A high-stability lithium-rich manganese-based positive electrode material, a preparation method and application thereof

Abstract

The application belongs to the field of battery materials, and discloses a high-stability lithium-rich manganese-based positive electrode material and a preparation method and application thereof. The high-stability lithium-rich manganese-based positive electrode material comprises a core, a first coating layer and a second coating layer. The first coating layer is coated on at least part of the surface of the core. The second coating layer is coated on at least part of the surface of the particle formed by the core and the first coating layer. The core is a lithium-rich manganese-based positive electrode material. The first coating layer is Ce 0.9‑ y Y y Zr 0.1 O2, 0.01≤y≤0.1. The second coating layer is LiAlPO 4‑z F z , 0.05≤z≤0.1. The application improves the initial coulombic efficiency, suppresses the collapse of the body phase structure and voltage attenuation, and can inhibit transition metal dissolution and phase transition, so that the performance of the lithium-rich manganese-based material is synergistically improved.

Description

Technical Field

[0001] The present invention belongs to the field of battery materials, relates to a positive electrode material, and particularly relates to a composite positive electrode material, a preparation method thereof, and an application thereof. Background Art

[0002] The lithium-rich manganese-based positive electrode material is regarded as one of the ideal positive electrode materials for the next-generation high-energy-density lithium-ion batteries due to its high specific capacity (>250 mAh / g) and high working voltage. However, its commercial application is severely restricted by two key problems: (1) During the first charging process, irreversible lattice oxygen evolution occurs during the activation of the Li2MnO3 component, resulting in a low first Coulombic efficiency and capacity loss; (2) During long-term cycling, continuous oxygen loss, phase transformation, and the erosion of the electrolyte on the material surface together lead to severe capacity decay and voltage drop.

[0003] Surface coating is an effective means to improve the performance of lithium-rich manganese-based materials. In the prior art, a single coating layer is mostly used, such as metal oxides (Al2O3, ZrO2) or fluorides (AlF3). However, the function of a single coating layer is limited: Although the oxide coating layer can physically isolate, it has little effect on suppressing the internal oxygen release; the fluoride coating layer has good chemical stability, but may hinder the lithium-ion transport. More importantly, a single coating layer is difficult to solve the "from the inside out" oxygen loss problem and the "from the outside in" interface erosion problem simultaneously.

[0004] Therefore, developing a multi-layer coating structure that can act synergistically from different mechanisms and different levels is the key to breaking through the performance bottleneck of lithium-rich manganese-based materials. Summary of the Invention

[0005] Aiming at the defects and deficiencies existing in the prior art, on the first aspect, the present invention provides a highly stable lithium-rich manganese-based positive electrode material; on the second aspect, the present invention provides a preparation method of a highly stable lithium-rich manganese-based positive electrode material; on the third aspect, the present invention provides a battery.

[0006] On the first aspect, the present invention provides a highly stable lithium-rich manganese-based positive electrode material, which includes a core, a first coating layer, and a second coating layer. The first coating layer covers at least part of the surface of the core, and the second coating layer covers at least part of the surface of the particles formed by the core and the first coating layer;

[0007] The core is xLi2MnO3·(1 - x)LiMO2, where 0.3 < x < Y y Zr 0.1 O2, 0.01 ≤ y ≤ 0.1;​​​​​

[0009] The second coating layer is LiAlPO 4-z F z , 0.05≤z≤0.1.

[0010] Preferably, the mass of the first coating layer is 0.1 wt% to 1 wt% of the core.

[0011] More preferably, the mass of the first coating layer is 0.3wt%-0.9wt% of the core.

[0012] Preferably, the mass of the second coating layer is 0.2wt%-2wt% of the sum of the mass of the core and the mass of the first coating layer.

[0013] More preferably, the mass of the second coating layer is 0.5wt%-1.5wt% of the sum of the masses of the core and the first coating layer.

[0014] Preferably, the high-stability lithium-rich manganese-based cathode material has a spherical or near-spherical particle morphology.

[0015] Preferably, the particle size of the high-stability lithium-rich manganese-based cathode material is 4-8 μm.

[0016] Secondly, the present invention provides a method for preparing a highly stable lithium-rich manganese-based cathode material, comprising the following steps:

[0017] Step 1: Mix lithium-rich manganese-based material, Y source, Ce source and Zr source in solvent to obtain mixture A; add ammonia water to mixture A to adjust the pH value and heat to obtain mixture B; separate mixture B into solid and liquid components, dry the obtained solid and heat treat it in an oxygen-containing atmosphere to obtain intermediate product.

[0018] Step 2: Mix the intermediate product, Li source, Al source, P source and F source in a solvent to obtain mixture C. Heat mixture C until the solvent is completely evaporated. Place the obtained solid particles in an inert atmosphere or a vacuum atmosphere for heat treatment to obtain the high-stability lithium-rich manganese-based cathode material.

[0019] Preferably, in step 1, the Y source is any one or two of Y(NO3)3·6H2O and YCl3·6H2O; the Ce source is any one or more of Ce(NO3)3·6H2O, CeCl3·7H2O, and (NH4)2[Ce(NO3)6]; and the Zr source is any one or two of ZrO(NO3)2·xH2O and ZrOCl2·8H2O.

