Lithium-rich manganese-based positive electrode material modified by ammonium fluorotitanate and preparation method thereof

Abstract

The application provides a lithium-rich manganese-based positive electrode material modified by ammonium fluorotitanate and a preparation method 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 0x<1. The preparation method is as follows: first, the lithium-rich manganese-based positive electrode material and ammonium fluorotitanate 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 lithium-rich manganese-based positive electrode material modified by ammonium fluorotitanate. The material surface of the application integrates double-element (titanium and fluorine) doping, spinel phase and oxygen vacancies, and the first cycle coulomb efficiency and cycle performance of the lithium-rich manganese-based positive electrode material are improved. The performance improvement is attributed to the strong integrated surface, in which the oxygen vacancies remove the surface unstable oxygen and inhibit the irreversible oxygen release, and the titanium and fluorine doping helps to stabilize the surface structure of the material. The preparation method is simple in operation, environment-friendly, non-toxic and harmless, and has strong economic adaptability, and is conducive to industrial application.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium ion battery materials, and particularly provides a lithium-rich manganese-based positive electrode material modified by ammonium fluorotitanate and a preparation method thereof. BACKGROUND

[0002] At present, layered oxides are widely used as positive electrode materials in commercial lithium ion batteries due to their high plateau voltage and relatively high specific capacity. However, the conventional positive electrode materials with lower specific capacity cannot meet the requirements of the driving range of electric vehicles. Therefore, it is particularly necessary to develop a new generation of high-energy-density positive electrode materials.

[0003] The lithium-rich manganese-based layered positive electrode material has a high specific capacity of more than 250 mAh / g and a high operating voltage of 4.8 V, and is low in cost, and is widely concerned by researchers. The lithium-rich manganese-based layered positive electrode material has such a high specific capacity because the Li2MnO3 component in the lithium-rich manganese-based layered positive electrode material participates in the reaction as an active phase at a charging voltage higher than 4.5 V. However, the lithium-rich manganese-based layered positive electrode material still has the following key problems in actual use: 1) low first-cycle coulombic efficiency caused by oxygen release and irreversible movement of Li2O in the lattice; 2) poor rate performance caused by low electronic and lithium ion conductivity; 3) poor cycle stability; and 4) voltage decay during the cycle process.

[0004] In view of the above problems, surface modification is obviously an effective strategy to improve the electrochemical performance of the lithium-rich manganese-based positive electrode material. More specifically, a surface composed of surface doping, surface spinel phase and oxygen vacancies is constructed to inhibit irreversible oxygen release and stabilize the surface structure. For example, NH3 and CO2 have been proved to produce uniform oxygen vacancies and surface spinel phase structures to control oxygen release without affecting the structural integrity of the lithium-rich manganese-based positive electrode material. Previous studies mainly focused on constructing a surface combining surface spinel phase and oxygen vacancies through gas-solid heat treatment to improve the electrochemical performance of the lithium-rich manganese-based positive electrode material. Few studies consider introducing oxygen vacancies and spinel phases and doping double elements on the surface of the lithium-rich manganese-based positive electrode material at the same time, and strengthening the surface structure through in-situ surface reconstruction. Therefore, it is crucial to construct a surface structure with multiple functional components to improve the electrochemical performance of the lithium-rich manganese-based positive electrode material. SUMMARY

[0005] The technical task of the present application is to solve the above problems in the prior art and provide a lithium-rich manganese-based positive electrode material modified by ammonium fluorotitanate and a preparation method thereof.

[0006] The technical scheme adopted by the present application to solve its technical problems is: a lithium-rich manganese-based positive electrode material modified by ammonium fluorotitanate, the molecular formula of the lithium-rich manganese-based positive electrode material is xLi2MnO3·(1-x)LiMO2, M is one or several of transition metals Ni, Co and Mn, 0

[0007] The present application also provides a preparation method of the lithium-rich manganese-based positive electrode material modified by ammonium fluorotitanate, comprising the following steps:

[0008] (a) the positive electrode material xLi2MnO3·(1-x)LiMO2 is fully mixed with ammonium fluorotitanate by a solid-phase method at a mass ratio of 100:(0.2-5) to obtain a mixture of ammonium fluorotitanate and the positive electrode material;

[0009] (b) the mixture obtained in step (a) is annealed in an inert atmosphere to obtain the lithium-rich manganese-based positive electrode material modified by ammonium fluorotitanate.

