F / Mg co-doped precursor materials, single-crystal lithium-rich manganese-based cathode materials and their preparation methods

Abstract

This invention relates to the field of lithium-ion battery technology, and discloses F / Mg co-doped precursor materials, single-crystal lithium-rich manganese-based cathode materials, and their preparation methods. The preparation method of the F / Mg co-doped precursor material includes the following steps: A1 preparing Mg-containing precursor materials... 2+ sulfate solution, containing F ‑ An alkaline solution was mixed, reacted, and separated to obtain a solid residue and a clear liquid. The solid residue and clear liquid were then subjected to a hydrothermal reaction under high pressure, followed by separation, washing, and drying to obtain the F / Mg co-doped precursor material. The amount of surfactant used was 0.1–10 wt% of the hydrothermal reaction raw materials. The preparation of F / Mg co-doped precursor materials with single-crystal morphology using co-precipitation, hydrothermal treatment, and high-temperature sintering can solve the problem of continuous voltage and capacity decay in multi-element doped lithium-rich manganese-based cathode materials.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and more specifically, to F / Mg co-doped precursor materials, single-crystal lithium-rich manganese-based cathode materials, and their preparation methods. Background Technology

[0002] Lithium-ion batteries possess advantages such as light weight, high energy density, no memory effect, long cycle life, and environmental friendliness, making them widely used in various fields including 3C electronic products and electric vehicles. The widespread adoption of lithium-ion batteries has changed people's lifestyles, and the increasing convenience of daily life has led to ever-increasing demands for the capacity and safety of lithium-ion batteries. The performance of a lithium-ion battery depends on the positive electrode material, negative electrode material, and electrolyte, among which lithium-rich manganese-based positive electrode materials exhibit performance exceeding 250 mAh / g. -1 With its advantages of ultra-high discharge specific capacity, low cost, non-toxicity and high thermal stability, it is regarded as the most promising next-generation lithium-ion battery cathode material.

[0003] Lithium-rich manganese-based cathode materials also suffer from several performance drawbacks, primarily low initial coulombic efficiency and significant voltage and capacity degradation during battery cycling. While initial coulombic efficiency can be significantly improved through surface modification, the rapid and significant voltage and capacity degradation during battery cycling remains a major factor affecting the electrochemical performance of lithium-rich manganese-based cathode materials.

[0004] To address the issue of voltage and capacity decay during battery cycling, ion doping has been proposed to improve lithium-rich manganese-based cathode materials. For example, using fluorine for 0-site doping can reduce the dissolution and loss of transition metals on the material surface, thereby inhibiting changes in the material structure and improving and stabilizing its electrochemical performance.

[0005] For example, patent CN112234176A provides a lithium-rich manganese-based precursor and its preparation method, a lithium-rich manganese-based cathode material and its preparation method, and a lithium-ion battery. It utilizes a dual-system co-precipitation method to co-dope F / Mg in the precursor material, effectively and fully dispersing the dopant elements on the material surface and in the bulk phase, thus improving the lithium-rich manganese-based cathode material. However, the aforementioned F / Mg-doped lithium-rich manganese-based cathode material exhibits a polycrystalline morphology of spherical secondary particles. This, along with other commonly used multi-element doped electrode materials, results in poor mechanical properties. This leads to inherent problems with polycrystalline particles, such as particle breakage and poor structural stability due to stress concentration during cycling, resulting in a certain degree of voltage and capacity decay during battery cycling.

[0006] Based on the above, there is an urgent need for a preparation process that can improve the structural stability of F / Mg co-doped lithium-rich manganese-based cathode materials. Summary of the Invention

[0007] The technical problem to be solved by this invention:

[0008] Currently, in lithium-rich manganese-based cathode materials for lithium-ion batteries, multi-element doping is used to reduce lattice oxygen loss and surface transition metal dissolution, thereby stabilizing the crystal structure and improving electrochemical performance. However, most existing multi-element doped lithium-rich manganese-based cathode materials exhibit a polycrystalline morphology, resulting in poor mechanical properties. This can lead to problems such as particle breakage and poor structural stability during cycling due to stress concentration, and still result in a certain degree of voltage and capacity decay.

[0009] The technical solution adopted in this invention is as follows:

[0010] This invention provides a method for preparing F / Mg co-doped precursor materials, comprising the following steps:

[0011] A1 was prepared containing Mg 2+ A sulfate solution and an alkaline solution containing F- are mixed, reacted, and separated to obtain a solid residue and a clear liquid.