[0020] Preferably, in step 1, the molar ratio of Y in the Y source, the molar ratio of Zr in the Ce source, and the molar ratio of Zr in the Zr source are consistent with the stoichiometry of the first coating layer.

[0021] Preferably, in step 1, ammonia is added to adjust the pH of the reaction system to 9.5-10.5.

[0022] Preferably, in step 1, the heating temperature is 135-210℃ and the heating time is 7-16h.

[0023] Preferably, in step 1, the heat treatment temperature is 400-800℃ and the heat treatment time is 3-20h.

[0024] Preferably, in step 2, the Li source is any one or two of Li2CO3 and CH3COOLi·2H2O; the Al source is Al(NO3)3·9H2O; the P source is any one or two of NH4H2PO4 and (NH4)2HPO4; and the F source is any one or two of NH4F and LiF.

[0025] Preferably, in step 2, the stoichiometry of Li in the Li source, Al in the Al source, P in the P source, and the second coating layer is consistent.

[0026] Preferably, in step 2, the heating temperature is 110-165℃.

[0027] Preferably, in step 2, the heat treatment temperature is 450-650℃ and the heat treatment time is 4-10h.

[0028] Preferably, the gas providing the inert atmosphere is any one or more of nitrogen, argon, and helium.

[0029] Thirdly, the present invention provides a battery comprising the above-described high-stability lithium-rich manganese-based cathode material or the high-stability lithium-rich manganese-based cathode material prepared by the above-described preparation method.

[0030] Compared with the prior art, one or more technical solutions provided by the present invention have at least one of the following beneficial effects:

[0031] (1) This invention achieves synergistic improvement of the performance of lithium-rich manganese-based materials through a double-layer composite coating. The double-layer coating structure has excellent bulk stability, interfacial compatibility and ion transport performance. The first coating layer Ce 0.9-y Y y Zr 0.1 O2 serves as the oxygen storage layer, relying on Ce. 4+ / Ce 3+ Redox pairs and Y 3+Oxygen vacancies formed by doping enable reversible storage and release of reactive oxygen species, inhibiting bulk structure collapse and voltage decay; the outer layer of F-doped LiAlPO4 (F-LAP) is a fluorophosphorus composite armor layer, which has excellent HF corrosion resistance, efficient Li + conduction paths and strong interfacial anchoring effects, which can suppress the dissolution and phase transformation of transition metals. The synergistic effect of the double-layer coating not only maintains the integrity of the bulk structure but also optimizes the interfacial compatibility, significantly improving the cycle stability and rate performance of the material. Moreover, the preparation process is simple and the coating is uniform, making it easy for large-scale production.

[0032] (2) After 300 cycles at a rate of 1C, the capacity retention rate of the double-layer composite-coated cathode material provided by the present invention can be increased from 85% of the single coating to more than 92%. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 SEM image of the high-stability lithium-rich manganese-based cathode material prepared in Example 1;

[0034] Figure 2 Li 1.2 Ni 0.1 Co 0.1 Mn 0.6 XRD pattern of O2;

[0035] Figure 3 Ce 0.8 Y 0.1 Zr 0.1 XRD pattern of O2;

[0036] Figure 4 LiAlPO 3.9 F 0.1 XRD pattern. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] The present invention provides the following specific technical solutions.

[0038] First, the present invention provides a high-stability lithium-rich manganese-based cathode material, including a core, a first coating layer, and a second coating layer. The first coating layer covers at least part of the surface of the core, and the second coating layer covers at least part of the surface of the particles formed by the core and the first coating layer;

[0039] The core is xLi2MnO3·(1-x)LiMO2, where 0.3 < x < 0.6, and M is any one or more of Ni, Co, and Mn;

[0040] The first coating layer is Ce 0.9-y Y y Zr 0.1O2, 0.01≤y≤0.1;

[0041] The second coating layer is LiAlPO 4-z F z , 0.05≤z≤0.1.

[0042] Employing a hierarchical structure design of "core-double-layer coating," it combines excellent bulk stability, interfacial compatibility, and ion transport performance, resulting in significant overall performance advantages and strong logical synergy. The inner YCZO coating layer, with its Ce-based structure... 4+ / Ce 3+ Redox pairs and Y 3+ The oxygen vacancies formed by doping enable reversible adsorption and release of reactive oxygen species. Through the oxygen sponge effect, oxygen is locked within the solid phase, inhibiting bulk structural collapse and voltage decay, thus achieving fundamental bulk protection. The outer F-LAP layer, as a fluorophosphorus composite armor layer, achieves near-immunity to HF corrosion through strong Al-F and PF bonds, while retaining NASICON-type ionic conductivity pathways and enhancing ionic conductivity. Simultaneously, it anchors transition metals through strong PO-TM and MF bonds, inhibiting their dissolution and phase transformation, achieving interfacial solidification. The synergistic effect of the dual-layer coating maintains the integrity of the bulk structure and optimizes interfacial compatibility, significantly improving the material's cycle stability and rate performance.

[0043] The synergistic effect of the double coating, combined with the simple and controllable stepwise liquid phase deposition-thermal treatment preparation process, enables the material to exhibit excellent performance. After 300 cycles at 1C rate, the capacity retention rate is increased to over 92%, the average discharge voltage decay rate is significantly reduced, and the amount of transition metal dissolution is reduced to an extremely low level, thus comprehensively breaking through the performance bottleneck of single coating materials.

