Modified lithium-rich manganese-based positive electrode material, preparation method thereof and application of modified lithium-rich manganese-based positive electrode material in solid-state lithium battery

Abstract

The invention discloses a modified lithium-rich manganese-based positive electrode material, a preparation method thereof and application of the modified lithium-rich manganese-based positive electrode material in a solid-state lithium battery, and belongs to the field of lithium ion battery materials. The modified lithium-rich manganese-based positive electrode material comprises a lithium-rich manganese-based positive electrode material and a coating layer LiAl thereof, the molecular formula of the lithium-rich manganese-based positive electrode material is xLi2MnO3. (1-x) LiMO2, M is one or more of transition metals Ni, Co and Mn, and x is more than 0 and less than 1; and the coating layer LiAl is formed by decomposing LiAlH4. The preparation method comprises the following steps: uniformly mixing a lithium-rich manganese-based positive electrode material xLi2MnO3. (1-x) LiMO2 and LiAlH4 through a solid phase method or a liquid phase method, and then annealing in an inert atmosphere to prepare the modified lithium-rich manganese-based positive electrode material. The problems of unstable interface and poor transmission kinetics in the sulfide-based all-solid-state lithium ion battery are solved at the same time, and the first-circle charge-discharge specific capacity and cycle stability of the solid-state lithium ion battery can be improved.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery materials, specifically relating to a modified lithium-rich manganese-based cathode material, its preparation method, and its application in solid-state lithium batteries. Background Technology

[0002] All-solid-state lithium-ion batteries, employing inorganic solid-state electrolytes, have garnered significant attention in recent years due to their superior safety, wide operating temperature range, and high energy density potential. Recently, sulfide solid-state electrolytes have been considered one of the most promising systems for all-solid-state lithium-ion batteries, exhibiting room-temperature ionic conductivity comparable to liquid electrolytes and possessing ideal ductility. Meanwhile, lithium-rich manganese-based cathode materials can provide additional capacity by triggering redox reactions, overcoming the capacity bottleneck caused by transition metal ion redox reactions. Therefore, applying lithium-rich manganese-based cathode materials to all-solid-state lithium-ion batteries to improve battery energy density has significant research value and application prospects.

[0003] However, the practical application of lithium-rich manganese-based cathode materials in sulfide-based all-solid-state lithium-ion batteries still faces the following limitations and challenges: First, due to the electrochemical potential difference between the lithium-rich manganese-based cathode material and the sulfide solid electrolyte, a charge layer effect forms at the interface; second, under high voltage, the cathode-electrolyte interface inevitably degrades due to oxygen-related interface degradation / reactions. These problems lead to decreased interface stability and poorer energy efficiency and rate performance.

[0004] In recent years, researchers have addressed the challenges of lithium-rich manganese-based cathode materials in sulfide-based all-solid-state lithium-ion batteries by modifying their surfaces. For example, Chinese patent CN114865100A discloses a structurally stable, high-performance all-solid-state lithium-ion battery and its preparation method. This method improves cycle stability by adjusting the content of Co and LiNiO2 components in lithium-rich manganese and forming a stable LiNiO2 spinel structure on the surface of the lithium-rich manganese. However, this method is complex and does not address the charge layer effect. Chinese patent CN103633329A discloses an all-solid-state lithium-ion battery composite cathode material, its preparation method, and an all-solid-state lithium-ion battery. This method solves the charge layer effect problem by preparing a coating layer on the surface of the cathode material using radio frequency magnetron sputtering. However, this method is too costly and not conducive to commercial application. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention aims to provide a modified lithium-rich manganese-based cathode material and its preparation method. The method utilizes LiAl generated from the decomposition of LiAlH4 to coat the lithium-rich manganese-based cathode material. LiAl, as a pre-lithiation additive, can provide additional capacity, replenish the active lithium consumed in the initial cycle, reduce the rapid loss of lithium ions from the cathode surface, alleviate the interfacial lithium concentration gradient, and weaken the space charge layer effect of sulfide solid electrolytes. Simultaneously, H2 generated from the decomposition of LiAlH4 reacts with unstable lattice oxygen on the surface of the lithium-rich manganese-based cathode material to generate oxygen vacancies. These oxygen vacancies provide additional lithium ion migration channels, reduce the diffusion barrier, and improve interfacial ion transport kinetics. Therefore, when the modified lithium-rich manganese-based cathode material is used in solid-state lithium batteries, it can improve the first-cycle charge-discharge specific capacity and cycle stability of the solid-state lithium-ion battery.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] In a first aspect, the present invention provides a modified lithium-rich manganese-based cathode material, comprising a lithium-rich manganese-based cathode material and a coating layer LiAl, wherein the lithium-rich manganese-based cathode material has the molecular formula xLi2MnO3·(1-x)LiMO2, where M is one or more of the transition metals Ni, Co and Mn, and 0 < x < 1; the coating layer LiAl is formed by the decomposition of LiAlH4.

[0008] Secondly, the present invention provides a method for preparing a modified lithium-rich manganese-based cathode material, wherein the lithium-rich manganese-based cathode material xLi2MnO3·(1-x)LiMO2 and LiAlH4 are uniformly mixed by a solid-phase method or a liquid-phase method, and then annealed under an inert atmosphere to obtain the modified lithium-rich manganese-based cathode material.

[0009] Furthermore, the preparation method of lithium-rich manganese-based cathode material xLi2MnO3·(1-x)LiMO2 includes the following steps:

[0010] (1) The hydroxide precursor and lithium salt are uniformly mixed in a ball mill;

[0011] (2) After drying the mixture in step (1), it is heated and kept warm in an air or oxygen atmosphere in stages, and then cooled to obtain lithium-rich manganese-based cathode material xLi2MnO3·(1-x)LiMO2.

[0012] Furthermore, the hydroxide precursor in step (1) has the molecular formula Mn. 1-x’-y’ Ni x’ Co y’ (OH)2, where 0≤x'≤0.3, 0≤y'≤0.2; the lithium salt is Li2CO3 or LiOH; the molar ratio of Li in the lithium salt to the metal element contained in the hydroxide precursor, i.e., the lithium ratio, is 1.30-1.60;

[0013] In step (2), the staged calcination is carried out at a heating rate of 3℃ / min-5℃ / min. First, the temperature is raised to 450℃-600℃ and held for 3h-7h, and then the temperature is raised to 850℃-1020℃ and held for 10h-15h.

