Oxidation halide solid electrolyte and preparation method and application thereof

Abstract

The invention relates to the technical field of solid-state batteries, in particular to oxyhalide solid-state electrolyte as well as a preparation method and application thereof. The method comprises the following steps: taking molten salt LiaMbXc as a raw material, reacting with an oxide AdOf in a molten state, removing steam impurities by utilizing a high-temperature vacuumizing mode, and cooling to prepare the oxyhalide solid electrolyte; according to the invention, the molten salt raw material is molten at high temperature to form the ion melt, and the oxygen element is introduced to replace part of halogen, so that the hardness of the target electrolyte is reduced after cooling, the deformability at room temperature is improved, and the obtained electrolyte is high in conductivity and wide in antioxidant electrochemical window. The prepared oxyhalide solid electrolyte is used for preparing a positive electrode, the adhesion force between the electrolyte and positive electrode material particles, the actual microscopic contact area and the ion migration rate are improved through melt permeation, the problem of a positive electrode interface is effectively relieved, and the electrochemical performance of an all-solid-state battery is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solid-state batteries, and in particular to a halide oxide solid electrolyte and a preparation method and application thereof. Background Art

[0002] With the rapid development of all-solid-state batteries, developing qualified solid-state electrolytes has become one of the most important tasks in order to achieve high energy density. Halide solid electrolytes have attracted much attention from researchers due to their strong compatibility with high-energy cathode materials, wide electrochemical stability window, and excellent compatibility with oxide cathode materials.

[0003] Halides can be roughly divided into three categories according to their structural categories: one is the anion sublattice, such as Li3YBr6 (cubic close-packed anion arrangement) with an ionic conductivity close to 10 -3 S / cm; the second is the cation sublattice, which uses metal halides with larger cation radius, such as LaCl3 and SmCl3, to form another structural category. These electrolytes have a UCl3-type structure similar to zeolites, with spacious nanopores with diameters exceeding 4 Å, which further improves the mobility of ions; the third is oxyhalides, such as Li─Ta─O─Cl, which have higher conductivity (greater than 10 -3 S / cm), oxidation stability and mechanical properties are better.

[0004] Current methods for preparing oxyhalides typically use oxygen-containing compounds such as LiOH and Li2O and metal halides as raw materials, synthesized through conventional mechanical mixing and heating. However, this synthesis method is prone to producing metastable crystalline and amorphous phases, with the amorphous phase often exceeding 80% by weight. Furthermore, many metal halides are susceptible to hydrolysis in oxygen-containing compounds such as LiOH and Li2O.

[0005] In addition, applying a reasonable design of electrolytes to solid-state batteries also faces many difficulties, such as the solid-solid interface contact problem between the solid electrolyte and the electrode particles. The solid-solid interface contact mode of solid-state batteries is usually point contact, and the contact area is small. In some battery systems, the interface may initially be in surface contact, but as the battery cycles, the volume expansion of the electrode material will cause the originally good contact to deteriorate, increase the interface impedance, and thus affect the battery performance. In addition, inorganic solid electrolytes lack elasticity and it is difficult to maintain close contact when the positive and negative electrodes expand and contract. Although polymer electrolytes are elastic, they have poor oxidation resistance and low conductivity. Therefore, the preparation of most solid-state batteries can only rely on additional pressure to maintain close contact between the solid electrolyte and the electrode particles.

[0006] In view of this, the present invention is proposed. Summary of the Invention

[0007] The first purpose of the present invention is to provide a method for preparing a halide oxide solid electrolyte, by melting a molten salt raw material at a high temperature to form an ionic melt, introducing oxygen elements to replace part of the halogen, so that the hardness of the target electrolyte decreases after cooling, and the deformation ability at room temperature is enhanced, and the resulting electrolyte has high electrical conductivity and a wide anti-oxidation electrochemical window.

[0008] The second object of the present invention is to provide an oxyhalide solid electrolyte as described above, which is prepared by the preparation method of the oxyhalide solid electrolyte as described above.

[0009] The third object of the present invention is to provide an application of the oxyhalide solid electrolyte as described above in the preparation of a positive electrode.

[0010] The fourth object of the present invention is to provide a method for preparing a positive electrode, which uses melt infiltration to improve the adhesion, actual microscopic contact area and ion migration rate between the electrolyte and the positive electrode material particles, effectively alleviating the positive electrode interface problem.

[0011] The fifth object of the present invention is to provide a lithium-ion all-solid-state battery comprising the positive electrode as described above.

[0012] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are adopted: A method for preparing an oxyhalide solid electrolyte comprises the following steps: S1. Raw material molten salt Li a M b X c Heating to make it into a molten state, wherein M is a metal element, a+mb=c, m is the valence of the M element, and X is a halogen; S2. Add oxide A d O f , mix evenly; S3. Above AX n At boiling point, AX is removed by vacuuming. n Steam impurities, wherein n is the valence of element A, n=2f / d, are cooled to obtain the oxyhalide solid electrolyte.

[0013] A halide oxide solid electrolyte is prepared by the preparation method of the halide oxide solid electrolyte described in the above embodiment, wherein the halide oxide solid electrolyte has the general formula Li g M h X i O k , where 1≤g≤15, 0.005≤h≤5, 0.005≤i≤12, and 0.05≤k≤5.

[0014] The use of the oxyhalide solid electrolyte in the preparation of a positive electrode as described in the above embodiment.

[0015] A method for preparing a positive electrode comprises the following steps: The positive electrode material, electrolyte, conductive agent and binder are mixed in proportion, rolled into a film, pressed onto the current collector, pressurized to remove gaps, and heated to 100-250°C to allow the positive electrode material to fully penetrate. Wherein, the electrolyte is the oxyhalide solid electrolyte described in the above embodiment.