[0044] Preferably, the mass of the first coating layer is 0.1 wt% to 1 wt% of the core.

[0045] This coating amount ensures that the YCZO layer fully functions as an oxygen sponge, through Ce 4+ / Ce 3+ Redox pairs and oxygen vacancies enable reversible storage and release of reactive oxygen species, effectively suppressing bulk oxygen loss and structural collapse, while avoiding problems such as increased ion transport impedance and material specific capacity dilution caused by excessive coating. Simultaneously, the low-percentage coating design significantly reduces the cost of using rare metals Ce and Y, and combined with a simplified preparation process, it balances improved electrochemical performance with the economic viability of large-scale production.

[0046] Further preferably, the mass of the first coating layer is 0.3%-0.9% of the core.

[0047] Preferably, the mass of the second coating layer is 0.2wt%-2wt% of the sum of the mass of the core and the mass of the first coating layer.

[0048] The coating amount allows the F-LAP layer to form a dense and continuous fluorophosphorus composite armor, resisting HF corrosion through strong Al-F and PF bonds, and anchoring transition metal ions through PO-TM and MF bonds, while preserving the NASICON-type ion conduction pathway. It also avoids insufficient protection due to too low a coating amount, and problems such as increased ion impedance and dilution of specific capacity caused by excessive coating. Furthermore, this ratio can form synergistic protection with the inner YCZO layer without significantly increasing production costs, making it suitable for large-scale mass production.

[0049] More preferably, the mass of the second coating layer is 0.5wt%-1.5wt% of the sum of the masses of the core and the first coating layer.

[0050] Preferably, the high-stability lithium-rich manganese-based cathode material has a spherical or near-spherical particle morphology.

[0051] Blocky primary particles can improve the packing density between particles, reduce grain boundary defects, and suppress grain breakage and structural phase transformation during charging and discharging. Spherical secondary particles not only have excellent flowability and compaction density, which facilitates electrode slurry coating and cell assembly, but also reduce the contact interface impedance between the electrolyte and the particles, promoting uniform lithium ion insertion and extraction.

[0052] Preferably, the particle size of the high-stability lithium-rich manganese-based cathode material is 4-8 μm.

[0053] The high-stability lithium-rich manganese-based cathode material provided by this invention avoids the problems of aggravated electrolyte side reactions and increased transition metal dissolution caused by the excessively large specific surface area of ​​small-diameter particles (<4μm), while also avoiding the drawbacks of rate performance degradation and increased polarization caused by the excessively long lithium-ion diffusion path of large-diameter particles (>8μm), thus ensuring high efficiency in ion and electron transport. From a process perspective, 4-8μm spherical particles have excellent tap density and slurry dispersibility, which can improve electrode compaction density and electrode uniformity, making them suitable for large-scale coating and cell assembly processes. At the same time, this particle size can synergize with the double-layer coating structure to further enhance bulk stability and interfacial compatibility, contributing to a comprehensive improvement in material cycle life and voltage retention.

[0054] Secondly, the present invention provides a method for preparing a highly stable lithium-rich manganese-based cathode material, comprising the following steps:

[0055] Step 1: Mix lithium-rich manganese-based material, Y source, Ce source and Zr source in solvent to obtain mixture A; add ammonia water to mixture A to adjust the pH value and heat to obtain mixture B; separate mixture B into solid and liquid components, dry the obtained solid and heat treat it in an oxygen-containing atmosphere to obtain intermediate product.

[0056] Step 2: Mix the intermediate product, Li source, Al source, P source and F source in a solvent to obtain mixture C. Heat mixture C until the solvent is completely evaporated. Place the obtained solid particles in an inert atmosphere or a vacuum atmosphere for heat treatment to obtain the high-stability lithium-rich manganese-based cathode material.

[0057] Step 1 involves constructing the inner YCZO coating layer in an oxygen-containing atmosphere, which ensures the full oxidation of Ce, Y, and Zr precursors and the formation of a uniform oxygen vacancy structure, thus ensuring the effective activation of the oxygen sponge function. Step 2 involves switching to an inert or vacuum atmosphere to prepare the outer F-LAP coating layer, which avoids oxidation loss of the F source at high temperatures and ensures the stable formation of the NASICON-type crystal structure of LiAlPO4 and the F doping sites, achieving precise layering and functional synergy of the double coating.

[0058] In actual production, the mass ratio of lithium-rich manganese-based materials (Y source + Ce source + Zr source) and the mass ratio of intermediate products (Li source + Al source + P source) are determined according to actual needs, by the mass of the first coating layer and the mass of the second coating layer. The amount of raw materials used is calculated based on the required mass of the coating layer, and then the batching and production are carried out.

[0059] In step 2, the mixture C is heated by hydrothermal heating until the solvent is completely evaporated.

[0060] Preferably, in step 1, the Y source is Y(NO3)3·6H2O; the Ce source is Ce(NO3)3·6H2O; and the Zr source is any one or two of ZrO(NO3)2·xH2O and ZrOCl2·8H2O.

[0061] Preferably, in step 1, the molar ratio of Y in the Y source, the molar ratio of Zr in the Ce source, and the molar ratio of Zr in the Zr source are consistent with the stoichiometry of the first coating layer.

