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

Abstract

The present application relates to the field of solid-state batteries, and in particular, to a kind of solid-state electrolyte material and its preparation method and application.The solid-state electrolyte material includes core and the coating layer of coating in the core surface: wherein, the core includes: sulfide electrolyte;The coating layer includes: halide electrolyte;The chemical formula of the halide electrolyte is: LiTaCl5M 1 / n n‑ M is selected from one or more of Cl, F, I, Br or O, and n is 1 or 2.The solid-state electrolyte material has high ionic conductivity and oxidation potential, and the density value is not much different from that of sulfide electrolyte, which is used to prepare all-solid-state secondary batteries, and can improve the capacity of positive active material, battery energy density, rate and cycle performance.

Description

Technical Field

[0001] This invention relates to the field of solid-state batteries, and more specifically, to a solid electrolyte material, its preparation method, and its application. Background Technology

[0002] Since Sony introduced lithium-ion batteries in 1991, they have been widely used in various portable electronic products (such as laptops, mobile phones, and digital cameras) and electric vehicles. However, recent frequent safety incidents involving new energy vehicles are mainly due to the fact that traditional lithium-ion batteries use flammable organic solvents as electrolytes, posing significant safety hazards that cannot be completely resolved using conventional improvement methods. In contrast, solid-state lithium-ion batteries using solid-state electrolytes offer greater safety advantages. Using solid-state electrolytes can not only fundamentally solve the safety problems of lithium-ion batteries but also significantly simplify manufacturing and packaging processes, improving battery energy density, reliability, and design freedom. Among various new battery systems, solid-state batteries are the next-generation technology closest to industrialization, a consensus reached by both industry and the scientific community. Therefore, strong requirements are placed on the ionic conductivity and high potential stability (>4V) of solid-state electrolytes.

[0003] In inorganic electrolyte materials, the mainstream electrolyte systems are currently divided into three main categories: oxide, sulfide, and halide systems. Oxide electrolytes have high oxidation potentials and are stable for high-voltage ternary cathode materials, but their ionic conductivity is low, and they are rigid and have poor ductility, resulting in high contact resistance with the cathode material and poor battery performance. Sulfide electrolytes typically have high ionic conductivity, some comparable to that of conventional liquid electrolytes, and they have good ductility and low density (approximately 1.9 g / cm³), allowing for relatively dense physical contact with both cathode and anode materials. However, their oxidation potential is low, and when the voltage is >3V, they are prone to decomposition and side reactions, severely affecting battery performance and energy density improvement. For example, Li-type sulfide electrolytes... 7-x P 6-x SCl x Taking the electrolyte system as an example, as the chlorine content increases, its ionic conductivity can increase from 5 mS / cm to 12 mS / cm. However, its own stability and its stability to the positive and negative electrodes gradually deteriorate, and it is prone to side reactions, resulting in poor battery performance. In contrast, halides such as Li3InCl6 and LiTaCl6 are a class of recently popular solid electrolyte materials, especially the glassy LiTaCl5M. 1 / n n-The electrolyte system (M=Cl, F and O, etc.) has good stability for high-voltage cathode materials, an oxidation potential of up to 4.39V, and high ionic conductivity (up to ≈10mS / cm). However, its density is relatively high (≈3.5g / cm³). Under the same formulation conditions, its volume is relatively small compared to the cathode, making it difficult to mix evenly. Consequently, it cannot form a relatively dense physical contact with the cathode material, which seriously affects the battery's rate performance and energy density.

[0004] In view of this, the present invention is hereby proposed. Summary of the Invention

[0005] To address the chemical and electrochemical instability of sulfide electrolyte materials in all-solid-state secondary batteries, improve the capacity utilization of positive electrode active materials, battery energy density, rate capability, and cycle performance, and realize the commercial application value of all-solid-state secondary batteries, this invention provides a solid electrolyte material, its preparation method, and its application.

[0006] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0007] One aspect of the present invention relates to a solid electrolyte material, comprising a core and a coating layer covering the surface of the core:

[0008] The core comprises a sulfide electrolyte; the coating layer comprises a halide electrolyte.