[0014] Furthermore, the solid-state method for preparing modified lithium-rich manganese-based cathode materials includes the following steps:

[0015] (1) The lithium-rich manganese-based cathode material xLi2MnO3·(1-x)LiMO2 prepared above was thoroughly mixed with LiAlH4 solid powder by mechanical grinding;

[0016] (2) The lithium-rich manganese-based cathode material obtained in step (1) is annealed with a mixture of LiAlH4 under an inert atmosphere and then cooled to room temperature to obtain the modified lithium-rich manganese-based cathode material.

[0017] Furthermore, in step (1), the molar ratio of xLi2MnO3·(1-x)LiMO2 to LiAlH4 is 100:(0.1-2); the mechanical grinding is ball milling or dry grinding, and the purity of LiAlH4 is ≥97%;

[0018] In step (2), the inert atmosphere is argon or an argon / hydrogen mixture, with argon accounting for more than 95% of the mixture; the annealing treatment is to heat to 250℃-400℃ at a heating rate of 3℃ / min-5℃ / min and anneal for 2h-3h.

[0019] Furthermore, the modified lithium-rich manganese-based cathode material is prepared by liquid-phase method, including the following steps:

[0020] (1) Dissolve the lithium-rich manganese-based cathode material xLi2MnO3·(1-x)LiMO2 and LiAlH4 solid powder obtained above in anhydrous ethanol and stir until uniform. Then place the mixed solution in an oven to dry.

[0021] (2) The lithium-rich manganese-based cathode material dried in step (1) is annealed with the LiAlH4 mixture under an inert atmosphere and then cooled to room temperature to obtain the modified lithium-rich manganese-based cathode material.

[0022] Furthermore, in step (1), the molar ratio of xLi2MnO3·(1-x)LiMO2 to LiAlH4 is 100:(0.1-2); the purity of LiAlH4 is ≥97%, and the concentration of LiAlH4 in the mixed solution is 0.38mol / mL-7.6mol / mL;

[0023] In step (2), the inert atmosphere is argon or an argon / hydrogen mixture, with argon accounting for more than 95% of the mixture; the annealing treatment is to heat to 250℃-400℃ at a heating rate of 3℃ / min-5℃ / min and anneal for 2h-3h.

[0024] Thirdly, this invention provides an application of a modified lithium-rich manganese-based cathode material in solid-state lithium batteries.

[0025] Furthermore, the modified lithium-rich manganese-based cathode material was used to assemble a sulfide all-solid-state lithium-ion battery. Electrochemical performance was tested at 60°C, a cycling current of 0.2C, and a voltage of 2.1V-4.6V. The first charge specific capacity was >263mAh / g, the first discharge specific capacity was >168mAh / g, and the capacity retention rate after 100 cycles was >80%.

[0026] Advantages and effects of the present invention:

[0027] The modified lithium-rich manganese-based cathode material of this invention simultaneously solves the problems of interfacial instability and poor transport dynamics in sulfide-based all-solid-state lithium-ion batteries, and can improve the first-cycle charge-discharge specific capacity and cycle stability of solid-state lithium-ion batteries. It comprehensively improves the first-cycle coulombic efficiency, cycle stability, rate performance and energy density of all-solid-state lithium-ion batteries. Moreover, the preparation method of this invention is simple to operate, environmentally friendly, non-toxic and harmless, economically adaptable and conducive to industrial application. Attached Figure Description

[0028] Figure 1 The graphs show the charge and discharge test curves for Examples 1, 6, and the control group.

[0029] Figure 2 The graphs show the cyclic performance tests for Examples 1, 6, and the control group. Detailed Implementation

[0030] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples.

[0031] A modified lithium-rich manganese-based cathode material includes a lithium-rich manganese-based cathode material and a coating layer LiAl. The lithium-rich manganese-based cathode material has the molecular formula xLi2MnO3·(1-x)LiMO2, where M is one or more of the transition metals Ni, Co and Mn, and 0 < x < 1. The coating layer LiAl is formed by the decomposition of LiAlH4.

[0032] A method for preparing a modified lithium-rich manganese-based cathode material involves uniformly mixing xLi2MnO3·(1-x)LiMO2 and LiAlH4 via a solid-phase or liquid-phase method, followed by annealing under an inert atmosphere to obtain the modified lithium-rich manganese-based cathode material. The specific process is as follows:

[0033] A method for preparing lithium-rich manganese-based cathode material xLi2MnO3·(1-x)LiMO2 includes the following steps:

[0034] (1) The hydroxide precursor and lithium salt are uniformly mixed in a ball mill. The molar ratio of Li in the lithium salt to the metal element contained in the hydroxide precursor is 1.30-1.60 (i.e., lithium ratio). The molecular formula of the hydroxide precursor is Mn. 1-x’-y’ Ni x’ Co y’ OH, where 0≤x'≤0.3, 0≤y'≤0.2; the lithium salt is Li2CO3 or LiOH;

[0035] (2) After drying the mixture in step (1), place it in a tube furnace and calcine it in an air or oxygen atmosphere. The temperature is increased at a rate of 3℃ / min-5℃ / min. First, the temperature is increased to 450℃-600℃ and held for 3h-7h. Then, the temperature is increased to 850℃-1020℃ and held for 10h-15h. After calcination, the mixture is cooled to obtain the lithium-rich manganese-based cathode material xLi2MnO3·(1-x)LiMO2.

[0036] The solid-state method for preparing modified lithium-rich manganese-based cathode materials includes the following steps:

[0037] (1) The lithium-rich manganese-based cathode material xLi2MnO3·(1-x)LiMO2 prepared above is mixed with LiAlH4 (purity ≥97%) solid powder by ball milling or dry grinding at a molar ratio of 100:(0.1-2);

[0038] (2) The lithium-rich manganese-based cathode material obtained in step (1) and the LiAlH4 mixture are placed in a tube furnace and heated to 250℃-400℃ at a heating rate of 3℃ / min-5℃ / min under an inert atmosphere of argon or argon / hydrogen mixture (argon content above 95%). The mixture is annealed for 2h-3h and then cooled to room temperature to obtain the modified lithium-rich manganese-based cathode material.