[0010] Further, the solid-phase method in step (a) comprises ball milling or dry grinding.

[0011] Further, the inert atmosphere in step (b) is an argon atmosphere or a hydrogen-argon mixed atmosphere.

[0012] Further, the annealing step in step (b) is: heating to 250-400℃ at a heating rate of 3-5℃ / min for 2-3h, and then cooling to room temperature.

[0013] The present application also provides a preparation method of the lithium-rich manganese-based positive electrode material modified by ammonium fluorotitanate, comprising the following steps:

[0014] (1) the positive electrode material xLi2MnO3·(1-x)LiMO2 is fully mixed with ammonium fluorotitanate by a solid-phase method at a mass ratio of 100:(0.2-5) to obtain a mixture of ammonium fluorotitanate and the positive electrode material;

[0015] (2) the mixture obtained in step (1) is annealed in an inert atmosphere to obtain the lithium-rich manganese-based positive electrode material modified by ammonium fluorotitanate.

[0016] Further, the concentration of ammonium fluorotitanate in the mixed solution in step (1) is 0.0007-0.0196mol / L.

[0017] Further, the inert atmosphere in step (2) is an argon atmosphere or a hydrogen-argon mixed atmosphere.

[0018] Further, the annealing step in step (2) is: annealing at a temperature increasing rate of 3-5 ℃ / min to 250-400 ℃ for 2-3 h, and then cooling to room temperature.

[0019] The application further provides a preparation method of the lithium-rich manganese-based positive electrode material.

[0020] S1. uniformly mixing a hydroxide precursor and a lithium salt;

[0021] S2. drying the mixed material in S1 and then placing it in a tube furnace for calcination to obtain a lithium-ion battery lithium-rich manganese-based positive electrode material.

[0022] Further, the lithium salt in step S1 is Li2CO3 or LiOH, and the hydroxide precursor is Ni x’ Co y’ Mn 1-x’-y’ OH, wherein 0≤x'≤0.3 and 0≤y'≤0.2.

[0023] Further, the molar ratio of Li in the lithium salt to the metal element M contained in the precursor, i.e., the lithium ratio, is 1.30-1.60 in step S1.

[0024] Further, the mixing in step S1 is performed in a ball mill, and the calcination in step S2 is performed in an air or oxygen atmosphere in a tube furnace.

[0025] Further, the calcination temperature in step S2 is: first increasing the temperature to 450-600 ℃ and maintaining the temperature for 3-7 h, then continuously increasing the temperature to 850-1020 ℃ and maintaining the temperature for 10-15 h, and then cooling.

[0026] Compared with the prior art, the application has the following beneficial effects:

[0027] The lithium-rich manganese-based positive electrode material modified by the ammonium fluorotitanate in the application integrates double-element (titanium and fluorine) doping, spinel phase and oxygen vacancies on the surface, and improves the first-cycle coulombic efficiency and cycle performance of the lithium-rich manganese-based positive electrode material. The performance improvement is attributed to the strong integrated surface, in which the oxygen vacancies and strong Ti-O and M-F bonds help to remove unstable oxygen on the surface and inhibit the irreversible oxygen release, and the first-cycle coulombic efficiency of the material is obviously improved. The doping of titanium and fluorine helps to stabilize the surface structure of the material and is beneficial to the improvement of cycle stability. The preparation method is simple in operation, environmentally friendly, non-toxic and harmless, and has strong economic adaptability, and is conducive to industrial application. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a first discharge curve diagram of examples 1-3 and comparative example 1 of the application;

[0029] Figure 2is the cycle curve of the present application examples 1-3 and comparative example 1 at 0.5C

[0030] Figure 3 is the first discharge curve of the present application examples 6-8 and comparative example 1;

[0031] Figure 4 is the cycle curve of the present application examples 6-8 and comparative example 1 at 0.5C. DETAILED DESCRIPTION

[0032] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application is further described in detail below in combination with examples. It should be understood that the specific examples described herein are only used to explain the present application and do not limit the present application.

