A halide oxide solid-state electrolyte and a preparation method and application thereof

Abstract

The application relates to the technical field of solid-state batteries, in particular to a halide oxyde and a preparation method and application thereof. The application takes a molten salt Li a M b X c as raw material, reacts with an oxide A d O f in a molten state, removes steam impurities by means of high-temperature vacuum extraction, and obtains the halide oxyde solid-state electrolyte after cooling; the molten salt raw material is melted into an ionic melt at high temperature, oxygen elements are introduced to replace part of halogens, the hardness of the target electrolyte is reduced after cooling, the deformation ability at room temperature is improved, the obtained electrolyte has high conductivity, a wide oxidation electrochemical window, and the like. The prepared halide oxyde solid-state electrolyte is used for preparing a positive electrode, and the adhesion, actual micro contact area and ion migration rate between the electrolyte and positive electrode material particles are improved through melt infiltration, the positive electrode interface problem is effectively relieved, and the electrochemical performance of the full solid-state battery is improved.

Description

Technical Field

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

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

[0003] Halides can be broadly classified into three categories based on their structural types: one is anionic sublattice, such as Li3YBr6 (cubic close-packed anionic arrangement), with an ionic conductivity close to 10. -3 S / cm; secondly, cationic sublattices, using metal halides with larger cationic radii, such as LaCl3 and SmCl3, forming another structural category. These electrolytes have a zeolite-like UCl3-type structure with spacious nanopores exceeding 4 Å in diameter, further improving ion mobility; thirdly, halide oxides, such as Li─Ta─O─Cl, have high conductivity (above 10). -3 It has superior S / cm, oxidation stability and mechanical properties.

[0004] Current methods for preparing halide oxides typically involve using oxygen-containing compounds such as LiOH and Li₂O, along with metal halides, as raw materials, and synthesizing them through conventional mechanical mixing and heating. However, this synthesis method is prone to producing metastable crystalline and amorphous phases, with the amorphous state often exceeding 80 wt%. Furthermore, many metal halides readily undergo hydrolysis reactions in oxygen-containing compounds like LiOH and Li₂O.

[0005] Furthermore, the rational design and application of electrolytes in solid-state batteries faces numerous challenges, such as the solid-solid interface contact problem between the solid electrolyte and electrode particles. Solid-state batteries typically employ point contact, resulting in a small contact area. In some battery systems, the interface may initially be surface contact, but with battery cycling, the volume expansion of the electrode materials can deteriorate the initially good contact, increasing interfacial impedance and consequently affecting battery performance. Moreover, inorganic solid electrolytes lack elasticity, making it difficult to maintain close contact during the expansion and contraction of the positive and negative electrodes. While polymer electrolytes are elastic, they suffer from poor oxidation resistance and low conductivity. Therefore, the fabrication of most solid-state batteries relies on additional pressure to maintain close contact between the solid electrolyte and electrode particles.

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

[0007] The first objective of this invention is to provide a method for preparing a halide oxide solid electrolyte. By melting molten salt raw materials at high temperature to form an ionic melt, oxygen is introduced to replace part of the halogen, resulting in a target electrolyte with reduced hardness after cooling, enhanced deformability at room temperature, and high conductivity and a wide anti-oxidation electrochemical window.

[0008] The second objective of this invention is to provide a halide oxide solid electrolyte as described above, which is prepared by the halide oxide solid electrolyte preparation method described above.

[0009] A third objective of this invention is to provide an application of the halide oxide solid electrolyte as described above in the preparation of a positive electrode.

[0010] The fourth objective of this invention is to provide a method for preparing a positive electrode. This method utilizes melt penetration to improve the adhesion between the electrolyte and the positive electrode material particles, the actual microscopic contact area, and the ion migration rate, effectively alleviating the positive electrode interface problem.

[0011] The fifth objective of this invention is to provide a lithium-ion all-solid-state battery, including the positive electrode as described above.

[0012] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0013] A method for preparing a halide oxide solid electrolyte includes the following steps:

[0014] S1. For the raw material molten salt Li a M b X c Heating is performed to make it molten, where M is a metallic element, a+mb=c, m is the valence of element M, and X is a halogen;

[0015] S2. Add oxide A d O f Mix thoroughly;

[0016] S3. Above AX n At the boiling point temperature, AX is removed by vacuuming. n Vapor impurities, where n is the valence of element A, n=2f / d, are removed and cooled to obtain the halide oxide solid electrolyte.

[0017] A halide oxide solid electrolyte is prepared using the preparation method for halide oxide solid electrolytes described in the foregoing embodiments, wherein the general formula of the halide oxide solid electrolyte is 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.

[0018] The application of halide oxide solid electrolytes in the preparation of positive electrodes as described in the foregoing embodiments.