[0039] The preparation of modified lithium-rich manganese-based cathode materials by liquid-phase method includes the following steps:

[0040] (1) The lithium-rich manganese-based cathode material xLi2MnO3·(1-x)LiMO2 and LiAlH4 (purity ≥97%) solid powder prepared above were dissolved in anhydrous ethanol at a molar ratio of 100:(0.1-2), and stirred evenly to obtain a mixed solution with a LiAlH4 concentration of 0.38mol / mL-7.6mol / mL. Then the mixed solution was placed in an oven to dry.

[0041] (2) The dried lithium-rich manganese-based cathode material and the LiAlH4 mixture in step (1) are placed in a tube furnace and heated to 250℃-400℃ at a heating rate of 3℃ / min-5℃ / min under an inert atmosphere of argon or argon / hydrogen mixture (argon content above 95%). The mixture is annealed for 2h-3h and then cooled to room temperature to obtain the modified lithium-rich manganese-based cathode material.

[0042] An application of a modified lithium-rich manganese-based cathode material in solid-state lithium batteries: The modified lithium-rich manganese-based cathode material is used to assemble a sulfide all-solid-state lithium-ion battery. Electrochemical performance tests are conducted under the conditions of 60℃, cycling current of 0.2C and voltage of 2.1V-4.6V. The first charge specific capacity is >263mAh / g, the first discharge specific capacity is >168mAh / g, and the capacity retention rate after 100 cycles is >80%.

[0043] Example 1

[0044] A modified lithium-rich manganese-based cathode material includes a lithium-rich manganese-based cathode material and a coating layer LiAl. The molecular formula of the lithium-rich manganese-based cathode material is xLi₂MnO₃·(1-x)LiMO₂, where M is composed of Ni and Mn, and x = 0.45. The lithium-rich manganese-based cathode material is Li… 1.45 Mn 0.7 Ni 0.3 O 2.45 The coating layer LiAl is formed by the decomposition of LiAlH4.

[0045] This embodiment 1 describes a method for preparing a modified lithium-rich manganese-based cathode material, Li... 1.45 Mn 0.7 Ni 0.3 O 2.45 The modified lithium-rich manganese-based cathode material was obtained by uniformly mixing it with LiAlH4 via a solid-state method and then annealing it under an inert atmosphere. The specific process is as follows:

[0046] Lithium-rich manganese-based cathode material Li 1.45 Mn 0.7 Ni 0.3 O 2.45 The preparation method includes the following steps:

[0047] (1) The hydroxide precursor Mn 1-x’-y’ Ni x’ Co y’ OH (x'=0.3, y'=0) and Li2CO3 were uniformly mixed in a ball mill, according to the relationship between Li in Li2CO3 and the metallic element Mn contained in the hydroxide precursor. 0.7 Ni 0.3 The molar ratio (lithium content) is 1.45. Weigh out Li₂CO₃ and Mn. 0.7Ni 0.3 (OH)2;

[0048] (2) After drying the mixture from step (1), place it in a tube furnace and heat it to 600℃ at 4℃ / min for 7 hours in an air atmosphere. Then heat it to 900℃ at 4℃ / min for 15 hours. After the temperature drops to room temperature, lithium-rich manganese-based cathode material Li is obtained. 1.45 Mn 0.7 Ni 0.3 O 2.45 .

[0049] The solid-state method for preparing modified lithium-rich manganese-based cathode materials includes the following steps:

[0050] (1) The prepared lithium-rich manganese-based cathode material Li 1.45 Mn 0.7 Ni 0.3 O 2.45 The solid powder of LiAlH4 (purity: 97%) was placed in a mortar at a molar ratio of 100:0.5 and ground and mixed thoroughly.

[0051] (2) The lithium-rich manganese-based cathode material obtained in step (1) and the LiAlH4 mixture are placed in a tube furnace and heated to 400°C at 4°C / min under an argon atmosphere. After annealing for 2.5 h, the modified lithium-rich manganese-based cathode material is obtained after the temperature drops to room temperature.

[0052] Example 2

[0053] A modified lithium-rich manganese-based cathode material includes a lithium-rich manganese-based cathode material and a coating layer of LiAl. The molecular formula of the lithium-rich manganese-based cathode material is xLi₂MnO₃·(1-x)LiMO₂, where M is composed of Co and Mn, and x = 0.3. The lithium-rich manganese-based cathode material is Li 1.3 Mn 0.8 Co 0.2 O 2.3 The coating layer LiAl is formed by the decomposition of LiAlH4.

[0054] This embodiment 2 presents a method for preparing a modified lithium-rich manganese-based cathode material, Li... 1.3 Mn 0.8 Co 0.2 O 2.3 The modified lithium-rich manganese-based cathode material was obtained by uniformly mixing it with LiAlH4 via a solid-state method and then annealing it under an inert atmosphere. The specific process is as follows:

[0055] Lithium-rich manganese-based cathode material Li 1.3 Mn 0.8 Co 0.2 O 2.3 The preparation method includes the following steps:

[0056] (1) The hydroxide precursor Mn 1-x’-y’ Ni x’ Co y’ OH (x'=0, y'=0.2) and LiOH were uniformly mixed in a ball mill, according to the relationship between Li in LiOH and the metallic element Mn contained in the hydroxide precursor. 0.8 Co 0.2 The molar ratio (lithium content) is 1.3. Weigh out LiOH and Mn. 0.8 Co 0.2 (OH)2;

[0057] (2) After drying the mixture from step (1), place it in a tube furnace and heat it to 450°C at 5°C / min for 3 hours under an oxygen atmosphere. Then heat it to 850°C at 3°C / min for 10 hours. After the temperature drops to room temperature, lithium-rich manganese-based cathode material Li is obtained. 1.3 Mn 0.8 Co 0.2 O 2.3 .

