A high-power lithium-rich manganese-based positive electrode material, a preparation method thereof, a positive electrode sheet and a lithium ion battery

Abstract

The application belongs to the field of lithium batteries, and particularly relates to a high-power lithium-rich manganese-based positive electrode material, a preparation method thereof, a positive electrode sheet and a lithium ion battery. The high-power lithium-rich manganese-based positive electrode material has a three-layer core-shell structure, and comprises a gradient pore inner core, an in-situ spinel transition layer and a composite coating layer from inside to outside. The application accelerates lithium ion transmission through the gradient pore design, stabilizes the lattice structure through the in-situ spinel transition layer, and suppresses the interface side reaction through the composite coating layer. The preparation method does not need secondary sintering, and has simple process and low energy consumption. The prepared lithium ion battery can realize ≥10C continuous discharge, ≥20C pulse discharge, a capacity retention rate ≥80% at -20 DEG C, a capacity retention rate ≥90% after 800 cycles, and is suitable for the field of high-power, wide-temperature-range and high-safety demand power batteries such as unmanned aerial vehicles.

Description

Technical Field

[0001] This invention belongs to the field of lithium batteries, specifically relating to a high-power lithium-rich manganese-based cathode material and its preparation method, as well as a cathode sheet and a lithium-ion battery. Background Technology

[0002] The rapid proliferation of drones in fields such as plant protection, inspection, logistics, and emergency rescue places comprehensive demands on power batteries, requiring high power density, high safety, wide temperature range, long cycle life, and low cost. Currently, commercial drone batteries mainly adopt lithium cobalt oxide, high-nickel ternary, and lithium iron phosphate systems. Among them, lithium cobalt oxide has excellent rate performance but high cost and poor thermal stability; high-nickel ternary batteries have high energy density but are prone to oxygen evolution at high temperatures and have poor cycle and safety performance; lithium iron phosphate is safe and stable, but its energy density and power density are insufficient to meet the requirements of long endurance and high current output.

[0003] In contrast, lithium-rich manganese-based cathode materials have become the preferred system for next-generation high-energy-density batteries due to their high specific capacity (>250mAh / g), high operating voltage, abundant manganese resources, and low cost. However, they face the following problems: (1) poor lithium-ion diffusion kinetics, large polarization, and insufficient power density during high-rate (≥10C) discharge; (2) severe loss of lattice oxygen and structural phase change during cycling, resulting in capacity decay and voltage drop; (3) high interface impedance, poor adaptability to high and low temperatures, low capacity retention at -20℃, and severe high-temperature side reactions; (4) traditional modification methods require secondary sintering, which is complex, energy-intensive, and difficult to industrialize.

[0004] Existing technologies modify lithium-rich manganese-based cathode materials through methods such as elemental doping, surface coating, and acid treatment. However, these optimization methods are limited and offer only minor performance improvements. Therefore, this invention proposes a technical solution. Summary of the Invention

[0005] To address the limitations of existing technologies, such as the reliance on single optimization methods and limited performance improvements, this invention provides a three-layer core-shell structure lithium-rich manganese-based cathode material consisting of a gradient channel core, an in-situ spinel transition layer, and a composite coating layer, along with a matching high-power lithium-ion battery. This material enables continuous discharge at high rates, pulse discharge, stable operation over a wide temperature range, and long cycle life, thus meeting the high-performance operational requirements of unmanned aerial vehicles (UAVs).

[0006] The present invention provides a high-power lithium-rich manganese-based cathode material, wherein the high-power lithium-rich manganese-based cathode material has a three-layer core-shell structure, including a gradient channel core, an in-situ spinel transition layer, and a composite coating layer from the inside out; wherein:

[0007] The general formula for the gradient channel core component is: xLi2MnO3·(1-x)LiNi a Mn b M1-a-b O2, where 0.1≤x≤0.5, 0.5≤a<1, 0<b<0.5, and M is a combination of four or more of Zr, Al, Nb, Ta, Fe, Ti, V, Mg, Cr, Co, Cu, Zn, Sn, Te, and La; it has high entropy doping characteristics and can stabilize the crystal structure; In the in-situ spinel transition layer, the spinel phase accounts for 10-50% of the total mass of the in-situ spinel transition layer, Mn 3+ / (Mn) 3+ +Mn 4+ =0.05-0.25 (molar ratio); whereby the presence of spinel phase can provide three-dimensional lithium-ion channels, which helps the rapid insertion and extraction of lithium ions and is beneficial to high rate performance; In the composite coating layer, LiF accounts for 60-80%, and the remainder is at least one of AlF3, MgF2, LiAlO2, Li3PO4, LiNbO3, LiTaO3, and Li2ZrO3; it can reduce interfacial impedance, suppress side reactions, and improve high-temperature and cycling stability.