[0033] Example 1

[0034] 1) Preparation of lithium-rich manganese-based positive electrode material matrix

[0035] According to the experimental requirements, a certain stoichiometric ratio of precursors Ni 0.22 Co 0.11 Mn 0.67 (OH)2 and Li2CO3 were placed in a ball mill and mixed uniformly, the lithium content was Li:M(Ni+Co+Mn)=1.5(molar ratio), then placed in a tube furnace and heated to 550℃ at 3℃ / min in air atmosphere, and then heated to 900℃ at 5℃ / min for 12h, and then cooled to room temperature, to obtain Li 1.2 Mn 0.5 Ni 0.2 Co 0.1 O2.

[0036] 2) Preparation of fluorotitanate ammonium modified lithium-rich manganese-based positive electrode material by solid phase method

[0037] The obtained Li 1.2 Mn 0.5 Ni 0.2 Co 0.1 O2 and fluorotitanate ammonium were mixed in a mortar at a mass ratio of 100:0.5, and the uniformly ground material was placed in a tube furnace in an argon atmosphere, heated to 300℃ at a heating rate of 5℃ / min for 2h, and then cooled to room temperature to obtain fluorotitanate ammonium modified lithium-rich manganese-based positive electrode material.

[0038] Example 2

[0039] 1) Preparation of lithium-rich manganese-based positive electrode material matrix

[0040] According to the experimental requirements, a certain stoichiometric ratio of precursors Ni 0.22 Co0.11 Mn 0.67 (OH)2 and Li2CO3 were placed in a ball mill and mixed uniformly, with lithium content Li:M(Ni+Co+Mn) = 1.5 (molar ratio), then placed in a tube furnace and heated to 550℃ at a rate of 3℃ / min in air atmosphere for 5h, then heated to 900℃ at a rate of 5℃ / min for 12h, and after the temperature dropped to room temperature, Li 1.2 Mn 0.5 Ni 0.2 Co 0.1 O2;

[0041] 2) Preparation of ammonium fluorotitanate synergistically modified lithium-rich manganese-based positive electrode material by solid phase method

[0042] The obtained Li 1.2 Mn 0.5 Ni 0.2 Co 0.1 O2 was mixed with ammonium fluorotitanate in a mortar at a mass ratio of 100:1, and the uniformly ground material was placed in a tube furnace in argon atmosphere, heated to 250℃ at a rate of 3℃ / min for annealing for 3h, and after the temperature dropped to room temperature, the ammonium fluorotitanate synergistically modified lithium-rich manganese-based positive electrode material was obtained.

[0043] Example 3

[0044] 1) Preparation of lithium-rich manganese-based positive electrode material matrix

[0045] The precursors Ni 0.25 Co 0.12 Mn 0.63 (OH)2 and Li2CO3 were placed in a ball mill and mixed uniformly, with lithium content Li:M(Ni+Co+Mn) = 1.45 (molar ratio), then placed in a tube furnace and heated to 550℃ at a rate of 3℃ / min in air atmosphere for 5h, then heated to 900℃ at a rate of 5℃ / min for 12h, and after the temperature dropped to room temperature, Li 1.16 Mn 0.5 Ni 0.2 Co 0.1 O2;

[0046] 2) Preparation of ammonium fluorotitanate synergistically modified lithium-rich manganese-based positive electrode material by solid phase method

[0047] The obtained Li 1.16 Mn 0.5 Ni 0.2 Co 0.1O2 and ammonium fluorotitanate were mixed in a mortar at a mass ratio of 100:3, the uniformly ground material was placed in a tube furnace in an argon atmosphere, and was heated to 300°C at a heating rate of 5°C / min for annealing for 3h. After the temperature dropped to room temperature, the lithium-rich manganese-based positive electrode material modified by ammonium fluorotitanate was obtained.