[0058] The solid-state method for preparing modified lithium-rich manganese-based cathode materials includes the following steps:

[0059] (1) The prepared lithium-rich manganese-based cathode material Li 1.3 Mn 0.8 Co 0.2 O 2.3 The mixture was placed in a ball mill and mixed evenly with LiAlH4 (purity: 97%) solid powder at a molar ratio of 100:0.25;

[0060] (2) The lithium-rich manganese-based cathode material obtained in step (1) and the LiAlH4 mixture are placed in a tube furnace and heated to 250°C at 3°C / min under an argon / hydrogen mixed atmosphere (argon accounts for 95%). After annealing for 3 hours, the modified lithium-rich manganese-based cathode material is obtained after the temperature drops to room temperature.

[0061] Example 3

[0062] A modified lithium-rich manganese-based cathode material includes a lithium-rich manganese-based cathode material and a coating layer LiAl. The molecular formula of the lithium-rich manganese-based cathode material is xLi₂MnO₃·(1-x)LiMO₂, where M is composed of Ni, Co, and Mn, and x = 0.5. The lithium-rich manganese-based cathode material is Li 1.5 Mn 0.65 Ni 0.23 Co 0.12 O 2.5 The coating layer LiAl is formed by the decomposition of LiAlH4.

[0063] This embodiment 3 describes a method for preparing a modified lithium-rich manganese-based cathode material, Li... 1.5 Mn 0.65 Ni 0.23 Co 0.12 O 2.5 The modified lithium-rich manganese-based cathode material was obtained by uniformly mixing it with LiAlH4 via a solid-state method and then annealing it under an inert atmosphere. The specific process is as follows:

[0064] Lithium-rich manganese-based cathode material Li 1.5 Mn 0.65 Ni 0.23 Co 0.12 O 2.5 The preparation method includes the following steps:

[0065] (1) The hydroxide precursor Mn 1-x’-y’ Ni x’ Co y’ OH (x'=0.23, y'=0.12) and Li2CO3 were uniformly mixed in a ball mill, according to the ratio of Li in Li2CO3 to the metallic element Mn contained in the hydroxide precursor. 0.65 Ni 0.23 Co 0.12 The molar ratio (lithium content) is 1.5. Weigh out Li₂CO₃ and Mn. 0.65 Ni 0.23 Co 0.12 (OH)2;

[0066] (2) After drying the mixture from step (1), place it in a tube furnace and heat it to 550°C at 3°C / min for 5 hours in an air atmosphere. Then heat it to 900°C at 5°C / min for 12 hours. After the temperature drops to room temperature, lithium-rich manganese-based cathode material Li is obtained. 1.5 Mn 0.65 Ni 0.23 Co 0.12 O 2.5 .

[0067] The solid-state method for preparing modified lithium-rich manganese-based cathode materials includes the following steps:

[0068] (1) The prepared lithium-rich manganese-based cathode material Li 1.5 Mn 0.65 Ni 0.23 Co 0.12 O 2.5 The solid powder of LiAlH4 (purity: 97%) was placed in a mortar at a molar ratio of 100:0.1 and thoroughly ground and mixed.

[0069] (2) The lithium-rich manganese-based cathode material obtained in step (1) and the mixture of LiAlH4 are placed in a tube furnace and heated to 300°C at 5°C / min under an argon atmosphere. After annealing for 2 hours, the modified lithium-rich manganese-based cathode material is obtained after the temperature drops to room temperature.

[0070] Example 4

[0071] A modified lithium-rich manganese-based cathode material includes a lithium-rich manganese-based cathode material and a coating layer LiAl. The molecular formula of the lithium-rich manganese-based cathode material is xLi₂MnO₃·(1-x)LiMO₂, where M is composed of Ni, Co, and Mn, and x = 0.5. The lithium-rich manganese-based cathode material is Li 1.5 Mn 0.63 Ni 0.25 Co 0.12 O 2.5 The coating layer LiAl is formed by the decomposition of LiAlH4.

[0072] This embodiment 4 describes a method for preparing a modified lithium-rich manganese-based cathode material, Li... 1.5 Mn 0.63 Ni 0.25 Co 0.12 O 2.5 The modified lithium-rich manganese-based cathode material was obtained by uniformly mixing it with LiAlH4 via a solid-state method and then annealing it under an inert atmosphere. The specific process is as follows:

[0073] Lithium-rich manganese-based cathode material Li 1.5 Mn 0.63 Ni 0.25 Co 0.12 O 2.5 The preparation method includes the following steps:

[0074] (1) The hydroxide precursor Mn 1-x’-y’ Ni x’ Co y’ OH (x'=0.25, y'=0.12) and Li2CO3 were uniformly mixed in a ball mill, according to the ratio of Li in Li2CO3 to the metallic element Mn contained in the hydroxide precursor. 0.63 Ni 0.25 Co 0.12 The molar ratio (lithium content) is 1.5. Weigh out Li₂CO₃ and Mn. 0.63 Ni 0.25 Co 0.12 (OH)2;

[0075] (2) After drying the mixture from step (1), place it in a tube furnace and heat it to 550°C at 4°C / min for 5 hours in an air atmosphere. Then heat it to 900°C at 5°C / min for 12 hours. After the temperature drops to room temperature, lithium-rich manganese-based cathode material Li is obtained. 1.5 Mn 0.63 Ni 0.25 Co 0.12 O 2.5 .

[0076] The solid-state method for preparing modified lithium-rich manganese-based cathode materials includes the following steps:

[0077] (1) The prepared lithium-rich manganese-based cathode material Li 1.5 Mn 0.63 Ni 0.25 Co 0.12 O 2.5 The solid powder of LiAlH4 (purity: 97%) was placed in a mortar at a molar ratio of 100:1 and thoroughly ground and mixed.

[0078] (2) The lithium-rich manganese-based cathode material obtained in step (1) and the LiAlH4 mixture are placed in a tube furnace and heated to 400°C at 4°C / min under an argon atmosphere. After annealing for 2.5 h, the modified lithium-rich manganese-based cathode material is obtained after the temperature drops to room temperature.