[0016] An all-solid-state battery comprises the positive electrode described in the aforementioned embodiment or the positive electrode prepared by the method for preparing the positive electrode described in the aforementioned embodiment.

[0017] Compared with the prior art, the present invention has the following beneficial effects: (1) The method of the present invention uses molten salt as a reaction medium, which is a low-viscosity liquid at high temperature and a high-hardness, brittle crystal after cooling; the addition of oxygen partially replaces the halogen, which increases the viscosity at high temperature, so that the hardness of the target electrolyte decreases after cooling and the deformability at room temperature is enhanced; and the raw materials have good electrical conductivity, high ion migration rate and diffusion rate. Even if impure phases exist after the electrolyte is synthesized, the impact on the material can be greatly reduced; the oxyhalide solid electrolyte prepared by the method of the present invention has high electrical conductivity and a wide electrochemical stability window.

[0018] (2) The limited actual microscopic contact area not only restricts the ion transfer path, but also greatly reduces the adhesion between the solid electrolyte and the electrode material. The present invention uses melt infiltration to improve the adhesion between the electrolyte and the positive electrode particles, the actual microscopic contact area, and ultimately the ion migration rate, effectively alleviating the positive electrode interface problem; (3) The all-solid-state battery assembled with the positive electrode material prepared by the method of the present invention has high first efficiency, high discharge capacity and good cycle stability. DETAILED DESCRIPTION

[0019] The technical scheme of the present invention will be clearly and completely described below in conjunction with specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work premise belong to the scope of protection of the present invention. Those who do not specify specific conditions in the embodiments are carried out according to normal conditions or the conditions recommended by the manufacturer. Those whose reagents or instruments are not specified by the manufacturer are conventional products that can be purchased commercially.

[0020] A first aspect of the present invention provides a method for preparing an oxyhalide solid electrolyte, comprising the following steps: S1. Raw material molten salt Li a M b X c Heating to a molten state, wherein M is a metal element, a+mb=c, m is the valence of the metal element M, and X is a halogen (such as at least one of F, Cl, Br, and I); S2. Add oxide A d O f , mix evenly; S3. Above AX n At boiling point, AX is removed by vacuuming. n Steam impurities, wherein n is the valence of element A, n=2f / d, are cooled to obtain a halide oxide solid electrolyte.

[0021] The method of the present invention is to a M b X c Melting forms an ion melt, which is a low-viscosity liquid at high temperature and a high-hardness, brittle crystal after cooling. Introducing oxygen elements to replace part of the halogen can increase the viscosity at high temperature, reduce the hardness of the target electrolyte after cooling, increase the deformation ability at room temperature, and improve the interfacial contact during the expansion process.

[0022] The traditional synthesis method of oxyhalides is usually a solid phase reaction. Due to the limited contact area between the raw material particles, the reaction rate is slow, which easily leads to local incomplete reaction or side reaction, thereby generating metastable crystalline phase or amorphous phase, and uneven product distribution. a M b X cAs raw materials, they have a low melting point and can be melted into a molten state for reaction at low energy consumption. In the molten state, the raw materials are dissolved in the melt, the molecular mixing is more uniform, the reaction interface is greatly increased, and a more sufficient chemical reaction can be achieved, the generation of impurity phases is reduced, and the resulting oxyhalide electrolyte crystal structure is more complete and the performance consistency is higher; and the oxyhalide electrolyte generated by the reaction in the molten state has a moderate hardness after cooling, and the deformability at room temperature is improved, which can improve the interfacial contact during the charge and discharge process, while the products generated by the solid-phase reaction are often hard or brittle, making it difficult to maintain close contact during long-term cycles, affecting the battery life; in traditional solid-phase reactions, many metal halides are easily hydrolyzed with oxygen-containing compounds to generate by-products, which affect the performance of the electrolyte, while the reaction in the molten state avoids this problem because the raw materials will not come into contact with water in the high-temperature molten state, reducing the possibility of hydrolysis reaction. In addition, the raw materials used in the present invention have good electrical conductivity, high ion migration and diffusion rates, and even if there is a non-existent phase after the electrolyte is synthesized, the impact on the material can be greatly reduced.

[0023] The molten salt serves not only as a reaction medium but also as a template. By controlling the size and properties of the molten salt, the structure and morphology of the electrolyte can be affected. This method can also effectively control the size and morphology of the electrolyte by controlling the cooling time and temperature of the molten salt. Therefore, the appropriate molten salt size can be selected according to the positive electrode material used to obtain an electrolyte that is compatible with the positive electrode material.

[0024] In some specific embodiments of the present invention, the M element includes at least one of Mg, Sr, Ba, Sc, Y, Ti, Zr, Hf, Nb, Ta, Mo, Mn, Fe, Co, Ir, Cu, Zn, Al, In, Ge, Sn, Sb, Bi, La, Ce, Pr, Nd, Sm, Pm, Eu, Er, Tm, Yb, Lu, Gd, Ac, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, and Md.

[0025] In some specific embodiments of the present invention, in step S1, the raw material molten salt Li a M b X c After heating to a molten state, the process also includes adding metal M scraps, the purpose of which is to supplement the metal M and adjust the M content in the final electrolyte. The amount of M used can be calculated based on the composition of the desired target electrolyte.

