A layered lithium-rich manganese-based high-entropy cathode material, its preparation method, and a battery

Abstract

The present invention discloses a layered lithium-rich manganese-based high-entropy cathode material, a preparation method thereof, and a battery. The chemical formula of the cathode material is Li a [Li x Mn y A 1‑x‑y O2, the Li layer and the transition metal [Li x Mn y A 1‑x‑y layers are alternately arranged, 0

Description

Technical Field

[0001] The present invention belongs to the fields of lithium-ion battery materials and electrochemistry, and relates to a layered lithium-rich manganese-based high-entropy cathode material, a preparation method thereof, and a battery. Background Art

[0002] As an advanced energy storage device, lithium-ion batteries can realize the convenient use of new energy in terms of time and space, and have received extensive attention since the commercialization of lithium cobalt oxide batteries in the 1990s. With the rapid development of new energy vehicles and large-scale energy storage power grids, conventional lithium-ion battery materials can no longer meet the needs of people for battery systems with higher specific energy, higher power density, and higher cost performance. For lithium-ion batteries, the cathode material has long been proven to be the key bottleneck for improving the comprehensive performance of the lithium-ion battery system. Therefore, the research on the cathode material has never stopped.

[0003] At present, several commonly used cathode materials on the market include layered LiCoO2, ternary materials, high-nickel cathode materials, polyanion-type LiFePO4, and spinel-type LiMn2O4, etc., but there are problems such as low specific capacity (120-200 mAh / g) and / or high cost, which are not conducive to the lightweight, long endurance, and wider promotion of electric vehicles.

[0004] Seeking cathode materials with higher energy density and lower cost has been the goal of academia and industry. In recent years, lithium-rich manganese-based cathode materials have received extensive research due to their high specific capacity (above 250 mAh / g, even exceeding 300 mAh / g) and relatively low cost (using more Mn). However, they still have many disadvantages, such as oxygen evolution at high voltages and the resulting low initial Coulombic efficiency (65%-80%); poor cycle stability; continuous voltage decay and many other problems. Currently, they are struggling in the process of commercialization. To improve the above problems, efforts are mainly made from several aspects such as coating, doping, and surface treatment, and certain effects have been achieved. In the Chinese patent authorized text CN113451582B, the inventors provided a tungsten and sulfur co-doped modified lithium-rich manganese-based cathode material and its preparation method. Through tungsten and sulfur co-doping modification, the initial Coulombic efficiency and cycle stability of the lithium-rich manganese-based cathode material were improved; in the Chinese patent application published specification CN114864895A, the inventors disclosed a surface-reconstructed lithium-rich manganese-based cathode material and its preparation method and application. Utilizing the characteristic that zirconium alkoxide will hydrolyze in deionized water, a ZrO2 coating layer is formed on the surface of the bulk material, and at the same time, a Li2ZrO3 layer is formed using the residual alkali on the surface of the bulk material. The Zr in the Li2ZrO3 coating layer will migrate inward under thermodynamic action, thereby forming a near-surface doping of Zr. By constructing a "three-in-one" surface through wet chemical method and high-temperature solid-phase method, the cycle stability and rate performance of the cathode material are improved. However, there are still some problems: such as the processing technology is troublesome, it is not compatible with the current production line, or the improvement effect is limited. Summary of the Invention

[0005] To solve the above technical problems, the present invention provides a layered lithium-rich manganese-based high-entropy cathode material, its preparation method, and a corresponding lithium-ion battery. By constructing a lithium-rich manganese-based cathode material with a higher in-layer configurational entropy, a large amount of O2 release during the first charge process is avoided, as well as the continuous voltage decay caused by the migration of transition metal ions during the cycle, avoiding a significant attenuation of the energy density and increasing the difficulty of battery system management, which will strongly promote the practical use of lithium-rich manganese-based cathode materials.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] A layered lithium-rich manganese-based high-entropy cathode material, whose chemical formula is Li a [Li x Mn y A 1-x-yO2, where 0 < a ≤ 1, 0.1 ≤ x ≤ 0.25, 0.45 ≤ y ≤ 0.55; A is at least 4 of Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Sn, Sb, Te, Ta, W, Ce, and their contents are represented by a1, a2, a3, ai…an respectively (n represents a natural number ≥ 4, and i represents any number from 1 to n), where 0 < ai ≤ 0.15, and satisfy -

[0008] Furthermore, the structure of the above-mentioned layered lithium-rich manganese-based high-entropy cathode material belongs to space group or C2 / m space group or is composed of both, where: the Li layer and the transition metal [Li x Mn y A 1-x-y layers are arranged alternately.

