Modified solid-state electrolyte and preparation method thereof, and all-solid-state battery

Abstract

The application provides a modified solid-state electrolyte, a preparation method thereof and a full-solid-state battery. The modified solid-state electrolyte comprises a sulfide solid-state electrolyte and a coating layer coated on the surface of the sulfide solid-state electrolyte, wherein the coating layer is a high-molecular polymer, and the thermal decomposition temperature of the high-molecular polymer is greater than or equal to 50 DEG C. The coating layer on the surface of the modified solid-state electrolyte in the application is a high-molecular polymer, and the high-molecular polymer is decomposed into formaldehyde gas at a temperature greater than or equal to 50 DEG C, so that on the one hand, the stability of the modified solid-state electrolyte in air during transportation and storage can be ensured, and on the other hand, the high-molecular coating layer can be degraded and volatilized by heating during the use of the modified solid-state electrolyte, so that the protective layer is completely removed, and at the same time, the high ionic conductivity of the sulfide solid-state electrolyte itself is retained as much as possible, and further, the comprehensive performance of the sulfide full-solid-state battery is improved.

Description

Technical Field

[0001] This invention relates to the field of all-solid-state battery technology, and more specifically, to a modified solid-state electrolyte and its preparation method, and an all-solid-state battery. Background Technology

[0002] Solid-state batteries have attracted widespread attention due to their advantages such as high safety and high energy density. Sulfide all-solid-state batteries, in particular, have been studied. However, the poor air stability of sulfide solid electrolytes is one of the major problems affecting their commercialization. Therefore, solving this problem has become an important research direction in the field of all-solid-state batteries.

[0003] Existing technologies include coating sulfide solid electrolytes to improve their stability in air. For example, coating an oxide solid electrolyte onto the surface of a sulfide solid electrolyte results in a coated sulfide solid electrolyte, thus addressing the poor water stability of sulfide solid electrolytes. However, oxide solid electrolytes have lower ionic conductivity than sulfide solid electrolytes, therefore coated sulfide solid electrolytes suffer from poor ionic conductivity during use.

[0004] Existing technologies also involve doping sulfide solid electrolytes with certain elements to improve their stability in air. However, doping inevitably reduces the ionic conductivity of the sulfide solid electrolyte, and the stability of the doped sulfide solid electrolyte in air is not ideal. Summary of the Invention

[0005] The main objective of this invention is to provide a modified solid electrolyte and its preparation method, as well as an all-solid-state battery, to solve the problem of poor stability of sulfide all-solid-state batteries in air in the prior art.

[0006] To achieve the above objectives, according to one aspect of the present invention, a modified solid electrolyte is provided, the modified solid electrolyte comprising a sulfide solid electrolyte and a coating layer coated on the surface of the sulfide solid electrolyte, wherein the coating layer is a polymer and the thermal decomposition temperature of the polymer is ≥50°C.

[0007] Furthermore, the aforementioned polymer is polyoxymethylene (POM), preferably with the following structural formula: Where n is 1283 to 5376, and preferably the molecular weight of the polymer is 30452 to 235712 Da.

[0008] Furthermore, the thickness of the aforementioned coating layer is 5.00–100.00 nm, preferably 5.50–20.60 nm.

[0009] Furthermore, the mass ratio of the aforementioned polymer to the sulfide solid electrolyte is 0.5–10:100, and preferably the sulfide solid electrolyte is selected from (1+x)Li₂S·xP₂S₅, Li 6-y PS 5-y X 1+y and Li 11-z M 2-z P 1+z S 12 The sulfide solid electrolyte has any one or more of the following properties: 0 < x < 1, 0 ≤ y ≤ 0.6, 0.5 ≤ z ≤ 1.5, M is selected from any one or more of Ge, Sn, and Si, X is a halogen, preferably selected from any one or more of Cl, Br, and I, and the D50 particle size of the sulfide solid electrolyte is preferably 0.5 to 20 μm.

[0010] According to another aspect of the present invention, a method for preparing the aforementioned modified solid electrolyte is provided, the method comprising: coating a polymer onto the surface of a sulfide solid electrolyte using chemical vapor deposition to obtain a modified solid electrolyte.