[0048] Example 4

[0049] 1) Preparation of lithium-rich manganese-based positive electrode material matrix

[0050] The precursors Ni 0.25 Co 0.12 Mn 0.63 (OH)2 and Li2CO3 were placed in a ball mill and mixed uniformly, the lithium content was Li:M(Ni+Co+Mn) = 1.45 (molar ratio), and then placed in a tube furnace and heated to 550°C at a rate of 3°C / min in an air atmosphere for 5h, and then heated to 900°C at a rate of 5°C / min for 12h. After the temperature dropped to room temperature, Li 1.16 Mn 0.5 Ni 0.2 Co 0.1 O2 was obtained.

[0051] 2) Preparation of lithium-rich manganese-based positive electrode material modified by ammonium fluorotitanate by solid phase method

[0052] The obtained Li 1.16 Mn 0.5 Ni 0.2 Co 0.1 O2 and ammonium fluorotitanate were mixed in a mortar at a mass ratio of 100:0.2, the uniformly ground material was placed in a tube furnace in an argon atmosphere, and was heated to 350°C at a heating rate of 3°C / min for annealing for 2h. After the temperature dropped to room temperature, the lithium-rich manganese-based positive electrode material modified by ammonium fluorotitanate was obtained.

[0053] Example 5

[0054] 1) Preparation of lithium-rich manganese-based positive electrode material matrix

[0055] The precursors Ni 0.2 Co 0.1 Mn 0.7 (OH)2 and Li2CO3 were placed in a ball mill and mixed uniformly, the lithium content was Li:M(Ni+Co+Mn) = 1.55 (molar ratio), and then placed in a tube furnace and heated to 550°C at a rate of 3°C / min in an air atmosphere for 5h, and then heated to 900°C at a rate of 5°C / min for 12h. After the temperature dropped to room temperature, Li 1.24 Mn 0.56 Ni 0.16Co 0.08 O2;

[0056] 2) Preparation of ammonium fluorotitanate synergistically modified lithium-rich manganese-based positive electrode material by solid phase method

[0057] Li 1.24 Mn 0.56 Ni 0.16 Co 0.08 O2 and ammonium fluorotitanate in a mortar at a mass ratio of 100:5, and the uniformly ground material is placed in a tube furnace in an argon atmosphere, heated to 350°C at a heating rate of 3°C / min for 3h annealing, and after the temperature drops to room temperature, ammonium fluorotitanate synergistically modified lithium-rich manganese-based positive electrode material is obtained.

[0058] Example 6

[0059] 1) Preparation of lithium-rich manganese-based positive electrode material matrix

[0060] According to the experimental requirements, a certain stoichiometric ratio of precursors Ni 0.2 Co 0.1 Mn 0.7 (OH)2 and Li2CO3 are placed in a ball mill and mixed uniformly, the lithium content is Li:M(Ni+Co+Mn)=1.55(molar ratio), then placed in a tube furnace and heated to 550°C at 3°C / min in air atmosphere for 5h, then heated to 900°C at 5°C / min for 12h, and after the temperature drops to room temperature, Li 1.24 Mn 0.56 Ni 0.16 Co 0.08 O2;

[0061] 2) Preparation of ammonium fluorotitanate synergistically modified lithium-rich manganese-based positive electrode material by liquid phase method

[0062] Li 1.24 Mn 0.56 Ni 0.16 Co 0.08 O2 and ammonium fluorotitanate at a mass ratio of 100:0.5 in deionized water for 12h, at this time the concentration of ammonium fluorotitanate is 0.0019mol / L; the uniformly stirred material is placed in a 120°C oven for drying for 12h, then placed in a tube furnace in an argon atmosphere, heated to 400°C at a heating rate of 5°C / min for 2h annealing, and after the temperature drops to room temperature, ammonium fluorotitanate synergistically modified lithium-rich manganese-based positive electrode material is obtained.