[0009] In the above-mentioned layered lithium-rich manganese-based high-entropy cathode material, in the transition metal [Li x Mn y A 1-x-y layer, the content of each element preferably satisfies

[0010] In the above-mentioned layered lithium-rich manganese-based high-entropy cathode material, preferably, 0.85 < a ≤ 1, 0.15 ≤ x ≤ 0.20, 0.48 ≤ y ≤ 0.54; 0.025 < ai ≤ 0.05.

[0011] In the above-mentioned layered lithium-rich manganese-based high-entropy cathode material, preferably, A can be selected as a combination of Ni, Co, Fe, Cu; a combination of Ni, Co, Fe, Cu, Mg; a combination of Ni, Co, Fe, Cu, Mg, Ti; a combination of Ni, Co, Fe, Cu, Mg, Ti, Al; a combination of Ni, Co, Fe, Cu, Ti, Al; a combination of Ni, Co, Fe, Cu, Zn, Mg, Al, Zr; a combination of Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru; a combination of Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Sn, Sb, Te, Ta, W, Ce, and so on. The obtained layered lithium-rich manganese-based high-entropy cathode material is, for example:

[0012] Li 1.0 Li 0.15 Mn 0.45 Ni 0.10 Co 0.10 Fe 0.10 Cu 0.10 O2;

[0013] Li1.0 Li 0.15 Mn 0.45 Ni 0.08 Co 0.08 Fe 0.08 Cu 0.08 Mg 0.08 O2;

[0014] Li 1.0 Li 0.15 Mn 0.45 Ni 0.08 Co 0.08 Fe 0.08 Cu 0.08 Ti 0.04 Al 0.04 O2;

[0015] Li 1.0 Li 0.15 Mn 0.45 Ni 0.1 Co 0.05 Fe 0.05 Cu 0.05 Mg 0.05 Ti 0.05 Al 0.05 O2;

[0016] Li 1.0 Li 0.15 Mn 0.5 Ni 0.1 Co 0.05 Fe 0.05 Cu 0.05 Mg 0.05 Al 0.05 O2;

[0017] Li 1.0 Li 0.15 Mn 0.5 Ni 0.05 Co 0.05 Fe 0.05 Cu 0.05 Zn 0.05 Mg 0.05 Al 0.025 Zr 0.025 O2。

[0018] Furthermore, the present invention also provides a preparation method for the layered lithium-rich manganese-based high-entropy cathode material, specifically including the following three methods:

[0019] (1) Solid-state sintering method, including the following steps:

[0020] 1) Weigh the chemical formula Li a [Li x Mny A 1-x-y Compounds of lithium, compounds of Mn, and compounds of A with the stoichiometric ratios shown in ]O2 are ground together and mixed evenly;

[0021] 2) The above-ground mixture is pre-calcined at 150 - 550 °C for 4 - 10 h, then taken out and ground again to be mixed evenly, and then calcined at 750 - 950 °C for 8 - 20 h to obtain the target layered lithium-rich manganese-based high-entropy cathode material.

[0022] (2) Sol-gel method, including the following steps:

[0023] 1) Weigh soluble compounds of lithium, soluble compounds of Mn, and soluble compounds of A with the stoichiometric ratios shown in the chemical formula Li a [Li x Mn y A 1-x-y O2. At the same time, add citric acid with a molar amount 2 - 5 times that of the metal elements and ethylene glycol with a molar amount 1 - 3 times that of the metal elements. All are dissolved in deionized water to prepare a solution, and then rotary evaporated on a rotary evaporator to form a sol, where the temperature is 70 - 95 °C and the rotation speed is 30 - 80 r / min;

[0024] 2) Place the gel in an oven and dry it at 120 - 150 °C for 5 - 12 h to evaporate the sol into a gel;

[0025] 3) Grind the gel obtained in step 2), pre-calcine the evenly ground mixture at 150 - 550 °C for 4 - 10 h, and then immediately calcine it at 750 - 950 °C for 8 - 20 h to obtain the target layered lithium-rich manganese-based high-entropy cathode material.

