Coated microcrystal lithium-rich manganese-based positive electrode material as well as preparation method and application thereof

Abstract

The invention provides a coated microcrystal lithium-rich manganese-based positive electrode material as well as a preparation method and application thereof. The positive electrode material is a lithium-rich manganese-based positive electrode material which is prepared from a lithium-rich manganese-based precursor and has primary particles formed in situ and secondary spheres with surface coatings. The positive electrode material has a unique core-shell structure, the core is a microcrystal lithium-rich material, the shell is a nanoscale solid electrolyte layer, and the shell layer coats primary particles and secondary spheres at the same time; the structure effectively inhibits the interface side reaction between the positive electrode material and the solid electrolyte, and stabilizes the interface structure; a continuous and short Li and charge transmission path is provided, the interface impedance in an all-solid-state battery is remarkably reduced, and the rate capability and the cycling stability of the material are improved.

Description

Technical Field

[0001] This invention belongs to the field of cathode material technology, and particularly relates to a coated microcrystalline lithium-rich manganese-based cathode material, its preparation method, and its application. Background Technology

[0002] With the increasing global demand for clean energy, lithium-ion batteries, as a highly efficient energy storage device, have been widely used in electric vehicles, portable electronic devices, and other fields. However, traditional lithium-ion batteries use flammable organic liquid electrolytes, posing safety hazards such as leakage, fire, and even explosion, which limits their further development in fields with high safety requirements. Furthermore, the unstable interface between the organic liquid electrolyte and electrode materials can lead to side reactions during battery cycling, causing capacity decay and shortened lifespan.

[0003] All-solid-state batteries use solid electrolytes instead of traditional organic liquid electrolytes, fundamentally solving safety issues such as leakage and flammability, and significantly improving battery safety. Simultaneously, solid electrolytes possess excellent mechanical properties, effectively suppressing lithium dendrite growth and preventing short circuits caused by lithium dendrites piercing the separator, further enhancing battery safety and stability. Furthermore, solid electrolytes exhibit higher thermal stability, enabling operation over a wider temperature range and expanding battery application scenarios. Moreover, all-solid-state batteries can achieve higher energy densities, potentially meeting the urgent demand for high-energy-density batteries in electric vehicles with long driving ranges and large-scale energy storage systems. Therefore, all-solid-state batteries are considered a crucial development direction for next-generation high-safety, high-energy-density batteries, attracting widespread attention and in-depth research from academia and industry.

[0004] All-solid-state batteries currently face challenges such as immature systems and high manufacturing costs. Therefore, only by achieving high energy density can their watt-hour cost be reduced. Energy density is largely determined by the cathode material. Lithium-rich manganese-based cathode materials (xLi2MnO3·(1-x)LiMO2, M=Ni, Co, Mn, etc.) are considered ideal cathode materials for next-generation high-energy-density lithium-ion batteries due to their high specific capacity (>250 mAh / g) and high operating voltage. However, applying them to all-solid-state batteries (ASSBs) still faces significant challenges: (1) Interface problems: Traditional lithium-rich materials and solid electrolytes (SSEs) have a solid-solid contact, resulting in high interfacial impedance and low ion transport efficiency. (2) Low electronic / ionic conductivity: The intrinsic electronic and ionic conductivity of the materials are both low, leading to severe performance degradation under high current. (3) Interfacial side reactions: Adverse interfacial reactions easily occur between the materials and solid electrolytes during sintering and cycling, resulting in capacity decay.

[0005] Existing improvement methods, such as simple surface coatings (e.g., Al2O3, Li2TiO3), typically only form a coating layer on the surface of secondary spheres, making it difficult to penetrate to the primary particle interface within the material. For secondary spheres at the micrometer scale or even smaller, traditional liquid or solid-phase coating methods cannot achieve a uniform, dense, and thin solid electrolyte layer on the surface of primary particles, leading to blockage of internal ion transport channels and limited performance improvement in all-solid-state batteries. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a coated microcrystalline lithium-rich manganese-based cathode material, its preparation method and application, which has high capacity performance and excellent cycle stability in solid-state batteries.

[0007] This invention provides a coated microcrystalline lithium-rich manganese-based cathode material, wherein the cathode material is a secondary spherical particle formed by primary particle stacking, and both the primary particle and the secondary sphere have a coating material formed in situ by atomic layer deposition on their surfaces.

[0008] The coating material includes an oxide solid electrolyte.

[0009] Preferably, the primary particles are lithium-rich manganese-based cathode materials with a particle size of 20~500nm;

[0010] The particle size of the secondary spherical particles is 500 nm to 5 μm.

[0011] Preferably, the coating material has both electron-conducting and ion-conducting properties.

[0012] Preferably, the oxide solid electrolyte is selected from one or more of LiNbO3, LLZO, LLTO, LATP, Li3PO4 and LiTaO3.

[0013] Preferably, the thickness of the coating material is 2~20nm.

[0014] This invention provides a method for preparing the coated microcrystalline lithium-rich manganese-based cathode material described in the above technical solution, comprising the following steps:

[0015] S1: A mixed salt solution of manganese, nickel and cobalt salts, along with a precipitant and a complexing agent, is added dropwise to a system containing an organic dispersant and a pore-forming agent to co-precipitate and react, resulting in a nickel-cobalt-manganese precursor suspension with a particle size D50 of 1~5 μm.

[0016] S2: Wash, filter and dry the nickel-cobalt-manganese precursor suspension to obtain nickel-cobalt-manganese precursor particles.

[0017] S3: The nickel-cobalt-manganese precursor particles are pre-sintered to obtain a porous nickel-cobalt-manganese precursor.

[0018] S4: The porous nickel-cobalt-manganese precursor, lithium salt, and additives are mixed, ground, and sintered to obtain a microcrystalline lithium-rich manganese-based cathode material.

[0019] S5: The microcrystalline lithium-rich manganese-based cathode material is modified at the gas-solid interface to obtain a lithium-rich manganese-based cathode material with oxygen vacancies.

[0020] S6: The lithium-rich manganese-based cathode material with oxygen vacancies is subjected to in-situ atomic layer deposition and then tempered to obtain a coated microcrystalline lithium-rich manganese-based cathode material.

[0021] Preferably, the pore-forming agent is selected from one or more of graphene, carbon nanotubes, and conductive carbon black;

[0022] The organic dispersant is selected from one or more of PEG-400, sodium dodecyl sulfate (SDS), polyethylene glycol (PEG), sodium polystyrene sulfonate (PSS), N-methylpyrrolidone (NMP), and dimethylformamide (DMF).

[0023] Preferably, the specific surface area of ​​the porous nickel-cobalt-manganese precursor obtained in step S3 is 8~200 m². 2 / g.

[0024] Preferably, the pH of the reaction system is controlled to be 7.6~9.5 by controlling the dropping rate of the precipitant;

[0025] The pre-sintering temperature is 400~600℃, and the pre-sintering time is 4~10h;

[0026] The sintering temperature is 800~950℃, and the sintering time is 10~20h;

[0027] The tempering temperature is 300~700℃, and the tempering time is 2~5h.

[0028] This invention provides an application of the coated microcrystalline lithium-rich manganese-based cathode material described above in liquid batteries, semi-solid batteries, or all-solid batteries;

[0029] The negative electrode in the battery is made of graphite, artificial graphite, silicon-carbon material, lithium metal, or lithium-carbon material.

[0030] This invention provides a coated microcrystalline lithium-rich manganese-based cathode material. The cathode material consists of secondary spherical particles formed by primary particle stacking. Both the primary and secondary spherical particles have an in-situ coated material formed by atomic layer deposition. The coated material includes an oxide solid electrolyte. This cathode material has a unique "core-shell" structure, with the "core" being a microcrystalline lithium-rich material and the "shell" being a nanoscale solid electrolyte layer. This "shell" layer simultaneously coats both the primary particles and the secondary spheres. This structure effectively suppresses interfacial side reactions between the cathode material and the solid electrolyte, stabilizing the interfacial structure. It provides continuous and short Li⁺ and electron transport paths, significantly reducing the interfacial impedance in all-solid-state batteries and improving the rate performance and cycle stability of the material. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the process for preparing the coated microcrystalline lithium-rich manganese-based cathode material according to the present invention;

[0032] Figure 2 This is a SEM image of the coated microcrystalline lithium-rich manganese-based cathode material of Example 1 of the present invention;

[0033] Figure 3 This is a TEM image of the surface coating morphology of the coated microcrystalline lithium-rich manganese-based cathode material in Example 1 of the present invention.