[0008] Preferably, the gradient channel core is spherical or near-spherical, with primary particles of 200-500 nm and secondary particles (D50 = 3-12 μm, composed of aggregated primary particles) having a D50 of 3-12 μm; the pore size in the gradient channel core is 50-200 nm, and the specific surface area is 5-10 m². 2 / g, can significantly improve lithium-ion transport rate; And / or, the thickness of the in-situ spinel transition layer is 10-150 nm; And / or, the thickness of the composite coating layer is 20-80 nm.

[0009] Preferably, the lithium-ion diffusion coefficient of the high-power lithium-rich manganese-based cathode material is ≥1×10⁻⁶. -8 cm 2 / s.

[0010] Based on the same technical concept, the present invention further provides a method for preparing a high-power lithium-rich manganese-based cathode material, the method comprising the following steps: (1) According to the elemental molar ratio of the target cathode material, Li source, Mn source, Ni source and M source are mixed to prepare a uniform dispersion; then the uniform dispersion is spray-dried and sintered to obtain the gradient channel core. (2) The gradient channel core is immersed in a reducing organic acid solution and stirred to react. After the spinel transition layer is generated in situ, an intermediate product is obtained. (3) The intermediate product is mixed with the raw materials that make up the composite coating layer, and then the composite coating is carried out by high-energy ball milling to obtain the high-power lithium-rich manganese-based cathode material; The high-power lithium-rich manganese-based cathode material has a three-layer core-shell structure, including a gradient channel core, an in-situ spinel transition layer, and a composite coating layer from the inside out.

[0011] Preferably, in step (1), the Li source is one or a combination of two or more of lithium sulfate, lithium acetate, lithium carbonate, lithium oxalate, lithium hydroxide, lithium nitrate, and lithium chloride; wherein the Li source may exceed the theoretical usage by no more than 10%. And / or, the Mn source is one or a combination of two or more of manganese sulfate, manganese nitrate, manganese acetate, manganese carbonate, manganese oxalate, manganese tetroxide, and manganese chloride; And / or, the Ni source is one or a combination of two or more of nickel sulfate, nickel nitrate, nickel acetate, nickel carbonate, nickel oxalate, nickel oxide, and nickel chloride; And / or, the M source is a sulfate, nitrate, acetate, carbonate, oxalate, oxide, or chloride containing four or more of the following: Zr, Al, Nb, Ta, Fe, Ti, V, Mg, Cr, Co, Cu, Zn, Sn, Te, and La. And / or, after spray drying, sintering is carried out: first pre-fired at a temperature of 400-500℃ for 4-6 hours; then sintered at a temperature of 750-900℃ for 8-16 hours.

[0012] Preferably, in step (2), the gradient channel core is immersed in a reducing organic acid solution at 20-30℃ and 60-80r / min for stirring reaction for 5-240min. After the spinel transition layer is generated in situ, the intermediate product is obtained. It is prepared by in situ reduction of organic acid at room temperature (20-30℃), without secondary sintering, which can suppress oxygen loss and structural phase change and expand lithium ion transport channels. And / or, the reducing organic acid solution is one of tartaric acid, malic acid, citric acid, ascorbic acid, oxalic acid, lactic acid, glycolic acid, or maleic acid.

[0013] Based on the same technical concept, the present invention provides another positive electrode sheet, which includes the high-power lithium-rich manganese-based positive electrode material.

