Positive electrode material and preparation method therefor, positive electrode sheet, and all-solid-state battery

Abstract

The present application provides a positive electrode material and a preparation method therefor, a positive electrode sheet, and an all-solid-state battery. The positive electrode material comprises: a lithium-rich manganese-based positive electrode active material and a coating layer covering at least part of the surface of the lithium-rich manganese-based positive electrode active material. The molecular formula of the lithium-rich manganese-based positive electrode active material is xLi2-αMnO3(1-x)Li1-βNiaCobMncO2-γ, wherein a+b+c=1, 0<α+β≤0.2, 0<γ≤0.1, and 0<x<1. The coating layer satisfies the following formulas: formula 1: 0.5×10-3S / cm≤T≤5×10-3S / cm, and formula 2: H≤10-9S / cm, wherein T is the ionic conductivity of the coating layer, and H is the electronic conductivity of the coating layer. The positive electrode material provided by the present application solves the problem of low first coulombic efficiency of lithium-rich manganese-based positive electrode materials, and improves the migration efficiency of interface ions and the stability of positive electrode materials.

Description

A positive electrode material and preparation method thereof, a positive electrode sheet and an all-solid-state battery

[0001] This application claims priority to the Chinese patent application filed with the Patent Office of China on March 6, 2024, with application number 202410257081.7 and application name “A positive electrode material and its preparation method, positive electrode sheet and all-solid-state battery”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to the field of battery materials, and in particular to a positive electrode material and a preparation method thereof, a positive electrode sheet and an all-solid-state battery. Background Art

[0003] Among solid-state electrolytes, sulfide-based solid electrolytes have attracted widespread attention due to their high electrical conductivity, high lithium-ion mobility, and excellent mechanical properties and thermal stability. Lithium-rich manganese-based cathode materials are potential cathode materials for high-energy-density lithium-ion batteries, facilitating the assembly of high-energy-density all-solid-state batteries. However, the low initial coulombic efficiency of lithium-rich manganese-based cathode materials has hindered their commercialization. Furthermore, when lithium-rich manganese-based cathode materials come into contact with mainstream sulfide-based solid electrolytes, a space charge layer is generated, and side reactions occur to form an inert interface layer, hindering the migration of interfacial ions. Therefore, while addressing the low coulombic efficiency of lithium-rich manganese-based cathode materials, reducing the interfacial reaction between lithium-rich manganese-based cathode materials and sulfide solid electrolytes will help promote their industrialization in the field of all-solid-state batteries.

[0004] Application Contents

[0005] The present application provides a positive electrode material, which solves the problem of low initial coulombic efficiency of lithium-rich manganese-based positive electrode materials, while reducing the possibility of generating a space charge layer and an inert interface layer when the lithium-rich manganese-based positive electrode material contacts a sulfide solid electrolyte, thereby improving the migration efficiency of interface ions.

[0006] The present application also provides a method for preparing the above-mentioned positive electrode material, which can prepare the above-mentioned positive electrode material and has a simple process.

[0007] The present application also provides a positive electrode plate. Since the plate includes the above-mentioned positive electrode material, the plate is used in a battery to help improve the battery's first coulombic efficiency, discharge specific capacity and cycle performance.

[0008] The present application also provides an all-solid-state battery. Since the all-solid-state battery includes the above-mentioned positive electrode plate, the battery has higher first coulombic efficiency, discharge specific capacity and cycle performance.

[0009] In a first aspect, the present application provides a positive electrode material, comprising: a lithium-rich manganese-based positive electrode active material, and a coating layer covering at least a portion of the surface of the lithium-rich manganese-based positive electrode active material, wherein the molecular formula of the lithium-rich manganese-based positive electrode active material is xLi 2-α MnO3·(1-x)Li 1-β Ni a Co b Mn c O 2-γ , where a+b+c=1, 0<α+β≤0.2, 0<γ≤0.1, 0 <x<1;

[0010] The coating layer satisfies the following formula 1 and formula 2: 0.5×10 -3 S / cm≤T≤5×10 -3 S / cm Formula 1, H≤10 -9 S / cm Formula 2,

[0011] Wherein, T is the ionic conductivity of the coating layer, and H is the electronic conductivity of the coating layer.

[0012] Furthermore, the coating layer includes a halide solid electrolyte material.

[0013] Furthermore, the chemical composition of the halide solid electrolyte material is Li d MX e , wherein M is one or more of Ho, Y, Er, and Yb, and X is Cl or Br; <d≤10,1≤e≤13。

[0014] Furthermore, the coating layer has a thickness of nanometer scale, preferably 5-80 nm.

[0015] Furthermore, the coating layer accounts for 0.1%-0.5% by mass in the positive electrode material.

[0016] Furthermore, the coating layer is dense and free of pores or contains micropores with a pore diameter of no more than 5 nm.

[0017] Furthermore, the specific surface area of ​​the positive electrode material is 0.5-1.3m 2 / g;

[0018] And / or, the size of a single crystal grain of the positive electrode material is 0.7-1.5 μm, and the particle size of the positive electrode material is 4-6 μm.

[0019] In a second aspect, the present application provides a method for preparing the above-mentioned positive electrode material, comprising the following steps:

[0020] 1) Mixing an oxide of M, an ammonium salt, a lithium salt, and a HX solution, stirring at 20-90° C. to obtain a mixed solution with a pH of 1-3; wherein M is one or more of Ho, Y, Er, and Yb, and X is Cl or Br;

[0021] 2) immersing the lithium-rich manganese-based material in the mixed solution, allowing it to stand for 1-5 minutes, and drying it to obtain a precursor;

[0022] 3) Under a protective atmosphere, the precursor is heated to 400-600° C. at a heating rate of 1-10° C. / min and kept at this temperature for 4-6 hours to obtain the positive electrode material.

[0023] Furthermore, the general formula of the lithium-rich manganese-based material is xLi2MnO3·(1-x)LiNi a Co b Mn c O 2， Among them, a+b+c=1, 0≤a≤1, 0≤b≤1, 0≤c≤1, 0<x<1.

[0024] Furthermore, the solid-liquid ratio of the lithium-rich manganese-based material and the mixed solution is (50-100) g: (0.1-1) L.

[0025] In a third aspect, the present application provides a positive electrode plate, comprising a positive electrode active layer and a current collector; the positive electrode active layer comprises the above-mentioned positive electrode material, a sulfide solid electrolyte, a conductive agent and a binder.