[0019] A method for preparing a positive electrode includes the following steps:

[0020] The positive electrode material, electrolyte, conductive agent and binder are mixed in proportion, rolled into a film, pressed onto the current collector, and then pressurized to remove voids. The mixture is then heated to 100~250℃ to allow the positive electrode material to fully permeate, thus obtaining the final product.

[0021] The electrolyte is the halide oxide solid electrolyte described in the foregoing embodiments.

[0022] An all-solid-state battery includes the positive electrode described in the foregoing embodiments or the positive electrode prepared by the method described in the foregoing embodiments.

[0023] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] (1) The method of the present invention uses molten salt as the reaction medium. It is a low viscosity liquid at high temperature and a high hardness, brittle crystal after cooling. The addition of oxygen to partially replace halogen increases the viscosity at high temperature, which reduces the hardness of the target electrolyte after cooling and enhances its deformability at room temperature. In addition, the raw materials have good conductivity, high ion migration rate and diffusion rate. Even if there is an impure phase after the electrolyte is synthesized, the impact on the material can be greatly reduced. The halide oxide solid electrolyte prepared by the method of the present invention has high conductivity and a wide electrochemical stability window.

[0025] (2) The limited actual micro-contact area not only restricts the ion transport path, but also greatly reduces the adhesion between the solid electrolyte and the electrode material. This invention utilizes melt penetration to improve the adhesion between the electrolyte and the positive electrode particles, the actual micro-contact area, and the final ion migration rate, effectively alleviating the positive electrode interface problem.

[0026] (3) The all-solid-state battery assembled from the cathode material prepared by the method of the present invention has high initial efficiency, high discharge capacity and good cycle stability. Detailed Implementation

[0027] The technical solution of the present invention will be clearly and completely described below with reference to 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.

[0028] A first aspect of the present invention provides a method for preparing a halide oxide solid electrolyte, comprising the following steps:

[0029] S1. For the raw material molten salt Li a M b X c Heating is performed to make it molten, where M is a metallic element, a+mb=c, m is the valence of metallic element M, and X is a halogen (such as at least one of F, Cl, Br, and I).

[0030] S2. Add oxide A d O f Mix thoroughly;

[0031] S3. Above AX n At the boiling point temperature, AX is removed by vacuuming. n Vapor impurities, where n is the valence of element A, n=2f / d, are cooled to obtain a halide oxide solid electrolyte.

[0032] The method of the present invention uses Li a M b X c The melting process forms an ionic melt, which is a low-viscosity liquid at high temperatures and a high-hardness, brittle crystal after cooling. Introducing oxygen to replace some halogens can increase the viscosity at high temperatures, thereby reducing the hardness of the target electrolyte after cooling, improving its deformability at room temperature, and enhancing the interfacial contact during the expansion process.

[0033] Traditional methods for synthesizing halide oxides are usually solid-state reactions. Due to the limited contact area between raw material particles, the reaction rate is slow, easily leading to incomplete local reactions or side reactions, resulting in metastable or amorphous phases and uneven product distribution. The method of this invention uses Li... a M b X cThe raw materials used have low melting points and can be melted into a molten state for reaction with low energy consumption. In the molten state, the raw materials dissolve in the melt, resulting in more uniform molecular-level mixing and a significantly increased reaction interface. This allows for a more complete chemical reaction, reduces the formation of impurity phases, and produces a more complete halide oxide electrolyte crystal structure with higher performance consistency. Furthermore, the halide oxide electrolyte produced in the molten state has moderate hardness after cooling and improved deformability at room temperature, which improves interfacial contact during charge and discharge. In contrast, products from solid-state reactions are often harder or more brittle, making it difficult to maintain close contact during long-term cycling and affecting battery life. In traditional solid-state reactions, many metal halides are prone to hydrolysis reactions with oxygen-containing compounds, generating byproducts that affect electrolyte performance. The molten state reaction avoids this problem because the raw materials do not come into contact with water in the high-temperature molten state, reducing the possibility of hydrolysis. In addition, the raw materials used in this invention have good conductivity and high ion migration and diffusion rates, which significantly reduces the impact on the material even if non-existent phases exist after electrolyte synthesis.

[0034] 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 influenced. 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, a suitable molten salt size can be selected according to the cathode material used to obtain an electrolyte that is compatible with the cathode material.

[0035] In some specific embodiments of the present invention, the element M includes at least one selected from 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.

[0036] In some specific embodiments of the present invention, in step S1, the raw material molten salt Li is... a M b X c After heating to a molten state, the process also includes adding metal M fragments to replenish 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.

[0037] In some specific embodiments of the present invention, a heat preservation and resting step is further included between step S1 and step S2. The heat preservation and resting time is 10 min to 2 h. For example, it can be any value or a range of any two values ​​among 10 min, 30 min, 1 h, 1.5 h, and 2 h. The purpose of heat preservation and resting is to allow the raw materials to fully melt and homogenize, which is conducive to the full contact and reaction of the subsequent raw materials and to ensure that volatile impurities are completely volatilized during this period.

