Coated sulfide solid electrolyte, preparation method thereof, solid-state battery and electronic device

Abstract

The invention relates to the field of solid-state batteries, in particular to a coated sulfide solid-state electrolyte and a preparation method thereof, a solid-state battery and an electronic device. The coated sulfide electrolyte is composed of a core electrolyte A and a shell electrolyte B, the core electrolyte A is a Li6-aPS5-aCl1 + a-bXb type crystalline electrolyte, a is greater than or equal to 0 and less than or equal to 0.8, b is greater than or equal to 0 and less than or equal to 0.6, and X is at least one of F, Br and I elements; the shell electrolyte B is Li7P2S8I1-cYc type glass-ceramic electrolyte, c is more than or equal to 0 and less than or equal to 0.8, and Y is at least one of Cl and Br elements. According to the coated sulfide solid electrolyte disclosed by the invention, the crystalline electrolyte and the glass-ceramic electrolyte are combined, and the crystalline electrolyte is taken as an inner core, so that the overall conductivity of the electrolyte is improved, the lithium ion transfer rate is improved, and the rate capability of a battery is further improved; in addition, the coated sulfide solid electrolyte has the characteristics of low Young modulus and high conductivity, and an all-solid-state battery assembled by the coated sulfide solid electrolyte still has excellent energy density and cycle performance even under low external pressure.

Description

Technical Field

[0001] This invention relates to the field of solid-state batteries, specifically to a coated sulfide solid electrolyte and its preparation method, as well as solid-state batteries and electronic devices. Background Technology

[0002] With the widespread adoption of electric vehicles, lithium-ion battery technology has made rapid progress. However, the energy density achievable with graphite anodes in traditional lithium batteries is limited, and using lithium metal anodes is considered the ultimate solution to improve lithium battery energy density. However, when using lithium metal anodes, problems such as uneven lithium stripping / deposition and lithium dendrite formation occur during battery cycling. Lithium dendrites may even penetrate the separator, leading to short circuits and serious safety issues. Solid-state lithium batteries are expected to suppress lithium dendrite growth, improve battery energy density, and enhance battery safety. Among the many types of solid electrolytes, sulfide solid electrolytes have been extensively studied due to their high ionic conductivity comparable to organic electrolytes and good compatibility with commercial cathode materials. Summary of the Invention

[0003] To address the aforementioned problems, one objective of this invention is to provide a coated sulfide solid electrolyte, wherein the coated sulfide electrolyte comprises a core electrolyte A and a shell electrolyte B, wherein the core electrolyte A is Li 6- a PS 5-a Cl 1+a-b X b The electrolyte is a crystalline electrolyte, wherein 0 ≤ a ≤ 0.8, 0 ≤ b ≤ 0.6, and X is at least one of F, Br, and I; the outer electrolyte B is Li7P2S8I. 1-c Y c A type of glass-ceramic electrolyte, wherein 0≤c≤0.8, and Y is at least one of Cl and Br elements.

[0004] In some specific embodiments, the mass ratio of electrolyte A to electrolyte B in the coated sulfide electrolyte is (1~5):1; preferably, the mass ratio of electrolyte A to electrolyte B in the coated sulfide electrolyte is (3~4):1.

[0005] The second aspect of this application provides a method for preparing a coated sulfide electrolyte as described in the first aspect, wherein the core electrolyte A is obtained by weighing LiCl, P2S5, Li2S, and LiX, mechanically mixing them, sintering them, obtaining coarse electrolyte A powder, and then refining the coarse electrolyte A powder to obtain core electrolyte A.

[0006] In some specific embodiments, the mechanical mixing includes mixing using one or more of a pulverizer, ball mill, and sand mill.

[0007] In some specific embodiments, the mixing time of the mechanical mixing is 2-12 hours; preferably, the mixing time of the mechanical mixing is 4-8 hours.

[0008] In some specific embodiments, the sintering temperature is 500~600℃, preferably 550℃.

[0009] In some specific embodiments, the sintering time is 10 to 30 hours, preferably 12 to 18 hours.

[0010] In some specific embodiments, the refining process includes at least one of ball milling, sand milling, and air jet milling.

[0011] In some specific embodiments, the equipment used for the refining process includes at least one of a ball mill, a sand mill, and an air jet mill.

[0012] In some specific embodiments, the coated sulfide electrolyte is obtained as follows: the raw materials of electrolyte B include LiI, P2S5, Li2S, and LiY. After weighing the raw materials of electrolyte B, electrolyte A and solvent are added and mixed. After mixing, the mixture is vacuum dried and sintered again to obtain a coated sulfide electrolyte in which electrolyte B coats electrolyte A.

[0013] In some specific embodiments, the drying conditions after mixing and vacuum drying are as follows: drying at 120-140°C for 4-8 hours. During the vacuum drying stage, the solvent and complexing agent are removed together.

[0014] In some specific embodiments, the re-sintering temperature is 150~250℃, and in some further embodiments, the re-sintering temperature can be 180~210℃; in some specific embodiments, the re-sintering time is 1-6h; and in some further embodiments, the re-sintering time is 2-3h.

[0015] In some specific embodiments, the addition of electrolyte A solvent for mixing further includes: adding electrolyte A, solvent and complexing agent for mixing.