[0026] In a fourth aspect, the present application provides an all-solid-state battery, comprising the above-mentioned positive electrode plate.

[0027] The positive electrode material provided in the present application solves the problem of low first coulombic efficiency of lithium-rich manganese-based positive electrode materials, while reducing the possibility of generating a space charge layer and an inert interface layer when the lithium-rich manganese-based positive electrode material contacts the sulfide solid electrolyte, thereby improving the migration efficiency of the interface ions and the stability of the positive electrode material. Therefore, it is beneficial to simultaneously improve the first coulombic efficiency, discharge specific capacity and cycle performance of the all-solid-state battery system. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0029] FIG1 is a SEM image of the lithium-rich manganese-based positive electrode active material of Example 1 at a magnification of 50,000;

[0030] FIG2 is a SEM image of the positive electrode material of Example 1 at a magnification of 50,000;

[0031] FIG3 is a SEM image of the positive electrode material of Comparative Example 1 at a magnification of 50,000;

[0032] FIG4 is a SEM image of the lithium-rich manganese-based positive electrode active material of Example 1 at a magnification of 9000; FIG5 is a SEM image of the positive electrode material of Example 1 at a magnification of 9000. DETAILED DESCRIPTION

[0033] To enable those skilled in the art to better understand the solutions of the present application, the present application is further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present application. The examples cited are only used to explain the present application and do not limit the scope of the present application. Based on the embodiments of the present application, all other implementation methods obtained by those of ordinary skill in the art without making creative efforts are within the scope of protection of this application.

[0034] In order to solve the low coulombic efficiency of lithium-rich manganese-based positive electrode materials while reducing the interfacial reaction between lithium-rich manganese-based positive electrode materials and sulfide solid electrolytes, this application adopts the following technical solutions:

[0035] On the one hand, the present application provides a positive electrode material, comprising: a lithium-rich manganese-based positive electrode active material, and a coating layer covering at least a portion of the surface of the lithium-rich manganese-based positive electrode active material, wherein the molecular formula of the lithium-rich manganese-based positive electrode active material is xLi 2-α MnO3·(1-x)Li 1-β Ni a Co b Mn c O 2-γ , where a+b+c=1, 0<α+β≤0.2, 0<γ≤0.1, 0 <x<1;

[0036] The coating layer satisfies the following formula 1 and formula 2: 0.5×10 -3 S / cm≤T≤5×10 -3 S / cm Formula 1,

[0037] H≤10 -9 S / cm Formula 2,

[0038] Wherein, T is the ionic conductivity of the coating layer, and H is the electronic conductivity of the coating layer.

[0039] It should be noted that the molecular formula of the lithium-rich manganese-based positive electrode active material is basically the same as that of the existing conventional lithium-rich manganese-based material, the main difference being the presence of lithium defects and oxygen defects. The molecular formula of the lithium-rich manganese-based positive electrode active material is xLi 2-α MnO3·(1-x)Li 1-β Nia Co b Mn c O 2-γ， Where a+b+c=1, 0<α+β≤0.2, 0<γ≤0.1. It can be understood that 0≤a≤1, 0≤b≤1, 0≤c≤1, and a+b+c=1, with α+β representing the lithium defect of the entire material system. For example, the degree of lithium defect can be determined by conventional detection methods such as ICP, while the degree of oxygen defect can be calculated based on charge conservation.

[0040] In addition, the T value and H value of the present application are obtained by testing the ionic conductivity and electronic conductivity of the coating material consistent with the above-mentioned coating layer. For example, a coating material consistent with the coating layer is first prepared, or the coating layer material is physically peeled off; and then the T value and H value of the coating material are tested.

[0041] Exemplarily, the T value test method of the coating material is: the ionic conductivity is tested by the AC impedance method. For example, the following method can be used: 200 mg of the coating material is weighed and poured into a mold battery with a diameter of 10 mm, and then the pressure is maintained at 3 tons for 10 minutes, and the thickness of the electrolyte membrane after pressurization is measured. Then, the mold battery is placed in an oven at 25°C and kept warm for more than 2 hours to ensure the consistency of the test temperature, and then connected to the electrochemical workstation for AC impedance testing. The test frequency is 1 Hz-1×10 6 Hz. Based on the AC impedance value obtained from the test, the thickness and area of ​​the electrolyte sheet combined with the ionic conductivity formula (σ = L / RS, σ is the ionic conductivity, L is the thickness of the electrolyte sheet, S is the area of ​​the electrolyte sheet, and R is the ionic resistance obtained from the test), the ionic conductivity can be obtained.

[0042] The H value test method of the coating material is: the electronic conductivity is tested by the DC polarization method. For example, the following method can be used: weigh 200 mg of the coating material and pour it into a mold battery with a diameter of 10 mm, then maintain the pressure at 3 tons for 10 minutes, measure the thickness of the electrolyte membrane after pressurization, and then put the mold battery into a 25°C oven for more than 2 hours to ensure the consistency of the test temperature, and then connect the electrochemical workstation for DC polarization test, set the test bias to 0.1V, and obtain the electronic resistance based on the current obtained from the test. Combined with the thickness and area of ​​the electrolyte sheet, substitute it into the conductivity formula (σ=L / RS, σ is the electronic conductivity, L is the thickness of the electrolyte sheet, S is the area of ​​the electrolyte sheet, and R is the electronic resistance) to obtain the electronic conductivity.

[0043] The reason why the cathode material provided by this application has a high initial Coulomb efficiency and discharge specific capacity is as follows: First, the above-mentioned lithium-rich manganese-based cathode active material has certain lithium defects. This defective lithium-rich manganese-based cathode active material has a high ability to release lithium ions, which is beneficial to improving the initial Coulomb efficiency and discharge specific capacity of the lithium-rich manganese-based cathode active material. At the same time, certain lithium defects can also alleviate the irreversible phase change under high voltage caused by the large amount of lithium ion release during charge and discharge, which is beneficial to maintaining the crystal structure stability of the cathode material and alleviating metal dissolution, so that the cathode material has both high specific capacity and cycle stability. Second, compared with sulfide solid electrolyte, the traditional lithium-rich manganese-based cathode active material has a high electronic conductivity, while the sulfide solid electrolyte is a single lithium ion conductor. When the traditional lithium-rich manganese-based cathode active material comes into contact with the sulfide solid electrolyte, due to the large chemical potential difference of lithium ions between the two, lithium ions will move from the sulfide solid electrolyte side to the cathode active material side, forming a space charge layer between the electrode and the electrolyte. Since the cathode active material has both electronic and ionic conductivity, electrons can eliminate the lithium ion concentration gradient on the electrode side, so that the space charge layer on the electrode side disappears. However, for the lithium ion chemical potential on the sulfide electrolyte side to reach equilibrium, it will inevitably continue to move towards the cathode direction, and the space charge layer will continue to form, eventually resulting in a lithium-deficient layer on the electrolyte side, forming a very large interfacial resistance. In this application, by introducing a halide coating layer with ionic conductivity and almost insulating electrons between the defective lithium-rich manganese-based cathode active material and the solid electrolyte, two new interfaces can be formed, namely the electrode / halide layer interface and the solid electrolyte / halide layer interface, which can effectively inhibit the generation of the space charge layer. At the same time, due to the emergence of the new interface, it avoids the side reaction caused by the direct contact between the lithium-rich manganese-based cathode active material and the sulfide solid electrolyte with a low voltage window, and improves the migration efficiency of interfacial ions, which can effectively improve the initial Coulomb efficiency and discharge specific capacity of the battery system.