[0062] Preferably, in step 1, the heat treatment temperature is 400-800℃ and the heat treatment time is 3-20h.

[0063] Y-source, Ce-source, and Zr-source precursors can undergo sufficient decomposition and solid-state reaction to form Ce with moderate crystallinity and pure phase. 0.9-y Y y Zr 0.1 O2 coating layer, while promoting Y 3+ Uniform doping induces sufficient oxygen vacancies for Ce 4+ / Ce 3+The oxygen sponge effect of the redox pair provides the structural basis, ensuring the maximization of the reversible adsorption and release of reactive oxygen species. Furthermore, this temperature allows the YCZO coating layer to form a stable and well-bonded interface with the lithium-rich manganese-based core, ensuring both the integrity and uniformity of the coating layer and maintaining the bulk structural stability of the core material. Simultaneously, this temperature range is compatible with conventional industrial heat treatment equipment, enabling stable process control and continuous production, balancing functional activity with industrial applicability.

[0064] Preferably, in step 1, ammonia is added to adjust the pH of the reaction system to 9.5-11.

[0065] Adding ammonia to adjust the pH to 9.5-11 can make Y in mixture A... 3+ Ce 3+ Zr 4+ Plasma hydrolysis generates corresponding hydroxide or hydroxyl oxide precipitates, which uniformly coat the surface of lithium-rich manganese-based material particles. At the same time, it stabilizes the pH of the reaction system, avoiding uneven coating thickness caused by local pH fluctuations, thus laying the foundation for the formation of a dense and uniform modified layer in subsequent heat treatment.

[0066] Preferably, in step 1, the heating temperature is 135-210℃ and the heating time is 7-16h.

[0067] Under the above preferred conditions, it can be Y 3+ Ce 3+ Zr 4+ The hydrolysis and precipitation reactions provide sufficient motive force to accelerate the reaction process; at the same time, they promote the full collision and fusion of particles to form a uniform and dense coating layer; they can also accelerate the volatilization of small molecules in the system, reduce residual impurities in the solid, and ensure the structural integrity and modification effect of the intermediate product after subsequent heat treatment.

[0068] Preferably, in step 2, the Li source is any one or both of Li2CO3 and CH3COOLi·2H2O; the Al source is Al(NO3)3·9H2O; the P source is NH4H2PO4; and the F source is any one or both of NH4F and LiF.

[0069] Preferably, in step 2, the molar ratios of Li in the Li source, Al in the Al source, and P in the P source are consistent with the stoichiometric ratio of the second coating layer.

[0070] Preferably, in step 2, the heating temperature is 110-165℃.

[0071] Heating within this temperature range provides suitable activation energy for the interfacial reactions of Li, Al, P, and F ions with intermediate products, promoting uniform diffusion and doping of ions. It also avoids excessively high temperatures that could lead to abnormal grain growth and increased structural defects. Simultaneously, the gradual evaporation of the solvent promotes the formation of a stable and dense microstructure in the solid particles, thereby improving the cycle stability of the final cathode material.

[0072] Preferably, in step 2, the heat treatment temperature is 450-650℃ and the heat treatment time is 4-10h.

[0073] The Li, Al, P, and F source precursors can undergo a sufficient and controllable solid-state reaction to form an F-doped LiAlPO4 phase with suitable crystallinity, while ensuring that F... - It can uniformly replace O in the crystal lattice 2- This process stably constructs a strongly bonded Al-F and PF structure, providing the coating layer with excellent resistance to HF corrosion. Furthermore, this temperature fully preserves the inherent NASICON-type ion conductivity pathway of LiAlPO4, and the lithium vacancies introduced by F doping further enhance ion conductivity, achieving a balance between interface protection and ion transport performance. Simultaneously, this temperature allows the F-LAP layer to form a tightly bonded interface with the inner YCZO layer and the core particles, strengthening the synergistic protective effect of the double-layer coating. It is also compatible with conventional industrial heat treatment equipment, ensuring process stability and mass production suitability.

[0074] Preferably, the gas providing the inert atmosphere is any one or more of nitrogen, argon, and helium.

[0075] In practical applications, when preparing mixture A and mixture C in steps 1 and 2, it is only necessary to ensure that the materials are evenly dispersed. The amount of solvent used can be adjusted according to the actual situation.

[0076] Thirdly, the present invention provides a battery comprising the above-described high-stability lithium-rich manganese-based cathode material or the high-stability lithium-rich manganese-based cathode material prepared by the above-described preparation method.

[0077] To make the technical problems, technical solutions and technical advantages of the present invention clearer, a detailed description will be given below with reference to specific examples. However, the scope of protection of the present invention is not limited to the following specific embodiments.

[0078] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0079] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0080] Example 1:

[0081] A method for preparing a highly stable lithium-rich manganese-based cathode material includes the following steps:

[0082] Step 1, according to the stoichiometric ratio Ce 0.8 Y 0.1 Zr 0.1 O2 calculation: 1.72 g of Ce(NO3)3·6H2O, 0.13 g of ZrO(NO3)2·xH2O, and 0.18 g of Y(NO3)3·6H2O were weighed and dissolved in 50 mL of water to obtain a salt solution; 126.8 g of lithium-rich manganese-based material Li... 1.2 Ni 0.1 Co 0.1 Mn 0.6 O2 was dispersed in 300 mL of water to obtain a suspension. A salt solution was added dropwise to the material suspension at a rate of 2 mL / min. Then, the pH of the slurry was adjusted to 9.7 by adding ammonia. The mixture was stirred at 140 °C for 7 h to obtain mixture A. Mixture A was filtered to obtain a solid. The solid was filtered and dried to obtain solid particles. The solid particles were then heat-treated in air at 650 °C for 5 h and naturally cooled to obtain an intermediate product. The coating amount of the first coating layer was 0.6 wt% of the lithium-rich manganese-based material.