[0034] Figure 4 This is a comparison of the first charge-discharge performance of the coated microcrystalline lithium-rich manganese-based cathode material in an all-solid-state battery according to Example 1 of the present invention.

[0035] Figure 5 This is a comparison of the cycle performance of the coated microcrystalline lithium-rich manganese-based cathode material in an all-solid-state battery according to Example 1 of the present invention. Detailed Implementation

[0036] This invention provides a coated microcrystalline lithium-rich manganese-based cathode material, wherein the cathode material is a secondary spherical particle formed by primary particle stacking, and both the primary and secondary spherical particles have a coating material formed in situ by atomic layer deposition on their surfaces.

[0037] The coating material includes an oxide solid electrolyte.

[0038] In this invention, the primary particles are typically 50-200 nm in size, while the secondary spherical particles are at the micrometer level.

[0039] The materials coating the surfaces of the primary and secondary spherical particles described in this invention possess both electron-conducting and ion-conducting properties. In this invention, the surface-coating material that performs both electron-conducting and ion-conducting functions is a material that facilitates lithium-ion conduction, belonging to the category of fast ion conductors. The included material comprises an oxide solid electrolyte; the solid electrolyte is selected from oxide solid electrolytes. The solid electrolyte is selected from one or more of lithium niobate (LiNbO3), lithium lanthanum zirconium oxide (LLZO), lithium lanthanum titanium oxide (LLTO), lithium aluminum titanium phosphate (LATP), lithium phosphate (Li3PO4), and lithium tantalate (LiTaO3).

[0040] The coating material of this invention may also contain conductive carbon. The conductive carbon is preferably added during the precursor synthesis process, and the conductive carbon is formed by a pre-oxidation process, while some of it volatilizes to create pores. The added material is preferably one or more of graphene, carbon nanotubes and conductive carbon black.

[0041] In this invention, the thickness of the material coating the surface of the primary particles and the secondary spherical particles is 2~20nm, specifically 2nm, 3nm, 4nm, 5nm, 6nm, 7nm, 8nm, 9nm, 10nm, 11nm, 12nm, 13nm, 14nm, 15nm, 16nm, 17nm, 18nm, 19nm or 20nm.

[0042] In this invention, the primary particles are lithium-rich manganese-based cathode materials with a particle size of 20~500nm; the secondary spherical particles have a particle size of 500nm~5μm.

[0043] The in-situ surface coating method in this invention is obtained by atomic layer deposition coating combined with surface solid-phase sintering.

[0044] The present invention also provides a method for preparing the coated microcrystalline lithium-rich manganese-based cathode material described in the above technical solution, comprising the following steps:

[0045] S1: A mixed salt solution of manganese, nickel and cobalt salts, along with a precipitant and a complexing agent, is added dropwise to a system containing an organic dispersant and a pore-forming agent to co-precipitate and react, resulting in a nickel-cobalt-manganese precursor suspension with a particle size D50 of 1~5 μm.

[0046] S2: Wash, filter and dry the nickel-cobalt-manganese precursor suspension to obtain nickel-cobalt-manganese precursor particles.

[0047] S3: The nickel-cobalt-manganese precursor particles are pre-sintered to obtain a porous nickel-cobalt-manganese precursor.

[0048] S4: The porous nickel-cobalt-manganese precursor, lithium salt, and additives are mixed, ground, and sintered to obtain a microcrystalline lithium-rich manganese-based cathode material.

[0049] S5: The microcrystalline lithium-rich manganese-based cathode material is modified at the gas-solid interface to obtain a lithium-rich manganese-based cathode material with oxygen vacancies.

[0050] S6: The lithium-rich manganese-based cathode material with oxygen vacancies is subjected to in-situ atomic layer deposition and then tempered to obtain a coated microcrystalline lithium-rich manganese-based cathode material.

[0051] This invention uses a co-precipitation synthesis of lithium-rich manganese-based cathode material precursors with secondary spherical small particles (the particle size of the secondary spherical particles is 500 nm~5 μm). Through controlled precursor synthesis, including the introduction of additives, pre-sintering to create pores, and lithium mixing and sintering modification, especially through surface atomic layer deposition coating combined with solid-state sintering, a solid electrolyte surface coating is formed on the surface of the primary particles inside the secondary spheres of the microcrystalline lithium-rich manganese-based cathode material.

[0052] This invention involves adding a mixed salt solution of manganese, nickel, and cobalt salts, along with a precipitant and a complexing agent, dropwise to a system containing an organic dispersant and a pore-forming agent for co-precipitation reaction, resulting in a nickel-cobalt-manganese precursor suspension with a particle size D50 of 1-5 μm. Alternatively, this invention involves mixing a nickel-containing compound, a cobalt-containing compound, and a manganese-containing compound with water to obtain a mixed salt solution of manganese, nickel, and cobalt salts. The precipitant used in this invention is selected from sodium carbonate solution, sodium hydroxide solution, or sodium acetate solution; the complexing agent is an ammonia solution; the organic dispersant is selected from one or more of PEG-400, sodium dodecyl sulfate (SDS), polyethylene glycol (PEG), sodium polystyrene sulfonate (PSS), N-methylpyrrolidone (NMP), and dimethylformamide (DMF); and the pore-forming agent is selected from one or more of graphene, carbon nanotubes, and conductive carbon black.

[0053] The mixed salt solution, precipitant, complexing agent, organic dispersant, and pore-forming agent suspensions are all pumped into the coprecipitation reactor using metering pumps. The dropping rate of the mixed salt solution is 0.5–100 mL / min; the dropping rate of the complexing agent is 0.1–40 mL / min; and the pH value of the reaction in the reactor is controlled to be 7.6–9.5 by controlling the dropping rate of the precipitant. The coprecipitation reaction is carried out at a temperature of 50–60 °C for 40–60 h; coprecipitation is conducted under stirring at a speed of 200–1000 rpm. This invention controls the D50 of the precursor formed by coprecipitation to be within the range of 1–5 micrometers.

[0054] After obtaining the nickel-cobalt-manganese precursor suspension, this invention washes, filters, and dries the nickel-cobalt-manganese precursor suspension to obtain nickel-cobalt-manganese precursor particles. The composition of the nickel-cobalt-manganese precursor varies depending on the type of precipitant; if the precipitant is sodium carbonate, the composition of the nickel-cobalt-manganese precursor is Mn. c0 Ni a0 Cob0 CO3; if the precipitant is sodium hydroxide, then the composition of the nickel-cobalt-manganese precursor is Mn c0 Ni a0 Co b0 (OH)2; if the precipitant is sodium acetate, then the composition of the nickel-cobalt-manganese precursor is Mn c0 Ni a0 Co b0 (COOH)2.

[0055] In other words, the nickel-cobalt-manganese precursor obtained by the present invention has a composition of formula 101, formula 102, or formula 103:

[0056] Ni a0 Co b0 Mn c0 CO3 type 101;

[0057] Ni a0 Co b0 Mn c0 (OH)2 formula 102;

[0058] Ni a0 Co b0 Mn c0 (COOH)2 formula 103;

[0059] Among them, 0 <a0≤0.5,0≤b0<0.5,0.5≤c0<1。

[0060] This invention involves pre-sintering the nickel-cobalt-manganese precursor particles to obtain a porous nickel-cobalt-manganese precursor. The porous nickel-cobalt-manganese precursor exhibits high porosity and a large specific surface area, ranging from 8 to 200 m². 2 / g, preferably 50~200 m 2 / g. The pre-sintering temperature is 400~600℃, which can be 400℃, 450℃, 500℃, 550℃ or 600℃; the time is 4~10h, which can be 4h, 5h, 6h, 7h, 8h, 9h or 10h.