[0079] Example 5

[0080] A modified lithium-rich manganese-based cathode material includes a lithium-rich manganese-based cathode material and a coating layer of LiAl. The lithium-rich manganese-based cathode material has the molecular formula xLi₂MnO₃·(1-x)LiMO₂, where M is Mn and x = 0.4. The lithium-rich manganese-based cathode material is Li... 1.4 MnO 2.4 The coating layer LiAl is formed by the decomposition of LiAlH4.

[0081] This Example 5 describes a method for preparing a modified lithium-rich manganese-based cathode material, Li... 1.4 MnO 2.4 The modified lithium-rich manganese-based cathode material was obtained by uniformly mixing it with LiAlH4 via a solid-state method and then annealing it under an inert atmosphere. The specific process is as follows:

[0082] Lithium-rich manganese-based cathode material Li 1.4 MnO 2.4 The preparation method includes the following steps:

[0083] (1) The hydroxide precursor Mn 1-x’-y’ Ni x’ Co y’OH (x'=0, y'=0) and LiOH are uniformly mixed in a ball mill. LiOH and Mn(OH)2 are weighed according to the molar ratio of Li in LiOH to Mn in the hydroxide precursor (lithium content) of 1.4.

[0084] (2) After drying the mixture from step (1), place it in a tube furnace and heat it to 600℃ at 3℃ / min for 7 hours under an oxygen atmosphere. Then heat it to 1020℃ at 4℃ / min for 15 hours. After the temperature drops to room temperature, lithium-rich manganese-based cathode material Li is obtained. 1.4 MnO 2.4 .

[0085] The solid-state method for preparing modified lithium-rich manganese-based cathode materials includes the following steps:

[0086] (1) The prepared lithium-rich manganese-based cathode material Li 1.4 MnO 2.4 The solid powder of LiAlH4 (purity: 97%) was mixed evenly in a ball mill at a molar ratio of 100:2.

[0087] (2) The lithium-rich manganese-based cathode material obtained in step (1) and the LiAlH4 mixture are placed in a tube furnace and heated to 300°C at 3°C / min under an argon / hydrogen mixed atmosphere (argon accounts for 96%). After annealing for 2 hours, the modified lithium-rich manganese-based cathode material is obtained after the temperature drops to room temperature.

[0088] Example 6

[0089] A modified lithium-rich manganese-based cathode material includes a lithium-rich manganese-based cathode material and a coating layer LiAl. The molecular formula of the lithium-rich manganese-based cathode material is xLi₂MnO₃·(1-x)LiMO₂, where M is composed of Ni and Mn, and x = 0.45. The lithium-rich manganese-based cathode material is Li… 1.45 Mn 0.7 Ni 0.3 O 2.45 The coating layer LiAl is formed by the decomposition of LiAlH4.

[0090] This embodiment 6 describes a method for preparing a modified lithium-rich manganese-based cathode material, Li... 1.45 Mn 0.7 Ni 0.3 O 2.45 The modified lithium-rich manganese-based cathode material was obtained by uniformly mixing it with LiAlH4 via a solid-state method and then annealing it under an inert atmosphere. The specific process is as follows:

[0091] Lithium-rich manganese-based cathode material Li 1.45 Mn 0.7 Ni 0.3 O 2.45The preparation method includes the following steps:

[0092] (1) The hydroxide precursor Mn 1-x’-y’ Ni x’ Co y’ OH (x'=0.3, y'=0) and Li2CO3 were uniformly mixed in a ball mill, according to the relationship between Li in Li2CO3 and the metallic element Mn contained in the hydroxide precursor. 0.7 Ni 0.3 The molar ratio (lithium content) is 1.45. Weigh out Li₂CO₃ and Mn. 0.7 Ni 0.3 (OH)2;

[0093] (2) After drying the mixture from step (1), place it in a tube furnace and heat it to 600℃ at 4℃ / min for 7 hours in an air atmosphere. Then heat it to 900℃ at 4℃ / min for 15 hours. After the temperature drops to room temperature, lithium-rich manganese-based cathode material Li is obtained. 1.45 Mn 0.7 Ni 0.3 O 2.45 .

[0094] The preparation of modified lithium-rich manganese-based cathode materials by liquid-phase method includes the following steps:

[0095] (1) The lithium-rich manganese-based cathode material Li prepared above 1.45 Mn 0.7 Ni 0.3 O 2.45 LiAlH4 (purity: 97%) solid powder was dissolved in anhydrous ethanol at a molar ratio of 100:0.5 and stirred until homogeneous to obtain a mixed solution with a LiAlH4 concentration of 1.9 mol / mL. The mixed solution was then dried in an oven.

[0096] (2) The dried lithium-rich manganese-based cathode material and the LiAlH4 mixture in step (1) are placed in a tube furnace and heated to 400°C at a heating rate of 4°C / min under an argon atmosphere. The mixture is annealed for 2.5 h and then cooled to room temperature to obtain the modified lithium-rich manganese-based cathode material.

[0097] Example 7

[0098] A modified lithium-rich manganese-based cathode material includes a lithium-rich manganese-based cathode material and a coating layer of LiAl. The molecular formula of the lithium-rich manganese-based cathode material is xLi₂MnO₃·(1-x)LiMO₂, where M is composed of Co and Mn, and x = 0.3. The lithium-rich manganese-based cathode material is Li 1.3 Mn 0.8 Co 0.2 O 2.3 The coating layer LiAl is formed by the decomposition of LiAlH4.