[0083] Step 2: Disperse 5g of the intermediate product in 100mL of deionized water to obtain a suspension. According to the stoichiometric ratio of LiAlPO4... 3.9 F 0.1 Calculations were performed, and 0.0398 g of CH3COOLi·2H2O, 0.1452 g of Al(NO3)3·9H2O, 0.0445 g of NH4H2PO4, and 0.0015 g of NH4F were weighed and dissolved in 50 mL of water to obtain a salt solution. The salt solution was added dropwise to the material suspension at a rate of 2 mL / min to obtain mixture B. Mixture B was stirred at 120 °C until it evaporated to dryness to obtain a powder. The obtained powder was heat-treated at 550 °C for 6 h in an argon atmosphere and then naturally cooled to obtain the high-stability lithium-rich manganese-based cathode material. The total amount of the second coating layer was 1.0 wt% of the intermediate product.

[0084] Comparative Example 1:

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

[0086] Step 1, according to the stoichiometric ratio Ce 0.8 Y 0.1 Zr 0.1O2 calculation: 1.72 g of Ce(NO3)3·6H2O, 0.13 g of ZrO(NO3)2·xH2O, and 0.18 g of Y(NO3)3·6H2O were weighed and dissolved in 50 mL of water to obtain a salt solution; 47.56 g of lithium-rich manganese-based material Li... 1.2 Ni 0.1 Co 0.1 Mn 0.6 O2 was dispersed in 300 mL of water to obtain a suspension. A salt solution was added dropwise to the material suspension at a rate of 2 mL / min. Then, the pH of the slurry was adjusted to 9.7 by adding ammonia. The mixture was stirred at 140 °C for 7 h to obtain mixture A. Mixture A was filtered to obtain a solid. The solid was filtered and dried to obtain solid particles. The solid particles were then heat-treated in air at 650 °C for 5 h and naturally cooled to obtain the lithium-rich manganese-based cathode material.

[0087] Comparative Example 2:

[0088] A method for preparing a highly stable lithium-rich manganese-based cathode material includes the following steps:

[0089] Step 2, take 3.125g of lithium-rich manganese-based material Li 1.2 Ni 0.1 Co 0.1 Mn 0.6 O2 was dispersed in 100 mL of deionized water to obtain a suspension. LiAlPO4 was then dissolved in water according to the stoichiometric ratio. 3.9 F 0.1 Calculations were performed, and 0.0398 g of CH3COOLi·2H2O, 0.1452 g of Al(NO3)3·9H2O, 0.0445 g of NH4H2PO4, and 0.0015 g of NH4F were weighed and dissolved in 50 mL of water to obtain a salt solution. The salt solution was added dropwise to the material suspension at a rate of 2 mL / min to obtain mixture B. Mixture B was stirred at 120 °C until it evaporated to dryness to obtain a powder. The obtained powder was heat-treated at 550 °C for 6 h in an argon atmosphere and then naturally cooled to obtain the high-stability lithium-rich manganese-based cathode material.

[0090] Comparative Example 3:

[0091] A method for preparing a lithium-rich manganese-based cathode material includes the following steps:

[0092] Step 1, according to the stoichiometric ratio Ce 0.8 Y 0.1 Zr 0.1O2 calculation: 1.72 g of Ce(NO3)3·6H2O, 0.13 g of ZrO(NO3)2·xH2O, and 0.18 g of Y(NO3)3·6H2O were weighed and dissolved in 50 mL of water to obtain a salt solution; 126.8 g of lithium-rich manganese-based material Li... 1.2 Ni 0.1 Co 0.1 Mn 0.6 O2 was dispersed in 300 mL of water to obtain a suspension. Salt solution was added dropwise to the material suspension at a rate of 2 mL / min. Then, the pH of the slurry was adjusted to 9.7 by adding ammonia. The mixture was stirred at 140 °C for 7 h to obtain mixture A. Mixture A was filtered to obtain a solid. The solid was filtered and dried to obtain solid particles. The solid particles were then heat-treated in air at 650 °C for 5 h and naturally cooled to obtain an intermediate product.

[0093] Step 2: Disperse 5g of the intermediate product in 100mL of deionized water to obtain a suspension. Based on the stoichiometric ratio of LiAlPO4, weigh 0.04g of CH3COOLi·2H2O, 0.1456g of Al(NO3)3·9H2O, and 0.045g of NH4H2PO4, and dissolve them in 50mL of water to obtain a salt solution. Add the salt solution dropwise to the material suspension at 2mL / min to obtain mixture B. Stir mixture B at 120℃ until it evaporates to dryness to obtain a powder. Place the obtained powder in an argon atmosphere at 550℃ for 6h and then allow it to cool naturally to obtain the highly stable lithium-rich manganese-based cathode material.