[0012] A2 takes solid residue and clear liquid, adds surfactant, and places under high pressure to carry out hydrothermal reaction. After separation, washing and drying, the F / Mg co-doped precursor material is obtained.

[0013] Preferably, the Mg-containing 2+ The sulfate solution comprises NiSO4, CoSO4, MnSO4, and MgSO4, and is prepared from NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O, and MgSO4 as raw materials; and in the sulfate solution, Ni 2+ Co 2+ and Mn 2+ The sum of the ion concentrations is 1–4 mol / L.

[0014] Preferably, the F-containing - The alkaline solution includes Na₂CO₃, NH₄F, and Na₃C₆H₅O₇·2H₂O, and the amount of F in the alkaline solution is controlled. - The concentration of Mn in the sulfate solution 2+ The concentration is 210-240%.

[0015] Preferably, in step A1, the reaction time after mixing is 6 to 18 hours, the reaction temperature is 40 to 60°C, and the pH value of the reaction environment is 7.5 to 8.5.

[0016] Preferably, in step A2, the solid content of the mixture of solid residue and clear liquid is 20-50%.

[0017] Preferably, in step A2, during the hydrothermal reaction, the temperature is controlled at 80–180°C and the reaction time is 6–48 h.

[0018] Preferably, the surfactant comprises one or more of polyvinylpyrrolidone, sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium hexadecyl sulfate, and sodium hexadecyl sulfonate, and the amount of surfactant used is 0.1 to 10 wt% of the hydrothermal reaction raw materials.

[0019] The present invention also provides an F / Mg co-doped precursor material prepared by the above preparation method.

[0020] The present invention also provides a single-crystal lithium-rich manganese-based cathode material, the raw materials of which include the F / Mg co-doped precursor material prepared by the above preparation method or the above-mentioned F / Mg co-doped precursor material.

[0021] This invention also provides a method for preparing the single-crystal lithium-rich manganese-based cathode material as described above, comprising the following steps:

[0022] B1 is prepared by mixing F / Mg co-doped precursor material and lithium source at a molar ratio of 1:1.1 to 3, and ball milling to obtain intermediate mixture.

[0023] B2 places the intermediate mixture in an oxygen atmosphere, pre-sintersects it at 400-600℃, then sintersects it at 700-1000℃, washes it, and dries it to obtain a single-crystal lithium-rich manganese-based cathode material.

[0024] Preferably, in the pre-sintering process, the heating rate is controlled at 2–10 °C / min and the sintering time is 3–7 h; in the high-temperature sintering process, the heating rate is controlled at 1–5 °C / min and the sintering time is 10–20 h.

[0025] The technical mechanism and beneficial effects of this invention are as follows:

[0026] This invention reveals that while existing F / Mg co-doped lithium-rich manganese-based cathode materials exhibit better electrochemical performance, they suffer from inherent problems due to their spherical secondary particles. These problems include: the breakage and pulverization of agglomerated micron-sized secondary particles during cycling; the subsequent side reactions and dissolution of transition metal ions on the newly exposed internal surfaces upon contact with the electrolyte; and the resulting structural collapse, leading to continuous voltage and capacity decay. Furthermore, the spherical secondary particles can also cause safety issues such as gas expansion.

[0027] This invention employs techniques such as co-precipitation, hydrothermal treatment, and high-temperature sintering to prepare lithium-rich manganese-based cathode materials with single-crystal morphology, thereby addressing the problems existing in the aforementioned F / Mg co-doped polycrystalline lithium-rich manganese-based cathode materials.

[0028] Specifically, co-precipitation enables atomic-level mixing. MgF2 is uniformly dispersed within the particles via co-precipitation. MgF2 acts as both a dopant ion, stabilizing the material structure during battery cycling, and a flux, dispersing the precursor particles from within during high-temperature sintering. This provides an additional pathway for single-crystal growth, lowering the minimum temperature required to reach specific particle sizes and reducing cation mixing and agglomeration. Hydrothermal treatment of the precursor material aims to increase solid content and promote primary particle growth. Furthermore, the addition of surfactants during hydrothermal treatment regulates crystal growth, promoting single-crystal formation and improving the electrochemical performance of the single-crystal particles. The single-crystal lithium-rich manganese-based cathode material prepared using the method of this invention exhibits advantages such as uniform particle size distribution, high crystallinity, structural stability, and high safety. Attached Figure Description

