Lithium-rich manganese-based positive electrode material, preparation method thereof, positive plate and battery

Abstract

The invention provides a lithium-rich manganese-based positive electrode material and a preparation method thereof, a positive plate and a battery. The lithium-rich manganese-based positive electrode material comprises a lithium-rich manganese-based core material and a coating layer coating the lithium-rich manganese-based core material, the alkali metal layer of the lithium-rich manganese-based core material at least comprises Mg element, and the coating layer comprises lithium fluoride. The lithium-rich manganese-based positive electrode material disclosed by the invention has high capacity, high structural stability and excellent interface durability, and can meet the performance requirements of a high-energy-density battery under complex working conditions.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to a lithium-rich manganese-based cathode material, its preparation method, cathode sheet, and battery. Background Technology

[0002] Lithium-rich manganese-based cathode materials (Li-rich layered oxide cathode materials) are one of the core components of high-energy-density lithium-ion batteries, widely used in new energy vehicles, energy storage systems, and consumer electronics. This cathode material is renowned in the industry for its high energy density, but its performance is limited to 250-300 mAh / g. -1 Behind the high capacity lies unacceptable voltage and capacity decay, making it unsuitable for industrial applications. Simultaneously, the high voltage employed introduces significant side reactions at the interface, leading to gas generation and deterioration in storage performance within the battery system. Furthermore, the anion buildup caused by shallow discharge SOC gradually accumulates material stress, resulting in rapid performance degradation. These results indicate that high capacity (>250 mAh g) is... -1 There are several technical bottlenecks in applying lithium-rich cathodes to liquid battery systems, which need to be overcome one by one.

[0003] In the short term, a feasible solution is to find a balance between capacity utilization and structural stability, and successfully introduce it into industrial applications. This would attract more academic and industrial research and development, ultimately driving the realization of high-capacity systems. Therefore, appropriately adjusting the operating voltage window to 4.4~4.5V will maintain its capacity utilization at 210~230mAhg. -1 This is a highly feasible industrialization path in the short term. Under these conditions, ultra-high capacity (>250mAh g) -1 The series of problems caused by the high capacity have been alleviated or partially resolved. Even so, the voltage window of 4.4~4.5V is still not low. The more serious interfacial side reactions and structural collapse caused by anion redox still need to be addressed. In particular, under high temperature conditions, the improved kinetics lead to higher capacity than at room temperature, while anion oxidation leads to structural rearrangement and exacerbates interfacial side reactions, resulting in a significant deterioration in cycling performance compared to room temperature.

[0004] Therefore, there is an urgent need to develop a lithium-rich manganese-based cathode material that combines high capacity, high structural stability, and excellent interface durability to meet the performance requirements of high-energy-density batteries under complex operating conditions. Summary of the Invention

[0005] The lithium-rich manganese-based cathode material, its preparation method, cathode sheet, and battery provided in this application have the advantages of high capacity, high structural stability, and excellent interface durability, which can meet the performance requirements of high energy density batteries under complex operating conditions.

[0006] In a first aspect, the present application provides a lithium-rich manganese-based cathode material, comprising a lithium-rich manganese-based core material and a coating layer coated on the lithium-rich manganese-based core material; the alkali metal layer of the lithium-rich manganese-based core material at least includes Mg element, and the coating layer includes lithium fluoride.

[0007] In a possible implementation manner, the lithium fluoride contains a (200) crystal plane; the included angle between the lattice fringes of the (200) crystal plane of the lithium fluoride and the lattice fringes of the (003) crystal plane of the lithium-rich manganese-based core material is less than or equal to 10°.

[0008] In a possible implementation manner, the d(Li-O-Li) spacing of the lithium-rich manganese-based cathode material is 2.590 - 2.600 Å.

[0009] In a possible implementation manner, the chemical formula of the lithium-rich manganese-based cathode material includes Li 1+ x Ni a Co b Mn c M d Mg e O y F z R h , where a + b + c + d + e = 1.0, 0.1 ≤ a < 0.5, 0 ≤ b ≤ 0.15, 0.5 ≤ c ≤ 0.7, d ≤ 0.2, 0.10 ≤ x ≤ 0.5, 0 < e ≤ 0.015, 2.13 ≤ y ≤ 2.50, 0.006 ≤ z ≤ 0.03, 0.001 ≤ h ≤ 0.02; 1.95 + x ≤ y + z + h ≤ 2.05 + x, z + h ≤ 0.2y, M includes one or more of Al, P, Ca, Ti, Cr, Fe, Cu, Zn, Sr, Se, Y, Zr, Si, Nb, Mo, Sb, Sn, Te, Ba, Cs, Ta, W, La, Ce, Sm and Gd, and R includes one or more of S, Cl, B and C.

[0010] In a possible implementation manner, the thickness of the coating layer is 2 nm - 20 nm.

[0011] In a possible implementation manner, the thickness of the coating layer is 2 nm - 14 nm.

[0012] In a possible implementation manner, the specific surface area of the lithium-rich manganese-based cathode material is 0.3 - 3.0 m 2 / g.

[0013] In a possible implementation manner, the specific surface area of the lithium-rich manganese-based cathode material is 1.4 - 1.8 m 2 / g.

[0014] In one possible implementation, the D50 of the lithium-rich manganese-based cathode material is 1.0 μm ≤ D50 ≤ 15.0 μm.

[0015] In one possible implementation, the D50 of the lithium-rich manganese-based cathode material is 6.5 μm ≤ D50 ≤ 12.2 μm.

[0016] In one possible implementation, the coating layer further includes at least one element selected from La, Zr, Ba, and Cs.

[0017] Secondly, this application provides a method for preparing a lithium-rich manganese-based cathode material, the method comprising the following steps:

[0018] A metal salt solution, a precipitant, and a complexing agent are mixed and reacted to obtain a hydroxide precursor; the hydroxide precursor and a lithium source are mixed and subjected to a first sintering to obtain a cathode material intermediate;

[0019] The cathode material intermediate and fluoride are mixed and subjected to a second sintering process to obtain the lithium-rich manganese-based cathode material, wherein the fluoride includes at least magnesium fluoride.

[0020] In one possible implementation, a hydroxide precursor, a lithium source, and a modifying additive are mixed and subjected to a first sintering. The modifying additive comprises a compound containing an element M, which includes one or more of Al, P, Ca, Ti, Cr, Fe, Cu, Zn, Sr, Se, Y, Zr, Si, Nb, Mo, Sb, Sn, Te, Ba, Cs, Ta, W, La, Ce, Sm, and Gd.

[0021] In one possible implementation, the fluoride further includes fluoride I, which includes at least one of LaF3, ZrF4, BaF2, and CsF.

[0022] In one possible implementation, the second sintering time is 2-5 hours.

[0023] In one possible implementation, the heating rate of the second sintering is greater than or equal to 10°C / min, or the heating rate of the second sintering is 10-15°C / min.

[0024] In one possible implementation, the temperature of the second sintering is 800~900°C.

[0025] Thirdly, this application provides a positive electrode sheet comprising the aforementioned lithium-rich manganese-based positive electrode material.

[0026] Fourthly, this application provides a battery including the aforementioned positive electrode.

[0027] The lithium-rich manganese-based cathode material, its preparation method, cathode sheet, and battery provided in this application improve lithium-ion conductivity, structural stability under deep delithiation conditions, and Mn metal migration energy by doping Mg ions into the alkali metal layer of the lithium-rich manganese-based core material, thereby inhibiting spinel phase formation. The LiF coating layer prevents direct contact between the cathode material and the electrolyte, thus avoiding the formation of low-conductivity byproduct layers resulting from direct contact, improving cathode interface stability, reducing electrolyte erosion of the surface, inhibiting metal dissolution, improving surface structural stability, and simultaneously increasing the lithium-ion migration coefficient. Attached Figure Description

[0028] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and, together with the description, serve to explain the principles of this application.

[0029] Figure 1 The XRD pattern of the lithium-rich manganese-based cathode material obtained in Example 1 of this application;

[0030] Figure 2 The XRD pattern of the lithium-rich manganese-based cathode material obtained in Comparative Example 1 provided in this application;

[0031] Figure 3 HRTEM image of the lithium-rich manganese-based cathode material obtained in Example 1 of this application;

[0032] Figure 4 HRTEM image of the lithium-rich manganese-based cathode material obtained in Comparative Example 1 provided in this application;

[0033] Figure 5 HRTEM image of the lithium-rich manganese-based cathode material obtained in Example 1 of this application after high-temperature cycling;

[0034] Figure 6 HRTEM image of the lithium-rich manganese-based cathode material obtained in Comparative Example 1 provided in this application after high-temperature cycling;

[0035] Figure 7 EPMA image of the lithium-rich manganese-based cathode material obtained in Example 1 of this application at 6000x magnification;

[0036] Figure 8 Provided for this application Figure 7 The corresponding point scan detection results for Mg and F elements;

[0037] Figure 9 EPMA image of the cross-section of the lithium-rich manganese-based cathode material obtained in Example 1 of this application;

[0038] Figure 10 Provided for this application Figure 9 The corresponding point scan detection results for Mg and F elements;

[0039] Figure 11 EPMA image of the lithium-rich manganese-based cathode material obtained in Example 1 of this application at 4000x magnification;

[0040] Figure 12 Provided for this application Figure 11 The corresponding elemental distribution diagram of Mg;

[0041] Figure 13 Provided for this application Figure 11 The corresponding element distribution diagram of element F;

[0042] Figure 14 EPMA image of the lithium-rich manganese-based cathode material obtained in Example 5 of this application at 4000x magnification;

[0043] Figure 15 Provided for this application Figure 14 The corresponding elemental distribution diagram of Mg;

[0044] Figure 16 Provided for this application Figure 14 The corresponding element distribution diagram of element F;

[0045] Figure 17 A schematic diagram of the lattice fringe angle between the LiF coating (200) crystal plane of the lithium-rich manganese-based cathode material obtained in Example 1 of this application and the (003) crystal plane of the core lithium-rich cathode material;

[0046] Figure 18 GITT test diagrams of batteries prepared using lithium-rich manganese-based cathode materials obtained in Example 1 and Comparative Example 1, provided for this application.