[0044] In a preferred embodiment, the coating layer includes a halide solid electrolyte material.

[0045] In a specific embodiment, the chemical composition of the halide solid electrolyte material is Li d MX e , where M is one or more of Ho, Y, Er, Yb, and X is Cl or Br; 0 < d ≤ 10, 1 ≤ e ≤ 13. Among them, the chemical composition of the halide solid electrolyte material determines the ionic conductivity and electronic conductivity of the coating layer. The halide solid electrolyte material within the above-mentioned embodiment range can meet the requirements of high ionic conductivity of this application.

[0046] In a preferred embodiment, X is Cl, wherein the coating layer of the chloride solid electrolyte material helps to further improve the stability of the positive electrode material, thereby further improving the cycle stability of the battery system.

[0047] In a preferred embodiment, the coating layer has a thickness of nanometer scale, preferably 5-80 nm.

[0048] The thickness of the coating layer can be measured using conventional testing instruments, for example, by observation and measurement using a high-resolution transmission electron microscope (HRTEM); illustratively, the thickness of the coating layer includes but is not limited to any value of 10 nm, 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, 65 nm, 70 nm, 75 nm, etc.

[0049] In a preferred embodiment, the coating layer accounts for 0.1%-0.5% by mass in the positive electrode material.

[0050] It can be understood that the mass ratio of the coating layer in the positive electrode material can reflect the degree to which the coating layer coats the positive electrode material. If the mass ratio of the coating layer in the positive electrode material is too low, the first coulombic efficiency and discharge specific capacity of the positive electrode material will not be improved much. On the contrary, if the mass ratio of the coating layer in the positive electrode material is too high, it will have an adverse effect on the conductivity of the positive electrode material. In a preferred embodiment, the coating layer is dense and has no holes or has micropores with a pore size of no more than 5nm. Among them, the coating layer is dense and has no holes or has micropores, which can achieve a relatively tight and uniform coating of the coating layer on the surface of the lithium-rich manganese-based positive active material, which is not only conducive to further suppressing the generation of the space charge layer, but also avoids the direct contact of the lithium-rich manganese-based positive active material with the sulfide solid electrolyte to produce side reactions, and the denser coating layer is also conducive to suppressing the expansion phenomenon of the positive electrode material, thereby helping to improve the stability and safety of the all-solid-state battery system. The mass proportion of the coating layer in the positive electrode material can reflect the degree to which the coating layer covers the positive electrode material. If the mass proportion of the coating layer in the positive electrode material is too low, the first coulombic efficiency and discharge specific capacity of the positive electrode material will not be greatly improved. Conversely, if the mass proportion of the coating layer in the positive electrode material is too high, it will have an adverse effect on the conductivity of the positive electrode material.

[0051] In a preferred embodiment, the specific surface area of ​​the positive electrode material is 0.5-1.3 m 2 / g;

[0052] And / or, the size of a single crystal grain of the positive electrode material is 0.7-1.5 μm, and the particle size of the positive electrode material is 4-6 μm.

[0053] It can be understood that the traditional lithium-rich manganese-based material is a polycrystalline structure formed by multiple grains, so the positive electrode material of the present application is also a polycrystalline structure. The size of the above-mentioned single grain refers to the maximum size of the grain in the range of 0.7-1.5μm, and the particle size of the positive electrode material refers to the maximum size of the positive electrode material with a polycrystalline structure in the range of 4-6μm. As for the size of a single grain and the particle size of the positive electrode material, they can be observed and measured by SEM. For example: use SEM to obtain the surface morphology of the positive electrode material, set the magnification of the picture to 9000 times, take a test point in the picture, and measure the particle size of the positive electrode material in the test point. Then set the magnification of the picture to 50,000 times, take a test point in the picture, and measure the size of a single grain in the test point.

[0054] The positive electrode material of the above-mentioned size can further ensure the kinetic performance and specific capacity of the positive electrode material; and the positive electrode material with a specific surface area within the above-mentioned range can further ensure the cyclability of the battery without affecting its rate performance. The reason is that: the positive electrode material has a larger specific surface area to ensure the rate performance of the battery, but an excessively large specific surface area will lead to a low compaction density, which is not conducive to its application in high energy density systems.

[0055] In a preferred embodiment, the above-mentioned positive electrode material is prepared by a method comprising the following steps:

[0056] 1) Mixing an oxide of M, an ammonium salt, a lithium salt, and a HX solution, stirring at 20-90° C. to obtain a mixed solution with a pH of 1-3; wherein M is one or more of Ho, Y, Er, and Yb, and X is Cl or Br;

[0057] 2) immersing the lithium-rich manganese-based material in the mixed solution, allowing it to stand for 1-5 minutes, and drying it to obtain a precursor;

[0058] 3) Under a protective atmosphere, the precursor is heated to 400-600° C. at a heating rate of 1-10° C. / min and kept at this temperature for 4-6 hours to obtain the positive electrode material.

[0059] Illustratively, the ammonium salt may be ammonium chloride, ammonium nitrate, etc., and the lithium salt may be lithium carbonate, lithium nitrate, lithium chloride, etc.