[0029] Figure 1 Here is a SEM image of the precursor material in Example 2;

[0030] Figure 2 This is a SEM image of the multi-element doped single-crystal lithium-rich manganese-based cathode material in Example 1;

[0031] Figure 3 This is a SEM image of the multi-element doped single-crystal lithium-rich manganese-based cathode material in Example 2;

[0032] Figure 4 This is a SEM image of the multi-element doped single-crystal lithium-rich manganese-based cathode material in Example 3;

[0033] Figure 5 This is a SEM image of the multi-element doped single-crystal lithium-rich manganese-based cathode material in Example 4;

[0034] Figure 6 This is a SEM image of the multi-element doped single-crystal lithium-rich manganese-based cathode material in Example 5;

[0035] Figure 7 SEM image of the lithium-rich manganese-based cathode material in Comparative Example 1;

[0036] Figure 8 Here is a SEM image of the precursor material in Comparative Example 2;

[0037] Figure 9 SEM image of the lithium-rich manganese-based cathode material in Comparative Example 2;

[0038] Figure 10 The image shows a SEM image of the lithium-rich manganese-based cathode material in Comparative Example 3. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0040] This invention provides a multi-element doped single-crystal lithium-rich manganese-based cathode material and its preparation method, comprising the following steps:

[0041] (1) Preparation of F / Mg co-doped precursor materials:

[0042] Weigh out the required amounts of NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O, and MgSO4, dissolve them in deionized water, and prepare a NiSO4 solution. 2+ Co 2+ and Mn 2+ A mixed sulfate solution with a total ion concentration of 1–4 mol / L was prepared; then, Na₂CO₃, NH₄F, and Na₃C₆H₅O₇·2H₂O were weighed out and dissolved in deionized water to prepare an alkaline solution with a Na₂CO₃ concentration of 1–4 mol / L; wherein, by mass, the F in the alkaline solution… - The concentration of Mg in the mixed sulfate solution is 2+ The concentration is 200-245%, and the amount of Na2CO3 used is Ni. 2+ Co 2+ and Mn 2+ The total amount of NH4F used is 115-135% of the total amount of Mg. 2+ The amount of Na3C6H5O7·2H2O is 210-240% of that of Na2CO3, and the amount of Na3C6H5O7·2H2O is 2.5-3.5% of that of Na2CO3.

[0043] In this invention, the optimal dosage is: F in the alkaline solution - The concentration of Mg in the mixed sulfate solution is 2+ The concentration is 225%, and the amount of Na2CO3 used is Ni. 2+ Co 2+ and Mn 2+ The sum of the amounts used is 125%, and the amount of NH4F used is Mg. 2+ 225% of the total amount, and the amount of Na3C6H5O7·2H2O used is 3% of Na2CO3.

[0044] The mixed sulfate solution and alkaline solution prepared above were slowly added to the reaction vessel using a peristaltic pump, and the mixture was continuously stirred. The reaction was carried out for 6–18 hours, followed by filtration to collect the filter cake and the clear liquid. During the reaction, the temperature of the reaction vessel was controlled at 40–60℃, the stirring rate was 800–1300 rpm, and the pH value of the solution was controlled at 7.5–8.5 by adjusting the alkaline solution feed rate.

[0045] Take the above filter cake and a certain amount of clear liquid. The solid content of the mixture of filter cake and clear liquid is 20-50%. Transfer it to a high-pressure reactor, add surfactant, carry out hydrothermal reaction, and then filter, wash and dry to obtain F / Mg co-doped precursor material.

[0046] The surfactant includes one or more of polyvinylpyrrolidone, sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium hexadecyl sulfate, and sodium hexadecyl sulfonate. The total amount of surfactant used is 0.1 wt% to 10 wt% of the precursor. During the hydrothermal reaction, the temperature is controlled at 80 to 180°C and the reaction time is 6 to 48 hours.

[0047] (2) Preparation of multi-element doped single-crystal lithium-rich manganese-based cathode material:

[0048] Mix the precursor material prepared in step (I) with the lithium source at a molar ratio of 1:1.1 to 3, and ball mill to uniformly crush the precursor material to obtain an intermediate mixture.

[0049] The intermediate mixture is placed in a tube furnace and pre-sintered for 3-7 hours at a heating rate of 2-10℃ / min to 400-600℃ under an oxygen atmosphere. Then, the temperature is raised to 700-1000℃ at a heating rate of 1-5℃ / min and sintered for 10-20 hours. After washing and drying, the multi-element doped single-crystal lithium-rich manganese-based cathode material can be obtained.