[0016] In some specific embodiments, the complexing agent is at least one of tetramethylethylenediamine, hexamethylenetetramine, and tetrahydroxyethylethylenediamine.

[0017] In some specific embodiments, the mass ratio of the complexing agent to the electrolyte B is (0~0.05):1; the preparation of the coated electrolyte can also be completed when the amount of complexing agent is 0. When a complexing agent is added to the formulation, the complexing agent will be adsorbed on the surface of electrolyte A, with electrolyte A acting as a nucleation center, and inducing the electrolyte B raw material to react on the surface of electrolyte A, forming a coated electrolyte B layer, thereby forming a coated core-shell electrolyte.

[0018] In some specific embodiments, the solvent is at least one selected from n-heptane, n-octane, dodecane, cyclohexane, toluene, xylene, and hexyl octanoate.

[0019] In some specific embodiments, the mass ratio of the solvent to the electrolyte A is (1~3):1; preferably, the mass ratio of the solvent to the electrolyte A is (1.5~2):1.

[0020] In some specific embodiments, the mass ratio of the solvent to the sum of electrolyte A and electrolyte B is (1~3):1.

[0021] In some specific embodiments, the median particle size of the core electrolyte A obtained after the coarse powder of electrolyte A is refined is 1-5 μm.

[0022] In some specific embodiments, the median particle size of the core electrolyte A obtained after the coarse powder of electrolyte A is refined is 2-3 μm.

[0023] In some specific embodiments, the mixing time for adding electrolyte A and the solvent is 6 to 24 hours. Preferably, the mixing time for adding electrolyte A and the solvent is 12 to 20 hours.

[0024] A third aspect of this application provides a solid-state battery, comprising a positive electrode, a solid electrolyte, and a negative electrode, wherein at least one of the positive electrode, the solid electrolyte, and the negative electrode comprises the coated sulfide solid electrolyte described in the first aspect or is prepared by the method of the second aspect.

[0025] A fourth aspect of this application provides an electronic device comprising a solid-state battery as described in the third aspect. Detailed Implementation

[0026] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art based on this application are within the scope of protection of this application.

[0027] It should be noted that, in the specific embodiments of this application, a pouch lithium-ion battery is used as an example of a solid-state battery to explain this application, but the solid-state battery of this application is not limited to pouch lithium-ion batteries.

[0028] Crystalline sulfide electrolytes typically require high-temperature sintering to form high-strength electrolytes approaching 10. -2 The conductivity is mS / cm, but the sintered crystalline electrolyte is composed of numerous grains and has a very high Young's modulus. Young's modulus is a physical quantity that measures the "stiffness" or "hardness" of a material. A high Young's modulus means that the material is very hard and not easily deformed. A low Young's modulus means that the material is relatively soft, elastic and easily deformed. For the battery to work properly, ions must shuttle smoothly back and forth between the positive electrode, electrolyte and negative electrode, which requires a tight and seamless contact interface.

[0029] Electrolytes with high Young's modulus tend to have poor interfacial contact with electrodes, meaning there are voids between the electrolyte particles, resulting in a small effective contact area and thus a large interfacial impedance, which is detrimental to lithium-ion transport at the interface. Furthermore, due to the numerous grain boundaries formed by the many tiny grains in crystalline sulfide electrolytes, even after very high-pressure isostatic pressing, large voids remain in the electrolyte layer, which are difficult to address through other processes. These issues ultimately require sulfide-based all-solid-state batteries to withstand enormous external pressures during use, often exceeding 50 or even 100 MPa, which is unfavorable for practical applications of solid-state batteries.

[0030] Glass-ceramic electrolytes, due to their inherently low Young's modulus and high plasticity, can effectively solve the aforementioned problems. However, the presence of a large amount of amorphous phase in glass-ceramic electrolytes often results in a conductivity typically around 10. -4 ~10 -3 The low conductivity (mS / cm) results in poor rate performance of batteries assembled from it, falling far short of industry requirements for electrolyte conductivity.

[0031] Therefore, there is an urgent need to find an innovative solution to address the above problems in order to ensure that solid-state batteries still have practical application value under low external pressure.

[0032] To address the aforementioned problems, one objective of this invention is to provide a coated sulfide solid electrolyte, wherein the coated sulfide electrolyte comprises a core electrolyte A and a shell electrolyte B, wherein the core electrolyte A is Li 6- a PS 5-a Cl 1+a-b X bThe electrolyte is a crystalline electrolyte, wherein 0 ≤ a ≤ 0.8, 0 ≤ b ≤ 0.6, and X is at least one of F, Br, and I; the outer electrolyte B is Li7P2S8I. 1-c Y c A type of glass-ceramic electrolyte, wherein 0≤c≤0.8, and Y is at least one of Cl and Br elements.

[0033] The coated sulfide solid electrolyte of this application combines crystalline electrolyte and glass-ceramic electrolyte, with the crystalline electrolyte as the core, to improve the overall conductivity of the electrolyte, increase the lithium-ion transfer rate, and thus improve the rate performance of the battery. In addition, the coated sulfide solid electrolyte of this application has the characteristics of low Young's modulus and high conductivity, and the all-solid-state battery assembled with it still has excellent energy density and cycle performance even under low external pressure.