[0038] 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.

[0039] 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 halide electrolyte composition.

[0040] In some specific embodiments of the present invention, before step S1, the process further includes preparing the raw material molten salt Li. a M b X c The impurity removal step of this invention utilizes the difference in solubility of impurities in the solid and liquid phases. Through partial melting and slow cooling, the impurities are enriched at one end of the molten salt. Specifically, it includes:

[0041] molten salt Li a M b X c The powder is placed in a long, narrow container (such as a crucible), and a moving heater is used to heat it from one end to partially melt the raw material. The heating position is then gradually moved to continuously move the melting zone to 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 with the melting zone. The end product is removed to obtain the purified molten salt raw material.

[0042] A second aspect of the present invention provides a halide oxide solid electrolyte, prepared by the method for preparing halide oxide solid electrolyte as described in any of the foregoing embodiments, wherein the general formula of the obtained halide oxide 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 halide oxide solid electrolyte provided by this invention exhibits strong deformability at room temperature, high conductivity, and a wide anti-oxidation electrochemical window.

[0043] A third aspect of the present invention provides the application of the halide oxide solid electrolyte described in the foregoing embodiments in the preparation of a positive electrode.

[0044] A fourth aspect of the present invention provides a method for preparing a positive electrode, comprising the following steps:

[0045] The positive electrode material, electrolyte, conductive agent and binder are mixed in proportion, rolled into a thin film, pressed onto the current collector, and then pressure is applied to remove the voids. The mixture is then heated to 100~250℃ to allow the positive electrode material to fully permeate, thus obtaining the final product.

[0046] The electrolyte is the halide oxide solid electrolyte described in the foregoing embodiments.

[0047] The method of this invention achieves melt infiltration by controlling the heating temperature. This melt infiltration enhances the adhesion between the electrolyte and positive electrode particles, the actual microscopic contact area, and the ion migration rate, effectively alleviating positive electrode interface problems. Full cells assembled using the positive electrode prepared by this method exhibit high initial efficiency, high discharge specific capacity, and good cycle stability.

[0048] In some specific embodiments of the present invention, the method for preparing the positive electrode specifically includes the following steps:

[0049] (1) The positive electrode material and the electrolyte are mixed and subjected to a first ball milling to obtain a first mixture;

[0050] (2) Add a conductive agent to the first mixture and perform a second ball milling to obtain a second mixture;

[0051] (3) Add a binder to the second mixture and perform a third ball milling to obtain a third mixture;

[0052] (4) Press the third mixture into a film, press it onto the carbon-coated film, apply pressure to remove voids, heat to 100~250℃, hold for 10s~5min, so that the positive electrode material can be completely penetrated, and the result is obtained.

[0053] First, the positive electrode material and electrolyte are ball-milled and mixed, which is beneficial to the uniform mixing of the positive electrode material and electrolyte. Since the binder is sticky, it is easy to clump together after being added first, which makes it difficult for the electrolyte and conductive agent to be evenly dispersed. Therefore, the binder is added last, and mixing in the above order is beneficial to the uniform dispersion of raw materials.

[0054] In some implementations, typically but not limitingly, for example, the heating temperature in step (4) can be any one value or a range of any two values ​​among 100°C, 130°C, 150°C, 180°C, 200°C, 220°C, and 250°C; the holding time can be any one value or a range of any two values ​​among 10s, 30s, 1min, 2min, 3min, 4min, and 5min.

[0055] In step (4), excessively high permeation temperature may cause the following problems: 1. Material structure damage, failure of positive electrode active material, and the positive electrode may undergo phase change or surface side reactions (such as oxygen release) under high temperature and pressure, reducing capacity; 2. Increased interfacial reaction, chemical side reactions, high temperature will accelerate the diffusion reaction at the positive electrode / electrolyte interface (such as element interdiffusion), forming a high impedance layer and increasing interfacial resistance; 3. Excessive densification, the plasticity of the material is enhanced at high temperature, which may lead to excessively low porosity (such as <5%), hindering the lithium ion transport path and reducing rate performance. Excessively low permeation temperature may cause the following problems: 1. Incomplete pore removal, brittle particles under cold pressing, poor plastic deformation ability of the material at low temperature, making it difficult to effectively close pores and discontinuous electron / ion conduction network; 2. Poor interfacial contact, insufficient physical contact area between positive electrode particles and solid electrolyte, and significantly increased interfacial impedance; 3. Risk of electrode cracking, the elastic modulus increases during low temperature rolling, the electrode is prone to microcracks, and crack propagation during cycling leads to capacity decay. By controlling the permeation temperature within the range of 100~250℃, excellent overall performance can be obtained.

[0056] 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 one value or a range of any two values ​​among 2:1, 2.5:1, 4:1, 6:1, 8:1, and 10:1; the rotational speed is 250~500 rpm, for example, it can be any one value or a range of any two values ​​among 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, and 500 rpm; the ball milling time is 10-60 min, for example, it can be any one value or a range of any two values ​​among 10 min, 20 min, 30 min, 40 min, 50 min, and 60 min.