[0050] The lithium source can be one or more of lithium carbonate, lithium nitrate, or lithium hydroxide. During the pre-sintering process, the precursor material decomposes with the lithium source, releasing H2O and CO2. During the sintering process, a high-temperature solid-state reaction occurs, prolonging the sintering time, which is beneficial to the formation of single crystal particles. Furthermore, MgF2, which has flux properties, is uniformly dispersed inside the precursor material, and the precursor particles can be dispersed under high temperature.

[0051] <Example>

[0052] Example 1

[0053] (1) Prepare the precursor material according to the following steps:

[0054] NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O, and MgSO4 were weighed out and dissolved in deionized water in a molar ratio of 0.13:0.13:0.54:0.01 to prepare NiSO4·6H2O. 2+ Co 2+ and Mn 2+ A mixed sulfate solution with a sum of ion concentrations of 2 mol / L;

[0055] Weigh out Na2CO3, NH4F and Na3C6H5O7·2H2O, dissolve them in deionized water, and prepare an alkaline solution with a Na2CO3 concentration of 2mol / L.

[0056] The mixed sulfate solution and alkaline solution were added to a reactor containing 300 ml of deionized water as the base solution using a peristaltic pump and reacted for 10 hours. During the entire reaction, the pH was controlled at around 8, the reaction temperature was maintained at 55℃, and the stirring speed was 1200 rpm. After the reaction was completed, the mixture was filtered and the filter cake and clear liquid were collected separately.

[0057] The filter cake and the clear liquid were mixed, and the solid content was controlled at 30%. The mixture was added to a high-pressure reactor, and then 2 wt% polyvinylpyrrolidone was added. The mixture was subjected to hydrothermal reaction at 180°C for 24 hours. After the reaction was completed, the mixture was filtered, washed, and dried to obtain the precursor material.

[0058] (2) Prepare multi-element doped single-crystal lithium-rich manganese-based cathode material according to the following steps:

[0059] With a molar ratio of 1:2, measure the precursor material and LiOH·H2O, mix them, place them in a ball mill jar, and ball mill at 400 rpm for 2 hours to ensure thorough mixing and obtain intermediate mixture.

[0060] The intermediate mixture was placed in a tube furnace and pre-sintered at 500°C for 5 hours in an oxygen atmosphere, followed by sintering at 850°C for 15 hours. After washing and drying, a multi-element doped single-crystal lithium-rich manganese-based cathode material was obtained.

[0061] Example 2

[0062] (1) Prepare the precursor material according to the following steps:

[0063] With a molar ratio of 0.13:0.13:0.54:0.02, NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O, and MgSO4 were weighed out and dissolved in deionized water to prepare NiSO4·6H2O·7 ... 2+ Co 2+ and Mn 2+ A mixed sulfate solution with a sum of ion concentrations of 2 mol / L;

[0064] Weigh out Na2CO3, NH4F and Na3C6H5O7·2H2O, dissolve them in deionized water, and prepare an alkaline solution with a Na2CO3 concentration of 2mol / L.

[0065] The mixed sulfate solution and alkaline solution were added to a reactor containing 300 ml of deionized water as the base solution using a peristaltic pump and reacted for 10 hours. During the entire reaction, the pH was controlled at around 8, the reaction temperature was maintained at 55℃, and the stirring speed was 1200 rpm. After the reaction was completed, the mixture was filtered and the filter cake and clear liquid were collected separately.

[0066] The filter cake and the clear liquid were mixed, and the solid content was controlled at 30%. The mixture was added to a high-pressure reactor, and then 2 wt% polyvinylpyrrolidone was added. The mixture was subjected to hydrothermal reaction at 180°C for 24 hours. After the reaction was completed, the mixture was filtered, washed, and dried to obtain the precursor material.

[0067] (2) Prepare multi-element doped single-crystal lithium-rich manganese-based cathode material according to the following steps:

[0068] With a molar ratio of 1:2, measure the precursor material and LiOH·H2O, mix them, place them in a ball mill jar, and ball mill at 400 rpm for 2 hours to ensure thorough mixing and obtain intermediate mixture.

[0069] The intermediate mixture was placed in a tube furnace and pre-sintered at 500°C for 5 hours in an oxygen atmosphere, followed by sintering at 850°C for 15 hours. After washing and drying, a multi-element doped single-crystal lithium-rich manganese-based cathode material was obtained.