[0047] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0048] To enable those skilled in the art to better understand the present invention, this application will be further described in detail below. The specific embodiments listed below are merely descriptions of the principles and features of the present invention, and the examples are only for explaining the invention and are not intended to limit its scope. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. When the following description relates to the accompanying drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements.

[0049] When lithium-rich manganese-based cathode materials are used in the medium voltage window of 4.4~4.5V, they suffer from serious interfacial side reactions and structural collapse caused by anion redox, resulting in a significant deterioration in cycle performance.

[0050] Based on the above problems, this invention optimizes lithium-rich manganese-based cathode materials by focusing on the surface structure and coating of the cathode material.

[0051] In a first aspect, this application provides a lithium-rich manganese-based cathode material, comprising a lithium-rich manganese-based core material and a coating layer covering the lithium-rich manganese-based core material; the alkali metal layer of the lithium-rich manganese-based core material includes at least Mg element, and the coating layer includes lithium fluoride.

[0052] First, the surface region of existing lithium-rich manganese-based cathode materials is susceptible to electrolyte corrosion, causing its structure to transform from layered to spinel, and then to a rock salt phase. This application proposes doping the alkali metal layer of the lithium-rich manganese-based core material with Mg ions, which can increase the interlayer spacing of the alkali metal layers, improve lithium-ion conductivity, enhance structural stability under deep delithiation conditions, increase Mn metal migration energy, and suppress spinel phase formation. Second, this application involves in-situ coating of the lithium-rich manganese-based core material with the fast ion conductor LiF. LiF has been proven to be one of the components of the cathode-electrolyte interface layer. Increasing the LiF concentration on the surface of the material helps stabilize the LiF saturation at the cathode-electrolyte interface, thereby stabilizing the formation of this side reaction and preventing its iterative reaction. The LiF coating layer of this application can avoid direct contact between the cathode material and the electrolyte, thus avoiding the formation of a low-conductivity side reaction product layer caused by direct contact between the cathode material and the electrolyte, improving the stability of the cathode interface, reducing electrolyte erosion of the surface layer, inhibiting metal dissolution, improving surface structural stability, and simultaneously increasing the lithium-ion migration coefficient. Secondly, when the amount of Mg doping is too high, it will affect lithium-ion transport. However, the LiF coating layer involved in this application can offset the decrease in lithium-ion transport efficiency caused by the high concentration of Mg ions in the cathode, so that the material can achieve its objective capacity.

[0053] Furthermore, if only bulk Mg exists in the alkali metal layer without surface LiF coating, the large-area direct contact between the cathode material and the electrolyte will still lead to certain interfacial side reactions. Significant side reactions and structural degradation will still exist in the surface region of the material. The accumulation of these interfacial side reactions will increase the internal stress of the cathode material, cause secondary spheres to break, expose fresh interfaces, and trigger new chain reactions. On the other hand, if only a LiF coating layer exists without Mg doping of the alkali metal layer of the lithium-rich manganese-based core material, localized areas of the bulk phase will rapidly evolve into spinel and rock salt phases, increasing internal stress, causing secondary spheres to break, and exposing fresh interfaces, thus significantly reducing the effectiveness of the LiF coating.

[0054] Therefore, the Mg doping and LiF coating of the alkali metal layer have a synergistic effect, significantly improving the improvement effect compared to single modification. Thus, the Mg doping and LiF coating of the alkali metal layer in this application are both indispensable as part of the overall scheme.

[0055] Furthermore, under high-temperature conditions, compared to ternary cathode materials, lithium-rich manganese-based cathode materials typically exhibit more severe interfacial side reactions and poorer kinetic performance. Therefore, the solution proposed in this application significantly improves the stability of cathode materials under high-temperature conditions. Specifically, the amount of lithium delithiation is less at room temperature than at high temperature, resulting in relatively stable bulk structure when applied at room temperature (4.4–4.5V). Compared to high temperatures, Mg doping at room temperature has a relatively weaker effect on improving cycle stability. At high temperatures, under the same voltage, the degree of lithium delithiation is higher, forming more non-bonded O and reducing the migration energy of Mn. At this point, the LiF layer interface can maximize the protection of interface stability, thereby avoiding the chain reaction of interface degradation and bulk degradation, and improving the stability of the material at room temperature. When used under high-temperature conditions, the bulk structure stability of the material decreases. At this time, Mg ions begin to inhibit Mn migration, combining with the LiF interface protection to mutually promote and jointly maintain the stability of the overall material performance.

[0056] In one possible implementation, lithium fluoride contains a (200) crystal plane; the angle between the lattice stripes of the (200) crystal plane of lithium fluoride and the lattice stripes of the (003) crystal plane of the lithium-rich manganese-based core material is less than or equal to 10°.

[0057] This application limits the angle between the lattice fringes of the LiF coating layer (200) crystal plane and the lithium-rich manganese-based core material (003) crystal plane to ≤10°, so as to achieve the same crystal growth direction of the LiF coating layer (200) crystal plane and the lithium-rich manganese-based core material (003). This makes the direction of the lithium ion transport layer of the coating layer and the lithium-rich manganese-based core material basically the same, which can further improve the lithium ion transport efficiency.

[0058] It is understandable that the angle between the lattice fringes of the (200) crystal plane of lithium fluoride and the lattice fringes of the (003) crystal plane of the lithium-rich manganese-based core material is less than or equal to 10°, for example: 0°, 1°, 2°, 3°, 4°, 5°, 6°, 7°, 8°, 9°, 10° or the range composed of any two of them, not limited to the listed values, and other values not listed within this range or the range composed of any two other unlisted values are equally applicable.

[0059] In a possible implementation, the d(Li-O-Li) spacing of the lithium-rich manganese-based cathode material is 2.590 - 2.600 Å.

[0060] The alkali metal layer spacing of this application is 2.590 - 2.600 Å. That is, when the alkali metal layer spacing of this application increases, it indicates that at least part of the Mg element enters the Li layer, expanding the alkali metal layer spacing, which is beneficial to improving the lithium ion conduction ability, improving the structural stability under deep de-lithiation conditions, improving the Mn metal migration ability, and inhibiting the formation of the spinel phase.

[0061] In a possible implementation, the chemical formula of the lithium-rich manganese-based cathode material includes Li 1+ x Ni a Co b Mn c M d Mg e O y F z R h , where a + b + c + d + e = 1.0, 0.1 ≤ a < 0.5, 0 ≤ b ≤ 0.15, 0.5 ≤ c ≤ 0.7, d ≤ 0.2, 0.10 ≤ x ≤ 0.5, 0 < e ≤ 0.015, 2.13 ≤ y ≤ 2.50, 0.006 ≤ z ≤ 0.03, 0.001 ≤ h ≤ 0.02; 1.95 + x ≤ y + z + h ≤ 2.05 + x, z + h ≤ 0.2y, M includes one or more of Al, P, Ca, Ti, Cr, Fe, Cu, Zn, Sr, Se, Y, Zr, Si, Nb, Mo, Sb, Sn, Te, Ba, Cs, Ta, W, La, Ce, Sm, and Gd, and R includes one or more of S, Cl, B, and C.

[0062] In this application, for the M doping elements such as Al, Ti, Cr, Fe, Cu, Zn, and Sn, these element ions have relatively small radii or high matching degrees with the main elements, and they tend to be lattice doped more, improving the lattice layer stability. Some of them can be doped into the lithium layer to improve the support ability and inhibit the interlayer migration of metals; most of them are located in the transition metal layer, and to a certain extent, they inhibit the intra-layer migration of metals.

[0063] The doping elements P, Ca, Sr, Se, Y, Zr, Si, Nb, Mo, Sb, Te, Ba, Cs, Ta, W, La, Ce, Sm, and Gd, either have large ionic radii, high valence states, or combine with anions to form polymeric anions. These elements tend to accumulate at the crystal lattice surface or crystal interfaces, meaning their concentration at the surface or interface is generally higher than at the lattice center. These elements serve several purposes: firstly, they protect the crystal lattice interface from corrosion; secondly, their high valence suppresses oxygen release due to their typically stronger TM-O bonds; and thirdly, the polyanionic groups can bind interfacial metal ions, preventing dissolution and improving battery stability.

[0064] In this application, among the R doping elements, S and B can also form polyanions, which can bind interfacial metal ions, prevent metal ion dissolution, and improve battery stability; Cl can replace some O ions, improving the stability of the anion framework. C attaches to grain boundaries, improving conductivity and enhancing low-temperature and rate performance.

[0065] It is understandable that 0.1≤a<0.5, for example: 0.1, 0.2, 0.3, 0.4, 0.45 or any two of them, is not limited to the listed values. Other values ​​not listed in the range or any two other unlisted values ​​in the range also apply.

[0066] It is understandable that 0 ≤ b ≤ 0.15, for example: 0, 0.03, 0.05, 0.08, 0.1, 0.13, 0.15 or any two of them, is not limited to the listed values. Other values ​​not listed in this range or any two other values ​​not listed in this range also apply.