[0011] Furthermore, the above preparation method also includes: polymerizing the reaction raw materials including polyoxymethylene precursor and initiator to obtain polyoxymethylene powder; and chemically vapor-depositing the polyoxymethylene powder with a sulfide solid electrolyte to obtain a modified solid electrolyte.

[0012] Furthermore, the aforementioned polyoxymethylene precursor is oligooxymethylene, preferably oligooxymethylene is any one or more of trioxymethylene, tetraoxymethylene, pentaoxymethylene, and hexaoxymethylene; further, the polymerization reaction temperature is preferably 30-80°C, and the polymerization reaction time is preferably 0.5-5 h; even further, the initiator is preferably selected from any one or more of azobisisobutyronitrile, azobisisoheptanenitrile, and boron trifluoride ether.

[0013] Furthermore, the temperature of the above chemical vapor deposition is 150–500°C, and the preferred chemical vapor deposition time is 10–60 min.

[0014] According to another aspect of the present invention, an all-solid-state battery is provided, comprising a positive electrode, a solid electrolyte, and a negative electrode, wherein the solid electrolyte is the aforementioned modified solid electrolyte.

[0015] Furthermore, when the aforementioned all-solid-state battery is in operation, it is heated, preferably at a temperature of 86°C to 200°C.

[0016] By applying the technical solution of this invention, the coating layer on the surface of the modified solid electrolyte of this application is a polymer, and the polymer decomposes into small molecules such as water and carbon dioxide at a temperature of 50°C or higher. This ensures the stability of the electrolyte in air during transportation and storage, and allows the polymer coating layer to degrade and volatilize during use by heating, thereby completely removing the protective layer. At the same time, the high ionic conductivity of the sulfide solid electrolyte itself is preserved as much as possible, further improving the overall performance of the sulfide all-solid-state battery. Attached Figure Description

[0017] The accompanying drawings, which form part of this application, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an undue limitation of the invention. In the drawings:

[0018] Figure 1 A schematic diagram of a polymer-coated sulfide solid electrolyte and its decoating process is shown in Embodiment 1 of the present invention. Detailed Implementation

[0019] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0020] As analyzed in the background section of this application, existing technologies suffer from poor stability of sulfide-based all-solid-state batteries in air. To address this issue, this application provides a modified solid electrolyte, its preparation method, and an all-solid-state battery.

[0021] In a typical embodiment of this application, a modified solid electrolyte is provided, which includes a sulfide solid electrolyte and a coating layer on the surface of the sulfide solid electrolyte, wherein the coating layer is a polymer and the thermal decomposition temperature of the polymer is ≥50°C.

[0022] The modified solid electrolyte of this application has a coating layer made of a polymer, which decomposes into formaldehyde gas at a temperature of 50°C or higher. This ensures the stability of the electrolyte in air during transportation and storage, and allows the polymer coating layer to degrade and volatilize during use by heating, thus completely removing the protective layer. At the same time, the high ionic conductivity of the sulfide solid electrolyte itself is preserved as much as possible, further improving the overall performance of the sulfide all-solid-state battery.

[0023] To better balance the protective effect of the polymer coating on the sulfide solid electrolyte and its thermal decomposability, thereby making it easier to protect the sulfide solid electrolyte while ensuring that the ionic conductivity of the sulfide solid electrolyte itself remains unaffected, the polymer is preferably polyoxymethylene (POM), and the preferred structural formula of POM is [insert structural formula here]. Where n is 1283 to 5376, and preferably the molecular weight of the polymer is 30452 to 235712 Da.

[0024] In one embodiment of this application, the thickness of the coating layer is 5.00 to 100.00 nm, preferably 5.50 to 20.60 nm.

[0025] The thicker the coating layer, the better it is at suppressing the influence of substances such as moisture in the air on the performance of sulfide solid electrolytes. However, since the coating layer of this application itself is detrimental to the ionic conductivity of the sulfide solid electrolyte, the coating layer eventually needs to be removed. Therefore, if the coating layer is too thick, it will increase the workload of removing the coating layer, thereby increasing the cost. Therefore, the preferred coating layer thickness can protect the sulfide solid electrolyte as much as possible while making it easier to remove, thereby maximizing economic benefits.

[0026] The preferred mass ratio of polymer to sulfide solid electrolyte is 0.5 to 10:100. This allows for easier removal of the polymer while maximizing the protective effect of the polymer on the sulfide solid electrolyte.

