Solid-state electrolyte material and preparation method thereof, positive electrode sheet, solid-state electrolyte membrane, and all-solid-state battery

Abstract

The application discloses a kind of solid electrolyte material and its preparation method, positive pole piece, solid electrolyte film and full solid battery, it is related to solid battery field;Method comprises: lithium lanthanum zirconium oxygen base solid electrolyte is dispersed in first solvent, and electrolyte dispersion liquid is made;Acidic pH regulator is added to the electrolyte dispersion liquid, and the pH of the electrolyte dispersion liquid is adjusted to 7~8, and neutral dispersion liquid is obtained;Orthosilicate is added to the neutral dispersion liquid and mixed to obtain dispersion solution;During mixing process, polysiloxane is formed by the reaction of orthosilicate, and polysiloxane is coated on the surface of lithium lanthanum zirconium oxygen base solid electrolyte;The dispersion solution is subjected to electrolyte separation and drying treatment to obtain a solid electrolyte material.The application aims to improve the surface properties of lithium lanthanum zirconium oxygen base solid electrolyte, so that it can build good interface contact with other inorganic materials.

Description

Technical Field

[0001] This application relates to the field of solid-state batteries, and more particularly to a solid electrolyte material and its preparation method, a positive electrode, a solid electrolyte membrane, and an all-solid-state battery. Background Technology

[0002] Lithium-ion batteries are rechargeable batteries that primarily function by the reciprocating movement of lithium ions between the positive and negative electrodes. Traditional lithium-ion batteries use liquid organic electrolytes as the electrolyte material. However, liquid organic electrolytes have drawbacks such as flammability and poor thermal stability, leading to safety hazards in the application of lithium batteries. In recent years, all-solid-state batteries based on solid-state electrolytes have demonstrated their potential to replace traditional liquid lithium-ion batteries and dominate the new energy market due to their advantages such as low self-discharge, high flexibility, high safety, and high energy density, and are expected to become the next generation of commercially viable energy storage devices.

[0003] The key component of solid-state batteries is the solid-state electrolyte, which includes organic and inorganic solid-state electrolytes. Among them, inorganic solid-state electrolytes have advantages such as stable chemical and electrochemical properties and high ionic conductivity at room temperature, making them one of the research hotspots in the field of solid-state electrolytes. Garnet-type lithium lanthanum zirconium oxide (LLZO-based) solid-state electrolytes have received widespread attention and research due to their high melting point, high mechanical strength, and stable contact with metallic lithium.

[0004] LLZO-based electrolytes possess inherent characteristics of high hardness and brittleness, making it difficult to establish good interfacial contact with cathode active materials and unable to adapt to the volume changes of cathode materials and metallic lithium during battery cycling. Furthermore, LLZO-based electrolytes readily react with CO2 and H2O in the air, forming byproducts such as Li2CO3 on the surface of LLZO particles. These impurities not only reduce the lithium affinity of LLZO-based electrolytes but also increase the interfacial impedance between the LLZO-based electrolyte and the electrode. These problems severely limit the practical application of LLZO-based electrolytes in the preparation of high-performance composite cathodes, inorganic electrolytes, and composite electrolyte membranes. Therefore, improving solid / solid interfacial contact and removing lithium carbonate from the surface of LLZO electrolyte powder has become a current research hotspot. Summary of the Invention

[0005] In view of this, this application provides a solid electrolyte material and its preparation method, a positive electrode sheet, a solid electrolyte membrane and an all-solid-state battery, aiming to improve the surface properties of lithium lanthanum zirconium oxy-based solid electrolyte so that it can form good interfacial contact with other inorganic materials.

[0006] The embodiments of this application are implemented as follows:

[0007] In a first aspect, this application provides a method for preparing a solid electrolyte material, comprising the following steps:

[0008] A lithium lanthanum zirconium oxy-based solid electrolyte is dispersed in a first solvent to prepare an electrolyte dispersion.

[0009] An acidic pH adjuster is added to the electrolyte dispersion to adjust the pH of the electrolyte dispersion to 7-8, thereby obtaining a neutral dispersion.

[0010] Orthosilicate is added to the neutral dispersion and mixed to obtain a dispersion solution; during the mixing process, the orthosilicate reacts to form polysiloxane, which coats the surface of the lithium lanthanum zirconium oxide solid electrolyte.

[0011] The dispersion solution is subjected to electrolyte separation and drying treatment to obtain a solid electrolyte material.

[0012] Optionally, in some embodiments of this application, the orthosilicate includes one or more of ethyl orthosilicate, butyl orthosilicate, methyl orthosilicate, and isopropyl orthosilicate; and / or,

[0013] The chemical formula of the lithium lanthanum zirconium oxide solid electrolyte is Li 5+x La3Zr x M 2-x O 12 M is selected from any one of Ta, Nb, Hf, Al, Si, Ga, Sc, Ti, V, Y and Sn, and x is 0 to 0.6.

[0014] Optionally, in some embodiments of this application, in the step of dispersing the lithium lanthanum zirconium oxy-based solid electrolyte in a first solvent to prepare an electrolyte dispersion:

[0015] The first solvent comprises one or more of alcohols, alkanes having 3 to 8 carbon atoms, and aromatic hydrocarbons having 6 to 10 carbon atoms; the alcohols include one or more of methanol, ethanol, ethylene glycol, and isopropanol; the alkanes having 3 to 8 carbon atoms include n-hexane; and the aromatic hydrocarbons having 6 to 10 carbon atoms include toluene; and / or,

[0016] The lithium lanthanum zirconium oxy-based solid electrolyte is dispersed in the first solvent by ultrasound, wherein the frequency of the ultrasound is 1–50 kHz and the duration of the ultrasound is 0.05–3 h; and / or,

[0017] The concentration of the electrolyte dispersion is 0.1–2 g / ml; and / or,

[0018] The drying process employs an oven-drying method, with a drying temperature of 10–100°C and a drying time of 1–72 hours; and / or,

[0019] In the step of adding orthosilicate to the neutral dispersion and mixing to obtain a dispersion solution, the mixing is performed by ultrasound, the frequency of which is 1 to 100 kHz and the duration of which is 1 to 300 min.