[0067] It is understandable that 0.5≤c≤0.7, for example: 0.5, 0.53, 0.55, 0.58, 0.6, 0.63, 0.65, 0.7 or any two of them, is not limited to the listed values. Other values ​​not listed in this range or any two other values ​​not listed in this range also apply.

[0068] It is understandable that d≤0.2, for example: a range consisting of 0, 0.05, 0.1, 0.15, 0.2 or any two of them, is not limited to the listed values, but also applies to other values ​​not listed or any two other values ​​not listed.

[0069] It is understood that 0.10 ≤ x ≤ 0.5, for example: 0.1, 0.2, 0.3, 0.4, 0.5 or the range composed of any two of them. It is not limited to the listed values, and other values not listed within this range or the range composed of any two other unlisted values are also applicable.

[0070] It is understood that 0 < e ≤ 0.015, for example: 0.002, 0.004, 0.006, 0.008, 0.01, 0.015 or the range composed of any two of them. It is not limited to the listed values, and other values not listed within this range or the range composed of any two other unlisted values are also applicable. It is understood that when the doping amount of Mg element in the lithium-rich manganese-based core material is within the above range, the lithium-ion conduction ability can be effectively improved, and the structural stability under deep lithium deintercalation conditions can be improved, thereby improving the capacity and initial efficiency of the material.

[0071] It is understood that 2.13 ≤ y ≤ 2.50, for example: 2.13, 2.23, 2.33, 2.35, 2.50 or the range composed of any two of them. It is not limited to the listed values, and other values not listed within this range or the range composed of any two other unlisted values are also applicable.

[0072] It is understood that 0.006 ≤ z ≤ 0.03, for example: 0.006, 0.008, 0.01, 0.012, 0.014, 0.016, 0.018, 0.02, 0.03 or the range composed of any two of them. It is not limited to the listed values, and other values not listed within this range or the range composed of any two other unlisted values are also applicable.

[0073] It is understood that 0.001 ≤ z ≤ 0.02, for example: 0.001, 0.004, 0.006, 0.008, 0.01, 0.012, 0.014, 0.016, 0.018, 0.02 or the range composed of any two of them. It is not limited to the listed values, and other values not listed within this range or the range composed of any two other unlisted values are also applicable.

[0074] In a possible implementation manner, the thickness of the coating layer is 2 nm - 20 nm.

[0075] It is understood that the thickness of the coating layer is 2 nm - 20 nm, for example: 2 nm, 3 nm, 5 nm, 8 nm, 10 nm, 13 nm, 15 nm, 17 nm, 20 nm or the range composed of any two of them. It is not limited to the listed values, and other values not listed within this range or the range composed of any two other unlisted values are also applicable.

[0076] Understandably, the thickness of the coating layer affects capacity and interfacial stability. Specifically, when the coating layer is within the aforementioned range, it ensures that even if a small amount of the coating material is consumed over time, it can still continuously protect the cathode material from corrosion at the complex electrochemical reaction interface. Simultaneously, a coating layer within the aforementioned protection range also ensures that there will be no decrease in material capacity and power performance due to the lower ionic conductivity of LiF compared to the bulk material.

[0077] In one possible implementation, the thickness of the coating layer is 2nm-14nm.

[0078] In one possible implementation, the specific surface area of ​​the lithium-rich manganese-based cathode material is 0.3~3.0 m². 2 / g.

[0079] Understandably, the specific surface area of ​​lithium-rich manganese-based cathode materials is 0.3~3.0 m². 2 / g, for example: 0.3m 2 / g, 0.5m 2 / g, 1m 2 / g, 1.5m 2 / g, 2.0m 2 / g, 2.5m 2 / g, 3.0m 2 The range consisting of / g or any two of them is not limited to the listed values; it also applies to other values ​​not listed within the range or any range consisting of any two other unlisted values.

[0080] Understandably, a specific surface area within the aforementioned range for lithium-rich manganese-based cathode materials increases the lithium-ion migration channels on the material surface, facilitating high-power charging and discharging and excellent capacity utilization. Simultaneously, it promotes uniform delithiation within the material, preventing localized stress buildup caused by uneven delithiation, and improving lattice stability and particle mechanical strength; particularly enhancing cycle performance under high-rate conditions. Furthermore, lithium-rich manganese-based cathode materials within the aforementioned specific surface area range can reduce the probability of side reactions caused by contact with the electrolyte, preventing surface corrosion and reducing cathode degradation, metal dissolution, and electrolyte consumption.

[0081] In one possible implementation, the specific surface area of ​​the lithium-rich manganese-based cathode material is 1.4~1.8 m². 2 / g.

[0082] In one possible implementation, the D50 of the lithium-rich manganese-based cathode material is 1.0 μm ≤ D50 ≤ 15.0 μm.

[0083] It is understood that 1.0μm≤D50≤15.0μm, for example: 1.0μm, 3.0μm, 5.0μm, 8.0μm, 10.0μm, 13.0μm, 15.0μm or any two of them, is not limited to the listed values. Other values ​​not listed in this range or any two other values ​​not listed in this range also apply.

[0084] In one possible implementation, the D50 of the lithium-rich manganese-based cathode material is 6.5 μm ≤ D50 ≤ 12.2 μm.

[0085] In one possible implementation, the coating layer further includes at least one element selected from La, Zr, Ba, and Cs.

[0086] In this application, the La, Zr, Ba, and Cs elements in the coating layer mainly exist in oxide form. These elements either have large ionic radii or high valence states, and tend to be enriched at the lattice surface or crystal interface, meaning their concentration at the lattice surface or crystal interface is generally higher than that at the lattice center. These elements serve two purposes: firstly, they protect the lattice interface from corrosion; secondly, the high valence of these elements can suppress oxygen release because they typically possess stronger TM-O bonds.

[0087] Secondly, this application provides a method for preparing a lithium-rich manganese-based cathode material, comprising the following steps:

[0088] A metal salt solution, a precipitant, and a complexing agent are mixed and reacted to obtain a hydroxide precursor; the hydroxide precursor and a lithium source are mixed and subjected to a first sintering to obtain a cathode material intermediate;

[0089] The cathode material intermediate and fluoride are mixed and subjected to a second sintering process to obtain a lithium-rich manganese-based cathode material, wherein the fluoride includes at least magnesium fluoride.

[0090] Understandably, this application employs a one-step method to simultaneously achieve Mg doping and LiF coating. Specifically, the F anions released from MgF during sintering possess extremely strong electronegativity, attracting Li ions to escape from the bulk phase, forming a Li-Mg exchange mechanism. This promotes uniform and deep Mg doping, and the extraction of Li ions activates the activity of Li₂MnO₃, thereby improving the material's capacity and initial efficiency to a certain extent. The specific reason is that the in-situ formation of the LiF coating layer can balance the ionic conductivity. Using an alkali-free metal fluoride for in-situ interfacial reaction with the material, since F ions are more electronegative than O ions, they can attract and extract lithium ions from the bulk phase to form the in-situ LiF coating layer, while leaving vacancies on the material surface, thus promoting uniform Mg doping. Therefore, a one-step process forms both a deeply uniform Mg doping layer in the bulk phase and a surface LiF coating layer. These two elements mutually promote each other, balancing the ionic conductivity of the cathode material and increasing its capacity in battery systems. LiF blocks direct contact between the electrolyte and part of the surface layer of the lithium-rich manganese-based core material, and the uniform Mg doping within the lithium-rich manganese-based core material improves the structural stability of the core material. The combination of these two factors reduces the active contact area and reactivity, suppresses interfacial side reactions, and can significantly improve the lifespan of the cathode.

[0091] In one possible implementation, the second sintering temperature is 800~900℃. It should be noted that this application utilizes the strong electronegativity of F element to extract Li ions from the bulk phase of the material under high temperature conditions, which can simultaneously construct oxygen vacancies in the bulk phase of the material and improve the activity of Li2MnO3. This application differs from the low-temperature sintering methods used in existing technologies. Existing technologies typically employ temperatures of 600°C or below, using fluoride composite cathodes followed by sintering to generate a LiF coating layer from residual alkali on the material surface. However, such low-temperature sintering cannot provide the energy needed to remove bulk Li ions. Furthermore, lithium-rich manganese-based cathode materials differ from traditional ternary cathode materials. The residual alkali on the surface of lithium-rich cathodes is typically below 500 ppm, insufficient to bind surface F elements to form a dense and uniform LiF coating layer. In addition, under the dry low-temperature coating process, F elements are difficult to diffuse to a uniform distribution. The wet coating process is complex, and the wet solution system can easily cause localized corrosion on the lithium-rich cathode surface, which already has little residual lithium, leading to the dissolution and precipitation of Li and transition metal elements. Even if LiF is eventually formed, its coating uniformity, thickness, and binding energy are low, making it difficult to provide strong protection. Excessive F will form metal fluorides with other metals on the cathode material surface, affecting the surface ionic conductivity. This application uses high-temperature sintering, and the thickness of the LiF coating layer can be adjusted according to the amount of F contained in the added F source. This allows for flexible adjustment of the LiF layer thickness on the material surface according to different application scenarios, achieving a balance between capacity utilization, stability, and other indicators.

[0092] It is understood that the second sintering temperature is 800~900℃, for example: 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, 900℃ or any two of these ranges, not limited to the listed values, but also other values ​​not listed or any two other values ​​not listed within this range.

[0093] In one possible implementation, a hydroxide precursor, a lithium source, and a modifying additive are mixed and subjected to a first sintering. The modifying additive includes a compound containing an element M, which includes one or more of Al, P, Ca, Ti, Cr, Fe, Cu, Zn, Sr, Se, Y, Zr, Si, Nb, Mo, Sb, Sn, Te, Ba, Cs, Ta, W, La, Ce, Sm, and Gd.