[0060] In a second aspect, the present application provides a method for preparing the above-mentioned positive electrode material, comprising the following steps:

[0061] 1) Mixing an oxide of M, an ammonium salt, a lithium salt, and a HX solution, stirring at 20-90° C. to obtain a mixed solution with a pH of 1-3; wherein M is one or more of Ho, Y, Er, and Yb, and X is Cl or Br;

[0062] 2) immersing the lithium-rich manganese-based material in the mixed solution, allowing it to stand for 1-5 minutes, and drying it to obtain a precursor;

[0063] 3) Under a protective atmosphere, the precursor is heated to 400-600° C. at a heating rate of 1-10° C. / min and kept at this temperature for 4-6 hours to obtain the positive electrode material.

[0064] Through research, the present application found that the above preparation process can ensure that the defectivity of the lithium-rich manganese-based positive electrode active material is within an appropriate range and the coating effect of the coating layer is better, thereby ensuring that the all-solid-state battery system has excellent first coulombic efficiency, discharge specific capacity and cycle performance. If the standing time of step 2) is too long, or the pH of the mixed solution is not within the above range, or the preparation process is changed to: acid etching first, and then using a neutral mixed solution containing a halide solid electrolyte precursor to liquid-phase coat the acid-etched lithium-rich manganese-based material, the defectivity of the lithium-rich manganese-based positive electrode active material and the coating effect of the coating layer cannot be guaranteed.

[0065] In the above preparation method, the oxide of M, ammonium salt, and lithium salt are dissolved in the acidic HX solution. The chemical reaction that occurs at this time is exemplified by Ho2O3, NH4Cl, Li2CO3, and HCl. The chemical reaction equation is:

[0066] Ho2O3+3Li2CO3+(6+n)HCl+6NH4Cl→2(NH4)3[HoCl6]+6LiCl+6H2O+3CO2(↑); However, due to the excess of HCl solution in nm mol, the mixture obtained after the reaction contains a halide solid electrolyte precursor, and the liquid is weakly acidic. At this time, adding a lithium-rich manganese-based positive electrode active material to the acidic mixture will increase defects on its surface and wash away excess Li + , forming Li + The defect structure of lithium-rich manganese-based positive electrode material, at the same time, the halide solid electrolyte precursor in the mixed solution adheres to the surface of the lithium-rich manganese-based positive electrode active material. After filtration, drying, and vacuum sintering, a thin halide solid electrolyte coating layer is in situ formed on the surface of the lithium-rich manganese-based positive electrode active material. The chemical reaction equation is:

[0067] (NH4)3[HoCl6]+3LiCl→Li3HoCl6+3NH3(↑)+3HCl(↑); The Li3HoCl6 coating helps to improve the low ion transport capacity within the lithium-rich manganese-based positive electrode active material, while effectively suppressing the volume expansion of the positive electrode material. The pH of the mixed solution and the standing time affect the defectivity of the lithium-rich manganese-based positive electrode active material, while the sintering conditions of the precursor affect the ionic conductivity and density of the coating. If the sintering temperature is too high or the heating rate is too fast, the ionic conductivity of the coating will decrease. Moreover, due to the rapid volatilization of NH3 and HCl gases, the pore size of the coating will increase, and its coating structure will no longer be dense.

[0068] Illustratively, the ammonium salt may be ammonium chloride, ammonium bromide, etc., and the lithium salt may be lithium carbonate, lithium chloride, lithium bromide, etc.

[0069] It is understood that the lithium-rich manganese-based material in step 2) is a traditional lithium-rich manganese-based material without lithium defects, which can be purchased commercially or prepared according to conventional methods. For example, the general formula of the lithium-rich manganese-based material is xLi2MnO3·(1-x)LiNi a Co b Mn c O 2， Among them, a+b+c=1, 0≤a≤1, 0≤b≤1, 0≤c≤1, 0<x<1.

[0070] As for the solid-liquid ratio of the lithium-rich manganese-based material and the mixed liquid in step 2), this application does not specifically limit it. The technicians adjust it according to the coating amount, coating thickness and degree of manufacturing defects of the required coating layer. For example, the solid-liquid ratio is 50-100g:0.1-1L.

[0071] In a specific embodiment, the method further includes a step of crushing the positive electrode material, the purpose of which is only to disperse the agglomerates sintered into large blocks.

[0072] In a third aspect, the present application provides a positive electrode plate, comprising a positive electrode active layer and a current collector; the positive electrode active layer comprises the above-mentioned positive electrode material, a sulfide solid electrolyte, a conductive agent and a binder.

[0073] For example, the material of the current collector can be at least one of aluminum foil and nickel foil; the conductive agent can be at least one of carbon black, acetylene black, graphene, Ketjen black, and carbon fiber; the binder can be at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polymer containing ethylene oxide, polyvinyl pyrrolidone, and polyurethane; the sulfide solid electrolyte can be Li7P3S 11, β-Li3PS4, Li6PS5Cl, Li6PS5Br, Li7P2S8I, Li4PS4I, Li6PS5Cl x Br 1-x 、Li6PS5Cl y I 1-y 、Li6PS5Br z I 1-z One of the following, where x, y, z = 0 to 1.

[0074] Illustratively, the mass ratio of the positive electrode material, the sulfide solid electrolyte, the conductive agent, and the binder may be (50-90):(50-10):(0.1-2):(0.1-10).

[0075] Exemplarily, the preparation method of the above-mentioned positive electrode plate may include the following steps: weighing the above-mentioned positive electrode material, sulfide solid electrolyte (Li6PS5Cl), and conductive agent (VGCF) in a mass ratio of 85:15:1 into a mortar and manually mixing for more than 30 minutes to obtain a mixture, then adding 1% by mass (1% of the above-mentioned mixture) of polytetrafluoroethylene particles (PTFE), heating on a heating table at 150°C for 5 minutes, and then manually grinding into a film to pre-fiberize the PTFE, and then heating and rolling the obtained film on a calender at a rolling temperature of 100°C. The thickness of the obtained film is adjusted by controlling the gap width between the two hot pressing rollers, and repeatedly rolling to obtain a formed composite positive electrode material film with a thickness of 40-60 μm. The composite positive electrode material film is calendered to the surface of a 15 μm thick Al foil current collector to obtain a positive electrode plate.

[0076] In a fourth aspect, the present application provides an all-solid-state battery, comprising the above-mentioned positive electrode plate.