[0020] Optionally, in some embodiments of this application, the weight ratio of lithium lanthanum zirconium oxysolid electrolyte to orthosilicate in the neutral dispersion is (50–99.9):(50–0.1); and / or,

[0021] Before adding the acidic pH adjuster to the electrolyte dispersion, the method further includes: adding an acidic substance to a second solvent to dissolve and obtain the acidic pH adjuster, wherein the acidic substance includes an organic acid, and the second solvent includes one or more of alcohols, alkanes with 3 to 8 carbon atoms, and aromatic hydrocarbons with 6 to 10 carbon atoms, wherein the alcohols include one or more of methanol, ethanol, ethylene glycol, and isopropanol, the alkanes with 3 to 8 carbon atoms include n-hexane, and the aromatic hydrocarbons with 6 to 10 carbon atoms include toluene.

[0022] Optionally, in some embodiments of this application, the organic acid includes one or more of formic acid, acetic acid, and oxalic acid; and / or,

[0023] The concentration of the acidic substance in the acidic pH adjuster is 0.5–3 mol / L; and / or,

[0024] After the acidic substance is added to the second solvent, it is subjected to ultrasonic treatment to dissolve the acidic substance. The frequency of the ultrasonic treatment is 30-50 kHz, and the duration of the ultrasonic treatment is 5-20 min.

[0025] Secondly, this application also proposes a solid electrolyte material, which is prepared by the above-described preparation method. The solid electrolyte material includes a lithium lanthanum zirconium oxy solid electrolyte and a modification layer covering the lithium lanthanum zirconium oxy solid electrolyte. The material of the modification layer includes polysiloxane.

[0026] Optionally, in some embodiments of this application, the weight percentage of the lithium lanthanum zirconium oxide solid electrolyte in the solid electrolyte material is 50.1% to 99.9%; and / or,

[0027] The chemical formula of the lithium lanthanum zirconium oxide solid electrolyte is Li 5+x La3Zr x M 2-x O 12 Wherein, M is selected from any one of Ta, Nb, Hf, Al, Si, Ga, Sc, Ti, V, Y, and Sn, and x is 0 to 0.6; and / or,

[0028] The solid electrolyte material is a powder, and the average particle size of the solid electrolyte material is 50-900 nm.

[0029] Thirdly, this application also proposes a positive electrode sheet comprising a solid electrolyte material, wherein the solid electrolyte material includes the solid electrolyte material described above, or the solid electrolyte material is prepared by the preparation method described above.

[0030] Fourthly, this application also proposes a solid electrolyte membrane, comprising a solid electrolyte material, wherein the solid electrolyte material includes the solid electrolyte material described above, or the solid electrolyte material is prepared by the preparation method described above.

[0031] Fifthly, this application also proposes an all-solid-state battery, including a positive electrode, an electrolyte membrane, and a negative electrode, wherein the positive electrode includes the positive electrode described above, and / or the electrolyte membrane includes the solid electrolyte membrane described above.

[0032] The preparation method provided in this application has advantages such as readily available raw materials, short preparation time, simple operation, and ease of large-scale production. This method can prepare lithium lanthanum zirconium oxide solid electrolyte material with at least partial surface coating of orthosilicate. By at least partially coating the lithium lanthanum zirconium oxide solid electrolyte with a polysiloxane modification layer, the surface of LLZO is modified. On the one hand, its environmental stability is greatly improved, which can avoid its reaction with CO2 and H2O in the air to form byproducts such as Li2CO3, thus enabling large-scale stable transportation, storage, and use. On the other hand, the surface-modified LLZO has better dispersibility, which can significantly improve the agglomeration phenomenon during the preparation of composite materials such as positive electrode sheets and electrolyte membranes. At the same time, the presence of the modification layer improves its surface properties, enabling it to form good interfacial contact with other inorganic active materials. This allows the composite material to adapt to the electrode volume changes during battery cycling, resulting in all-solid-state batteries prepared using this composite material with lower interfacial impedance and better cycle stability. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 This is a TEM image of a solid electrolyte material proposed in an embodiment of this application;

[0035] Figure 2This is a schematic flowchart of a method for preparing a solid electrolyte material according to an embodiment of this application;

[0036] Figure 3 This is a SEM image of a positive electrode sheet proposed in an embodiment of this application;

[0037] Figure 4 This is a comparison diagram of the composite solid electrolyte slurry in the example and the comparative example in Experimental Example 1;

[0038] Figure 5 This is a comparison chart of the room temperature cycling performance of Example 1 and Comparative Example 1 in Experimental Example 2;

[0039] Figure 6 These are the room-temperature electrochemical charge-discharge curves of the all-solid-state battery in Example 1 of Experiment 2;

[0040] Reference numerals: 1-Lithium lanthanum zirconium oxide solid electrolyte; 2-Modification layer. Detailed Implementation

[0041] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. Furthermore, it should be understood that the specific embodiments described herein are only for illustration and explanation of this application and are not intended to limit this application.

[0042] In this application, unless otherwise stated, directional terms such as "upper" and "lower" specifically refer to the orientation shown in the accompanying drawings. Furthermore, in the description of this application, the term "comprising" means "including but not limited to".

[0043] Various embodiments of this application may exist in the form of a range; it should be understood that the description in the form of a range is merely for convenience and brevity and should not be construed as a hard limitation on the scope of this application; therefore, it should be considered that the range description has specifically disclosed all possible sub-ranges and single numerical values ​​within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and single numbers within the range, such as 1, 2, 3, 4, 5, and 6, regardless of the range. Furthermore, whenever a numerical range is referred to herein, it means including any referenced number (fraction or integer) within the referred range.

[0044] In this application, "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural.

[0045] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one," "at least one of the following," or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c," or "at least one of a, b, and c," can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0046] The technical solution of this application is implemented as follows:

[0047] In a first aspect, embodiments of this application provide a solid electrolyte material, the solid electrolyte material comprising a lithium lanthanum zirconium oxy-solid electrolyte 1 and a modification layer 2 covering the lithium lanthanum zirconium oxy-solid electrolyte 1, the modification layer 2 being made of orthosilicate.

[0048] Please see Figure 1 In some embodiments, the solid electrolyte material is observed using a transmission electron microscope (TEM), which has a core and a modification layer 2. The core is made of lithium lanthanum zirconium oxy-based solid electrolyte 1, and the modification layer 2 is made of polysiloxane. The modification layer 2 at least partially covers the core, that is, completely covers the outer surface of the core, or covers a portion of the outer surface of the core.