[0014] Based on the same technical concept, the present invention further provides a lithium-ion battery, which includes a positive electrode, a negative electrode, an electrolyte, a ceramic separator, and a casing. The specific preparation method includes the following steps: (S1) Positive electrode preparation: The above-mentioned three-layer core-shell structure high-power lithium-rich manganese-based positive electrode material is used as the active material. The conductive agent is a composite system of carbon nanotubes, graphene, and acetylene black. Polyvinylidene fluoride is used as the binder. The positive electrode slurry is prepared by mixing the materials in a mass ratio of 92:4:4. The slurry is coated onto an aluminum foil current collector, and the positive electrode is obtained after drying and rolling. The compaction density of the positive electrode is controlled to be 3.3-4.0 g / cm³. 3 ; (S2) Preparation of negative electrode sheet: Silicon / graphite composite negative electrode material is used as active material, in which silicon accounts for 10-20% by mass. Acetylene black is selected as the conductive agent, and sodium carboxymethyl cellulose and styrene-butadiene rubber are selected as binders. They are mixed in a mass ratio of 94:2:2:2 to prepare negative electrode slurry, which is coated on copper foil current collector. After drying and rolling, the negative electrode sheet is obtained, which takes into account both high capacity and high rate charge and discharge performance. (S3) Electrolyte preparation: A composite lithium salt system composed of LiFSI and LiPF6 is adopted. The solvent is a mixed solvent of ethylene carbonate, dimethyl carbonate, ethyl methyl carbonate and some fluorocarbonate. The functional additives include at least trimethyl phosphate (TMP) and vinylene carbonate (VC) to meet the requirements of high voltage, wide temperature range and high safety. (S4) The diaphragm is made of Al2O3-SiO2 composite ceramic coated diaphragm; (S5) The above positive electrode, negative electrode and separator are made into a cell by winding or stacking process, and after being installed in the casing, the above electrolyte is injected. The lithium-ion battery is obtained by sealing, formation and capacity testing processes.

[0015] Preferably, the interface impedance of the lithium-ion battery is ≤80Ω·cm. 2 5C discharge capacity retention rate ≥95%, 10C discharge capacity retention rate ≥90%, thermal runaway temperature ≥220℃.

[0016] The beneficial effects of this invention are as follows: 1. Significantly improved kinetic performance and excellent high-rate discharge capability: The gradient channel core is constructed with continuous gradient channels of 50-200nm, and the specific surface area is controlled at 5-10m². 2 / g, significantly shortening the lithium-ion diffusion path, while the synergistic effect of high-entropy doping of multiple elements optimizes the crystal structure, making the lithium-ion diffusion coefficient of the material ≥1×10 -8 cm 2 / s, interface impedance ≤80Ω·cm 2 It achieves a 5C discharge capacity retention rate of ≥95% and a 10C discharge capacity retention rate of ≥90% at room temperature, which can meet the requirements of high-current continuous discharge and pulse discharge of UAVs.

[0017] 2. Significantly enhanced structural stability and extended cycle life: The in-situ generated spinel transition layer has a high degree of matching with the core lattice, effectively suppressing lattice oxygen loss and irreversible phase transition from layered phase to spinel phase during cycling; the composite coating layer isolates the positive electrode material from direct contact with the electrolyte, reducing interfacial side reactions and transition metal dissolution, enabling the battery to retain ≥90% capacity after 800 cycles at 2C / 10C, ​​solving the problems of rapid cycle decay and severe discharge voltage decay of traditional lithium-rich manganese-based materials.

[0018] 3. Outstanding thermal stability and wide temperature range performance, and excellent safety performance: The three-layer core-shell structure works synergistically to improve the thermal stability of the material, with a thermal runaway initiation temperature ≥220℃; the composite coating layer reduces the interfacial impedance and improves the lithium-ion transport capability at low temperatures, enabling the battery to retain ≥80% of its capacity at -20℃. At the same time, side reactions are effectively suppressed at high temperatures, achieving stable operation in a wide temperature range of -20℃ to 60℃, which greatly improves the safety and reliability of the battery in extreme environments.

[0019] 4. The preparation process is simple and efficient, and the industrialization feasibility is high: The spinel transition layer is prepared by the room temperature reducing organic acid in-situ reduction method, which eliminates the need for secondary high-temperature sintering, significantly reducing energy consumption and production costs; the high-energy ball milling composite coating process is easy to operate and can be easily scaled up for production; the overall process flow is short, the equipment requirements are low, and it has good compatibility with existing cathode material production lines, and has good prospects for industrial application.