[0063] Example 7

[0064] 1) Preparation of lithium-rich manganese-based positive electrode material matrix

[0065] According to the experimental requirements, a certain stoichiometric ratio of precursors Ni0.22 Co 0.11 Mn 0.67 (OH)2 and Li2CO3 were placed in a ball mill and mixed uniformly, the lithium amount was Li:M(Ni+Co+Mn)=1.5(molar ratio), then placed in a tube furnace and heated to 550℃ at a rate of 3℃ / min in air atmosphere for 5h, then heated to 900℃ at a rate of 5℃ / min for 12h, after the temperature dropped to room temperature, Li 1.2 Mn 0.5 Ni 0.2 Co 0.1 O2;

[0066] 2) Preparation of ammonium fluorotitanate synergistically modified lithium-rich manganese-based positive electrode material by liquid phase method

[0067] The obtained Li 1.2 Mn 0.5 Ni 0.2 Co 0.1 O2 was stirred with ammonium fluorotitanate at a mass ratio of 100:1 in deionized water for 12h, at this time the concentration of ammonium fluorotitanate was 0.0039mol / L; the uniformly stirred material was placed in a 120℃ oven and dried for 12h, then placed in a tube furnace in argon atmosphere, heated to 350℃ at a rate of 3℃ / min and annealed for 3h, after the temperature dropped to room temperature, the ammonium fluorotitanate synergistically modified lithium-rich manganese-based positive electrode material was obtained.

[0068] Example 8

[0069] 1) Preparation of lithium-rich manganese-based positive electrode material matrix

[0070] The precursors Ni 0.22 Co 0.11 Mn 0.67 (OH)2 and Li2CO3 were placed in a ball mill and mixed uniformly, the lithium amount was Li:M(Ni+Co+Mn)=1.5(molar ratio), then placed in a tube furnace and heated to 550℃ at a rate of 3℃ / min in air atmosphere for 5h, then heated to 900℃ at a rate of 5℃ / min for 12h, after the temperature dropped to room temperature, Li 1.2 Mn 0.5 Ni 0.2 Co 0.1 O2;

[0071] 2) Preparation of ammonium fluorotitanate synergistically modified lithium-rich manganese-based positive electrode material by liquid phase method

[0072] The obtained Li 1.2 Mn 0.5 Ni 0.2 Co 0.1O2 and ammonium fluorotitanate were stirred in deionized water at a mass ratio of 100:3 for 12 h, at which time the ammonium fluorotitanate concentration was 0.0117 mol / L; the uniformly stirred material was placed in a 120°C oven to dry for 12 h, and then was placed in a tube furnace in an argon atmosphere, and was heated to 300°C at a heating rate of 5°C / min and was annealed for 3 h; after the temperature was reduced to room temperature, the ammonium fluorotitanate synergistically modified lithium-rich manganese-based positive electrode material was obtained.

[0073] Example 9

[0074] 1) Preparation of a lithium-rich manganese-based positive electrode material matrix

[0075] The precursors Ni 0.2 Co 0.1 Mn 0.7 (OH)2 and Li2CO3 were placed in a ball mill and mixed uniformly, the lithium amount was Li:M(Ni+Co+Mn)=1.55 (molar ratio), and then were placed in a tube furnace and heated to 550°C at 3°C / min in an air atmosphere, and were held for 5 h, and then were heated to 900°C at 5°C / min, and were held for 12 h; after the temperature was reduced to room temperature, Li 1.24 Mn 0.56 Ni 0.16 Co 0.08 O2 was obtained.

[0076] 2) Preparation of an ammonium fluorotitanate synergistically modified lithium-rich manganese-based positive electrode material by a liquid phase method

[0077] The obtained Li 1.24 Mn 0.56 Ni 0.16 Co 0.08 O2 was stirred in deionized water at a mass ratio of 100:0.2 for 12 h, at which time the ammonium fluorotitanate concentration was 0.0007 mol / L; the uniformly stirred material was placed in a 120°C oven to dry for 12 h, and then was placed in a tube furnace in an argon atmosphere, and was heated to 250°C at a heating rate of 5°C / min and was annealed for 3 h; after the temperature was reduced to room temperature, the ammonium fluorotitanate synergistically modified lithium-rich manganese-based positive electrode material was obtained.