[0026] In some specific embodiments of the present invention, a heat preservation and holding step is included between step S1 and step S2, and the heat preservation and holding time is 10 minutes to 2 hours. For example, it can be any point value among 10 minutes, 30 minutes, 1 hour, 1.5 hours, and 2 hours, or a range value consisting of any two points. The purpose of the heat preservation and holding is to fully melt and homogenize the raw materials, which is conducive to sufficient contact and reaction of the subsequent raw materials and ensures that volatile impurities are completely evaporated during this period.

[0027] In some specific embodiments of the present invention, in step S2, element A includes at least one of Ti, Zr, Hf, Nb, Ta, Mo, Fe, Zn, Al, Ga, In, Sb, and Bi.

[0028] In some specific embodiments of the present invention, step S2 further includes the step of introducing oxygen and / or chlorine gas, the purpose of which is to supplement O and / or Cl to obtain the desired oxyhalide electrolyte composition.

[0029] In some specific embodiments of the present invention, before step S1, the raw material molten salt Li a M b X c The impurity removal step of the present invention utilizes the difference in solubility of impurities in the solid phase and the liquid phase to enrich the impurities at one end of the molten salt through local melting and slow cooling, specifically including: The raw material molten salt Li a M b X c The powder is placed in a long container (such as a crucible), and a mobile heater is used to heat the raw material from one end to partially melt it. The heating position is then gradually moved to move the melting zone toward the other end until it reaches the end. The difference in solubility of impurities in the solid and liquid phases is used to move the impurities to the end along with the melting zone, and the end product is removed to obtain a purified molten salt raw material.

[0030] The second aspect of the present invention provides an oxyhalide solid electrolyte, which is prepared by the preparation method of the oxyhalide solid electrolyte described in any one of the above embodiments, and the general formula of the obtained oxyhalide solid electrolyte is Li g M h X i O k , wherein 1≤g≤15, 0.005≤h≤5, 0.005≤i≤12, and 0.05≤k≤5. The oxyhalide solid electrolyte provided by the present invention has strong deformability at room temperature, high electrical conductivity, and a wide anti-oxidation electrochemical window.

[0031] A third aspect of the present invention provides a use of the oxyhalide solid electrolyte described in the aforementioned embodiment in preparing a positive electrode.

[0032] A fourth aspect of the present invention provides a method for preparing a positive electrode, comprising the following steps: The positive electrode material, electrolyte, conductive agent and binder are mixed in proportion, rolled into a thin film, pressed onto the current collector, pressurized to remove gaps, and heated to 100-250°C to allow the positive electrode material to fully penetrate. Wherein, the electrolyte is the oxyhalide solid electrolyte described in the above embodiment.

[0033] The method of the present invention achieves melt infiltration by controlling the heating temperature. This process improves the adhesion between the electrolyte and the positive electrode particles, the actual microscopic contact area, and the ion migration rate in the positive electrode, effectively alleviating positive electrode interface issues. Full batteries assembled using the positive electrodes prepared using this method exhibit high initial efficiency, high discharge specific capacity, and good cycling stability.

[0034] In some specific embodiments of the present invention, the method for preparing the positive electrode specifically includes the following steps: (1) mixing the positive electrode material and the electrolyte, and performing a first ball milling to obtain a first mixed material; (2) adding a conductive agent to the first mixture and performing a second ball milling to obtain a second mixture; (3) adding a binder to the second mixture and performing a third ball milling to obtain a third mixture; (4) Roll the third mixture into a film, press it onto the carbon-coated film, apply pressure to remove gaps, heat it to 100~250℃, and maintain it for 10s~5min to allow the positive electrode material to fully penetrate.

[0035] First, the positive electrode material and the electrolyte are ball-milled to mix them evenly, which is conducive to the uniform mixing of the positive electrode material and the electrolyte. Since the binder is relatively sticky, it is easy to form lumps if added first, making it difficult to evenly disperse the electrolyte and the conductive agent. Therefore, the binder is added last and mixed in the above order of addition to facilitate the uniform dispersion of the raw materials.

[0036] In some embodiments, typically but not limitatively, for example, the heating temperature in step (4) can be any value among 100°C, 130°C, 150°C, 180°C, 200°C, 220°C, 250°C, or a range consisting of any two values; the holding time can be any value among 10s, 30s, 1min, 2min, 3min, 4min, 5min, or a range consisting of any two values.

[0037] If the infiltration temperature in step (4) is too high, the following problems may occur: 1. Material structure is destroyed, the positive electrode active material fails, and the positive electrode may undergo phase change or surface side reaction (such as oxygen release) under high temperature and high pressure, reducing the capacity; 2. Interface reaction is intensified, chemical side reaction, high temperature will accelerate the diffusion reaction (such as element mutual diffusion) at the positive electrode / electrolyte interface, forming a high impedance layer and increasing the interface resistance; 3. Over-densification, the plasticity of the material is enhanced at high temperature, which may lead to too low porosity (such as <5%), hindering the lithium ion transmission path and reducing the rate performance. If the infiltration temperature is too low, the following problems may occur: 1. Pore removal is not complete, the particles are brittle when cold pressed, and the plastic deformation ability of the material at low temperature is poor, resulting in difficulty in effectively closing the pores and discontinuous electron / ion conduction network; 2. Poor interface contact, insufficient physical contact area between the positive electrode particles and the solid electrolyte, and significant increase in interface impedance; 3. Risk of electrode cracking, the elastic modulus increases during low temperature rolling, and the electrode is prone to microcracks. The crack expansion during cycling leads to capacity decay. By controlling the infiltration temperature within the range of 100~250℃, excellent comprehensive performance can be obtained.