[0094] Comparative Example 4:

[0095] A lithium-rich manganese-based cathode material, namely, uncoated lithium-rich manganese-based material Li 1.2 Ni 0.1 Co 0.1 Mn 0.6 O2.

[0096] Example 2:

[0097] A method for preparing a highly stable lithium-rich manganese-based cathode material includes the following steps:

[0098] Step 1, press Ce 0.89 Y 0.01 Zr 0.1 O2 stoichiometry calculation: Weigh 0.463g of Ce(NO3)3·6H2O, 0.0386g of ZrOCl2·8H2O, and 0.00459g of Y(NO3)3·6H2O, dissolve them in 50mL of water to obtain a salt solution; Add 100g of lithium-rich manganese-based material Li 1.2 Ni 0.1 Co 0.1 Mn0.6 O2 was dispersed in 300 mL of water to obtain a suspension. A salt solution was added dropwise to the material suspension at a rate of 2 mL / min. Then, the pH of the slurry was adjusted to 10.7 by adding ammonia. The mixture was stirred at 165 °C for 10 h to obtain mixture A. Mixture A was filtered to obtain a solid. The solid was filtered and dried to obtain solid particles. The solid particles were then heat-treated at 700 °C for 20 h in an air atmosphere and allowed to cool naturally to obtain an intermediate product. The coating amount of the first coating layer was 0.2 wt% of the matrix.

[0099] Step 2: Disperse 50g of the intermediate product in 100mL of deionized water to obtain a suspension. (According to LiAlPO4) 3.95 F 0.05 Stoichiometric calculations were performed, and 0.00272 g of Li₂CO₃, 0.291 g of Al(NO₃)₃·9H₂O, 0.0891 g of NH₄H₂PO₄, and 0.001 g of LiF were weighed and dissolved in 10 mL of water to obtain a salt solution. The salt solution was added dropwise to the material suspension at a rate of 2 mL / min to obtain mixture B. Mixture B was stirred at 130 °C until it evaporated to dryness to obtain a powder. The obtained powder was heat-treated at 450 °C for 10 h in an argon atmosphere and then naturally cooled to obtain the high-stability lithium-rich manganese-based cathode material, with the total amount of the second coating layer being 0.2 wt% of the matrix.

[0100] Example 3:

[0101] A method for preparing a highly stable lithium-rich manganese-based cathode material includes the following steps:

[0102] Step 1, according to the stoichiometric ratio Ce 0.85 Y 0.05 Zr 0.1 O2 calculation: Weigh 2.241 g of Ce(NO3)3·6H2O, 0.1957 g of ZrOCl2·8H2O, and 0.1165 g of Y(NO3)3·6H2O, dissolve them in 50 mL of water to obtain a salt solution; Add 100 g of lithium-rich manganese-based material Li 1.2 Ni 0.1 Co 0.1 Mn 0.6 O2 was dispersed in 300 mL of water to obtain a suspension; salt solution was added to the material suspension and stirred evenly, and then the pH of the slurry was adjusted to 10.2 by adding ammonia dropwise. The mixture was stirred at 200 °C for 12 h to obtain mixture A. Mixture A was filtered to obtain a solid. The solid was filtered and dried to obtain solid particles. The solid particles were then heat-treated in air at 400 °C for 20 h and naturally cooled to obtain an intermediate product. The coating amount of the first coating layer was 1 wt% of the lithium-rich manganese-based material.

[0103] Step 2: Disperse 50g of the intermediate product in 50mL of deionized water to obtain a suspension. Proceed according to the stoichiometric ratio using LiAlPO4. 3.97 F 0.03 Calculations were performed, and 0.279 g of Li₂CO₃, 2.908 g of Al(NO₃)₃·9H₂O, 0.892 g of NH₄H₂PO₄, and 0.006 g of LiF were weighed and dissolved in 20 mL of water to obtain a salt solution. The salt solution was added to the material suspension and stirred until homogeneous to obtain mixture B. Mixture B was stirred at 152 °C until evaporated to dryness to obtain a powder. The obtained powder was heat-treated at 450 °C for 10 h in an argon atmosphere and then naturally cooled to obtain the high-stability lithium-rich manganese-based cathode material. The total amount of the second coating layer was 2 wt% of the intermediate product.

[0104] Figure 1 This is a SEM image of the highly stable lithium-rich manganese-based cathode material prepared in Example 1. Figure 1 It can be seen that the primary particles of the cathode material prepared by the preparation method provided by the present invention are blocky or blocky, and the secondary particles are spherical or spherical, with a particle size of 4-8 μm.

[0105] Figure 2 Li used in step 1 of Example 1 1.2 Ni 0.1 Co 0.1 Mn 0.6 The XRD pattern of O2, by Figure 2 It can be seen that the diffraction peaks conform to the typical structural characteristics of lithium-rich manganese-based cathode materials, and there are no obvious impurity phase diffraction peaks, indicating that Li 1.2 Ni 0.1 Co 0.1 Mn 0.6 O2 has a regular layered crystal structure and is of single phase and high purity.

