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

Abstract

The application provides a lithium-rich manganese-based positive electrode material and a preparation method and battery thereof, the lithium-rich manganese-based positive electrode material is fused by primary particles to form secondary particles, wherein recesses exist, the depth H of the recesses satisfies: the proportion of the secondary particles with 0nm The application controls the size of the recesses of the secondary particles accurately, suppresses the interface side reaction, effectively improves the stability and conductive performance of the material, reduces the resistance, and improves the performance of the material under large-rate charging.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and relates to a lithium-rich manganese-based cathode material, its preparation method, and a battery. Background Technology

[0002] As a key component of lithium-ion batteries, cathode materials play a crucial role in the battery's energy density, cycle life, and safety. Currently, lithium-rich manganese-based cathode materials are strong contenders for next-generation high-performance lithium-ion battery cathode materials due to their advantages such as high specific capacity, good thermal stability and cycle performance, and environmental friendliness.

[0003] However, existing lithium-rich manganese-based cathode materials still face several unresolved issues. First, their traditional polycrystalline aggregate morphology easily leads to particle cracking, causing material performance degradation. Second, due to the small particle size and numerous structural defects in primary particles, structural collapse easily occurs under high-voltage charge-discharge conditions, and secondary particles struggle to encapsulate these fine particles, making it difficult to suppress interfacial side reactions. Furthermore, lithium-rich manganese-based cathode materials exhibit low conductivity during high-rate charging, leading to increased resistance. Combined with concentration polarization and other adverse factors, this results in severe degradation of their rate performance. In addition, current technologies lack precise size control for both primary and secondary particles, hindering further optimization of material performance.

[0004] To address these issues, existing technologies disclose single-crystal or near-single-crystal lithium-rich manganese-based cathode materials. Single-crystal lithium-rich manganese-based cathode materials, due to their dispersed micron-sized primary particles, can effectively reduce the specific surface area of ​​the material, inhibit electrolyte penetration, and increase compaction density, thereby improving the material's volumetric energy density. However, the synthesis process of single-crystal materials is complex to control, and due to the high bond energy of the Mn-O bonds, grain boundary defects are easily generated during the synthesis process.

[0005] Based on the above research, there is a need to develop a high-performance and structurally stable lithium-rich manganese-based cathode material. Summary of the Invention

[0006] The purpose of this invention is to provide a lithium-rich manganese-based cathode material, its preparation method, and a battery. The lithium-rich manganese-based cathode material suppresses interfacial side reactions by precisely controlling the concave size of the secondary particles, thereby forming a dense network structure between the primary and secondary particles. This effectively improves the stability and conductivity of the material, reduces resistance, and improves the material's performance under high-rate charging.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a lithium-rich manganese-based cathode material, wherein the secondary particles of the lithium-rich manganese-based cathode material are formed by fusing primary particles.

[0009] The secondary particles of the lithium-rich manganese-based cathode material are spherical with depressions. The depth H of the depressions satisfies the following conditions: the proportion of secondary particles with a depth of 0 nm < H < 5 nm is less than 30% of the total number of secondary particles; the proportion of secondary particles with a depth of H between 5 nm and 200 nm is 50%-80% of the total number of secondary particles; and the proportion of secondary particles with a depth of H > 200 nm is less than 30% of the total number of secondary particles.

[0010] The depth H of the depression refers to the shortest distance from the fusion point of two adjacent primary particles to the common tangent surface of two adjacent primary particles in the secondary particles.

[0011] The width W of the depression satisfies the following conditions: the proportion of secondary particles with W < W < 10 nm in the total number of secondary particles is less than 30%; the proportion of secondary particles with W between 10 nm and 500 nm in the total number of secondary particles is 50%-80%; and the proportion of secondary particles with W > 500 nm in the total number of secondary particles is less than 30%.

[0012] The width W of the depression refers to the distance between the centers of two adjacent primary particles in the secondary particle.

[0013] The secondary particles of the lithium-rich manganese-based cathode material of this invention are formed by the fusion of primary particles, resulting in a spherical morphology. Since the primary particles are not completely fused into regular spheres, there are depressions in the secondary particles. These depressions are localized low-lying areas formed on or around the sintering neck. In this invention, the depressions are directly connected to the sintering neck, with a continuous transition between the boundary and the particle surface without obvious breaks. By controlling the distribution of the depth H and width W of the depressions, this invention suppresses interfacial side reactions, resulting in a dense network structure between the primary and secondary particles. This effectively improves the stability and conductivity of the material, reduces resistance, and improves the performance of the material under high-rate charging.