[0027] High ionic conductivity sulfide solid electrolytes contribute to the development of all-solid-state batteries with superior isoelectric properties. Therefore, the preferred sulfide solid electrolytes are selected from (1+x)Li₂S·xP₂S₅ and Li₂S₅. 6-y PS 5-y X 1+y and Li 11-z M 2- z P 1+z S 12 The solid electrolyte is selected from any one or more of the following, wherein 0 < x < 1, 0 ≤ y ≤ 0.6, 0.5 ≤ z ≤ 1.5, M is selected from any one or more of Ge, Sn, and Si, and X is a halogen, preferably selected from any one or more of Cl, Br, and I. The preferred D50 particle size of the sulfide solid electrolyte is 0.5 to 20 μm. The preferred sulfide solid electrolyte can basically determine the particle size of the modified solid electrolyte, thereby obtaining a solid electrolyte that better meets the needs of practical applications.

[0028] In another typical embodiment of this application, a method for preparing the aforementioned modified solid electrolyte is provided. The method includes: coating a polymer onto the surface of a sulfide solid electrolyte using chemical vapor deposition to obtain the modified solid electrolyte.

[0029] The above method facilitates a simpler and faster way to uniformly coat the surface of a solid electrolyte with a polymer, thereby achieving better protection of the sulfide solid electrolyte by the coating layer.

[0030] In one embodiment, the above preparation method further includes: polymerizing the reaction raw materials including polyoxymethylene precursor and initiator to obtain polyoxymethylene powder; and performing chemical vapor deposition on the polyoxymethylene powder and sulfide solid electrolyte to obtain modified solid electrolyte.

[0031] The above-mentioned reaction raw materials also include a solvent. The polymerization reaction yields a product system including polyoxymethylene (POM) powder. This product system is then filtered to obtain POM powder, which is subsequently coated onto the sulfide solid electrolyte using chemical vapor deposition. The above preparation method is simple, quick, and convenient, and the resulting modified solid electrolyte coating provides better protection for the sulfide solid electrolyte.

[0032] To improve the self-polymerization efficiency and effect of the polyoxymethylene precursor, the polyoxymethylene precursor is preferably an oligooxymethylene, and preferably an oligooxymethylene is any one or more of trioxymethylene, tetraoxymethylene, pentaoxymethylene, and hexaoxymethylene; further, the polymerization reaction temperature is preferably 30-80°C, and the polymerization reaction time is preferably 0.5-5 h; even further, the initiator is preferably selected from any one or more of azobisisobutyronitrile, azobisisoheptanenitrile, and boron trifluoride ether.

[0033] In one embodiment of this application, the temperature of the chemical vapor deposition is 150-500°C, and the chemical vapor deposition time is preferably 10-60 min.

[0034] The temperature and time of the above chemical vapor deposition are conducive to the faster and more uniform deposition of polyoxymethylene powder on the surface of sulfide solid electrolyte, resulting in a denser and more uniform coating layer.

[0035] In another typical embodiment of this application, a solid-state battery is provided, including a positive electrode, a solid-state electrolyte, and a negative electrode, wherein the solid-state electrolyte is the aforementioned modified solid-state electrolyte.

[0036] Solid-state batteries, including the solid electrolyte described in this application, have superior ionic conductivity, and thus superior electrical performance.

[0037] In one embodiment of this application, the all-solid-state battery is heated during normal operation, preferably at a temperature of 86°C to 200°C.

[0038] The above method is beneficial for protecting the all-solid-state battery throughout the entire storage process, and for removing the coating layer within the above heating temperature range while minimizing the impact of heating temperature on the sulfide solid electrolyte and the overall performance of the all-solid-state battery.

[0039] The beneficial effects of this application will be further illustrated below with reference to the embodiments.

[0040] Example 1

[0041] Preparation of sulfide solid electrolyte: [The text abruptly ends here, likely due to an incomplete sentence or missing information.] 5.4 PS 4.4 Cl 1.6 Li₂S, P₂S₅, and LiCl were mixed uniformly in molar ratio and ball-milled at 600 r / min for 12 h. The resulting powder was compacted into sheets at 300 MPa and encapsulated in quartz tubes at 10 Pa pressure. The sheets were then sintered at 520 °C for 2 h. After cooling with the sample, the powder was removed and ground into sulfide solid electrolyte powder. The D50 particle size of the sulfide solid electrolyte was 5 μm. The conductivity of 100 mg of sulfide solid electrolyte powder compacted at 300 MPa was measured to be 7.80 mS / cm.

