Solid-state electrolyte, and preparation method therefor and use thereof

Abstract

A solid-state electrolyte, and a preparation method therefor and the use thereof. The solid-state electrolyte comprises a solid-state electrolyte substrate and a coating layer on the surface of the solid-state electrolyte substrate, wherein the coating layer comprises an inorganic substance having a sublimation temperature of less than 500°C; and the coating coverage of the solid-state electrolyte is greater than or equal to 90%. In the solid-state electrolyte, by introducing the coating layer onto the surface of the solid-state electrolyte substrate and using the inorganic substance having a sublimation temperature of less than 500°C as a coating material, with the coating coverage being greater than or equal to 90%, the interfacial impedance between the solid-state electrolyte and an electrode material can be reduced, and microscopic defects and pores on the surface of the solid-state electrolyte substrate can be filled; moreover, direct exposure of the solid-state electrolyte matrix to the environment can be prevented, and chemical bonds can be formed with certain metal elements in the solid-state electrolyte substrate, thereby improving the ionic conductivity retention and stability of the solid-state electrolyte. When applied to a battery, the solid-state electrolyte can improve the specific capacity and the initial coulombic efficiency of the battery.

Description

A solid electrolyte, its preparation method and application

[0001] This application claims priority to Chinese Patent Application No. 202510112253.6, filed on January 23, 2025, entitled "A solid electrolyte and its preparation method and application", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application belongs to the field of battery technology, and in particular relates to a solid electrolyte, its preparation method and application. Background Technology

[0003] While traditional liquid electrolytes have been widely used in batteries and other energy storage devices, their inherent safety issues (such as leakage, flammability, and thermal runaway) have limited their development in high-energy-density and high-safety applications. The emergence of solid-state electrolytes offers a new approach to solving these problems.

[0004] However, existing solid electrolytes still suffer from poor stability and low retention of ionic conductivity, resulting in low specific capacity and initial coulombic efficiency of the battery. Summary of the Invention

[0005] The main objective of this application is to provide a solid electrolyte with good stability and high ionic conductivity retention. When applied to batteries, it can improve the specific capacity and initial coulombic efficiency of the batteries.

[0006] This application also provides a method for preparing a solid electrolyte, which can prepare the above-mentioned solid electrolyte and is simple and low in cost.

[0007] This application also provides a positive electrode sheet including the above-mentioned solid electrolyte. Therefore, when this positive electrode sheet is applied to a battery, it can improve the battery's specific capacity and initial coulombic efficiency.

[0008] This application also provides a battery comprising the above-described solid electrolyte or the above-described positive electrode, thus the battery has excellent specific capacity and initial coulombic efficiency.

[0009] In a first aspect, this application provides a solid electrolyte, including a solid electrolyte matrix and a coating layer present on the surface of the solid electrolyte matrix, wherein the coating layer includes an inorganic material with a sublimation temperature of less than 500°C;

[0010] The solid electrolyte has a coating rate of 90% or greater.

[0011] In the solid electrolyte described above, the thickness of the coating layer is 0.1 nm-100 nm, preferably 2 nm-20 nm.

[0012] In the solid electrolyte described above, the electronegativity of the bonding elements in the inorganic material is 2.0-2.8.

[0013] In the solid electrolyte described above, the coating layer comprises elemental sulfur.

[0014] The solid electrolyte as described above, wherein the solid electrolyte matrix comprises a halide solid electrolyte.

[0015] The solid electrolyte described above, wherein the chemical composition of the halide solid electrolyte is Li a MX b M is selected from at least one of Mg, Al, Ga, In, Sb, Bi, Y, Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Zr, Hf, Cr, Fe, Zn and Cd, and X is selected from at least one of Cl, Br, I and F, 1≤a≤3, 1≤b≤6.

[0016] In the solid electrolyte described above, M is selected from at least one of Ga, In, Y, Sc, Ho, Yb, Lu, Zr, and Hf;

[0017] And / or, the X is selected from Cl and / or Br.

[0018] In the solid electrolyte described above, the difference between the binding energy between the elements of the inorganic material and the binding energy between the elements of the inorganic material and the elements of the solid electrolyte matrix is ​​0.1 eV-2.0 eV.

[0019] The solid electrolyte described above has an ionic conductivity greater than 0.3 mS / cm.

[0020] Secondly, this application provides a method for preparing the solid electrolyte as described above, comprising the following steps:

[0021] The solid electrolyte is obtained by heat-treating a raw material system comprising a solid electrolyte matrix and a coating source and then cooling it.

[0022] Wherein, the temperature of the heat treatment is greater than the sublimation temperature of the coating source;

[0023] The mass ratio of the solid electrolyte matrix to the coating source is (100-1000):1.

[0024] In the preparation method of the solid electrolyte as described above, the heat treatment is carried out in a closed environment;

[0025] And / or, the sublimation temperature of the coating source is less than 500°C;

[0026] And / or, the temperature of the heat treatment is 150℃-500℃.