[0020] 5. Balanced overall performance, suitable for multiple application scenarios: The material of this invention has the advantages of high specific capacity (>250mAh / g), high power density, high safety, long cycle life and low cost. It is not only suitable for drone power batteries, but can also be applied to fields with high requirements for power density and safety performance, such as power tools, start-stop power supplies for new energy vehicles and energy storage power stations. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be described in detail below. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other implementation methods obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0022] Example 1 This embodiment provides a method for preparing a high-power lithium-rich manganese-based cathode material, the method comprising the following steps: (1) The target material to be prepared is: 0.4Li2MnO3·0.6LiNi 0.5 Mn 0.35 Co0.05 Zr 0.04 Al 0.03 Mg 0.03 O2 cathode material, the surface of which is a LiF-LiAlO2 composite coating layer; (2) Lithium carbonate (2% excess), manganese tetroxide, nickel oxide, cobalt nitrate, zirconium dioxide, aluminum oxide and magnesium nitrate were added to water according to the molar ratio of metal elements, ground and dispersed, spray dried and pre-calcined at 450℃ for 4h, and then sintered at 800℃ for 14h to obtain gradient pore core material. (3) Immerse the gradient pore core material in a 15 mmol / L tartaric acid solution (pH=4), stir at 25°C and 60 r / min for 3 h, and after the spinel transition layer is generated in situ, filter, wash and dry to obtain the intermediate product; (4) The intermediate product and LiF-LiAlO2 are subjected to high-energy ball milling to obtain the target high-power lithium-rich manganese-based cathode material. The mass ratio of LiF-LiAlO2 in the target cathode material is 1%, and the mass ratio of LiF to LiAlO2 is 7:3.

[0023] The target cathode material was characterized, revealing an internal pore size of 80-100 nm and a specific surface area of ​​6.8 m². 2 / g.

[0024] Furthermore, the target high-power lithium-rich manganese-based cathode material was fabricated into a battery, and then the following tests were performed: (i) 10C continuous discharge test and 20C pulse discharge test at room temperature (25°C); (ii) 5C discharge test at -20℃; (iii) Cyclic test at room temperature (25°C) with 2C charging and 10C discharging; (iv) Continuous discharge test at 10C at a high temperature of 45℃; (v) High temperature 45°C, 1C charge 10C discharge cycle test; (vi) Battery thermal runaway test; (vii) Test the lithium-ion diffusion coefficient and interface impedance.

[0025] The test results are as follows: (i) At room temperature (25°C), the capacity retention rate for continuous discharge at 10C is 95%, and the capacity retention rate for pulse discharge at 20C is 93%; (ii) At a low temperature of -20°C, the 5C discharge capacity retention rate is 82%; (iii) At room temperature (25°C), after 800 cycles of 2C charging and 10C discharging, the battery capacity retention rate is 92.5%; (iv) At a high temperature of 45°C, the 10C continuous discharge capacity retention rate is 97%; (v) At a high temperature of 45°C, after 800 cycles of 1C charging and 10C discharging, the battery capacity retention rate is 85%; (vi) The battery thermal runaway initiation temperature is 230°C; (vii) Lithium-ion diffusion coefficient 1.46 × 10 -8 cm 2 / s, interface impedance 60Ω·cm 2 .

[0026] Example 2 This embodiment provides a method for preparing a high-power lithium-rich manganese-based cathode material, the method comprising the following steps: (1) The target material to be prepared is: 0.3Li2MnO3·0.7LiNi 0.6 Mn 0.25 Ti 0.05 Nb 0.04 Fe 0.03 Cr 0.03 O2 cathode material, the surface of which is a LiF-MgF2 composite coating layer; (2) Lithium hydroxide (5% excess), manganese sulfate, nickel acetate, titanium dioxide, niobium pentoxide, ferric oxide and chromium oxide were added to water according to the molar ratio of metal elements, ground and dispersed, spray dried and pre-calcined at 420℃ for 5h, and then sintered at 850℃ for 12h to obtain gradient pore core material. (3) The gradient pore core material was immersed in 20 mmol / L citric acid solution (pH=3.5), stirred at 22℃ and 70 r / min for 2 h, and after the spinel transition layer was generated in situ, it was filtered, washed and dried to obtain the intermediate product; (4) The intermediate product and LiF-MgF2 are ball-milled at high energy to obtain the target high-power lithium-rich manganese-based cathode material. The mass ratio of LiF-MgF2 in the target cathode material is 1.2%, and the mass ratio of LiF to MgF2 is 8:2.

[0027] The target cathode material was characterized, revealing an internal pore size of 78-105 nm and a specific surface area of ​​6.6 m². 2 / g.