[0049] The technical solution provided in this application involves at least partially coating a polysiloxane modification layer onto the lithium lanthanum zirconium oxide (LLZO) solid electrolyte, thereby modifying the LLZO surface. On one hand, polysiloxane possesses excellent chemical stability; after coating, the environmental stability of LLZO is significantly improved, preventing it from reacting with CO2 and H2O in the air to form byproducts such as Li2CO3. This allows for large-scale stable transportation, storage, and use. On the other hand, the surface-modified LLZO exhibits better dispersibility, significantly reducing agglomeration during the preparation of composite materials such as positive electrode sheets and electrolyte membranes. Simultaneously, the presence of the modification layer improves its surface properties, enabling it to establish good interfacial contact with other inorganic active materials. This allows the composite material to adapt to electrode volume changes during battery cycling, resulting in all-solid-state batteries prepared using this composite material with lower interfacial impedance and better cycle stability. In summary, the solid electrolyte material proposed in this application is convenient for transportation, storage, and use; and the all-solid-state batteries prepared using it exhibit stable performance and high quality, contributing to the promotion of LLZO's application in the field of solid-state batteries.

[0050] In some embodiments, the weight percentage of the lithium lanthanum zirconium oxy-based solid electrolyte in the solid electrolyte material is 50.1% to 99.9%, for example, 50.1%, 51%, 55%, 60%, 70%, 80%, 90%, 95%, 96%, 97%, 98%, 99%, 99.5%, 99.9%, and any two of the above values. Within this range, it can be ensured that the solid electrolyte material has good ionic conductivity, and at the same time, it can be ensured that the material contains a certain amount of modification layer, so that the surface properties of the material are effectively improved.

[0051] In some embodiments, the lithium lanthanum zirconium oxy-oxide (LLZO) solid electrolyte can be an ionic conductor with a garnet structure and a chemical formula of Li. 5+x La3Zr x M 2-x O 12 Wherein, M is selected from any one of Ta, Nb, Hf, Al, Si, Ga, Sc, Ti, V, Y, and Sn, and x is 0 to 0.6, for example, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, and any value between any two of the above. LLZO exhibits excellent lithium stability and high ionic conductivity. It is understood that in some embodiments, x is 0, in which case the chemical formula of LLZO is Li5La3M2O. 12 .

[0052] In some embodiments, the solid electrolyte material is a powder, and the average particle size of the solid electrolyte material is 50-900 nm, for example, 50-150 nm, 110-180 nm, 170-220 nm, 220-260 nm, 250-290 nm, 280-320 nm, 310-350 nm, 350-400 nm, 400-450 nm, 450-500 nm, 490-620 nm, 620-650 nm, 650-730 nm, 730-770 nm, 750-860 nm, 860-900 nm, etc.

[0053] In some embodiments, the polysiloxane may be obtained from orthosilicate via hydrolysis and polycondensation reaction; the orthosilicate may be one or more of ethyl orthosilicate, butyl orthosilicate, methyl orthosilicate, and isopropyl orthosilicate.

[0054] Secondly, this application also proposes a method for preparing a solid electrolyte material, which can be used to obtain the solid electrolyte material described above. Please refer to [link to relevant documentation]. Figure 2 The preparation method includes the following steps:

[0055] S10, a lithium lanthanum zirconium oxy-based solid electrolyte is dispersed in a first solvent to prepare an electrolyte dispersion;

[0056] S20, add an acidic pH adjuster to the electrolyte dispersion to adjust the pH of the electrolyte dispersion to 7-8, and obtain a neutral dispersion;

[0057] S30, add orthosilicate to the neutral dispersion and mix to obtain a dispersion solution; during the mixing process, the orthosilicate undergoes hydrolysis and condensation to form polysiloxane, and the polysiloxane coats the surface of the lithium lanthanum zirconium oxide solid electrolyte.

[0058] S40, the dispersion solution is subjected to electrolyte separation and drying treatment to obtain a solid electrolyte material.

[0059] The preparation method proposed in this application has advantages such as readily available raw materials, short preparation time, simple operation, and ease of large-scale production. This method can prepare lithium lanthanum zirconium oxy-based solid electrolytes with at least partial surface coating of polysiloxane. The solid electrolyte material exhibits good environmental stability, allowing for large-scale stable transportation, storage, and use. Furthermore, it is not prone to agglomeration and can form good interfacial contact with other inorganic active materials, adapting to electrode volume changes during battery cycling. This results in all-solid-state batteries prepared using this composite material exhibiting lower interfacial impedance and better cycle stability.

[0060] In some embodiments, the orthosilicate may be one or more of ethyl orthosilicate, butyl orthosilicate, methyl orthosilicate, and isopropyl orthosilicate.

[0061] In some embodiments, the solid electrolyte material contains 50.1% to 99.9% by weight of the lithium lanthanum zirconium oxy-based solid electrolyte; the average particle size of the solid electrolyte material is 50 to 900 nm; and the chemical formula of the lithium lanthanum zirconium oxy-based solid electrolyte is Li. 5+x La3Zr x M 2-x O 12 M is selected from any one of Ta, Nb, Hf, Al, Si, Ga, Sc, Ti, V, Y and Sn, and x is 0 to 0.6.

[0062] In some embodiments, the lithium lanthanum zirconium oxy-based solid electrolyte can be purchased commercially or prepared by sol-gel method or solid-phase reaction method. For example, the preparation steps of the sol-gel method can be as follows: mixing lithium precursor, lanthanum precursor, zirconium precursor and precursor of dopant element M in a molar ratio of Li, La, Zr and M of (5+x):3:x:(2-x), then adding a solvent to dissolve, adding a chelating agent to form a sol-gel; heating the sol-gel to form a powder, and then grinding and sintering it to obtain the lithium lanthanum zirconium oxy-based solid electrolyte.

[0063] In step S10:

[0064] In some embodiments, the first solvent includes, but is not limited to, one or more of alcohols, alkanes having 3 to 8 carbon atoms, and aromatic hydrocarbons having 6 to 10 carbon atoms. These solvents can not only disperse LLZO well, but are also safe and non-toxic. Further, the alcohols are preferably one or more of methanol, ethanol, and ethylene glycol, the alkanes having 3 to 8 carbon atoms are preferably n-hexane, and the aromatic hydrocarbons having 6 to 10 carbon atoms are preferably toluene.