[0070] Example 3

[0071] (1) Prepare the precursor material according to the following steps:

[0072] With a molar ratio of 0.13:0.13:0.54:0.03, NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O, and MgSO4 were weighed out and dissolved in deionized water to prepare NiSO4·6H2O·7 ... 2+ Co 2+ and Mn 2+ A mixed sulfate solution with a sum of ion concentrations of 2 mol / L;

[0073] Weigh out Na2CO3, NH4F and Na3C6H5O7·2H2O, dissolve them in deionized water, and prepare an alkaline solution with a Na2CO3 concentration of 2mol / L.

[0074] The mixed sulfate solution and alkaline solution were added to a reactor containing 300 ml of deionized water as the base solution using a peristaltic pump and reacted for 10 hours. During the entire reaction, the pH was controlled at around 8, the reaction temperature was maintained at 55℃, and the stirring speed was 1200 rpm. After the reaction was completed, the mixture was filtered and the filter cake and clear liquid were collected separately.

[0075] The filter cake and the clear liquid were mixed, and the solid content was controlled at 30%. The mixture was added to a high-pressure reactor, and then 2 wt% polyvinylpyrrolidone was added. The mixture was subjected to hydrothermal reaction at 180°C for 24 hours. After the reaction was completed, the mixture was filtered, washed, and dried to obtain the precursor material.

[0076] (2) Prepare multi-element doped single-crystal lithium-rich manganese-based cathode material according to the following steps:

[0077] With a molar ratio of 1:2, measure the precursor material and LiOH·H2O, mix them, place them in a ball mill jar, and ball mill at 400 rpm for 2 hours to ensure thorough mixing and obtain intermediate mixture.

[0078] The intermediate mixture was placed in a tube furnace and pre-sintered at 500°C for 5 hours in an oxygen atmosphere, followed by sintering at 850°C for 15 hours. After washing and drying, a multi-element doped single-crystal lithium-rich manganese-based cathode material was obtained.

[0079] Example 4

[0080] (1) Prepare the precursor material according to the following steps:

[0081] With a molar ratio of 0.13:0.13:0.54:0.02, NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O, and MgSO4 were weighed out and dissolved in deionized water to prepare NiSO4·6H2O·7 ... 2+ Co 2+ and Mn 2+ A mixed sulfate solution with a sum of ion concentrations of 2 mol / L;

[0082] Weigh out Na2CO3, NH4F and Na3C6H5O7·2H2O, dissolve them in deionized water, and prepare an alkaline solution with a Na2CO3 concentration of 2mol / L.

[0083] The mixed sulfate solution and alkaline solution were added to a reactor containing 300 ml of deionized water as the base solution using a peristaltic pump and reacted for 10 hours. During the entire reaction, the pH was controlled at around 8, the reaction temperature was maintained at 55℃, and the stirring speed was 1200 rpm. After the reaction was completed, the mixture was filtered and the filter cake and clear liquid were collected separately.

[0084] The filter cake and the clear liquid were mixed, and the solid content was controlled at 30%. The mixture was added to a high-pressure reactor, and then 2 wt% polyvinylpyrrolidone was added. The mixture was subjected to hydrothermal reaction at 180°C for 24 hours. After the reaction was completed, the mixture was filtered, washed, and dried to obtain the precursor material.

[0085] (2) Prepare multi-element doped single-crystal lithium-rich manganese-based cathode material according to the following steps:

[0086] With a molar ratio of 1:2, measure the precursor material and LiOH·H2O, mix them, place them in a ball mill jar, and ball mill at 400 rpm for 2 hours to ensure thorough mixing and obtain intermediate mixture.

[0087] The intermediate mixture was placed in a tube furnace and pre-sintered at 500°C for 5 hours in an oxygen atmosphere, followed by sintering at 880°C for 15 hours. After washing and drying, a multi-element doped single-crystal lithium-rich manganese-based cathode material was obtained.

[0088] Example 5

[0089] (1) Prepare the precursor material according to the following steps:

[0090] With a molar ratio of 0.13:0.13:0.54:0.02, NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O, and MgSO4 were weighed out and dissolved in deionized water to prepare NiSO4·6H2O·7 ... 2+ Co 2+ and Mn 2+ A mixed sulfate solution with a sum of ion concentrations of 2 mol / L;

[0091] Weigh out Na2CO3, NH4F and Na3C6H5O7·2H2O, dissolve them in deionized water, and prepare an alkaline solution with a Na2CO3 concentration of 2mol / L.