[0099] This embodiment 7 describes a method for preparing a modified lithium-rich manganese-based cathode material, Li... 1.3 Mn 0.8 Co 0.2 O 2.3 The modified lithium-rich manganese-based cathode material was obtained by uniformly mixing it with LiAlH4 via a solid-state method and then annealing it under an inert atmosphere. The specific process is as follows:

[0100] Lithium-rich manganese-based cathode material Li 1.3 Mn 0.8 Co 0.2 O 2.3 The preparation method includes the following steps:

[0101] (1) The hydroxide precursor Mn 1-x’-y’ Ni x’ Co y’ OH (x'=0, y'=0.2) and LiOH were uniformly mixed in a ball mill, according to the relationship between Li in LiOH and the metallic element Mn contained in the hydroxide precursor. 0.8 Co 0.2 The molar ratio (lithium content) is 1.3. Weigh out LiOH and Mn. 0.8 Co 0.2 (OH)2;

[0102] (2) After drying the mixture from step (1), place it in a tube furnace and heat it to 450°C at 5°C / min for 3 hours under an oxygen atmosphere. Then heat it to 850°C at 3°C / min for 10 hours. After the temperature drops to room temperature, lithium-rich manganese-based cathode material Li is obtained. 1.3 Mn 0.8 Co 0.2 O 2.3 .

[0103] The preparation of modified lithium-rich manganese-based cathode materials by liquid-phase method includes the following steps:

[0104] (1) The lithium-rich manganese-based cathode material Li prepared above 1.3 Mn 0.8 Co 0.2 O 2.5 LiAlH4 (purity: 97%) solid powder was dissolved in anhydrous ethanol at a molar ratio of 100:0.25 and stirred until homogeneous to obtain a mixed solution with a LiAlH4 concentration of 0.95 mol / mL. The mixed solution was then dried in an oven.

[0105] (2) The dried lithium-rich manganese-based cathode material and the LiAlH4 mixture in step (1) are placed in a tube furnace and heated to 250°C at a heating rate of 3°C / min under an argon / hydrogen mixed atmosphere (argon accounts for 96%). The mixture is annealed for 3 hours and then cooled to room temperature to obtain the modified lithium-rich manganese-based cathode material.

[0106] Example 8

[0107] A modified lithium-rich manganese-based cathode material includes a lithium-rich manganese-based cathode material and a coating layer LiAl. The molecular formula of the lithium-rich manganese-based cathode material is xLi₂MnO₃·(1-x)LiMO₂, where M is composed of Ni, Co, and Mn, and x = 0.5. The lithium-rich manganese-based cathode material is Li 1.5 Mn 0.65 Ni 0.23 Co 0.12 O 2.5 The coating layer LiAl is formed by the decomposition of LiAlH4.

[0108] This embodiment 8 describes a method for preparing a modified lithium-rich manganese-based cathode material, Li... 1.5 Mn 0.65 Ni 0.23 Co 0.12 O 2.5 The modified lithium-rich manganese-based cathode material was obtained by uniformly mixing it with LiAlH4 via a solid-state method and then annealing it under an inert atmosphere. The specific process is as follows:

[0109] Lithium-rich manganese-based cathode material Li 1.5 Mn 0.65 Ni 0.23 Co 0.12 O 2.5 The preparation method includes the following steps:

[0110] (1) The hydroxide precursor Mn 1-x’-y’ Ni x’ Co y’ OH (x'=0.23, y'=0.12) and Li2CO3 were uniformly mixed in a ball mill, according to the ratio of Li in Li2CO3 to the metallic element Mn contained in the hydroxide precursor. 0.65 Ni 0.23 Co 0.12 The molar ratio (lithium content) is 1.5. Weigh out Li₂CO₃ and Mn. 0.65 Ni 0.23 Co 0.12 (OH)2;

[0111] (2) After drying the mixture from step (1), place it in a tube furnace and heat it to 550°C at 3°C / min for 5 hours in an air atmosphere. Then heat it to 900°C at 5°C / min for 12 hours. After the temperature drops to room temperature, lithium-rich manganese-based cathode material Li is obtained. 1.5 Mn 0.65 Ni 0.23 Co 0.12 O 2.5 .

[0112] The preparation of modified lithium-rich manganese-based cathode materials by liquid-phase method includes the following steps:

[0113] (1) The lithium-rich manganese-based cathode material Li prepared above 1.5 Mn 0.65 Ni 0.23 Co 0.12 O 2.5 LiAlH4 (purity: 97%) solid powder was dissolved in anhydrous ethanol at a molar ratio of 100:0.1 and stirred until homogeneous to obtain a mixed solution with a LiAlH4 concentration of 0.38 mol / mL. The mixed solution was then dried in an oven.

[0114] (2) The dried lithium-rich manganese-based cathode material and the LiAlH4 mixture in step (1) are placed in a tube furnace and heated to 300°C at a heating rate of 5°C / min under an argon atmosphere. After annealing for 2 hours, the mixture is cooled to room temperature to obtain the modified lithium-rich manganese-based cathode material.

[0115] Example 9

[0116] A modified lithium-rich manganese-based cathode material includes a lithium-rich manganese-based cathode material and a coating layer LiAl. The molecular formula of the lithium-rich manganese-based cathode material is xLi₂MnO₃·(1-x)LiMO₂, where M is composed of Ni, Co, and Mn, and x = 0.5. The lithium-rich manganese-based cathode material is Li 1.5 Mn 0.63 Ni 0.25 Co 0.12 O 2.5 The coating layer LiAl is formed by the decomposition of LiAlH4.

[0117] This Example 9 describes a method for preparing a modified lithium-rich manganese-based cathode material, Li... 1.5 Mn 0.63 Ni 0.25 Co 0.12 O 2.5 The modified lithium-rich manganese-based cathode material was obtained by uniformly mixing it with LiAlH4 via a solid-state method and then annealing it under an inert atmosphere. The specific process is as follows:

[0118] Lithium-rich manganese-based cathode material Li1.5 Mn 0.63 Ni 0.25 Co 0.12 O 2.5 The preparation method includes the following steps:

[0119] (1) The hydroxide precursor Mn 1-x’-y’ Ni x’ Co y’ OH (x'=0.25, y'=0.12) and Li2CO3 were uniformly mixed in a ball mill, according to the ratio of Li in Li2CO3 to the metallic element Mn contained in the hydroxide precursor. 0.63 Ni 0.25 Co 0.12 The molar ratio (lithium content) is 1.5. Weigh out Li₂CO₃ and Mn. 0.63 Ni 0.25 Co 0.12 (OH)2;

[0120] (2) After drying the mixture from step (1), place it in a tube furnace and heat it to 550°C at 4°C / min for 5 hours in an air atmosphere. Then heat it to 900°C at 5°C / min for 12 hours. After the temperature drops to room temperature, lithium-rich manganese-based cathode material Li is obtained. 1.5 Mn 0.63 Ni 0.25 Co 0.12 O 2.5 .