[0034] In some specific embodiments, for example, a can be a value within the range of 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, or any two of these values; b can be a value within the range of 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, or any two of these values; c can be a value within the range of 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, or any two of these values.

[0035] In some specific embodiments, the mass ratio of electrolyte A to electrolyte B in the coated sulfide electrolyte is (1~5):1; preferably, the mass ratio of electrolyte A to electrolyte B in the coated sulfide electrolyte is (3~4):1.

[0036] By adjusting the mass ratio of electrolyte A and electrolyte B to within the range of (1~5):1, the coated sulfide solid electrolyte of this application achieves a balance between Young's modulus and conductivity. The assembled all-solid-state battery still has excellent energy density and cycle performance even under low external pressure.

[0037] In some specific embodiments, the mass ratio of electrolyte A to electrolyte B in the coated sulfide electrolyte is 1:1, 2:1, 3:1, 4:1, 5:1, or any value within the range of any two of these values.

[0038] The second aspect of this application provides a method for preparing a coated sulfide electrolyte as described in the first aspect, wherein the core electrolyte A is obtained by weighing LiCl, P2S5, Li2S, and LiX, mechanically mixing them, sintering them, obtaining coarse electrolyte A powder, and then refining the coarse electrolyte A powder to obtain core electrolyte A.

[0039] In some specific embodiments, the mechanical mixing includes mixing using one or more of a pulverizer, ball mill, and sand mill.

[0040] In some specific embodiments, the mixing time of the mechanical mixing is 2-12 hours; preferably, the mixing time of the mechanical mixing is 4-8 hours.

[0041] In some specific embodiments, the mixing time of the mechanical mixing can be 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h or a value within the range of any two of these values.

[0042] In some specific embodiments, the sintering temperature is 500~600℃, preferably 550℃.

[0043] In some specific embodiments, the sintering temperature can be 500°C, 510°C, 520°C, 530°C, 540°C, 550°C, 560°C, 570°C, 580°C, 590°C, or 600°C, or a value within a range of any two of these values.

[0044] In some specific embodiments, the sintering time is 10 to 30 hours, preferably 12 to 18 hours.

[0045] In some specific embodiments, the sintering time can be 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, 26h, 28h, 30h, or a value within a range of any two of these values.

[0046] In some specific embodiments, the refining process includes at least one of ball milling, sand milling, and air jet milling.

[0047] In some specific embodiments, the equipment used for the refining process includes at least one of a ball mill, a sand mill, and an air jet mill.

[0048] In some specific embodiments, the coated sulfide electrolyte is obtained as follows: the raw materials of electrolyte B include LiI, P2S5, Li2S, and LiY. After weighing the raw materials of electrolyte B, electrolyte A and solvent are added and mixed. After mixing, the mixture is vacuum dried and sintered again to obtain a coated sulfide electrolyte in which electrolyte B coats electrolyte A.

[0049] In some specific embodiments, the drying conditions after mixing and vacuum drying are 120°C to 140°C for 4 to 8 hours. During the vacuum drying stage, the solvent and complexing agent are removed together.

[0050] In some specific embodiments, the drying temperature for vacuum drying after mixing is 120℃~140℃; in some specific embodiments, the drying temperature can be 120℃, 125℃, 130℃, 135℃, 140℃ or a value within any two of these values.

[0051] This application avoids excessively high drying temperatures that could lead to element volatilization, material phase transformation or decomposition, and material surface oxidation. It also avoids excessively low drying temperatures that could result in incomplete evaporation of internally trapped water and solvents, which could lead to reactions between water and solvents and Li metal or the cathode during subsequent processing, resulting in increased interfacial impedance. Furthermore, this application avoids energy waste caused by excessively long drying times and potential particle agglomeration, thus avoiding the need for redispersing in subsequent processing (such as ball milling and molding), which increases process complexity.

[0052] The sintering temperature of this application ensures that the goal of forming a core crystalline electrolyte and a shell glass-ceramic electrolyte is achieved.

[0053] In some specific embodiments, the drying time for vacuum drying after mixing is 4h to 8h; the drying time can be 4h, 5h, 6h, 7h, 8h or any value within the range of any two of these values.

[0054] In some specific embodiments, the re-sintering temperature is 150℃~250℃; in some further embodiments, the re-sintering temperature can be 180℃~210℃; in some specific embodiments, the re-sintering time is 1h-6h; in some further embodiments, the re-sintering time is 2h-3h.

[0055] In some specific embodiments, the re-sintering temperature can be 150°C, 170°C, 190°C, 210°C, 230°C, 250°C, or a value within the range of any two of these values.

[0056] In some specific embodiments, the re-sintering time can be 1h, 2h, 3h, 4h, 5h, 6h, or a value within the range of any two of these values.

[0057] In some specific embodiments, the addition of electrolyte A solvent for mixing further includes: adding electrolyte A, solvent and complexing agent for mixing.

[0058] In some specific embodiments, the complexing agent is at least one of tetramethylethylenediamine, hexamethylenetetramine, and tetrahydroxyethylethylenediamine. The complexing agents used in this application possess multidentate coordination ability, high complexing stability, and are readily soluble in organic solvents. They can connect metal ions into chain-like or network-like complexes through bridging coordination. During subsequent heat treatment, the complexing agent decomposes, achieving uniform coating of the glass-ceramic electrolyte on the surface of the crystalline electrolyte.