[0014] Specifically, the present invention achieves a specific proportion of secondary particles with different H values, enabling the material to possess both good stability and low resistance. If the proportion of secondary particles with 0nm < H < 5nm is too high, the material resistance will increase, conductivity will decrease, and specific capacity will decrease. However, if the proportion is 0%, it will be detrimental to the stability of the material. If the proportion of secondary particles with H between 5nm and 200nm is too low or too high, the material will exhibit poor stability or high resistivity, thereby affecting cycle performance or high-rate charge-discharge performance. If the proportion of secondary particles with H > 200nm is too high, the material stability will be poor. However, if the proportion is 0%, it will affect high-rate charge-discharge performance.

[0015] This invention achieves a specific proportion of secondary particles with different W values, which can suppress interfacial side reactions while maintaining low resistivity of the material. If the proportion of secondary particles with 0nm < W < 10nm is too high, it can easily cause interfacial side reactions and affect battery performance. However, if the proportion is 0%, the resistivity is high, and the specific capacity of the material will decrease. If the proportion of secondary particles with W between 10nm and 500nm is too low or too high, the material will exhibit poor stability or low specific capacity. If the proportion of secondary particles with W > 500nm is too high, the resistivity is high, but if the proportion is 0%, interfacial side reactions cannot be suppressed.

[0016] The proportion of secondary particles with a wavelength of 0nm < H < 5nm (e.g., 1nm, 2nm, 3nm, or 4nm) in the total number of secondary particles is <30% (preferably <30%, >0%), for example, 28%, 25%, 20%, 15%, 10%, 5%, 1%, or 0%. The proportion of secondary particles with a wavelength of H between 5nm and 200nm (e.g., 5nm, 20nm, 50nm, 100nm, 150nm, or 200nm) in the total number of secondary particles is 50%-80%, for example, 50%, 60%, 70%, or 80%. The proportion of secondary particles with a wavelength of H > 200nm (e.g., 250nm, 300nm, 350nm, 400nm, or 450nm) in the total number of secondary particles is <30% (preferably <30%, >0%), for example, 28%, 25%, 20%, 15%, 10%, 5%, 1%, or 0%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] The width W of the recess described in this invention satisfies the following: 0nm < W < 10nm (e.g., it can be 2nm, 4nm, 6nm, 8nm, or 9nm) of secondary particles accounts for < 30% (preferably < 30%, > 0%) of the total number of secondary particles, for example, it can be 28%, 25%, 20%, 15%, 10%, 5%, 1%, or 0%; and W is the percentage of secondary particles with a width W between 10nm and 500nm (e.g., it can be 10nm, 50nm, 100nm, 250nm, or 500nm) of the total number of secondary particles. The proportion is 50%-80%, for example, it can be 50%, 60%, 70% or 80%. The proportion of secondary particles with W>500nm (for example, it can be 520nm, 550nm, 600nm, 650nm, 700nm or 750nm) in the total number of secondary particles is <30% (preferably <30%, >0%), for example, it can be 28%, 25%, 20%, 15%, 10%, 5%, 1% or 0%, but is not limited to the listed values. Other unlisted values ​​within the value range are also applicable.

[0018] The testing method for H and W described in this invention is as follows: Take 0.1g of lithium-rich manganese-based cathode material sample, coat it on conductive adhesive, and attach it to the SEM sample stage for testing. The magnification is 20.0k. Select a field of view containing no less than 200 complete primary particles (for samples with excessively large or small primary particle sizes, the magnification can be appropriately reduced or increased). Measure all complete W and H within this field of view.

[0019] Preferably, the primary particle size d of the lithium-rich manganese-based cathode material satisfies the following: the proportion of primary particles with d > 1 μm (e.g., 1.5 μm, 1.75 μm, 2 μm, 2.25 μm, 2.5 μm, 2.75 μm, or 3 μm) in the total number of primary particles is less than 30% (preferably < 30%, > 0%), for example, 28%, 25%, 20%, 15%, 10%, 5%, 1%, or 0%; and d is 0.1 μm-1 μm (e.g., 0.1 μm, 0.3 μm, ...). The proportion of primary particles (0.5μm, 0.7μm, 0.9μm or 1μm) in the total number of primary particles is 50%-90%, for example, it can be 50%, 60%, 70%, 80% or 90%. The proportion of primary particles with d < 0.1μm in the total number of primary particles is less than 30% (preferably <30%, >0%), for example, it can be 28%, 25%, 20%, 15%, 10%, 5%, 1% or 0%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] This invention improves the structural stability of the material by controlling the primary particle size distribution of the lithium-rich manganese-based cathode material, preventing the structural collapse of the primary particles under high-voltage charge and discharge.