[0038] In some specific embodiments of the present invention, the ball-to-material ratio of the first ball mill is (2~10):1, for example, it can be any point value among 2:1, 2.5:1, 4:1, 6:1, 8:1, 10:1, or a range value consisting of any two point values; the rotation speed is 250~500rpm, for example, it can be any point value among 250rpm, 300rpm, 350rpm, 400rpm, 450rpm, 500rpm, or a range value consisting of any two point values; the ball milling time is 10-60min, for example, it can be any point value among 10min, 20min, 30min, 40min, 50min, 60min, or a range value consisting of any two point values.

[0039] In some specific embodiments of the present invention, the ball-to-material ratio of the second ball milling is (2~10):1, for example, it can be any point value among 2:1, 2.5:1, 4:1, 6:1, 8:1, 10:1, or a range value consisting of any two point values; the rotation speed is 250~500rpm, for example, it can be any point value among 250rpm, 300rpm, 350rpm, 400rpm, 450rpm, 500rpm, or a range value consisting of any two point values; the ball milling time is 10-60min, for example, it can be any point value among 10min, 20min, 30min, 40min, 50min, 60min, or a range value consisting of any two point values.

[0040] In some specific embodiments of the present invention, the ball-to-material ratio of the third ball mill is (2~10):1, for example, it can be any point value among 2:1, 2.5:1, 4:1, 6:1, 8:1, 10:1, or a range value consisting of any two point values; the rotation speed is 250~500rpm, for example, it can be any point value among 250rpm, 300rpm, 350rpm, 400rpm, 450rpm, 500rpm, or a range value consisting of any two point values; the ball milling time is 30min~5h, for example, it can be any point value among 30min, 1h, 2h, 3h, 4h, 5h, or a range value consisting of any two point values.

[0041] In some specific embodiments of the present invention, the mass of the positive electrode material, the electrolyte, the conductive agent and the binder is (70~95):(5~30):(0.25~10):(0.25~7.5), for example, it can be any point value of 70:25:2.5:2.5, 70:12.5:10:7.5, 80:10:2.5:7.5, 80:15:2.5:2.5, 85:14.5:0.25:0.25, or a range value consisting of any two point values.

[0042] In some embodiments of the present invention, the positive electrode material includes a ternary positive electrode material (such as LiNi 1 / 3 Co 1 / 3Mn 1 / 3 O2、LiNi 0.5 Co 0.2 Mn 0.3 O2、LiNi 0.6 Co 0.2 Mn 0.2 O2、LiNi 0.8 Co 0.1 Mn 0.1 O2、LiNi 0.8 Co 0.15 Al 0.05 O2, etc.), lithium-rich manganese-based positive electrode materials (such as Li 1.2 Mn 0.6 Ni 0.2 O2、0.3Li2MnO3•0.7LiNi 0.5 Mn 0.5 O2、Li 1.2 Mn 0.54 Ni 0.13 Co 0.13 O2、0.5Li2MnO3•0.5LiMn 0.5 Ni 0.5 O2、Li 1.2 Mn 0.4 Ni 0.3 Co0.1 O2, etc.), lithium cobalt oxide positive electrode materials (such as LiCoO2), cobalt-free positive electrode materials (such as Li[Ni 0.9 Mn 0.1 ]O2、Li 1.2 Mn 0.4 Ti 0.4 O2, etc.), the surface of the positive electrode material is coated with Ru element. The Ru-O covalent bond formed by Ru coating can not only stabilize the lattice oxygen and prevent it from further participating in the interface decomposition, but also improve the Li + The diffusion ability in the above-mentioned oxide positive electrode material components stimulates the material activation performance.

[0043] Advantages of coating Ru elements on the surface of positive electrode materials: Improved electronic conductivity. Ru is a precious metal with excellent electronic conductivity. Coating Ru or forming Ru-O bonds (such as RuO2) can build a conductive network on the positive electrode surface, reduce interface resistance, and improve charge transfer efficiency, which is especially suitable for oxides with poor intrinsic conductivity. Stabilize the surface structure. The Ru coating layer can inhibit side reactions between the positive electrode material and the electrolyte (such as transition metal dissolution), reduce surface oxygen loss (especially under high pressure conditions), and thus delay phase transition and lattice distortion. Catalyze redox reactions. Ru can catalyze reversible redox reactions (O 2- / O n - ), improve the capacity; the hybridization of Ru's d electron orbital and oxygen's p orbital can promote the reversibility of oxygen vacancy formation and repair, increase specific capacity, and alleviate the voltage decay caused by oxygen release; inhibit transition metal migration, Ru's high valence state (such as Ru 4+ ) can stabilize the lattice structure, inhibit the migration and valence change of transition metals (such as Ni, Co, Mn) during charge and discharge, and reduce the Jahn-Teller effect (such as Mn 3+ ); optimize interfacial ion transport, the Ru coating layer may form a fast ion conductor interface phase (such as Li-Ru-O compound), promoting Li + diffusion dynamics, while preventing the electrolyte from corroding the bulk material, improving low-temperature performance and cycle stability.

[0044] In some specific embodiments of the present invention, the coating amount of Ru on the surface of the positive electrode material is 0.05wt%~5wt%, for example, it can be any point value among 0.05wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt% or a range value consisting of any two point values.