[0065] In step S10, various methods such as stirring, ultrasonication, vortexing, ball milling, and sand milling can be used to disperse the lithium lanthanum zirconium oxy-based solid electrolyte. The specific method can be selected according to actual needs and site conditions. In some embodiments, ultrasonication is used to disperse the lithium lanthanum zirconium oxy-based solid electrolyte in the first solvent. That is, step S10 can be implemented as follows: the lithium lanthanum zirconium oxy-based solid electrolyte and the first solvent are mixed, and ultrasonication is used to fully disperse the lithium lanthanum zirconium oxy-based solid electrolyte in the first solvent to prepare an electrolyte dispersion. The conditions for ultrasound can be as follows: the frequency of ultrasound is 1 to 50 kHz, for example, 1 kHz, 2 kHz, 5 kHz, 10 kHz, 15 kHz, 20 kHz, 25 kHz, 30 kHz, 35 kHz, 40 kHz, 45 kHz, 50 kHz, and any two of the above values; the duration of ultrasound is 0.05 to 3 h, for example, 0.05 h, 0.1 h, 0.5 h, 1 h, 1.5 h, 2 h, 2.5 h, 3 h, and any two of the above values; controlling ultrasound under the above conditions can promote the full dispersion of LLZO and obtain a uniform electrolyte dispersion, so that LLZO and orthosilicate can be in full contact in subsequent steps.

[0066] The amount of LLZO can be adjusted according to the amount of orthosilicate to control the percentage ratio of the two in the solid electrolyte material, thereby effectively regulating the balance between the electrical and surface properties of the material. In some embodiments, the feeding ratio of the two satisfies the following: the weight ratio of lithium lanthanum zirconium oxide solid electrolyte to orthosilicate in the neutral dispersion is (50-99.9):(50-0.1), for example: 50:50, 60:40, 70:30, 80:20, 85:15, 90:10, 95:5, 98:2, 98.5:1.5, 98.8:1.2, 99:1, 99.2:0.8, 99.5:0.5, 99.7:0.3, 99.9:0.1, etc.

[0067] In some embodiments, the concentration of the electrolyte dispersion is 0.1 to 2 g / ml, for example, 0.1 g / ml, 0.5 g / ml, 1 g / ml, 1.5 g / ml, 2 g / ml, and any two of the above values. Within this range, on the one hand, the electrolyte dispersion can have good stability and avoid agglomeration; on the other hand, it can ensure a sufficiently high concentration to help promote its reaction with orthosilicates.

[0068] In step S20, by adding an acidic pH adjuster, not only can the acidity and alkalinity of the system be adjusted to create a neutral environment and promote the coating of LLZO by orthosilicate, but also the impurities such as Li2CO3 that may be contained in LLZO can be reacted and removed during the pH adjustment process.

[0069] In some embodiments, prior to the step of adding an acidic pH adjuster to the electrolyte dispersion, the method further includes: adding an acidic substance to a second solvent to dissolve and obtain the acidic pH adjuster.

[0070] The acidic substance includes organic acids. In a preferred embodiment, the organic acid may include, but is not limited to, one or more of formic acid, acetic acid, and oxalic acid.

[0071] The second solvent includes one or more of alcohols, alkanes having 3 to 8 carbon atoms, and aromatic hydrocarbons having 6 to 10 carbon atoms; further, the alcohols are preferably one or more of methanol, ethanol, and ethylene glycol, the alkanes having 3 to 8 carbon atoms are preferably n-hexane, and the aromatic hydrocarbons having 6 to 10 carbon atoms are preferably toluene.

[0072] In some embodiments, the concentration of the acidic substance in the acidic pH adjuster is 0.5 to 3 mol / L, for example, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, and any value between any two of the above.

[0073] After the acidic substance is added to the second solvent, it can be dissolved using various methods such as stirring, ultrasound, and vortexing. The specific method can be selected based on actual needs and site conditions. In some embodiments, ultrasound is used for dissolution. The ultrasound conditions can be: the ultrasound frequency is 30–50 kHz, for example, 30 kHz, 35 kHz, 40 kHz, 45 kHz, 50 kHz, or any value between two of the above; the ultrasound duration is 5–20 min, for example, 5 min, 6 min, 8 min, 10 min, 13 min, 15 min, 18 min, 20 min, or any value between two of the above.

[0074] In some embodiments, during step S20, an acidic pH adjuster is added to the electrolyte dispersion to adjust the pH of the electrolyte dispersion to 7-8, resulting in a neutral dispersion. This process can be carried out under stirring conditions to ensure that the added acidic pH adjuster is promptly incorporated into the electrolyte dispersion, resulting in a uniform pH change throughout the dispersion. The stirring speed can be 200-5000 r / min, for example, 200 r / min, 300 r / min, 500 r / min, 1000 r / min, 2000 r / min, 3000 r / min, 4000 r / min, 5000 r / min, or any value between any two of these. Furthermore, to ensure the accuracy of pH adjustment, after adding the acidic pH adjuster and adjusting the pH to neutral, the pH of the electrolyte dispersion can be checked again after 0.05-3 hours to ensure that the electrolyte dispersion remains neutral.

[0075] In step S30, the mixing of the neutral dispersion and the orthosilicate can be achieved by various methods such as stirring, ultrasonication, or vortexing, and the specific method can be selected according to actual needs and site conditions. In some embodiments, ultrasonication is used for mixing. The frequency of the ultrasonication is 1–100 kHz, for example, 1 kHz, 2 kHz, 5 kHz, 10 kHz, 15 kHz, 20 kHz, 25 kHz, 30 kHz, 35 kHz, 40 kHz, 45 kHz, 50 kHz, 60 kHz, 70 kHz, 80 kHz, 90 kHz, 100 kHz, and any value between any two of the above; the duration of the ultrasonication is 1–300 min, for example, 1 min, 5 min, 6 min, 8 min, 10 min, 13 min, 15 min, 18 min, 20 min, 30 min, 50 min, 100 min, 150 min, 200 min, 250 min, 300 min, and any value between any two of the above.

[0076] In step S40, the electrolyte separation and drying process includes: firstly, performing solid-liquid separation on the dispersion solution to obtain a solid product, and then drying the solid product to remove residual solvent. The solid-liquid separation can be performed using methods such as filtration, vacuum filtration, or centrifugation; the drying can be performed using various methods such as hot air drying or vacuum drying. In some embodiments, the drying process employs an oven drying method. Specifically, the solid product can be placed in an oven for baking and drying. The drying temperature is 10–100°C, for example, 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, or any value between two of the above. The drying time is 1–72 hours, for example, 1 hour, 1.5 hours, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 10 hours, 15 hours, 20 hours, 22 hours, 24 hours, 23 hours, 25 hours, 26 hours, 28 hours, 30 hours, 40 hours, 50 hours, 60 hours, 70 hours, 72 hours, or any value between two of the above. Preferably, the drying temperature is 50–70°C, and the drying time is 18–30 hours. Within this range, residual solvent can be completely evaporated.