[0094] In one possible implementation, the fluoride further includes fluoride I, which includes at least one of LaF3, ZrF4, BaF2, and CsF.

[0095] Understandably, the coating reagents, in addition to magnesium fluoride, also include fluoride I. Fluoride I is mainly a neutral fluoride and / or a basic fluoride, allowing for gentle contact between the coating layer and the lithium-rich manganese-based core material during coating. This minimizes thermodynamically induced or spontaneous acid-base corrosion and uneven localized reactions during the reaction, ultimately ensuring no excessive delithiation or deoxidation of the material surface at the reaction endpoint. In other words, during the reaction, the material structure only creates vacancies due to gentle delithiation, further promoting reaction homogeneity and enhancing the integrity of the bulk layered structure. Therefore, the addition of fluoride further improves the surface structural strength.

[0096] In one possible implementation, the second sintering time is 2-5 hours, for example, a range of 2 hours, 3 hours, 4 hours, 5 hours or any two of these, not limited to the listed values, but also applicable to other values ​​not listed or any range of two other unlisted values.

[0097] In one possible implementation, the heating rate of the second sintering is greater than or equal to 10 °C / min.

[0098] In one possible implementation, the heating rate of the second sintering is 10-15°C / min, for example, a range of 10°C / min, 11°C / min, 12°C / min, 13°C / min, 14°C / min, 15°C / min or any two of these ranges, not limited to the listed values, and other values ​​not listed or any two other values ​​not listed are also applicable.

[0099] This application specifies that the heating rate of the second sintering is greater than or equal to 10℃ / min, so as to reach a high temperature of 800~900℃ in a relatively short time. The rapid heating process causes the coating agent to melt quickly and uniformly cover the surface of the core material, making full contact with the core material to form a molten system. At this time, the high temperature provides sufficient energy for the system, allowing the newly formed crystals in the molten system to grow in the orientation that minimizes the energy of the system, i.e., twinning or quasi-twinning. Microscopically, this is manifested as the newly formed lithium fluoride (200) lattice fringes extending outward along the (003) lattice fringes of the core material in a nearly or basically consistent orientation, so that the system reaches a stable, low-energy state. Secondly, rapid heating (i.e., a short dwell time during the heating process) allows the material to complete the melting and surface reaction process when it reaches a high temperature of 800~900℃. At this time, the temperature is sufficient and the system reaction energy is sufficient, making it easy for the new crystal to grow in a way or orientation that reduces system energy and increases stability. That is, the (200) lattice stripes of lithium fluoride extend outward along the direction of the (003) lattice stripes of the core material in an orientation that is close to or basically consistent with the direction.

[0100] In one possible implementation, when the chemical formula of the resulting lithium-rich manganese-based cathode material includes Li 1+ x Ni a Co b Mn c M d Mg e O y F z R h When R contains S, the metal salt solution is the sulfate solution corresponding to the metal; when R is one or more of Cl, B and C, "mixing the cathode material intermediate and fluoride and performing a second sintering treatment" includes "mixing the cathode material intermediate, fluoride and R-containing compound and performing a second sintering treatment".

[0101] In one possible implementation, the metal salt solution includes a nickel salt solution, a cobalt salt solution, and a manganese salt solution.

[0102] In one possible implementation, the precipitant comprises a sodium hydroxide solution.

[0103] In one possible implementation, the complexing agent includes one or more of the following: ammonia, monosodium glutamate, ascorbic acid, ammonium sulfate, ammonium persulfate, and sodium hexametaphosphate.

[0104] In one possible implementation, during the second sintering process of mixing the cathode material intermediate and the fluoride, the fluoride further includes fluoride I, which is mainly a neutral fluoride and / or an alkaline fluoride.

[0105] In one possible implementation, the temperature of the first sintering is 800~950°C.

[0106] It is understood that the first sintering temperature is 800~950℃, for example: 800℃, 810℃, 820℃, 830℃, 840℃, 850℃, 860℃, 870℃, 880℃, 890℃, 900℃, 910℃, 920℃, 930℃, 940℃, 950℃ or any two of these ranges, not limited to the listed values, other values ​​not listed within this range or any two other unlisted values ​​within this range also apply.

[0107] In one possible implementation, the heating rate of the first sintering is 2~3℃ / min.

[0108] It is understood that the heating rate of the first sintering is 2~3℃ / min, for example: 2℃ / min, 2.5℃ / min, 3℃ / min or any combination thereof, not limited to the listed values, other values ​​not listed or any combination of two other values ​​not listed are also applicable.

[0109] In one possible implementation, the holding time for the first sintering is 2 to 12 hours.

[0110] It is understandable that the holding time for the first sintering is 2 to 12 hours, for example: 2 hours, 4 hours, 6 hours, 8 hours, 10 hours or 12 hours, etc., not limited to the listed values, and other values ​​not listed in this range also apply.

[0111] Thirdly, this application provides a positive electrode sheet comprising the aforementioned lithium-rich manganese-based positive electrode material.

[0112] The positive electrode sheet of this application specifically includes a positive current collector and a positive active layer formed of lithium-rich manganese-based positive electrode material disposed on the surface of the positive current collector.

[0113] In the specific preparation of the positive electrode sheet, for example, the lithium-rich manganese-based positive electrode material of the application can be dispersed with a conductive agent and a binder in an appropriate amount of N-methylpyrrolidone (NMP) solvent, and thoroughly stirred and mixed to form a uniform positive electrode slurry; the positive electrode slurry is uniformly coated on the positive electrode current collector, and after drying, rolling and cutting, the positive electrode sheet is obtained.

[0114] In one specific embodiment, the positive electrode active layer comprises, by weight percentage, 70-99 wt% lithium-rich manganese-based positive electrode material, 0.5-15 wt% conductive agent, and 0.5-15 wt% binder; more specifically, it comprises 80-98 wt% lithium-rich manganese-based positive electrode material, 1-10 wt% conductive agent, and 1-10 wt% binder.

[0115] The positive electrode current collector can be made of at least one of aluminum foil or nickel foil; the conductive agent can be selected from at least one of carbon black, acetylene black, graphene, Ketjen black, and carbon fiber; the binder can be selected from at least one of polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl fluoride, polyethylene, polypropylene, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, ethylene oxide-containing polymers, polyvinylpyrrolidone, and polyurethane. Thirdly, this application provides a battery including the above-mentioned positive electrode sheet.

[0116] It is conceivable that, in addition to the aforementioned positive electrode, the battery of this application also includes a negative electrode, an electrolyte, and a separator.

[0117] This application does not strictly limit the negative electrode active material in the negative electrode sheet. It can be at least one of the negative electrode active materials commonly used in lithium-ion batteries, such as graphite, hard carbon, soft carbon, mesophase carbon microspheres, silicon-based negative electrode materials (mainly including silicon suboxide and silicon-carbon negative electrode), and tin-based negative electrode materials (mainly including tin and tin alloy).

[0118] This application does not strictly limit the choice of electrolyte, which may include one or more solvents commonly used in lithium-ion battery electrolytes, as well as lithium salts commonly used in lithium-ion electrolytes. For example, the solvent may be ethylene carbonate, propylene carbonate, butene carbonate, fluoroethylene carbonate (FEC), dimethyl carbonate (DMC), diethyl carbonate (DEC), difluoroethylene carbonate (DFEC), dipropyl carbonate, methyl ethyl carbonate (EMC), ethyl acetate, ethyl propionate, propyl acetate, propyl propionate, sulfolane, γ-butyrolactone, etc.; the lithium salt may be one or more of lithium hexafluorophosphate (LiPF6), lithium bis(fluorosulfonyl)imide (LiFSI), and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI).

[0119] This application does not strictly limit the choice of separator material. It can be one of the separator materials commonly used in lithium-ion batteries, such as polypropylene separator (PP), polyethylene separator (PE), polypropylene / polyethylene double-layer composite membrane (PP / PE), polyimide electrospun separator (PI), polypropylene / polyethylene / polypropylene triple-layer composite membrane (PP / PE / PP), cellulose nonwoven separator, and separator with ceramic coating.

[0120] In battery manufacturing, the positive electrode, separator, and negative electrode are wound or stacked to obtain a bare battery, which is then packaged into a pre-stamped aluminum-plastic film bag or steel casing. After the packaged battery is dried at 85°C, the electrolyte is injected into the dried battery. The battery undergoes resting, formation, and secondary sealing to complete battery manufacturing.

[0121] Example 1

[0122] The preparation method of the lithium-rich manganese-based cathode material provided in this embodiment is as follows:

[0123] Preparation of hydroxide precursor (D50=7.0μm):

[0124] S1. Prepare nickel and manganese salt solutions with a molar concentration of 2.5 mol / L, respectively. The nickel salt and manganese salt are nickel sulfate and manganese sulfate solutions, respectively. Prepare a 10 mol / L sodium hydroxide solution as a precipitant and a 10 wt% ammonia complexing agent solution.

[0125] S2. Fill the reactor with clean water and set the stirring speed to 800 rpm and the temperature to 55℃. Introduce nitrogen gas containing 0.2 vol% oxygen. After venting for 2 hours, introduce nickel and manganese salt solutions, precipitant, and complexing agent into the reactor for reaction. The ratio of nickel to manganese salt solutions introduced should satisfy the following: the molar ratio of nickel to manganese is 35:65. Maintain the pH of the reaction system at 11.2. After the D50 of the material in the reactor grows to 2.0 μm, lower the pH to 10.8.

[0126] S3. After the particle size grows to D50 = target particle size of 7.0μm, stop feeding and collect the slurry in the reactor.