[0092] The mixed sulfate solution and alkaline solution were added to a reactor containing 300 ml of deionized water as the base solution using a peristaltic pump and reacted for 10 hours. During the entire reaction, the pH was controlled at around 8, the reaction temperature was maintained at 55℃, and the stirring speed was 1200 rpm. After the reaction was completed, the mixture was filtered and the filter cake and clear liquid were collected separately.

[0093] The filter cake and the clear liquid were mixed, and the solid content was controlled at 30%. The mixture was added to a high-pressure reactor, and then 2 wt% polyvinylpyrrolidone was added. The mixture was subjected to hydrothermal reaction at 180°C for 24 hours. After the reaction was completed, the mixture was filtered, washed, and dried to obtain the precursor material.

[0094] (2) Prepare multi-element doped single-crystal lithium-rich manganese-based cathode material according to the following steps:

[0095] With a molar ratio of 1:2, measure the precursor material and LiOH·H2O, mix them, place them in a ball mill jar, and ball mill at 400 rpm for 2 hours to ensure thorough mixing and obtain intermediate mixture.

[0096] The intermediate mixture was placed in a tube furnace and pre-sintered at 500°C for 5 hours in an oxygen atmosphere, followed by sintering at 820°C for 15 hours. After washing and drying, a multi-element doped single-crystal lithium-rich manganese-based cathode material was obtained.

[0097] <Comparative Example>

[0098] Comparative Example 1

[0099] (1) Prepare the precursor material according to the following steps:

[0100] With a molar ratio of 0.13:0.13:0.54:0.02, NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O, and MgSO4 were weighed out and dissolved in deionized water to prepare NiSO4·6H2O·7 ... 2+ Co 2+ and Mn 2+ A mixed sulfate solution with a sum of ion concentrations of 2 mol / L;

[0101] Weigh out Na2CO3, NH4F and Na3C6H5O7·2H2O, dissolve them in deionized water, and prepare an alkaline solution with a Na2CO3 concentration of 2mol / L.

[0102] A peristaltic pump was used to add the mixed sulfate solution and alkaline solution to a reaction vessel containing 300 ml of deionized water as the base solution. 2 wt% polyvinylpyrrolidone was added, and the reaction was carried out for 10 h. During the entire reaction, the pH was controlled at around 8, the reaction temperature was maintained at 55℃, and the stirring speed was 1200 rpm. After the reaction was completed, the precursor material was obtained by filtration, washing, and drying.

[0103] (2) Prepare multi-element doped single-crystal lithium-rich manganese-based cathode material according to the following steps:

[0104] With a molar ratio of 1:2, measure the precursor material and LiOH·H2O, mix them, place them in a ball mill jar, and ball mill at 400 rpm for 2 hours to ensure thorough mixing and obtain intermediate mixture.

[0105] The intermediate mixture was placed in a tube furnace and pre-sintered at 500°C for 5 hours in an oxygen atmosphere, followed by sintering at 850°C for 15 hours. After washing and drying, a multi-element doped single-crystal lithium-rich manganese-based cathode material was obtained.

[0106] Comparative Example 2

[0107] (1) Prepare the precursor material according to the following steps:

[0108] With a molar ratio of 0.13:0.13:0.54:0.02, NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O, and MgSO4 were weighed out and dissolved in deionized water to prepare NiSO4·6H2O·7 ... 2+ Co 2+ and Mn 2+ A mixed sulfate solution with a sum of ion concentrations of 2 mol / L;

[0109] Weigh out Na2CO3, NH4F and Na3C6H5O7·2H2O, dissolve them in deionized water, and prepare an alkaline solution with a Na2CO3 concentration of 2mol / L.

[0110] A peristaltic pump was used to add the mixed sulfate solution and alkaline solution to a reactor containing 300 ml of deionized water as the base solution. The reaction was carried out for 10 hours and then aged for 20 hours. During the reaction, the pH was controlled at around 8, the reaction temperature was maintained at 55℃, and the stirring speed was 1200 rpm. After the reaction was completed, the precursor material was obtained by filtration, washing, and drying.