[0106] Weigh 1.72g of Ce(NO3)3·6H2O, 0.13g of ZrO(NO3)2·xH2O, and 0.18g of Y(NO3)3·6H2O, dissolve them in 50mL of water to obtain a salt solution. Add ammonia to adjust the pH of the salt solution obtained in step 1 of Example 1 to 9.7. Then stir at 140℃ for 7h, filter to obtain a solid, dry the solid, heat treat it at 650℃ in air for 5h, cool it naturally and grind it to obtain Sample 1.

[0107] Figure 3 The XRD pattern for sample one. Figure 3PDF#28-0271 is a standard XRD card for CeO2, showing characteristic peaks of a fluorite-type structure. Sample 1's XRD peaks exhibit two key characteristics: firstly, a slight shift compared to the characteristic peaks of pure CeO2; and secondly, considering the preparation process of Sample 1, it should be Y... 3+ Zr 4+ With Ce 4+ Different ionic radii, replacing Ce in the CeO2 lattice 4+ This leads to lattice distortion, causing changes in interplanar spacing; secondly, the diffraction peaks of sample one only show a single fluorite-type structure peak, without impurity phase peaks of individual Y and Zr oxides. This indicates that Y and Zr do not exist as impurity phases, but rather enter the CeO2 lattice to form a solid solution, thus proving that Y and Zr were successfully doped.

[0108] Weigh 0.0398g of CH3COOLi·2H2O, 0.1452g of Al(NO3)3·9H2O, 0.0445g of NH4H2PO4 and 0.0015g of NH4F, dissolve them in 50mL of water to obtain a salt solution. Stir the salt solution at 120℃ until it evaporates to dryness to obtain a powder. Place the obtained powder in an argon atmosphere and heat-treat it at 550℃ for 6h. After natural cooling, grind it to obtain sample two.

[0109] Figure 4 This is the XRD pattern of sample two. Figure 4 PDF#80-1104 is the standard XRD card for LiAlPO4, while the XRD peaks of sample two exhibit two key characteristics: firstly, there is a slight shift relative to the standard peaks of LiAlPO4; secondly, considering the preparation process of sample two, it should be F... - With O 2- Different ionic radii, F - Replacing O in the LiAlPO4 lattice 2- The first is that it causes lattice distortion, which changes the interplanar spacing; the second is that it only shows a single phase peak of LiAlPO4 type, without the impurity phase peak of elemental F or fluoride. This indicates that F does not exist as an impurity phase, but enters the LiAlPO4 lattice to form a solid solution, thus proving that F has been successfully doped into LiAlPO4.

[0110] comprehensive Figure 1-4 , Figure 1 The uniform particle morphology in Example 1 indirectly proves that Ce was successfully processed. 0.8 Y 0.1 Zr 0.1 O2 and LiAlPO 3.97 F 0.03 Li 1.2 Ni 0.1 Co 0.1 Mn 0.6 O2 surface.

[0111] Preparation of positive electrode:

[0112] Electrode preparation was carried out in a temperature- and humidity-controlled dry room. First, the positive electrode active material, acetylene black, and polyvinylidene fluoride (PVDF) were weighed in a mass ratio of 8:1:1 and ground and mixed in an agate mortar. After uniform mixing, an appropriate amount of organic solvent N-methylpyrrolidone (NMP) was added dropwise, and the slurry was ground until it reached a fluid state. The slurry was evenly coated onto aluminum foil and dried in a vacuum oven at 120°C for 4 hours, and then a circular positive electrode sheet with a diameter of 14 mm was formed.

[0113] Button battery assembly:

[0114] The positive electrode was dried in a vacuum drying oven at 60°C for 2 hours. After being removed, it was placed in an argon-protected glove box and assembled with the negative electrode (a lithium sheet with a diameter of 15 mm and a thickness of 0.3 mm), the separator (Celgard 2400 microporous polypropylene membrane), and the electrolyte (LiPF6 as the solute; EC / DEC / EMC volume ratio = 1:1:1; electrolyte concentration of 1 mol / L) to form a CR2032 coin cell. The battery was subjected to constant current charge-discharge at 2.5-4.6V, and the Mn content in the electrolyte was detected by ICP test after 300 cycles. The test data are shown in Table 1.

[0115] Table 1. Test data of batteries assembled from the cathode materials prepared in Examples 1-3 and Comparative Examples 1-4.

[0116]

[0117] As shown in Table 1, the battery assembled from the cathode material provided by the present invention has good cycle performance, and the amount of Mn dissolved is greatly reduced.

[0118] The retention rate of Example 1 after 300 cycles at 1C was higher than that of Comparative Example 1, and the manganese content of the electrolyte was much lower than that of Comparative Example 1. This indicates that although the inner YCZO layer can improve the bulk stability through the oxygen sponge effect, it lacks the fluorine-phosphorus armor protection of the outer F-LAP layer and cannot effectively resist the corrosion of HF and the dissolution of transition metals in the electrolyte. In contrast, the double-layer coating of Example 1 further enhances the cycle stability and interface compatibility through the synergy of "bulk phase treatment + interface solid protection".

[0119] The cycle retention rate of Example 1 is significantly better than that of Comparative Example 2, indicating that although the outer F-LAP layer can protect the interface, it lacks the oxygen sponge effect of the inner YCZO layer to lock in bulk oxygen, making it difficult to suppress bulk structure collapse and voltage decay. In contrast, the inner YCZO layer and the outer F-LAP layer in Example 1 work together to solve the root cause of bulk oxygen loss and strengthen interface protection, thus achieving a comprehensive performance improvement.