[0127] S4. The slurry collected in S3 is subjected to aging, washing, centrifugation, and drying to obtain the hydroxide precursor.

[0128] Preparation of cathode material intermediate: A hydroxide precursor, lithium carbonate and additive Nb2O5 were mixed, wherein the amount of hydroxide precursor, lithium carbonate and additive Nb2O5 added was in the molar ratio of nickel, manganese, lithium and Nb of 35:65:135:0.2. The mixture was sintered once in a box furnace at a heating rate of 2℃ / min, a sintering temperature of 880℃ and a holding time of 10h. After that, it was naturally cooled to room temperature, crushed and sieved to obtain the cathode material intermediate.

[0129] Preparation of lithium-rich manganese-based cathode material: The cathode material intermediate and the treatment agent MgF2 were further mixed evenly, wherein the amount of cathode material intermediate and the treatment agent MgF2 added was based on a nickel to Mg molar ratio of 35:0.8. Secondary sintering was carried out in a box furnace at a heating rate of 13℃ / min, a sintering temperature of 850℃, and a holding time of 4h. Afterwards, the mixture was allowed to cool naturally to room temperature, crushed, and sieved to obtain the lithium-rich manganese-based cathode material.

[0130] Example 2

[0131] The preparation method of the lithium-rich manganese-based cathode material provided in this embodiment is basically the same as that in Example 1, with the only difference being as follows:

[0132] Preparation of cathode material intermediate: A hydroxide precursor, lithium carbonate and additive Nb2O5 are mixed, wherein the amount of hydroxide precursor, lithium carbonate and additive Nb2O5 added is in the molar ratio of nickel, manganese, lithium and Nb as 35:65:136:0.2.

[0133] Preparation of lithium-rich manganese-based cathode material: The cathode material intermediate and the treatment agent MgF2 are further mixed evenly, wherein the amount of cathode material intermediate and the treatment agent MgF2 added is based on a nickel to Mg molar ratio of 35:0.3.

[0134] The remaining process parameters for the secondary sintering after primary sintering are shown in Table 1.

[0135] Example 3

[0136] The preparation method of the lithium-rich manganese-based cathode material provided in this embodiment is basically the same as that in Example 1, with the only difference being as follows:

[0137] Preparation of lithium-rich manganese-based cathode material: The cathode material intermediate and the treatment agent MgF2 are further mixed evenly, wherein the amount of cathode material intermediate and the treatment agent MgF2 added is based on a molar ratio of nickel to Mg of 35:1.5.

[0138] The remaining process parameters for the secondary sintering after primary sintering are shown in Table 1.

[0139] Example 4

[0140] The preparation method of the lithium-rich manganese-based cathode material provided in this embodiment is basically the same as that in Example 1, with the only difference being as follows:

[0141] The changes in process parameters for secondary sintering are shown in Table 1.

[0142] Example 5

[0143] The only difference between this embodiment and Embodiment 1 is that the secondary sintering temperature is 700℃. Compared to Embodiment 1, the secondary sintering temperature in this embodiment is slightly lower, resulting in limited lithium ion extraction from the bulk phase and consequently limited Mg doping at lithium sites. Therefore, compared to Embodiment 1, this embodiment offers limited improvement in lithium-ion conductivity.

[0144] Example 6

[0145] The preparation method of the lithium-rich manganese-based cathode material provided in this embodiment is basically the same as that in Example 1, with the only difference being as follows:

[0146] Preparation of cathode material intermediate: Mix hydroxide precursor and lithium carbonate, wherein the amount of hydroxide precursor and lithium carbonate added is in the molar ratio of nickel, manganese and lithium of 35:65:135.

[0147] Preparation of lithium-rich manganese-based cathode material: The cathode material intermediate and the treatment agent MgF2 are further mixed evenly, wherein the amount of cathode material intermediate and the treatment agent MgF2 added is based on a nickel to Mg molar ratio of 35:0.8.

[0148] Example 7

[0149] The preparation method of the lithium-rich manganese-based cathode material provided in this embodiment is basically the same as that in Example 1, with the only difference being as follows:

[0150] Preparation of cathode material intermediate: Hydroxide precursor, lithium carbonate and additive Cs2O are mixed, wherein the amount of added hydroxide precursor, lithium carbonate and additive Cs2O is in the molar ratio of nickel, manganese, lithium and Cs as 35:65:135:0.4.

[0151] Preparation of lithium-rich manganese-based cathode material: The cathode material intermediate and the treatment agent MgF2 are further mixed evenly, wherein the amount of cathode material intermediate and the treatment agent MgF2 added is based on a nickel to Mg molar ratio of 35:0.6.

[0152] The remaining process parameters for the secondary sintering after primary sintering are shown in Table 1.

[0153] Example 8

[0154] The preparation method of the lithium-rich manganese-based cathode material provided in this embodiment is basically the same as that in Example 1, with the only difference being as follows:

[0155] Preparation of cathode material intermediate: Hydroxide precursor, lithium carbonate, additive Nb2O5 and La2O3 are mixed, wherein the amount of added hydroxide precursor, lithium carbonate, additive Nb2O5 and La2O3 is in the molar ratio of nickel, manganese, lithium, Nb and La as 35:65:135:0.1:0.3.

[0156] Preparation of lithium-rich manganese-based cathode material: The cathode material intermediate and the treatment agent MgF2 are further mixed evenly, wherein the amount of cathode material intermediate and the treatment agent MgF2 added is based on a nickel to Mg molar ratio of 35:0.6.

[0157] The remaining process parameters for the secondary sintering after primary sintering are shown in Table 1.

[0158] Example 9

[0159] The preparation method of the lithium-rich manganese-based cathode material provided in this embodiment is basically the same as that in Example 1, with the only difference being as follows:

[0160] Preparation of cathode material intermediate: Hydroxide precursor, lithium carbonate, additive Nb2O5 and La2O3 are mixed, wherein the amount of added hydroxide precursor, lithium carbonate, additive Nb2O5 and La2O3 is in the molar ratio of nickel, manganese, lithium, Nb and La as 35:65:135:0.2:0.2.

[0161] Preparation of lithium-rich manganese-based cathode material: The cathode material intermediate and the treatment agent MgF2 are further mixed evenly, wherein the amount of cathode material intermediate and the treatment agent MgF2 added is based on a nickel to Mg molar ratio of 35:0.6.

[0162] The remaining process parameters for the secondary sintering after primary sintering are shown in Table 1.

[0163] Example 10

[0164] The preparation method of the lithium-rich manganese-based cathode material provided in this embodiment is basically the same as that in Example 1, with the only difference being as follows:

[0165] Preparation of cathode material intermediate: Hydroxide precursor, lithium carbonate, additives SiO2 and La2O3 are mixed, wherein the amount of added hydroxide precursor, lithium carbonate, additives SiO2 and La2O3 is in the molar ratio of nickel, manganese, lithium, Si and La as 35:65:135:0.8:0.6.

[0166] Preparation of lithium-rich manganese-based cathode material: The cathode material intermediate and the treatment agent MgF2 are further mixed evenly, wherein the amount of cathode material intermediate and the treatment agent MgF2 added is based on a nickel to Mg molar ratio of 35:0.6.

[0167] The remaining process parameters for the secondary sintering after primary sintering are shown in Table 1.

[0168] Example 11

[0169] The preparation method of the lithium-rich manganese-based cathode material provided in this embodiment is basically the same as that in Example 1, with the only difference being as follows:

[0170] Preparation of cathode material intermediate: Hydroxide precursor, lithium carbonate, additive WO3 and La2O3 are mixed, wherein the amount of added hydroxide precursor, lithium carbonate, additive WO3 and La2O3 is in the molar ratio of nickel, manganese, lithium, W and La as 35:65:135:0.8:0.6.

[0171] Preparation of lithium-rich manganese-based cathode material: The cathode material intermediate and the treatment agent MgF2 are further mixed evenly, wherein the amount of cathode material intermediate and the treatment agent MgF2 added is based on a nickel to Mg molar ratio of 35:0.6.

[0172] The remaining process parameters for the secondary sintering after primary sintering are shown in Table 1.

[0173] Example 12

[0174] The preparation method of the lithium-rich manganese-based cathode material provided in this embodiment is basically the same as that in Example 1, with the only difference being as follows:

[0175] In S2, the ratio of nickel and manganese salt solutions introduced satisfies the following condition: the molar ratio of nickel to manganese is 45:54.

[0176] Preparation of cathode material intermediate: A hydroxide precursor, lithium carbonate and additive Nb2O5 are mixed, wherein the amount of hydroxide precursor, lithium carbonate and additive Nb2O5 added is in the molar ratio of nickel, manganese, lithium and Nb as 45:54:115:0.4.

[0177] Preparation of lithium-rich manganese-based cathode material: The cathode material intermediate and the treatment agent MgF2 are further mixed evenly, wherein the amount of cathode material intermediate and the treatment agent MgF2 added is based on a nickel to Mg molar ratio of 45:0.6.

[0178] The remaining process parameters for the secondary sintering after primary sintering are shown in Table 1.

[0179] Example 13

[0180] The preparation method of the lithium-rich manganese-based cathode material provided in this embodiment is basically the same as that in Example 1, with the only difference being as follows:

[0181] In S1, nickel, cobalt, and manganese salt solutions with a molar concentration of 2.5 mol / L were prepared, with nickel salt, cobalt salt, and manganese salt being nickel sulfate, cobalt phosphate, and manganese sulfate solutions, respectively.

[0182] In S2, the ratio of nickel, cobalt, and manganese salt solutions introduced satisfies the following condition: the molar ratio of nickel, cobalt, and manganese is 18:15:65.