[0077] Thirdly, this application also proposes a positive electrode sheet comprising a solid electrolyte material, wherein the solid electrolyte material includes the solid electrolyte material described above, or the solid electrolyte material is prepared by the preparation method described above. Please refer to [link to relevant documentation]. Figure 3 Scanning the surface morphology of the positive electrode sheet reveals that the positive electrode sheet has good material uniformity, no obvious aggregation of electronic conductors, and small-sized coated inorganic electrolyte material is uniformly dispersed on the surface of large-sized active material or filling the pores between them.

[0078] The positive electrode sheet is made of the aforementioned solid electrolyte material, binder, positive electrode active material, conductive carbon, and other components. Specifically, it can be prepared using a ball mill or a slurry mixer. For example, in some embodiments, a ball mill is used to prepare the positive electrode sheet, and the specific operation steps are as follows:

[0079] (1) The solid electrolyte material prepared above is mixed with positive electrode active material, conductive carbon, binder and solvent (NMP) in a certain proportion and ball-milled to obtain composite positive electrode slurry.

[0080] The positive electrode active material is at least one of lithium cobalt oxide, lithium nickel manganese oxide, lithium manganese oxide, lithium iron phosphate, or lithium nickel cobalt manganese oxide, with a particle size D50 of 0.5 μm-50 μm; the conductive carbon includes super pll conductive carbon black and conductive graphite KS-6; the binder includes polyvinylidene fluoride (PVDF); and the solvent includes N-methylpyrrolidone (NMP). The mass ratio of the solid electrolyte material, positive electrode active material, super pll conductive carbon black, conductive graphite KS-6, PVDF, and NMP is (2-15):(81.5-95.2):(1-1.3):(0.5-0.7):(1.3-1.5):(20-800).

[0081] The ball milling conditions include a speed of 300–350 r / min and a time of 2–3 h.

[0082] (2) The composite positive electrode slurry is coated on the current collector, and then baked in an oven at 40-80℃ for 2-3 hours to pre-dry it. Then it is transferred to a vacuum oven for further drying to finally obtain the positive electrode sheet.

[0083] The vacuum drying conditions include: vacuum degree ≤133 Pa, temperature 60~200℃, and time 0.5-72h. The current collector is aluminum foil, carbon-coated aluminum foil, or carbon foil, etc.

[0084] In other embodiments, a slurry mixer is used to prepare the positive electrode sheet, and the specific operation steps are as follows:

[0085] (1) Place the solid electrolyte material, positive electrode active material and binder in a positive electrode mixing tank and stir at low speed to premix to obtain the first premix.

[0086] The stirring conditions include: stirring speed of 5-20 rpm and stirring time of 5-10 min.

[0087] (2) Add conductive carbon to the first premix obtained in step (1) and stir at low speed to premix to obtain the second premix.

[0088] The stirring conditions include: stirring speed of 5-20 rpm and stirring time of 10-20 min.

[0089] (3) Add solvent to the second premix obtained in step (2), stir and knead to obtain slurry.

[0090] The stirring conditions include: a stirring speed of 1500–2000 rpm and a stirring time of 30–60 min.

[0091] (4) Add solvent to the slurry obtained in step (3) to dilute it, measure the viscosity until it reaches the required value of 4000-8000 mPa·s, then reduce the speed to defoam and discharge the material to obtain the composite positive electrode slurry.

[0092] The dilution stirring rate is 1500-2000 rpm, the stirring time is 20-30 min, and the defoaming stirring rate is 50-100 rpm.

[0093] In the above steps, the positive electrode active material is at least one of lithium cobalt oxide, lithium nickel manganese oxide, lithium manganese oxide, lithium iron phosphate, or lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminum oxide, with a particle size D50 of 0.5μm-50μm; the conductive carbon includes super pll conductive carbon black and conductive graphite KS-6, conductive graphene, acetylene black, carbon nanotubes, carbon nanofibers (VGCF), and Ketjen black; the binder includes polyvinylidene fluoride (PVDF), polyacrylonitrile (PAN), styrene-butadiene latex (SBR), polyimide (PI), carboxymethyl cellulose (CMC), polytetrafluoroethylene emulsion (PTFE), polyacrylate (PAA), hydrogenated nitrile butadiene rubber, and polyurethane; the solvent includes N,N-dimethylacetamide, n-methylpyrrolidone, dimethyl sulfoxide, tetramethylurea, trimethyl phosphate, and dimethylacetamide. The mass ratio of solid electrolyte material, positive electrode active material, super pll conductive carbon black, conductive graphite KS-6, PVDF, and NMP is (2-15): (81.5-95.2): (1-1.3): (0.5-0.7): (1.3-1.5): (20-800).

[0094] (5) The composite positive electrode slurry is coated on the current collector aluminum foil, and then baked in an oven at 55-130℃ for 2-3 hours to pre-dry it. Then it is transferred to a vacuum oven for drying to finally obtain the positive electrode sheet.

[0095] The vacuum drying conditions include: vacuum degree ≤133Pa, temperature 60~200℃, and time 0.5-72h.

[0096] Fourthly, this application also proposes a solid electrolyte membrane, comprising a solid electrolyte material, wherein the solid electrolyte material includes the solid electrolyte material described above, or the solid electrolyte material is prepared by the preparation method described above.

[0097] The solid electrolyte membrane can be prepared using conventional solid electrolyte membrane preparation methods in the art. In some embodiments, the preparation of the solid electrolyte membrane may include:

[0098] (1) The solid electrolyte material prepared above is mixed with a polymer substrate, lithium salt and solvent (NMP) of at least one or more of the following: polyethylene oxide (PEO), polyethylene glycol (PEG), polytrimethylene carbonate (PTMC), polyvinyl carbonate (PEC), polypropylene carbonate (PPC), polyvinyl carbonate (PVC), polycaprolactone diol (PCL), polyacrylonitrile (PAN), polymethyl methacrylate (PMMA), polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene (PVDF-HFP), carboxymethyl cellulose (CMC), poly(1,3-dioxolane), and polyvinyl carbonate (PVC) in a certain proportion to obtain a polymer substrate-LLZO slurry.