[0121] The preparation of modified lithium-rich manganese-based cathode materials by liquid-phase method includes the following steps:

[0122] (1) The lithium-rich manganese-based cathode material Li prepared above 1.5 Mn 0.63 Ni 0.25 Co 0.12 O 2.5 LiAlH4 (purity: 97%) solid powder was dissolved in anhydrous ethanol at a molar ratio of 100:1 and stirred until homogeneous to obtain a mixed solution with a LiAlH4 concentration of 3.8 mol / mL. The mixed solution was then placed in an oven to dry.

[0123] (2) The dried lithium-rich manganese-based cathode material and the LiAlH4 mixture in step (1) are placed in a tube furnace and heated to 400°C at a heating rate of 4°C / min under an argon atmosphere. The mixture is annealed for 2.5 h and then cooled to room temperature to obtain the modified lithium-rich manganese-based cathode material.

[0124] Example 10

[0125] A modified lithium-rich manganese-based cathode material includes a lithium-rich manganese-based cathode material and a coating layer of LiAl. The lithium-rich manganese-based cathode material has the molecular formula xLi₂MnO₃·(1-x)LiMO₂, where M is Mn and x = 0.4. The lithium-rich manganese-based cathode material is Li... 1.4 MnO 2.4 The coating layer LiAl is formed by the decomposition of LiAlH4.

[0126] This embodiment 10 describes a method for preparing a modified lithium-rich manganese-based cathode material, Li... 1.4 MnO 2.4 The modified lithium-rich manganese-based cathode material was obtained by uniformly mixing it with LiAlH4 via a solid-state method and then annealing it under an inert atmosphere. The specific process is as follows:

[0127] Lithium-rich manganese-based cathode material Li 1.4 MnO 2.4 The preparation method includes the following steps:

[0128] (1) The hydroxide precursor Mn 1-x’-y’ Ni x’ Co y’ OH (x'=0, y'=0) and LiOH are uniformly mixed in a ball mill. LiOH and Mn(OH)2 are weighed according to the molar ratio of Li in LiOH to Mn in the hydroxide precursor (lithium content) of 1.4.

[0129] (2) After drying the mixture from step (1), place it in a tube furnace and heat it to 600℃ at 3℃ / min for 7 hours under an oxygen atmosphere. Then heat it to 1020℃ at 4℃ / min for 15 hours. After the temperature drops to room temperature, lithium-rich manganese-based cathode material Li is obtained. 1.4 MnO 2.4 .

[0130] The preparation of modified lithium-rich manganese-based cathode materials by liquid-phase method includes the following steps:

[0131] (1) The lithium-rich manganese-based cathode material Li prepared above 1.4 MnO 2.4 LiAlH4 (purity: 97%) solid powder was dissolved in anhydrous ethanol at a molar ratio of 100:2 and stirred until homogeneous to obtain a mixed solution with a LiAlH4 concentration of 7.6 mol / mL. The mixed solution was then placed in an oven to dry.

[0132] (2) The dried lithium-rich manganese-based cathode material and the LiAlH4 mixture in step (1) are placed in a tube furnace and heated to 300°C at a heating rate of 3°C / min under an argon / hydrogen mixed atmosphere (argon accounts for 96%). The mixture is annealed for 2 hours and then cooled to room temperature to obtain the modified lithium-rich manganese-based cathode material.

[0133] Performance testing:

[0134] Assembling a sulfide all-solid-state battery includes: a composite cathode composed of modified lithium-rich manganese-based cathode materials prepared in Examples 1 to 10, an LPSCl solid electrolyte, and elemental lithium anode. The specific process is as follows:

[0135] (1) 80 mg of solid electrolyte Li6PS5Cl was placed in a polycarbonate tube with a diameter of 10 mm and pressed with a pressure of 1.5 t. Ten sets were prepared simultaneously and in parallel, labeled as Examples 1 to 10.

[0136] (2) The modified lithium-rich manganese-based cathode materials prepared in Examples 1 to 10 were ground and mixed with Li6PS5Cl solid electrolyte and conductive agent vapor-grown carbon fiber (VGCF) in a mass ratio of 60:37:3 to obtain 10 sets of composite cathode powders. 5 mg of each powder was evenly distributed on one side of the LPSCl corresponding to Examples 1 to 10 in step (1) and pressed with a pressure of 3t.

[0137] (3) Take Li elemental substance and attach it to the other side of the solid electrolyte LPSCl in Examples 1 to 10 in step (2). Press it at 120 MPa to obtain the sulfide all-solid-state battery assembled in Examples 1 to 10.

[0138] The assembled sulfide all-solid-state batteries were subjected to electrochemical performance tests at corresponding rates and cycle numbers. The cycle test current was 0.2C (1C = 200mA / g), the test voltage was 2.1V-4.6V, and the test temperature was 60℃. The test results are detailed in Table 1.

[0139] Table of Electrochemical Performance Test Results for Examples 1 to 10

[0140]

[0141] As shown in Table 1, the modified lithium-rich manganese-based cathode material of this invention exhibits excellent first-cycle charge and discharge specific capacity and cycle performance when used in solid-state lithium-ion batteries.

[0142] The lithium-rich manganese-based cathode materials in Examples 1 and 6 are the same, the difference being that Example 1 uses a solid-phase method to prepare the modified lithium-rich manganese-based cathode material, while Example 6 uses a liquid-phase method to prepare the modified lithium-rich manganese-based cathode material. The lithium-rich manganese-based cathode material was used as a control group. Sulfide all-solid-state batteries were assembled with the modified lithium-rich manganese-based cathode materials from Examples 1 and 6 according to the above operations. Charge and discharge tests were conducted under the conditions of a cycle test current of 0.05C, a test voltage of 2.1V-4.8V, and a test temperature of 60℃. The cycle test current was adjusted to 0.2C for cycle performance testing. Figure 1 , Figure 2 As shown, compared with lithium-rich manganese-based cathode materials, the modified lithium-rich manganese-based cathode material of the present invention effectively improves the first-cycle charge-discharge specific capacity and cycle performance; and when the lithium-rich manganese-based cathode materials are the same, the electrochemical performance of the modified lithium-rich manganese-based cathode material prepared by the solid-phase method is better than that of the modified lithium-rich manganese-based cathode material prepared by the liquid-phase method.

