ideas of this application. Those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A solid electrolyte membrane, characterized in that, It includes a base membrane and an electrolyte layer disposed on at least one side of the base membrane, the electrolyte layer at least covering a portion of the surface of the base membrane; The electrolyte layer comprises polymer I, and the structural formula of polymer I is shown in Formula I: Formula I; In the formula, R is an inorganic electrolyte group, m = 5~50, n = 5~50.

2. The solid electrolyte membrane according to claim 1, characterized in that, The inorganic electrolyte group includes at least one of lithium lanthanum titanium oxide, lithium lanthanum zirconium oxide, lithium lanthanum zirconium tantalum oxide, and lithium aluminum titanium phosphate.

3. The solid electrolyte membrane according to claim 1, characterized in that, The inorganic electrolyte groups in polymer I have a mass percentage of 1 to 10%.

4. The solid electrolyte membrane according to claim 1, characterized in that, The porosity of the base membrane is 50-70%, and the average pore size of the base membrane is 0.05-0.5 μm.

5. The solid electrolyte membrane according to claim 1, characterized in that, The base membrane and the electrolyte layer satisfy the following: 8μm≤H1+H2≤35μm; Wherein, H1 is the thickness of the base film, and H2 is the thickness of the electrolyte layer.

6. The solid electrolyte membrane according to claim 5, characterized in that, The thickness H1 of the base film satisfies: 5μm ≤ H1 ≤ 30μm; and / or, The thickness H2 of the electrolyte layer satisfies: 3μm≤H2≤10μm.

7. The solid electrolyte membrane according to claim 1, characterized in that, The base film is made of at least one of polyethylene, polypropylene, polyvinylidene fluoride, and nonwoven fabric.

8. A method for preparing a solid electrolyte membrane as described in any one of claims 1 to 7, characterized in that, Includes the following steps: Maleic anhydride and acrylonitrile were added to the first organic solvent, mixed evenly, and a polymerization initiator was added. The mixture was heated to carry out the first reaction to obtain polymer II. The inorganic electrolyte is added to a second organic solvent, the pH is adjusted to alkaline, the temperature is raised, and the hydrolysate of the coupling agent is added to carry out a second reaction to obtain the modified inorganic electrolyte. The polymer II and the modified inorganic electrolyte were mixed and subjected to a third reaction. Acetic anhydride and pyridine were added and the reaction was continued to obtain polymer I. The polymer I is coated onto the surface of the base membrane to obtain the solid electrolyte membrane; The structural formula of polymer II is shown in Formula II. Formula II; In the formula, m = 5~50, n = 5~50.

9. The method for preparing a solid electrolyte membrane according to claim 8, characterized in that, The mass ratio of the polymer II to the modified inorganic electrolyte is (90~99):(1~10); and / or, The first reaction is carried out at a temperature of 40-70°C for a time of 2-5 hours; and / or, The second reaction is carried out at a temperature of 70-100°C for 4-10 hours, with an initial pH of 9-10; and / or, The third reaction is carried out at a temperature of 15-30°C for a time of 15-25 hours; and / or, The reaction time after adding acetic anhydride and pyridine is 10-20 h.

10. A lithium battery, characterized in that, Includes a solid electrolyte membrane as described in any one of claims 1 to 7, or includes a solid electrolyte membrane prepared by the preparation method as described in any one of claims 8 to 9; The solid electrolyte separator of the lithium battery has a mechanical strength of 7~25 MPa.

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