[0027] Thirdly, this application provides a positive electrode sheet, comprising the solid electrolyte as described above or the solid electrolyte prepared by the method described above.

[0028] Fourthly, this application provides a battery comprising a solid electrolyte as described above, a solid electrolyte prepared by the method described above, or a positive electrode as described above.

[0029] The solid electrolyte provided in this application, by introducing a coating layer on the surface of the solid electrolyte matrix and using an inorganic material with a sublimation temperature of less than 500°C as the coating material, with a coating rate greater than or equal to 90%, can reduce the interfacial impedance between the solid electrolyte and the electrode material, and fill the microscopic defects and pores on the surface of the solid electrolyte matrix. At the same time, it can prevent the solid electrolyte matrix from being directly exposed to the environment, and can also form chemical bonds with certain metal elements in the solid electrolyte matrix, thereby improving the ionic conductivity retention and stability of the solid electrolyte. When applied to batteries, it can improve the specific capacity and initial coulombic efficiency of the battery. Attached Figure Description

[0030] To more clearly illustrate the technical solutions in the embodiments of this application or related technologies, the accompanying drawings used in the description of the embodiments of this application or related technologies are briefly introduced below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0031] Figure 1 shows the SEM and EDS images of the solid electrolyte of Embodiment 1 of this application, where a is the SEM image of the solid electrolyte of Embodiment 1 of this application and b is the EDS image of the solid electrolyte of Embodiment 1 of this application.

[0032] Figure 2 shows the SEM and EDS images of the solid electrolyte of Comparative Example 2 of this application, where a is the SEM image of the solid electrolyte of Comparative Example 2 of this application and b is the EDS image of the solid electrolyte of Comparative Example 2 of this application.

[0033] Figure 3 shows the XPS energy spectrum of the solid electrolyte of Comparative Example 2 of this application;

[0034] Figure 4 is the XPS energy spectrum of the solid electrolyte of Example 1 of this application. Detailed Implementation

[0035] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, 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.

[0036] In the development of modern energy storage technologies, solid-state electrolytes have attracted much attention due to their potential for high safety and high energy density. However, existing solid-state electrolyte technologies still face many challenges that limit their widespread adoption in commercial applications.

[0037] First, the stability of solid-state electrolytes is a particularly prominent issue. In environments with high air or humidity, many solid-state electrolytes are prone to degradation reactions, leading to a significant decrease in their ionic conductivity retention. This instability directly affects the battery's specific capacity and initial coulombic efficiency, making it difficult to meet the requirements of high-performance energy storage devices.

[0038] Secondly, traditional coating modification methods also have limitations in improving the performance of solid electrolytes. While solvent coating can improve electrolyte stability to some extent, it also introduces new problems, such as solvent residue potentially altering the electrolyte's chemical properties or even destroying its structure. Furthermore, the use of solvents increases production costs, hindering large-scale applications. Solvent-free direct mixing methods, on the other hand, easily lead to poor solid-solid contact, uneven coating, and uncoated electrolyte portions exposed to air, further exacerbating its instability. Although atomic deposition technology can achieve uniform coating, its high cost and complex process limit its application in large-scale production.

[0039] Based on this, in a first aspect, this application provides a solid electrolyte, including a solid electrolyte matrix and a coating layer present on the surface of the solid electrolyte matrix. The coating layer includes an inorganic material with a sublimation temperature of less than 500°C, for example, it can be a range consisting of 60°C, 70°C, 80°C, 90°C, 100°C, 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C or any two thereof; the coating rate of the solid electrolyte is greater than or equal to 90%, for example, it can be a range consisting of 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, 100% or any two thereof.

[0040] The solid electrolyte provided in this application exhibits high ionic conductivity retention and stability. When applied to batteries, it can improve the specific capacity and initial coulombic efficiency. This is because the coating layer and its high coating ratio improve the interfacial contact between the solid electrolyte and the electrode materials. Good interfacial contact reduces charge accumulation and interfacial reactions at the interface, thereby lowering interfacial impedance and improving ion transport efficiency at the interface, thus enhancing the overall ionic conductivity retention. Furthermore, the inorganic material with a sublimation temperature below 500°C can fill microscopic defects and pores on the surface of the solid electrolyte matrix during deposition. This filling effect reduces ion scattering and trapping effects during transport, thereby improving ionic conductivity retention.

[0041] Furthermore, the inorganic coating layer enables uniform coating of the solid electrolyte matrix, and the high coating rate avoids the problem of poor solid-solid contact. The uniform coating layer effectively protects the electrolyte matrix, preventing it from being directly exposed to the environment and reducing the impact of environmental factors on electrolyte performance. Moreover, inorganic materials with a sublimation temperature below 500℃ can form chemical bonds with certain metal elements in the solid electrolyte matrix, further improving the stability of the solid electrolyte in air, helping to maintain the structural integrity of the solid electrolyte, reducing obstacles in the ion transport process, and thus improving the retention rate of ionic conductivity. When applied to batteries, this solid electrolyte can improve the battery's specific capacity and initial coulombic efficiency.