[0026] (3) Co-precipitation-high temperature solid-state method, including the following steps:

[0027] 1) Preparation of the precursor:

[0028] i. Prepare a mixed solution of Mn and A: Weigh soluble compounds of Mn and A according to the ratio of Mn and A in the final cathode material and dissolve them in deionized water to prepare a mixed solution with a concentration of 0.5 - 3.0 mol / L;

[0029] ii. Dissolve NaOH and / or KOH or Na2CO3 and / or K2CO3 in deionized water to prepare a mixed alkali solution with a concentration of 0.5 - 3.0 mol / L; Add ammonia water as a complexing agent, and the concentration of ammonium ions is 0.1 - 2 times that of the alkali concentration;

[0030] iii. Slowly and uniformly add the mixed solution obtained in step i and the mixed alkali solution obtained in step ii into a container filled with deionized water at a rate controlled at 0.5 - 2.5 mL / min. Throughout the process, for carbonate precipitation, the pH value is maintained between 7 and 9; for hydroxide precipitation, the pH value is maintained between 10 and 12, and the temperature is between 50 and 80 °C; the stirring speed is 300 - 1000 r / min;

[0031] iv. After the dropping is completed, let it stand for aging for 1 - 16 h, then filter, wash, and dry the precipitate to obtain the precursor material;

[0032] 2) Weigh lithium compounds in the stoichiometric ratio shown in the chemical formula Lia[Li x Mn y A 1-x-y O2 and the precursor material prepared in step 1), grind them together, and mix them evenly;

[0033] 3) Pre-calcine the above evenly ground mixture at 150 - 550 °C for 4 - 10 h, and then calcine it at 750 - 950 °C for 8 - 20 h to obtain the target layered lithium-rich manganese-based high-entropy cathode material.

[0034] In the preparation method of the layered lithium-rich manganese-based high-entropy cathode material, in step 1) of the method (1), the Li compound is selected from one or more of lithium carbonate, oxalate, acetate, sulfate, nitrate, halide, oxide, and hydroxide; the Mn compound is selected from one or more of manganese carbonate, oxalate, acetate, sulfate, nitrate, halide, oxide, and hydroxide; the A compound is selected from one or more of A carbonate, oxalate, acetate, sulfate, nitrate, halide, oxide, and hydroxide, where A is at least 4 of Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Sn, Sb, Te, Ta, W, and Ce.

[0035] In the preparation method of the layered lithium-rich manganese-based high-entropy cathode material, in step 1) of the method (2), the soluble lithium compound is selected from one or more of lithium carbonate, oxalate, acetate, sulfate, nitrate, and halide; the soluble Mn compound is selected from one or more of manganese acetate, nitrate, sulfate, and halide; the soluble A compound is selected from one or more of A acetate, nitrate, sulfate, and halide, where A is at least 4 of Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Sn, Sb, Te, Ta, W, and Ce.

[0036] In the preparation method of the layered lithium-rich manganese-based high-entropy cathode material, in item i) of step 1) of the method (3), the soluble compound of Mn is selected from one or more of acetate, nitrate, sulfate, and halide of Mn; the soluble compound of A is selected from one or more of acetate, nitrate, sulfate, and halide of A, where A is at least 4 of Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Sn, Sb, Te, Ta, W, and Ce.

[0037] In the preparation method of the layered lithium-rich manganese-based high-entropy cathode material, in step 2) of the method (3), the compound of Li is selected from one or more of carbonate, oxalate, acetate, sulfate, nitrate, halide, oxide, and hydroxide of lithium.

[0038] Furthermore, the present invention also provides a positive electrode sheet, which contains the layered lithium-rich manganese-based high-entropy cathode material or the cathode material prepared by the preparation method of the layered lithium-rich manganese-based high-entropy cathode material.

[0039] Furthermore, the present invention also provides a battery, which includes a positive electrode sheet, a negative electrode sheet, a separator, and an electrolyte, wherein the positive electrode sheet contains the layered lithium-rich manganese-based high-entropy cathode material or the cathode material prepared by the preparation method of the layered lithium-rich manganese-based high-entropy cathode material.

[0040] Compared with the prior art, the beneficial effects of the present invention include:

[0041] By constructing a lithium-rich manganese-based cathode material with a higher configurational entropy within the layer, the integrity of the crystal structure of the material is ensured, avoiding the large amount of release of O2 during the first charge process and the continuous voltage decay caused by the migration of transition metal ions during the cycling process, avoiding a significant attenuation of the energy density and increasing the difficulty of battery system management; in addition, this method is simple and matches the current process, which will strongly promote the practical use of the lithium-rich manganese-based cathode material. Description of the Drawings

[0042] Figure 1 . XRD of the layered lithium-rich manganese-based high-entropy cathode material in Example 3.