[0021] The size d of the primary particle described in this invention is equivalent to the diameter of the primary particle when it is a complete sphere.

[0022] The method for testing the primary particle size of the lithium-rich manganese-based cathode material described in this invention is as follows: Image analysis software (such as ImageJ or Nano Measurer) is used to statistically analyze ≥200 primary particles in a SEM image, and the equivalent circle diameter (area equivalence method) is calculated using the formula: d = 2 (A / π). 1 / 2 , where A is the projected area of ​​a single primary particle (equivalent to a complete sphere).

[0023] Preferably, the secondary particles of the lithium-rich manganese-based cathode material have a particle size D0 > 0.3 μm, for example, 0.4 μm, 0.6 μm, 0.8 μm or 1 μm, but are not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0024] Preferably, the particle size D10 of the secondary particles of the lithium-rich manganese-based cathode material is 1.5μm-2.5μm, for example, it can be 1.5μm, 1.7μm, 1.9μm, 2.1μm, 2.3μm or 2.5μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, the particle size D50 of the secondary particles of the lithium-rich manganese-based cathode material is 2.5μm-4.5μm, for example, it can be 2.5μm, 3μm, 3.5μm, 4μm or 4.5μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] Preferably, the particle size D90 of the secondary particles of the lithium-rich manganese-based cathode material is 5.5μm-7.5μm, for example, it can be 5.5μm, 6μm, 6.5μm, 7μm or 7.5μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0027] Preferably, the particle size D100 of the secondary particles of the lithium-rich manganese-based cathode material is less than 15 μm, for example, it can be 14 μm, 12 μm, 10 μm or 8 μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] This invention improves the stability and cycle performance of traditional polycrystalline aggregate morphology materials by controlling the particle size distribution of secondary particles, thereby addressing the problem of microcracks easily formed in the particles.

[0029] Preferably, the particle size D50 of the precursor of the lithium-rich manganese-based cathode material is 2μm-4μm, for example, it can be 2μm, 2.5μm, 3μm, 3.5μm or 4μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] Preferably, the particle size D100 of the precursor of the lithium-rich manganese-based cathode material is <20 μm, for example, it can be 1 μm, 5 μm, 10 μm, 15 μm or 20 μm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0031] Preferably, the TAP (tap density) of the precursor of the lithium-rich manganese-based cathode material is 1 g / cm³. 3 -1.8g / cm 3 For example, it could be 1g / cm 3 1.2g / cm 3 1.4g / cm 3 1.6g / cm 3 Or 1.8g / cm 3However, this does not limit the listed values; other unlisted values ​​within the range are also applicable.

[0032] Preferably, the BET (specific surface area) of the precursor of the lithium-rich manganese-based cathode material is 5m². 3 / g-40m 3 / g, for example, could be 5m 3 / g, 10m 3 / g、20m 3 / g、30m 3 / g or 40m 3 / g, but not limited to the listed values, other unlisted values ​​within the range also apply.

[0033] The BET of the precursor described in this invention affects the sintering temperature and time of the cathode material, as well as the heating rate and atmosphere during sintering. For a high BET precursor, a lower sintering temperature is preferable, and vice versa.

[0034] Preferably, the general chemical formula of the lithium-rich manganese-based cathode material is xLi2MnO3·(1-x)LiTMO2, where 0 < x < 1, for example, it can be 0.1, 0.3, 0.5, 0.7 or 0.9, and TM includes any one or at least a combination of two of Ni, Co or Mn.

[0035] Secondly, the present invention provides a method for preparing a lithium-rich manganese-based cathode material as described in the first aspect, the method comprising the following steps:

[0036] A lithium-rich manganese-based cathode material precursor and a lithium source are mixed and sintered once to obtain a sintered material. The temperature of the first sintering is 850℃-1000℃, for example, it can be 850℃, 900℃, 950℃ or 1000℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] The sintering material is subjected to secondary sintering to obtain the lithium-rich manganese-based cathode material.

[0038] The present invention uses high-temperature forming during a single sintering process, which essentially determines the morphology of the material and promotes the satisfaction of specific conditions for the depth H and width W of the recess.