[0099] The weight ratio of solid electrolyte material to polymer substrate such as PVDF is 9:1 to 1:9, the weight ratio of polymer substrate such as PVDF to lithium salt is 1:1 to 1:0.05, and the weight ratio of the total weight of solid electrolyte material to polymer substrate such as PVDF and lithium salt to the weight of solvent is 1:20 to 1:2.

[0100] (2) The polymer substrate - LLZO slurry is coated onto the polytetrafluoroethylene board by solution pouring or spin coating, and the polytetrafluoroethylene board is placed in a 60°C oven for 12 hours to dry the solvent.

[0101] (3) Peel off the composite electrolyte membrane on the polytetrafluoroethylene plate and transfer it to a vacuum oven to dry it to finally obtain a solid electrolyte membrane.

[0102] The vacuum drying conditions include: vacuum degree ≤133Pa, temperature 60~200℃, and time 0.5-72h.

[0103] Fifthly, this application also proposes an all-solid-state battery, comprising a positive electrode, an electrolyte membrane, and a negative electrode, wherein the positive electrode comprises the positive electrode described above, and / or the electrolyte membrane comprises the solid electrolyte membrane described above. In this all-solid-state battery, at least one of the positive electrode and the electrolyte membrane is prepared using the solid electrolyte material described above, thereby obtaining an all-solid-state battery with low interfacial impedance and good cycle stability.

[0104] The all-solid-state battery can be prepared using conventional all-solid-state battery preparation methods in the art. In some embodiments, the preparation of the all-solid-state battery may include: cutting the positive electrode sheet into Φ14mm circular pieces, weighing them, and assembling them with a Φ16mm negative electrode sheet and a solid electrolyte membrane in an argon-filled glove box to form an LIR2025 coin cell. The pouch battery can be manufactured using a stacking process. Specifically, the positive electrode sheet, solid electrolyte membrane, and negative electrode sheet are stacked together sequentially, and then vacuum-sealed and have tabs welded to obtain the pouch battery. The negative electrode sheet can be one of a lithium metal negative electrode, a silicon-based negative electrode, a lithium metal alloy negative electrode, or a lithium-free negative electrode such as copper foil.

[0105] The technical solutions and effects of this application will be described in detail below through specific embodiments and comparative examples. The following embodiments are only some embodiments of this application and are not intended to limit this application in any specific way.

[0106] Example 1

[0107] (1) Preparation of acidic pH adjuster: Weigh 22.51g of acidic substance oxalic acid into 500ml of ethanol and dissolve it completely by sonication to obtain an alcoholic solution of oxalic acid with a concentration of 0.5mol / L.

[0108] The ultrasound conditions included a frequency of 30 kHz and a duration of 5 minutes.

[0109] (2) Li7La3Zr2O 12 Preparation and pH adjustment of (LLZO) solid electrolyte dispersion: 15g of Li7La3Zr2O was prepared by ultrasonication. 12 (LLZO) solid electrolyte nanopowder was dispersed in 50 ml of ethanol to obtain an LLZO solid electrolyte dispersion with a dispersion concentration of 0.3 g / ml; the LLZO solid electrolyte dispersion prepared above was adjusted to neutral (pH 7) using the oxalic acid alcohol solution prepared in step (1) during the process of continuous stirring, and then the pH test was repeated after stirring for another 1 h to ensure that the dispersion remained neutral.

[0110] The ultrasonic dispersion conditions included a frequency of 30 kHz and a duration of 0.5 h; the stirring conditions included a rotation speed of 400 r / min.

[0111] (3) Preparation of solid electrolyte material: Tetraethyl orthosilicate is added to the neutral LLZO solid electrolyte dispersion obtained in step (2), and it is thoroughly mixed by ultrasonication. The solid electrolyte powder is filtered and then placed in an oven to dry until the solvent is completely removed. Finally, LLZO solid electrolyte material coated with tetraethyl orthosilicate is obtained.

[0112] The mass ratio of LLZO solid electrolyte to tetraethyl orthosilicate is 99.5:0.5; the ultrasonic dispersion conditions include a frequency of 50 kHz and a time of 20 min; the drying conditions include a drying temperature of 60 ℃ and a drying time of 24 h.

[0113] (4) Preparation of the positive electrode: Weigh 1g of the solid electrolyte material prepared in step (3) and 47.35g of the positive electrode active material lithium nickel cobalt manganese oxide (LiNi). 0.8 Co 0.1 Mn 0.1 O2 (NCM811), 0.65g of super pll conductive carbon black, 0.35g of conductive graphite KS-6, 13g of polyvinylidene fluoride adhesive with a mass fraction of 5% and solvent were mixed by ball milling to obtain a composite positive electrode slurry. After coating, the slurry was first baked in a 60℃ oven for 3 hours, and then transferred to a vacuum oven for drying to finally obtain the positive electrode sheet.

[0114] Among them, solid electrolyte materials, lithium nickel cobalt manganese oxide (LiNi) 0.8 Co 0.1 Mn 0.1 The mass ratio of O2, super pll conductive carbon black, conductive graphite KS-6, and binder polyvinylidene fluoride (PVDF) is 2:94.7:1.3:0.7:1.3; the ball milling conditions include a speed of 300 r / min and a time of 3 h; the vacuum drying conditions include a vacuum degree ≤133 Pa, a temperature of 100 ℃, and a time of 24 h.

[0115] (5) Preparation of solid electrolyte membrane: The solid electrolyte material obtained in step (3) is mixed with PVDF polymer substrate, lithium salt and solvent in a certain proportion to obtain PVDF-LLZO slurry; the PVDF-LLZO slurry is coated on polytetrafluoroethylene plate by spin coating, and the polytetrafluoroethylene plate is placed in a 60℃ oven for 12h to dry the solvent; the composite electrolyte membrane on the polytetrafluoroethylene plate is peeled off and transferred to a vacuum oven for drying to finally obtain PVDF-LLZO solid electrolyte membrane.

[0116] The solid electrolyte material is composed of PVDF, lithium salt, and solvent in a ratio of 8:2:2:60. The vacuum drying conditions include a vacuum degree ≤133Pa, a temperature of 100℃, and a time of 24h.