[0045] Excessive Ru coating will lead to an imbalance in electron-ion conduction. Ru is a high electron conductor, and excessive coating will form an electron "short circuit path", resulting in Li +Transmission is blocked, battery polarization increases, and rate performance decreases; it also leads to intensified interface side reactions, increased interface impedance, and accelerated cycle capacity decay; and excessively thick Ru does not match the thermal expansion coefficient of the positive electrode material, making it easy to peel off during the charge and discharge process, causing crack propagation; in addition, Ru is a precious metal, and excessive use will significantly increase material costs. Too little Ru coating will lead to insufficient electron conduction and high charge transfer impedance. Insufficient coating cannot form a continuous conductive network, resulting in low initial discharge capacity and poor high-rate performance; and insufficient interface protection. When Ru is insufficient, the positive electrode / solid electrolyte interface side reactions cannot be effectively suppressed, resulting in thickening of the interface passivation layer and shortened cycle life; in addition, insufficient Ru coating cannot improve oxidation stability under high voltage. Reasonable control of the Ru coating amount helps improve the electrochemical performance of the battery.

[0046] In some specific embodiments of the present invention, the conductive agent used includes at least one of graphite, carbon nanotubes, acetylene black, graphene, and polymer conductive agents.

[0047] In some specific embodiments of the present invention, the binder used includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, SBR (styrene-butadiene rubber), CMC (carboxymethyl cellulose), PAA (polyacrylic acid), PVA (polyvinyl alcohol), PI (polyimide), PEO (polyethylene oxide), PTFE (polytetrafluoroethylene), and PEO-PVDF (polyethylene oxide-polyvinylidene fluoride blend).

[0048] A fifth aspect of the present invention provides an all-solid-state battery, comprising the positive electrode described in the aforementioned embodiment or a positive electrode prepared by the method for preparing a positive electrode in any one of the aforementioned embodiments.

[0049] The embodiments of the present invention will be described in detail below with reference to specific examples, but it will be understood by those skilled in the art that the following examples are merely illustrative of the present invention and should not be construed as limiting the scope of the present invention. Where specific conditions are not specified in the examples, the methods were performed according to conventional conditions or the conditions recommended by the manufacturer. Where the manufacturers of the reagents or instruments are not specified, they are all commercially available conventional products.

[0050] Example 1 (1) Electrolytes This embodiment provides a halide oxide solid electrolyte, and the preparation method is as follows: S0. First, a raw material molten salt LiAlCl4 with a D50 particle size of 25 μm is placed in a long crucible. A mobile heater is used to heat one end of the crucible to partially melt the raw material. The heating position is then gradually moved to move the molten zone toward the other end until it reaches the end. The solubility difference between impurities in the solid and liquid phases is exploited to move the impurities along with the molten zone to the end. The end product is then removed to obtain a purified molten salt raw material. S1. The purified raw material molten salt LiAlCl4 is heated to 180°C to molten state and allowed to stand for 6 hours; S2 was added Sb2O3 oxide, mixed and stirred uniformly, wherein the molar ratio of LiAlCl4 to Sb2O3 was 4:1; S3. The temperature was raised to 250°C and kept at this temperature for 1.5 hours. During this period, SbCl3 vapor impurities were removed by high-temperature vacuum pumping. The mixture was then cooled to 50°C to obtain a halide oxide solid electrolyte LiAlCl with a D50 of 550 nm. 2.5 O 0.75 .

[0051] (2) Positive electrode This embodiment also provides a positive electrode, the positive electrode material is NCM931 with a surface coating of 0.15wt% Ru element, D50 is 2.5μm, and the electrolyte is the oxyhalide solid electrolyte LiAlCl prepared in Example 1. 2.5 O 0.75 , the conductive agent uses carbon nanotubes, and the binder uses PTFE; the preparation method is as follows: (1) Weigh the raw materials according to the mass ratio of positive electrode material, electrolyte, conductive agent and binder of 80:15:2.5:2.5; (2) Place the positive electrode material and electrolyte in a ball mill at a ball-to-material ratio of 2.5:1, stir evenly with a key, tighten the screws, seal the cover interface with tape, rotate at 250 rpm, and ball mill for 25 minutes to obtain the first mixture; (3) adding carbon nanotubes to the first mixture and continuing ball milling at a speed of 300 rpm for 40 min to obtain a second mixture; (4) adding PTFE to the second mixture and grinding at a speed of 100 rpm for 2 h to obtain a third mixture; (5) The third mixture is rolled into a 10 nm thick film, pressed onto a carbon-coated aluminum foil, and pressurized to remove voids. The film is heated to 180°C and maintained for 35 seconds to allow the positive electrode material to fully penetrate, thereby obtaining a positive electrode.

[0052] Example 2 (1) Electrolytes This embodiment provides a halide oxide solid electrolyte, and the preparation method is as follows: S0. First, a raw material molten salt, LiAlCl4, with a D50 particle size of 22 μm, is placed in a long crucible. A mobile heater is used to heat one end of the crucible to partially melt the raw material. The heating position is then gradually moved to move the molten zone toward the other end until it reaches the end. The solubility difference between impurities in the solid and liquid phases is exploited to move the impurities along with the molten zone to the end. The end product is then removed to obtain a purified molten salt raw material. S1. The purified raw material molten salt LiAlCl4 is heated to 180°C to molten state and kept warm for 6 hours; S2 was added α-Bi2O3 oxide, mixed and stirred uniformly, wherein the molar ratio of LiAlCl4 and α-Bi2O3 was 1:0.5; S3. The temperature was raised to 450°C and maintained for 3 hours. During this time, the BiCl3 vapor impurities were removed by high-temperature vacuum pumping. The solution was then cooled to 60°C to obtain the oxyhalide solid electrolyte LiAlClO with a D50 of 655 nm. 1.5 .

[0053] (2) Positive electrode The preparation method of the positive electrode is similar to that of Example 1, except that the electrolyte is the oxyhalide solid electrolyte prepared in Example 2; The remaining conditions are the same as those in Example 1.