[0043] Figure 2 . Cyclic stability diagram of the layered lithium-rich manganese-based high-entropy cathode material in Example 3.

[0044] Figure 3 . XRD of the conventional lithium-rich manganese-based cathode material in Comparative Example 1.

[0045] Figure 4Cyclic stability diagram of the conventional lithium-rich manganese-based cathode material in Comparative Example 1. Detailed implementation mode

[0046] Example 1. Synthesis of layered lithium-rich manganese-based high-entropy cathode material Li 1.0 Li 0.15 Mn 0.45 Ni 0.1 Co 0.05 Fe 0.05 Cu 0.05 Mg 0.05 Ti 0.05 Al 0.05 O2

[0047] It is estimated that the synthesized cathode material is 0.03 mol. Weigh Li2CO3, MnO2, NiO, CoO, Fe2O3, CuO, MgO, TiO2 and Al2O3 according to the molar ratio shown in the chemical formula. Mix and grind the above compounds evenly. After grinding evenly, put them into a porcelain boat and place it in a tube furnace. First, pre-burn at 450 °C for 4 h, then take it out and grind and mix evenly again. Then place it in the tube furnace again and calcine at 850 °C for 10 h. After taking it out, grind it evenly to obtain the layered lithium-rich manganese-based high-entropy cathode material Li 1.0 Li 0.15 Mn 0.45 Ni 0.1 Co 0.05 Fe 0.05 Cu 0.05 Mg 0.05 Ti 0.05 Al 0.05 O2.

[0048] Mix the above-prepared layered lithium-rich manganese-based high-entropy cathode material Li 1.0 Li 0.15 Mn 0.45 Ni 0.1 Co 0.05 Fe 0.05 Cu 0.05 Mg 0.05 Ti 0.05 Al 0.05 O2 with carbon black and PVDF in a mass ratio of 8:1:1, grind evenly with N-methylpyrrolidone as the solvent, then coat it on aluminum foil, and place it in a blast drying oven at 100 °C for 12 h. After taking it out, roll it several times on a rolling press and cut it into electrode discs. Use this as the positive electrode sheet, use a lithium sheet as the negative electrode sheet, the glass microfiber filter paper GF / D produced by Whatman company, and the electrolyte is the high-voltage electrolyte for lithium-ion batteries produced by Beijing Chemical Reagent Research Institute. Assemble a button battery in a glove box and test it on a Neware battery test system at a temperature of 25 °C at room temperature.

[0049] The material synthesized under this condition, when tested at a voltage range of 2.0 - 4.8 V and a current density of 25 mA / g, has an initial discharge capacity of 230 mAh / g. The reversible discharge capacity at the 100th cycle is higher than 185 mAh / g, the capacity retention rate is greater than 80%, and the voltage decay is less than 200 mV.

[0050] Example 2. Synthesis of layered lithium-rich manganese-based high-entropy cathode material Li 1.0 Li 0.15 Mn 0.5 Ni 0.1 Co 0.05 Fe 0.05 Cu 0.05 Mg 0.05 Al 0.05 O2

[0051] It is expected that 0.03 mol of the synthesized cathode material is obtained. Weigh the acetates of Li, Mn, Ni, Co, Fe, Cu, Mg, and Al according to the molar ratio shown in the chemical formula. At the same time, add citric acid with a molar amount 4 times that of the metal elements and ethylene glycol with a molar amount 2 times that of the metal elements. Dissolve them in deionized water and perform rotary evaporation on a rotary evaporator to form a sol; the temperature is 80 °C and the rotation speed is 55 r / min. Place the obtained gel in an oven and dry it at 150 °C for 10 h to evaporate the sol into a gel; crush the obtained gel, pre-calcine the uniformly ground mixture at 400 °C for 5 h, and then calcine it at 900 °C for 15 h to obtain the target layered lithium-rich manganese-based high-entropy cathode material.

[0052] Mix the above-prepared layered lithium-rich manganese-based high-entropy cathode material Li 1.0 Li 0.15 Mn 0.5 Ni 0.1 Co 0.05 Fe 0.05 Cu 0.05 Mg 0.05 Al 0.05 O2 with carbon black and PVDF in a mass ratio of 8:1:1, grind them evenly with N-methylpyrrolidone as the solvent, then coat them on aluminum foil, and place them in a forced-air drying oven at 100 °C for 12 h. After taking them out, roll them several times on a rolling press and cut them into electrode discs. Use this as the positive electrode sheet, use a lithium sheet as the negative electrode sheet, a glass microfiber filter paper GF / D produced by Whatman company, and the electrolyte is a high-voltage lithium-ion battery electrolyte produced by Beijing Chemical Reagent Research Institute. Assemble a button battery in a glove box and test it on a Neware battery test system at a temperature of 25 °C (room temperature).