[0061] After obtaining the porous nickel-cobalt-manganese precursor, this invention mixes the porous nickel-cobalt-manganese precursor with lithium salt and additives, then grinds and sintersects the mixture to obtain a microcrystalline lithium-rich manganese-based cathode material. The small-particle polycrystalline precursor in the porous nickel-cobalt-manganese precursor maintains its unique morphology during sintering, while some large particles can break down into smaller particles. This small-particle polycrystalline lithium-rich material is the microcrystalline material.

[0062] In this invention, the lithium source can be any lithium source well known in the art, preferably one or more of lithium carbonate, lithium hydroxide, lithium oxide, and lithium acetate; the mass ratio of the porous nickel-cobalt-manganese precursor to the lithium source is 1.05~1.30:1. The additive is selected from one or more of H3BO3, NH4F, nano-alumina, and nano-alumina-magnesium; the amount of the additive added is less than 2wt% of the coated microcrystalline lithium-rich manganese-based cathode material; the additive can improve the specific properties of the material, such as conductivity, rate performance, cycle life, or processing performance, and reduce the sintering temperature of the material.

[0063] The sintering temperature described in this invention is 800~950℃, specifically 800℃, 850℃, 900℃, or 950℃. The sintering time is 10~20h, specifically 10h, 11h, 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, or 20h. The sintering atmosphere is air or oxygen. The resulting microcrystalline lithium-rich manganese material has a Li composition. 1+d Ni a0 Co b0 Mn c0 Compounds of O2, where d > 1.

[0064] After obtaining the microcrystalline lithium-rich manganese-based cathode material, this invention performs gas-solid interface modification on the microcrystalline lithium-rich manganese-based cathode material to obtain a lithium-rich manganese-based cathode material with oxygen vacancies. Preferably, this invention places the microcrystalline lithium-rich manganese-based cathode material in a gas-solid interface reactor for gas-solid interface modification to purify the surface, eliminate residual lithium, and optimize the surface chemical state; oxygen vacancies are formed on the surface, improving the first-stage efficiency, resulting in a lithium-rich manganese-based cathode material that can effectively suppress lattice oxygen evolution and gas production; the atmosphere for gas-solid interface modification is an NH3 / Ar mixture, O2, O3, or a fluorine-containing atmosphere. The temperature for gas-solid interface modification is 100~350℃, specifically 100℃, 150℃, 200℃, 250℃, 300℃, or 350℃; the time is 2~8h, specifically 2h, 3h, 4h, 5h, 6h, 7h, or 8h.

[0065] After obtaining a lithium-rich manganese-based cathode material with oxygen vacancies, this invention performs in-situ atomic layer deposition (ALD) coating on the oxygen-vacancy-rich lithium-rich manganese-based cathode material, and then tempers the coated material to obtain a coated microcrystalline lithium-rich manganese-based cathode material. This invention uses atomic layer deposition (ALD) technology to in-situ coat gas-solid interface modified lithium-rich manganese-based cathode material, sequentially depositing each component element of the fast ion conductor or solid electrolyte. Through self-limiting surface reactions, a coating layer is formed in-situ on the surface of the primary particles and the entire outer surface and internal pore surfaces of the secondary spheres. The thickness of the coating layer is 2~20 nm, preferably 2~8 nm.

[0066] In specific embodiments of the present invention, lithium source, aluminum source, phosphorus source and oxygen source are used as precursors, and cyclic deposition is performed at 100~230°C; or lithium source, phosphorus source and oxygen source are used as precursors; or lithium source, zirconium source, phosphorus source and oxygen source are used as precursors; or lithium source, niobium source, phosphorus source and oxygen source are used as precursors.

[0067] In this invention, the tempering temperature is 300~700℃, specifically 300℃, 350℃, 400℃, 450℃, 500℃, 550℃, 600℃, 650℃, or 700℃; the tempering time is 2~5 hours, specifically 2 hours, 3 hours, 4 hours, or 5 hours. Tempering is used to crystallize the solid electrolyte layer deposited by ALD.

[0068] The solid-state battery microcrystalline lithium-rich manganese-based cathode material prepared by the above method provided by the present invention has a microcrystalline structure, and both the surface of the primary particles and the surface of the secondary spheres are covered by an ultrathin layer of solid electrolyte.

[0069] This invention creates a microcrystalline structure with a large specific surface area and abundant internal pores by controlling the precursor particle size D50 to 1~5μm and introducing pore-forming agents such as graphene. This provides the necessary conditions for the effective permeation and reaction of the subsequent ALD precursor gas on the inner surface, realizing "bulk phase coating" from the outside of the secondary sphere to the surface of the primary particle, rather than the traditional external coating only.

[0070] This invention utilizes ALD technology to simultaneously construct an ultrathin, uniform, and continuous solid electrolyte ion conductor layer on the surfaces of primary particles and secondary spheres, greatly shortening the transport path of Li⁺ from the bulk phase to the solid electrolyte and significantly reducing interfacial impedance. During the preparation process, the small amount of residual carbon may synergize with the ALD coating layer to form a continuous electron transport network, thus achieving dual interface engineering for both ion transport channels and electron transport channels.

[0071] The cathode material prepared by the method provided by this invention has a unique "core-shell" structure. The "core" is a microcrystalline lithium-rich material, and the "shell" is a nanoscale solid electrolyte layer, which simultaneously coats primary particles and secondary spheres. This structure effectively suppresses interfacial side reactions between the cathode material and the solid electrolyte, stabilizing the interfacial structure. Furthermore, this structure provides continuous and short Li⁺ and electron transport paths, significantly reducing the interfacial impedance in all-solid-state batteries and improving the rate performance and cycle stability of the material. The method provided by this invention offers strong process controllability, good coating uniformity, and is suitable for large-scale production.

[0072] This invention introduces a pore-forming agent, including a carbon-containing highly conductive substance, into the synthesis process of a carbonate precursor with high specific surface area and small particle size, based on traditional synthesis methods. Pre-oxidation of the precursor creates pores, increasing the specific surface area of ​​the material and yielding a microcrystalline lithium-rich manganese-based cathode material. Combining solid-state sintering with surface atomic layer deposition and other modification techniques, simultaneous coating is achieved on the material surface, the internal pores of secondary spheres, and the surface of primary particles, forming a continuous ion / electron dual-conductivity network. Chemical bonding between the coating layer and the substrate enhances interfacial stability. This high-capacity microcrystalline lithium-rich manganese-based cathode material is suitable for use in all-solid-state lithium-rich manganese-based batteries due to its high capacity, high safety, long cycle life, and high compaction properties.

[0073] The preparation method provided by this invention effectively shortens the ion-electron transport path by reducing the particle size of the secondary particles of lithium-rich materials. It also effectively solves the problem of interface issues between the cathode material and the solid electrolyte, which severely restricts battery performance due to the inability of the solid electrolyte to effectively penetrate the interior of the secondary spheres, leading to the disruption of the ion / electron conduction path. Conventional surface coatings only cover the outer surface of the secondary spheres and cannot solve the internal conduction problem. While directly using single-crystal and microcrystalline materials as nano-primary particles can effectively solve the interface problem to some extent, lithium-rich manganese-based cathode materials have poor kinetic performance, and single-crystal and microcrystalline materials suffer from capacity differences and excessively large specific surface areas, which also cause serious interfacial side reactions. Therefore, there is an urgent need to effectively modify high-capacity lithium-rich manganese-based cathode materials with secondary spherical particles to achieve high capacity while maintaining good interfacial performance, thus realizing high-energy-density, low-cost lithium-rich manganese-based solid-state batteries.

[0074] Figure 1This is a schematic diagram of the process for preparing microcrystalline lithium-rich manganese-based cathode material for solid-state batteries according to the present invention. A precursor suspension is prepared by co-precipitation of a mixed metal salt solution, precipitant, complexing agent, and additives. The precursor suspension is washed, centrifuged, and dried to obtain small-particle precursors. The small-particle precursors are pre-sintered to obtain small-particle oxide precursors. The small-particle oxide precursors are mixed with lithium and then sintered to obtain a high specific surface area microcrystalline lithium-rich manganese-based cathode material. After gas-solid interface modification, oxygen vacancies are present. ALD coating is then performed to obtain a coated lithium-rich manganese-based cathode material with oxygen vacancies. Tempering yields a coated microcrystalline lithium-rich manganese-based cathode material.