[0028] Furthermore, the target high-power lithium-rich manganese-based cathode material was fabricated into a battery, and then the following tests were performed: (i) 10C continuous discharge test and 20C pulse discharge test at room temperature (25°C); (ii) 5C discharge test at -20℃; (iii) Cyclic test at room temperature (25°C) with 2C charging and 10C discharging; (iv) Continuous discharge test at 10C at a high temperature of 45℃; (v) High temperature 45°C, 1C charge 10C discharge cycle test; (vi) Battery thermal runaway test; (vii) Test the lithium-ion diffusion coefficient and interface impedance.

[0029] The test results are as follows: (i) At room temperature (25°C), the capacity retention rate for continuous discharge at 10C is 94%, and the capacity retention rate for pulse discharge at 20C is 92%; (ii) At a low temperature of -20°C, the 5C discharge capacity retention rate is 81%; (iii) At room temperature (25°C), after 800 cycles of 2C charging and 10C discharging, the battery capacity retention rate is 91.8%; (iv) At a high temperature of 45°C, the 10C continuous discharge capacity retention rate is 95%; (v) At a high temperature of 45°C, after 800 cycles of 1C charging and 10C discharging, the battery capacity retention rate is 82%; (vi) The battery thermal runaway initiation temperature is 225°C; (vii) Lithium-ion diffusion coefficient 1.42 × 10 -8 cm 2 / s, interface impedance 65Ω·cm 2 .

[0030] Example 3 This embodiment provides a method for preparing a high-power lithium-rich manganese-based cathode material, the method comprising the following steps: (1) The target material to be prepared is: 0.2Li2MnO3·0.8LiNi 0.7 Mn 0.15 V 0.05 Ta 0.04 Cu 0.03 Zn 0.03 O2 cathode material, the surface of which is a LiF-Li3PO4 composite coating layer; (2) Lithium carbonate (3% excess), manganese nitrate, nickel carbonate, vanadium pentoxide, tantalum pentoxide, copper oxide and zinc oxide were added to water according to the molar ratio of metal elements, ground and dispersed, spray dried and pre-calcined at 480℃ for 4h, and then sintered at 780℃ for 16h to obtain gradient pore core material. (3) The gradient pore core material was immersed in 10 mmol / L ascorbic acid solution (pH=4.5), stirred at 28℃ and 75 r / min for 4 h, and after the spinel transition layer was generated in situ, it was filtered, washed and dried to obtain the intermediate product. (4) The intermediate product and LiF-Li3PO4 are subjected to high-energy ball milling to obtain the target high-power lithium-rich manganese-based cathode material. The mass ratio of LiF-Li3PO4 in the target cathode material is 0.8%, and the mass ratio of LiF to Li3PO4 is 6.5:3.5.

[0031] The target cathode material was characterized, revealing an internal pore size of 82-110 nm and a specific surface area of ​​7.1 m². 2 / g.

[0032] Furthermore, the target high-power lithium-rich manganese-based cathode material was fabricated into a battery, and then the following tests were performed: (i) 10C continuous discharge test and 20C pulse discharge test at room temperature (25°C); (ii) 5C discharge test at -20℃; (iii) Cyclic test at room temperature (25°C) with 2C charging and 10C discharging; (iv) Continuous discharge test at 10C at a high temperature of 45℃; (v) High temperature 45°C, 1C charge 10C discharge cycle test; (vi) Battery thermal runaway test; (vii) Test the lithium-ion diffusion coefficient and interface impedance.

[0033] The test results are as follows: (i) At room temperature (25°C), the capacity retention rate for continuous discharge at 10C is 96%, and the capacity retention rate for pulse discharge at 20C is 94%. (ii) At a low temperature of -20°C, the 5C discharge capacity retention rate is 83%; (iii) At room temperature (25°C), after 800 cycles of 2C charging and 10C discharging, the battery capacity retention rate is 93.2%; (iv) At a high temperature of 45°C, the 10C continuous discharge capacity retention rate is 97%; (v) At a high temperature of 45°C, after 800 cycles of 1C charging and 10C discharging, the battery capacity retention rate is 87%; (vi) The battery thermal runaway initiation temperature is 235°C; (vii) Lithium-ion diffusion coefficient 1.51 × 10 -8 cm 2 / s, interface impedance 56Ω·cm 2 .