[0183] Preparation of cathode material intermediate: A hydroxide precursor, lithium carbonate, additives Nb2O5, Al2O3 and La2O3 are mixed, wherein the amounts of the hydroxide precursor, lithium carbonate, additives Nb2O5, Al2O3 and La2O3 are added according to the molar ratio of nickel, cobalt, manganese, lithium, Nb, Al and La of 18:15:65:145:0.4:0.6:0.4.

[0184] Preparation of lithium-rich manganese-based cathode material: The amount of cathode material intermediate and treatment agent MgF2 added is based on a nickel to Mg molar ratio of 16:0.6.

[0185] The remaining process parameters for the secondary sintering after primary sintering are shown in Table 1.

[0186] Example 14

[0187] The preparation method of the lithium-rich manganese-based cathode material provided in this embodiment is basically the same as that in Example 1, with the only difference being as follows:

[0188] Preparation of cathode material intermediate: The amount of hydroxide precursor, lithium carbonate and additive Nb2O5 added is according to the molar ratio of nickel, manganese, lithium and Nb of 35:65:135:0.22.

[0189] Preparation of lithium-rich manganese-based cathode material: The cathode material intermediate is further mixed with the treatment agents MgF2 and ZrF4 to form a homogeneous mixture, wherein the amount of cathode material intermediate and treatment agents MgF2 and ZrF4 added is based on the molar ratio of nickel, Mg and Zr of 35:0.44:0.08.

[0190] The remaining process parameters for the secondary sintering after primary sintering are shown in Table 1.

[0191] Example 15

[0192] The preparation method of the lithium-rich manganese-based cathode material provided in this embodiment is basically the same as that in Example 1, with the only difference being as follows:

[0193] Preparation of cathode material intermediate: The amount of hydroxide precursor, lithium carbonate and additive Nb2O5 added is according to the molar ratio of nickel, manganese, lithium and Nb of 35:65:135:0.25.

[0194] Preparation of lithium-rich manganese-based cathode material: The cathode material intermediate is further mixed with the treatment agents MgF2 and LaF3 to form a homogeneous mixture, wherein the amount of cathode material intermediate and treatment agents MgF2 and LaF3 added is based on a molar ratio of nickel, Mg and La of 35:0.45:0.1.

[0195] The remaining process parameters for the secondary sintering after primary sintering are shown in Table 1.

[0196] Example 16

[0197] The preparation method of the lithium-rich manganese-based cathode material provided in this embodiment is basically the same as that in Example 1, with the only difference being as follows:

[0198] Preparation of cathode material intermediate: The amount of hydroxide precursor, lithium carbonate and additive Nb2O5 added is according to the molar ratio of nickel, manganese, lithium and Nb of 35:65:135:0.25.

[0199] Preparation of lithium-rich manganese-based cathode material: The cathode material intermediate is further mixed with the treatment agents MgF2 and BaF2 to achieve uniformity, wherein the amount of cathode material intermediate and treatment agents MgF2 and BaF2 added is based on the molar ratio of nickel, Mg and Ba of 35:0.4:0.2.

[0200] The remaining process parameters for the secondary sintering after primary sintering are shown in Table 1.

[0201] Example 17

[0202] The preparation method of the lithium-rich manganese-based cathode material provided in this embodiment is basically the same as that in Example 1, with the only difference being as follows:

[0203] Preparation of cathode material intermediate: The amount of hydroxide precursor, lithium carbonate and additive Nb2O5 added is according to the molar ratio of nickel, manganese, lithium and Nb of 35:65:135:0.25.

[0204] Preparation of lithium-rich manganese-based cathode material: The cathode material intermediate is further mixed with the treatment agents MgF2 and CsF to achieve uniformity, wherein the amount of cathode material intermediate and treatment agents MgF2 and CsF added is based on the molar ratio of nickel, Mg and Cs of 35:0.5:0.2.

[0205] The remaining process parameters for the secondary sintering after primary sintering are shown in Table 1.

[0206] Example 18

[0207] The preparation method of the lithium-rich manganese-based cathode material provided in this embodiment is basically the same as that in Example 1, with the only difference being as follows:

[0208] Preparation of cathode material intermediate: The amount of hydroxide precursor, lithium carbonate and additive Nb2O5 added is according to the molar ratio of nickel, manganese, lithium and Nb of 35:65:135:0.2.

[0209] Preparation of lithium-rich manganese-based cathode material: The cathode material intermediate is further mixed with the treatment agents MgF2 and CsF to achieve uniformity, wherein the amount of cathode material intermediate and treatment agents MgF2 and CsF added is based on the molar ratio of nickel, Mg and Cs of 35:0.4:0.4.

[0210] The remaining process parameters for the secondary sintering after primary sintering are shown in Table 1.

[0211] Example 19

[0212] The preparation method of the lithium-rich manganese-based cathode material provided in this embodiment is basically the same as that in Example 1, with the only difference being as follows:

[0213] In S1, nickel, cobalt, and manganese salt solutions with a molar concentration of 2.5 mol / L were prepared, with nickel salt, cobalt salt, and manganese salt being nickel sulfate, cobalt phosphate, and manganese sulfate solutions, respectively.

[0214] In S2, the ratio of nickel, cobalt, and manganese salt solutions introduced satisfies the following condition: the molar ratio of nickel, cobalt, and manganese is 30:05:64.

[0215] Preparation of cathode material intermediate: A hydroxide precursor, lithium carbonate, lithium chloride and additive Nb2O5 are mixed, wherein the amount of hydroxide precursor, lithium carbonate, lithium chloride and additive Nb2O5 added is in the molar ratio of nickel, cobalt, manganese, lithium, Nb and chlorine of 30:05:64:135:0.2:1.4.

[0216] Preparation of lithium-rich manganese-based cathode material: The cathode material intermediate and the treatment agent MgF2 are further mixed evenly, wherein the amount of cathode material intermediate and the treatment agent MgF2 added is based on a nickel to Mg molar ratio of 30:0.8.

[0217] The remaining process parameters for the secondary sintering after primary sintering are shown in Table 1.

[0218] Comparative Example 1

[0219] The only difference between this comparative example and Example 1 is that:

[0220] When preparing the intermediate of the cathode material, the hydroxide precursor, lithium carbonate and additive Nb2O5 are mixed, wherein the amount of hydroxide precursor, lithium carbonate and additive Nb2O5 added is in the molar ratio of nickel, manganese, lithium and Nb as 35:65:135:0.4.

[0221] Furthermore, in the preparation of lithium-rich manganese-based cathode materials, the cathode material intermediates are directly subjected to secondary sintering without the addition of MgF2.

[0222] Comparative Example 2

[0223] The only difference between this comparative example and Example 1 is that Mg doping is not performed, and only AlF3 coating is performed.

[0224] The specific differences from Example 1 are only as follows:

[0225] When preparing the cathode material intermediate, a hydroxide precursor, lithium carbonate, and additive Nb2O5 are mixed, wherein the amounts of the hydroxide precursor, lithium carbonate, and additive Nb2O5 are added according to the molar ratio of nickel, manganese, lithium, and Nb of 35:65:135:0.4.

[0226] In the preparation of lithium-rich manganese-based cathode materials: the cathode material intermediate and the treatment agent AlF3 are further mixed evenly, wherein the amount of cathode material intermediate and treatment agent AlF3 added is based on a nickel to Al molar ratio of 35:0.6.

[0227] Comparative Example 3

[0228] The only difference between this comparative example and Example 1 is the preparation of the intermediate for the cathode material. The specific differences are as follows:

[0229] The hydroxide precursor, lithium carbonate, and additives Nb2O5 and MgO are mixed, wherein the amounts of the hydroxide precursor, lithium carbonate, additives Nb2O5 and MgO are added according to the molar ratio of nickel, manganese, lithium, Nb and Mg of 35:65:135:0.2:0.8.

[0230] Furthermore, the obtained cathode material intermediate is directly used as a lithium-rich manganese-based cathode material, that is, the comparative ratio is Mg-doped, but MgF2 is not added for secondary sintering.

[0231] Comparative Example 4

[0232] The only differences between this comparative example and Example 1 are: the preparation of the intermediate for the cathode material and the preparation of the lithium-rich manganese-based cathode material are different. The specific differences are as follows:

[0233] Cathode material intermediate: A hydroxide precursor, lithium carbonate, and additives Nb2O5 and MgO are mixed, wherein the amounts of the hydroxide precursor, lithium carbonate, additives Nb2O5 and MgO are added according to the molar ratio of nickel, manganese, lithium, Nb and Mg of 34.5:64.5:135:0.2:0.4.

[0234] Preparation of lithium-rich manganese-based cathode material: The cathode material intermediate and the treatment agent CaF2 are further mixed evenly, wherein the amount of cathode material intermediate and the treatment agent CaF2 added is based on a molar ratio of nickel to Ca of 34.5:0.8.

[0235] Comparative Example 5

[0236] The only difference between this comparative example and Example 1 is the preparation of the intermediate for the cathode material. The specific differences are as follows:

[0237] The hydroxide precursor, lithium carbonate, and additives Nb2O5 and MgF2 were mixed, wherein the amounts of the hydroxide precursor, lithium carbonate, additives Nb2O5 and MgF2 were added according to the molar ratio of nickel, manganese, lithium, Nb and Mg of 34.5:64.5:135:0.2:0.8.

[0238] Furthermore, the obtained cathode material intermediate is directly used as a lithium-rich manganese-based cathode material, that is, the comparative ratio is Mg-doped, but no secondary sintering treatment is performed.