[0143] In summary, the LiAl generated from the decomposition of LiAlH4 in this invention can coat lithium-rich manganese-based cathode materials with additional capacity to replenish the active lithium consumed in the initial cycle and reduce interfacial side reactions between the cathode and the electrolyte. At the same time, the H2 generated from the decomposition of LiAlH4 reacts with the unstable lattice oxygen on the surface of the lithium-rich manganese-based cathode material to generate oxygen vacancies. These oxygen vacancies provide additional lithium-ion migration channels, reduce the diffusion barrier, and improve interfacial ion transport kinetics. Through synergistic effects, the first charge-discharge specific capacity and cycle performance of solid-state lithium-ion batteries are effectively improved.

Claims

1. A modified lithium-rich manganese-based positive electrode material, characterized in that, The lithium-rich manganese-based positive electrode material and its coating layer LiAl, the molecular formula of the lithium-rich manganese-based positive electrode material is xLi2MnO3·(1-x)LiMO2, M is one or more of transition metals Ni, Co and Mn, and 0 2. A method of preparing the modified lithium-rich manganese-based cathode material of claim 1, characterized in that, The lithium-rich manganese-based positive electrode material xLi2MnO3·(1-x)LiMO2 and LiAlH4 are uniformly mixed by a solid phase method or a liquid phase method, and then annealing is performed under an inert atmosphere to obtain the modified lithium-rich manganese-based positive electrode material.

3. The method of producing a modified lithium-rich manganese-based cathode material according to claim 2, wherein The preparation method of the lithium-rich manganese-based positive electrode material xLi2MnO3·(1-x)LiMO2 comprises the following steps: (1) uniformly mixing hydroxide precursors and lithium salts in a ball mill; (2) drying the mixture of step (1) and then performing staged heating and holding calcination under an air or oxygen atmosphere, and then cooling to obtain the lithium-rich manganese-based positive electrode material xLi2MnO3·(1-x)LiMO2.

4. The method for preparing the modified lithium-rich manganese-based cathode material as described in claim 3, characterized in that, The formula of the hydroxide precursor in step (1) is Mn 1-x’-y’ Ni x’ Co y’ (OH)2, wherein 0≤x'≤0.3, 0≤y'≤0.2; the lithium salt is Li2CO3 or LiOH; the molar ratio of Li in the lithium salt to the metal elements contained in the hydroxide precursor is 1.30-1.60; The staged calcination in step (2) is to first heat to 450-600°C at a heating rate of 3-5°C / min, hold for 3-7h, and then heat to 850-1020°C, hold for 10-15h.

5. The method of producing a modified lithium-rich manganese-based cathode material according to claim 2, wherein The preparation of the modified lithium-rich manganese-based positive electrode material by a solid phase method comprises the following steps: (1) uniformly mixing the lithium-rich manganese-based positive electrode material xLi2MnO3·(1-x)LiMO2 and LiAlH4 solid powder by mechanical grinding; (2) annealing the mixture of the lithium-rich manganese-based positive electrode material and LiAlH4 obtained in step (1) under an inert atmosphere, and then cooling to room temperature to obtain the modified lithium-rich manganese-based positive electrode material.

6. The method for preparing the modified lithium-rich manganese-based cathode material as described in claim 5, characterized in that, In step (1), the molar ratio of xLi2MnO3·(1-x)LiMO2 to LiAlH4 is 100:(0.1-2); the mechanical grinding is ball milling or dry grinding, and the purity of LiAlH4 is ≥97%; In step (2), the inert atmosphere is argon or argon / hydrogen mixed gas, and the proportion of argon in the mixed gas is more than 95%; the annealing treatment is to heat to 250-400°C at a heating rate of 3-5°C / min, and hold for 2-3h.

7. The method of producing a modified lithium-rich manganese-based cathode material according to claim 2, wherein The preparation of the modified lithium-rich manganese-based positive electrode material by a liquid phase method comprises the following steps: (1) dissolving the lithium-rich manganese-based positive electrode material xLi2MnO3·(1-x)LiMO2 prepared above and LiAlH4 solid powder in anhydrous ethanol, stirring uniformly, and then drying the mixed solution in an oven; (2) annealing the mixture of the lithium-rich manganese-based positive electrode material and LiAlH4 after drying in step (1) under an inert atmosphere, and then cooling to room temperature to obtain the modified lithium-rich manganese-based positive electrode material.

8. The method for preparing the modified lithium-rich manganese-based cathode material as described in claim 7, characterized in that, In step (1), the molar ratio of xLi2MnO3·(1-x)LiMO2 to LiAlH4 is 100:(0.1-2); the purity of LiAlH4 is ≥97%, and the concentration of LiAlH4 in the mixed solution is 0.38-7.6mol / mL; The inert atmosphere in step (2) is argon or argon / hydrogen mixed gas, and the proportion of argon in the mixed gas is more than 95%; the annealing treatment is to heat to 250-400℃ at a heating rate of 3-5℃ / min, and to be annealed for 2-3h.

9. The modified lithium-rich manganese-based positive electrode material of claim 1 is used in solid-state lithium batteries.

10. The use of the modified lithium-rich manganese-based cathode material according to claim 9 in a solid-state lithium battery, characterized in that, The modified lithium-rich manganese-based positive electrode material is used to assemble a sulfide full-solid-state lithium ion battery, and the electrochemical performance is tested at 60℃, a cycle current of 0.2C and a voltage of 2.1V-4.6V, the first charge specific capacity is >263mAh / g, the first discharge specific capacity is >168mAh / g, and the capacity retention rate after 100 cycles is >80%.

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