[0111] (2) Prepare multi-element doped single-crystal lithium-rich manganese-based cathode material according to the following steps:

[0112] With a molar ratio of 1:2, measure the precursor material and LiOH·H2O, mix them, place them in a ball mill jar, and ball mill at 400 rpm for 2 hours to ensure thorough mixing and obtain intermediate mixture.

[0113] The intermediate mixture was placed in a tube furnace and pre-sintered at 500°C for 5 hours in an oxygen atmosphere, followed by sintering at 850°C for 15 hours. After washing and drying, lithium-rich manganese-based cathode material was obtained.

[0114] Comparative Example 3

[0115] (1) Prepare the precursor material according to the following steps:

[0116] With a molar ratio of 0.13:0.13:0.54:0.02, NiSO4·6H2O, CoSO4·7H2O, MnSO4·H2O, and MgSO4 were weighed out and dissolved in deionized water to prepare NiSO4·6H2O·7 ... 2+ Co 2+ and Mn 2+ A mixed sulfate solution with a sum of ion concentrations of 2 mol / L;

[0117] Weigh out Na2CO3, NH4F and Na3C6H5O7·2H2O, dissolve them in deionized water, and prepare an alkaline solution with a Na2CO3 concentration of 2mol / L.

[0118] A peristaltic pump was used to add the mixed sulfate solution and alkaline solution to a reactor containing 300 ml of deionized water as the base solution. The reaction was carried out for 10 hours and then aged for 20 hours. During the reaction, the pH was controlled at around 8, the reaction temperature was maintained at 55℃, and the stirring speed was 1200 rpm. After the reaction was completed, the precursor material was obtained by filtration, washing, and drying.

[0119] (2) Prepare multi-element doped single-crystal lithium-rich manganese-based cathode material according to the following steps:

[0120] With a molar ratio of 1:1.56, measure the precursor material and LiOH·H2O, mix them, place them in a ball mill jar, and ball mill at 400 rpm for 1 hour to ensure thorough mixing and obtain the intermediate mixture.

[0121] The intermediate mixture was placed in a tube furnace and pre-sintered at 500°C for 5 hours in an oxygen atmosphere, followed by sintering at 850°C for 12 hours. After washing and drying, lithium-rich manganese-based cathode material was obtained.

[0122] <Experimental Example>

[0123] Samples: Examples 1-5, Comparative Examples 1-3

[0124] (I) Material Structural Properties

[0125] The structural features of the precursor material and lithium-rich manganese-based cathode material in the sample were observed using scanning electron microscopy, such as... Figure 1 This is a scanning electron microscope (SEM) image of the precursor material in Example 2. Figure 2-6 The images shown are SEM images of the multi-element doped single-crystal lithium-rich manganese-based cathode materials from Examples 1-5. Figure 7 The image shows a SEM image of the lithium-rich manganese-based cathode material in Comparative Example 1. Figure 8-9 The images show SEM images of the precursor material and the lithium-rich manganese-based cathode material of Comparative Example 2, respectively. Figure 10 The SEM images of the lithium-rich manganese-based cathode material in Comparative Example 3 show the following conclusions:

[0126] (1) Comparison Figure 1 and Figure 8 It can be observed that, compared to the precursor material in Comparative Example 2 that has not undergone hydrothermal treatment, the precursor material in Example 2 exhibits a larger primary particle volume on its surface and contains some hexagonal plate-like precursors. This structure is beneficial for the formation of single-crystal particles and the improvement of electrochemical performance during subsequent high-temperature sintering. Figure 3 and Figure 9It was found that the single crystal particles obtained without hydrothermal treatment had an uneven particle size distribution and a large number of small particles. This is because the smaller primary particles of the precursor are not conducive to the growth of single crystal particles. After hydrothermal treatment, the single crystal particles prepared were larger and more uniform in size, which shows that hydrothermal treatment has a decisive influence on the improvement of the performance of the precursor material.

[0127] (2) Figures 2 to 4 These are multi-element doped single-crystal lithium-rich manganese-based cathode materials obtained by doping with different MgF2 contents. The single-crystal material obtained in Example 1 has slight agglomeration. With the increase of MgF2 content, the fluxing effect is enhanced, the agglomeration phenomenon is significantly improved, the size of the obtained single-crystal particles is slightly increased, and the uniformity of particle size is improved. In addition, MgF2, as the most important doping element, has a significant impact on the electrochemical performance of the material. As shown in Table 1, the optimal doping concentration is that of Example 2. Figure 3 , Figure 5 and Figure 6 These are multi-element doped single-crystal lithium-rich manganese-based cathode materials prepared using different sintering temperatures. Observation shows that within a certain temperature range, increasing the sintering temperature is beneficial for forming single-crystal particles with larger particle sizes, and the best sintering effect is observed at 850℃.