[0057] In some specific embodiments of the present invention, the ball-to-material ratio of the second ball mill is (2~10):1, for example, it can be any one value or a range of any two values ​​among 2:1, 2.5:1, 4:1, 6:1, 8:1, and 10:1; the rotational speed is 250~500 rpm, for example, it can be any one value or a range of any two values ​​among 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, and 500 rpm; the ball milling time is 10-60 min, for example, it can be any one value or a range of any two values ​​among 10 min, 20 min, 30 min, 40 min, 50 min, and 60 min.

[0058] 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 one value or a range of any two values ​​among 2:1, 2.5:1, 4:1, 6:1, 8:1, and 10:1; the rotation speed is 250~500 rpm, for example, it can be any one value or a range of any two values ​​among 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, and 500 rpm; the ball milling time is 30 min~5 h, for example, it can be any one value or a range of any two values ​​among 30 min, 1 h, 2 h, 3 h, 4 h, and 5 h.

[0059] In some specific embodiments of the present invention, the mass of the positive electrode material, electrolyte, conductive agent and binder is (70~95):(5~30):(0.25~10):(0.25~7.5), for example, it can be any one value or a range of any two values ​​from 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.

[0060] In some specific embodiments of the present invention, the cathode material includes a ternary cathode 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 0.05O2, etc.), lithium-rich manganese-based cathode 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 Co 0.1 O2, etc.), lithium cobalt oxide cathode materials (such as LiCoO2), and cobalt-free cathode materials (such as Li[Ni)). 0.9 Mn 0.1 O2, Li 1.2 Mn 0.4 Ti 0.4 The cathode material contains at least one of the following: O2, etc., and its surface is coated with Ru. The Ru-O covalent bonds formed by the Ru coating not only stabilize lattice oxygen and prevent it from further participating in interfacial decomposition, but also enhance the Li... + The diffusion capacity of the above-mentioned oxide cathode material components enhances the material's activation performance.

[0061] Advantages of coating the surface of cathode materials with Ru: Improved electronic conductivity (Ru is a noble metal with excellent electronic conductivity); Ru coating or forming Ru-O bonds (such as RuO2) can build a conductive network on the cathode surface, reducing interfacial resistance and improving charge transfer efficiency, especially suitable for oxides with poor intrinsic conductivity; Stabilized surface structure (Ru coating can suppress side reactions between the cathode material and the electrolyte (such as transition metal dissolution) and reduce surface oxygen loss (especially under high pressure conditions), thereby delaying phase transitions and lattice distortions); Catalytic redox reactions (Ru can catalyze reversible redox reactions (O2- ... 2- / O n - This increases capacity; hybridization of Ru's d-electron orbitals with oxygen's p-orbitals promotes the reversibility of oxygen vacancy formation and repair, increasing specific capacity and mitigating voltage decay caused by oxygen release; it also inhibits transition metal migration, and high valence states of Ru (such as Ru...) 4+ It can stabilize the crystal structure, suppress the migration and valence state changes of transition metals (such as Ni, Co, and Mn) during charging and discharging, and reduce the Jahn-Teller effect (such as Mn). 3+ ); to optimize interfacial ion transport, the Ru coating layer may form a fast ion conductor interfacial phase (such as Li-Ru-O compounds), promoting Li +Diffusion kinetics, while blocking the electrolyte from corroding the bulk material, improves low-temperature performance and cycle stability.

[0062] In some specific embodiments of the present invention, the Ru coating amount on the surface of the positive electrode material is 0.05wt% to 5wt%, for example, it can be any one value or a range of any two values ​​from 0.05wt%, 0.1wt%, 0.2wt%, 0.3wt%, 0.4wt%, 0.5wt%.

[0063] Excessive Ru coating can lead to an imbalance in electron-ion conduction. Ru is a high electron conductor, and excessive coating can create an electron "short circuit," causing Li to... + Impaired charge transfer leads to increased battery polarization and decreased rate performance; it also exacerbates interfacial side reactions, increases interfacial impedance, and accelerates cycle capacity decay. Furthermore, excessive Ru coating mismatches the thermal expansion coefficients of the cathode material, making it prone to peeling during charge and discharge, causing crack propagation. Additionally, Ru is a precious metal, and excessive use significantly increases material costs. Insufficient Ru coating results in inadequate electron conduction, high charge transfer impedance, and an inability to form a continuous conductive network, leading to low initial discharge capacity and poor high-rate performance. Insufficient interface protection also prevents effective suppression of cathode / solid electrolyte interfacial side reactions, resulting in a thicker passivation layer and shortened cycle life. Moreover, insufficient Ru coating fails to improve oxidation stability under high voltage. Therefore, properly controlling the Ru coating amount helps improve the electrochemical performance of the battery.