[0078] Example 10

[0079] 1) Preparation of a lithium-rich manganese-based positive electrode material matrix

[0080] The precursors Ni 0.2 Co 0.1 Mn 0.7Li2CO3 were placed in a ball mill and mixed uniformly, the lithium content was Li:M(Ni+Co+Mn) = 1.55, then placed in a tube furnace and heated to 550℃ at a rate of 3℃ / min in air atmosphere for 5h, then heated to 900℃ at a rate of 5℃ / min for 12h, after the temperature dropped to room temperature, Li 1.24 Mn 0.56 Ni 0.16 Co 0.08 O2;

[0081] 2) Liquid phase method for preparing ammonium fluorotitanate synergistically modified lithium-rich manganese-based positive electrode material

[0082] Li 1.24 Mn 0.56 Ni 0.16 Co 0.08 O2 was mixed with ammonium fluorotitanate at a mass ratio of 100:5 in deionized water for 12h, at this time the concentration of ammonium fluorotitanate was 0.0196mol / L; the uniformly stirred material was placed in a 120℃ oven and dried for 12h, then placed in a tube furnace in argon atmosphere, heated to 300℃ at a rate of 3℃ / min and annealed for 3h, after the temperature dropped to room temperature, the ammonium fluorotitanate synergistically modified lithium-rich manganese-based positive electrode material was obtained.

[0083] Comparative Example 1

[0084] The preparation method of the lithium-rich manganese-based positive electrode material is as follows:

[0085] According to the experimental requirements, a certain stoichiometric ratio of precursors Ni 0.22 Co 0.11 Mn 0.67 Li2CO3 were placed in a ball mill and mixed uniformly, the mass of the precursor was 3g, the lithium content was Li:M(Ni+Co+Mn) = 1.5(molar ratio), then placed in a tube furnace and heated to 550℃ at a rate of 3℃ / min in air atmosphere for 5h, then heated to 900℃ at a rate of 5℃ / min for 12h, after the temperature dropped to room temperature, Li 1.2 Mn 0.5 Ni 0.2 Co 0.1 O2;

[0086] Electrochemical performance test

[0087] The lithium-rich manganese-based positive electrode material powder prepared in Examples 1-10 and Comparative Example 1 was mixed with acetylene black and polyvinylidene fluoride (mass ratio 90:5:5), and an appropriate amount of N-methyl pyrrolidone was added as a dispersant to grind into a slurry; then the slurry was uniformly coated on an aluminum foil, vacuum dried at 120 DEG C for 12 h, and then the dried electrode sheet was rolled using a roll machine, and the aluminum foil was cut into a circular electrode sheet with a diameter of 1 cm using a slicing machine. A half battery was assembled in an argon atmosphere glove box, wherein the water partial pressure was ≤0.1 ppm and the oxygen partial pressure was ≤0.1 ppm. A lithium ion secondary battery was assembled with lithium metal as the counter electrode and 1M LiPF6 (FEC / EC / DMC, volume ratio 1:1:1) solution as the electrolyte. Then, the first charge and discharge specific capacity and the first efficiency of the battery were tested under the conditions of a constant current charge and discharge mode at room temperature, a voltage range of 2.0-4.6 V, and a current density of 0.05C (1C = 200 mAh g -1 -1). The discharge specific capacity after 100 cycles, the capacity retention rate, were tested under the conditions of a current density of 0.5C (1C = 200 mAh g -1 -1). The test results are shown in Table 1 and Figures 1-4

[0088] Table 1

[0089]

[0090] As can be seen from Table 1 and Figures 1-4 , compared with Comparative Example 1, the first discharge specific capacity, the first efficiency and the capacity retention rate after 100 cycles of the lithium-rich manganese-based positive electrode material modified by the ammonium fluorotitanate in Examples 1-10 are significantly improved. Compared with Examples 4-5, the lithium-rich manganese-based positive electrode material prepared in Examples 1-3 has a more obvious effect on improving the first efficiency, the discharge specific capacity and the cycle performance. Compared with Examples 9-10, the lithium-rich manganese-based positive electrode material prepared in Examples 6-8 has a more obvious effect on improving the first efficiency, the discharge specific capacity and the cycle performance. It is shown that the ammonium fluorotitanate modification strategy in Examples 1-10 constructs a complete surface structure containing oxygen vacancies, spinel phase, fluorine and titanium co-doping and other multifunctional components on the surface of the lithium-rich manganese-based positive electrode material, and the surface reconstruction is attributed to the reaction of the NH3, HF and TiF4 gases after decomposition with the LRMO at high temperature. The first efficiency, the discharge specific capacity and the cycle performance of the lithium-rich manganese-based positive electrode material can be effectively improved.