[0075] This invention provides an application of the coated microcrystalline lithium-rich manganese-based cathode material described above in liquid batteries, semi-solid batteries, or all-solid batteries;

[0076] The negative electrode in the battery is made of graphite, artificial graphite, silicon-carbon material, lithium metal, or lithium-carbon material.

[0077] Using the above-mentioned coated microcrystalline lithium-rich manganese-based cathode material as the cathode material for all-solid-state lithium-rich manganese-based batteries, the three-dimensional conduction network is effectively achieved: the coating layer penetrates both inside and outside the secondary sphere, increasing the ionic conductivity by 10 times (>10). -5 Simultaneously, it can form an outer coating layer to suppress interfacial side reactions; the inner solid electrolyte provides ion conduction channels to achieve dual interfacial protection. Combined with high-pressure treatment, the coating layer and oxygen vacancy matrix form Li-MO bonds, suppressing cycle cracking and structural stability. This results in a lithium-rich manganese-based cathode material with high capacity, high safety, long cycle life, and high-pressure compaction, suitable for preparing high-energy-density, long-life all-solid-state lithium-ion batteries.

[0078] In this invention, the solid-state positive electrode sheet includes the microcrystalline lithium-rich manganese-based positive electrode material for solid-state batteries described in the above-mentioned technical solution; it also includes a binder, a conductive agent, and a solvent, wherein the binder is PVDF, the conductive agent is conductive carbon, and the solvent is polyetheretherketone; the mass ratio of the positive electrode material, binder, conductive agent, and solvent is 75:15:5:5. The above components are ball-milled and then rolled with a porous aluminum mesh in an inert environment.

[0079] In this invention, the electrolyte film on the positive electrode side is made of Li3In 0.7 Sc 0.3 The Li3In was prepared by compression molding of Cl6, conductive carbon, and polyetheretherketone (PEEK) spheres. 0.7 Sc 0.3 The mass ratio of Cl6, conductive carbon, and polyetheretherketone is 98:1.5:0.5.

[0080] In this invention, the electrolyte film on the negative electrode side is made of Li 5.8 PS 4.8 Cl 1.2The Li was prepared by ball milling conductive carbon and polyetheretherketone and then pressing them into tablets. 5.8 PS 4.8 Cl 1.2 The mass ratio of conductive carbon to polyetheretherketone is 98:1.5:0.5.

[0081] Solid negative electrode sheets are made by coarsely grinding negative electrode material, indium and tin powder, heating it, pouring it onto microporous copper foil, scraping it flat, and rolling it into shape.

[0082] The present invention stacks a solid positive electrode sheet, a positive side electrolyte film, an anti-electrolyte film, and a solid negative electrode sheet in sequence and encapsulates them to form a solid-state battery.

[0083] To further illustrate the present invention, the following detailed description, in conjunction with embodiments, provides a coated microcrystalline lithium-rich manganese-based cathode material, its preparation method, and its applications. However, these descriptions should not be construed as limiting the scope of protection of the present invention.

[0084] Example 1

[0085] A method for preparing a coated microcrystalline lithium-rich manganese-based cathode material includes the following steps:

[0086] Precursor preparation:

[0087] 1) Prepare a 500L mixed salt solution of 2mol / L by mixing nickel sulfate, cobalt sulfate and manganese sulfate compounds in a molar ratio of 1:1:4.

[0088] 2) Prepare a 2 mol / L sodium carbonate solution as a precipitant and a 0.5 mol / L ammonia solution as a complexing agent;

[0089] 3) The mixed salt solution, precipitant, complexing agent, PEG-400 dispersant (0.5 g / L), and graphene suspension (1.0 g / L) are added to the coprecipitation reactor at a certain rate using a metering pump. The dropping rate of the mixed salt solution is 30 mL / min, and the dropping rate of the complexing agent is 7 mL / min. The pH value of the reaction in the reactor is controlled to be around 8.5 by controlling the dropping rate of the precipitant. At the same time, the reactor temperature is controlled at 55℃ and the stirring speed is controlled at 700 r / min. After coprecipitation for 45 h, a nickel cobalt manganese carbonate precursor suspension is obtained.

[0090] 4) The above nickel-cobalt-manganese carbonate precursor suspension was washed, filtered, and dried to obtain a sample with a D50≈3.2μm and a specific surface area of ​​120m². 2 / g of nickel cobalt manganese carbonate precursor particles;

[0091] Cathode material preparation:

[0092] 5) The nickel-cobalt-manganese carbonate precursor particles were pre-sintered in air at 500°C for 6 hours to obtain a porous nickel-cobalt-manganese carbonate precursor with a specific surface area of ​​85 m². 2 / g.

[0093] 6) The above porous nickel-cobalt-manganese carbonate precursor and lithium carbonate were mixed in a Li:(Ni+Co+Mn) ratio of 1.45, with 1 wt% H3BO3 additive added. The mixture was ball-milled for 4 hours and then sintered at 875℃ for 12 hours to obtain a microcrystalline lithium-rich manganese-based cathode material. Figure 2 The obtained microcrystalline lithium-rich manganese-based cathode material has a primary particle size of approximately 50 nm, a secondary sphere particle size (D50) of approximately 4 μm, and a specific surface area of ​​8 m². 2 / g is a porous material.

[0094] Gas-solid interface modification of cathode materials:

[0095] 7) The above-mentioned microcrystalline lithium-rich manganese-based cathode material was placed in a gas-solid interface reactor and treated at 300°C for 2 hours in an NH3 / Ar mixed gas. Oxygen vacancies were formed on the surface, and the initial efficiency of the material was improved, resulting in a lithium-rich manganese-based cathode material with oxygen vacancies that can effectively suppress the generation of oxygen evolution in the lattice.

[0096] Atomic layer deposition coating on the surface of cathode material:

[0097] 8) The above-mentioned lithium-rich manganese-based cathode material with oxygen vacancies is placed in an ALD device. Using lithium (lithium tert-butoxide), aluminum (TMA trimethylaluminum), phosphorus (trimethyl phosphate), and oxygen (water vapor) as precursors, cyclic deposition is performed at 200°C to deposit a 2 nm LATP solid electrolyte coating layer, thus obtaining a coated microcrystalline lithium-rich manganese-based cathode material, such as... Figure 3 As shown.

[0098] Tempering treatment of cathode materials:

[0099] 9) The above-mentioned coated microcrystalline lithium-rich manganese-based cathode material after ALD coating is heat-treated at 600°C for 3 hours in Ar atmosphere to obtain a microcrystalline lithium-rich manganese-based cathode material with carbon coating and solid electrolyte coating on the surface of the secondary spherical particles and the surface of the internal primary particles.

[0100] Solid-state positive electrode preparation:

[0101] 10) According to the coated microcrystalline lithium-rich manganese-based cathode material: Li3In 0.7 Sc 0.3 Cl6: conductive carbon: polyetheretherketone = 75:15:5:5 by mass was ball-milled and compounded. The ball milling speed was 500 r / min, the time was 6 h, and it was rolled with porous aluminum mesh in an inert environment.

[0102] Preparation of electrolyte film on the positive electrode side:

[0103] 11) The preparation method of the high-voltage electrolyte membrane on the positive electrode side is carried out under an inert atmosphere according to Li3In 0.7 Sc 0.3 Cl6: conductive carbon: polyetheretherketone = 98:1.5:0.5 parts by mass were ball-milled and then calendered to obtain a 50 μm film.

[0104] Preparation of electrolyte film on the negative electrode side:

[0105] 12) The solid electrolyte membrane on the negative electrode side is prepared as follows, under an inert atmosphere according to Li 5.8 PS 4.8 Cl 1.2 Conductive carbon and polyetheretherketone (PEEK) were mixed in a ratio of 98:1.5:0.5 by mass and ball-milled, then calendered to form a film. The resulting 50 μm negative electrode side electrolyte membrane was obtained.