[0042] Preparation of polyoxymethylene powder: 20g of trioxymethylene was dissolved in 50mL of cyclohexane at 80℃. After the solution cooled to 40℃, 0.25mL of boron trifluoride diethyl ether was added as an initiator. The solution was stirred at 40℃ for 2 hours, and then obtained as polyoxymethylene powder by filtration and washing. Its molecular weight is 53487 Da.

[0043] Polyoxymethylene (POM)-coated sulfide solid electrolyte: 1g of POM powder was placed on the heating stage of the CVD equipment, and 100g of sulfide solid electrolyte powder was placed in the CVD sample chamber. The heating stage was heated to 250℃ and maintained at a constant temperature to allow the POM powder to volatilize onto the sulfide solid electrolyte sample. After the CVD process was carried out for 30 minutes, the equipment was cooled to room temperature to obtain the modified solid electrolyte. The thickness of the POM coating layer was 5nm.

[0044] Coating effect verification: The obtained modified solid electrolyte was exposed to air with 50% humidity for 12 hours. 110 mg of modified solid electrolyte powder was taken and baked in a vacuum oven at 120℃ for 1 hour. The powder was taken out and pressed into a tablet at 300 MPa. The conductivity was measured to be 7.52 mS / cm, which proved the protective effect of the coating layer on the sulfide solid electrolyte and the effect of high temperature removal of the protective layer.

[0045] Example 2

[0046] Preparation of sulfide solid electrolyte: Li₂S, P₂S₅, and LiCl were mixed uniformly in a molar ratio of Li₆PS₅Cl and ball-milled at 500 r / min for 24 h. The resulting powder was compacted into sheets at 300 MPa and sealed in a quartz tube at 10 Pa. The sheets were then sintered at 500 °C for 3 h. After cooling with the sample, the powder was removed and ground into sulfide solid electrolyte powder. The D50 particle size of the sulfide solid electrolyte was 10 μm. The conductivity of 100 mg of sulfide solid electrolyte powder compacted at 300 MPa was measured to be 2.40 mS / cm.

[0047] Preparation of polyoxymethylene powder: 20g of tetraoxymethylene was dissolved in 50mL of cyclohexane at 80℃. When the solution cooled to 40℃, 0.2mL of boron trifluoride ether was added as an initiator. The solution was stirred at 40℃ for 3h, and then obtained by filtration and washing, with a molecular weight of 146732 Da.

[0048] Polyoxymethylene (POM)-coated sulfide solid electrolyte: 1g of POM powder was placed on the heating stage of the CVD equipment, and 100g of sulfide solid electrolyte powder was placed in the CVD sample chamber. The heating stage was heated to 300℃ and kept constant to allow the POM powder to volatilize onto the sulfide solid electrolyte sample. After the CVD process was carried out for 30 minutes, the equipment was cooled to room temperature to obtain the modified solid electrolyte. The thickness of the POM coating layer was 15nm.

[0049] Coating effect verification: The obtained modified solid electrolyte was exposed to air with 50% humidity for 12 hours. 110 mg of modified solid electrolyte powder was taken and baked in a vacuum oven at 135℃ for 1 hour. The powder was taken out and pressed into tablets at 300 MPa. The conductivity was measured to be 2.20 mS / cm.

[0050] Example 3

[0051] Preparation of sulfide solid electrolyte: [The text abruptly ends here, likely due to an incomplete sentence or missing information.] 10 GeP2S 12 Li₂S, P₂S₅, and GeS₂ were mixed uniformly in molar ratio and ball-milled at 400 r / min for 100 h. The resulting powder was compacted into sheets at 300 MPa and encapsulated in quartz tubes at 10 Pa pressure. The sheets were then sintered at 230 °C for 4 h. After cooling with the sample, the powder was removed and ground into sulfide solid electrolyte powder. The D50 particle size of the sulfide solid electrolyte was 8 μm. The conductivity of 100 mg of sulfide solid electrolyte powder compacted at 300 MPa was measured to be 10.80 mS / cm.