[0120] Example 1 showed a higher cycle retention rate than Comparative Example 3 and a lower manganese content in the electrolyte than Comparative Example 3. This is because the F-doped F-LAP can form strong Al-F and PF bonds to resist HF corrosion, and at the same time anchor the transition metal through MF bonds. In contrast, the undoped LiAlPO4 has insufficient protective ability, which proves that F doping is the key to achieving efficient interface protection in the outer coating layer, and also reflects the design advantages of the F-LAP provided by this invention.

[0121] The cycle retention rate of Example 1 is nearly 1.7 times that of Comparative Example 4, and the manganese content of the electrolyte is only 1 / 36 of that of Comparative Example 4. This fully demonstrates that the "core-double layer coating" structure provides all-round protection from the bulk phase to the interface, completely solving the problems of bulk phase structure collapse and large-scale dissolution of transition metals in uncoated lithium-rich manganese-based materials, and significantly improving the cycle stability and service life of the material.

[0122] The above-described embodiments are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the technical scope of the present invention, based on the technical solution and concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A highly stable lithium-rich manganese-based cathode material, characterized in that, The positive electrode material has a double-layer coating structure. The positive electrode material includes a core, a first coating layer, and a second coating layer. The core, the first coating layer, and the second coating layer are arranged in sequence from the inside to the outside. The first coating layer covers at least part of the surface of the core, and the second coating layer covers at least part of the surface of the particles formed by the core and the first coating layer; The core is xLi2MnO3·(1-x)LiMO2, where 0.3 < x < 0.6, and M is any one or more of Ni, Co, and Mn; The first coating layer is Ce 0.9-y Y y Zr 0.1 O2, 0.01≤y≤0.1; The second coating layer is LiAlPO 4-z F z , 0.05≤z≤0.

1.

2. The high-stability lithium-rich manganese-based cathode material as described in claim 1, characterized in that, The mass of the first coating layer is 0.1wt%-1wt% of the core; the mass of the second coating layer is 0.2wt%-2wt% of the sum of the masses of the core and the first coating layer.

3. The high-stability lithium-rich manganese-based cathode material as described in claim 1, characterized in that, The particle morphology of the high-stability lithium-rich manganese-based positive electrode material is spherical or quasi-spherical; the particle size of the high-stability lithium-rich manganese-based positive electrode material is 4-8μm.

4. A method for preparing the high-stability lithium-rich manganese-based cathode material according to any one of claims 1 to 3, characterized in that, It includes the following steps: Step 1, mix the lithium-rich manganese-based material, Y source, Ce source, and Zr source in a solvent to obtain a mixed material A; add ammonia water to the mixed material A to adjust the pH value and heat it to obtain a mixed material B; separate the solid and liquid of the mixed material B, dry the obtained solid matter, and perform heat treatment in an oxygen-containing atmosphere to obtain an intermediate product; Step 2, mix the intermediate product, Li source, Al source, P source, and F source in a solvent to obtain a mixed material C, heat the mixed material C until the solvent completely volatilizes, and place the obtained solid particles under an inert atmosphere or a vacuum atmosphere for heat treatment to obtain the high-stability lithium-rich manganese-based positive electrode material.

5. The method for preparing the high-stability lithium-rich manganese-based cathode material as described in claim 4, characterized in that, In Step 1, the Y source is any one or two of Y(NO3)3·6H2O and YCl3·6H2O; the Ce source is any one or more of Ce(NO3)3·6H2O, CeCl3·7H2O, and (NH4)2[Ce(NO3)6]; the Zr source is any one or two of ZrO(NO3)2·xH2O and ZrOCl2·8H2O; In Step 1, the molar ratio of Y in the Y source, Ce in the Ce source, and Zr in the Zr source is consistent with the stoichiometry of the first coating layer.

6. The method for preparing the high-stability lithium-rich manganese-based cathode material as described in claim 4 or 5, characterized in that, In Step 1, add ammonia water to adjust the pH value of the reaction system to 9.5-10.5; the heating temperature is 135-210°C, and the heating time is 7-16h; the heat treatment temperature is 400-800°C, and the heat treatment time is 3-20h.

7. The method for preparing the high-stability lithium-rich manganese-based cathode material as described in claim 4, characterized in that, In Step 2, the Li source is any one or two of Li2CO3 and CH3COOLi·2H2O; the Al source is Al(NO3)3·9H2O; the P source is any one or two of NH4H2PO4 and (NH4)2HPO4; the F source is any one or two of NH4F and LiF; the molar ratio of Li in the Li source, Al in the Al source, and P in the P source is consistent with the stoichiometry of the second coating layer.

8. The method for preparing the high-stability lithium-rich manganese-based cathode material as described in claim 4 or 7, characterized in that, In Step 2, the heating temperature is 110-165°C; in Step 2, the heat treatment temperature is 450-650°C, and the heat treatment time is 4-10h.

9. The method for preparing the high-stability lithium-rich manganese-based cathode material as described in claim 4, characterized in that, The gas providing the inert atmosphere is any one or more of nitrogen, argon, and helium.

10. A battery, characterized in that, Including the high-stability lithium-rich manganese-based cathode material as described in any one of claims 1 to 3.

Images