[0053] The material synthesized under this condition has an initial discharge capacity of 280 mAh / g when tested at a current density of 25 mA / g within a voltage range of 2.0 - 4.8 V. The reversible discharge capacity at the 100th cycle is higher than 255 mAh / g, the capacity retention rate is greater than 90%, and the voltage decay is less than 150 mV.

[0054] Example 3. Synthesis of layered lithium-rich manganese-based high-entropy cathode material Li 1.0 Li 0.15 Mn 0.5 Ni 0.05 Co 0.05 Fe 0.05 Cu 0.05 Zn 0.05 Mg 0.05 Al 0.05 O2

[0055] 1) Preparation of precursor:

[0056] i. Prepare a mixed salt solution: Weigh the sulfates of Mn, Ni, Co, Fe, Cu, Zn, Mg, and Al according to the above molar ratio, dissolve them in deionized water, and prepare a mixed salt solution with a concentration of 2 mol / L.

[0057] ii. Dissolve Na2CO3 in deionized water to prepare an alkali solution with a concentration of 2 mol / L; add ammonia water as a complexing agent with an ammonium ion concentration of 0.2 mol / L;

[0058] iii. Slowly and uniformly add the above mixed salt solution and mixed alkali solution into a container filled with deionized water at a speed of 1.5 ml / min. During the whole process, the pH value is maintained at about 7.8; the temperature is between 55°C; the stirring speed is 500 r / min.

[0059] iv. After dropping, let it stand for aging for 10 h, then filter, wash, and dry the precipitate to obtain the precursor of the material;

[0060] 2) Weigh the required lithium carbonate and the precursor material prepared in 1) with the stoichiometric ratio shown in the chemical formula Li 1.0 Li 0.15 Mn 0.5 Ni 0.05 Co 0.05 Fe 0.05 Cu 0.05 Zn 0.05 Mg 0.05 Al 0.05 O2, grind them together and mix evenly.

[0061] 3) Pre-calcine the above-mentioned well-ground mixture at 450 °C for 4 h, and then calcine it at 850 °C for 15 h to obtain the target layered lithium-rich manganese-based high-entropy cathode material.

[0062] Figure 1 Show the XRD pattern of the layered lithium-rich manganese-based high-entropy cathode material; Figure 2 Show the cyclic stability diagram of the layered lithium-rich manganese-based high-entropy cathode material.

[0063] Mix the above-prepared layered lithium-rich manganese-based high-entropy cathode material Li 1.0 Li 0.15 Mn 0.5 Ni 0.05 Co 0.05 Fe 0.05 Cu 0.05 Zn 0.05 Mg 0.05 Al 0.05 O₂ with carbon black and PVDF in a mass ratio of 8:1:1, grind it evenly with N-methylpyrrolidone as the solvent, then coat it on the aluminum foil, and place it in a blast drying oven at 100 °C for 12 h. After taking it out, roll it several times on a rolling press and then cut it into electrode discs. Use this as the positive electrode sheet, use the lithium sheet as the negative electrode sheet, the glass microfiber filter paper GF / D produced by whatman company, and the electrolyte is the high-voltage electrolyte for lithium-ion batteries produced by Beijing Research Institute of Chemical Reagents. Assemble it into a button battery in a glove box and test it on a Neware battery test system at a temperature of 25 °C at room temperature.

[0064] For the layered lithium-rich manganese-based high-entropy cathode material synthesized under this condition, when tested at a voltage range of 2.0 - 4.8 V and a current density of 25 mA / g, the initial discharge capacity is 275 mAh / g, the reversible discharge capacity at the 100th cycle is higher than 260 mAh / g, the capacity retention rate is greater than 94.5%, and the voltage decay is less than 130 mV.

[0065] Example 4. Synthesis of layered lithium-rich manganese-based high-entropy cathode material Li 1.0 Li 0.15 Mn 0.45 Ni 0.08 Co 0.0 8Fe 0.08 Cu 0.08 Ti 0.04 Al 0.04 O₂.