[0042] Therefore, the solid electrolyte provided in this application, by introducing a coating layer on the surface of the solid electrolyte matrix and using an inorganic material with a sublimation temperature of less than 500°C as the coating material, with a coating rate greater than or equal to 90%, can reduce the interfacial impedance between the solid electrolyte and the electrode material, fill the microscopic defects and pores on the surface of the solid electrolyte matrix; at the same time, it can prevent the solid electrolyte matrix from being directly exposed to the environment, and can also form chemical bonds with certain metal elements in the solid electrolyte matrix, thereby improving the ionic conductivity retention rate and stability of the solid electrolyte. When applied to batteries, it can improve the specific capacity and initial coulombic efficiency of the battery.

[0043] In this application, the coating ratio of the solid electrolyte can be adjusted by controlling the relationship between the heat treatment temperature and the sublimation temperature of the coating source, as well as the mass ratio of the solid electrolyte matrix to the coating source.

[0044] In some embodiments of this application, the thickness of the coating layer is 0.1nm-100nm, for example, it can be a range of 0.1nm, 1nm, 2nm, 5nm, 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 80nm, 90nm, 100nm or any two of these, preferably 2nm-20nm.

[0045] The coating thickness in this application is within the aforementioned range, allowing ions to pass through effectively without significantly increasing the resistance to ion transport paths, which is beneficial for improving the overall ionic conductivity retention of the solid electrolyte. Furthermore, a coating of suitable thickness provides sufficient physical and chemical coating to improve the interfacial stability between the solid electrolyte and the electrode, helping to prevent interfacial reactions and solid electrolyte degradation, thereby improving the battery's specific capacity and initial coulombic efficiency. In addition, a coating of suitable thickness can effectively isolate the electrolyte from the influence of the external environment, such as the intrusion of moisture and oxygen, while also providing a certain degree of thermal protection to prevent the solid electrolyte from degrading at high temperatures, thus improving the stability of the solid electrolyte.

[0046] In some embodiments of this application, the electronegativity of the bonding elements in the inorganic material is 2.0-2.8, for example, it can be a range consisting of 2.0, 2.1, 2.2, 2.3, 2.4, 2.5, 2.6, 2.7, 2.8 or any two of them.

[0047] It is understandable that the electronegativity of bonding elements in inorganic materials refers to the element in the inorganic material that bonds with the metal element in the solid electrolyte matrix. The magnitude of electronegativity can characterize the element's ability to attract shared electron pairs in chemical bonds.

[0048] The electronegativity of the inorganic material in this application is within the above-mentioned range, which can reduce the degree of electron loss of the metal elements in the solid electrolyte matrix, and the metal elements react with OH groups. - The weaker binding affinity of the coating reduces the sensitivity of the solid electrolyte matrix to water, thereby improving the stability of the solid electrolyte. Furthermore, inorganic materials with appropriate electronegativity can optimize ion conduction pathways. Since electronegativity affects the electronic structure and bonding characteristics of materials, it influences ion migration ability. Suitable electronegativity can improve the ion conduction efficiency in the coating layer, i.e., improve ion conductivity retention. This, in turn, can improve the specific capacity and initial coulombic efficiency of the battery.

[0049] In some embodiments of this application, the coating layer comprises elemental sulfur.

[0050] The coating layer in this application includes elemental sulfur, which can protect the solid electrolyte matrix from environmental influences and improve the stability of the solid electrolyte. Furthermore, elemental sulfur can replace certain elements in the solid electrolyte matrix and form chemical bonds with the metal elements in the solid electrolyte matrix, further improving the stability of the solid electrolyte in air. In addition, elemental sulfur can form good interfacial contact with the solid electrolyte matrix, reducing interfacial impedance and thus improving ion transport efficiency, thereby enhancing the ionic conductivity retention rate of the solid electrolyte. It can also fill microscopic defects and pores on the surface of the solid electrolyte matrix, further improving the ionic conductivity retention rate.

[0051] In some embodiments of this application, the solid electrolyte matrix includes a halide solid electrolyte.

[0052] Specifically, the chemical composition of the halide solid electrolyte is Li a MX b Wherein, M is selected from at least one of Mg, Al, Ga, In, Sb, Bi, Y, Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Zr, Hf, Cr, Fe, Zn, and Cd, X is selected from at least one of Cl, Br, I, and F, 1≤a≤3, for example, it can be a range consisting of 1, 1.1, 1.2, 1.3, 1.4, 1.5, 1.8, 2, 2.2, 2.5, 2.7, 3 or any two of them, and 1≤b≤6, for example, it can be a range consisting of 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5, 5, 5.5, 6 or any two of them.