[0077] Exemplarily, the all-solid-state battery further comprises a sulfide solid electrolyte membrane and a negative electrode, wherein the negative electrode can be at least one of a lithium metal alloy, lithium metal, graphite, a Si-C composite negative electrode, and metal indium; the material of the sulfide solid electrolyte membrane can be Li7P3S 11 , β-Li3PS4, Li6PS5Cl, Li6PS5Br, Li7P2S8I, Li4PS4I, Li6PS5Cl x Br 1-x 、Li6PS5Cl y I 1-y 、Li6PS5Br z I 1-z At least one of the following, where x, y, 0 <z<1。

[0078] The present application is further described below with reference to specific embodiments:

[0079] Example 1

[0080] This example provides a positive electrode material, comprising: a lithium-rich manganese-based positive electrode active material, and a coating layer covering at least a portion of the surface of the lithium-rich manganese-based positive electrode active material, wherein the lithium-rich manganese-based positive electrode active material has a lithium-deficient crystal structure; the ionic conductivity of the coating layer is 1.20×10 -3 S / cm, and the electronic conductivity of the coating layer is 4.31×10 -10 S / cm.

[0081] The preparation method thereof comprises the following steps:

[0082] 1) Dissolution: 0.1 mol, 0.3 mol, and 0.6 mol of the raw materials Ho2O3, Li2CO3, and NH4Cl were dissolved in 0.5 L of 2.41 mol / L HCl solution and heated with stirring for 1 h at a speed of 400 rpm to obtain a mixed solution containing a halide solid electrolyte precursor (pH 1.97);

[0083] 2) Mixing: 50g lithium-rich manganese-based material (molecular formula: 0.5Li2MnO3·0.5Li Ni 0.7 Mn 0.3 O2) was placed in 0.1 L of the above mixed solution and allowed to stand for 2 minutes;

[0084] 3) Drying: filtering out the lithium-rich manganese-based positive electrode active material with the halide solid electrolyte precursor and drying it in an oven at 80° C. to obtain a lithium-rich manganese-based positive electrode active material coated with the halide solid electrolyte precursor;

[0085] 4) Sintering process: The lithium-rich manganese-based cathode active material coated with the halide solid electrolyte precursor was sintered in a tube furnace under an Ar atmosphere at a heating rate of 3°C / min from room temperature to a sintering temperature of 500°C for 4 hours to obtain the cathode material;

[0086] 5) Material crushing: The sintered positive electrode material is ground in a crusher to obtain the final product. The ionic conductivity and electronic conductivity of the coating layer of this embodiment are tested by the following steps:

[0087] S1. Prepare the constituent materials of the coating layer. The process is similar to the preparation of the positive electrode material in this example, except that step 2) is omitted. That is, the mixed solution is directly dried in an oven at 80° C. and then sintered.

[0088] S2. Ionic conductivity test: Weigh 200 mg of the coating material and pour it into a mold battery with a diameter of 10 mm. Then, maintain the pressure at 3 tons for 10 minutes. Measure the thickness of the electrolyte membrane after pressurization. Then, place the mold battery in a 25°C oven for more than 2 hours to ensure the consistency of the test temperature. Then, connect it to the electrochemical workstation for AC impedance testing. The test frequency is 1 Hz-1×10 6 Hz. Based on the AC impedance value obtained from the test, the thickness and area of ​​the electrolyte sheet combined with the ionic conductivity formula (σ=L / RS, σ is the ionic conductivity, L is the thickness of the electrolyte sheet, S is the area of ​​the electrolyte sheet, and R is the ionic resistance obtained from the test), the ionic conductivity can be obtained;

[0089] S3. Electronic conductivity test: Weigh 200 mg of coating material and pour it into a mold battery with a diameter of 10 mm. Then maintain the pressure at 3 tons for 10 minutes, measure the thickness of the pressurized electrolyte membrane, and then place the mold battery in a 25°C oven for more than 2 hours to ensure the consistency of the test temperature. Then connect the electrochemical workstation to perform a DC polarization test, set the test bias to 0.1 V, and obtain the electronic resistance based on the current obtained from the test. Combined with the thickness and area of ​​the electrolyte sheet, substitute it into the conductivity formula (σ=L / RS, σ is the electronic conductivity, L is the thickness of the electrolyte sheet, S is the area of ​​the electrolyte sheet, and R is the electronic resistance) to obtain the electronic conductivity.

[0090] Example 2

[0091] This example provides a positive electrode material, comprising: a lithium-rich manganese-based positive electrode active material, and a coating layer covering at least a portion of the surface of the lithium-rich manganese-based positive electrode active material, wherein the lithium-rich manganese-based positive electrode active material has a lithium-deficient crystal structure; the ionic conductivity of the component material of the coating layer is 1.21×10 -3 S / cm, and the electronic conductivity of the constituent material of the coating layer is 4.30×10 -10 S / cm (test method refers to Example 1).

[0092] The preparation method is basically the same as that of Example 1, except that the concentration of the HCl solution is 2.45 mol / L. The pH of the mixed solution containing the halide solid electrolyte precursor is 1.30.

[0093] Example 3

[0094] This example provides a positive electrode material, comprising: a lithium-rich manganese-based positive electrode active material, and a coating layer covering at least a portion of the surface of the lithium-rich manganese-based positive electrode active material, wherein the lithium-rich manganese-based positive electrode active material has a lithium-deficient crystal structure; the ionic conductivity of the constituent material of the coating layer is 1.19×10 -3S / cm, and the electronic conductivity of the constituent material of the coating layer is 4.32×10 -10 S / cm (test method refers to Example 1).

[0095] The preparation method is basically the same as that of Example 1, except that the concentration of the HCl solution is 2.50 mol / L. The pH of the mixed solution containing the halide solid electrolyte precursor is 1.

[0096] Example 4

[0097] This example provides a positive electrode material, comprising: a lithium-rich manganese-based positive electrode active material, and a coating layer covering at least a portion of the surface of the lithium-rich manganese-based positive electrode active material, wherein the lithium-rich manganese-based positive electrode active material has a lithium-deficient crystal structure; the ionic conductivity of the component material of the coating layer is 1.04×10 -3 S / cm, and the electronic conductivity of the constituent material of the coating layer is 2.62×10 -10 S / cm (test method refers to Example 1).

[0098] The preparation method is basically the same as that in Example 1, except that Ho2O3 is replaced by Y2O3.

[0099] Example 5

[0100] This example provides a positive electrode material, comprising: a lithium-rich manganese-based positive electrode active material, and a coating layer covering at least a portion of the surface of the lithium-rich manganese-based positive electrode active material, wherein the lithium-rich manganese-based positive electrode active material has a lithium-deficient crystal structure; the ionic conductivity of the constituent material of the coating layer is 1.16×10 -3 S / cm, and the electronic conductivity of the constituent material of the coating layer is 4.23×10 -10 S / cm (test method refers to Example 1).