[0009] The chemical formula of the halide electrolyte is: LiTaCl5M 1 / n n- M is selected from one or more of Cl, F, I, Br or O, and n is 1 or 2.

[0010] The solid electrolyte material described above has high ionic conductivity and oxidation potential, and its density value is not much different from that of sulfide electrolytes. When used to prepare all-solid-state secondary batteries, it can improve the capacity utilization of the positive electrode active material, battery energy density, rate capability, and cycle performance.

[0011] Another aspect of the present invention relates to a method for preparing the aforementioned solid electrolyte material, comprising the following steps:

[0012] (a) After adding the halide electrolyte suspension to the sulfide electrolyte suspension, the first reaction and the second reaction are carried out to obtain the first precursor;

[0013] (b) The first precursor is dried and heat-treated.

[0014] The method for preparing the solid electrolyte material is simple, easy to operate, does not rely on complex processes and equipment, has low cost, and the prepared solid electrolyte material has high ionic conductivity and oxidation potential.

[0015] Another aspect of the present invention relates to a lithium secondary battery, comprising the solid electrolyte material described above or a solid electrolyte material prepared by the method for preparing the solid electrolyte material described above;

[0016] Preferably, the lithium secondary battery includes: a semi-solid lithium secondary battery or an all-solid lithium secondary battery.

[0017] The lithium secondary battery described above has high energy density and relatively stable performance.

[0018] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0019] (1) The solid electrolyte material provided by the present invention has high ionic conductivity and oxidation potential, and its density value is not much different from that of sulfide electrolyte. A halide electrolyte coating layer is coated on the surface of the sulfide electrolyte core. By utilizing the high stability and high ionic conductivity of halide electrolyte for high voltage cathode material, the target electrolyte can achieve the goal of maintaining high ionic conductivity while achieving higher oxidation potential, which greatly improves the stability of the target electrolyte for high voltage cathode. At the same time, by utilizing the low density and good ductility of sulfide electrolyte, the density of the target electrolyte can be effectively controlled to maintain an appropriate level, and its volume ratio with cathode material can be increased under the same formulation conditions, thereby improving the uniformity of its mixing with cathode and ensuring sufficient contact between it and cathode material.

[0020] (2) The method for preparing solid electrolyte materials provided by the present invention is simple, easy to operate, does not depend on complex processes and equipment, has low cost, and the prepared solid electrolyte materials have high ionic conductivity and oxidation potential. Attached Figure Description

[0021] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 XRD pattern of solid electrolyte material provided by the present invention;

[0023] Figure 2 XRD pattern of another solid electrolyte material provided by the present invention. Detailed Implementation

[0024] The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0025] One aspect of the present invention relates to a solid electrolyte material, comprising a core and a coating layer covering the surface of the core:

[0026] The core comprises a sulfide electrolyte; the coating layer comprises a halide electrolyte.

[0027] The chemical formula of the halide electrolyte is: LiTaCl5M 1 / n n- M is selected from one or more of Cl, F, I, Br or O, and n is 1 or 2.

[0028] The aforementioned solid electrolyte material involves modifying and coating the surface of a sulfide electrolyte with a certain amount of glassy halide electrolyte. This allows the solid electrolyte material to possess both high ionic conductivity and high oxidation potential, solving the problems of instability and susceptibility to side reactions of sulfide solid electrolytes at high-potential cathodes in all-solid-state secondary batteries. This effectively improves the battery's energy density, rate capability, and cycle performance. Simultaneously, the larger proportion of the core sulfide electrolyte helps maintain a lower density value for the target electrolyte, resulting in a larger volume ratio with the cathode under the same formulation conditions. This facilitates more uniform mixing and forms a denser physical contact with the cathode material, ensuring optimal battery performance.