[0064] 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.

[0065] In some specific embodiments of the present invention, the adhesive 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).

[0066] A fifth aspect of the present invention provides an all-solid-state battery, comprising the positive electrode described in the foregoing embodiments or the positive electrode prepared by the method described in any one of the foregoing embodiments.

[0067] The embodiments of the present invention will be described in detail below with reference to specific examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer are followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0068] Example 1

[0069] (a) Electrolytes

[0070] This embodiment provides a halide oxide solid electrolyte, prepared by the following method:

[0071] S0. First, place the raw material molten salt LiAlCl4 with a D50 particle size of 25μm in a long strip crucible. Use a moving heater to heat one end of the raw material to locally melt it. Then, gradually move the heating position so that the melting zone moves to the other end until it reaches the end. Utilize the difference in solubility of impurities in the solid and liquid phases to make the impurities move to the end with the melting zone. Remove the end product to obtain the purified molten salt raw material.

[0072] S1. Heat the purified raw material molten salt LiAlCl4 to 180℃ to make it molten, and let it stand for 6 hours;

[0073] S2. Add Sb2O3 oxide and mix thoroughly, wherein the molar ratio of LiAlCl4 to Sb2O3 is 4:1;

[0074] S3. The temperature was raised to 250℃ and held for 1.5 hours, during which SbCl3 vapor impurities were removed by high-temperature vacuuming. The mixture was then cooled to 50℃ to obtain a solid-state halide electrolyte, LiAlCl3, with a D50 of 550 nm. 2.5 O 0.75 .

[0075] (ii) Positive electrode

[0076] This embodiment also provides a positive electrode, the positive electrode material being NCM931 with a surface coating of 0.15wt% Ru, and a D50 of 2.5μm. The electrolyte is the halide oxide solid electrolyte LiAlCl prepared in Example 1. 2.5 O 0.75 The conductive agent is made of carbon nanotubes, and the binder is made of PTFE; the preparation method is as follows:

[0077] (1) Weigh the raw materials according to the mass ratio of positive electrode material, electrolyte, conductive agent and binder as 80:15:2.5:2.5;

[0078] (2) According to the ball-to-material ratio of 2.5:1, place the positive electrode material and electrolyte in the ball mill jar, stir evenly with a key, tighten the screw, seal the interface of the cover with tape, and mill at 250 rpm for 25 minutes to obtain the first mixture.

[0079] (3) Add carbon nanotubes to the first mixture and continue ball milling at 300 rpm for 40 min to obtain the second mixture;

[0080] (4) Add PTFE to the second mixture and grind it at 100 rpm for 2 hours to obtain the third mixture;

[0081] (5) The third mixture is rolled into a 10nm thick film, pressed onto the carbon-coated aluminum foil, and pressure is applied to remove the voids. The mixture is heated to 180°C and held for 35s to allow the positive electrode material to fully penetrate, thus obtaining the positive electrode.

[0082] Example 2

[0083] (a) Electrolytes

[0084] This embodiment provides a halide oxide solid electrolyte, prepared by the following method:

[0085] S0. First, place the raw material molten salt LiAlCl4 with a D50 particle size of 22μm in a long strip crucible. Use a moving heater to heat one end of the raw material to locally melt it. Then, gradually move the heating position so that the melting zone moves to the other end until it reaches the end. Utilize the difference in solubility of impurities in the solid and liquid phases to make the impurities move to the end with the melting zone. Remove the end product to obtain the purified molten salt raw material.

[0086] S1. Heat the purified raw material molten salt LiAlCl4 to 180℃ to make it molten, and keep it at this temperature for 6 hours;

[0087] S2. Add α-Bi2O3 oxide, mix and stir until homogeneous, wherein the molar ratio of LiAlCl4 to α-Bi2O3 is 1:0.5;

[0088] S3. Raise the temperature to 450℃ and hold for 3 hours, during which BiCl3 vapor impurities are removed by high-temperature vacuuming. Cool to 60℃ to obtain a halide oxide solid electrolyte LiAlClO with a D50 of 655 nm. 1.5 .

[0089] (ii) Positive electrode

[0090] The preparation method of the positive electrode is similar to that of Example 1, except that the electrolyte is the halide oxide solid electrolyte prepared in Example 2.

[0091] All other conditions are the same as in Example 1.

[0092] Example 3

[0093] (a) Electrolytes

[0094] This embodiment provides a halide oxide solid electrolyte, prepared by the following method:

[0095] S0. First, place the raw material molten salt LiTaCl4 with a D50 particle size of 5μm in a long strip crucible. Use a moving heater to heat one end of the raw material to locally melt it. Then, gradually move the heating position so that the melting zone moves to the other end until it reaches the end. Utilize the difference in solubility of impurities in the solid and liquid phases to make the impurities move to the end with the melting zone. Remove the end product to obtain the purified molten salt raw material.