[0101] The preparation method is basically the same as that in Example 1, except that the standing time in step 2) is 1 minute.

[0102] Example 6

[0103] This example provides a positive electrode material, comprising: a lithium-rich manganese-based positive electrode active material, and a coating layer covering at least a portion of the surface of the lithium-rich manganese-based positive electrode active material, wherein the lithium-rich manganese-based positive electrode active material has a lithium-deficient crystal structure; the ionic conductivity of the component material of the coating layer is 1.15×10 -3 S / cm, and the electronic conductivity of the constituent material of the coating layer is 4.22×10 -10 S / cm (test method refers to Example 1).

[0104] The preparation method is basically the same as that in Example 1, except that the standing time in step 2) is 5 minutes.

[0105] Example 7

[0106] This example provides a positive electrode material, comprising: a lithium-rich manganese-based positive electrode active material, and a coating layer covering at least a portion of the surface of the lithium-rich manganese-based positive electrode active material, wherein the lithium-rich manganese-based positive electrode active material has a lithium-deficient crystal structure; the ionic conductivity of the component material of the coating layer is 1.18×10 -3 S / cm, and the electronic conductivity of the constituent material of the coating layer is 4.26×10 -10 S / cm (test method refers to Example 1).

[0107] The preparation method is basically the same as that of Example 1, except that the volume of the HCl solution in step 1) is changed to 0.1 L (keeping the pH value consistent with that of Example 1).

[0108] Example 8

[0109] This example provides a positive electrode material, comprising: a lithium-rich manganese-based positive electrode active material, and a coating layer covering at least a portion of the surface of the lithium-rich manganese-based positive electrode active material, wherein the lithium-rich manganese-based positive electrode active material has a lithium-deficient crystal structure; the ionic conductivity of the constituent material of the coating layer is 1.16×10 -3 S / cm, and the electronic conductivity of the constituent material of the coating layer is 4.14×10 -10 S / cm (test method refers to Example 1).

[0110] The preparation method is basically the same as that of Example 1, except that the molecular formula of the lithium-rich manganese-based material in step 2) is 0.3Li2MnO3·0.7Li Ni 0.7 Mn 0.3 O2.

[0111] Example 9

[0112] This example provides a positive electrode material, comprising: a lithium-rich manganese-based positive electrode active material, and a coating layer covering at least a portion of the surface of the lithium-rich manganese-based positive electrode active material, wherein the lithium-rich manganese-based positive electrode active material has a lithium-deficient crystal structure; the ionic conductivity of the component material of the coating layer is 1.18×10 -3 S / cm, and the electronic conductivity of the constituent material of the coating layer is 4.23×10 -10 S / cm (test method refers to Example 1).

[0113] The preparation method is basically the same as that of Example 1, except that the molecular formula of the lithium-rich manganese-based material in step 2) is 0.7Li2MnO3·0.3Li Ni 0.7 Mn 0.3 O2.

[0114] Example 10

[0115] This example provides a positive electrode material, comprising: a lithium-rich manganese-based positive electrode active material, and a coating layer covering at least a portion of the surface of the lithium-rich manganese-based positive electrode active material, wherein the lithium-rich manganese-based positive electrode active material has a lithium-deficient crystal structure; the ion conductivity of the component material of the coating layer is 3.72×10 -3 S / cm, and the electronic conductivity of the constituent material of the coating layer is 4.03×10 -10 S / cm (test method refers to Example 1).

[0116] The preparation method is basically the same as that of Example 1, except that the Ho2O3 in step 1) is replaced by Er2O3, and the HCl solution is replaced by HBr solution (the pH remains unchanged).

[0117] Example 11

[0118] This example provides a positive electrode material, comprising: a lithium-rich manganese-based positive electrode active material, and a coating layer covering at least a portion of the surface of the lithium-rich manganese-based positive electrode active material, wherein the lithium-rich manganese-based positive electrode active material has a lithium-deficient crystal structure; the ionic conductivity of the component material of the coating layer is 3.93×10 -3 S / cm, and the electronic conductivity of the constituent material of the coating layer is 4.68×10 -10 S / cm (test method refers to Example 1).

[0119] The preparation method is basically the same as that in Example 1, except that the Ho2O3 in step 1) is replaced by Yb2O3, and the HCl solution is replaced by HBr solution (the pH remains unchanged).

[0120] Example 12

[0121] This example provides a positive electrode material, comprising: a lithium-rich manganese-based positive electrode active material, and a coating layer covering at least a portion of the surface of the lithium-rich manganese-based positive electrode active material, wherein the lithium-rich manganese-based positive electrode active material has a lithium-deficient crystal structure; the ionic conductivity of the component material of the coating layer is 0.54×10 -3 S / cm, and the electronic conductivity of the constituent material of the coating layer is 4.21×10 -10 S / cm (test method refers to Example 1).

[0122] The preparation method is basically the same as that in Example 1, except that the Ho2O3 in step 1) is replaced by Dy2O3, and the HCl solution is replaced by HBr solution (pH remains unchanged).

[0123] Comparative Example 1

[0124] This example provides a positive electrode material, comprising: a lithium-rich manganese-based positive electrode active material, and a coating layer covering at least a portion of the surface of the lithium-rich manganese-based positive electrode active material, wherein the lithium-rich manganese-based positive electrode active material has not been modified; the ionic conductivity of the constituent material of the coating layer is 1.17×10 -3 S / cm, and the electronic conductivity of the constituent material of the coating layer is 4.14×10 -10 S / cm (test method refers to Example 1).

[0125] The preparation method thereof comprises the following steps:

[0126] 1) Dissolution: 0.1 mol, 0.3 mol, and 0.6 mol of the raw materials Ho2O3, Li2CO3, and NH4Cl were dissolved in 0.5 L of 2.41 mol / L HCl solution and heated with stirring for 1 h at a speed of 400 rpm to obtain a mixed solution containing a halide solid electrolyte precursor (pH 1.97);

[0127] 2) Drying: Drying the halide solid electrolyte precursor solution in an oven at 80° C. to obtain a halide solid electrolyte precursor;

[0128] 3) Sintering process: The halide solid electrolyte precursor was sintered in a tube furnace (heating rate of 3°C / min) under an Ar atmosphere at a sintering temperature of 500°C for 4 h.