[0053] The solid electrolyte matrix in this application includes materials with a chemical composition of Li. a MX b The halide solid electrolyte exhibits strong lithium-ion migration within the halide lattice, particularly in suitable crystal structures, which enhances the retention of ionic conductivity. Elements M and X form stable compounds, making the solid electrolyte less prone to decomposition or side reactions under battery operating conditions, thus improving battery safety and lifespan. Furthermore, elements M and X improve the interfacial compatibility between the solid electrolyte and electrode materials, reducing interfacial impedance and contributing to enhanced overall electrochemical performance of the battery.

[0054] In some embodiments of this application, M is selected from at least one of Ga, In, Y, Sc, Ho, Yb, Lu, Zr and Hf.

[0055] In some embodiments, X is selected from Cl and / or Br.

[0056] As a preferred option, when M is selected from at least one of the above elements and X is selected from Cl and / or Br, the ionic conductivity retention rate of the solid electrolyte can be further improved, the safety and life of the battery can be improved, and the overall electrochemical performance of the battery can be improved.

[0057] In some embodiments of this application, the difference between the binding energy between the elements of the inorganic material and the binding energy between the elements of the inorganic material and the elements of the solid electrolyte matrix is ​​0.1 eV-2.0 eV, for example, it can be a range of 0.1 eV, 0.5 eV, 1.0 eV, 1.2 eV, 1.6 eV, 2.0 eV or any two of these.

[0058] In this application, the difference between the binding energy between inorganic elements and the binding energy between inorganic elements and the elements of the solid electrolyte matrix falls within the aforementioned range. This indicates that the coating layer forms chemical bonds with certain metal elements in the solid electrolyte matrix, which improves the stability of the solid electrolyte, helps maintain its structural integrity, reduces obstacles in ion transport, and thus improves the retention rate of ionic conductivity. When this solid electrolyte is applied to batteries, it can improve the battery's specific capacity and initial coulombic efficiency.

[0059] In some embodiments of this application, the ionic conductivity of the solid electrolyte is greater than 0.3 mS / cm, for example, it can be a range of 0.3 mS / cm, 0.4 mS / cm, 0.5 mS / cm, 0.6 mS / cm, 0.7 mS / cm, 0.8 mS / cm, 1 mS / cm, 1.5 mS / cm, 2 mS / cm, 3 mS / cm, 4 mS / cm, 5 mS / cm, 10 mS / cm, 20 mS / cm, 30 mS / cm, 50 mS / cm, or any combination thereof.

[0060] The solid electrolyte in this application has an ionic conductivity greater than 0.3 mS / cm, which means that ions can migrate rapidly in the electrolyte, thereby improving the specific capacity and initial coulombic efficiency of the battery.

[0061] Secondly, this application provides a method for preparing the solid electrolyte as described above, comprising the following steps:

[0062] A raw material system comprising a solid electrolyte matrix and a coating source is heat-treated and then cooled to obtain a solid electrolyte; wherein the heat treatment temperature is higher than the sublimation temperature of the coating source; the mass ratio of the solid electrolyte matrix to the coating source is (100-1000):1, for example, it can be a range of 100:1, 200:1, 400:1, 500:1, 700:1, 1000:1 or any two of them.

[0063] The method for preparing the solid electrolyte in this application involves heat treatment at a temperature higher than the sublimation temperature of the coating source, and limiting the mass ratio of the solid electrolyte matrix to the coating source to (100-1000):1, so that the coating source sublimates into a gaseous state and coats the surface of the solid electrolyte matrix, i.e., gas-solid contact. Then, after cooling, the coating source is uniformly coated on the surface of the solid electrolyte matrix.

[0064] Specifically, the solid electrolyte matrix and the coating source can be stirred and mixed evenly according to the above mass ratio to obtain a mixture. Then, the mixture is subjected to heat treatment, wherein the heat treatment temperature is higher than the sublimation temperature of the coating source and lower than the destruction temperature of the solid electrolyte matrix. After cooling, the solid electrolyte of the first aspect of this application is obtained.

[0065] The solid electrolyte preparation method of this application does not require the use of solvents, does not damage the structure of the solid electrolyte matrix, and the coating process is a gas-solid contact rather than a solid-solid contact, which can form a uniform coating layer on the surface of the solid electrolyte matrix. The coating layer can form chemical bonds with certain metal elements in the solid electrolyte matrix, rather than a single physical coating, thereby enabling the obtained solid electrolyte to have a high retention rate and stability of ionic conductivity, which in turn can improve the specific capacity and initial coulombic efficiency of the battery.

[0066] In some embodiments of this application, the heat treatment is carried out in a closed environment, which makes it difficult for the coating source to diffuse to the outside after sublimation, and more coating source is coated on the surface of the solid electrolyte matrix, which is beneficial to improving the coating rate of the solid electrolyte.

[0067] In practice, the solid electrolyte matrix and the coating source can be loaded into a glass tube, and then the glass tube can be vacuum sealed and heat-treated.

