Lithium-rich manganese-based positive electrode material and preparation method and application thereof

Abstract

The invention belongs to the technical field of new energy, and particularly relates to a lithium-rich manganese-based positive electrode material and a preparation method and application thereof. The method comprises the following steps: S1, respectively mixing lithium-rich manganese-based positive electrode material precursors 1 and 2 with a lithium source to obtain mixed materials 1 and 2; the composition of the lithium-rich manganese-based positive electrode material precursors 1 and 2 is Ni (alpha) Co (beta) Mn (gamma) (OH) 2; 0.23 < = alpha < = 0.31, 0.04 < = beta < = 0.12, and 0.65 < = gamma < = 0.73; the lithium-rich manganese-based positive electrode material precursor 1 and the lithium-rich manganese-based positive electrode material precursor 2 have the same components; the D50 of the lithium-rich manganese-based positive electrode material precursor 1 is 10-20 [mu] m, and the D50 of the lithium-rich manganese-based positive electrode material precursor 2 is 3-6 [mu] m; s2, filling the mixture 1 and the mixture 2 with the volume ratio of (40-48): (52-60) from bottom to top, sintering and mixing to obtain the lithium-rich manganese-based positive electrode material, the positive electrode material prepared by the method is uniformly sintered, and has excellent capacity performance, rate capability and cycle life.

Description

Technical Field

[0001] This invention belongs to the field of new energy technology, specifically relating to a lithium-rich manganese-based cathode material, its preparation method, and its application. Background Technology

[0002] Lithium-rich manganese-based cathode materials are considered core materials for next-generation high-energy-density lithium-ion batteries due to their high specific capacity (≥250mAh / g) and low cost.

[0003] However, the industrial preparation of lithium-rich manganese-based cathode materials faces two major challenges: the first is the residual alkali problem. During the sintering process, the lithium salt (LiOH / Li2CO3) is not completely decomposed, and the residual alkaline substances will react with the electrolyte, leading to battery gas production and a decrease in capacity performance, rate performance, and cycle life. The second is the structural sensitivity of lithium-rich manganese-based cathode materials. The material lattice is extremely sensitive to sintering temperature, atmosphere, and mass transfer efficiency. Process fluctuations can easily cause problems such as cation mixing and layered structure collapse, resulting in a decrease in capacity performance, rate performance, and cycle life. Currently, to expand the production scale of lithium-rich manganese-based cathode materials, high-capacity pots (capacity ≥ 600g) are used for packaging. However, during sintering, the high thickness of the reactant buildup leads to a low heat conduction rate, and the actual temperature in the central region of the particles is 50-100℃ lower than the set value, resulting in a decrease in lithium salt decomposition rate. Furthermore, gas diffusion is hindered, preventing the timely release of CO2 and H2O gases produced during the reaction, forming a "gas film barrier" between the powder particles, inhibiting lithium salt decomposition, and causing pore structure collapse. Simultaneously, reducing gases accumulate, oxygen concentration decreases, and some Mn... 4+ Reduced to Mn 3+ This leads to lattice distortion and capacity decay, ultimately resulting in uneven sintering at different locations within the same furnace, which in turn causes a decline in electrical performance. Summary of the Invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects of insufficient capacity performance, rate performance and cycle life of existing lithium-rich manganese-based cathode materials due to uneven sintering, thereby providing a lithium-rich manganese-based cathode material, its preparation method and application.

[0005] Therefore, the present invention provides the following technical solution:

[0006] The first aspect of this invention provides a method for preparing a lithium-rich manganese-based cathode material, wherein the preparation method includes the following steps:

[0007] S1, lithium-rich manganese-based cathode material precursor 1 and lithium-rich manganese-based cathode material precursor 2 are mixed with lithium source to obtain mixture 1 and mixture 2 respectively.

[0008] The general formula of the lithium-rich manganese-based cathode material precursor 1 and the lithium-rich manganese-based cathode material precursor 2 is Niɑ Co β Mn γ (OH)2;0.23≤ɑ≤0.31, 0.04≤β≤0.12, 0.65≤γ≤0.73;

[0009] The lithium-rich manganese-based cathode material precursor 1 and the lithium-rich manganese-based cathode material precursor 2 have the same composition.

[0010] The median particle size of the lithium-rich manganese-based cathode material precursor 1 is 10-20 μm, and the median particle size of the lithium-rich manganese-based cathode material precursor 2 is 3-6 μm.

[0011] S2, mixes 1 and 2 with a volume ratio of (40-48):(52-60) are loaded from bottom to top and sintered to obtain lithium-rich manganese-based cathode material.