[0096] S1. Heat the purified raw material molten salt LiTaCl4 to 385℃ to make it molten, and let it stand for 2.25h;

[0097] S2. Add Nb2O5 oxide, mix and stir evenly, and then pass chlorine gas through, wherein the molar ratio of LiTaCl4, chlorine gas and Nb2O5 is 1.5:0.5:0.2;

[0098] S3. The temperature was lowered to 265℃ and held for 2 hours, during which NbCl5 vapor impurities were removed by high-temperature vacuuming. The mixture was then cooled to 65℃ to obtain a halide oxide solid electrolyte Li with a D50 of 985 nm. 1.5 Ta 1.5 Cl5O1.

[0099] (ii) Positive electrode

[0100] The preparation method of the positive electrode is similar to that of Example 1, except that the electrolyte is the halide oxide solid electrolyte prepared in Example 3;

[0101] All other conditions are the same as in Example 1.

[0102] Example 4

[0103] (a) Electrolytes

[0104] This embodiment provides a halide oxide solid electrolyte, prepared by the following method:

[0105] S0. First, the raw material molten salt LiZrCl with a D50 particle size of 8.5μm is... 2.5 Br 2.5The raw material is placed in a long strip crucible and heated at one end by a moving heater to partially melt it. Then, the heating position is gradually moved to move the melting zone to 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 with the melting zone. The end product is removed to obtain the purified molten salt raw material.

[0106] S1. The purified raw material molten salt LiZrCl 2.5 Br 2.5 Heat to 265℃ until it becomes molten, add Zr metal scraps, and let stand for 1.25 hours;

[0107] S2. Add Al2O3 oxide, mix and stir until homogeneous, wherein LiZrCl 2.5 Br 2.5 The molar ratio of Zr and Al2O3 is 1.5:3:0.5;

[0108] S3. The temperature was lowered to 265℃ and held for 2.5 hours. During this time, AlBr3 and AlCl3 vapor impurities were removed by high-temperature vacuuming. The mixture was then cooled to 55℃ to obtain a halide oxide solid electrolyte Li with a D50 of 765 nm. 1.5 Zr 4.5 Cl 2.25 Br 2.25 O 1.5 .

[0109] (ii) Positive electrode

[0110] The preparation method of the positive electrode is similar to that of Example 1, except that the electrolyte is the halide oxide solid electrolyte prepared in Example 4, and in step (5), the heating temperature is 100 and the holding time is 5 min.

[0111] All other conditions are the same as in Example 1.

[0112] Example 5

[0113] (a) Electrolytes

[0114] This embodiment provides a halide oxide solid electrolyte, prepared by the following method:

[0115] S0. First, place the raw material molten salt LiYCl2Br2 with a D50 particle size of 6.5μm in a long strip crucible. Use a moving heater to heat one end of the raw material to locally melt it. Then, gradually move the heating position so that the melting zone moves to the other end until it reaches the end. Utilize the difference in solubility of impurities in the solid and liquid phases to make the impurities move to the end with the melting zone. Remove the end product to obtain the purified molten salt raw material.

[0116] S1. Heat the purified raw material molten salt LiYCl2Br2 to 385℃ to make it molten, and let it stand for 1.55h;

[0117] S2. Add HfO2 oxide and mix thoroughly, wherein the molar ratio of LiYCl2Br2 to HfO2 is 1:0.5;

[0118] S3. The temperature was lowered to 325℃ and held for 2.5 hours. During this period, HfBr4 and HfCl4 vapor impurities were removed by high-temperature vacuuming. The mixture was then cooled to 60℃ to obtain a halide oxide solid electrolyte LiYClBrO with a D50 of 900 nm.

[0119] (ii) Positive electrode

[0120] The preparation method of the positive electrode is similar to that of Example 1, except that the electrolyte is the halide oxide solid electrolyte prepared in Example 5, and in step (5), the heating temperature is 250°C and the holding time is 10s.

[0121] All other conditions are the same as in Example 1.

[0122] Comparative Example 1

[0123] (a) Electrolytes

[0124] Comparative Example 1 synthesized halide oxide electrolytes using a traditional 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℃ for 8 h, and natural cooling to obtain the final product.

[0125] (ii) Positive electrode

[0126] The preparation method of the positive electrode is similar to that of Example 1, except that the electrolyte is the halide oxide solid electrolyte prepared in Comparative Example 1.

[0127] All other conditions are the same as in Example 1.

[0128] Comparative Example 2

[0129] (a) Electrolytes

[0130] The preparation method of the electrolyte is the same as in Example 1.

[0131] (ii) Positive electrode

[0132] The preparation method of the positive electrode is similar to that of Example 1, except that in step (5), the heating temperature is 80°C and the time is 15 min.

[0133] All other conditions are the same as in Example 1.

[0134] Comparative Example 3

[0135] (a) Electrolytes

[0136] The preparation method of the electrolyte is the same as in Example 1.