[0239] Comparative Example 6

[0240] Preparation of a matrix Mg&F co-doped hydroxide precursor (D50=7.0μm):

[0241] S1. Prepare nickel, manganese, and magnesium salt solutions with a molar concentration of 2.5 mol / L, respectively. The sources of nickel, manganese, and magnesium are nickel sulfate, manganese sulfate, and magnesium sulfate, respectively. Prepare a 10 mol / L mixed solution of sodium hydroxide and sodium fluoride, and a 10 wt% ammonia complexing agent solution.

[0242] S2. Fill the reactor with clean water and set the stirring speed to 800 rpm and the temperature to 55℃. Introduce nitrogen gas containing 0.2 vol% oxygen. After venting for 2 hours, introduce a metal salt solution, precipitant, and complexing agent into the reactor, maintaining the pH of the reaction system at 11.2. Once the D50 of the material in the reactor has grown to 2.0 μm, lower the pH to 10.8. The metal salts include nickel, manganese, and magnesium salt solutions and sodium fluoride solution, wherein the molar ratio of nickel, manganese, magnesium, and fluorine is 35:65:0.8:1.6.

[0243] S3. After the particle size grows to D50 = target particle size of 7.0μm, stop feeding and collect the slurry in the reactor.

[0244] S4. The slurry collected in S3 is subjected to aging, washing, centrifugation, and drying to obtain a conventional hydroxide precursor.

[0245] The above-mentioned hydroxide precursor, lithium carbonate, and additive Nb2O5 were mixed, with the amount of hydroxide precursor, lithium carbonate, and additive Nb2O5 added according to the molar ratio of nickel, manganese, lithium, and Nb being 35:65:135:0.2. The mixture was sintered once in a box furnace or roller kiln with a heating rate of 2℃ / min, a sintering temperature of 880℃, and a holding time of 10h. After that, it was naturally cooled to room temperature, crushed, and sieved to obtain a lithium-rich cathode.

[0246] Test example:

[0247] Particle size determination: The particle size of the lithium-rich manganese-based cathode materials in each embodiment and comparative example was determined using a laser particle size analyzer. D50 represents the particle size of the cathode material particles when the cumulative volume reaches 50% in the volume-based particle size distribution. The test results are shown in Table 3.

[0248] BET test: The specific surface area was determined by nitrogen adsorption BET method, and the test was carried out in accordance with the test method specified in national standard GB / T 19587-2017. The test results are shown in Table 3.

[0249] Chemical composition determination: The actual chemical composition of the lithium-rich manganese-based cathode materials in each example and comparative example was determined by ICP-AES, and the test results are shown in Table 3. The results show that the actual chemical composition of the finished products in each example and comparative example is basically consistent with the design ratio.

[0250] HRTEM test: The material of the coating layer of the lithium-rich manganese-based cathode material in each embodiment and comparative example was measured by HRTEM, the coating layer thickness was measured (5 measurements were selected and the average value was taken), and the angle between the lattice stripes of the LiF (200) crystal plane and the lithium-rich manganese-based core material (300) crystal plane (the lattice stripe angle was photographed along the crystal axis of the core material

[110] ).

[0251] Test of d(Li-O-Li) spacing of lithium-rich manganese-based cathode material: The cathode material powder that has not been charged or discharged was placed in a conventional XRD test sample stage. The sample was flattened by using a glass slide to press the material. Powder XRD measurement was performed using a Bruker D8 Advance XRD instrument. The test angle 2θ was 10°~100°, the step size was 2θ=0.02°, and the test time for each step was 0.1s.

[0252] The XRD spectra obtained from the tests were refined using TOPAS software. The refinement steps were as follows:

[0253] 1. Open the standard data processing template and import the material data to be refined;

[0254] 2. Import the structural model into a CIF card with an R-3m space group;

[0255] 3. Click the "Refine" button to perform refinement calculations for materials D003, D101, and D104;

[0256] 4. Select the existing structural models in the template, and click "Refine" again to refine the crystal structure parameters of the material.

[0257] 5. If both the WeightedRProfile (Rwp) and Rexpected (Rp) values ​​are below 10 (the smaller the value, the closer the measured spectrum and the simulated spectrum are), and the GoodnessofFit (GOF) value is less than 1.5, it can be considered that the refinement is complete. At this time, the d (Li-O-Li) spacing of the material can be read from the software interface.

[0258] Electrochemical testing:

[0259] Assembling liquid coin cells: The lithium-rich manganese-based cathode materials prepared according to the above examples and comparative examples were assembled into liquid coin cells. The assembly method was as follows: The obtained lithium-rich manganese-based cathode material, conductive agent Super-P, and binder PVDF were added to NMP solvent in a mass ratio of 94:3:3 and mixed evenly to obtain a slurry. The obtained slurry was then subjected to coating, drying, stamping, and rolling to obtain a cathode sheet. The compaction density of the cathode sheet was 2.8 g / cm³. 3The stainless steel casing, positive electrode, PP separator, and lithium sheet of the coin cell are stacked in sequence, and a certain amount of electrolyte is added (the electrolyte composition is 1M LiPF6 dissolved in EC:EMC:FEC=3:6:1 (volume ratio), and 1wt% LiDFOB is added before sealing and allowing it to stand to obtain a liquid coin cell half-cell).

[0260] Assembling Liquid Soft-Pack Full Cells: The lithium-rich manganese-based cathode materials prepared according to the above examples and comparative examples were assembled into liquid soft-pack full cells. The assembly method was as follows: the obtained lithium-rich manganese-based cathode material, conductive agent Super-P, and binder PVDF were added to NMP solvent in a mass ratio of 94:3:3 and mixed evenly to obtain a slurry. The obtained slurry was then coated, dried, and rolled to obtain a cathode sheet. The compaction density of the cathode sheet was 2.8 g / cm³. 3 The negative electrode is assembled into a pouch cell (with a negative electrode mass ratio of 95.5 (graphite):1 (conductive agent SP):2 (binder SBR):1.5 (thickener CMC), and the compaction density of the negative electrode sheet is 1.6 g / cm³). 3 (The separator is a PP separator), add electrolyte (the electrolyte consists of 1M LiPF6 dissolved in EC:EMC:FEC=3:6:1 (volume ratio), add 1wt% LiDFOB, and then encapsulate and let stand to form a soft-pack full cell).

[0261] The batteries obtained above were subjected to the following tests (test results are shown in Table 4):

[0262] 1. 0.1C discharge capacity (button battery test):

[0263] Test method: After the assembled battery has been left to stand for 5 hours, it is charged at a constant current of 0.1C to 4.55V, then charged at a constant voltage of 4.55V until the cutoff current is equal to 0.05C. After standing for 5 minutes, it is discharged at a constant current of 0.1C to 2.5V. The resulting discharge capacity is the 0.1C discharge capacity.

[0264] 2. First Coulomb Efficiency (Button Battery Test):

[0265] Test method: After the assembled battery has been stationary for 5 hours, it is charged at a constant current of 0.1C to 4.55V, then charged at a constant voltage of 4.55V until the cutoff current is equal to 0.05C. After being stationary for 5 minutes, it is discharged at a constant current of 0.1C to 2.5V. The resulting discharge capacity / charge capacity is the initial coulombic efficiency.

[0266] 3. Capacity retention rate after 800 cycles at 1.0C (full battery test):

[0267] Test method: The test is divided into room temperature and high temperature tests. The room temperature is 25℃ and the high temperature is 45℃. After the battery completes the first discharge capacity test, it is charged at a constant current of 1.0C to 4.5V, then charged at a constant voltage of 4.5V until the cutoff current is equal to 0.05C. After resting for 5 minutes, it is discharged at a constant current of 1.0C to 2.5V. This process is repeated 800 times, that is, 800 charge-discharge cycles at a 1.0C rate. The discharge capacity of the 800th cycle / the discharge capacity of the 1st cycle is the capacity retention rate of the battery after 800 cycles at 1.0C.

[0268] The first discharge cycle capacity is as follows: 0.1C constant current charging to 4.5V, then constant voltage charging until the cutoff current equals 0.05C, and 0.1C discharge to the lower limit voltage of 2.5V.

[0269] 4. Calculation method for 0.1C volumetric energy density: 0.1C discharge capacity * average discharge voltage * electrode compaction density; Discharge capacity: Using a full cell at 2.5~4.5V, charge at 0.1C constant current to 4.5V, then continue charging at constant voltage until the cutoff current equals 0.05C, and discharge at 0.1C to the lower limit voltage of 2.5V. The capacity released per unit mass is the 0.1C discharge capacity; Discharge equalization voltage: Divide the integral area under the discharge curve by the discharge capacity to get the discharge equalization voltage.

[0270] 5. GITT test: The full cells prepared in Example 1 and Comparative Example 1 were subjected to GITT test.

[0271] The steps are as follows:

[0272] Step 1: Initial resting: Before testing, let the battery rest for 2 hours.

[0273] Step 2: Apply current pulse: Apply a 1C current (I, in the charging or discharging direction) for 10 minutes.

[0274] Record voltage transients: During the pulse, the voltage changes rapidly from the initial equilibrium voltage E_0. Record the voltage-time curve for the entire pulse period.

[0275] Step 3: Current Reset and Relaxation: Disconnect the current (I=0) and allow the battery to rest for 60 minutes. Observe the voltage relaxation over time until it stabilizes at a new equilibrium voltage E_s.

[0276] Repeat the cycle: Repeat steps 2-3 as a "titration" cycle until the battery reaches the set voltage endpoint. The voltage endpoint for charging is 4.5V, and the voltage endpoint for discharging is 2.5V.