[0106] Solid-state negative electrode preparation:

[0107] 13) Li 0.5 In 0.3 Sn 0.2 The metal composite anode is prepared as follows: graphene-composite silicon-carbon anode material and Li are mixed in a molar ratio of 95:5. 0.5 In 0.3 Sn 0.2 The powder was coarsely ground, then heated to 250°C and held at that temperature for 3 hours under an inert argon atmosphere, with stirring performed during the process. The heated powder was then poured onto a microporous copper foil, leveled, and finally rolled into shape.

[0108] Solid-state battery fabrication:

[0109] 14) A lithium-rich manganese-based cathode material solid cathode sheet, a high-voltage electrolyte membrane on the cathode side, a solid electrolyte membrane layer on the anode side, and a solid anode sheet are stacked sequentially and encapsulated under a pressure of 20 MPa.

[0110] Performance testing:

[0111] The electrochemical performance is as follows: Within a voltage window of 1.4–4.2 V, the material's initial discharge specific capacity at 0.1C rate increased from 210.98 mAh / g in Comparative Example 1 to 250 mAh / g, and the initial efficiency was also improved from 73.96% to 80.5%. Furthermore, the polarization voltage was reduced. The dV / dQ curves of the initial charge of the lithium-rich manganese-based solid-state battery show a reduction in oxidation potential, indicating a decrease in battery impedance. The highest capacity of the hollow lithium-rich material at 0.1C cycling can reach as high as 250 mAh / g. See [link to relevant documentation]. Figure 5After 100 cycles, the specific capacity increased from 144.45 mAh / g in Comparative Example 1 to 219.91 mAh / g. The capacity retention also improved significantly, from 68.2% to 89.3%. This demonstrates that by introducing pore-forming agents, including carbon-containing highly conductive substances, into the synthesis process of a high-specific-surface-area, small-particle carbonate precursor, and utilizing precursor pre-oxidation to create pores and simultaneously applying low-temperature carbon coating, a microcrystalline lithium-rich manganese-based cathode material can be obtained. Combining solid-state sintering with surface atomic layer deposition and other modification methods, simultaneous coating of the material surface, the internal pores of secondary spheres, and the surface of primary particles is achieved; a continuous ion / electron dual-conductivity network is formed; and chemical bonding is formed between the coating layer and the substrate to enhance interfacial stability. This high-capacity microcrystalline lithium-rich manganese-based cathode material for solid-state batteries, possessing high capacity, high safety, long cycle life, and high compaction, is suitable for preparing high-energy-density, long-life all-solid-state lithium-ion batteries.

[0112] Example 2

[0113] A method for preparing a coated microcrystalline lithium-rich manganese-based cathode material includes the following steps:

[0114] Precursor preparation:

[0115] 1) Prepare a 500L mixed salt solution of 2mol / L by mixing nickel sulfate, cobalt sulfate and manganese sulfate compounds in a molar ratio of 1:1:4.

[0116] 2) Prepare a 2 mol / L sodium carbonate solution as a precipitant and a 0.5 mol / L ammonia solution as a complexing agent;

[0117] 3) The mixed salt solution, precipitant, complexing agent, PEG-400 dispersant (0.5 g / L), and carbon nanotube suspension (1.0 g / L) were added to the coprecipitation reactor at a certain rate using a metering pump. The dropping rate of the mixed salt solution was 30 mL / min, and the dropping rate of the complexing agent was 7 mL / min. The pH value of the reaction in the reactor was controlled to be around 8.5 by controlling the dropping rate of the precipitant. At the same time, the reactor temperature was controlled at 55℃ and the stirring speed was controlled at 650 r / min. After coprecipitation for 45 h, a nickel cobalt manganese carbonate precursor suspension was obtained.

[0118] 4) The above nickel-cobalt-manganese carbonate precursor suspension was washed, filtered, and dried to obtain a sample with a D50≈3.2μm and a specific surface area of ​​120m². 2 / g of nickel cobalt manganese carbonate precursor particles;

[0119] Cathode material preparation:

[0120] 5) The nickel-cobalt-manganese carbonate precursor particles were pre-calcined in air at 500°C for 6 hours to obtain a porous nickel-cobalt-manganese carbonate precursor with a specific surface area of ​​120 m². 2 / g.

[0121] 6) The above porous nickel-cobalt-manganese carbonate precursor and lithium carbonate were mixed at a ratio of Li:(Ni+Co+Mn)=1.45, with 1wt% H3BO3 additive added. The mixture was ball-milled for 4 hours and then sintered at 875℃ for 12 hours to obtain a microcrystalline lithium-rich manganese-based cathode material. The obtained microcrystalline lithium-rich manganese-based cathode material has a primary particle size of about 100nm, a secondary spherical particle size D50 of about 7μm, and a specific surface area of ​​5m². 2 / g, is a porous material;

[0122] Gas-solid interface modification of cathode materials:

[0123] 7) The above-mentioned microcrystalline lithium-rich manganese-based cathode material was placed in a gas-solid interface reactor and treated at 300°C for 2 hours in an NH3 / Ar mixed gas. Oxygen vacancies were formed on the surface, and the first efficiency was improved. A lithium-rich manganese-based cathode material with oxygen vacancies was obtained, which can effectively suppress the generation of oxygen evolution in the lattice.

[0124] Atomic layer deposition coating on the surface of cathode material:

[0125] 8) The above-mentioned lithium-rich manganese-based cathode material with oxygen vacancies is placed in an ALD device, and a lithium source (lithium tert-butoxide), a phosphorus source (trimethyl phosphate), and an oxygen source (water vapor) are used as precursors. Cyclic deposition is performed at 200°C to deposit a 5 nm lithium phosphate solid electrolyte coating layer to obtain a coated microcrystalline lithium-rich manganese-based cathode material.

[0126] Tempering treatment of cathode materials:

[0127] 9) The above-mentioned coated microcrystalline lithium-rich manganese-based cathode material after ALD coating is heat-treated at 700°C for 2 hours in Ar atmosphere to obtain a microcrystalline lithium-rich manganese-based cathode material with carbon coating and solid electrolyte coating on the surface of the secondary spherical particles and the surface of the internal primary particles.

[0128] Solid-state positive electrode preparation:

[0129] 10) According to the coated microcrystalline lithium-rich manganese-based cathode material: Li3In 0.7 Sc 0.3 Cl6: conductive carbon: polyether ether ketone = 75:15:5:5 by mass was ball-milled and compounded; the ball milling speed was 500 r / min and the time was 6 h, and it was rolled with porous aluminum mesh in an inert environment;

[0130] Preparation of electrolyte film on the positive electrode side:

[0131] 11) The preparation method of the high-voltage electrolyte membrane on the positive electrode side is carried out under an inert atmosphere according to Li3In 0.7 Sc 0.3 Cl6: conductive carbon: polyether ether ketone = 98:1.5:0.5 parts by mass were ball-milled and then calendered to obtain a 50μm film;

[0132] Preparation of electrolyte film on the negative electrode side:

[0133] 12) The solid electrolyte membrane on the negative electrode side is prepared as follows, under an inert atmosphere according to Li 5.8 PS 4.8 Cl 1.2 Conductive carbon and polyether ether ketone (PEEK) were ball-milled in a ratio of 98:1.5:0.5 by mass, and then calendered to form a 50 μm negative electrode side electrolyte membrane.

[0134] Solid-state negative electrode preparation:

[0135] 13) Li 0.5 In 0.3 Sn 0.2 The metal composite anode is prepared as follows: graphene-composite silicon-carbon anode material and Li are mixed in a molar ratio of 95:5. 0.5 In 0.3 Sn 0.2 The powder was coarsely ground, then heated to 250°C and held at that temperature for 3 hours under an inert argon atmosphere, with stirring performed during the process. The heated powder was then poured onto a microporous copper foil, leveled, and finally rolled into shape.