[0052] Preparation of polyoxymethylene powder: 20g of paraoxymethylene was dissolved in 50mL of cyclohexane at 80℃. After the solution cooled to 50℃, 0.3mL of azobisisobutyronitrile was added as an initiator. The solution was stirred at 50℃ for 1.5h, and then obtained by filtration and washing, with a molecular weight of 243671 Da.

[0053] Polyoxymethylene (POM)-coated sulfide solid electrolyte: 1g of POM powder was placed on the heating stage of the CVD equipment, and 100g of sulfide solid electrolyte powder was placed in the CVD sample chamber. The heating stage was heated to 380℃ and maintained at a constant temperature to allow the POM powder to volatilize onto the sulfide solid electrolyte sample. After the CVD process was carried out for 30 minutes, the equipment was cooled to room temperature to obtain the modified solid electrolyte with a POM coating thickness of 20nm.

[0054] Coating effect verification: The obtained modified solid electrolyte was exposed to air with 50% humidity for 12 hours. 110 mg of modified solid electrolyte powder was taken and baked in a vacuum oven at 180℃ for 1 hour. The powder was taken out and pressed into tablets at 300 MPa. The conductivity was measured to be 10.50 mS / cm.

[0055] Example 4

[0056] The difference from Example 1 is that the D50 particle size of the sulfide solid electrolyte was changed to 18 μm and the thickness of the polyoxymethylene coating layer was changed to 5.50 nm, and the modified solid electrolyte was finally obtained.

[0057] Example 5

[0058] The difference from Example 1 is that the D50 particle size of the sulfide solid electrolyte was changed to 20 μm and the thickness of the polyoxymethylene coating layer was changed to 20.60 nm, and the modified solid electrolyte was finally obtained.

[0059] Example 6

[0060] The difference from Example 1 is that the D50 particle size of the sulfide solid electrolyte was changed to 30 μm and the thickness of the polyoxymethylene coating layer was changed to 5.00 nm, and the modified solid electrolyte was finally obtained.

[0061] Example 7

[0062] The difference from Example 1 is that the D50 particle size of the sulfide solid electrolyte was changed to 35 μm and the thickness of the polyoxymethylene coating layer was changed to 100.00 nm, and the modified solid electrolyte was finally obtained.

[0063] Example 8

[0064] The difference from Example 1 lies in the preparation of the polyoxymethylene powder: 20g of trioxymethylene was dissolved in 50mL of cyclohexane at 80°C. When the solution cooled to 40°C, 0.2mL of boron trifluoride diethyl ether was added as an initiator. The solution was stirred at 40°C for 1.5h, and then obtained by filtration and washing, resulting in polyoxymethylene powder with a molecular weight of 34567 Da, ultimately yielding the modified solid electrolyte.

[0065] Coating effect verification: The obtained modified solid electrolyte was exposed to air with 50% humidity for 12 hours. 110 mg of modified solid electrolyte powder was taken and baked in a vacuum oven at 100℃ for 1 hour. The powder was taken out and pressed into a tablet at 300 MPa. The conductivity was measured to be 7.52 mS / cm, which proved the protective effect of the coating layer on the sulfide solid electrolyte and the effect of high temperature removal of the protective layer.

[0066] Example 9

[0067] The difference from Example 1 lies in the preparation of the polyoxymethylene powder: 30g of trioxymethylene was dissolved in 50mL of cyclohexane at 80°C. When the solution cooled to 40°C, 0.5mL of boron trifluoride ether was added as an initiator. The solution was stirred at 40°C for 4 hours, and then obtained by filtration and washing, resulting in polyoxymethylene powder with a molecular weight of 235712 Da, ultimately yielding the modified solid electrolyte.

[0068] Coating effect verification: The obtained modified solid electrolyte was exposed to air with 50% humidity for 12 hours. 110 mg of modified solid electrolyte powder was taken and baked in a vacuum oven at 150℃ for 1 hour. The powder was taken out and pressed into tablets at 300 MPa. The conductivity was measured to be 7.58 mS / cm, which proved the protective effect of the coating layer on the sulfide solid electrolyte and the effect of high temperature removal of the protective layer.