[0068] In some embodiments, the sublimation temperature of the coating source is less than 500°C, for example, it can be a range of 60°C, 70°C, 80°C, 90°C, 100°C, 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C or any combination thereof.

[0069] In some embodiments, the heat treatment temperature is 150°C-500°C, for example, it can be a range of 150°C, 200°C, 250°C, 300°C, 350°C, 400°C, 450°C, 500°C or any combination thereof.

[0070] In this application, the sublimation temperature and heat treatment temperature of the coating source are within the aforementioned range, which is beneficial for the sublimation of the coating source, allowing it to smoothly sublimate into a gaseous state and coat the surface of the solid electrolyte substrate. After cooling, the coating source is uniformly coated on the surface of the solid electrolyte substrate. This helps improve the retention rate and stability of the ionic conductivity of the solid electrolyte, thereby increasing the specific capacity and initial coulombic efficiency of the battery.

[0071] Thirdly, this application provides a positive electrode sheet, comprising the solid electrolyte as described above or the solid electrolyte prepared by the method described above.

[0072] The positive electrode provided in this application includes the aforementioned solid electrolyte. Therefore, when this positive electrode is applied to a battery, it can improve the battery's specific capacity and initial coulombic efficiency.

[0073] The present application does not limit the preparation method of the positive electrode sheet. In a specific embodiment, the positive electrode active material, solid electrolyte, conductive agent, binder, etc. can be mixed and dispersed in a solvent to prepare a positive electrode paste. Subsequently, the positive electrode paste is coated on at least one functional surface of the positive electrode current collector, and after drying and rolling, a positive electrode sheet including a solid electrolyte inside is obtained. Further, a dispersion liquid including a solid electrolyte can also be prepared, and the dispersion liquid is coated on the surface of the above positive electrode sheet to obtain a positive electrode sheet including a solid electrolyte both inside and on the surface.

[0074] Alternatively, the positive electrode active material, conductive agent, binder, etc. are mixed and dispersed in a solvent to prepare a positive electrode paste, and at the same time, a dispersion liquid including a solid electrolyte can also be prepared. Subsequently, the positive electrode paste is coated on at least one functional surface of the positive electrode current collector, and after drying, the dispersion liquid is coated on the dried surface, and after drying again and rolling, a positive electrode sheet including a solid electrolyte on the surface is obtained.

[0075] The present application does not make special limitations on the positive electrode active material, conductive agent, and binder. For example, the positive electrode active material is selected from lithium iron phosphate (LiFePO4), lithium cobalt oxide (LiCoO2), lithium nickel cobalt manganese oxide (Li z Ni x Co y Mn 1-x-y O2, where 0.95 ≤ z ≤ 1.05, x > 0, y > 0, 0 < x + y < 1), lithium manganese oxide (LiMnO2), lithium nickel cobalt aluminum oxide (Li z Ni x Co y Al 1-x-y O2, where 0.95 ≤ z ≤ 1.05, x > 0, y > 0, 0.8 ≤ x + y < 1), lithium nickel cobalt manganese aluminum oxide (Li z Ni x Co y Mn w Al 1-x-y-w O2, where 0.95 ≤ z ≤ 1.05, x > 0, y > 0, w > 0, 0.8 ≤ x + y + w < 1), nickel cobalt aluminum tungsten material*, lithium-rich manganese-based solid solution positive electrode material (xLi2MnO3·(1 - x)LiMO2, where M = Ni / Co / Mn, 0 < x < 1), lithium nickel cobalt oxide (LiNi x CoyO2, where x > 0, y > 0, x + y = 1), lithium nickel titanium magnesium oxide (LiNi x Ti y Mg z *Note: "镍钴铝钨材料" is translated as "nickel cobalt aluminum tungsten material" here. It might need to be further verified according to the specific context if it has a more specific name in the relevant technical field.O2, where x>0, y>0, z>0, x+y+z=1), lithium nickel oxide (Li2NiO2), lithium spinel manganese oxide (LiMn2O4), nickel-cobalt-tungsten materials or combinations thereof; the conductive agent is selected from at least one of conductive carbon black, Ketjen black, conductive fiber, conductive polymer, acetylene black, carbon nanotubes, graphene, flake graphite, conductive oxide, metal particles; the binder is selected from at least one of polyvinylidene fluoride and its copolymer derivatives, polytetrafluoroethylene and its copolymer derivatives, polyacrylic acid and its copolymer derivatives, polyhexafluoropropylene and its copolymer derivatives.

[0076] Fourthly, this application provides a battery comprising a solid electrolyte as described above, a solid electrolyte prepared by the method described above, or a positive electrode as described above.

[0077] The battery described in this application exhibits outstanding performance in terms of specific capacity and initial coulombic efficiency.

[0078] This application does not limit the method of battery preparation. For example, it can be prepared by sequentially stacking a positive electrode, a solid electrolyte, and a negative electrode and then encapsulating them. Alternatively, a basic cell can be formed by sequentially stacking a positive electrode, a separator, and a negative electrode, then injecting a precursor solution into it, fully impregnating it, and then baking it to obtain the lithium-ion battery of this application.