[0066] It is expected that the synthesized cathode material is 0.03 mol. Weigh the acetates of Li, Mn, Ni, Co, Fe, Cu, Mg, and Al according to the molar ratios shown in the above chemical formula. At the same time, add citric acid with a molar amount 4 times that of the metal elements and ethylene glycol with a molar amount 2 times that of the metal elements. Dissolve them in deionized water and perform rotary evaporation on a rotary evaporator to make a sol; the temperature is 80 °C and the rotation speed is 55 r / min. Place the obtained gel in an oven and dry it at 150 °C for 10 h to evaporate the sol into a gel; crush the obtained gel, pre-calcine the uniformly ground mixture at 400 °C for 5 h, and then calcine it at 900 °C for 15 h to obtain the target layered lithium-rich manganese-based high-entropy cathode material.

[0067] The layered lithium-rich manganese-based high-entropy cathode material Li 1.0 Li 0.15 Mn 0.45 Ni 0.08 Co 0.08 Fe 0.08 Cu 0.08 Ti 0.04 Al 0.04 O2 is mixed with carbon black and PVDF at a mass ratio of 8:1:1, ground evenly with N-methylpyrrolidone as the solvent, then coated on aluminum foil, and placed in a forced-air drying oven at 100 °C for 12 h. After taking it out, roll it several times on a rolling press and cut it into electrode discs. Use this as the positive electrode sheet, use a lithium sheet as the negative electrode sheet, the glass microfiber filter paper GF / D produced by whatman company, and the electrolyte is the high-voltage electrolyte for lithium-ion batteries produced by Beijing Research Institute of Chemical Reagents. Assemble a button battery in a glove box and test it on a Neware battery test system at a temperature of room temperature 25 °C.

[0068] For the material synthesized under this condition, when tested at a voltage range of 2.0 - 4.8 V and a current density of 25 mA / g, the initial discharge capacity is 275 mAh / g, the reversible discharge capacity at the 100th cycle is higher than 245 mAh / g, the capacity retention rate is ~89.1%, and the voltage decay is less than 100 mV.

[0069] Example 5. Synthesis of layered lithium-rich manganese-based high-entropy cathode material Li 1.0 Li 0.15 Mn 0.5 Ni 0.05 Co 0.05 Fe 0.05 Cu 0.05 Zn 0.05 Mg 0.05 Al 0.025 Zr 0.025 O2.

[0070] It is estimated that the synthesized cathode material is 0.03 mol. Weigh Li2CO3, MnO2, NiO, CoO, Fe2O3, CuO, ZnO, MgO, Al2O3 and ZrO2 according to the molar ratio shown in the above chemical formula. Mix and grind the above compounds evenly. After grinding evenly, put them into a porcelain boat and place it in a tube furnace. First, pre-burn at 450 °C for 4 h, then take it out, grind and mix evenly again, and then place it in the tube furnace and calcine at 850 °C for 10 h. After taking it out, grind it evenly to obtain the layered lithium-rich manganese-based high-entropy cathode material Li 1.0 Li 0.15 Mn 0.5 Ni 0.05 Co 0.05 Fe 0.05 Cu 0.05 Zn 0.05 Mg 0.05 Al 0.025 Zr 0.025 O2.

[0071] Mix the prepared layered lithium-rich manganese-based high-entropy cathode material Li 1.0 Li 0.15 Mn 0.5 Ni 0.05 Co 0.05 Fe 0.05 Cu 0.05 Zn 0.05 Mg 0.05 Al 0.025 Zr 0.025 O2 with carbon black and PVDF in a mass ratio of 8:1:1, grind evenly with N-methylpyrrolidone as the solvent, then coat it on aluminum foil, and place it in a blast drying oven at 100 °C for 12 h. After taking it out, roll it several times on a rolling press and then cut it into electrode discs. Use this as the positive electrode sheet, use a lithium sheet as the negative electrode sheet, the glass microfiber filter paper GF / D produced by whatman company, and the electrolyte is the high-voltage electrolyte for lithium-ion batteries produced by Beijing Research Institute of Chemical Reagents. Assemble a button battery in a glove box and test it on a Neware battery test system at a temperature of 25 °C at room temperature.

[0072] Under the conditions of the synthesized material, when tested at a voltage range of 2.0 - 4.8 V and a current density of 25 mA / g, the initial discharge capacity is 240 mAh / g, the reversible discharge capacity at the 100th cycle is higher than 195 mAh / g, the capacity retention rate is greater than 80%, and the voltage decay is less than 200 mV.