[0029] A suitable amount of glassy halide electrolyte is uniformly coated on the surface of sulfide electrolyte particles of silver-germanium sulfide. The good stability of halide electrolyte to high-voltage cathode materials is used to solve the problems of low oxidation potential of sulfide electrolyte and serious side reactions when in direct contact with cathode materials. The high ionic conductivity of both is used to ensure that the ionic conductivity of the target electrolyte is at a high level. Using silver-germanium sulfide electrolyte with a small density value as the core material can make the target electrolyte have a larger volume ratio with the cathode under the same formulation conditions, making it easier to mix evenly and form dense contact.

[0030] In summary, the target electrolyte can achieve high ionic conductivity (≥8 mS / cm), high oxidation potential (≥4.3 V), and a density value (1.9–2.5 g / cm³) comparable to that of sulfide electrolytes. 3 This effectively solves the problems of chemical and electrochemical instability and poor physical contact of sulfide electrolyte materials in all-solid-state secondary batteries, ensuring higher capacity utilization of positive electrode active materials, higher energy density of batteries, and more stable performance.

[0031] By utilizing the characteristics of low density, high conductivity, and good ductility of sulfide electrolytes and the high stability of glassy halide electrolytes to high-voltage cathodes, a suitable layer of glassy halide electrolyte is uniformly coated on the surface of the sulfide electrolyte. This achieves a target electrolyte with high ionic conductivity and high oxidation potential, while also having a low density. This improves its chemical and electrochemical stability on the cathode side, ensuring higher capacity utilization of the cathode active material, higher energy density of the battery, and more stable performance.

[0032] Glass-phase halide electrolytes exhibit high ionic conductivity and oxidation potential. Currently, commonly used halide electrolytes have an ionic conductivity of 1–2 mS / cm, such as LiTaCl5M. 1 / n n- Its ionic conductivity can reach up to 10.95 mS / cm, comparable to that of core sulfide electrolytes. This high ionic conductivity is beneficial for improving the battery's rate performance. LiTaCl5M 1 / n n- Its oxidation potential can reach 4.39V, making it more stable for high-nickel cathodes and thus beneficial for improving battery energy density. In addition, glass-phase, i.e., amorphous halide electrolytes are softer than commonly used crystalline halide electrolytes, which greatly improves their contact with the cathode, reduces negative reactions, and helps improve the battery's long-cycle performance.

[0033] Preferably, the mass ratio of the coating layer to the core is (0.001~0.1):1 (e.g., 0.001:1, 0.003:1, 0.005:1, 0.008:1, 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, 0.06:1, 0.07:1, 0.08:1, 0.09:1 or 0.1:1).

[0034] Preferably, the mass ratio of the coating layer to the core is (0.005~0.05):1.

[0035] Preferably, the halide electrolyte, M is selected as F, and its chemical formula is LiTaCl5F.

[0036] Preferably, the particle size of the solid electrolyte material is ≤60μm (e.g., 0.1μm, 1μm, 5μm, 10μm, 15μm, 20μm, 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm or 60μm).

[0037] Preferably, the chemical formula of the sulfide electrolyte is Li. 7-x PS 6-x N x Wherein, N is selected from one or more of Cl, Br, F or I, and 0.1≤x≤5.9.

[0038] Preferably, the sulfide electrolyte has N selected as Cl, x=1, and its chemical formula is Li6PS5Cl.

[0039] Another aspect of the present invention relates to a method for preparing the aforementioned solid electrolyte material, comprising the following steps:

[0040] (a) After adding the halide electrolyte suspension to the sulfide electrolyte suspension, the first reaction and the second reaction are carried out to obtain the first precursor;

[0041] (b) The first precursor is dried and heat-treated.

[0042] The method for preparing the solid electrolyte material is simple, easy to operate, does not rely on complex processes and equipment, has low cost, and the prepared solid electrolyte material has high ionic conductivity and oxidation potential.

[0043] The preparation method of the solid electrolyte material adopts liquid phase coating. Compared with dry ball milling, liquid phase coating is easier to mix evenly and form a uniform suspension to achieve uniform coating; it is more efficient, without the need for intermediate pauses for manual scraping; it is more conducive to using existing equipment or easier to develop special equipment, and it is more conducive to achieving large-scale production.