[0054] Example 3 (1) Electrolytes This embodiment provides a halide oxide solid electrolyte, and the preparation method is as follows: S0. First, a raw material molten salt LiTaCl4 with a D50 particle size of 5μm is placed in a long crucible. A mobile heater is used to heat one end of the crucible to partially melt the raw material. The heating position is then gradually moved to move the molten zone toward the other end until it reaches the end. The solubility difference between impurities in the solid and liquid phases is exploited to move the impurities along with the molten zone to the end. The end product is then removed to obtain a purified molten salt raw material. S1. The purified raw material molten salt LiTaCl4 was heated to 385°C to molten state and allowed to stand for 2.25h; S2 was added Nb2O5 oxide, mixed and stirred, and chlorine was introduced, wherein the molar ratio of LiTaCl4, chlorine and Nb2O5 was 1.5:0.5:0.2; S3. The temperature was lowered to 265°C and kept at this temperature for 2 hours. During this period, NbCl5 vapor impurities were removed by high-temperature vacuum pumping. The mixture was then cooled to 65°C to obtain a halide solid electrolyte Li with a D50 of 985 nm. 1.5 Ta 1.5 Cl5O1.

[0055] (2) Positive electrode The preparation method of the positive electrode is similar to that of Example 1, except that the electrolyte is the oxyhalide solid electrolyte prepared in Example 3; The remaining conditions are the same as those in Example 1.

[0056] Example 4 (1) Electrolytes This embodiment provides a halide oxide solid electrolyte, and the preparation method is as follows: S0. First, the raw material molten salt LiZrCl with a D50 particle size of 8.5 μm 2.5 Br 2.5 Place the raw material in a long crucible, use a mobile heater to heat one end of it to partially melt the raw material, then gradually move the heating position to make the molten zone move continuously to the other end until it reaches the end. Utilize the difference in solubility of impurities in the solid phase and the liquid phase to make the impurities move to the end with the molten zone, remove the end product, and obtain the purified molten salt raw material; S1. The purified raw material molten salt LiZrCl 2.5 Br 2.5 Heat to 265°C to make it molten, add Zr metal chips, and let it stand for 1.25 hours; S2. Add Al2O3 oxide and mix well. Among them, LiZrCl 2.5 Br 2.5 , the molar ratio of Zr and Al2O3 is 1.5:3:0.5; S3. The temperature was lowered to 265°C and kept at this temperature for 2.5 hours. During this time, AlBr3 and AlCl3 vapor impurities were removed by high-temperature vacuum pumping. The mixture was then cooled to 55°C to obtain a halide solid electrolyte Li with a D50 of 765 nm. 1.5 Zr 4.5 Cl 2.25 Br 2.25 O 1.5 .

[0057] (2) Positive electrode The preparation method of the positive electrode is similar to that of Example 1, with the only difference being that the electrolyte is the oxyhalide solid electrolyte prepared in Example 4, and in step (5), the heating temperature is 100°C and the holding time is 5 minutes; The remaining conditions are the same as those in Example 1.

[0058] Example 5 (1) Electrolytes This embodiment provides a halide oxide solid electrolyte, and the preparation method is as follows: S0. First, a molten salt raw material, LiYCl2Br2, with a D50 particle size of 6.5 μm, is placed in a long crucible. A mobile heater is used to heat one end of the crucible to partially melt the raw material. The heating position is then gradually moved to move the molten zone toward the other end until it reaches the end. The solubility difference between impurities in the solid and liquid phases is exploited to move the impurities along with the molten zone to the end. The end product is then removed to obtain a purified molten salt raw material. S1. The purified raw material molten salt LiYCl2Br2 was heated to 385°C to molten state and allowed to stand for 1.55h; S2 HfO2 oxide was added and mixed uniformly, wherein the molar ratio of LiYCl2Br2 and HfO2 was 1: 0.5; S3. The temperature was lowered to 325°C and maintained for 2.5 hours. During this time, HfBr4 and HfCl4 vapor impurities were removed by high-temperature vacuum pumping. The mixture was then cooled by 60°C to obtain the oxyhalide solid electrolyte LiYClBrO with a D50 of 900 nm.

[0059] (2) Positive electrode The preparation method of the positive electrode is similar to that of Example 1, with the only difference being that the electrolyte is the oxyhalide solid electrolyte prepared in Example 5, and in step (5), the heating temperature is 250°C and the holding time is 10s; The remaining conditions are the same as those in Example 1.

[0060] Comparative Example 1 (1) Electrolytes Comparative Example 1: A halide oxide electrolyte was synthesized by conventional ball milling followed by heat treatment. The raw materials were LiCl, AlCl3, and Al2O3 in a molar ratio of 1:0.5:0.25, a ball-to-material ratio of 25:1, a rotation speed of 550 rpm, ball milling for 10 h, heat treatment at 180 ° C for 8 h, and natural cooling.

[0061] (2) Positive electrode The preparation method of the positive electrode is similar to that of Example 1, except that the electrolyte is the oxyhalide solid electrolyte prepared in Comparative Example 1; The remaining conditions are the same as those in Example 1.

[0062] Comparative Example 2 (1) Electrolytes The preparation method of the electrolyte is the same as that in Example 1.

[0063] (2) Positive electrode The preparation method of the positive electrode is similar to that of Example 1, with the only difference being that in step (5), the heating temperature is 80°C and the heating time is 15 min; The remaining conditions are the same as those in Example 1.

[0064] Comparative Example 3 (1) Electrolytes The preparation method of the electrolyte is the same as that in Example 1.