[0059] In some specific embodiments, the mass ratio of the complexing agent to the electrolyte B is (0~0.05):1; the preparation of the coated electrolyte can also be completed when the amount of complexing agent is 0. When a complexing agent is added to the formulation, the complexing agent will be adsorbed on the surface of electrolyte A, with electrolyte A acting as a nucleation center, and inducing the electrolyte B raw material to react on the surface of electrolyte A, forming a coated electrolyte B layer, thereby forming a coated core-shell electrolyte.

[0060] In some specific embodiments, the mass ratio of the complexing agent to the electrolyte B is 0:1, 0.01:1, 0.02:1, 0.03:1, 0.04:1, or 0.05:1, or a value within the range of any two of these values.

[0061] In some specific embodiments, the solvent is at least one selected from n-heptane, n-octane, dodecane, cyclohexane, toluene, xylene, and hexyl octanoate. The solvent used in this application is a weakly polar solvent, characterized by low polarity and no chemical reaction with sulfide electrolytes, thus being compatible with sulfide systems and improving the success rate of electrolyte synthesis.

[0062] In some specific embodiments, the mass ratio of the solvent to the electrolyte A is (1~3):1; preferably, the mass ratio of the solvent to the electrolyte A is (1.5~2):1. The solvent dosage used in this application allows for complete dissolution of the precursor, thorough and uniform reaction, suitable grain size, and few grain boundary defects, resulting in a finished material with characteristics such as no obvious agglomeration, no solvent residue, and high conductivity.

[0063] In some specific embodiments, the mass ratio of the solvent to the electrolyte A can be 1:1, 2:1, 3:1, or a value within a range of any two of these values.

[0064] In some specific embodiments, the median particle size of the core electrolyte A obtained after the coarse powder of electrolyte A is refined is 1-5 μm.

[0065] In some specific embodiments, the median particle size of the core electrolyte A obtained after the coarse powder of electrolyte A is refined can be 1 μm, 2 μm, 3 μm, 4 μm, 5 μm or a value within the range of any two of these values.

[0066] In some specific embodiments, the median particle size of the core electrolyte A obtained after the coarse powder of electrolyte A is refined is 2-3 μm.

[0067] In some specific embodiments, the mixing time for adding electrolyte A and the solvent is 6 to 24 hours. Preferably, the mixing time for adding electrolyte A and the solvent is 12 to 20 hours.

[0068] In some specific embodiments, the mixing time for adding electrolyte A and solvent can be 6h, 8h, 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, or a value within any range of two of these values.

[0069] A third aspect of this application provides a solid-state battery, comprising a positive electrode, a solid electrolyte, and a negative electrode, wherein at least one of the positive electrode, the solid electrolyte, and the negative electrode comprises the coated sulfide solid electrolyte described in the first aspect or is prepared by the method of the second aspect.

[0070] In some specific embodiments, the negative electrode includes at least one of a lithium metal negative electrode, a silicon-carbon negative electrode, and a silicon negative electrode.

[0071] In some specific embodiments, the positive electrode includes at least one of lithium nickel cobalt manganese oxide-based positive electrode, lithium iron phosphate-based positive electrode, lithium manganese iron phosphate-based positive electrode, and lithium-rich manganese-based positive electrode.

[0072] A fourth aspect of this application provides an electronic device comprising a solid-state battery as described in the third aspect.

[0073] The electronic device described in this application is not particularly limited and can be any electronic device known in the prior art. In some embodiments, the electronic device may include, but is not limited to, laptops, pen input computers, mobile computers, e-book players, portable telephones, portable fax machines, portable copiers, portable printers, stereo headphones, video recorders, LCD TVs, portable cleaners, portable CD players, mini CDs, transceivers, electronic notebooks, calculators, memory cards, portable recorders, radios, backup power supplies, motors, automobiles, motorcycles, electric bicycles, bicycles, lighting fixtures, toys, game consoles, clocks, power tools, flashlights, cameras, large household batteries or lithium-ion capacitors, etc.

[0074] Example The following examples and comparative examples illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0075] The testing methods and equipment used in the embodiments and comparative examples of this application are as follows: Ionic conductivity testing: The coated electrolyte membrane was scraped into powder. Using stainless steel (SS) as the ion-blocking electrodes on both sides, the sulfide electrolyte membrane powder was sandwiched between them to assemble a molded battery with a sandwich structure. A pressure of 500 MPa was applied during assembly. The assembled test battery was subjected to AC impedance testing at room temperature using an electrochemical workstation (Zennium Pro) with a frequency range of 1 MHz–0.1 Hz and a voltage amplitude of 10 mV. The ionic conductivity was calculated using the following formula: ; Where σ is the ionic conductivity R is the resistance (Ω). A is the thickness (cm), and A is the area (cm²). 2 ).

[0076] Young's modulus test: Electrolyte powder was hot-pressed to obtain a sample with a diameter of about 10 mm and a height of about 5 mm. The Young's modulus of the electrolyte powder at room temperature was measured using standard procedure 15 for ultrasonic velocity measurement.

[0077] Rate performance test: The completed small soft-pack battery is placed in the fixture, and a pressure of 3MPa or 30MPa is applied to the fixture. Then, the battery cell with the fixture is placed in a 25℃ oven for charge and discharge tests at different rates of 0.1, 0.5C, 1C and 2C, and the discharge capacity at different rates is recorded.