[0091] The above technical solutions set forth the technical idea of the present application, which cannot limit the protection scope of the present application. Any modification and modification of the above technical solutions according to the technical essence of the present application, which does not deviate from the content of the technical solutions of the present application, belongs to the protection scope of the technical solutions of the present application.​

Claims

1. A method for preparing a lithium-rich manganese-based cathode material modified with ammonium fluorotitanate, characterized in that: The molecular formula of the lithium-rich manganese-based cathode material is xLi2MnO3·(1-x)LiMO2, where M is one or more of the transition metals Ni, Co and Mn, and 0 < x < 1. The lithium-rich manganese-based cathode material and ammonium fluorotitanate are mixed at a mass ratio of 100:(0.2-5) by a solid-phase or liquid-phase method, and then annealed at 250℃-400℃ for 2h-3h under an inert atmosphere to obtain the ammonium fluorotitanate-modified lithium-rich manganese-based cathode material. The preparation method of the lithium-rich manganese-based cathode material is as follows: A lithium salt and a hydroxide precursor are uniformly mixed and calcined. The mixture is first heated to 450℃-600℃ and held for 3-7 hours, then further heated to 850℃-1020℃ and held for 10-15 hours to obtain the lithium-rich manganese-based cathode material. The lithium salt is Li₂CO₃ or LiOH, and the hydroxide precursor is Ni. x’ Co y’ Mn 1-x’-y’ OH, wherein 0≤x'≤0.3, 0≤y'≤0.2; the molar ratio of Li in the lithium salt to the metal element contained in the hydroxide precursor is 1.30-1.

60.

2. The method for preparing an ammonium fluorotitanate-modified lithium-rich manganese-based cathode material according to claim 1, characterized in that: Includes the following steps: (a) The lithium-rich manganese-based cathode material xLi2MnO3·(1-x)LiMO2 and the ammonium fluorotitanate are thoroughly mixed by a solid-state method at a mass ratio of 100:(0.2-5). The solid-state method includes ball milling or dry grinding to obtain a mixture of the ammonium fluorotitanate and the lithium-rich manganese-based cathode material. (b) The mixture obtained in step (a) is annealed in an inert atmosphere to obtain the ammonium fluorotitanate modified lithium-rich manganese-based cathode material; during annealing, the temperature is increased to 250℃-400℃ at a heating rate of 3℃ / min-5℃ / min and annealed for 2h-3h, and then cooled to room temperature; the inert atmosphere is an argon atmosphere or a hydrogen-argon mixed atmosphere.

3. The method for preparing an ammonium fluorotitanate-modified lithium-rich manganese-based cathode material according to claim 1, characterized in that: Includes the following steps: (1) The lithium-rich manganese-based cathode material xLi2MnO3·(1-x)LiMO2 and the ammonium fluorotitanate were dissolved in water at a mass ratio of 100:(0.2-5) and stirred until homogeneous. The concentration of ammonium fluorotitanate in the mixture was 0.0007mol / L-0.0196mol / L. The mixture was then placed in an oven at 80℃-120℃ and dried for 6h-12h to obtain a mixture of ammonium fluorotitanate and lithium-rich manganese-based cathode material. (2) The mixture obtained in step (1) is annealed in an inert atmosphere to obtain the lithium-rich manganese-based cathode material modified with ammonium fluorotitanate; during annealing, the temperature is increased to 250℃-400℃ at a heating rate of 3℃ / min-5℃ / min and annealed for 2h-3h, and then cooled to room temperature; the inert atmosphere is an argon atmosphere or a hydrogen-argon mixed atmosphere.

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