[0136] Solid-state battery fabrication:

[0137] 14) A lithium-rich manganese-based cathode material solid cathode sheet, a high-voltage electrolyte membrane on the cathode side, a solid electrolyte membrane on the anode side, and a solid anode sheet are stacked sequentially and encapsulated under a pressure of 20 MPa.

[0138] Performance testing:

[0139] The electrochemical performance is as follows: within a voltage window of 1.4~4.2V, the initial discharge specific capacity of the above battery increased from 152.98 mAh / g in Comparative Example 1 to 242 mAh / g, and the initial efficiency also improved from 58% to 76.5%. Furthermore, the polarization voltage was reduced. The dV / dQ curve of the initial charge of the lithium-rich manganese-based solid-state battery shows a reduction in oxidation potential, indicating a decrease in battery impedance. The highest capacity of the hollow lithium-rich material at 0.1C cycling reached 250 mAh / g, which is the highest specific capacity achievable by solid-state batteries to date. After 100 cycles, the specific capacity also increased from 144.45 mAh / g in Comparative Example 1 to 210.91 mAh / g. The capacity retention also improved significantly, from 68.2% to 88.3%.

[0140] Example 3

[0141] A method for preparing a coated microcrystalline lithium-rich manganese-based cathode material includes the following steps:

[0142] Precursor preparation:

[0143] 1) Prepare a 500L mixed salt solution of 2mol / L by mixing nickel sulfate, cobalt sulfate and manganese sulfate compounds in a molar ratio of 1:1:4.

[0144] 2) Prepare a 2 mol / L sodium carbonate solution as a precipitant and a 0.5 mol / L ammonia solution as a complexing agent;

[0145] 3) The mixed salt solution, precipitant, complexing agent, PEG-400 dispersant (0.5 g / L), and graphene and carbon nanotube (1:1) composite suspension (1.0 g / L) were added to the coprecipitation reactor at a certain rate using a metering pump. The mixed salt solution was added at a rate of 30 mL / min, the complexing agent was added at a rate of 7 mL / min, and the pH value of the reaction in the reactor was controlled to be around 8.5 by controlling the drop rate of the precipitant. At the same time, the reactor temperature was controlled at 55℃ and the stirring speed was controlled at 700 r / min. After coprecipitation for 45 h, a nickel cobalt manganese carbonate precursor suspension was obtained.

[0146] 4) The above nickel-cobalt-manganese carbonate precursor suspension was washed, filtered, and dried to obtain a sample with a D50≈3.2μm and a specific surface area of ​​120m². 2 / g of nickel cobalt manganese carbonate precursor particles;

[0147] Cathode material preparation:

[0148] 5) The nickel-cobalt-manganese carbonate precursor particles were pre-calcined in air at 500°C for 6 hours to obtain a porous nickel-cobalt-manganese carbonate precursor with a specific surface area of ​​135 m². 2 / g.

[0149] 6) The above porous nickel-cobalt-manganese carbonate precursor and lithium carbonate were mixed at a Li:Me ratio of 1.45, with 1 wt% H3BO3 additive added. The mixture was ball-milled for 4 hours and then sintered at 875℃ for 12 hours to obtain a microcrystalline lithium-rich manganese-based cathode material. The resulting microcrystalline lithium-rich manganese-based cathode material had a primary particle size of approximately 150 nm, a secondary spherical particle size (D50) of approximately 6.5 μm, and a specific surface area of ​​5.3 m². 2 / g, is a porous material;

[0150] Gas-solid interface modification of cathode materials:

[0151] 7) The above-mentioned microcrystalline lithium-rich manganese-based cathode material was placed in a gas-solid interface reactor and treated at 300°C for 2 hours in an NH3 / Ar mixed gas. Oxygen vacancies were formed on the surface, and the first efficiency was improved. A lithium-rich manganese-based cathode material with oxygen vacancies was obtained, which can effectively suppress the generation of oxygen evolution in the lattice.

[0152] Atomic layer deposition coating on the surface of cathode material:

[0153] 8) The above-mentioned lithium-rich manganese-based cathode material with oxygen vacancies is placed in an ALD device, and a lithium source (lithium tert-butoxide), a zirconium source (tetramethylzirconium), and an oxygen source (water vapor) are used as precursors. Cyclic deposition is performed at 200°C to deposit a lithium zirconate solid electrolyte coating layer with a thickness of 2 nm, thereby obtaining a coated microcrystalline lithium-rich manganese-based cathode material.

[0154] Tempering treatment of cathode materials:

[0155] 9) The above-mentioned coated microcrystalline lithium-rich manganese-based cathode material after ALD coating is heat-treated at 700°C for 2 hours in Ar atmosphere to obtain a microcrystalline lithium-rich manganese-based cathode material with carbon coating and solid electrolyte coating on the surface of the secondary spherical particles and the surface of the internal primary particles.

[0156] Solid-state positive electrode preparation:

[0157] 10) According to the coated microcrystalline lithium-rich manganese-based cathode material: Li3In 0.7 Sc 0.3 Cl6: conductive carbon: polyetheretherketone = 75:15:5:5 by mass was ball-milled and compounded. The ball milling speed was 500 r / min, the time was 6 h, and it was rolled with porous aluminum mesh in an inert environment.

[0158] Preparation of electrolyte film on the positive electrode side:

[0159] 11) The preparation method of the high-voltage electrolyte membrane on the positive electrode side is carried out under an inert atmosphere according to Li3In 0.7 Sc 0.3 Cl6: conductive carbon: polyetheretherketone = 98:1.5:0.5 parts by mass were ball-milled and then calendered to obtain a 50 μm film.

[0160] Preparation of electrolyte film on the negative electrode side:

[0161] 12) The solid electrolyte membrane on the negative electrode side is prepared as follows, under an inert atmosphere according to Li 5.8 PS 4.8 Cl 1.2 Conductive carbon and polyetheretherketone (PEEK) in a ratio of 98:1.5:0.5 parts by mass were ball-milled and then calendered to form a film. The resulting electrolyte membrane on the negative electrode side was 50 μm thick.

[0162] Solid-state negative electrode preparation:

[0163] 13) Li 0.5 In 0.3 Sn 0.2 The metal composite anode is prepared as follows: graphene-composite silicon-carbon anode material and Li are mixed in a molar ratio of 95:5. 0.5 In 0.3 Sn 0.2 The powder was coarsely ground, then heated to 250°C and held at that temperature for 3 hours under an inert argon atmosphere, with stirring performed during the process. The heated powder was then poured onto a microporous copper foil, leveled, and finally rolled into shape.

[0164] Solid-state battery fabrication:

[0165] 14) A lithium-rich manganese-based cathode material solid cathode sheet, a high-voltage electrolyte membrane on the cathode side, a solid electrolyte membrane layer on the anode side, and a solid anode sheet are stacked sequentially and encapsulated under a pressure of 20 MPa.

[0166] Performance testing:

[0167] The electrochemical performance is as follows: within a voltage window of 1.4~4.2V, the initial discharge specific capacity of the above battery increased from 152.98 mAh / g in Comparative Example 1 to 245 mAh / g, and the initial efficiency also improved from 58% to 76.9%. Furthermore, the polarization voltage was reduced. The dV / dQ curve of the initial charge of the lithium-rich manganese-based solid-state battery shows a reduction in oxidation potential, indicating a decrease in battery impedance. The highest capacity of the hollow lithium-rich material at 0.1C cycling reached 250 mAh / g, which is the highest specific capacity achievable by solid-state batteries to date. After 100 cycles, the specific capacity also increased from 144.45 mAh / g in Comparative Example 1 to 220.85 mAh / g. The capacity retention also improved significantly, from 68.2% to 89.8%.

[0168] Example 4

[0169] A method for preparing a coated microcrystalline lithium-rich manganese-based cathode material includes the following steps:

[0170] Precursor preparation:

[0171] 1) Prepare a 500L mixed salt solution of 2mol / L by mixing nickel sulfate, cobalt sulfate and manganese sulfate compounds in a molar ratio of 1:1:4.