[0078] Cyclic performance testing: The fabricated small pouch battery is placed in a fixture, and a pressure of 3MPa or 30MPa is applied to the fixture. Then, the battery cell with the fixture is placed in a 25℃ oven for 300 cycles of 0.5C charge-discharge testing. The discharge specific capacity D1 of the first cycle and the discharge specific capacity D2 of the 300th cycle are recorded. 300 Calculate the capacity retention rate after 300 cycles. Use the following formula to calculate the capacity retention rate: ; The reagents used in the embodiments and comparative examples of this application are as follows: LiCl, P2S5, Li2S, LiBr, LiI, hexamethylenetetramine, and n-heptane were all purchased from Shanghai Aladdin Biochemical Technology Co., Ltd.

[0079] Example 1 1. Preparation of electrolytes: (1) LiCl, P2S5, Li2S, and LiBr were mechanically mixed in stoichiometric ratios (where a=0.6, b=0.6), sintered at 550℃ for 12 h, and refined into 3 μm Li 5.4 PS 4.4 ClBr 0.6 Type electrolyte.

[0080] (2) Weigh LiBr, P2S5, Li2S, and LiI according to their stoichiometric ratio (where c=0.7), mix them, and the total mass is 1 part by weight. Add 3 parts by weight of Li... 5.4 PS 4.4 ClBr 0.6 A mixture of a type electrolyte, 0.02 parts by weight of hexamethylenetetramine, and 6 parts by weight of n-heptane was liquid-phase mixed for 12 h, dried under vacuum at 120 °C for 4 h, and then sintered at 220 °C for 4 h to obtain Li7P2S8I. 0.3 Br 0.7 Encapsulated Li 5.4 PS 5.4 ClBr 0.6 Type electrolyte.

[0081] 2. Preparation of negative electrode sheet: Using a mixture of graphite and silicon carbon materials with a mass ratio of 70:30 as the active material, the negative electrode active material, electrolyte powder, binder (PVDF), and conductive agent (Super P) are thoroughly mixed in a solvent according to a certain weight ratio to form a uniform negative electrode slurry. This slurry is coated on nickel-plated copper foil, dried at 85°C, and then cut and slit to obtain the negative electrode sheet with a size of 2.3cm*2.3cm.

[0082] 3. Preparation of positive electrode sheet: NCM811 positive electrode material, conductive agent (Super P), binder (PVDF) and electrolyte powder are thoroughly mixed in a solvent system at a certain weight ratio to obtain a positive electrode slurry. The obtained positive electrode slurry is coated on the positive electrode current collector aluminum foil, dried and cut to obtain a positive electrode sheet with a size of 2cm*2cm.

[0083] 4. Preparation of electrolyte membrane: The electrolyte powder and binder prepared above are thoroughly mixed in a solvent system at a certain mass ratio to obtain an electrolyte slurry. The electrolyte slurry is coated on a PET substrate, dried, and then the electrolyte membrane is peeled off from the substrate and cut to obtain the desired electrolyte membrane.

[0084] 4. Battery Assembly: Ni and Al tabs are welded onto the negative and positive electrodes respectively. The positive electrode, electrolyte membrane, and negative electrode are then stacked in sequence, with the electrolyte membrane acting as a separator between the positive and negative electrodes, thus forming the electrode assembly. The electrode assembly is placed in an aluminum-plastic film packaging bag and undergoes vacuum sealing, isostatic pressing, formation, and capacity testing to obtain a soft-pack lithium-ion battery.

[0085] Example 2 Electrolyte preparation: (1): LiCl, P2S5, Li2S, and LiBr were mechanically mixed in stoichiometric ratios (where a=0.6, b=0), sintered at 520℃ for 14 h, and refined into 5 μm Li. 5.4 PS 4.4 Cl 1.6 Type electrolyte.

[0086] (2): Weigh LiBr, P2S5, Li2S, and LiI according to their stoichiometric ratio (where c=0.5), mix them, and the total mass is 1 part by weight. Add 4 parts by weight of Li... 5.4 PS 4.4 Cl 1.6 A mixture of a type electrolyte, 0.02 parts by weight of tetramethylethylenediamine, 3 parts by weight of n-heptane, and 2 parts by weight of cyclohexane was prepared in the liquid phase for 8 hours, dried under vacuum at 140°C for 3 hours, and then sintered at 200°C for 3 hours to obtain Li7P2S8I. 0.5 Br 0.5 Encapsulated Li 5.4 PS 5.4 Cl 1.6 Type electrolyte.

[0087] The remaining methods for powdering, preparation of negative electrode, preparation of positive electrode, preparation of electrolyte membrane, and battery assembly are the same as in Example 1.

[0088] Example 3 Electrolyte preparation: (1): LiCl, P2S5, Li2S, and LiBr were mechanically mixed in stoichiometric ratios (where a=0.3, b=0.3), sintered at 500℃ for 16 h, and refined into 2 μm Li. 5.4 PS 4.4 Cl 1.3 Br 0.3 Type electrolyte.