[0128] (3) Comparison Figure 7 and Figure 9 It was found that adding surfactants during the preparation process helps in the formation of single-crystal morphology, indicating that the addition of surfactants during the preparation process has a significant impact on the growth of single-crystal particles; compared with Figure 3 and Figure 7 It was found that the single crystal particles obtained after the hydrothermal process were larger and more uniform in size, indicating that the hydrothermal process plays a crucial role in the formation and growth of single crystal morphology.

[0129] (II) Electrochemical Performance

[0130] The positive electrode slurry for the battery was prepared by taking samples, conductive carbon black, and PVDF at a mass ratio of 8:1:1, and then assembling the battery with lithium metal as the negative electrode material. Electrochemical performance tests were conducted, and the results are shown in Table 1 below.

[0131] Table 1 Electrochemical performance of batteries assembled from different samples

[0132]

[0133] As can be seen from Table 1 above, Comparative Examples 1 and 2 are lithium-rich manganese-based cathode materials obtained without hydrothermal treatment, while Comparative Example 3 is a polycrystalline lithium-rich manganese-based cathode material. Compared with Comparative Examples 1 and 2, the materials in Examples 1-5, after hydrothermal treatment, show obvious comprehensive advantages in electrochemical performance such as first-cycle discharge specific capacity and first-cycle coulombic efficiency, especially in capacity retention. Compared with Comparative Example 3, the single-crystal materials in Examples 1-5 have a slightly decreased capacity, but a significantly increased capacity retention.

[0134] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing an F / Mg co-doped precursor material, characterized in that, The method comprises the following steps: A1 contains Mg 2+ sulfate solution, F - containing alkali solution is reacted, and solid residue and clear liquid are separated. A2, taking the solid residue and the clear liquid, the solid content of the mixture of the solid residue and the clear liquid being 20-50%, adding a surfactant, and performing a hydrothermal reaction, wherein the temperature is controlled to be 80-180 DEG C and the reaction time is 6-48 h during the hydrothermal reaction, and the F / Mg co-doped precursor material is obtained by separation; The surfactant comprises one or more of polyvinylpyrrolidone, sodium dodecyl sulfate, sodium dodecyl sulfonate, sodium hexadecyl sulfate, and sodium hexadecyl sulfonate, and the amount of the surfactant is 0.1-10 wt% of the hydrothermal reaction raw material.

2. The method of claim 1, wherein the F / Mg co-doped precursor material is prepared by a method comprising: The Mg-containing 2+ sulfate solution includes NiSO4, CoSO4, MnSO4, and MgSO4, and the sum of the ion concentrations of Ni 2+ , Co 2+ , and Mn 2+ in the sulfate solution is 1 to 4 mol / L.

3. The method of claim 2, wherein the F / Mg co-doped precursor material is prepared by a method comprising: The F - containing base solution includes Na2CO3, NH4F, and Na3C6H5O7·2H2O, and in the base solution, the F - concentration is 210~240% of the Mn 2+ concentration in the sulfate solution.

4. The F / Mg co-doped precursor material prepared by the preparation method in any one of claims 1-3.

5. A single-crystalline lithium-rich manganese-based cathode material, characterized in that, The raw material comprises the F / Mg co-doped precursor material prepared by the preparation method in any one of claims 1-3 or the F / Mg co-doped precursor material in claim 4.

6. The method for preparing the single-crystal lithium-rich manganese-based cathode material as described in claim 5, characterized in that, The method comprises the following steps: B1, taking the F / Mg co-doped precursor material and a lithium source in a molar ratio of 1:1.1-3, mixing, and ball milling to obtain intermediate mixture; B2, placing the intermediate mixture in an oxygen atmosphere, pre-sintering at 400-600 DEG C, high-temperature sintering at 700-1000 DEG C, washing, drying, and obtaining the single-crystal lithium-rich manganese-based positive electrode material.

7. The method for preparing single-crystal lithium-rich manganese-based cathode material according to claim 6, characterized in that, In the pre-sintering, the heating rate is controlled to be 2-10 DEG C / min and the sintering time is 3-7 h; in the high-temperature sintering, the heating rate is controlled to be 1-5 DEG C / min and the sintering time is 10-20 h.

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