[0012] In this invention, mixtures 1 and 2 are filled into a sagger according to a specific volume ratio. The sagger is a conventional sagger in the art with a capacity of ≥600g, which can be 650g. The "from bottom to top" is to distinguish the areas after mixtures 1 and 2 are filled. After filling, mixture 1 is at the bottom of the sagger and mixture 2 is at the top of the sagger.

[0013] In this invention, the lithium-rich manganese-based cathode material precursors 1 and 2 can be purchased or prepared. The preparation method is a conventional co-precipitation method, specifically including the following steps: Nickel source (nickel sulfate), cobalt source (cobalt sulfate), and manganese source (manganese sulfate) are added in stoichiometric ratios and mixed with deionized water to obtain a metal salt solution. The concentration of metal ions in the metal salt solution is 3-3.5 mol / L. Co-precipitation reaction 1 is carried out at a temperature of 80-85℃ using an alkaline solution (NaOH), controlling the pH of the system at 10.5-11, for 14-16 hours to obtain a precipitate. The precipitate is washed and then... The precursor 1 of lithium-rich manganese-based cathode material was obtained by drying at -100℃ for 12-16h. Nickel source (nickel sulfate), cobalt source (cobalt sulfate), and manganese source (manganese sulfate) were added in stoichiometric ratio and mixed with deionized water to obtain a metal salt solution with a metal ion concentration of 2-2.5 mol / L. Co-precipitation reaction 2 was carried out at 55-65℃ using an alkaline solution (NaOH) to control the pH of the system at 10-10.5 for 4-6h to obtain a precipitate. The precipitate was washed and dried at 80-100℃ for 12-16h to obtain lithium-rich manganese-based cathode material precursor 2.

[0014] In this invention, the mixing in step S1 is a conventional mixing method in the art. Typically, without limitation, ball milling can be used to mix for 2-3 hours to make the mixture more uniform.

[0015] According to the present invention, the general formula of the lithium-rich manganese-based cathode material precursor 1 and the lithium-rich manganese-based cathode material precursor 2 is Ni. ɑ Co β Mn γ (OH)2; 0.27≤ɑ≤0.30, 0.08≤β≤0.10, 0.65≤γ≤0.70.

[0016] According to the present invention, the median particle size of the lithium-rich manganese-based cathode material precursor 1 is 12-16 μm, and the median particle size of the lithium-rich manganese-based cathode material precursor 2 is 3.5-5.5 μm.

[0017] According to the present invention, the volume ratio of the mixture 1 and the mixture 2 is (45-48):(55-60).

[0018] According to the present invention, the sintering conditions include: a first sintering at a rate of 2-5°C / min to 500-600°C for 1-5 hours, a second sintering at a rate of 2-5°C / min to 850-900°C for 1-5 hours, and a third sintering at a rate of 1-3°C / min to 920-1000°C for 1-5 hours.

[0019] According to the present invention, the gas atmosphere of the first sintering is nitrogen or an inert gas, and the gas flow rate is 2-5 L / min. This removes air from the system and prevents the material from being oxidized or absorbing moisture at low temperatures. It effectively replaces and removes air from the system, avoiding the oxidation or moisture absorption of the material at low temperatures due to residual air caused by insufficient flow, while also preventing material dispersion or system temperature fluctuations due to excessive flow. The gas atmosphere of the second sintering is oxygen or air, and the gas flow rate is 8-10 L / min. A larger flow rate ensures sufficient oxygen supply and promptly removes byproduct gases generated during lithium source decomposition and solid-phase reaction, thereby promoting lithium source decomposition and solid-phase reaction more efficiently. The gas atmosphere of the third sintering is oxygen or air, with a pressure of -50 to -30 Pa. The third sintering is controlled under negative pressure of -50 to -30 Pa to optimize the crystal structure, reduce impurity phases, and improve material uniformity.

[0020] According to the present invention, the sintering conditions include: a first sintering at a rate of 2-3°C / min to 500-520°C for 2-3 hours, a second sintering at a rate of 2-3°C / min to 850-880°C for 2-3 hours, and a third sintering at a rate of 1-3°C / min to 920-950°C for 3-5 hours.

[0021] A second aspect of this invention protects a lithium-rich manganese-based cathode material prepared by the aforementioned preparation method.

[0022] According to the present invention, the general formula of the lithium-rich manganese-based cathode material is Li x Ni a Co b Mn c O2, where 1.00≤x≤1.20, 0.150≤a≤0.250, 0.030≤b≤0.100, and 0.520≤c≤0.680.