[0089] (2): Weigh LiBr, P2S5, Li2S, and LiI according to their stoichiometric ratio (where c=0), and mix them to obtain a total mass of 1 part by weight. Add 5 parts by weight of Li... 5.4 PS 4.4 Cl1.3 Br 0.3 A mixture of a type electrolyte, 0.02 parts by weight of tetramethylethylenediamine, 0.02 parts by weight of tetrahydroxyethylethylenediamine, and 6 parts by weight of toluene was prepared in the liquid phase for 8 hours, dried under vacuum at 130°C for 2 hours, and then sintered at 190°C for 3 hours to obtain Li7P2S8I-coated Li. 5.4 PS 5.4 Cl 1.3 Br 0.3 Type electrolyte.

[0090] The remaining methods for powdering, preparation of negative electrode, preparation of positive electrode, preparation of electrolyte membrane, and battery assembly are the same as in Example 1.

[0091] Example 4 Electrolyte preparation: (1): LiCl, P2S5, Li2S, and LiBr were mechanically mixed in stoichiometric ratios (where a=0.8, b=0.6), sintered at 600℃ for 18h, and refined into 4µm Li 5.2 PS 4.2 Cl 1.2 Br 0.6 Type electrolyte.

[0092] (2): Weigh LiBr, P2S5, Li2S, and LiI according to their stoichiometric ratio (where c=0.5), mix them, and the total mass is 1 part by weight. Add 3 parts by weight of Li... 5.2 PS 4.2 Cl 1.2 Br 0.6 A mixture of a type electrolyte, 0.04 parts by weight of hexamethylenetetramine, and 6 parts by weight of xylene was liquid-phase mixed for 24 h, dried under vacuum at 120 °C for 8 h, and then sintered at 210 °C for 6 h to obtain Li7P2S8I. 0.5 Br 0.5 Encapsulated Li 5.2 PS 4.2 Cl 1.2 Br 0.6 Type electrolyte.

[0093] The remaining methods for powdering, preparation of negative electrode, preparation of positive electrode, preparation of electrolyte membrane, and battery assembly are the same as in Example 1.

[0094] Example 5 Electrolyte preparation: (1): LiCl, P2S5, Li2S, and LiBr were mechanically mixed in stoichiometric ratios (where a=0.6, b=0.6), sintered at 500℃ for 12 h, and refined into 3 μm Li. 5.4PS 4.4 ClBr 0.6 Type electrolyte.

[0095] (2): Weigh LiBr, P2S5, Li2S, and LiI according to their stoichiometric ratio (where c=0.8), mix them, and the total mass is 1 part by weight. Add 2 parts by weight of Li... 5.4 PS 4.4 ClBr 0.6 A mixture of a type electrolyte, 0.02 parts by weight of hexamethylenetetramine, 2 parts by weight of hexyl octanoate, and 1 part by weight of n-octane was liquid-phase mixed for 12 h, dried under vacuum at 140 °C for 4 h, and then sintered at 250 °C for 3 h to obtain Li7P2S8I. 0.2 Br 0.8 Encapsulated Li 5.4 PS 5.4 ClBr 0.6 Type electrolyte.

[0096] The remaining methods for powdering, preparation of negative electrode, preparation of positive electrode, preparation of electrolyte membrane, and battery assembly are the same as in Example 1.

[0097] Example 6 Electrolyte preparation: (1): LiCl, P2S5, Li2S, and LiBr were mechanically mixed in stoichiometric ratios (where a=0.6, b=0.6), sintered at 550℃ for 12 h, and refined into 3 μm Li. 5.4 PS 4.4 ClBr 0.6 Type electrolyte.

[0098] (2): Weigh LiCl, P2S5, Li2S, and LiI according to their stoichiometric ratio (where c=0.7), mix them, and the total mass is 1 part by weight. Add 3 parts by weight of Li... 5.4 PS 4.4 ClBr 0.6 The electrolyte, 0 parts by weight of complexing agent, and 6 parts by weight of n-heptane were mixed in the liquid phase for 12 h, dried under vacuum at 120 °C for 4 h, and then sintered at 220 °C for 4 h to obtain Li7P2S8I. 0.3 Br 0.7 Encapsulated Li 5.4 PS 5.4 ClBr 0.6 Type electrolyte.

[0099] The remaining methods for powdering, preparation of negative electrode, preparation of positive electrode, preparation of electrolyte membrane, and battery assembly are the same as in Example 1.

[0100] Comparative Example 1 Electrolyte preparation: LiCl, P₂S₅, Li₂S, and LiBr were mechanically mixed in stoichiometric ratios (where a = 0.6, b = 0.6), sintered at 550℃ for 12 h, and refined into 3 μm Li₂. 5.4 PS 4.4 ClBr 0.6 Type electrolyte.

[0101] The remaining methods for powdering, preparation of negative electrode, preparation of positive electrode, preparation of electrolyte membrane, and battery assembly are the same as in Example 1.

[0102] Comparative Example 2 1. Preparation of electrolytes: LiCl, P₂S₅, Li₂S, and LiBr were mechanically mixed in stoichiometric ratios (where a = 0.6, b = 0), sintered at 520℃ for 14 h, and refined into 5 μm Li₂. 5.4 PS 4.4 Cl 1.6 Type electrolyte.

[0103] The remaining methods for powdering, preparation of negative electrode, preparation of positive electrode, preparation of electrolyte membrane, and battery assembly are the same as in Example 1.