[0117] (6) An all-solid-state battery, comprising a negative electrode silicon-carbon electrode sheet, a composite positive electrode sheet prepared above, and a PVDF-LLZO composite solid electrolyte membrane. Specific manufacturing method for coin cell assembly: The positive electrode sheet prepared above is cut into Φ14mm round pieces, weighed, and then assembled with a Φ16mm negative electrode sheet and a PVDF-LLZO solid electrolyte membrane in an argon-filled glove box to form an LIR2025 coin cell.

[0118] Example 2

[0119] This embodiment is basically the same as Embodiment 1, except that the preparation steps of the solid electrolyte material are as follows, that is, steps (1) to (3) are changed to:

[0120] (1) Preparation of acidic pH adjuster: Weigh 45.02g of acidic acetic acid into 500ml of ethylene glycol and dissolve it completely by sonication to obtain an alcoholic solution of acetic acid with a concentration of 1mol / L.

[0121] The ultrasound conditions included a frequency of 40 kHz and a duration of 20 min.

[0122] (2) Li7La3Zr2O 12 Preparation and pH adjustment of (LLZO) solid electrolyte dispersion: 15g of Li7La3Zr2O was prepared by ultrasonication. 12 (LLZO) solid electrolyte nanopowder was dispersed in 150 ml of ethylene glycol to obtain an LLZO solid electrolyte dispersion with a dispersion concentration of 0.1 g / ml; the LLZO solid electrolyte dispersion prepared above was adjusted to neutral (pH 8) using the oxalic acid alcohol solution prepared in step (1) during the process of continuous stirring, and then the pH test was repeated after stirring for another 1 h to ensure that the dispersion remained neutral.

[0123] The ultrasonic dispersion conditions included a frequency of 1 kHz and a duration of 3 h; the stirring conditions included a rotation speed of 400 r / min.

[0124] (3) Preparation of solid electrolyte material: Tetraethyl orthosilicate is added to the neutral LLZO solid electrolyte dispersion obtained in step (2), and it is thoroughly mixed by ultrasonication. The solid electrolyte powder is filtered and then placed in an oven to dry until the solvent is completely removed. Finally, LLZO solid electrolyte material coated with tetraethyl orthosilicate is obtained.

[0125] The mass ratio of LLZO solid electrolyte to tetraethyl orthosilicate is 99.9:0.1; the ultrasonic dispersion conditions include a frequency of 100 kHz and a time of 300 min; the drying conditions include a drying temperature of 10 ℃ and a drying time of 72 h.

[0126] Example 3

[0127] This embodiment is basically the same as Embodiment 1, except that the preparation steps of the solid electrolyte material are as follows, that is, steps (1) to (3) are changed to:

[0128] (1) Preparation of acidic pH adjuster: Weigh 135.06g of acidic substance oxalic acid into 500ml of ethanol and dissolve it completely by sonication to obtain an alcoholic solution of oxalic acid with a concentration of 3mol / L.

[0129] The ultrasound conditions included a frequency of 50 kHz and a duration of 10 min.

[0130] (2) Li7La3Zr2O 12 Preparation and pH adjustment of (LLZO) solid electrolyte dispersion: 100g of Li7La3Zr2O was prepared by ultrasonication. 12 (LLZO) solid electrolyte nanopowder was dispersed in 50 ml of ethanol to obtain an LLZO solid electrolyte dispersion with a dispersion concentration of 2 g / ml; the LLZO solid electrolyte dispersion prepared above was adjusted to neutral (pH 7.5) using the oxalic acid alcohol solution prepared in step (1), and the mixture was stirred continuously during the process. After stirring for another 1 h, the pH test was repeated to ensure that the dispersion remained neutral.

[0131] The ultrasonic dispersion conditions included a frequency of 50 kHz and a duration of 0.05 h; the stirring conditions included a rotation speed of 400 r / min.

[0132] (3) Preparation of solid electrolyte material: Tetraethyl orthosilicate is added to the neutral LLZO solid electrolyte dispersion obtained in step (2), and it is thoroughly mixed by ultrasonication. The solid electrolyte powder is filtered and then placed in an oven to dry until the solvent is completely removed. Finally, LLZO solid electrolyte material coated with tetraethyl orthosilicate is obtained.

[0133] The mass ratio of LLZO solid electrolyte to tetraethyl orthosilicate is 50:50; the ultrasonic dispersion conditions include a frequency of 100 kHz and a time of 1 min; the drying conditions include a drying temperature of 100 ℃ and a drying time of 1 h.

[0134] Example 4

[0135] This embodiment is basically the same as embodiment 1, except that in this embodiment, the Li7La3Zr2O in step (2) is different. 12 (LLZO) solid electrolyte nanopowder was replaced with Li 6.4 La3Zr 1.4 Ta 0.6 O 12(LLZTO) solid electrolyte nanopowder.

[0136] Example 5

[0137] This embodiment is basically the same as Embodiment 1, except that in this embodiment, in step (4), the positive electrode active material is lithium nickel cobalt manganese oxide (LiNi). 0.8 Co 0.1 Mn 0.1 O2 was replaced with lithium cobalt oxide (LiCoO2).

[0138] Comparative Example 1

[0139] This comparative example is basically the same as Example 1, except that the solid electrolyte material in this comparative example is Li7La3Zr2O. 12 (LLZO) solid electrolyte nanoparticles, i.e., Li7La3Zr2O without pH adjustment and tetraethyl orthosilicate coating. 12 (LLZO) solid electrolyte nanopowder.

[0140] Accordingly, in this comparative example, the solid electrolyte material used in steps (4) to (6) was also changed to Li7La3Zr2O. 12 (LLZO) solid electrolyte nanopowder.

[0141] Experimental Example 1

[0142] The PVDF-LLZO slurry prepared in Example 1 and Comparative Example 1 during the preparation of the solid electrolyte membrane was placed in a normal temperature and humidity environment for 2 days. Observations were taken at 0 days, 0.5 days, 1.5 days, and 2 days. After 2 days, the slurry states of Example 1 and Comparative Example 1 were as follows: Figure 4 As shown.

[0143] result: Figure 4 In the figure, the slurry in the left vial is the slurry of Comparative Example 1, and the slurry in the right vial is the slurry of Example 1. As can be seen from the figure, after two days of standing, the slurry of Example 1 remains a white, uniform slurry, showing stable stability, while the slurry in Comparative Example 1 appears as a brown, layered slurry, gradually gelling and becoming unsuitable for further coating. Clearly, the solid electrolyte material slurry proposed in this application exhibits superior environmental stability.