[0044] Preferably, the temperature of the first reaction is 50~80℃ (e.g., 50℃, 55℃, 60℃, 65℃, 70℃, 75℃ or 80℃). The first reaction process is mainly a process of uniform coating. Providing a certain temperature in this process is more conducive to uniform coating and improving coating efficiency. If the temperature is too low, the reaction time needs to be extended, which will affect the coating efficiency; if the temperature is too high, the solvent will evaporate and be lost during the reaction process, which will affect the coating effect.

[0045] Preferably, the reaction time is 2 to 6 hours (e.g., 2 hours, 3 hours, 4 hours, 5 hours or 6 hours).

[0046] Preferably, the first reaction is carried out under stirring conditions, and the stirring speed is 50~400 rpm / min (e.g. 50 rpm / min, 100 rpm / min, 150 rpm / min, 200 rpm / min, 250 rpm / min, 300 rpm / min, 350 rpm / min or 400 rpm / min).

[0047] Preferably, the temperature of the second reaction is 100~200℃ (e.g., 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃, or 200℃). This temperature range corresponds to the boiling point range of the solvent used: if the temperature is too low, the solvent evaporates slowly, increasing the reaction time; if the temperature is too high, the solvent evaporates quickly, which has a certain impact on the performance of the electrolyte.

[0048] Preferably, the second reaction time is 4 to 8 hours (e.g., 4 hours, 5 hours, 7 hours or 8 hours).

[0049] Preferably, the second reaction is carried out under stirring conditions, and the stirring speed is 50~400 rpm / min (e.g. 50 rpm / min, 100 rpm / min, 150 rpm / min, 200 rpm / min, 250 rpm / min, 300 rpm / min, 350 rpm / min or 400 rpm / min).

[0050] Preferably, the drying method includes freeze-drying. Compared with conventional drying methods, freeze-drying is more efficient, leaves less solvent residue, and has better electrolyte performance.

[0051] Preferably, the freeze-drying temperature is -100 to -20°C (e.g., -100°C, -90°C, -80°C, -70°C, -60°C, -50°C, -40°C, -30°C, or -20°C).

[0052] Preferably, the vacuum degree of the freeze-drying is -95 to -60 Pa (e.g., -95 Pa, -90 Pa, -85 Pa, -80 Pa, -75 Pa, -70 Pa, -65 Pa or -60 Pa).

[0053] Preferably, the freeze-drying time is 6 to 12 hours (e.g., 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours or 12 hours).

[0054] Preferably, the heat treatment temperature is 100~200℃ (e.g., 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃ or 200℃).

[0055] Preferably, the heating rate of the heat treatment is 1~2℃ / min.

[0056] Preferably, the heat treatment time is 1 to 4 hours (e.g., 1 hour, 2 hours, 3 hours or 4 hours).

[0057] Preferably, the sulfide electrolyte in the sulfide electrolyte suspension has a particle size of 30-80 μm (e.g., 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, or 80 μm). As the core material for coating, the sulfide electrolyte needs to have a larger particle size than the coating material, while also maintaining high ionic conductivity (which decreases with decreasing particle size). A particle size of 30-80 μm is preferred. If the particle size is too small, the electrolyte's ionic conductivity will be low and uniform coating will be difficult to achieve; if the particle size is too large, it will affect the contact between the electrolyte material and the cathode material, thus affecting the cathode's performance.

[0058] Preferably, the particle size of the halide electrolyte in the halide electrolyte suspension is 0.05~1μm (e.g., 0.05μm, 0.1μm, 0.3μm, 0.5μm, 0.7μm, 0.9μm, or 1μm). As a coating material, the halide electrolyte needs to have a smaller particle size than the core material to form a relatively dense coating while maintaining a certain ionic conductivity; a particle size of 0.05~1μm is preferred. If the particle size is too small, the coating will be too dense, affecting the electrolyte's ionic conductivity and performance; if the particle size is too large, the coating will be uneven, failing to achieve the desired coating effect and affecting the stability of the electrolyte and the positive electrode.