[0172] 2) Prepare a 2 mol / L sodium carbonate solution as a precipitant and a 0.5 mol / L ammonia solution as a complexing agent;

[0173] 3) The mixed salt solution, precipitant, complexing agent, PEG-400 dispersant (0.5 g / L), and carbon nanotube suspension (1.0 g / L) were added to the coprecipitation reactor at a certain rate using a metering pump. The dropping rate of the mixed salt solution was 30 mL / min, and the dropping rate of the complexing agent was 7 mL / min. The pH value of the reaction in the reactor was controlled to be around 8.5 by controlling the dropping rate of the precipitant. At the same time, the reactor temperature was controlled at 55℃ and the stirring speed was controlled at 700 r / min. After coprecipitation for 45 h, a nickel cobalt manganese carbonate precursor suspension was obtained.

[0174] 4) The above nickel-cobalt-manganese carbonate precursor suspension was washed, filtered, and dried to obtain a sample with a D50≈3.2μm and a specific surface area of ​​120m². 2 / g of nickel cobalt manganese carbonate precursor particles;

[0175] Cathode material preparation:

[0176] 5) The nickel-cobalt-manganese carbonate precursor particles were pre-calcined in air at 500°C for 6 hours to obtain a porous nickel-cobalt-manganese carbonate precursor with a specific surface area of ​​95 m². 2 / g.

[0177] 6) The above porous nickel-cobalt-manganese carbonate precursor and lithium carbonate were mixed at a Li:Me ratio of 1.45, with 1 wt% H3BO3 additive added. The mixture was ball-milled for 4 hours and then sintered at 875℃ for 12 hours to obtain a microcrystalline lithium-rich manganese-based cathode material. The obtained microcrystalline lithium-rich manganese-based cathode material has a primary particle size of about 50 nm, a secondary spherical particle size D50 of about 5.5 μm, and a specific surface area of ​​8 m². 2 / g, is a porous material;

[0178] Gas-solid interface modification of cathode materials:

[0179] 7) The above-mentioned microcrystalline lithium-rich manganese-based cathode material was placed in a gas-solid interface reactor and treated at 300°C for 2 hours in an NH3 / Ar mixed gas. Oxygen vacancies were formed on the surface, and the first efficiency was improved. A lithium-rich manganese-based cathode material with oxygen vacancies was obtained, which can effectively suppress the generation of oxygen evolution in the lattice.

[0180] Atomic layer deposition coating on the surface of cathode material:

[0181] 8) The above-mentioned lithium-rich manganese-based cathode material with oxygen vacancies is placed in an ALD device, and lithium source (lithium tert-butoxide), niobium source (niobium ethanol) and oxygen source (water vapor) are used as precursors. Cyclic deposition is performed at 200°C to deposit a 3nm lithium niobate solid electrolyte coating layer to obtain a coated microcrystalline lithium-rich manganese-based cathode material.

[0182] Tempering treatment of cathode materials:

[0183] 9) The above-mentioned coated microcrystalline lithium-rich manganese-based cathode material after ALD coating is heat-treated at 700°C for 2 hours in Ar atmosphere to obtain a microcrystalline lithium-rich manganese-based cathode material with carbon coating and solid electrolyte coating on the surface of the secondary spherical particles and the surface of the internal primary particles.

[0184] Solid-state positive electrode preparation:

[0185] 10) According to the coated microcrystalline lithium-rich manganese-based cathode material: Li3In 0.7 Sc 0.3 Cl6: conductive carbon: polyetheretherketone = 75:15:5:5 by mass was ball-milled and compounded. The ball milling speed was 500 r / min, the time was 6 h, and it was rolled with porous aluminum mesh in an inert environment.

[0186] Preparation of electrolyte film on the positive electrode side:

[0187] 11) The preparation method of the high-voltage electrolyte membrane on the positive electrode side is carried out under an inert atmosphere according to Li3In 0.7 Sc 0.3 Cl6: conductive carbon: polyetheretherketone = 98:1.5:0.5 parts by mass were ball-milled and then calendered to obtain a 50 μm film.

[0188] Preparation of electrolyte film on the negative electrode side:

[0189] 12) The solid electrolyte membrane on the negative electrode side is prepared as follows, under an inert atmosphere according to Li 5.8 PS 4.8 Cl 1.2 Conductive carbon and polyetheretherketone (PEEK) in a ratio of 98:1.5:0.5 parts by mass were ball-milled and then calendered to form a film. A 50 μm negative electrode side electrolyte membrane was obtained.

[0190] Solid-state negative electrode preparation:

[0191] 13) Li 0.5 In 0.3 Sn 0.2 The metal composite anode is prepared as follows: graphene-composite silicon-carbon anode material and Li are mixed in a molar ratio of 95:5. 0.5 In 0.3 Sn 0.2 The powder was coarsely ground, then heated to 250°C and held at that temperature for 3 hours under an inert argon atmosphere, with stirring performed during the process. The heated powder was then poured onto a microporous copper foil, leveled, and finally rolled into shape.

[0192] Solid-state battery fabrication:

[0193] 14) A lithium-rich manganese-based cathode material solid cathode sheet, a high-voltage electrolyte membrane on the cathode side, a solid electrolyte membrane layer on the anode side, and a metal composite anode are stacked sequentially and encapsulated under a pressure of 20 MPa.

[0194] Performance testing:

[0195] The electrochemical performance is as follows: within a voltage window of 1.4~4.2V, the initial discharge specific capacity of the above battery increased from 152.98 mAh / g in Comparative Example 1 to 245 mAh / g, and the initial efficiency also improved from 58% to 76.9%. Furthermore, the polarization voltage was reduced. The dV / dQ curve of the initial charge of the lithium-rich manganese-based solid-state battery shows a reduction in oxidation potential, indicating a decrease in battery impedance. The highest capacity of the hollow lithium-rich material at 0.1C cycling reached as high as 250 mAh / g. After 100 cycles, the specific capacity also increased from 144.45 mAh / g in Comparative Example 1 to 216.91 mAh / g. The capacity retention rate also improved significantly, from 68.2% to 89.2%.

[0196] Comparative Example 1

[0197] A method for preparing a coated microcrystalline lithium-rich manganese-based cathode material includes the following steps:

[0198] Precursor preparation:

[0199] 1) Prepare a 500L mixed salt solution of 2mol / L by mixing nickel sulfate, cobalt sulfate and manganese sulfate compounds in a molar ratio of 1:1:4.

[0200] 2) Prepare a 2 mol / L sodium carbonate solution as a precipitant and a 0.5 mol / L ammonia solution as a complexing agent;

[0201] 3) The mixed salt solution, precipitant, and complexing agent are added to the coprecipitation reactor at a certain rate using a metering pump. The dropping rate of the mixed salt solution is 30 mL / min, and the dropping rate of the complexing agent is 7 mL / min. The pH value of the reaction in the reactor is controlled to be around 8.5 by controlling the dropping rate of the precipitant. At the same time, the reactor temperature is controlled at 55℃ and the stirring speed is controlled at 700 r / min. After coprecipitation for 45 h, a nickel cobalt manganese carbonate precursor suspension is obtained.

[0202] 4) The above nickel-cobalt-manganese carbonate precursor suspension was washed, filtered, and dried to obtain a D50≈3.5μm and a specific surface area of ​​85m². 2 / g of nickel cobalt manganese carbonate precursor particles;

[0203] Cathode material preparation:

[0204] 5) The nickel cobalt manganese carbonate precursor particles were pre-calcined in air at 500°C for 6 hours to obtain a porous nickel cobalt manganese carbonate precursor.

[0205] 6) The above porous nickel-cobalt-manganese carbonate precursor and lithium carbonate were mixed in a ratio of Li:(Ni+Co+Mn)=1.45, and 1wt% H3BO3 additive was added. The mixture was ball-milled for 4 hours and sintered at a high temperature of 875℃ for 12 hours to obtain microcrystalline lithium-rich manganese-based cathode material.

[0206] Gas-solid interface modification of cathode materials:

[0207] 7) The above-mentioned microcrystalline lithium-rich manganese-based cathode material was placed in a gas-solid interface reactor and treated at 300°C for 2 hours in an NH3 / Ar mixed gas. Oxygen vacancies were formed on the surface, and the first efficiency was improved. A lithium-rich manganese-based cathode material with oxygen vacancies was obtained, which can effectively suppress the generation of oxygen evolution in the lattice.