[0034] Example 4 This embodiment provides a method for preparing a high-power lithium-rich manganese-based cathode material, the method comprising the following steps: (1) The target material to be prepared is: 0.5Li₂MnO₃·0.5LiNi 0.55 Mn 0.3 Sn 0.05 La 0.04 Te 0.03 Co 0.03 O2 cathode material, the surface of which is a LiF-LiNbO3 composite coating layer; (2) Lithium acetate (8% excess), manganese chloride, nickel oxalate, tin dioxide, lanthanum oxide, tellurium dioxide and cobalt nitrate were added to water according to the molar ratio of metal elements, ground and dispersed, spray dried and pre-calcined at 400℃ for 6 hours, and then sintered at 900℃ for 8 hours to obtain gradient pore core material. (3) Immerse the gradient pore core material in a 25 mmol / L oxalic acid solution (pH=3), stir at 20℃ and 65 r / min for 1 h, and after the spinel transition layer is generated in situ, filter, wash and dry to obtain the intermediate product; (4) The intermediate product and LiF-LiNbO3 are subjected to high-energy ball milling to obtain the target high-power lithium-rich manganese-based cathode material. The mass ratio of LiF-LiNbO3 in the target cathode material is 1.5%, and the mass ratio of LiF to LiNbO3 is 7.5:2.5.

[0035] The target cathode material was characterized, revealing an internal pore size of 60-95 nm and a specific surface area of ​​6.1 m². 2 / g.

[0036] Furthermore, the target high-power lithium-rich manganese-based cathode material was fabricated into a battery, and then the following tests were performed: (i) 10C continuous discharge test and 20C pulse discharge test at room temperature (25°C); (ii) 5C discharge test at -20℃; (iii) Cyclic test at room temperature (25°C) with 2C charging and 10C discharging; (iv) Continuous discharge test at 10C at a high temperature of 45℃; (v) High temperature 45°C, 1C charge 10C discharge cycle test; (vi) Battery thermal runaway test; (vii) Test the lithium-ion diffusion coefficient and interface impedance.

[0037] The test results are as follows: (i) At room temperature (25°C), the capacity retention rate for continuous discharge at 10C is 93%, and the capacity retention rate for pulse discharge at 20C is 91%; (ii) At a low temperature of -20°C, the 5C discharge capacity retention rate is 80%; (iii) At room temperature (25°C), after 800 cycles of 2C charging and 10C discharging, the battery capacity retention rate is 90.5%; (iv) At a high temperature of 45°C, the 10C continuous discharge capacity retention rate is 94%; (v) At a high temperature of 45°C, after 800 cycles of 1C charging and 10C discharging, the battery capacity retention rate is 81%; (vi) The battery thermal runaway initiation temperature is 222℃; (vii) Lithium-ion diffusion coefficient 1.40 × 10 -8 cm 2 / s, interface impedance 68Ω·cm 2 .

[0038] Example 5 This embodiment provides a method for preparing a high-power lithium-rich manganese-based cathode material, the method comprising the following steps: (1) The target material to be prepared is: 0.1Li2MnO3·0.9LiNi 0.8 Mn 0.1 Zr 0.03 Al 0.03 Mg 0.02 Ti 0.02 O2 cathode material, the surface of which is a LiF-Li2ZrO3 composite coating layer; (2) Lithium nitrate (1% excess), manganese carbonate, nickel oxide, zirconium dioxide, aluminum oxide, magnesium nitrate and titanium dioxide were added to water according to the molar ratio of metal elements, ground and dispersed, spray dried and pre-calcined at 500℃ for 4h, and then sintered at 750℃ for 15h to obtain gradient pore core material. (3) The gradient pore core material was immersed in 18 mmol / L malic acid solution (pH=4.2), stirred at 30℃ and 80 r / min for 3.5 h, and after the spinel transition layer was generated in situ, it was filtered, washed and dried to obtain the intermediate product; (4) The intermediate product and LiF-Li2ZrO3 are subjected to high-energy ball milling to obtain the target high-power lithium-rich manganese-based cathode material. The mass ratio of LiF-Li2ZrO3 in the target cathode material is 0.9%, and the mass ratio of LiF to Li2ZrO3 is 7:3.

[0039] The target cathode material was characterized, revealing an internal pore size of 95-115 nm and a specific surface area of ​​7.8 m². 2 / g.