[0144] Experimental Example 2

[0145] The all-solid-state batteries prepared in Examples 1-5 and Comparative Example 1 were subjected to performance testing, including initial internal resistance testing, capacity recording, and cycle performance testing. The testing methods are as follows:

[0146] The test results are shown in Table 1 and Figure 5 and 6 As shown. Figure 5 In the figure, the horizontal axis (cycle number) refers to the number of cycles, and the vertical axis (specific capacity) refers to the specific capacity, with the unit being mAh / g. Figure 6 In the diagram, the horizontal axis (specific capacity) refers to the specific capacity, measured in mAh / g; the vertical axis (Voltage) refers to the voltage, measured in V vs. Li. + / Li.

[0147] Table 1

[0148]

[0149]

[0150] From Table 1 and Figure 5 and Figure 6 As can be seen, the coated LLZO constructed a better ion pathway in the cathode of the solid-state battery of Example 1, thus exhibiting a lower initial impedance value and a higher initial capacity. Simultaneously, the solid-state battery of Example 1 maintained a higher capacity retention rate (78%) during cycling, indicating that the improved interface-modified LLZO electrolyte can better maintain the internal ion pathways of the electrode during cycling.

[0151] The solid electrolyte materials and their preparation methods, positive electrode sheets, solid electrolyte membranes, and all-solid-state batteries provided in the embodiments of this application have been described in detail above. Specific examples have been used 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 methods and core ideas of this application. At the same time, for those skilled in the art, there will be changes in the specific implementation methods and application scope based on the ideas of this application. Therefore, the content of this specification should not be construed as a limitation of this application.

Claims

1. A method for preparing a solid electrolyte material, characterized in that, Includes the following steps: A lithium lanthanum zirconium oxy-based solid electrolyte is dispersed in a first solvent to prepare an electrolyte dispersion with a concentration of 0.1~2 g / ml. An acidic pH adjuster is added to the electrolyte dispersion to adjust the pH of the electrolyte dispersion to 7-8, thereby obtaining a neutral dispersion. The weight ratio of lithium lanthanum zirconium oxysolid electrolyte to orthosilicate in the neutral dispersion is (50-99.9):(50-0.1). Orthosilicate is added to the neutral dispersion and mixed to obtain a dispersion solution; during the mixing process, the orthosilicate reacts to form polysiloxane, which coats the surface of the lithium lanthanum zirconium oxide solid electrolyte. The dispersion solution is subjected to electrolyte separation and drying treatment to obtain a solid electrolyte material.

2. The preparation method according to claim 1, characterized in that, The orthosilicate includes one or more of ethyl orthosilicate, butyl orthosilicate, methyl orthosilicate, and isopropyl orthosilicate; and / or, The chemical formula of the lithium lanthanum zirconium oxide solid electrolyte is Li 5+x La3Zr x M 2-x O 12 M is selected from any one of Ta, Nb, Hf, Al, Si, Ga, Sc, Ti, V, Y and Sn, and x is 0 to 0.

6.

3. The preparation method according to claim 1, characterized in that, In the step of dispersing the lithium lanthanum zirconium oxy-based solid electrolyte in a first solvent to prepare an electrolyte dispersion: The first solvent comprises one or more of alcohols, alkanes having 3 to 8 carbon atoms, and aromatic hydrocarbons having 6 to 10 carbon atoms; the alcohols include one or more of methanol, ethanol, ethylene glycol, and isopropanol; the alkanes having 3 to 8 carbon atoms include n-hexane; and the aromatic hydrocarbons having 6 to 10 carbon atoms include toluene; and / or, The lithium lanthanum zirconium oxy-based solid electrolyte is dispersed in the first solvent by ultrasound, wherein the frequency of the ultrasound is 1~50 kHz and the duration of the ultrasound is 0.05~3 h; and / or, The drying process employs an oven-drying method, with a drying temperature of 10~100℃ and a drying time of 1~72 hours; and / or, In the step of adding orthosilicate to the neutral dispersion and mixing to obtain a dispersion solution, the mixing is performed by ultrasound, the frequency of which is 1~100kHz and the duration of which is 1~300min.

4. The preparation method according to claim 1, characterized in that, Before adding the acidic pH adjuster to the electrolyte dispersion, the method further includes: adding an acidic substance to a second solvent to dissolve and obtain the acidic pH adjuster, wherein the acidic substance includes an organic acid, and the second solvent includes one or more of alcohols, alkanes with 3 to 8 carbon atoms, and aromatic hydrocarbons with 6 to 10 carbon atoms, wherein the alcohols include one or more of methanol, ethanol, ethylene glycol, and isopropanol, the alkanes with 3 to 8 carbon atoms include n-hexane, and the aromatic hydrocarbons with 6 to 10 carbon atoms include toluene.

5. The preparation method according to claim 4, characterized in that, The organic acid includes one or more of formic acid, acetic acid, and oxalic acid; and / or, The concentration of the acidic substance in the acidic pH adjuster is 0.5~3 mol / L; and / or, After the acidic substance is added to the second solvent, it is subjected to ultrasonic treatment to dissolve the acidic substance. The frequency of the ultrasonic treatment is 30~50kHz and the duration of the ultrasonic treatment is 5~20min.

6. A solid electrolyte material, characterized in that, The solid electrolyte material is prepared by the preparation method according to any one of claims 1 to 5, wherein the solid electrolyte material comprises a lithium lanthanum zirconium oxy solid electrolyte and a modification layer coating the lithium lanthanum zirconium oxy solid electrolyte, and the material of the modification layer comprises polysiloxane.

7. The solid electrolyte material according to claim 6, characterized in that, In the solid electrolyte material, the weight percentage of the lithium lanthanum zirconium oxide solid electrolyte is 50.1% to 99.9%; and / or, The solid electrolyte material is a powder, and the average particle size of the solid electrolyte material is 50~900nm.

8. A positive electrode sheet, characterized in that, The solid electrolyte material includes the solid electrolyte material according to claim 6 or 7, or the solid electrolyte material is prepared by the preparation method according to any one of claims 1 to 5.

9. A solid electrolyte membrane, characterized in that, The solid electrolyte material includes the solid electrolyte material according to claim 6 or 7, or the solid electrolyte material is prepared by the preparation method according to any one of claims 1 to 5.

10. An all-solid-state battery, characterized in that, It includes a positive electrode, an electrolyte membrane, and a negative electrode, wherein the positive electrode includes the positive electrode as described in claim 8, and / or the electrolyte membrane includes the solid electrolyte membrane as described in claim 9.

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