[0039] The second firing process described in this invention can also be coated with a coating agent as needed.

[0040] Preferably, the sintering time is 8h-20h, for example, it can be 8h, 10h, 12h, 14h, 16h, 18h or 20h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0041] Preferably, the atmosphere for the first sintering is oxygen.

[0042] Preferably, the heating rate of the first sintering is 1℃ / min to 3℃ / min, for example, it can be 1℃ / min, 1.5℃ / min, 2℃ / min, 2.5℃ / min or 3℃ / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] Preferably, the temperature of the secondary sintering is 250℃-700℃, for example, it can be 250℃, 300℃, 400℃, 500℃, 600℃ or 700℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0044] Preferably, the secondary sintering time is 2h-12h, for example, it can be 2h, 6h, 10h or 12h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0045] Preferably, the atmosphere for the secondary sintering is air or oxygen.

[0046] Preferably, the heating rate of the secondary sintering is 1℃ / min to 5℃ / min, for example, it can be 1℃ / min, 2℃ / min, 3℃ / min, 4℃ / min or 5℃ / min, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0047] Thirdly, the present invention provides a battery comprising the lithium-rich manganese-based cathode material as described in the first aspect.

[0048] Compared with the prior art, the present invention has the following beneficial effects:

[0049] This invention suppresses interfacial side reactions and improves the electrochemical performance of the material by controlling the distribution of the depth H and width W of the depression. This results in a dense network structure between the primary and secondary particles, which effectively improves the stability and conductivity of the material, reduces resistance, and improves the material's performance under high-rate charging. Attached Figure Description

[0050] Figure 1 This is a schematic diagram of the secondary particles of the lithium-rich manganese-based cathode material described in Embodiment 1 of the present invention projected onto a horizontal plane.

[0051] Figure 2 This is a SEM image of the lithium-rich manganese-based cathode material described in Example 1 of the present invention. Detailed Implementation

[0052] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0053] Example 1

[0054] This embodiment provides a lithium-rich manganese-based cathode material, the chemical formula of which is 0.5Li₂MnO₃·0.5LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2; the secondary particles of the lithium-rich manganese-based cathode material are formed by the fusion of primary particles; the secondary particles of the lithium-rich manganese-based cathode material are spherical with depressions, such as... Figure 1 As shown, the depth H of the depression refers to the shortest distance from the fusion position of two adjacent primary particles to the common tangent surface of two adjacent primary particles in the secondary particle, and the width W of the depression refers to the distance between the centers of two adjacent primary particles in the secondary particle.

[0055] The depth H of the depression satisfies the following conditions: secondary particles with a depth of 0nm < H < 5nm account for 20% of the total number of secondary particles; secondary particles with a depth of H of 5nm-200nm account for 65% of the total number of secondary particles; and secondary particles with a depth of H > 200nm account for 15% of the total number of secondary particles.

[0056] The width W of the depression satisfies the following conditions: secondary particles with a width of 0nm < W < 10nm account for 20% of the total number of secondary particles; secondary particles with a width of W between 10nm and 500nm account for 60% of the total number of secondary particles; and secondary particles with a width of W > 500nm account for 20% of the total number of secondary particles.

[0057] The size d of the primary particles in the lithium-rich manganese-based cathode material is equivalent to the diameter of the primary particle when it is a complete sphere. d satisfies the following conditions: primary particles with d > 1 μm account for 15% of the total number of primary particles; primary particles with d = 0.1 μm - 1 μm account for 70% of the total number of primary particles; and primary particles with d < 0.1 μm account for 15% of the total number of primary particles.

[0058] The secondary particles of the lithium-rich manganese-based cathode material have a particle size D0 of 0.5 μm, a particle size D10 of 2 μm, a particle size D50 of 3.5 μm, a particle size D90 of 6.5 μm, and a particle size D100 of 10 μm.

[0059] The precursor of the lithium-rich manganese-based cathode material has a particle size D50 of 3 μm, a particle size D100 of 10 μm, and a TAP of 1.5 g / cm³. 3 BET is 20m 3 / g;

[0060] The preparation method of the lithium-rich manganese-based cathode material includes the following steps:

[0061] The precursor of the lithium-rich manganese-based cathode material and lithium carbonate were mixed according to the formula. Then, under an oxygen atmosphere, the mixture was sintered at 900°C for 15 hours at a heating rate of 2°C / min to obtain a sintered material. This sintered material was then sintered a second time under an oxygen atmosphere at 500°C for 7 hours at a heating rate of 3°C / min to obtain the lithium-rich manganese-based cathode material. The SEM image of the lithium-rich manganese-based cathode material is shown below. Figure 2 As shown.