[0104] Comparative Example 3 Electrolyte preparation: LiBr, P₂S₅, Li₂S, and LiI were weighed according to their stoichiometric ratio (where c = 0.7), resulting in a total mass of 1 part by weight. This mixture was then liquid-phase-mixed with 2 parts by weight of n-heptane for 12 hours, dried under vacuum at 120°C for 4 hours, and finally sintered at 220°C for 4 hours to obtain Li₇P₂S₈I. 0.3 Br 0.7 Electrolytes.

[0105] The remaining methods for powdering, preparation of negative electrode, preparation of positive electrode, preparation of electrolyte membrane, and battery assembly are the same as in Example 1.

[0106] Comparative Example 4 Electrolyte preparation: LiBr, P2S5, Li2S, and LiI were weighed according to their stoichiometric ratio (where c=0), with a total mass of 1 part by weight. This mixture was then liquid-phase-mixed with 2 parts by weight of n-heptane for 12 hours, dried under vacuum at 120°C for 4 hours, and finally sintered at 220°C for 4 hours to obtain the Li7P2S8I electrolyte.

[0107] The remaining methods for powdering, preparation of negative electrode, preparation of positive electrode, preparation of electrolyte membrane, and battery assembly are the same as in Example 1.

[0108] Comparative Example 5 Electrolyte preparation: (1): LiCl, P2S5, Li2S, and LiBr were mechanically mixed in stoichiometric ratios (where a=0.6, b=0.6), sintered at 550℃ for 12 h, and refined into 3 μm Li. 5.4 PS 4.4 ClBr 0.6 Type electrolyte.

[0109] (2): Weigh P2S5 and Li2S at a stoichiometric ratio of 2:8, mix them, and the total mass is 1 part by weight. Add 3 parts by weight of Li... 5.4 PS 4.4 ClBr 0.6 A mixture of a type electrolyte, 0 parts by weight of a complexing agent, and 6 parts by weight of n-heptane was liquid-phase mixed for 12 h, dried under vacuum at 120 °C for 4 h, and then plasma-sintered at 200 °C / 40 MPa for 10 min to obtain (glassy) Li8P2S7-coated (crystalline) Li. 5.4 PS 5.4 ClBr 0.6 Type electrolyte.

[0110] The remaining methods for powdering, preparation of negative electrode, preparation of positive electrode, preparation of electrolyte membrane, and battery assembly are the same as in Example 1.

[0111] Comparative Example 6 Electrolyte preparation: (1): P2S5 and Li2S were weighed at a stoichiometric ratio of 2:8, mechanically mixed, and plasma sintered at 200℃ / 40MPa for 10 min to obtain Li8P2S7 type electrolyte.

[0112] (2): Weigh LiCl, P2S5, Li2S, and LiI according to their stoichiometric ratio (where c=0.7), mix them, and the total mass is 1 part by weight. Add 3 parts by weight of Li7P3S... 11 A mixture of a type electrolyte, 0 parts by weight of a complexing agent, and 6 parts by weight of n-heptane was carried out in the liquid phase for 12 hours, dried under vacuum at 120°C for 4 hours, and then sintered at 220°C for 4 hours to obtain (crystalline) Li7P2S8I. 0.3 Br 0.7 Coated (glassy) Li8P2S7 type electrolyte.

[0113] The remaining methods for powdering, preparation of negative electrode, preparation of positive electrode, preparation of electrolyte membrane, and battery assembly are the same as in Example 1.

[0114] Comparative Example 7 Electrolyte preparation: Li 5.4 PS 4.4 ClBr 0.6 The electrolyte has a weight ratio of 7 parts, and the rest is the same as in Example 1.

[0115] The remaining methods for powdering, preparation of negative electrode, preparation of positive electrode, preparation of electrolyte membrane, and battery assembly are the same as in Example 1.

[0116] Comparative Example 8 1. Preparation of electrolytes: 0.06 parts by weight of hexamethylenetetramine was used as the solvent, and the rest was the same as in Example 1.

[0117] The powdering, preparation of the negative electrode, preparation of the positive electrode, preparation of the electrolyte membrane, and battery assembly methods are the same as in Example 1.

[0118] Comparative Example 9 Electrolyte preparation: 14 parts by weight of n-heptane were used as the solvent, and the rest was the same as in Example 1.

[0119] The remaining methods for powdering, preparation of negative electrode, preparation of positive electrode, preparation of electrolyte membrane, and battery assembly are the same as in Example 1.

[0120] Comparative Example 10 Electrolyte preparation: Two parts by weight of n-heptane were used as the solvent, and everything else was the same as in Example 1.

[0121] The remaining methods for powdering, preparation of negative electrode, preparation of positive electrode, preparation of electrolyte membrane, and battery assembly are the same as in Example 1.