[0073] For Comparative Example 1, a conventional lithium-rich manganese-based cathode material Li 1.0 Li 0.2 Mn 0.54 Ni 0.13 Co 0.13O2

[0074] 1) Preparation of precursor:

[0075] i. Preparation of mixed salt solution: Weigh the sulfates of Mn, Ni, and Co according to the above molar ratio, dissolve them in deionized water, and prepare a mixed salt solution with a concentration of 2 mol / L;

[0076] ii. Dissolve Na2CO3 in deionized water to prepare an alkali solution with a concentration of 2 mol / L; Add ammonia water as a complexing agent with an ammonium ion concentration of 0.2 mol / L;

[0077] iii. Slowly and evenly add the mixed salt solution obtained in step i and the mixed alkali solution obtained in step ii into a container filled with deionized water at a speed of 1.5 mL / min. During the whole process, the pH value is maintained at about 7.8; the temperature is between 55°C; the stirring speed is 500 r / min;

[0078] iv. After the dropping is completed, let it stand for aging for 10 h, then filter, wash, and dry the precipitate to obtain the precursor material;

[0079] 2) Weigh the required lithium carbonate and the precursor material prepared in step 1) according to the stoichiometric ratio shown in the chemical formula Li 1.0 Li 0.2 Mn 0.54 Ni 0.13 Co 0.13 O2, put them together and grind to mix evenly;

[0080] 3) Pre-calcine the above evenly ground mixture at 450°C for 4 h, and then calcine it at 850°C for 15 h to obtain the target conventional lithium-rich manganese-based cathode material.

[0081] Figure 3 Show the XRD pattern of the conventional lithium-rich manganese-based cathode material; Figure 4 Show the cycle stability diagram of the conventional lithium-rich manganese-based cathode material.

[0082] The conventional lithium-rich manganese-based cathode material Li 1.0 Li 0.2 Mn 0.54 Ni 0.13 Co 0.13O2, carbon black, and PVDF were mixed at a mass ratio of 8:1:1, ground evenly with N-methylpyrrolidone as the solvent, then coated on aluminum foil, and placed in a forced-air drying oven at 100 °C for 12 h. After taking it out, it was rolled several times on a rolling press and then cut into electrode discs. This was used as the positive electrode sheet, a lithium sheet was used as the negative electrode sheet, a glass microfiber filter paper GF / D produced by whatman company, and the electrolyte was a high-voltage electrolyte for lithium-ion batteries produced by Beijing Research Institute of Chemical Reagents. It was assembled into a button battery in a glove box and tested on a Neware battery test system at a temperature of 25 °C (room temperature).

[0083] For the conventional lithium-rich manganese-based cathode material synthesized under this condition, when tested at a voltage range of 2.0 - 4.8 V and a current density of 25 mA / g, the initial discharge capacity was 260 mAh / g, the reversible discharge capacity at the 100th cycle was lower than 205 mAh / g, the capacity retention rate was lower than 80%, and the voltage decay was greater than 300 mV.

Claims

1. A layered lithium-rich manganese-based high-entropy cathode material with the chemical formula Li a [Li x Mn y A 1-x-y O2, where 0 < a ≤ 1, 0.1 ≤ x ≤ 0.25, 0.45 ≤ y ≤ 0.55; A is selected from at least 4 of Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Sn, Sb, Te, Ta, W, Ce, and their contents are represented by a1, a2, a3, ai…an respectively, where n represents a natural number ≥ 4, i represents any number from 1 to n, and 0 < ai ≤ 0.15, and satisfy The structure of the layered lithium-rich manganese-based high-entropy cathode material belongs to the space group or the C2 / m space group or is composed of both. The Li layer and the transition metal [Li x Mn y A 1-x-y layers are arranged alternately; the layered lithium-rich manganese-based high-entropy cathode material is prepared by a sol-gel method or a co-precipitation-high temperature solid-phase method.

2. The layered lithium-rich manganese-based high-entropy cathode material according to claim 1, wherein, 0.85 < a ≤ 1, 0.15 ≤ x ≤ 0.20, 0.48 ≤ y ≤ 0.54; 0.025 < ai ≤ 0.

05.