[0040] Furthermore, the target high-power lithium-rich manganese-based cathode material was fabricated into a battery, and then the following tests were performed: (i) 10C continuous discharge test and 20C pulse discharge test at room temperature (25°C); (ii) 5C discharge test at -20℃; (iii) Cyclic test at room temperature (25°C) with 2C charging and 10C discharging; (iv) Continuous discharge test at 10C at a high temperature of 45℃; (v) High temperature 45°C, 1C charge 10C discharge cycle test; (vi) Battery thermal runaway test; (vii) Test the lithium-ion diffusion coefficient and interface impedance.

[0041] The test results are as follows: (i) At room temperature (25°C), the capacity retention rate for continuous discharge at 10C is 97%, and the capacity retention rate for pulse discharge at 20C is 95%; (ii) At a low temperature of -20°C, the 5C discharge capacity retention rate is 84%; (iii) At room temperature (25°C), after 800 cycles of 2C charging and 10C discharging, the battery capacity retention rate is 94.1%; (iv) At a high temperature of 45°C, the 10C continuous discharge capacity retention rate is 97%; (v) At a high temperature of 45°C, after 800 cycles of 1C charging and 10C discharging, the battery capacity retention rate is 88%; (vi) The battery thermal runaway initiation temperature is 240°C; (vii) Lithium-ion diffusion coefficient 1.53 × 10 -8 cm 2 / s, interface impedance 55Ω·cm 2 .

[0042] Comparative Example This comparative example provides a method for preparing a conventional lithium-rich manganese-based cathode material, the method comprising the following steps: (1) The target material to be prepared is: 0.4Li2MnO3·0.6LiNi 0.5 Mn 0.3 Co 0.2 O2 cathode material, the surface of which is a LiF-LiAlO2 composite coating layer; (2) Lithium carbonate and Ni 0.3 Mn 0.58 Co 0.12After the (OH)2 precursor was mixed evenly at a molar ratio of 1.42:1, it was first sintered at 450℃ for 4 hours, and then sintered at 800℃ for 14 hours to obtain the uncoated cathode material. (3) The uncoated cathode material and LiF-LiAlO2 are ball-milled at high energy to obtain the target lithium-rich manganese-based cathode material. The mass ratio of LiF-LiAlO2 in the target cathode material is 1%, and the mass ratio of LiF to LiAlO2 is 7:3.

[0043] The target cathode material was characterized, revealing an internal pore size <10 nm and a specific surface area of ​​3.3 m². 2 / g.

[0044] Furthermore, the target cathode material is fabricated into a battery, and then the following tests are performed: (i) 10C continuous discharge test and 20C pulse discharge test at room temperature (25°C); (ii) 5C discharge test at -20℃; (iii) Cyclic test at room temperature (25°C) with 2C charging and 10C discharging; (iv) Continuous discharge test at 10C at a high temperature of 45℃; (v) High temperature 45°C, 1C charge 10C discharge cycle test; (vi) Battery thermal runaway test; (vii) Test the lithium-ion diffusion coefficient and interface impedance.

[0045] The test results are as follows: (i) At room temperature of 25°C, the capacity retention rate of 10C continuous discharge is 50%, and it cannot discharge with 20C pulse. (ii) At a low temperature of -20°C, the 5C discharge capacity retention rate is 55%; (iii) At room temperature of 25°C, after 200 cycles of 2C charging and 10C discharging, the battery capacity decays to 0. (iv) At a high temperature of 45°C, the capacity retention rate during continuous 10C discharge is 70%; (v) At a high temperature of 45°C, after 120 cycles of 1C charging and 10C discharging, the battery capacity decays to 0. (vi) The battery thermal runaway initiation temperature is 205°C; (vii) Lithium-ion diffusion coefficient 1.23 × 10 -8 cm 2 / s, interface impedance 165Ω·cm 2 .

[0046] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A high-power lithium-rich manganese-based cathode material, characterized in that, The high-power lithium-rich manganese-based cathode material has a three-layer core-shell structure, including a gradient channel core, an in-situ spinel transition layer, and a composite coating layer from the inside out; wherein: The general formula for the gradient channel core component is: xLi2MnO3·(1-x)LiNi a Mn b M 1-a-b O2, where 0.1≤x≤0.5, 0.5≤a<1, 0<b<0.5, and M is a combination of four or more of Zr, Al, Nb, Ta, Fe, Ti, V, Mg, Cr, Co, Cu, Zn, Sn, Te, and La; In the in-situ spinel transition layer, the spinel phase accounts for 10-50% of the total mass of the in-situ spinel transition layer, Mn 3+ / (Mn) 3+ +Mn 4+ =0.05-0.25; In the composite coating layer, LiF accounts for 60-80%, and the remainder is at least one of AlF3, MgF2, LiAlO2, Li3PO4, LiNbO3, LiTaO3, and Li2ZrO3.