[0023] According to the present invention, the specific surface area of ​​the lithium-rich manganese-based cathode material is 1.1-1.5 m². 2 / g.

[0024] According to the present invention, the residual alkali content on the surface of the lithium-rich manganese-based cathode material is 0.3-0.6%.

[0025] According to the present invention, the general formula of the lithium-rich manganese-based cathode material is Li x Ni a Co b Mn c O2, where 1.10≤x≤1.20, 0.210≤a≤0.240, 0.050≤b≤0.070, and 0.520≤c≤0.600.

[0026] According to the present invention, the specific surface area of ​​the lithium-rich manganese-based cathode material is 1.3-1.5 m². 2 / g.

[0027] According to the present invention, the residual alkali content on the surface of the lithium-rich manganese-based cathode material is 0.3-0.4%.

[0028] A third aspect of this invention protects a secondary battery, wherein the secondary battery comprises the aforementioned lithium-rich manganese-based cathode material.

[0029] The technical solution of this invention has the following advantages:

[0030] 1. This invention provides a method for preparing a lithium-rich manganese-based cathode material, wherein the preparation method includes the following steps: S1, mixing lithium-rich manganese-based cathode material precursor 1 and lithium-rich manganese-based cathode material precursor 2 with lithium sources to obtain mixture 1 and mixture 2; the general formula of lithium-rich manganese-based cathode material precursor 1 and lithium-rich manganese-based cathode material precursor 2 is Ni ɑ Co β Mn γ(OH)2; 0.23≤α≤0.31, 0.04≤β≤0.12, 0.65≤γ≤0.73; The lithium-rich manganese-based cathode material precursor 1 and lithium-rich manganese-based cathode material precursor 2 have the same composition; The median particle size of the lithium-rich manganese-based cathode material precursor 1 is 10-20 μm, and the median particle size of the lithium-rich manganese-based cathode material precursor 2 is 3-6 μm; S2, Mixture 1 and Mixture 2 with a volume ratio of (40-48):(52-60) The process involves bottom-up filling and sintering to obtain lithium-rich manganese-based cathode materials. The specific ratios of nickel (Ni), cobalt (Co), and manganese (Mn) directly affect the material's structure and electrochemical properties. A specific amount of Co doping forms strong covalent bonds (Co-O bond energy of 384 kJ / mol), effectively limiting abnormal grain growth during high-temperature sintering and preventing grain coarsening. The contribution of d-orbital electrons from a specific amount of Co increases the material's electronic conductivity and reduces local Joule heating. This process avoids sintering agglomeration caused by local overheating; a specific amount of Co doping can reduce the activation energy of residual alkali decomposition, reduce the generation of residual gases (such as CO2 and H2O), and prevent gas retention leading to pore collapse; a specific amount of Co doping improves the thermal conductivity of the material, and when the crucible capacity is ≥600g, it still has good thermal conductivity, reducing densification caused by overburning in the edge area and ensuring more balanced heat transfer inside the material; Mix 1 and Mix 2 are mixed in a specific volume ratio, and the large-sized Mix 1 particles have large pores, providing an escape path for the gases (CO2 and H2O) generated in the reaction, preventing the formation of gas film barriers due to gas retention; the small-sized Mix 2 particles are densely packed, but because they are located on the top layer, the gas can be freely discharged into the furnace cavity without blocking the upward flow of gas from the bottom layer, which can optimize heat transfer and gas diffusion, avoid "gas film barriers" and local overheating, and improve sintering uniformity, thereby making the prepared lithium-rich manganese-based cathode material have excellent capacity performance, rate performance and cycle life.

[0031] 2. The present invention further defines the composition of the precursor general formula, the median particle size, and the volume ratio of mixture 1 and 2, which can further improve the capacity performance, rate performance and cycle life of the cathode material.