[0122] Table 1

[0123] Table 2

[0124] Regarding the coated sulfide electrolytes prepared in Examples 1-6, compared with the uncoated crystalline sulfide electrolytes of Comparative Examples 1-2 and the pure glass-ceramic sulfide electrolytes of Comparative Examples 3-4, as shown in Table 2, the Young's modulus of the coated sulfide electrolytes of the present invention is significantly lower than that of the uncoated sulfide electrolytes of Comparative Examples 1-2, while the ionic conductivity is significantly higher than that of the pure glass-ceramic electrolytes of Comparative Examples 3-4. A comparison of the electrical performance test results reveals that, because the coated sulfide electrolytes of the present invention simultaneously possess both low Young's modulus and high conductivity, the soft packs prepared using the coated sulfide electrolytes of the present invention exhibit significantly better rate capability and cycle test results under low pressure than the uncoated sulfide electrolytes of Comparative Examples 1-2, and also significantly better than the pure glass-ceramic sulfide electrolytes of Comparative Examples 3-4.

[0125] Comparative Example 5 used a glassy sulfide electrolyte to coat the crystalline electrolyte. Although the Young's modulus was significantly reduced, the poor ion-conducting ability of the glassy sulfide electrolyte affected the coated sulfide electrolyte, making it difficult to achieve a high level of ionic conductivity, thus impacting rate performance and cycle performance. The performance comparison between Examples 1-9 and Comparative Example 5 shows that coating the crystalline electrolyte with a glass-ceramic electrolyte can simultaneously achieve superior ionic conductivity and a lower Young's modulus, significantly improving the rate performance and cycle performance of the battery under low pressure.

[0126] Comparative Example 6 uses a glass-ceramic electrolyte to coat a glass electrolyte. Although this method can obtain a sulfide electrolyte with a lower Young's modulus, its ionic conductivity is significantly reduced, which seriously affects its electrical performance.

[0127] Comparative Example 7 used 7 parts electrolyte A and 1 part electrolyte B for coating experiments. The excessive proportion of electrolyte A resulted in poor coating performance. Therefore, although the coated sulfide electrolyte obtained in Comparative Example 7 had high conductivity, its Young's modulus remained high, leading to poor discharge capacity and capacity retention during low-pressure rate testing (3 MPa) and cycle testing. In contrast, the sulfide electrolyte preparation process of this invention uses a suitable ratio, ultimately achieving superior rate performance and cycle performance under low pressure.

[0128] Comparative Example 8 used too much complexing agent during coating. Excessive complexing agent coated the surface of the sulfide electrolyte, blocking the ion transport channels and resulting in low ionic conductivity, which affected its rate capability and cycling performance.

[0129] In Comparative Examples 9-10, when ceramic-glass sulfide electrolytes were used to coat crystalline electrolytes, the formulations showed both excessive and insufficient solvent. Both of these conditions resulted in poor coating effects, and the resulting coated sulfide electrolytes exhibited high Young's modulus, ultimately leading to unsatisfactory rate and cycle performance under low pressure.

[0130] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A coated sulfide electrolyte, characterized in that, The coated sulfide electrolyte consists of a core electrolyte A and a shell electrolyte B, wherein the core electrolyte A is Li 6-a PS 5-a Cl 1+a-b X b A crystalline electrolyte, wherein 0 ≤ a ≤ 0.8, 0 ≤ b ≤ 0.6, and X is at least one of the elements F, Br, and I; The outer electrolyte B is Li7P2S8I. 1-c Y c A type of glass-ceramic electrolyte, wherein 0≤c≤0.8, and Y is at least one of Cl and Br elements.

2. The coated sulfide electrolyte as described in claim 1, characterized in that, The mass ratio of the core electrolyte A to the outer shell electrolyte B in the coated sulfide electrolyte is (1~5):

1.

3. A method for preparing a coated sulfide electrolyte as described in any one of claims 1 to 2, characterized in that, The core electrolyte A is obtained as follows: LiCl, P2S5, Li2S, and LiX are weighed, mechanically mixed, and sintered to obtain coarse electrolyte A powder. After refining the coarse electrolyte A powder, the core electrolyte A is obtained.

4. The method as described in claim 3, characterized in that, The coated sulfide electrolyte is obtained as follows: the raw materials of the electrolyte B include LiI, P2S5, Li2S, and LiY. After weighing the raw materials of the outer shell electrolyte B, they are added to the core electrolyte A and a solvent for mixing. After mixing, the mixture is vacuum dried and sintered again to obtain a coated sulfide electrolyte in which the outer shell electrolyte B coats the core electrolyte A.

5. The method as described in claim 4, characterized in that, The addition of the core electrolyte A and the solvent for mixing further includes: adding electrolyte A, solvent and complexing agent for mixing; The complexing agent is at least one of tetramethylethylenediamine, hexamethylenetetramine, and tetrahydroxyethylethylenediamine.

6. The method as described in claim 4, characterized in that, The mass ratio of the complexing agent to the electrolyte B is (0~0.05):

1.

7. The method as described in claim 4, characterized in that, The solvent is at least one of n-heptane, n-octane, dodecane, cyclohexane, toluene, xylene, and hexyl octanoate.

8. The method as described in claim 4, characterized in that, The mass ratio of the solvent to the sum of the core electrolyte A and the outer shell electrolyte B is (1~3):

1.

9. A solid-state battery, characterized in that, It includes a positive electrode, a solid electrolyte, and a negative electrode, wherein at least one of the positive electrode, the solid electrolyte, and the negative electrode comprises a coated sulfide solid electrolyte as described in any one of claims 12 or a coated sulfide solid electrolyte prepared by any one of the preparation methods in claims 38.

10. An electronic device, characterized in that, The electronic device includes the solid-state battery as described in claim 9.

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