[0079] The positive and negative electrodes in the battery of this application have no special requirements compared to existing positive and negative electrodes in the art.

[0080] The technical solution of this application will be further described below with reference to specific embodiments.

[0081] Example 1

[0082] The preparation method of the solid electrolyte in this embodiment includes the following steps:

[0083] 1) Elemental sulfur (sublimation temperature 171℃, electronegativity 2.58) was stirred and mixed evenly with solid electrolyte matrix Li3YCl6 to obtain a mixture; wherein the mass ratio of solid electrolyte matrix Li3YCl6 to coated source elemental sulfur was 700:1.

[0084] 2) The mixture was placed in a glass tube, which was then vacuum-sealed. The sealed glass tube containing the mixture was then heat-treated at 200℃. After cooling, a solid electrolyte was obtained. The solid electrolyte consisted of a solid electrolyte matrix Li3YCl6 and a coating layer of elemental sulfur on the surface of the Li3YCl6 matrix. The coating layer was 5 nm thick, the coating efficiency was 95%, and the ionic conductivity was 0.6 mS / cm. In the XPS spectrum, the binding energy of the SS bond in elemental sulfur was 164.0 eV, and the binding energy of the SY bond formed between elemental sulfur and the solid electrolyte matrix was 163.0 eV, with a difference of 1.0 eV between the two.

[0085] Example 2

[0086] The preparation method of the solid electrolyte in Example 2 is basically the same as that in Example 1, except that the solid electrolyte matrix is ​​changed to Li3InCl6 and the mass ratio of the solid electrolyte matrix Li3InCl6 to the coated source elemental sulfur is changed to 600:1.

[0087] Example 3

[0088] The preparation method of the solid electrolyte in Example 3 is basically the same as that in Example 1, except that the solid electrolyte matrix is ​​changed to Li2ZrCl6 and the mass ratio of the solid electrolyte matrix Li2ZrCl6 to the coated source elemental sulfur is changed to 500:1.

[0089] Example 4

[0090] The preparation method of the solid electrolyte in Example 4 is basically the same as that in Example 1, except that the mass ratio of the source elemental sulfur coated on the solid electrolyte matrix Li3YCl6 is changed to 400:1.

[0091] Example 5

[0092] The preparation method of the solid electrolyte in Example 5 is basically the same as that in Example 1, except that the mass ratio of the source elemental sulfur coated on the solid electrolyte matrix Li3YCl6 is changed to 900:1.

[0093] Example 6

[0094] The preparation method of the solid electrolyte in Example 6 is basically the same as that in Example 1, except that the mass ratio of the source elemental sulfur coated on the solid electrolyte matrix Li3YCl6 is changed to 1000:1.

[0095] Example 7

[0096] The preparation method of the solid electrolyte in Example 7 is basically the same as that in Example 1, except that the mass ratio of the source element sulfur coated on the solid electrolyte matrix Li3YCl6 is changed to 100:1.

[0097] Example 8

[0098] The preparation method of the solid electrolyte in Example 8 is basically the same as that in Example 1, except that the mass ratio of the source elemental sulfur coated on the solid electrolyte matrix Li3YCl6 is changed to 10:1.

[0099] Example 9

[0100] The preparation method of the solid electrolyte in this embodiment includes the following steps:

[0101] 1) Elemental iodine (sublimation temperature 114℃, electronegativity 2.66) was stirred and mixed evenly with the solid electrolyte matrix Li3YCl6 to obtain a mixture; wherein the mass ratio of the solid electrolyte matrix Li3YCl6 to the coated source elemental iodine was 500:1.

[0102] 2) The mixture was heat-treated at 200℃, and after cooling, a solid electrolyte was obtained. The solid electrolyte consisted of a solid electrolyte matrix Li3YCl6 and a coating layer of elemental iodine on the surface of the Li3YCl6 matrix. The coating layer was 15 nm thick, the coating efficiency was 100%, and the ionic conductivity was 0.8 mS / cm. In the XPS spectrum, the I3d5 / 2 binding energy of the II bond in elemental iodine was 620.6 eV, and the I3d5 / 2 binding energy of the IY bond formed between elemental iodine and the solid electrolyte matrix was 618.8 eV, with a difference of 0.8 eV between the two.

[0103] Example 10

[0104] The preparation method of the solid electrolyte in Example 10 includes the following steps:

[0105] 1) Elemental sulfur (sublimation temperature 171℃) is stirred and mixed evenly with solid electrolyte matrix Li3YCl6 to obtain a mixture; wherein the mass ratio of solid electrolyte matrix Li3YCl6 to coated source elemental sulfur is 500:1.

[0106] 2) Add xylene solvent to the mixture, mix well, and dry at 200°C to obtain solid electrolyte.