[0069] Example 10

[0070] The difference from Example 1 is that the polyoxymethylene (POM)-coated sulfide solid electrolyte is used: 0.5g of POM powder is placed on the heating stage of the CVD equipment, and 100g of sulfide solid electrolyte powder is placed in the CVD sample chamber. The heating stage is heated to 250°C and maintained at a constant temperature to allow the POM powder to evaporate onto the sulfide solid electrolyte sample. After this CVD process is carried out for 30 minutes, the equipment is cooled to room temperature to obtain the modified solid electrolyte. The thickness of the POM coating layer is 13nm.

[0071] Example 11

[0072] The difference from Example 1 is that the polyoxymethylene (POM)-coated sulfide solid electrolyte is used: 10g of POM powder is placed on the heating stage of the CVD equipment, and 100g of sulfide solid electrolyte powder is placed in the CVD sample chamber. The heating stage is heated to 250°C and maintained at a constant temperature to allow the POM powder to evaporate onto the sulfide solid electrolyte sample. After this CVD process is carried out for 30 minutes, the equipment is cooled to room temperature to obtain the modified solid electrolyte. The thickness of the POM coating layer is 200nm.

[0073] Example 12

[0074] The difference from Example 1 lies in the use of polyoxymethylene (POM) coated with a sulfide solid electrolyte: 12g of POM powder was placed on the heating stage of the CVD equipment, and 100g of sulfide solid electrolyte powder was placed in the CVD sample chamber. The heating stage was heated to 250°C and maintained at a constant temperature to allow the POM powder to evaporate onto the sulfide solid electrolyte sample. After this CVD process was carried out for 30 minutes, the equipment was cooled to room temperature to obtain the modified solid electrolyte. The thickness of the POM coating layer was 250nm.

[0075] Example 13

[0076] The difference from Example 1 lies in the preparation of the polyoxymethylene powder: 20g of trioxymethylene was dissolved in 50mL of cyclohexane at 80°C. When the solution cooled to 40°C, 0.25mL of boron trifluoride ether was added as an initiator. The solution was stirred at 80°C for 0.5h, and then obtained by filtration and washing, resulting in polyoxymethylene powder with a molecular weight of 18347 Da, ultimately yielding the modified solid electrolyte.

[0077] Example 14

[0078] The difference from Example 1 is that the polyoxymethylene (POM)-coated sulfide solid electrolyte is used: 1g of POM powder is placed on the heating stage of the CVD equipment, and 100g of sulfide solid electrolyte powder is placed in the CVD sample chamber. The heating stage is heated to 150°C and maintained at a constant temperature to allow the POM powder to evaporate onto the sulfide solid electrolyte sample. After this CVD process is carried out for 30 minutes, the equipment is cooled to room temperature to obtain the modified solid electrolyte. The thickness of the POM coating layer is 24nm.

[0079] Example 15

[0080] The difference from Example 1 is that the polyoxymethylene (POM)-coated sulfide solid electrolyte is used: 1g of POM powder is placed on the heating stage of the CVD equipment, and 100g of sulfide solid electrolyte powder is placed in the CVD sample chamber. The heating stage is heated to 500°C and maintained at a constant temperature to allow the POM powder to evaporate onto the sulfide solid electrolyte sample. After this CVD process is carried out for 30 minutes, the equipment is cooled to room temperature to obtain the modified solid electrolyte. The thickness of the POM coating layer is 30nm.

[0081] Example 16

[0082] The difference from Example 1 is that the polyoxymethylene (POM)-coated sulfide solid electrolyte is used: 1g of POM powder is placed on the heating stage of the CVD equipment, and 100g of sulfide solid electrolyte powder is placed in the CVD sample chamber. The heating stage is heated to 100°C and kept at a constant temperature to allow the POM powder to evaporate onto the sulfide solid electrolyte sample. After this CVD process is carried out for 30 minutes, the equipment is cooled to room temperature to obtain the modified solid electrolyte. The thickness of the POM coating layer is 20nm.

[0083] Comparative Example 1

[0084] The difference from Example 1 is that the sulfide solid electrolyte (with a conductivity of 7.80 mS / cm) is not coated with polyoxymethylene.

[0085] Coating effect verification: The sulfide solid electrolyte was exposed to air with 50% humidity for 12 hours. 110 mg of the sulfide solid electrolyte was baked in a vacuum oven at 120℃ for 1 hour. The powder was then pressed into tablets at 300 MPa and the conductivity was measured to be 0.20 mS / cm.