[0062] Example 2

[0063] This embodiment provides a lithium-rich manganese-based cathode material, the chemical formula of which is 0.3Li₂MnO₃·0.7LiNi. 0.5 Mn 0.5 O2; The secondary particles of the lithium-rich manganese-based cathode material are formed by the fusion of primary particles; The secondary particles of the lithium-rich manganese-based cathode material are spherical with depressions. The depth H of the depression refers to the shortest distance from the fusion position of two adjacent primary particles to the common tangent of the secondary particles, and the width W of the depression refers to the distance between the centers of two adjacent primary particles.

[0064] The depth H of the depression satisfies the following conditions: secondary particles with a depth of 0 nm < H < 5 nm account for 10% of the total number of secondary particles; secondary particles with a depth of H between 5 nm and 200 nm account for 80% of the total number of secondary particles; and secondary particles with a depth of H > 200 nm account for 10% of the total number of secondary particles.

[0065] The width W of the depression satisfies the following conditions: secondary particles with a width W of 0nm < W < 10nm account for 12% of the total number of secondary particles; secondary particles with a width W of 10nm-500nm account for 78% of the total number of secondary particles; and secondary particles with a width W > 500nm account for 10% of the total number of secondary particles.

[0066] The size d of the primary particles in the lithium-rich manganese-based cathode material is equivalent to the diameter of the primary particle when it is a complete sphere. d satisfies the following conditions: primary particles with d > 1 μm account for 7% of the total number of primary particles; primary particles with d = 0.1 μm - 1 μm account for 88% of the total number of primary particles; and primary particles with d < 0.1 μm account for 5% of the total number of primary particles.

[0067] The secondary particles of the lithium-rich manganese-based cathode material have a particle size D0 of 0.4 μm, a particle size D10 of 1.5 μm, a particle size D50 of 2.5 μm, a particle size D90 of 5.5 μm, and a particle size D100 of 8 μm.

[0068] The precursor of the lithium-rich manganese-based cathode material has a particle size D50 of 2 μm, a particle size D100 of 7 μm, and a TAP of 1.8 g / cm³. 3 BET is 5m 3 / g;

[0069] The preparation method of the lithium-rich manganese-based cathode material includes the following steps:

[0070] The precursor of the lithium-rich manganese-based cathode material and lithium carbonate are mixed according to the formula. Then, under an oxygen atmosphere, the mixture is sintered at a temperature of 950°C for 12 hours at a heating rate of 1°C / min to obtain a sintered material. The sintered material is then sintered a second time at a temperature of 700°C for 2 hours under an air atmosphere at a heating rate of 5°C / min to obtain the lithium-rich manganese-based cathode material.

[0071] Example 3

[0072] This embodiment provides a lithium-rich manganese-based cathode material, the chemical formula of which is 0.4Li₂MnO₃·0.6LiNi. 1 / 3 Co 1 / 3 Mn 1 / 3 O2; The secondary particles of the lithium-rich manganese-based cathode material are formed by the fusion of primary particles; The secondary particles of the lithium-rich manganese-based cathode material are spherical with depressions. The depth H of the depression refers to the shortest distance from the fusion position of two adjacent primary particles to the common tangent of the secondary particles, and the width W of the depression refers to the distance between the centers of two adjacent primary particles.

[0073] The depth H of the depression satisfies the following conditions: secondary particles with a depth of 0nm < H < 5nm account for 25% of the total number of secondary particles; secondary particles with a depth of H between 5nm and 200nm account for 50% of the total number of secondary particles; and secondary particles with a depth of H > 200nm account for 25% of the total number of secondary particles.

[0074] The width W of the depression satisfies the following conditions: secondary particles with a width W of 0nm < W < 10nm account for 25% of the total number of secondary particles; secondary particles with a width W of 10nm-500nm account for 50% of the total number of secondary particles; and secondary particles with a width W > 500nm account for 25% of the total number of secondary particles.

[0075] The size d of the primary particles in the lithium-rich manganese-based cathode material is equivalent to the diameter of the primary particle when it is a complete sphere. d satisfies the following conditions: primary particles with d > 1 μm account for 28% of the total number of primary particles; primary particles with d between 0.1 μm and 1 μm account for 50% of the total number of primary particles; and primary particles with d < 0.1 μm account for 22% of the total number of primary particles.