[0059] Preferably, sulfide electrolyte and halide electrolyte are weighed according to the ratio and placed into a stirring tank respectively, and then a certain amount of solvent is added to each. The process control is the same for both, and the mixture is stirred at a speed of 50~400 rpm / min for 2~4 hours. After the process is completed, uniform sulfide electrolyte suspension and halide electrolyte suspension are obtained respectively.

[0060] Preferably, the solid content of the sulfide electrolyte suspension is 30% to 70%.

[0061] Preferably, the solid content of the halide electrolyte suspension is 30% to 70%.

[0062] Preferably, the solvent is selected from at least one of alkane solvents, benzene solvents, ether solvents, and ketone solvents.

[0063] Preferably, the solvent is selected from at least one of dichloromethane, n-heptane, p-xylene, trimethylbenzene, anisole, monochlorobenzene, and cyclohexanone.

[0064] Preferably, the preparation method of the solid electrolyte material is carried out under an inert gas atmosphere.

[0065] Another aspect of the present invention relates to a lithium secondary battery, comprising the solid electrolyte material described above or a solid electrolyte material prepared by the method for preparing the solid electrolyte material described above;

[0066] Preferably, the lithium secondary battery includes: a semi-solid lithium secondary battery or an all-solid lithium secondary battery.

[0067] The solid electrolyte material can be applied to at least one or more of the positive electrode layer, electrolyte layer and negative electrode layer in lithium secondary batteries, including semi-solid lithium secondary batteries and all-solid lithium secondary batteries.

[0068] The embodiments of the present invention will now be described in detail with reference to specific examples and comparative examples.

[0069] Example 1

[0070] The preparation method of the "0.1%LiTaCl5F@Li6PS5Cl" solid electrolyte material includes the following steps:

[0071] 1. Under an argon atmosphere, weigh 20 g of Li6PS5Cl and place it in a stirring jar 1. Add 20 g of trimethylbenzene solvent and control the solid content to 50%. Simultaneously weigh 0.01 g of LiTaCl5F halide electrolyte and place it in a stirring jar 2. Add 5 g of trimethylbenzene solvent. Start stirring both at a speed of 250 rpm for 3 hours. After stirring, obtain uniform sulfide electrolyte suspension and halide electrolyte suspension respectively.

[0072] 2. Transfer the mixing tank containing the sulfide electrolyte suspension to an oil bath device, control the temperature at 60℃, and keep the stirring speed constant; then add the halide electrolyte suspension gradually with a pipette, and continue stirring for 4 hours while keeping the stirring speed constant after the addition is completed; then raise the oil bath temperature to 120℃ and continue stirring until the slurry becomes viscous to obtain precursor #1.

[0073] 3. Under an argon atmosphere, the No. 1 precursor was transferred to a freeze dryer, the temperature was controlled at -75℃, the vacuum was controlled at -85Pa, and the drying time was 8h. After the drying was completed, the No. 2 precursor was obtained.

[0074] 4. Under an argon atmosphere, the No. 2 precursor was transferred to a muffle furnace for low-temperature heat treatment at a temperature of 120℃, a temperature rise rate of 1℃ / min, and a holding time of 2h. After natural cooling, the crude electrolyte product was obtained.

[0075] 5. Finally, the crude product is ground and sieved to obtain an electrolyte product with an overall particle size ≤60μm.

[0076] Examples 2 to 10

[0077] In Examples 2-10, only the content of the LiTaCl5F electrolyte in the coating layer was changed, and the process flow was the same as in Example 1. Specific information is shown in Table 1.

[0078] Example 11

[0079] The coating material is LiTaCl5O 0.5 The coating amount for other processes is the same as in Example 7.

[0080] Example 12

[0081] The coating material is LiTaCl6, and the coating amount in other processes is the same as in Example 7.