3. The layered lithium-rich manganese-based high-entropy cathode material according to claim 1, wherein, The layered lithium-rich manganese-based high-entropy cathode material is selected from one of the following materials: Li 1.0 Li 0.15 Mn 0.5 Ni 0.1 Co 0.05 Fe 0.05 Cu 0.05 Mg 0.05 Al 0.05 O2 Li 1.0 Li 0.15 Mn 0.5 Ni 0.05 Co 0.05 Fe 0.05 Cu 0.05 Zn 0.05 Mg 0.05 Al 0.05 O2 Li 1.0 Li 0.15 Mn 0.45 Ni 0.08 Co 0.08 Fe 0.08 Cu 0.08 Ti 0.04 Al 0.04 O2。 4. The preparation method of the layered lithium-rich manganese-based high-entropy cathode material according to any one of claims 1 to 3 is selected from one of the following preparation methods II and III: II. The sol-gel method, including the following steps: II1) Weigh soluble compounds of lithium, soluble compounds of Mn, and soluble compounds of A in the stoichiometric ratio shown in Li a [Li x Mn y A 1-x-y O2. At the same time, add citric acid with a molar amount 2 - 5 times that of the metal elements and ethylene glycol with a molar amount 1 - 3 times that of the metal elements. Dissolve all of them in deionized water to prepare a solution, and then perform rotary evaporation on a rotary evaporator to make a sol; II2) Place the gel in an oven and dry it at 120 - 150 °C for 5 - 12 h to evaporate the sol into a gel. II3) Grind the obtained gel, and pre-calcine the uniformly ground mixture at 150 - 550 °C for 4 - 10 h, followed by calcination at 750 - 950 °C for 8 - 20 h to obtain the target layered lithium-rich manganese-based high-entropy cathode material. III. Co-precipitation - high-temperature solid-state method, including the following steps: III1) Preparation of the precursor: i. Prepare a mixed solution of Mn and A: Weigh soluble compounds of Mn and A according to the ratio of Mn and A in the final cathode material, and dissolve them in deionized water to prepare a mixed solution with a concentration of 0.5 - 3.0 mol / L. ii. Dissolve NaOH and / or KOH or Na2CO3 and / or K2CO3 in deionized water to prepare a mixed alkali solution with a concentration of 0.5 - 3.0 mol / L; add ammonia water as a complexing agent, and the ammonium ion concentration is 0.1 - 2 times the alkali concentration. iii. Simultaneously and uniformly add the mixed solution obtained in step i and the mixed alkali solution obtained in step ii into a container filled with deionized water at a speed controlled at 0.5 - 2.5 mL / min. During the whole process, for carbonate precipitation, the pH value is maintained between 7 and 9, and for hydroxide precipitation, the pH value is maintained between 10 and 12, and the temperature is between 50 and 80 °C. iv. After dropping, let it stand for aging for 1 - 16 h, then filter, wash, and dry the precipitate to obtain the precursor material. III 2) Weigh the lithium compound with the stoichiometric ratio shown in Lia[Li x Mn y A 1-x-y O2 and grind it together with the precursor material prepared in step III 1), and mix evenly; III3) Pre-calcine the uniformly ground mixture at 150 - 550 °C for 4 - 10 h, followed by calcination at 750 - 950 °C for 8 - 20 h to obtain the target layered lithium-rich manganese-based high-entropy cathode material.

5. The preparation method according to claim 4, characterized in that, In step II1) of the sol-gel method, the soluble compound of lithium is selected from one or more of lithium carbonate, oxalate, acetate, sulfate, nitrate, and halide; the soluble compound of Mn is selected from one or more of Mn acetate, nitrate, sulfate, and halide; the soluble compound of A is selected from one or more of A acetate, nitrate, sulfate, and halide, where A is at least 4 of Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Sn, Sb, Te, Ta, W, and Ce.

6. The preparation method according to claim 4, characterized in that, In step i of the coprecipitation-high temperature solid phase method, the soluble compound of Mn is selected from one or more of acetate, nitrate, sulfate, and halide of Mn; the soluble compound of A is selected from one or more of acetate, nitrate, sulfate, and halide of A, where A is at least 4 of Mg, Al, Si, Ca, Ti, V, Cr, Fe, Co, Ni, Cu, Zn, Zr, Nb, Mo, Ru, Sn, Sb, Te, Ta, W, Ce; in step III2), the compound of lithium is selected from one or more of carbonate, oxalate, acetate, sulfate, nitrate, halide, oxide, and hydroxide of lithium.

7. A positive electrode sheet, comprising the layered lithium-rich manganese-based high-entropy positive electrode material according to any one of claims 1 to 3.

8. A battery, comprising a positive electrode sheet, a negative electrode sheet, a separator and an electrolyte, characterized in that, The positive electrode sheet contains the layered lithium-rich manganese-based high-entropy positive electrode material according to any one of claims 1 to 3.

Images