[0065] (2) Positive electrode The preparation method of the positive electrode is similar to that of Example 1, with the only difference being that in step (5), the heating temperature is 275°C and the holding time is 45 seconds; The remaining conditions are the same as those in Example 1.

[0066] Comparative Example 4 (1) Electrolytes The preparation method of the electrolyte is similar to that of Example 1, with the only difference being that LiAlCl4 is replaced with equal amounts of LiCl and AlCl3 in an equimolar ratio, and LiCl, AlCl3 and Sb2O3 are ball-milled and mixed, then annealed at 250°C for 5h and naturally cooled to obtain the electrolyte; the amount of Sb2O3 used is the same as that of Example 1.

[0067] (2) Positive electrode The preparation method of the positive electrode is similar to that of Example 1, except that the electrolyte is the oxyhalide solid electrolyte prepared in Comparative Example 4; The remaining conditions are the same as those in Example 1.

[0068] Comparative Example 5 (1) Electrolytes The preparation method of the electrolyte is similar to that of Example 1, with the only difference being that step S0 is not performed, and the electrolyte is directly prepared using the unpurified raw material molten salt LiAlCl4. The other conditions are the same as those of Example 1.

[0069] (2) Positive electrode The preparation method of the positive electrode is similar to that of Example 1, except that the electrolyte is the oxyhalide solid electrolyte prepared in Comparative Example 5; The remaining conditions are the same as those in Example 1.

[0070] Test example (1) The conductivity and anti-oxidation electrochemical window of the oxyhalide solid electrolytes prepared in each embodiment and each comparative example were tested respectively. The test method is as follows: (1) Conductivity test: 1. Weigh 100 mg of oxyhalide solid electrolyte powder and place it in a mold (10 mm diameter). Press it into an electrolyte sheet using a press (parameter: 400 MPa). Place stainless steel blocking electrodes at both ends of the electrolyte sheet to assemble into a blocked symmetrical cell. 2. Use an electrochemical workstation to measure the sample impedance using electrochemical impedance spectroscopy to obtain the resistance value R (unit: Ω) of the solid electrolyte. The test frequency is 0.01 Hz to 1 MHz, the test disturbance voltage is 5 mV, and the test temperature is the temperature inside the glove box. 3. Take out the electrolyte sheet and use a micrometer to measure the thickness L (in cm) of the solid electrolyte sheet; 4. Then calculate the ionic conductivity of the solid electrolyte at the temperature inside the glove box using the formula: σLi + =L / (R×S); where σLi + ——Ionic conductivity of solid electrolyte (S cm -1 ); L – thickness of solid electrolyte (cm); R——intrinsic resistance of solid electrolyte (Ω); S——cross-sectional area of ​​solid electrolyte (cm 2 ).

[0071] (2) Antioxidant capacity test: 1. Weigh 100 mg of the total material in a mass ratio of conductive agent SP to halide solid electrolyte = 9:1 and grind it by hand in a mortar for 10 minutes to mix it evenly; 2. Weigh 100 mg of halide solid electrolyte powder and place it in a mold (10 mm diameter). Press it into an electrolyte sheet using a press (parameter: 400 MPa). 3. Spread 25 mg of the mixture from step (1) on one end of the electrolyte, flatten it with a mold, and compact it with a press (parameter: 400 MPa); introduce a Li sheet on the other end; 4. Perform LSV test using an electrochemical workstation, set the open circuit voltage to ~6 V, and the scan rate to 0.1 mV / s.

[0072] The test results are shown in Table 1.

[0073] (2) All-solid-state batteries were assembled using the positive electrodes prepared in each embodiment and comparative example. In an argon-filled glove box, the positive electrode, solid electrolyte layer, and negative electrode (Li / in) were assembled and sealed in sequence to obtain batteries. The batteries were tested for their initial efficiency, 1C discharge capacity, and capacity retention after 100 cycles. The battery assembly process and testing methods are as follows: Solid-state battery mold battery assembly: The preparation method comprises the following steps: (1) Weigh 100 mg of sulfide solid electrolyte and place it in the inner liner of an alumina ceramic mold (10 mm in diameter). Use a press to press it into an electrolyte sheet with a thickness of 155 μm (parameters: 100 MPa, 30 s). Use an ear bulb to remove excess electrolyte powder. (2) Place the positive electrode on one side of the electrolyte, and on the other side of the electrolyte sheet, first place a 100 μm indium foil, then place a 50 μm lithium-copper composite tape, both with a diameter of 10 mm; (3) Fasten the mold and the press head, tighten the nut, and the solid-state mold battery is obtained; test with blue light; Electrical performance test: 1. First-effect test method: At 35±3℃, charge the battery to 3.7V at 0.1C constant current, then charge at 3.7V constant voltage to a cut-off current of 0.05C, and record the charge capacity as C1. Then discharge the battery to 2.0V at 0.1C constant current, and record the discharge capacity as D1. Calculate the first-effect based on the discharge capacity and charge capacity: first-effect = (D1 / C1) × 100%.

[0074] 2. Test method for first-cycle discharge capacity and capacity retention rate: At 35±3℃, charge to 3.7V at 1C constant current, charge at 3.7V constant voltage to cut-off current 0.05C, record the charging capacity as C1, discharge the battery to 2.0V at 1C constant current, and record the 1C first-cycle discharge capacity as D1; ​​repeat the charge and discharge steps for N weeks, obtain the Nth-cycle discharge capacity as DN, calculate the first efficiency based on the first-cycle discharge capacity and the first-cycle charging capacity, first efficiency = (D1 / C1) × 100%, calculate the Nth-cycle capacity retention rate based on the first-cycle discharge capacity and the Nth-cycle discharge capacity, Nth-cycle capacity retention rate = (DN / D1) × 100%.