[0032] 3. In this invention, the first sintering stage involves heating to 500-600℃ at a rate of 2-5℃ / min and holding for 1-5 hours. This allows volatiles such as moisture and residual organic matter in the precursor to escape smoothly, while simultaneously allowing the lithium source to initially react with the precursor. This avoids localized overheating and thermal stress caused by rapid heating, or the formation of porosity defects due to the rapid escape of volatiles. The second sintering stage continues to heat to 850-900℃ at the same rate and holds. This temperature range matches the thermodynamic requirements of lithium source decomposition and solid-phase reaction. Sufficient holding time ensures uniform diffusion of lithium elements and the formation of stable intermediates with transition metal ions, avoiding component segregation due to incomplete reaction. The third stage involves heating to 920-1000℃ at a slower rate of 1-3℃ / min and holding. The high-temperature environment combined with slow heating provides kinetic conditions for the orderly growth of the crystal structure. Finally, through the synergy and homogenization of reactions in each stage, the material forms a crystal structure with complete structure and uniform composition. The first sintering process uses nitrogen or an inert gas atmosphere with a flow rate of 2-5 L / min to remove air from the system and prevent the material from being oxidized or absorbing moisture at low temperatures. This effectively replaces and removes air from the system, preventing residual air from causing oxidation or moisture absorption at low temperatures, while also preventing material scattering or temperature fluctuations due to excessive flow. The second sintering process uses oxygen or air atmosphere with a flow rate of 8-10 L / min. The larger flow rate ensures a sufficient oxygen supply and promptly removes byproduct gases generated during lithium source decomposition and solid-state reaction, thereby promoting lithium source decomposition and solid-state reaction more efficiently. The third sintering process uses oxygen or air atmosphere at a pressure of -50 to -30 Pa to optimize the crystal structure, reduce impurity phases, and improve material uniformity.

[0033] 4. This invention provides a lithium-rich manganese-based cathode material, wherein the general formula of the lithium-rich manganese-based cathode material is Li x Ni a Co b Mn c O2, wherein 1.00≤x≤1.20, 0.15≤a≤0.25, 0.03≤b≤0.10, 0.52≤c≤0.68; the specific surface area of ​​the lithium-rich manganese-based cathode material is 1.1-1.5m². 2 / g; the residual alkali content on the surface of the lithium-rich manganese-based cathode material is 0.3-0.6%; the lithium-rich manganese-based cathode material of the present invention has excellent capacity performance, rate performance and cycle life; wherein, Co 3+ ionic radius and and Significant differences were observed at specific levels of Co. 3+The oxygen framework in the stable layered structure reduces the formation of disordered phases (such as spinel phase) on the surface by suppressing the release of O2 during charging and discharging; the specific surface area can optimize the lithium-ion transport path and reduce the side reaction interface; the low residual alkali content will not block the surface channels of the layered structure, nor will it lead to an increase in impedance, thus ensuring the excellent electrical performance of the cathode material.

[0034] 5. The present invention further defines the general formula composition, specific surface area and residual alkali content of lithium-rich manganese-based cathode materials, which can further improve the capacity performance, rate performance and cycle life of cathode materials. Detailed Implementation

[0035] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0036] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0037] The lithium-rich manganese-based cathode material precursors 1 and 2 with different median particle sizes in the examples and comparative examples were all purchased from GEM Co., Ltd.

[0038] Both the examples and the comparative examples were sintered in a 650g crucible.

[0039] Example 1

[0040] This embodiment provides a lithium-rich manganese-based cathode material, the preparation method of which includes the following steps:

[0041] Lithium-rich manganese-based cathode material precursor 1, namely Ni 0.27 Co 0.08 Mn 0.65 (OH)2, with a median particle size of 15 μm;

[0042] Lithium-rich manganese-based cathode material precursor 2, namely Ni 0.27 Co 0.08 Mn 0.65 (OH)2, with a median particle size of 4 μm;

[0043] S1, lithium-rich manganese-based cathode material precursor 1 and lithium-rich manganese-based cathode material precursor 2 are ball-milled with lithium carbonate at a stoichiometric ratio for 2 hours to obtain mixture 1 and mixture 2.

[0044] S2, mixtures 1 and 2 (volume ratio 44:55) are loaded from bottom to top for sintering. The sintering conditions include: first sintering under nitrogen protection at a flow rate of 2 L / min, heating to 500℃ at a rate of 2℃ / min for 2 hours; second sintering under oxygen protection at a flow rate of 10 L / min, heating to 850℃ at a rate of 5℃ / min for 3 hours; and third sintering under oxygen protection at a pressure of -30 Pa, heating to 920℃ at a rate of 1℃ / min for 3 hours. The sintered products are then mixed to obtain a lithium-rich manganese-based cathode material, i.e., Li. 1.2 Ni 0.216 Co 0.064 Mn 0.520 O2.

[0045] Example 2

[0046] This embodiment provides a lithium-rich manganese-based cathode material, the preparation method of which includes the following steps:

[0047] Lithium-rich manganese-based cathode material precursor 1, namely Ni 0.23 Co 0.12 Mn 0.65 (OH)2, with a median particle size of 10 μm;

[0048] Lithium-rich manganese-based cathode material precursor 2, namely Ni 0.23 Co 0.12 Mn 0.65 (OH)2, with a median particle size of 6 μm;

[0049] S1, lithium-rich manganese-based cathode material precursor 1 and lithium-rich manganese-based cathode material precursor 2 are ball-milled with lithium hydroxide in stoichiometric ratio for 3 hours to obtain mixture 1 and mixture 2.