[0208] Solid-state positive electrode preparation:

[0209] 8) According to the coated microcrystalline lithium-rich manganese-based cathode material: Li3In 0.7 Sc 0.3 Cl6: conductive carbon: polyetheretherketone = 75:15:5:5 by mass was ball-milled and compounded. The ball milling speed was 500 r / min, the time was 6 h, and it was rolled with porous aluminum mesh in an inert environment.

[0210] Preparation of electrolyte film on the positive electrode side:

[0211] 9) The preparation method of the high-voltage electrolyte membrane on the positive electrode side is carried out under an inert atmosphere according to Li3In 0.7 Sc 0.3 Cl6: conductive carbon: polyetheretherketone = 98:1.5:0.5 parts by mass were ball-milled and then calendered to obtain a 50 μm film.

[0212] Preparation of electrolyte film on the negative electrode side:

[0213] 10) The solid electrolyte membrane on the negative electrode side is prepared as follows, under an inert atmosphere according to Li 5.8 PS 4.8 Cl 1.2 Conductive carbon and polyether ether ketone (PEEK) were ball-milled in a ratio of 98:1.5:0.5 by mass, and then calendered to form a 50 μm negative electrode side electrolyte membrane.

[0214] Solid-state negative electrode preparation:

[0215] 11) Li 0.5 In 0.3 Sn 0.2The metal composite anode is prepared as follows: graphene-composite silicon-carbon anode material and Li are mixed in a molar ratio of 95:5. 0.5 In 0.3 Sn 0.2 The powder was coarsely ground, then heated to 250°C and held at that temperature for 3 hours under an inert argon atmosphere, with stirring performed during the process. The heated powder was then poured onto a microporous copper foil, leveled, and finally rolled into shape.

[0216] Solid-state battery fabrication:

[0217] 12) The lithium-rich manganese-based cathode material solid cathode sheet, the high-voltage electrolyte membrane on the cathode side, the solid electrolyte membrane layer on the anode side and the metal composite anode are stacked in sequence and encapsulated under a pressure of 20MPa.

[0218] Performance testing:

[0219] The electrochemical performance is as follows: Within a voltage window of 1.4–4.2 V, the initial discharge specific capacity of the battery is 210.98 mAh / g, with an initial efficiency of 73.96%. The dV / dQ curve of the lithium-rich manganese-based solid-state battery during the first charge shows a high oxidation potential and relatively high battery impedance. After 100 cycles at 0.1C, the specific capacity is 144.45 mAh / g, indicating a capacity retention of 68.2%.

[0220] Therefore, based on the synthesis of carbonate precursors with high specific surface area and small particles, the introduction of pore-forming agents, including carbon-containing highly conductive substances, during the synthesis process, and the use of precursor pre-oxidation to create pores and improve the material's specific surface area, along with low-temperature carbon coating, yields microcrystalline lithium-rich manganese-based cathode materials. Combined with solid-state sintering and modification methods such as surface atomic layer deposition coating, simultaneous coating of the material surface, the internal pores of secondary spheres, and the surface of primary particles is achieved; only then can a continuous ion / electron dual-conductivity network be formed. The chemical bonding between the coating layer and the substrate enhances interfacial stability. This high-capacity microcrystalline lithium-rich manganese-based cathode material for solid-state batteries serves as the cathode material for all-solid-state lithium-rich manganese-based batteries. Its high capacity, high safety, long cycle life, and high-compactness characteristics make it suitable for preparing high-energy-density, long-life all-solid-state lithium-ion batteries.

[0221] As can be seen from the above embodiments, the present invention provides a microcrystalline lithium-rich manganese-based cathode material for solid-state batteries. The cathode material is prepared from a lithium-rich manganese-based precursor, and both primary particles and secondary spheres are coated on the surface. This cathode material has a unique "core-shell" structure, where the "core" is a microcrystalline lithium-rich material and the "shell" is a nanoscale solid electrolyte layer, which simultaneously coats both primary particles and secondary spheres. This structure effectively suppresses interfacial side reactions between the cathode material and the solid electrolyte, stabilizing the interfacial structure. It provides continuous and short Li⁺ and e⁻ transport paths, significantly reducing the interfacial impedance in all-solid-state batteries and improving the rate performance and cycle stability of the material. Experimental results show that, compared with Example 1, the material in Comparative Example 1 without surface atomic layer deposition coating exhibits poor cycle performance in all-solid-state batteries and obviously cannot meet the relevant requirements.

[0222] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A coated microcrystalline lithium-rich manganese-based cathode material, characterized in that, The cathode material is a secondary spherical particle formed by primary particle stacking, and both the primary and secondary spherical particles have a coating material formed in situ by atomic layer deposition on their surfaces. The coating material includes an oxide solid electrolyte.

2. The coated microcrystalline lithium-rich manganese-based cathode material according to claim 1, characterized in that, Lithium-rich manganese-based cathode material with primary particle size of 20~500nm; The particle size of the secondary spherical particles is 500 nm to 5 μm.

3. The coated microcrystalline lithium-rich manganese-based cathode material according to claim 1, characterized in that, The coating material has both electron and ion conduction properties.

4. The coated microcrystalline lithium-rich manganese-based cathode material according to claim 3, characterized in that, The oxide solid electrolyte is selected from one or more of LiNbO3, LLZO, LLTO, LATP, Li3PO4, and LiTaO3.

5. The coated microcrystalline lithium-rich manganese-based cathode material according to claim 1, characterized in that, The thickness of the coating material is 2~20nm.

6. A method for preparing the coated microcrystalline lithium-rich manganese-based cathode material according to any one of claims 1 to 5, comprising the following steps: S1: A mixed salt solution of manganese, nickel and cobalt salts, along with a precipitant and a complexing agent, is added dropwise to a system containing an organic dispersant and a pore-forming agent to co-precipitate and react, resulting in a nickel-cobalt-manganese precursor suspension with a particle size D50 of 1~5 μm. S2: Wash, filter and dry the nickel-cobalt-manganese precursor suspension to obtain nickel-cobalt-manganese precursor particles. S3: The nickel-cobalt-manganese precursor particles are pre-sintered to obtain a porous nickel-cobalt-manganese precursor. S4: The porous nickel-cobalt-manganese precursor, lithium salt, and additives are mixed, ground, and sintered to obtain a microcrystalline lithium-rich manganese-based cathode material. S5: The microcrystalline lithium-rich manganese-based cathode material is modified at the gas-solid interface to obtain a lithium-rich manganese-based cathode material with oxygen vacancies. S6: The lithium-rich manganese-based cathode material with oxygen vacancies is subjected to in-situ atomic layer deposition and then tempered to obtain a coated microcrystalline lithium-rich manganese-based cathode material.

7. The preparation method according to claim 6, characterized in that, The pore-forming agent is selected from one or more of graphene, carbon nanotubes, and conductive carbon black. The organic dispersant is selected from one or more of PEG-400, sodium dodecyl sulfate (SDS), polyethylene glycol (PEG), sodium polystyrene sulfonate (PSS), N-methylpyrrolidone (NMP), and dimethylformamide (DMF).

8. The preparation method according to claim 6, characterized in that, The specific surface area of ​​the porous nickel-cobalt-manganese precursor obtained in step S3 is 8~200m². 2 / g.

9. The preparation method according to claim 6, characterized in that, The pH of the reaction system is controlled to be between 7.6 and 9.5 by controlling the dropping rate of the precipitant; The pre-sintering temperature is 400~600℃, and the pre-sintering time is 4~10h; The sintering temperature is 800~950℃, and the sintering time is 10~20h; The tempering temperature is 300~700℃, and the tempering time is 2~5h.

10. The application of the coated microcrystalline lithium-rich manganese-based cathode material according to any one of claims 1 to 5 in liquid batteries, semi-solid batteries or all-solid batteries; The negative electrode in the battery is made of graphite, artificial graphite, silicon-carbon material, lithium metal, or lithium-carbon material.

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