[0107] Example 11

[0108] The preparation method of the solid electrolyte in Example 11 is basically the same as that in Example 1, except that the mixture is placed in a crucible for heat treatment.

[0109] Comparative Example 1

[0110] The solid electrolyte in Comparative Example 1 was Li3YCl6, which was not coated.

[0111] Comparative Example 2

[0112] The preparation method of the solid electrolyte in Comparative Example 2 is basically the same as that in Example 1, except that the heat treatment temperature is changed to 80°C, which is lower than the sublimation temperature of elemental sulfur.

[0113] Comparative Example 3

[0114] The preparation method of the solid electrolyte in Comparative Example 3 includes the following steps:

[0115] 1) The polymer PI is dissolved in the oily solvent NMP to form a solution, and the concentration of PI in the solution is 1 wt%;

[0116] 2) The halide solid electrolyte Li3YCl6 is added to the above solution to form a solid electrolyte suspension, wherein the solid content of the halide solid electrolyte Li3YCl6 in the solid electrolyte suspension is 65wt%.

[0117] 3) Spray drying is used, and the drying temperature is controlled at 140℃. After drying, polymer-coated halide electrolytes are obtained.

[0118] Comparative Example 4

[0119] The preparation method of the solid electrolyte in Comparative Example 4 includes the following steps:

[0120] 1) Add 1 part by weight of ammonium fluoride to 100 parts by weight of Li3YCl6 halide solid electrolyte, and stir mechanically at 25°C for 0.5 hours to obtain a core-shell halide solid electrolyte precursor;

[0121] 2) The obtained precursor was heat-treated at 220℃ for 6 hours under sealed conditions, with a concentration of 1℃ / min. -1 The ammonium fluoride is cooled to room temperature at a cooling rate, during which it decomposes to generate hydrogen fluoride gas, which reacts with the Li3YCl6 halide solid electrolyte to obtain a core-shell Li3YCl6 halide solid electrolyte with LiF coating.

[0122] Experimental example:

[0123] 1. Thickness of the coating layer: obtained by transmission electron microscopy or high-magnification scanning electron microscopy.

[0124] 2. Electronegativity of inorganic substances: An inherent property of substances, which can be directly looked up in the periodic table.

[0125] 3. Binding energy: obtained by XPS characterization.

[0126] 4. Coating efficiency: The atomic concentration of each element on the sample surface is calculated based on the peak area and elemental correction information obtained from the XPS spectra. Coating efficiency = concentration of coating layer element / (concentration of coating layer element + concentration of each element in the solid electrolyte matrix). Taking Example 1 as an example, coating efficiency = concentration of S element / (concentration of S element + concentration of Li element + concentration of Y element + concentration of Cl element).

[0127] 5. Ionic conductivity and ionic conductivity retention: 200 mg of solid electrolyte was placed in a solid mold and pressed into a tablet using a pressure of 3 tons, maintaining the pressure for 3 minutes. Subsequently, a carbon-coated aluminum foil was attached to each side of the pressed solid electrolyte tablet as a current collector, assembling it into a battery, and external pressure was applied. The test method was AC impedance spectroscopy, with a test frequency of 10 MHz-1 Hz. The ionic conductivity P1 of the solid electrolyte was obtained.

[0128] After exposure at a dew point of 40℃ for 24 hours, the ionic conductivity of the solid electrolyte was tested again, and the ionic conductivity retention rate was P2 / P1.

[0129] 6. Specific capacity and initial coulombic efficiency: Batteries were prepared using the solid electrolytes (after exposure to air) obtained in the examples and comparative examples, specifically including: mixing the solid electrolyte with the ternary cathode material Ni83 at a mass ratio of 3:7 to obtain a cathode composite material; using In alloy as the anode material; weighing a certain amount of solid electrolyte, pouring it into a battery mold, pressing it under a certain pressure to obtain a solid electrolyte layer, and placing the solid electrolyte layer between the cathode sheet formed by the cathode composite material and the anode sheet formed by the anode material to obtain the battery.

[0130] At 25℃, the battery was charged at a constant current rate of 0.1C / 1C to 4.5V, and then charged at a constant voltage rate of 4.5V until the current equals 0.05C. The charging capacity at this point is recorded as the first charge specific capacity. After resting for 5 minutes, the battery was discharged at a constant current rate of 0.1C / 1C to a voltage of 2.5V. The discharge capacity at this point is recorded as the first discharge specific capacity. The first coulombic efficiency is calculated by dividing the resulting discharge specific capacity by the charge specific capacity.

[0131] Figure 1 shows the SEM and EDS images of the solid electrolyte of Embodiment 1 of this application, where a is the SEM image of the solid electrolyte of Embodiment 1 of this application and b is the EDS image of the solid electrolyte of Embodiment 1 of this application.

[0132] As can be seen from Figure 1, in the solid electrolyte of Example 1, elemental sulfur is uniformly coated on the surface of the halide solid electrolyte matrix.