[0129] 4) Mixing: The halide solid electrolyte powder having a mass corresponding to the in-situ coating and the lithium-rich manganese-based positive electrode active material are mixed uniformly in a high-speed mixer at a speed of 1000 rpm, and then cooled to room temperature to obtain the positive electrode material.

[0130] Comparative Example 2

[0131] This example provides a positive electrode material, comprising: a lithium-rich manganese-based positive electrode active material, and a coating layer covering at least a portion of the surface of the lithium-rich manganese-based positive electrode active material, wherein the lithium-rich manganese-based positive electrode active material has a lithium-deficient crystal structure; the ionic conductivity of the component material of the coating layer is 1.18×10 -3 S / cm, and the electronic conductivity of the constituent material of the coating layer is 4.16×10 -10 S / cm (test method refers to Example 1).

[0132] The preparation method is basically the same as that in Example 1, except that the standing time in step 2) is 20 minutes.

[0133] Comparative Example 3

[0134] This example provides a positive electrode material, comprising: a lithium-rich manganese-based positive electrode active material, and a coating layer covering at least a portion of the surface of the lithium-rich manganese-based positive electrode active material, wherein the lithium-rich manganese-based positive electrode active material has a lithium-deficient crystal structure; the ionic conductivity of the constituent material of the coating layer is 1.17×10 -3 S / cm, and the electronic conductivity of the constituent material of the coating layer is 4.19×10 -10 S / cm (test method refers to Example 1).

[0135] The preparation method is basically the same as that of Example 1, except that the pH of the mixed solution containing the halide solid electrolyte precursor is 0.20.

[0136] Comparative Example 4

[0137] This example provides a positive electrode material, comprising: a lithium-rich manganese-based positive electrode active material, and a coating layer covering at least a portion of the surface of the lithium-rich manganese-based positive electrode active material, wherein the lithium-rich manganese-based positive electrode active material has a lithium-deficient crystal structure; the ionic conductivity of the component material of the coating layer is 5.24×10 -5 S / cm, and the electronic conductivity of the constituent material of the coating layer is 2.16×10 -10 S / cm.

[0138] The preparation method is basically the same as that of Example 1 (the testing method refers to Example 1), except that the sintering temperature is 800°C.

[0139] Comparative Example 5

[0140] The positive electrode material provided in this example is a lithium-rich manganese-based material (molecular formula: 0.5Li2MnO3·0.5Li Ni 0.7 Mn 0.3 O2).

[0141] The following tests were performed on the positive electrode materials of the embodiments and comparative examples:

[0142] 1. Observe the morphology of the cathode materials of each embodiment by HRTEM;

[0143] 2. The morphology of the positive electrode materials of each embodiment and comparative example before and after coating was observed by SEM. The microscopic morphologies of the positive electrode material of embodiment 1 before and after coating and the positive electrode material of comparative example 1 are shown in Figures 1 to 5 ;

[0144] 3. The general formula of the lithium-rich manganese-based positive electrode active material in each embodiment or comparative example is xLi 2-α MnO3·(1-x)Li 1- β Ni a Co b Mn c O2-γ， Wherein, a+b+c=1, 0<α+β≤0.2, 0<γ≤0.1, "α+β" refers to the overall defectivity of lithium in the positive electrode material, "γ" refers to the overall defectivity of oxygen in the positive electrode material, the lithium content of the positive electrode material is determined by ICP, the lithium defectivity is obtained by conversion, and the oxygen defectivity is obtained by calculation;

[0145] 4. Specific surface area: The specific surface area is tested using BET;

[0146] 5. Mass proportion of the coating layer: The mass of the lithium-rich manganese-based material before coating is recorded as X, and the mass of the positive electrode material after being coated with the halide solid electrolyte is recorded as Y. The mass proportion of the coating layer = (YX) / Y.

[0147] At least part of the above test results are summarized in Table 1.

[0148] Table 1: In the table, “-” means that the result was not recorded.

[0149] It can be seen from the HRTEM test results that the thickness of the coating layer in the positive electrode materials of each embodiment is in the range of 5-80 nm, among which the thickness of the coating layer of the positive electrode material of Example 1 is in the range of 20-60 nm.

[0150] As shown in Figures 1-2, before in-situ coating, the surface of the lithium-rich manganese-based material is relatively regular. After in-situ coating, the surface is coated with a dense, substantially pore-free amorphous halide solid electrolyte coating layer. The size of a single grain of the positive electrode material is 0.7-1.5 μm. The positive electrode materials of other embodiments are similar to those of Example 1. As shown in Figure 3, in the mechanical mixing coating of Comparative Example 1, only a small amount of halide solid electrolyte is attached to the positive electrode surface, and the coating is uneven. It can also be seen from Figures 4 and 5 that the surface of the lithium-rich manganese-based positive electrode material is coated with a halide solid electrolyte, and it can be seen that the particle size of the positive electrode material is 4-6 μm. The positive electrode materials of other embodiments are similar to those of Example 1.

[0151] Application Example 1

[0152] The positive electrode materials of the above embodiments and comparative examples are used to prepare a positive electrode sheet, comprising the following steps:

[0153] The above-mentioned positive electrode materials, sulfide solid electrolyte (Li6PS5Cl), and conductive agent (VGCF) were weighed into a mortar in a mass ratio of 85:15:1 and manually mixed for more than 30 minutes to obtain a mixture. Subsequently, 1% by mass (accounting for 1% of the above-mentioned mixture) of polytetrafluoroethylene particles (PTFE) was added, and the mixture was heated at 150°C on a heating table for 5 minutes and then manually ground into a film to pre-fiberize the PTFE. The obtained film was then heated and rolled on a calender at a temperature of 100°C. The thickness of the obtained film was adjusted by controlling the gap width between the two hot pressing rollers. Repeated rolling was performed to obtain a formed composite positive electrode material film with a thickness of 40-60 μm. The composite positive electrode material film was calendered to the surface of a 15 μm thick Al foil current collector to obtain a positive electrode sheet.

[0154] Application Example 2

[0155] The preparation of an all-solid-state battery using the above-mentioned positive electrode sheet includes the following steps:

[0156] The above-mentioned positive electrode sheet is die-cut into a disc with a diameter of 8 mm, and then stacked and cold-pressed with the Li6PS5Cl sulfide solid electrolyte membrane and LiIn negative electrode in a glove box filled with Ar atmosphere to obtain an all-solid-state battery.