[0277] The lithium-ion conductivity D was then calculated using the following formula. Li+ :

[0278] D=4 / πτ*((m BV M ) / (M B S))^2*((ΔE) s ) / (ΔE τ ))^2;

[0279] Where τ is the pulse time, S is the electrochemical active area, which is approximated here by the specific surface area of ​​the lithium-rich manganese-based cathode material, m B M B 、and V M These represent the mass, molar mass, and molar volume of the lithium-rich manganese-based cathode material, respectively; ΔE s ΔE represents the voltage change caused by the pulse. τ The voltage change caused by constant current charging or discharging.

[0280] Table 1

[0281]

[0282] Table 2

[0283]

[0284] Figure 1 and 2 Table 1 shows the XRD spectra of the lithium-rich manganese-based cathode materials obtained in Example 1 and Comparative Example 1, respectively. Table 2 shows the XRD-refined lattice parameters of the lithium-rich manganese-based cathode materials obtained in Example 1 and Comparative Example 1. Figure 1-2 As shown in Table 2, the interlayer spacing of alkali metals in the sample of Example 1 increased while the interlayer spacing of transition metals decreased, indicating that Mg element at least partially entered the Li layer, thus expanding the interlayer spacing. Figure 18 For the GITT test of Example 1 and Comparative Example 1, combined with Figure 18 It can be seen that the scheme in Example 1 can increase the interlayer spacing and improve the lithium-ion conductivity.

[0285] Figure 3 and Figure 4 The images shown are HRTEM images of the lithium-rich manganese-based cathode materials obtained in Example 1 and Comparative Example 1, respectively. Figure 3 This indicates that at least a portion of the surface of the cathode material obtained in Example 1 contains an in-situ LiF coating layer, wherein the LiF interplanar spacing is 0.2~0.205 nm, corresponding to its (200) crystal plane, indicating that at least a portion of the LiF coating layer exposes the (200) crystal plane, and its thickness is 6.5 nm. The layered structure of Example 1 exhibits good crystallinity. According to the appendix... Figure 17 It can be seen that the growth direction of the LiF coating layer (200) crystal plane is basically consistent with that of the core lithium-rich cathode material (003) crystal plane, and the angle between the two is <10°. They have lithium-ion transport layers with consistent direction, which can improve lithium-ion transport efficiency. According to Figure 4It can be seen that the lithium-rich manganese-based cathode material obtained in Comparative Example 1 does not have a LiF coating layer, but only a core lithium-rich cathode material.

[0286] Figure 5 and Figure 6 HRTEM images of the lithium-rich manganese-based cathode materials obtained after disassembling the full cells of Example 1 and Comparative Example 1 after 800 high-temperature cycles, respectively, for comparison. Figure 5-6 It can be seen that, due to the stabilizing effect of Mg on the alkali metal layer and the protective effect of surface LiF, the lithium-rich manganese-based cathode material of Example 1 still maintains a complete layered structure after 800 cycles at high temperature. Although the surface LiF shows a transformation to amorphous characteristics, the bulk structure has not changed significantly. A thin, uniform CEI layer with a thickness of less than 5 nm is formed on the surface. In contrast, the lithium-rich manganese-based cathode material of Comparative Example 1, after 800 cycles, shows severe degradation in its near-surface region, and even in the region extending 30 nm from the surface. The bulk region has transformed into spinel and rock salt phase regions over a large area. With the deterioration of the structure, the performance will be severely degraded.

[0287] Figure 7 The image shows the EPMA diagram of the lithium-rich manganese-based cathode material in Example 1. Figure 8 for Figure 7 The corresponding point scan detection results for Mg and F elements; Figure 9 EPMA image of a cross-section of a lithium-rich manganese-based cathode material; Figure 10 for Figure 9 The corresponding point scan detection results for Mg and F elements. Based on... Figures 7-10 It can be seen that Mg and F elements can be detected on the surface, while only Mg can be detected in the bulk phase, indicating that Mg is deeply doped into the bulk phase, while F exists on the surface.

[0288] Figure 11 The image shows the EPMA diagram of the lithium-rich manganese-based cathode material in Example 1. Figure 12 for Figure 11 The corresponding elemental distribution diagram of Mg; Figure 13 for Figure 11 The corresponding element distribution diagram of element F. Figure 14 Here is the EPMA image of the lithium-rich manganese-based cathode material in Example 5; Figure 15 for Figure 14 The corresponding elemental distribution diagram of Mg; Figure 16 for Figure 14 The corresponding element distribution diagram of element F. (From...) Figures 11-16 It can be seen that the secondary sintering temperature affects the uniformity of Mg and F distribution. In Example 1, there is no significant elemental segregation on the material surface, and it tends to be uniformly dispersed. Compared with Example 1, there are Mg and F agglomerates on the surface of the material in Example 5.

[0289] Table 3

[0290]

[0291]

[0292] Table 4

[0293]

[0294] As can be seen from Examples 1-19 and Comparative Examples 1-6 in Tables 3 and 4, the technical solution of this application, by doping Mg ions into the alkali metal layer of the lithium-rich manganese-based core material, can increase the interlayer spacing of the alkali metal layer, improve lithium-ion conductivity, enhance structural stability under deep delithiation conditions, increase Mn metal migration energy, and suppress spinel phase formation. The LiF coating layer can prevent direct contact between the cathode material and the electrolyte, thereby avoiding the formation of a low-conductivity byproduct layer due to direct contact between the cathode material and the electrolyte, improving the cathode interface stability, reducing electrolyte erosion of the surface layer, inhibiting metal dissolution, improving surface structural stability, and simultaneously increasing the lithium-ion migration coefficient.

[0295] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A lithium-rich manganese-based cathode material, characterized in that, It includes a lithium-rich manganese-based core material and a coating layer covering the lithium-rich manganese-based core material; The alkali metal layer of the lithium-rich manganese-based core material includes at least Mg, and the coating layer includes lithium fluoride.

2. The lithium-rich manganese-based cathode material according to claim 1, characterized in that, The lithium fluoride contains a (200) crystal plane; The angle between the lattice stripes of the (200) crystal plane of the lithium fluoride and the lattice stripes of the (003) crystal plane of the lithium-rich manganese-based core material is less than or equal to 10°.

3. The lithium-rich manganese-based cathode material according to claim 1, characterized in that, The d(Li-O-Li) spacing of the lithium-rich manganese-based cathode material is 2.590~2.600 Å.

4. The lithium-rich manganese-based cathode material according to any one of claims 1-3, characterized in that, The chemical formula of the lithium-rich manganese-based cathode material includes Li 1+x Ni a Co b Mn c M d Mg e O y F z R h , where a + b + c + d + e = 1.0, 0.1 ≤ a < 0.5, 0 ≤ b ≤ 0.15, 0.5 ≤ c ≤ 0.7, d ≤ 0.2, 0.10 ≤ x ≤ 0.5, 0 < e ≤ 0.015, 2.13 ≤ y ≤ 2.50, 0.006 ≤ z ≤ 0.03, 0.001 ≤ h ≤ 0.02; 1.95 + x ≤ y + z + h ≤ 2.05 + x, z + h ≤ 0.2y, M includes one or more of Al, P, Ca, Ti, Cr, Fe, Cu, Zn, Sr, Se, Y, Zr, Si, Nb, Mo, Sb, Sn, Te, Ba, Cs, Ta, W, La, Ce, Sm, and Gd, and R includes one or more of S, Cl, B, and C.

5. The lithium-rich manganese-based cathode material according to any one of claims 1-3, characterized in that, The thickness of the coating layer is 2nm-20nm, or the thickness of the coating layer is 2nm-14nm; and / or; The specific surface area of ​​the lithium-rich manganese-based cathode material is 0.3~3.0 m². 2 / g, or, the specific surface area of ​​the lithium-rich manganese-based cathode material is 1.4~1.8m². 2 / g.

6. The lithium-rich manganese-based cathode material according to any one of claims 1-3, characterized in that, The D50 of the lithium-rich manganese-based cathode material is 1.0 μm ≤ D50 ≤ 15.0 μm; or the D50 of the lithium-rich manganese-based cathode material is 6.5 μm ≤ D50 ≤ 12.2 μm. and / or; The coating layer also includes at least one element selected from La, Zr, Ba, and Cs.

7. A method for preparing a lithium-rich manganese-based cathode material according to any one of claims 1-6, characterized in that, The method includes the following steps: A metal salt solution, a precipitant, and a complexing agent are mixed and reacted to obtain a hydroxide precursor; the hydroxide precursor and a lithium source are mixed and subjected to a first sintering to obtain a cathode material intermediate; The cathode material intermediate and fluoride are mixed and subjected to a second sintering process to obtain the lithium-rich manganese-based cathode material, wherein the fluoride includes at least magnesium fluoride.

8. The method according to claim 7, characterized in that, A hydroxide precursor, a lithium source, and a modifying additive are mixed and subjected to a first sintering. The modifying additive includes a compound containing an element M, which includes one or more of Al, P, Ca, Ti, Cr, Fe, Cu, Zn, Sr, Se, Y, Zr, Si, Nb, Mo, Sb, Sn, Te, Ba, Cs, Ta, W, La, Ce, Sm, and Gd. The fluoride further includes fluoride I, which includes at least one of LaF3, ZrF4, BaF2, and CsF; and / or; the second sintering time is 2-5 hours; And / or; the heating rate of the second sintering is greater than or equal to 10℃ / min, or the heating rate of the second sintering is 10-15℃ / min; And / or; the second sintering temperature is 800~900℃.

9. A positive electrode plate, characterized in that, The electrode comprises a lithium-rich manganese-based cathode material according to any one of claims 1-6.

10. A battery, characterized in that, The battery includes the positive electrode according to claim 9.

Images