[0133] Figure 2 shows the SEM and EDS images of the solid electrolyte of Comparative Example 2 of this application, where a is the SEM image of the solid electrolyte of Comparative Example 2 of this application and b is the EDS image of the solid electrolyte of Comparative Example 2 of this application.

[0134] As can be seen from Figure 2, in the solid electrolyte of Comparative Example 2, the distribution of elemental sulfur is uneven and it is not coated on the surface of the halide solid electrolyte matrix.

[0135] Figure 3 shows the XPS spectrum of the solid electrolyte of Comparative Example 2 of this application.

[0136] Figure 4 is the XPS energy spectrum of the solid electrolyte of Example 1 of this application.

[0137] As can be seen from Figures 3 and 4, the 2p3 / 2 binding energy of sulfur in the solid electrolyte of Comparative Example 2 is 164.0 eV (corresponding to the SS bond in elemental sulfur), while the 2p3 / 2 binding energy of sulfur in the solid electrolyte of Example 1 is 163.0 eV (corresponding to the SY bond formed by elemental sulfur and halide). The difference between the two is 1.0 eV.

[0138] Table 1

[0139] As shown in Table 1, the solid electrolyte provided in this application, by introducing a coating layer on the surface of the solid electrolyte matrix and using an inorganic material with a sublimation temperature of less than 500°C as the coating material, with a coating rate greater than or equal to 90%, can reduce the interfacial impedance between the solid electrolyte and the electrode material, fill the microscopic defects and pores on the surface of the solid electrolyte matrix; at the same time, it can prevent the solid electrolyte matrix from being directly exposed to the environment, and can also form chemical bonds with certain metal elements in the solid electrolyte matrix, thereby improving the ionic conductivity retention rate and stability of the solid electrolyte. When applied to batteries, it can improve the specific capacity and initial coulombic efficiency of the battery.

[0140] Finally, it should be noted that other embodiments of this application will readily conceive of by those skilled in the art upon consideration of the specification and practice of the application disclosed herein. This application is intended to cover any variations, uses, or adaptations of this application that follow the general principles of this application and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and alterations may be made without departing from its scope. The scope of this application is limited only by the appended claims.

Claims

1. A solid electrolyte, characterized in that, It includes a solid electrolyte matrix and a coating layer present on the surface of the solid electrolyte matrix, the coating layer comprising an inorganic material with a sublimation temperature of less than 500°C; The solid electrolyte has a coating rate of 90% or greater.

2. The solid electrolyte according to claim 1, characterized in that, The thickness of the coating layer is 0.1nm-100nm, preferably 2nm-20nm.

3. The solid electrolyte according to claim 1 or 2, characterized in that, The electronegativity of the bonding elements in the inorganic material is 2.0-2.

8.

4. The solid electrolyte according to any one of claims 1-3, characterized in that, The coating layer comprises elemental sulfur.

5. The solid electrolyte according to any one of claims 1-4, characterized in that, The solid electrolyte matrix includes a halide solid electrolyte.

6. The solid electrolyte according to claim 5, characterized in that, The chemical composition of the halide solid electrolyte is Li a MX b M is selected from at least one of Mg, Al, Ga, In, Sb, Bi, Y, Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Zr, Hf, Cr, Fe, Zn and Cd, and X is selected from at least one of Cl, Br, I and F, 1≤a≤3, 1≤b≤6.

7. The solid electrolyte according to claim 6, characterized in that, The M is selected from at least one of Ga, In, Y, Sc, Ho, Yb, Lu, Zr and Hf; And / or, the X is selected from Cl and / or Br.

8. The solid electrolyte according to any one of claims 1-7, characterized in that, The difference between the binding energy between the elements of the inorganic material and the binding energy between the elements of the inorganic material and the elements of the solid electrolyte matrix is ​​0.1 eV-2.0 eV.

9. The solid electrolyte according to any one of claims 1-8, characterized in that, The solid electrolyte has an ionic conductivity greater than 0.3 mS / cm.

10. A method for preparing a solid electrolyte according to any one of claims 1-9, characterized in that, Includes the following steps: The solid electrolyte is obtained by heat-treating a raw material system comprising a solid electrolyte matrix and a coating source and then cooling it. Wherein, the temperature of the heat treatment is greater than the sublimation temperature of the coating source; The mass ratio of the solid electrolyte matrix to the coating source is (100-1000):

1.

11. The method for preparing a solid electrolyte according to claim 10, characterized in that, The heat treatment is carried out in a closed environment; And / or, the sublimation temperature of the coating source is less than 500°C; And / or, the temperature of the heat treatment is 150℃-500℃.

12. A positive electrode plate, characterized in that, Solid electrolytes include those prepared by any one of claims 1-9 or the method for preparing solid electrolytes according to claim 10 or 11.

13. A battery, characterized in that, This includes the solid electrolyte as described in any one of claims 1-9, the solid electrolyte prepared by the method described in claim 10 or 11, or the positive electrode as described in claim 12.

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