[0137] (ii) Positive electrode

[0138] The preparation method of the positive electrode is similar to that of Example 1, except that in step (5), the heating temperature is 275°C and the holding time is 45s.

[0139] All other conditions are the same as in Example 1.

[0140] Comparative Example 4

[0141] (a) Electrolytes

[0142] The preparation method of the electrolyte is similar to that in Example 1, except that LiAlCl4 is replaced with equal amounts of LiCl and AlCl3 in an equimolar ratio. After ball milling and mixing LiCl, AlCl3 and Sb2O3, the mixture is kept at annealing temperature of 250℃ for 5 hours and then naturally cooled to obtain the electrolyte. The amount of Sb2O3 used is the same as in Example 1.

[0143] (ii) Positive electrode

[0144] The preparation method of the positive electrode is similar to that of Example 1, except that the electrolyte used is the halide oxide solid electrolyte prepared in Comparative Example 4.

[0145] All other conditions are the same as in Example 1.

[0146] Comparative Example 5

[0147] (a) Electrolytes

[0148] The preparation method of the electrolyte is similar to that of Example 1, except that step S0 is not performed, and the electrolyte is prepared directly using unpurified raw material molten salt LiAlCl4. All other conditions are the same as those in Example 1.

[0149] (ii) Positive electrode

[0150] The preparation method of the positive electrode is similar to that of Example 1, except that the electrolyte is the halide oxide solid electrolyte prepared in Comparative Example 5.

[0151] All other conditions are the same as in Example 1.

[0152] Test case

[0153] (1) The conductivity and antioxidant electrochemical window of the halide oxide solid electrolytes prepared in each example and each comparative example were tested respectively. The test methods are as follows:

[0154] (a) Conductivity test:

[0155] 1. Weigh 100mg of halide oxide solid electrolyte powder and place it into the inner liner of the mold (10 mm in diameter). Press it into an electrolyte sheet using a press (parameter: 400 MPa). Assemble a blocked symmetric cell by matching stainless steel blocking electrodes at both ends of the electrolyte sheet.

[0156] 2. The resistance value R (unit Ω) of the solid electrolyte was obtained by measuring the sample impedance value using an electrochemical workstation via electrochemical AC impedance spectroscopy. The test frequency was from 0.01 Hz to 1 MHz, the test disturbance voltage was 5 mV, and the test temperature was the temperature inside the glove box.

[0157] 3. Remove the electrolyte tablet and use a micrometer to measure the thickness L (in cm) of the solid electrolyte tablet.

[0158] 4. Then, the ionic conductivity of the solid electrolyte at the temperature inside the glove box is calculated using the formula: σLi + =L / (R×S;where σLi + —Ionic conductivity of solid electrolytes (S cm) -1 );

[0159] L—thickness of the solid electrolyte (cm);

[0160] R—Intrinsic resistance (Ω) of solid electrolyte;

[0161] S—Cross-sectional area of ​​solid electrolyte (cm²) 2 ).

[0162] (II) Antioxidant capacity test:

[0163] 1. Weigh out 100 mg of the total material according to the mass ratio of conductive agent SP: halide solid electrolyte = 9:1, place it in a mortar and grind it by hand for 10 minutes to mix it evenly;

[0164] 2. Weigh 100mg of halide solid electrolyte powder and place it into the inner liner of a mold (10 mm in diameter), and press it into electrolyte sheets using a press (parameter: 400 MPa);

[0165] 3. Spread 25 mg of the mixture from step (1) onto one end of the electrolyte, flatten it with a mold, and then compact it with a press (parameter: 400 MPa); introduce a Li sheet into the other end;

[0166] 4. Use an electrochemical workstation to perform LSV testing, setting the open-circuit voltage to ~6V and the scan rate to 0.1mV / S.

[0167] The test results are shown in Table 1.

[0168] (2) Solid-state batteries were assembled using the positive electrodes prepared in each embodiment and comparative example. The positive electrode, solid electrolyte layer, and negative electrode (Li / in) were sequentially assembled and sealed in an argon-filled glove box to obtain the battery. The battery's initial efficiency, 1C discharge capacity, and capacity retention after 100 cycles were tested. The battery assembly process and testing methods are as follows:

[0169] Solid-state battery mold battery assembly:

[0170] Its preparation method includes the following steps:

[0171] (1) Weigh 100mg of sulfide solid electrolyte and put it into the inner liner of the alumina ceramic mold (diameter 10 mm). Press it into an electrolyte sheet with a thickness of 155μm using a press (parameters: 100MPa, 30s). Remove excess electrolyte powder with a rubber bulb.

[0172] (2) Place the positive electrode on one side of the electrolyte, and place a 100μm indium foil on the other side of the electrolyte sheet, and then place a 50μm lithium copper composite strip, both with a diameter of 10mm.

[0173] (3) Fasten the mold and the pressure head, and tighten the nut to obtain the solid mold battery; test with Blue Electric.