2. The high-power lithium-rich manganese-based cathode material according to claim 1, characterized in that, The primary particles of the gradient channel core have a size of 200-500 nm, and the secondary particles have a D50 of 3-12 μm; the pore size in the gradient channel core is 50-200 nm, and the specific surface area is 5-10 m². 2 / g; And / or, the thickness of the in-situ spinel transition layer is 10-150 nm; And / or, the thickness of the composite coating layer is 20-80 nm.

3. The high-power lithium-rich manganese-based cathode material according to claim 1, characterized in that, The lithium-ion diffusion coefficient of the high-power lithium-rich manganese-based cathode material is ≥1×10⁻⁶. -8 cm 2 / s.

4. The method for preparing the high-power lithium-rich manganese-based cathode material according to any one of claims 1-3, characterized in that, The preparation method includes the following steps: (1) According to the elemental molar ratio of the target cathode material, Li source, Mn source, Ni source and M source are mixed to prepare a uniform dispersion; then the uniform dispersion is spray-dried and sintered to obtain the gradient channel core. (2) The gradient channel core is immersed in a reducing organic acid solution and stirred to react. After the spinel transition layer is generated in situ, an intermediate product is obtained. (3) The intermediate product is mixed with the raw materials that make up the composite coating layer, and then the composite coating is carried out by high-energy ball milling to obtain the high-power lithium-rich manganese-based cathode material; The high-power lithium-rich manganese-based cathode material has a three-layer core-shell structure, including a gradient channel core, an in-situ spinel transition layer, and a composite coating layer from the inside out.

5. The method for preparing the high-power lithium-rich manganese-based cathode material according to claim 4, characterized in that, In step (1), the Li source is one or a combination of two or more of lithium sulfate, lithium acetate, lithium carbonate, lithium oxalate, lithium hydroxide, lithium nitrate, and lithium chloride. And / or, the Mn source is one or a combination of two or more of manganese sulfate, manganese nitrate, manganese acetate, manganese carbonate, manganese oxalate, manganese tetroxide, and manganese chloride; And / or, the Ni source is one or a combination of two or more of nickel sulfate, nickel nitrate, nickel acetate, nickel carbonate, nickel oxalate, nickel oxide, and nickel chloride; And / or, the M source is a sulfate, nitrate, acetate, carbonate, oxalate, oxide, or chloride containing four or more of the following: Zr, Al, Nb, Ta, Fe, Ti, V, Mg, Cr, Co, Cu, Zn, Sn, Te, and La. And / or, after spray drying, sintering is carried out: first pre-fired at a temperature of 400-500℃ for 4-6 hours; then sintered at a temperature of 750-900℃ for 8-16 hours.

6. The method for preparing the high-power lithium-rich manganese-based cathode material according to claim 4, characterized in that, In step (2), the gradient channel core is immersed in a reducing organic acid solution at 20-30℃ and 60-80r / min for stirring reaction for 5-240min. After the spinel transition layer is generated in situ, the intermediate product is obtained. And / or, the reducing organic acid solution is one of tartaric acid, malic acid, citric acid, ascorbic acid, oxalic acid, lactic acid, glycolic acid, or maleic acid.

7. A positive electrode plate, characterized in that, The high-power lithium-rich manganese-based cathode material includes any one of claims 1-3 or the high-power lithium-rich manganese-based cathode material obtained by the preparation method described in any one of claims 4-6.

8. A lithium-ion battery, characterized in that, The high-power lithium-rich manganese-based cathode material included in any one of claims 1-3, or the high-power lithium-rich manganese-based cathode material obtained by the preparation method described in any one of claims 4-6, or the cathode sheet described in claim 7.

9. The lithium-ion battery according to claim 8, characterized in that, The interface impedance of the lithium-ion battery is ≤80Ω·cm 2 5C discharge capacity retention rate ≥95%, 10C discharge capacity retention rate ≥90%, thermal runaway temperature ≥220℃.