[0076] The secondary particles of the lithium-rich manganese-based cathode material have a particle size D0 of 1 μm, a particle size D10 of 2.5 μm, a particle size D50 of 4.5 μm, a particle size D90 of 7.5 μm, and a particle size D100 of 12 μm.

[0077] The precursor of the lithium-rich manganese-based cathode material has a particle size D50 of 4 μm, a particle size D100 of 10 μm, and a TAP of 1 g / cm³. 3 BET is 40m 3 / g;

[0078] The preparation method of the lithium-rich manganese-based cathode material includes the following steps:

[0079] The precursor of the lithium-rich manganese-based cathode material and lithium carbonate are mixed according to the formula. Then, under an oxygen atmosphere, the mixture is sintered at a temperature of 850°C for 20 hours at a heating rate of 3°C / min to obtain a sintered material. The sintered material is then sintered a second time under an air atmosphere at a temperature of 250°C for 12 hours at a heating rate of 1°C / min to obtain the lithium-rich manganese-based cathode material.

[0080] Example 4

[0081] This embodiment provides a lithium-rich manganese-based cathode material. Except that the depth H of the depression satisfies the following conditions: the proportion of secondary particles with a depth H of 0nm < H < 5nm is 0% of the total number of secondary particles, the proportion of secondary particles with a depth H of 5nm-200nm is 80% of the total number of secondary particles, and the proportion of secondary particles with a depth H > 200nm is 20% of the total number of secondary particles, the rest is the same as in Embodiment 1.

[0082] The preparation method of the lithium-rich manganese-based cathode material is the same as that in Example 1, except that the heating rate of the first sintering is 0.5℃ / min.

[0083] Example 5

[0084] This embodiment provides a lithium-rich manganese-based cathode material. Except that the depth H of the depression satisfies the following conditions: the proportion of secondary particles with a depth of 0nm < H < 5nm is 20% of the total number of secondary particles, the proportion of secondary particles with a depth of H of 5nm-200nm is 80% of the total number of secondary particles, and the proportion of secondary particles with a depth of H > 200nm is 0% of the total number of secondary particles, the rest of the lithium-rich manganese-based cathode material is the same as that in Embodiment 1.

[0085] The preparation method of the lithium-rich manganese-based cathode material is the same as that in Example 1, except that the heating rate of the first sintering is 5℃ / min.

[0086] Example 6

[0087] This embodiment provides a lithium-rich manganese-based cathode material. Except that the width W of the depression satisfies the following conditions: the proportion of secondary particles with W = 0nm < W < 10nm is 0% of the total number of secondary particles, the proportion of secondary particles with W = 10nm-500nm is 80% of the total number of secondary particles, and the proportion of secondary particles with W > 500nm is 20% of the total number of secondary particles, the rest is the same as in Embodiment 1.

[0088] The preparation method of the lithium-rich manganese-based cathode material is the same as that in Example 1, except that the secondary sintering time is 14 hours.

[0089] Example 7

[0090] This embodiment provides a lithium-rich manganese-based cathode material. Except that the width W of the depression satisfies the following conditions: the proportion of secondary particles with W = 0nm < W < 10nm is 20% of the total number of secondary particles, the proportion of secondary particles with W = 10nm-500nm is 80% of the total number of secondary particles, and the proportion of secondary particles with W > 500nm is 0% of the total number of secondary particles, the rest is the same as in Embodiment 1.

[0091] The preparation method of the lithium-rich manganese-based cathode material is the same as that in Example 1, except that the heating rate of the secondary sintering is 8℃ / min.

[0092] Example 8

[0093] This embodiment provides a lithium-rich manganese-based cathode material. Except for the following conditions: the proportion of primary particles with d>1μm is 30% of the total number of primary particles, the proportion of primary particles with d=0.1μm-1μm is 40% of the total number of primary particles, and the proportion of primary particles with d<0.1μm is 30% of the total number of primary particles, and the particle size of secondary particles is adapted to change, the rest of the lithium-rich manganese-based cathode material is the same as that in Example 1.

[0094] The preparation method of the lithium-rich manganese-based cathode material is the same as that in Example 1, except that the atmosphere for the first sintering is air.