[0174] Electrical performance testing:

[0175] 1. Test method for first-time efficiency: At 35±3℃, charge the battery with a constant current of 0.1C to 3.7V, and then charge it with a constant voltage of 3.7V to the cutoff current of 0.05C. Record the charging capacity as C1. Then discharge the battery with a constant current of 0.1C to 2.0V and record the discharge capacity as D1. Calculate the first-time efficiency based on the discharge capacity and charging capacity. First-time efficiency = (D1 / C1)×100%.

[0176] 2. Test method for first-cycle discharge capacity and capacity retention rate: At 35±3℃, charge at 1C constant current to 3.7V, then charge at 3.7V constant voltage to cutoff current of 0.05C, and record the charging capacity as C1. Discharge the battery at 1C constant current to 2.0V, and record the first-cycle discharge capacity as D1. Repeat the charge-discharge cycle N times to obtain the discharge capacity of the Nth cycle, which is recorded as DN. Calculate the first-cycle efficiency based on the first-cycle discharge capacity and the first-cycle charging capacity: First-cycle efficiency = (D1 / C1)×100%. Calculate the capacity retention rate of the Nth cycle based on the first-cycle discharge capacity and the Nth-cycle discharge capacity: Nth-cycle capacity retention rate = (DN / D1)×100%.

[0177] The test results are shown in Table 1.

[0178] Table 1

[0179]

[0180] 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 halide oxide solid electrolyte, characterized in that, Includes the following steps: S1. For the raw material molten salt Li a M b X c Heating is performed to make it molten, where M is a metallic element, a+mb=c, m is the valence of element M, and X is a halogen; S2. Add oxide A d O f Mix thoroughly; S3. Above AX n At the boiling point temperature, AX is removed by vacuuming. n Vapor impurities, where n is the oxidation state of element A, n=2f / d, are removed and cooled to obtain the halide oxide solid electrolyte; Prior to step S1, the process further includes processing the raw material molten salt Li. a M b X c The impurity removal step includes: The raw material molten salt Li a M b X c The powder is placed in a long, narrow container, and heating is started from one end to locally melt the raw material. Then, the heating position is gradually moved so that the melting zone moves to 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 with the melting zone. The end product is removed to obtain the purified molten salt raw material.

2. The method for preparing halide oxide solid electrolyte according to claim 1, characterized in that, It meets at least one of the following characteristics: (1) The element M 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 process also includes adding metal M shavings; (3) Between step S1 and step S2, there is also a heat preservation and resting step, the heat preservation and resting time is 10 min to 2 h; (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. A halide oxide solid electrolyte, characterized in that, The solid-state electrolyte is prepared by the method of claim 1 or 2, wherein the general formula of the solid-state electrolyte is 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.

4. A positive electrode, characterized in that, Includes the halide oxide solid electrolyte as described in claim 3.

5. A method for preparing a positive electrode, characterized in that, Includes 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, and then pressurized to remove voids. The mixture is then heated to 100~250℃ to allow the positive electrode material to fully permeate, thus obtaining the final product. The electrolyte is the halide oxide solid electrolyte as described in claim 3.

6. The method for preparing the positive electrode according to claim 5, characterized in that, Specifically, the following steps are included: (1) The positive electrode material and the electrolyte are mixed and subjected to a first ball milling to obtain a first mixture; (2) Add a conductive agent to the first mixture and perform a second ball milling to obtain a second mixture; (3) Add a binder to the second mixture and perform a third ball milling to obtain a third mixture; (4) The third mixture is rolled into a film and pressed onto the carbon-coated film. The voids are removed by applying pressure and heating to 100~250℃. The temperature is maintained for 10s~5min to allow the positive electrode material to fully penetrate.

7. The method for preparing the positive electrode according to claim 6, characterized in that, It meets 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 250~500rpm, and the ball milling time is 10-60min; (2) The ball-to-material ratio of the second ball mill is (2~10):1, the rotation speed is 250~500rpm, and the ball milling time is 10-60min; (3) The ball-to-material ratio of the third ball mill is (2~10):1, the rotation speed is 250~500rpm, and the ball milling time is 30min~5h.

8. The method for preparing the positive electrode according to any one of claims 5 to 7, characterized in that, It meets 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 cathode material includes at least one of ternary cathode material, lithium-rich manganese-based cathode material, lithium cobalt oxide cathode material, and cobalt-free cathode material, and the surface of the cathode material is coated with Ru element; (3) The conductive agent includes at least one of graphite, carbon nanotubes, acetylene black, graphene, and polymer conductive agents; (4) The adhesive includes at least one of polytetrafluoroethylene, polyvinylidene fluoride, SBR, CMC, PAA, PVA, PI, and PEO.

9. An all-solid-state battery, characterized in that, This includes the positive electrode as described in claim 4 or the positive electrode prepared by the method described in any one of claims 5 to 8.

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