[0082] Example 13

[0083] The preparation method of the "0.5%LiTaCl5F@Li6PS5Cl" solid electrolyte material includes the following steps:

[0084] 1. Same as Example 1;

[0085] 2. Transfer the stirred tank containing the sulfide electrolyte suspension to an oil bath device, control the temperature at 80℃, and the stirring speed at 50 rpm / min; then add the halide electrolyte suspension gradually with a pipette, and continue stirring for 2 hours while maintaining the stirring speed after the addition is complete; then raise the oil bath temperature to 200℃ and continue stirring until the slurry becomes viscous to obtain precursor #1.

[0086] 3. Under an argon atmosphere, the No. 1 precursor was transferred to a freeze dryer, the temperature was controlled at -100℃, the vacuum was controlled at -95Pa, and the drying time was 6h. After the drying was completed, the No. 2 precursor was obtained.

[0087] 4. Under an argon atmosphere, the No. 2 precursor was transferred to a muffle furnace for low-temperature heat treatment at a temperature of 120℃, a temperature rise rate of 1℃ / min, and a holding time of 2h. After natural cooling, the crude electrolyte product was obtained.

[0088] 5. Finally, the crude product is ground and sieved to obtain an electrolyte product with an overall particle size ≤60μm.

[0089] Example 14

[0090] The preparation method of the "0.5%LiTaCl5F@Li6PS5Cl" solid electrolyte material includes the following steps:

[0091] 1. Same as Example 1;

[0092] 2. Transfer the mixing tank containing the sulfide electrolyte suspension to an oil bath device, control the temperature at 50℃, and the stirring speed at 400 rpm / min; then add the halide electrolyte suspension gradually with a pipette, and continue stirring for 6 hours while maintaining the stirring speed after the addition is complete; then raise the oil bath temperature to 100℃ and continue stirring until the slurry becomes viscous to obtain precursor #1.

[0093] 3. Under an argon atmosphere, the 1# precursor was transferred to a freeze dryer, the temperature was controlled at -20℃, the vacuum was controlled at -60Pa, and the drying time was 8h. After the drying was completed, the 2# precursor was obtained.

[0094] 4. Under an argon atmosphere, the No. 2 precursor was transferred to a muffle furnace for low-temperature heat treatment at a temperature of 120℃, a temperature rise rate of 1℃ / min, and a holding time of 12h. After natural cooling, the crude electrolyte product was obtained.

[0095] 5. Finally, the crude product is ground and sieved to obtain an electrolyte product with an overall particle size ≤60μm.

[0096] Comparative Example 1

[0097] Li6PS5Cl was used as the electrolyte material on the positive electrode side.

[0098] Comparative Example 2

[0099] LiTaCl5F was used as the electrolyte material on the positive electrode side.

[0100] Comparative Example 3

[0101] The coating material is Li3InCl6, and the coating amount in other processes is the same as in Example 7.

[0102] Comparative Example 4

[0103] The preparation method of the "0.5%LiTaCl5F@Li6PS5Cl" solid electrolyte material includes the following steps:

[0104] 1. Mix Li6PS5Cl1 and LiTaCl5F in a certain proportion and ball mill them at a speed of 250 rpm / min for 20 h;

[0105] 2. Under an argon atmosphere, the ball-milled material is transferred to a muffle furnace for low-temperature heat treatment at a temperature of 120℃, a temperature rise rate of 1℃ / min, and a holding time of 2h. After natural cooling, the crude electrolyte product is obtained.

[0106] 4. Finally, the crude product is ground and sieved to obtain an electrolyte product with an overall particle size ≤60μm.

[0107] Table 1 Electrolyte material composition information

[0108]

[0109] Experimental Example

[0110] The test data for each embodiment and comparative example are shown in Table 2. The test methods are all the same, as detailed below:

[0111] Target electrolyte conductivity test: 100 mg of electrolyte powder was weighed and placed in an insulating sleeve with an inner diameter of 10 mm. It was then pressurized at 300 MPa and subjected to AC impedance spectroscopy to measure the impedance value of the electrolyte material. The thickness of the pressurized sheet electrolyte was then measured. Based on the sheet impedance value, thickness value, and area, the ionic conductivity of the electrolyte material was calculated using the formula σ = d / (R * S), where σ is the ionic conductivity (s / cm), d is the sheet thickness (cm), R is the impedance value (Ω), and S is the sheet area (cm²). The test results are shown in Table 2.