[0050] S2, mixtures 1 and 2 (volume ratio 40:60) are loaded from bottom to top for sintering. The sintering conditions include: first sintering under nitrogen protection at a flow rate of 5 L / min, heating to 600℃ at a rate of 2℃ / min for 2 hours; second sintering under oxygen protection at a flow rate of 8 L / min, heating to 850℃ at a rate of 5℃ / min for 3 hours; and third sintering under oxygen protection at a pressure of -40 Pa, heating to 1000℃ at a rate of 3℃ / min for 3 hours. The sintered products are then mixed to obtain a lithium-rich manganese-based cathode material, i.e., Li. 1.2 Ni 0.184 Co 0.096 Mn 0.520 O2.

[0051] Example 3

[0052] This embodiment provides a lithium-rich manganese-based cathode material, the preparation method of which includes the following steps:

[0053] Lithium-rich manganese-based cathode material precursor 1, namely Ni 0.31 Co 0.04 Mn 0.65 (OH)2, with a median particle size of 20 μm;

[0054] Lithium-rich manganese-based cathode material precursor 2, namely Ni 0.31 Co 0.04 Mn 0.65 (OH)2, with a median particle size of 3 μm;

[0055] S1, lithium-rich manganese-based cathode material precursor 1 and lithium-rich manganese-based cathode material precursor 2 are ball-milled with lithium carbonate at a stoichiometric ratio for 2.5 h to obtain mixture 1 and mixture 2.

[0056] S2, mixtures 1 and 2 (volume ratio 48:52) are loaded from bottom to top and sintered. The sintering conditions include: a first sintering under nitrogen protection at a flow rate of 3 L / min, heating to 500°C at a rate of 5°C / min for 4 hours; a second sintering under oxygen protection at a flow rate of 10 L / min, heating to 900°C at a rate of 2°C / min for 1 hour; and a third sintering under oxygen protection at a pressure of -50 Pa, heating to 920°C at a rate of 1°C / min for 2 hours. The sintered products are then mixed to obtain a lithium-rich manganese-based cathode material, i.e., Li. 1.0 Ni 0.248 Co 0.032 Mn 0.520 O2.

[0057] Example 4

[0058] This embodiment provides a lithium-rich manganese-based cathode material, the preparation method of which includes the following steps:

[0059] Lithium-rich manganese-based cathode material precursor 1, namely Ni 0.31 Co 0.04 Mn 0.65 (OH)2; the median particle size is the same as in Example 1;

[0060] Lithium-rich manganese-based cathode material precursor 2, namely Ni 0.31 Co 0.04 Mn 0.65 (OH)2; the median particle size is the same as in Example 1;

[0061] Steps S1 and S2 are performed in accordance with the method of Example 1. After sintering, the products are mixed to obtain a lithium-rich manganese-based cathode material, namely Li. 1.2 Ni 0.248 Co 0.032 Mn 0.520 O2.

[0062] Example 5

[0063] This embodiment provides a lithium-rich manganese-based cathode material, the preparation method of which includes the following steps:

[0064] Lithium-rich manganese-based cathode material precursor 1, namely Ni 0.23 Co 0.12 Mn 0.65 (OH)2; the median particle size is the same as in Example 1;

[0065] Lithium-rich manganese-based cathode material precursor 2, namely Ni 0.23 Co 0.12 Mn 0.65 (OH)2; the median particle size is the same as in Example 1;

[0066] Steps S1 and S2 are performed in accordance with the method of Example 1. After sintering, the products are mixed to obtain a lithium-rich manganese-based cathode material, namely Li. 1.2 Ni 0.184 Co 0.096 Mn 0.520 O2.

[0067] Example 6

[0068] This embodiment provides a lithium-rich manganese-based cathode material, the preparation method of which includes the following steps:

[0069] Lithium-rich manganese-based cathode material precursor 1, namely Ni 0.27 Co 0.08 Mn 0.65 (OH)2, with a median particle size of 18 μm;

[0070] Lithium-rich manganese-based cathode material precursor 2, namely Ni 0.27 Co 0.08 Mn 0.65 (OH)2, with a median particle size of 6 μm;

[0071] Steps S1 and S2 are performed in accordance with the method of Example 1. After sintering, the products are mixed to obtain a lithium-rich manganese-based cathode material, namely Li. 1.2 Ni 0.216 Co 0.064 Mn 0.520 O2.