[0086] The conductivity of the sulfide solid electrolyte before coating (denoted as A) and the conductivity of the modified solid electrolyte after decoating (denoted as B) in Examples 1 to 16 above are listed in Table 1.

[0087] Table 1

[0088]

[0089]

[0090] As can be seen from the above description, the embodiments of the present invention achieve the following technical effects:

[0091] The modified solid electrolyte of this application has a coating layer made of a polymer, which decomposes into small molecules such as water and carbon dioxide at a temperature of 50°C or higher. This ensures the stability of the electrolyte in air during transportation and storage, and allows the polymer coating layer to degrade and volatilize during use by heating, thus completely removing the protective layer. At the same time, the high ionic conductivity of the sulfide solid electrolyte itself is preserved as much as possible, further improving the overall performance of the sulfide all-solid-state battery.

[0092] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A modified solid electrolyte, characterized in that, The modified solid electrolyte includes a sulfide solid electrolyte and a coating layer on the surface of the sulfide solid electrolyte, wherein the coating layer is a polymer, and the thermal decomposition temperature of the polymer is ≥50℃; the molecular weight of the polymer is 30452~235712 Da. The polymer includes polyoxymethylene (POM), and the structural formula of POM is as follows: , where n is 1283~5376; The thickness of the coating layer is 5.00~100.00 nm; The mass ratio of the polymer to the sulfide solid electrolyte is 0.5~10:100; The preparation method of the modified solid electrolyte includes: A modified solid electrolyte was obtained by coating a polymer onto the surface of a sulfide solid electrolyte using chemical vapor deposition.

2. The modified solid electrolyte according to claim 1, characterized in that, The thickness of the coating layer is 5.50~20.60 nm.

3. The modified solid electrolyte according to claim 1 or 2, characterized in that, The sulfide solid electrolyte is selected from (1+x)Li₂S·xP₂S₅, Li₆- y PS5 y X 1+y and Li 11 - z M2- z P 1+z S 12 Any one or more of the following, wherein 0 < x < 1, 0 ≤ y ≤ 0.6, 0.5 ≤ z ≤ 1.5, M is selected from any one or more of Ge, Sn, and Si, and X is a halogen.

4. The modified solid electrolyte according to claim 3, characterized in that, X is selected from any one or more of Cl, Br, and I.

5. The modified solid electrolyte according to claim 3, characterized in that, The D50 particle size of the sulfide solid electrolyte is 0.5~20 μm.

6. A method for preparing the modified solid electrolyte according to any one of claims 1 to 5, characterized in that, The preparation method includes: A modified solid electrolyte was obtained by coating a polymer onto the surface of a sulfide solid electrolyte using chemical vapor deposition.

7. The preparation method according to claim 6, characterized in that, The preparation method further includes: Polymerization of reactants including polyoxymethylene precursor and initiator yields polyoxymethylene powder. The modified solid electrolyte is obtained by chemical vapor deposition of the polyoxymethylene powder and the sulfide solid electrolyte.

8. The preparation method according to claim 7, characterized in that, The polyoxymethylene precursor is oligooxymethylene, which is any one or more of trioxymethylene, tetraoxymethylene, pentaoxymethylene, and hexaoxymethylene.

9. The preparation method according to claim 7, characterized in that, The polymerization reaction is carried out at a temperature of 30~80℃.

10. The preparation method according to claim 9, characterized in that, The polymerization reaction takes 0.5 to 5 hours.

11. The preparation method according to claim 7, characterized in that, The initiator is selected from any one or more of azobisisobutyronitrile, azobisisoheptanenitrile, and boron trifluoride ether.

12. The preparation method according to claim 7, characterized in that, The temperature for chemical vapor deposition is 150~500℃.

13. The preparation method according to claim 12, characterized in that, The chemical vapor deposition time is 10~60 min.

14. An all-solid-state battery, comprising a positive electrode, a solid electrolyte, and a negative electrode, characterized in that, The solid electrolyte is the modified solid electrolyte according to any one of claims 1 to 5.

15. The all-solid-state battery according to claim 14, characterized in that, The all-solid-state battery is heated during normal operation.

16. The all-solid-state battery according to claim 15, characterized in that, The heating temperature is 86℃~200℃.

Images