[0112] Target electrolyte voltage window test: The target electrolyte and conductive carbon powder were weighed at a weight ratio of 70:30 and ground evenly using an agate mortar. In an insulating outer cylinder with a diameter of 10 mm, 20 mg of the above target electrolyte-conductive carbon powder mixture and 20 mg of Li were added... 5.4 PS 4.4 Cl 1.6 The layers are then stacked. It is then press-molded under a pressure of 360 MPa, and then... 5.4 PS 4.4 Cl 1.6 A lithium foil was stacked on one side and pressurized to form a solid structure at 100 MPa. Stainless steel current collectors were then placed on the top and bottom of the stack, with current collector leads attached. A linear sweep voltammetry test was performed with a sweep range of 2-5 V and a sweep rate of 0.1 mV / s. The oxidation potential of the material was determined by the intersection of the tangent line drawn from the oxidation peak of the test curve and the abscissa. The results are shown in Table 2.

[0113] Target electrolyte density test: Weigh an appropriate amount of target electrolyte (mass denoted as m, unit g), grind it further, and then use the specific gravity bottle method to test the compacted volume (denoted as v, unit cm³). The density of the material is denoted as ρ. The density value of the target electrolyte (unit g / cm³) can be calculated by the formula ρ=m / v.

[0114] Battery testing: Inside an argon glove box, the target electrolyte and the positive electrode active material Li(Ni) were tested. 0.8 Co 0.1 Mn 0.1O2 (NCM811) was weighed at a weight ratio of 20:80. The mixture was ground uniformly using an agate mortar, thus preparing the composite cathode material. In an insulating outer cylinder with a diameter of 10 mm, 14 mg of the above cathode material and 70 mg of solid electrolyte material Li were... 5.4 PS 4.4 Cl 1.6 The layers are stacked. The stack is then pressurized at 360 MPa to form the positive electrode and solid electrolyte layer. Next, an aluminum foil is stacked on the positive electrode side to form a current collector. Then, on the opposite side of the solid electrolyte layer that contacts the positive electrode, an indium sheet with a thickness of 200 μm and a diameter of 10 mm is placed as the negative electrode material. This is pressurized at 80 MPa to create a stack consisting of the positive electrode, solid electrolyte layer, and negative electrode. Stainless steel current collectors are then placed on the top and bottom of the stack, and current collector leads are attached to the current collectors. Cycle performance testing is performed on the assembled solid-state battery under the following conditions: current density of 0.3C and voltage range of 2.7-4.3V (Li). + / Li). The test results are shown in Table 2.

[0115] Table 2. Electrolyte performance test information

[0116]

[0117] Combining the data in Tables 1 and 2, and through Examples 1-12 and Comparative Example 1, it can be seen that: with the increase of coating amount, the target electrolyte ionic conductivity and oxidation potential both show a trend of first gradually increasing significantly and then stabilizing; battery performance shows a trend of first increasing and then decreasing. When the coating amount reaches 3.5% (Example 7), the target electrolyte oxidation potential reaches its maximum value of 4.39V, the ionic conductivity basically reaches its highest level of 9.8mS / cm, the density is still at a relatively low level of 2.42g / cm³, and the battery performance is optimal (95.1% initial efficiency, 235mAh / g first-cycle discharge capacity, and 99.8% capacity retention after 200 cycles); Simultaneously, XRD tests show (e.g., ...) Figure 1 and Figure 2As shown in the diagram, with the increase of coating amount, the characteristic peaks of the sulfide electrolyte phase gradually decrease or the peak intensity decreases. When the coating amount is ≥3.5%, the XRD test of the target electrolyte shows an amorphous phase, which is consistent with the phase of the coating layer halide electrolyte. This indicates that under the condition of 3.5% coating amount, the coating is complete and dense, and the coating process is a physical process without chemical reaction. Under the same coating amount of 3.5%, the battery performance is the best when the coating layer material is LiTaCl5F halide electrolyte. In addition, the comparison between Example 1 and Examples 13 and 14 shows that too low or too high reaction temperature will affect the performance of the electrolyte. The comparison between Example 7 and Comparative Example 3 shows that the coating layer halide electrolyte material of this scheme has significant advantages over the commonly used Li3InCl6 material. The comparison between Example 1 and Comparative Example 4 shows that the electrolyte prepared by this experimental method has better performance than the electrolyte prepared by the conventional dry ball milling method.