[0072] Example 7

[0073] This embodiment provides a lithium-rich manganese-based cathode material, the preparation method of which includes the following steps:

[0074] The lithium-rich manganese-based cathode material precursors 1 and 2 are the same as those in Example 1;

[0075] S1, according to the method of Example 1;

[0076] S2, in accordance with Example 1, except that the volume ratio of mixture 1 to mixture 2 is 40:60.

[0077] Example 8

[0078] This embodiment provides a lithium-rich manganese-based cathode material, the preparation method of which includes the following steps:

[0079] The lithium-rich manganese-based cathode material precursors 1 and 2 are the same as those in Example 1;

[0080] S1, according to the method of Example 1;

[0081] S2, mixtures 1 and 2 (volume ratio 44:55) are loaded from bottom to top for sintering. The sintering conditions include: first sintering under nitrogen protection at a flow rate of 2 L / min, heating to 600℃ at a rate of 2℃ / min for 5 hours; second sintering under oxygen protection at a flow rate of 10 L / min, heating to 850℃ at a rate of 2℃ / min for 1 hour; and third sintering under oxygen protection at a pressure of -30 Pa, heating to 980℃ at a rate of 1℃ / min for 3 hours. This yields a lithium-rich manganese-based cathode material, i.e., Li. 1.2 Ni 0.216 Co 0.064 Mn 0.520 O2.

[0082] Comparative Example 1

[0083] This comparative example provides a lithium-rich manganese-based cathode material, the preparation method of which includes the following steps:

[0084] Lithium-rich manganese-based cathode material precursor 1, namely Ni 0.33 Co 0.02 Mn 0.65 (OH)2; the median particle size is the same as in Example 1;

[0085] Lithium-rich manganese-based cathode material precursor 2, namely Ni 0.33 Co 0.02 Mn 0.65 (OH)2; the median particle size is the same as in Example 1;

[0086] Steps S1 and S2 are performed in accordance with the method of Example 8. After sintering, the products are mixed to obtain a lithium-rich manganese-based cathode material, namely Li. 1.2 Ni 0.264 Co 0.016 Mn 0.52 O2.

[0087] Comparative Example 2

[0088] This comparative example provides a lithium-rich manganese-based cathode material, the preparation method of which includes the following steps:

[0089] Lithium-rich manganese-based cathode material precursor 1, namely Ni 0.23 Co 0.18 Mn 0.65 (OH)2; the median particle size is the same as in Example 1;

[0090] Lithium-rich manganese-based cathode material precursor 2, namely Ni 0.23 Co 0.18 Mn 0.65 (OH)2; the median particle size is the same as in Example 1;

[0091] Steps S1 and S2 are performed in accordance with the method of Example 8. After sintering, the products are mixed to obtain a lithium-rich manganese-based cathode material, namely Li. 1.2 Ni 0.184 Co 0.144 Mn 0.520 O2.

[0092] Comparative Example 3

[0093] This comparative example provides a lithium-rich manganese-based cathode material, the preparation method of which includes the following steps:

[0094] The lithium-rich manganese-based cathode material precursors 1 and 2 are the same as those in Example 1;

[0095] Lithium-rich manganese-based cathode material precursor 1 and precursor 2 were mixed with lithium carbonate in a stoichiometric ratio and then sintered. The sintering conditions included: a first sintering under nitrogen protection at a flow rate of 2 L / min, heating to 500℃ at a rate of 2℃ / min for 2 hours; a second sintering under oxygen protection at a flow rate of 10 L / min, heating to 850℃ at a rate of 5℃ / min for 3 hours; and a third sintering under oxygen protection at a pressure of -30 Pa, heating to 920℃ at a rate of 1℃ / min for 3 hours, yielding the lithium-rich manganese-based cathode material, i.e., Li. 1.2 Ni 0.216 Co 0.064 Mn 0.520 O2.

[0096] Comparative Example 4

[0097] This comparative example provides a lithium-rich manganese-based cathode material, the preparation method of which includes the following steps:

[0098] The lithium-rich manganese-based cathode material precursors 1 and 2 are the same as those in Example 1;

[0099] S1, according to the method of Example 1;

[0100] S2, mixtures 2 and 1 (volume ratio 44:55) are loaded from bottom to top for sintering. The sintering conditions include: first sintering under nitrogen protection at a flow rate of 2 L / min, heating to 500℃ at a rate of 2℃ / min for 2 hours; second sintering under oxygen protection at a flow rate of 10 L / min, heating to 850℃ at a rate of 5℃ / min for 3 hours; and third sintering under oxygen protection at a pressure of -30 Pa, heating to 920℃ at a rate of 1℃ / min for 3 hours. The sintered products are then mixed to obtain a lithium-rich manganese-based cathode material, i.e., Li. 1.2 Ni 0.216 Co 0.064 Mn 0.520 O2.