[0075] The test results are shown in Table 1.

[0076] Table 1

[0077] Although the present invention has been illustrated and described using specific embodiments, it should be appreciated that the above embodiments are merely intended to illustrate the technical solutions of the present invention rather than to limit them. Those skilled in the art should understand that the technical solutions described in the above embodiments may be modified, or some or all of the technical features thereof may be replaced by equivalents, without departing from the spirit and scope of the present invention. However, these modifications or replacements do not deviate from the essence of the corresponding technical solutions within the scope of the technical solutions of the embodiments of the present invention. Therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing an oxyhalide solid electrolyte, characterized in that: The following steps are involved: S1. Raw material molten salt Li a M b X c Heating to make it into a molten state, wherein M is a metal element, a+mb=c, m is the valence of the M element, and X is a halogen; S2. Add oxide A d O f , mix evenly; S3. Above AX n At boiling point, AX is removed by vacuuming. n Steam impurities, wherein n is the valence of element A, n=2f / d, are cooled to obtain the oxyhalide solid electrolyte.

2. The method for preparing an oxyhalide solid electrolyte according to claim 1, wherein: Meet at least one of the following characteristics: (1) The M element includes at least one of Mg, Sr, Ba, Sc, Y, Ti, Zr, Hf, Nb, Ta, Mo, Mn, Fe, Co, Ir, Cu, Zn, Al, In, Ge, Sn, Sb, Bi, La, Ce, Pr, Nd, Sm, Pm, Eu, Er, Tm, Yb, Lu, Gd, Ac, Th, Pa, U, Np, Pu, Am, Cm, Bk, Cf, Es, Fm, and Md; (2) In step S1, the raw material molten salt Li a M b X c After heating to a molten state, the step of adding metal M chips is also included; (3) Between step S1 and step S2, a step of heat preservation and storage is included, and the heat preservation and storage time is 10 minutes to 2 hours; (4) In step S2, the element A includes at least one of Ti, Zr, Hf, Nb, Ta, Mo, Fe, Zn, Al, Ga, In, Sb, and Bi; (5) Step S2 also includes the step of introducing oxygen and / or chlorine.

3. The method for preparing an oxyhalide solid electrolyte according to claim 1, wherein: Before step S1, the step of removing impurities from the raw material molten salt LiaMbXc is also included, and the impurity removal includes: The raw material molten salt Li a M b X c The powder is placed in a long rectangular container and heated from one end to partially melt the raw material. The heating position is then gradually moved to allow the melting zone to continuously move toward the other end until it reaches the end. The solubility difference between impurities in the solid and liquid phases is utilized to move the impurities along with the melting zone to the end, and the end product is removed to obtain the purified molten salt raw material.

4. A halide oxide solid electrolyte, characterized in that: The oxyhalide solid electrolyte is prepared by the preparation method of any one of claims 1 to 3, wherein the general formula of the oxyhalide solid electrolyte is LigMhXiOk, wherein 1≤g≤15, 0.005≤h≤5, 0.005≤i≤12, and 0.05≤k≤5.

5. Use of the oxyhalide solid electrolyte as claimed in claim 4 in the preparation of a positive electrode.

6. A method for preparing a positive electrode, characterized in that: The following steps are involved: The positive electrode material, electrolyte, conductive agent and binder are mixed in proportion, rolled into a film, pressed onto the current collector, pressurized to remove gaps, and heated to 100-250°C to allow the positive electrode material to fully penetrate. Wherein, the electrolyte is the oxyhalide solid electrolyte according to claim 4.

7. The method for preparing a positive electrode according to claim 6, wherein: The specific steps include: (1) mixing the positive electrode material and the electrolyte, and performing a first ball milling to obtain a first mixed material; (2) adding a conductive agent to the first mixture and performing a second ball milling to obtain a second mixture; (3) adding a binder to the second mixture and performing a third ball milling to obtain a third mixture; (4) Roll the third mixture into a film, press it onto the carbon-coated film, apply pressure to remove voids, heat to 100-250°C, and maintain for 10s-5min to allow the positive electrode material to fully penetrate.

8. The method for preparing a positive electrode according to claim 7, wherein: Meet at least one of the following characteristics: (1) The ball-to-material ratio of the first ball mill is (2-10):1, the rotation speed is 250-500 rpm, and the ball milling time is 10-60 min; (2) The ball-to-material ratio of the second ball mill is (2-10):1, the rotation speed is 250-500 rpm, and the ball milling time is 10-60 min; (3) The ball-to-material ratio of the third ball mill is (2-10):1, the rotation speed is 250-500 rpm, and the ball milling time is 30 min-5 h.

9. The method for preparing a positive electrode according to any one of claims 6 to 8, wherein: Meet at least one of the following characteristics: (1) The mass ratio of the positive electrode material, the electrolyte, the conductive agent and the binder is (70-95): (5-30): (0.25-10): (0.25-7.5); (2) The positive electrode material includes at least one of a ternary positive electrode material, a lithium-rich manganese-based positive electrode material, a lithium cobalt oxide positive electrode material, and a cobalt-free positive electrode material, and the surface of the positive electrode material is coated with Ru element; (3) The conductive agent includes at least one of graphite, carbon nanotubes, acetylene black, graphene, and a polymer conductive agent; (4) The binder includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, SBR, CMC, PAA, PVA, PI, and PEO.

10. An all-solid-state battery, characterized in that: The positive electrode comprises the positive electrode according to claim 5 or the positive electrode prepared by the preparation method of the positive electrode according to any one of claims 6 to 9.

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