[0118] Although the present invention has been illustrated and described with specific embodiments, it should be understood that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; those skilled in the art should understand that modifications can be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein, without departing from the spirit and scope of the present invention; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such substitutions and modifications that fall within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing a solid electrolyte material, characterized in that, Includes the following steps: (a) After adding the halide electrolyte suspension to the sulfide electrolyte suspension, the first reaction and the second reaction are carried out to obtain the first precursor; (b) The first precursor is dried and heat-treated; The temperature of the first reaction is 50~80℃; The temperature of the second reaction is 100~200℃; The sulfide electrolyte in the sulfide electrolyte suspension has a particle size of 30~80μm; The halide electrolyte in the halide electrolyte suspension has a particle size of 0.05~1μm; The solid electrolyte material includes a core and a coating layer covering the surface of the core: The core comprises a sulfide electrolyte; the coating layer comprises a halide electrolyte. The chemical formula of the halide electrolyte is: LiTaCl5M 1 / n n- M is selected from one or more of Cl, F, I, Br or O, and n is 1 or 2.

2. The method for preparing the solid electrolyte material according to claim 1, characterized in that, The mass ratio of the coating layer to the core is (0.001~0.1):

1.

3. The method for preparing the solid electrolyte material according to claim 1, characterized in that, The particle size of the solid electrolyte material is ≤60μm.

4. The method for preparing the solid electrolyte material according to claim 1, characterized in that, The chemical formula of the sulfide electrolyte is Li 7-x PS 6-x N x Wherein, N is selected from one or more of Cl, Br, F or I, and 0.1≤x≤5.

9.

5. The method for preparing the solid electrolyte material according to claim 1, characterized in that, The first reaction takes 2 to 6 hours.

6. The method for preparing the solid electrolyte material according to claim 1, characterized in that, The first reaction was carried out under stirring conditions, with a stirring speed of 50~400 rpm / min.

7. The method for preparing the solid electrolyte material according to claim 1, characterized in that, The second reaction takes 4 to 8 hours.

8. The method for preparing the solid electrolyte material according to claim 1, characterized in that, The second reaction is carried out under stirring conditions, with a stirring speed of 50~400 rpm / min.

9. The method for preparing the solid electrolyte material according to claim 1, characterized in that, The drying method includes: freeze drying.

10. The method for preparing the solid electrolyte material according to claim 9, characterized in that, The freeze-drying temperature is -100~-20℃.

11. The method for preparing the solid electrolyte material according to claim 9, characterized in that, The vacuum degree of the freeze-drying process is -95 to -60 Pa.

12. The method for preparing the solid electrolyte material according to claim 9, characterized in that, The freeze-drying time is 6-12 hours.

13. The method for preparing the solid electrolyte material according to claim 1, characterized in that, The heat treatment temperature is 100~200℃.

14. The method for preparing the solid electrolyte material according to claim 1, characterized in that, The heating rate of the heat treatment is 1~2℃ / min.

15. The method for preparing the solid electrolyte material according to claim 1, characterized in that, The heat treatment time is 1 to 4 hours.

16. A lithium secondary battery, characterized in that, Solid electrolyte materials prepared by the method described in any one of claims 1 to 15 include solid electrolyte materials.

17. The lithium secondary battery according to claim 16, characterized in that, The lithium secondary battery includes: a semi-solid lithium secondary battery or an all-solid lithium secondary battery.

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