[0095] Example 9

[0096] This embodiment provides a lithium-rich manganese-based cathode material. Except for the following conditions: the proportion of primary particles with d>1μm is 2% of the total number of primary particles, the proportion of primary particles with d=0.1μm-1μm is 95% of the total number of primary particles, and the proportion of primary particles with d<0.1μm is 3% of the total number of primary particles, and the particle size of secondary particles is adapted to change, the rest of the lithium-rich manganese-based cathode material is the same as that in Embodiment 1.

[0097] The preparation method of the lithium-rich manganese-based cathode material is the same as that in Example 1, except that the atmosphere for the first sintering is nitrogen.

[0098] Comparative Example 1

[0099] This comparative example provides a lithium-rich manganese-based cathode material. Except that the depth H of the depression satisfies the following conditions: 30% of the secondary particles are 0nm < H < 5nm, 40% of the secondary particles are 5nm-200nm, and 30% of the secondary particles are H > 200nm, the rest of the lithium-rich manganese-based cathode material is the same as that in Example 1.

[0100] The preparation method of the lithium-rich manganese-based cathode material is the same as that in Example 1, except that the sintering temperature is 750°C.

[0101] Comparative Example 2

[0102] This comparative example provides a lithium-rich manganese-based cathode material. Except that the depth H of the depression satisfies the following conditions: secondary particles with a depth of 0nm < H < 5nm account for 5% of the total number of secondary particles; secondary particles with a depth of H of 5nm-200nm account for 90% of the total number of secondary particles; and secondary particles with a depth of H > 200nm account for 5% of the total number of secondary particles, the rest of the lithium-rich manganese-based cathode material is the same as that in Example 1.

[0103] The preparation method of the lithium-rich manganese-based cathode material is the same as that in Example 1, except that the sintering time is 25 hours.

[0104] Comparative Example 3

[0105] This comparative example provides a lithium-rich manganese-based cathode material. Except that the width W of the depression satisfies the following conditions: 30% of the secondary particles are 0nm < W < 10nm, 40% of the secondary particles are 10nm-500nm, and 30% of the secondary particles are W > 500nm, the rest of the lithium-rich manganese-based cathode material is the same as that in Example 1.

[0106] The preparation method of the lithium-rich manganese-based cathode material is the same as that in Example 1, except that the atmosphere for the secondary sintering is nitrogen.

[0107] Comparative Example 4

[0108] This comparative example provides a lithium-rich manganese-based cathode material. Except that the width W of the depression satisfies the following conditions: secondary particles with a width of 0nm < W < 10nm account for 5% of the total number of secondary particles, secondary particles with a width of W between 10nm and 500nm account for 90% of the total number of secondary particles, and secondary particles with a width of W > 500nm account for 5% of the total number of secondary particles, the rest of the lithium-rich manganese-based cathode material is the same as that in Example 1.

[0109] The preparation method of the lithium-rich manganese-based cathode material is the same as that in Example 1, except that the secondary sintering temperature is 800℃.

[0110] The lithium-rich manganese-based cathode materials obtained in the above examples and comparative examples were used to prepare lithium-ion batteries. The negative electrode in these lithium-ion batteries is lithium metal, the separator is a three-layer composite separator of PP, PE, and PP, and the electrolyte is HR8825 electrolyte. The electrochemical performance of the obtained lithium-ion batteries was tested. The capacity and cycle test conditions were 2.0-4.8V, 100 charge-discharge cycles at 0.1C / 0.1C, and a test temperature of 25℃. The rate test conditions were 2.0-4.8V, one charge-discharge cycle at 0.1C / 0.1C, one charge-discharge cycle at 1C / 1C, one charge-discharge cycle at 3C / 3C, and one charge-discharge cycle at 5C / 5C, and a test temperature of 25℃. The test results are shown in Table 1 below.

[0111] Table 1

[0112]

[0113] As can be seen from Table 1 above:

[0114] As shown in Examples 1 and Comparative Examples 1-4, the depth H and width W of the depression in the secondary particles of the present invention meet specific conditions, suppressing interfacial side reactions and forming a dense network structure between the primary and secondary particles, thereby improving the electrochemical performance of the battery. As shown in Examples 1 and Examples 4-5, the depth H of the depression in the present invention is preferably within three distribution ranges. As shown in Examples 1 and Examples 6-7, the width W of the depression in the present invention is also preferably within three distribution ranges, which is beneficial to improving the stability of the secondary particles and improving the electrochemical performance of the battery. As shown in Examples 1 and Examples 8-9, the present invention precisely controls the size distribution of the primary particles, which can further optimize the performance of the material and thus improve the electrochemical performance of the battery.