[0101] Comparative Example 5

[0102] This comparative example provides a lithium-rich manganese-based cathode material, the preparation method of which includes the following steps:

[0103] Lithium-rich manganese-based cathode material precursor 1, namely Ni 0.27 Co 0.08 Mn 0.65 (OH)2, with a median particle size of 80 μm;

[0104] Lithium-rich manganese-based cathode material precursor 2, namely Ni 0.27 Co 0.08 Mn 0.65 (OH)2, with a median particle size of 7 μm;

[0105] Steps S1 and S2 are performed in accordance with the method of Example 1. After sintering, the products are mixed to obtain a lithium-rich manganese-based cathode material, namely Li. 1.2 Ni 0.216 Co 0.064 Mn 0.520 O2.

[0106] Test case

[0107] The specific surface area of ​​lithium-rich manganese-based cathode materials was measured using the BET method.

[0108] The residual alkali content on the surface of lithium-rich manganese-based cathode materials was tested using an acid-base titration method: 0.5g of the lithium-rich manganese-based cathode materials from the examples and comparative examples were weighed and placed in an Erlenmeyer flask. Deionized water was added and stirred for 30 minutes to fully dissolve the residual alkali. After standing, the supernatant was collected, filtered to remove solid particles, and the test solution containing residual alkali was obtained. 2-3 drops of phenolphthalein indicator were added to the test solution, and titration was performed with 0.1mol / L hydrochloric acid solution until the solution changed from red to colorless. The volume of hydrochloric acid consumed was recorded as V1. 2-3 drops of methyl orange indicator were added to the above solution, and titration was continued with a 0.1mol / L hydrochloric acid solution. Titrate with 0.1 mol / L hydrochloric acid solution until the solution changes from yellow to orange, and record the volume of hydrochloric acid consumed as V2. Perform three tests and take the average value. The LiOH content w1 is (0.1 × V1 × M1) / (m × 1000) × 100%, where M1 is the relative molar mass of LiOH and m is the mass of the sample solution; the Li2CO3 content w2 is (0.1 × V2 × M2) / (m × 1000) × 100%, where M2 is the relative molar mass of Li2CO3 and m is the mass of the sample solution; the total residual alkali mass is taken as the mass of Li2O. 总 = 0.625 × w1 + 0.405 × w2;

[0109] The specific test results are shown in Table 1;

[0110] Table 1

[0111]

[0112]

[0113] Battery fabrication: The lithium-rich manganese-based cathode material and Super... prepared in the examples and comparative examples P and PVDF are mixed in a mass ratio of 8:1:1 to obtain a positive electrode mixture. The positive electrode mixture is then mixed with N-methylpyrrolidone (NMP) to form a slurry. The ratio of the positive electrode mixture to NMP is 2:1 g / mL. This slurry is coated onto aluminum foil and dried to form a positive electrode sheet. Graphite, binder (LA133), and carbon nanotubes (CNTs) are mixed in a mass ratio of 92:6:2 to obtain a negative electrode mixture. The ratio of the negative electrode mixture to NMP is 2:1 g / mL. This mixture is coated onto copper foil and dried to form a negative electrode sheet. The electrolyte is a 1 mol / L solution of ethylene carbonate (EC) and dimethyl carbonate (DMC) in LiPF6, with a volume ratio of EC to DMC of 1:1. The positive electrode sheet, separator (PE / PP composite membrane), negative electrode sheet, and electrolyte are assembled into a 2025 coin cell in an Ar gas glove box with a water and oxygen content of less than 5 ppm.

[0114] The Blue Electric series battery testing system was used to test the battery by charging it to 4.8V at a constant current rate of 0.1C to obtain the initial charge capacity and initial charge specific capacity; then discharging it to 2.0V at a constant current rate of 0.1C to obtain the initial charge specific capacity and initial discharge specific capacity.

[0115] At 25°C, the battery is charged to 4.8V at a constant current rate of 1C, and then discharged to 2.0V at a constant current rate of 1C for 500 cycles. The capacity retention rate at 1C is (discharge specific capacity in the 500th cycle / discharge specific capacity in the 1st cycle) × 100%.

[0116] At 25°C, the battery is charged to 4.8V at a constant current rate of 5C, and then discharged to 2.0V at a constant current rate of 5C for 500 cycles. The capacity retention rate at 5C is (discharge specific capacity in the 500th cycle / discharge specific capacity in the 1st cycle) × 100%.