[0157] Performance testing:

[0158] The following electrical properties of each battery assembled in Application Example 2 were tested separately (results are shown in Table 2):

[0159] First coulombic efficiency, first cycle charge capacity, first cycle discharge capacity, capacity retention rate: All-solid-state battery is charged at a constant current rate of 0.1C at 25-30℃ to a voltage of 4.2V (vs.Li + / LiIn), the charge capacity at this time is recorded as the first cycle charge capacity, then it is left to stand for 5 minutes, and then discharged at a constant current rate of 0.1C until the voltage reaches 1.4V (vs.LiIn + / LiIn), the discharge capacity at this time is recorded as the first cycle discharge capacity of the battery, the first coulombic efficiency of the battery (%) = first cycle discharge capacity / first cycle charge capacity × 100%; then, charge at a constant current rate of 1C until the voltage reaches 4.2V (vs.LiIn) + / LiIn), the charge capacity at this time is recorded as the first cycle charge capacity, then it is left to stand for 5 minutes, and then discharged at a constant current rate of 1C until the voltage reaches 1.4V (vs.Li + / LiIn), cycle 50 times, record the discharge specific capacity of the 1st cycle and the 50th cycle, and the capacity retention rate = discharge specific capacity of the 50th cycle / discharge specific capacity of the 1st cycle × 100%.

[0160] Table 2:

[0161] As can be seen from Table 2, compared with the traditional unmodified lithium-rich manganese-based material of Comparative Example 5, the lithium-rich manganese-based positive electrode active material of the embodiment significantly improves the first coulombic efficiency, discharge specific capacity and cycle performance of the all-solid-state battery system.

[0162] Furthermore, compared with the lithium-rich manganese-based positive electrode active material of Comparative Example 1 using a non-lithium defect crystal structure, the lithium-rich manganese-based positive electrode active material of the embodiment significantly improves the first coulombic efficiency of the all-solid-state battery system while ensuring relatively high discharge specific capacity and cycle performance.

[0163] Furthermore, compared with Comparative Examples 2-4, the lithium-rich manganese-based positive electrode active material of the embodiment has a suitable defect degree and / or ionic conductivity, which significantly improves the discharge specific capacity of the all-solid-state battery system while ensuring relatively high initial coulombic efficiency and cycle performance.

[0164] Furthermore, it can be seen from Examples 1 and 12 that changing the composition of the halide solid electrolyte material of the coating layer can change the ionic conductivity of the coating layer, thereby affecting the first coulombic efficiency, discharge specific capacity and cycle performance of the all-solid-state battery system.

[0165] Furthermore, it can be seen from Examples 1-3 that the acid concentration in the solution has a significant effect on the first efficiency and discharge specific capacity of the battery.

[0166] Furthermore, it can be seen from Examples 1, 5, 6 and Comparative Examples 2-3 that if the lithium-rich cathode material is immersed in the acidic precursor solution for too long or the acid concentration is too high, the discharge specific capacity of the cathode material will be reduced.

[0167] Furthermore, it can be seen from Examples 1 and 7 that a large proportion of the coating layer is not conducive to the specific capacity of the lithium-rich manganese-based positive electrode material.

[0168] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some or all of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A positive electrode material, characterized in that include: A lithium-rich manganese-based positive electrode active material and a coating layer covering at least a portion of the surface of the lithium-rich manganese-based positive electrode active material, wherein the molecular formula of the lithium-rich manganese-based positive electrode active material is xLi 2- α MnO3·(1-x)Li 1-β Ni a Co b Mn c O 2-γ , where a+b+c=1, 0<α+β≤0.2, 0<γ≤0.1, 0 <x<1; The coating layer satisfies the following formula 1 and formula 2: 0.5×10 -3 S / cm≤T≤5×10 -3 S / cm Formula 1, H≤10 -9 S / cm Formula 2, Wherein, T is the ionic conductivity of the coating layer, and H is the electronic conductivity of the coating layer.

2. The positive electrode material according to claim 1, characterized in that The coating layer includes a halide solid electrolyte material.

3. The positive electrode material according to claim 2, characterized in that The chemical composition of the halide solid electrolyte material is Li d MX e , wherein M is one or more of Ho, Y, Er, and Yb, and X is Cl or Br; <d≤10,1≤e≤13。 4. The positive electrode material according to claim 2 or 3, characterized in that The coating layer has a thickness of nanometer level.

5. The positive electrode material according to claim 4, characterized in that The thickness of the coating layer is 5-80 nm.

6. The positive electrode material according to claim 2 or 3, characterized in that The coating layer accounts for 0.1% to 0.5% by mass in the positive electrode material.

7. The positive electrode material according to any one of claims 1 to 6, characterized in that The coating layer is dense and free of pores or has micropores with a pore diameter of no more than 5 nm.

8. The positive electrode material according to any one of claims 1 to 7, characterized in that The specific surface area of ​​the positive electrode material is 0.5-1.3m 2 / g; And / or, the size of a single crystal grain of the positive electrode material is 0.7-1.5 μm, and the particle size of the positive electrode material is 4-6 μm.

9. A method for preparing the positive electrode material according to any one of claims 1 to 8, characterized in that: The following steps are involved: 1) Mixing an oxide of M, an ammonium salt, a lithium salt, and a HX solution, stirring at 20-90° C. to obtain a mixed solution with a pH of 1-3; wherein M is one or more of Ho, Y, Er, and Yb, and X is Cl or Br; 2) immersing the lithium-rich manganese-based material in the mixed solution, allowing it to stand for 1-5 minutes, and drying it to obtain a precursor; 3) Under a protective atmosphere, the precursor is heated to 400-600° C. at a heating rate of 1-10° C. / min and kept at this temperature for 4-6 hours to obtain the positive electrode material.

10. The preparation method according to claim 9, characterized in that The general formula of the lithium-rich manganese-based material is xLi2MnO3·(1-x)LiNi a Co b Mn c O 2， Among them, a+b+c=1, 0≤a≤1, 0≤b≤1, 0≤c≤1, 0<x<1.

11. The preparation method according to claim 10, characterized in that: The solid-liquid ratio of the lithium-rich manganese-based material and the mixed liquid is (50-100) g: (0.1-1) L.

12. A positive electrode plate, characterized in that: The invention comprises a positive electrode active layer and a current collector; the positive electrode active layer comprises the positive electrode material according to any one of claims 1 to 8, a sulfide solid electrolyte, a conductive agent and a binder.

13. An all-solid-state battery, characterized in that: Including the positive electrode sheet according to claim 12.

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