[0115] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A lithium-rich manganese-based cathode material, characterized in that, The secondary particles of the lithium-rich manganese-based cathode material are formed by fusing primary particles. The secondary particles of the lithium-rich manganese-based cathode material are spherical with depressions. The depth H of the depressions satisfies the following conditions: the proportion of secondary particles with a depth of 0 nm < H < 5 nm is less than 30% of the total number of secondary particles; the proportion of secondary particles with a depth of H between 5 nm and 200 nm is 50%-80% of the total number of secondary particles; and the proportion of secondary particles with a depth of H > 200 nm is less than 30% of the total number of secondary particles. The depth H of the depression refers to the shortest distance from the fusion point of two adjacent primary particles to the common tangent surface of two adjacent primary particles in the secondary particles. The width W of the depression satisfies the following conditions: the proportion of secondary particles with W < W < 10 nm in the total number of secondary particles is less than 30%; the proportion of secondary particles with W between 10 nm and 500 nm in the total number of secondary particles is 50%-80%; and the proportion of secondary particles with W > 500 nm in the total number of secondary particles is less than 30%. The width W of the depression refers to the distance between the centers of two adjacent primary particles in the secondary particle.

2. The lithium-rich manganese-based cathode material according to claim 1, characterized in that, The primary particle size d of the lithium-rich manganese-based cathode material satisfies the following conditions: the proportion of primary particles with d > 1 μm is less than 30% of the total number of primary particles; the proportion of primary particles with d = 0.1 μm - 1 μm is 50% - 90% of the total number of primary particles; and the proportion of primary particles with d < 0.1 μm is less than 30% of the total number of primary particles. The size d of the primary particle is equivalent to the diameter of the primary particle when it is a complete sphere.

3. The lithium-rich manganese-based cathode material according to claim 1 or 2, characterized in that, The secondary particles of the lithium-rich manganese-based cathode material have a particle size D0 > 0.3 μm; Preferably, the secondary particles of the lithium-rich manganese-based cathode material have a particle size D10 of 1.5 μm-2.5 μm; Preferably, the secondary particles of the lithium-rich manganese-based cathode material have a particle size D50 of 2.5 μm-4.5 μm; Preferably, the secondary particles of the lithium-rich manganese-based cathode material have a particle size D90 of 5.5 μm-7.5 μm; Preferably, the secondary particles of the lithium-rich manganese-based cathode material have a particle size D100 < 15 μm.

4. The lithium-rich manganese-based cathode material according to claim 1 or 2, characterized in that, The precursor of the lithium-rich manganese-based cathode material has a particle size D50 of 2μm-4μm; Preferably, the particle size D100 of the precursor of the lithium-rich manganese-based cathode material is <20 μm; Preferably, the TAP of the precursor of the lithium-rich manganese-based cathode material is 1 g / cm³. 3 -1.8g / cm 3 ; Preferably, the BET of the precursor of the lithium-rich manganese-based cathode material is 5m. 3 / g-40m 3 / g.

5. The lithium-rich manganese-based cathode material according to claim 1 or 2, characterized in that, The general chemical formula of the lithium-rich manganese-based cathode material is xLi2MnO3·(1-x)LiTMO2, where 0 < x < 1, and TM includes any one or at least a combination of two of Ni, Co, or Mn.

6. A method for preparing a lithium-rich manganese-based cathode material as described in any one of claims 1-5, characterized in that, The preparation method includes the following steps: A lithium-rich manganese-based cathode material precursor and a lithium source are mixed and sintered once to obtain a sintered material, wherein the temperature of the first sintering is 850℃-1000℃. The sintering material is subjected to secondary sintering to obtain the lithium-rich manganese-based cathode material.

7. The preparation method according to claim 6, characterized in that, The sintering time for the first sintering is 8-20 hours. Preferably, the atmosphere for the first sintering is oxygen; Preferably, the heating rate of the first sintering is 1℃ / min to 3℃ / min.

8. The preparation method according to claim 6 or 7, characterized in that, The temperature for the secondary sintering is 250℃-700℃; Preferably, the secondary sintering time is 2h-12h.

9. The preparation method according to claim 6 or 7, characterized in that, The atmosphere for the secondary sintering is air or oxygen; Preferably, the heating rate of the secondary sintering is 1℃ / min to 5℃ / min.

10. A battery, characterized in that, The battery comprises the lithium-rich manganese-based cathode material as described in any one of claims 1-5.

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