[0117] The specific test results are shown in Table 2;

[0118] Table 2

[0119]

[0120] A comparison of Example 8 and Comparative Example 2 shows that, as shown in Table 1, Comparative Example 2 performs better in terms of residual alkali content and specific surface area. However, Table 2 shows that the electrical performance of Comparative Example 2 is worse than that of Example 8. The inventors speculate that this is because excessive Co content will destroy the stability of the layered structure of the material, causing cation mixing and resulting in a decrease in electrochemical performance.

[0121] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a lithium-rich manganese-based cathode material, characterized in that, The preparation method includes the following steps: S1, lithium-rich manganese-based cathode material precursor 1 and lithium-rich manganese-based cathode material precursor 2 are mixed with lithium source to obtain mixture 1 and mixture 2 respectively. The general formula of the lithium-rich manganese-based cathode material precursor 1 and the lithium-rich manganese-based cathode material precursor 2 is Ni ɑ Co β Mn γ (OH)2;0.23≤ɑ≤0.31, 0.04≤β≤0.12, 0.65≤γ≤0.73; The lithium-rich manganese-based cathode material precursor 1 and the lithium-rich manganese-based cathode material precursor 2 have the same composition. The median particle size of the lithium-rich manganese-based cathode material precursor 1 is 10-20 μm, and the median particle size of the lithium-rich manganese-based cathode material precursor 2 is 3-6 μm. S2, mixes 1 and 2 with a volume ratio of (40-48):(52-60) are loaded from bottom to top and sintered to obtain lithium-rich manganese-based cathode material.

2. The preparation method according to claim 1, characterized in that, The general formula of the lithium-rich manganese-based cathode material precursor 1 and the lithium-rich manganese-based cathode material precursor 2 is Ni ɑ Co β Mn γ (OH)2; 0.27≤ɑ≤0.30, 0.08≤β≤0.10, 0.65≤γ≤0.

70.

3. The preparation method according to claim 1 or 2, characterized in that, The median particle size of the lithium-rich manganese-based cathode material precursor 1 is 12-16 μm, and the median particle size of the lithium-rich manganese-based cathode material precursor 2 is 3.5-5.5 μm.

4. The preparation method according to any one of claims 1-3, characterized in that, The volume ratio of the mixture 1 and the mixture 2 is (45-48):(55-60).

5. The preparation method according to any one of claims 1-4, characterized in that, The sintering conditions include: first sintering at a rate of 2-5℃ / min to 500-600℃ for 1-5 hours, second sintering at a rate of 2-5℃ / min to 850-900℃ for 1-5 hours, and third sintering at a rate of 1-3℃ / min to 920-1000℃ for 1-5 hours; And / or, the gas atmosphere of the first sintering is nitrogen or an inert gas; And / or, the gas atmosphere of the second sintering is oxygen or air; And / or, the gas atmosphere of the third sintering is oxygen or air, with a pressure of -50 to -30 Pa.

6. The preparation method according to claim 5, characterized in that, The sintering conditions include: a first sintering at a rate of 2-3℃ / min to 500-520℃ for 2-3 hours, a second sintering at a rate of 2-3℃ / min to 850-880℃ for 2-3 hours, and a third sintering at a rate of 1-3℃ / min to 920-950℃ for 3-5 hours.

7. A lithium-rich manganese-based cathode material prepared by the preparation method according to any one of claims 1-6.

8. The lithium-rich manganese-based cathode material according to claim 7, characterized in that, The general formula of the lithium-rich manganese-based cathode material is Li x Ni a Co b Mn c O2, where 1.00≤x≤1.20, 0.150≤a≤0.250, 0.030≤b≤0.100, 0.520≤c≤0.680; And / or, the specific surface area of ​​the lithium-rich manganese-based cathode material is 1.1-1.5 m². 2 / g; And / or, the residual alkali content on the surface of the lithium-rich manganese-based cathode material is 0.3-0.6%.

9. The lithium-rich manganese-based cathode material according to claim 8, characterized in that, The general formula of the lithium-rich manganese-based cathode material is Li x Ni a Co b Mn c O2, where 1.10≤x≤1.20, 0.210≤a≤0.240, 0.050≤b≤0.070, 0.520≤c≤0.600; And / or, the specific surface area of ​​the lithium-rich manganese-based cathode material is 1.3-1.5 m². 2 / g; And / or, the residual alkali content on the surface of the lithium-rich manganese-based cathode material is 0.3-0.4%.

10. A secondary battery, characterized in that, The secondary battery comprises the lithium-rich manganese-based cathode material as described in any one of claims 7-9.

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