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

Abstract

The invention relates to the technical field of lithium batteries, and provides a lithium-rich manganese-based material and a preparation method thereof, a positive plate and a battery. The lithium-rich manganese-based material comprises a matrix and a shell layer, the outer surface of the base body is coated with the shell layer; the shell layer comprises a first shell layer and a second shell layer, and the first shell layer is located between the base body and the second shell layer; wherein the first shell layer comprises a P element; the second shell layer includes W element. According to the lithium-rich manganese-based material with the double-layer core-shell structure, the P element in the first shell layer and the W element in the second shell layer form a covalent bond, so that a more compact surface coating layer can be formed, the structural stability of the lithium-rich manganese-based material can be improved, the lithium-rich manganese-based material has a good water absorption prevention effect, and the gram volume and the cycle performance of a battery are improved.

Description

Technical Field

[0001] This invention relates to the technical field of lithium-ion batteries, specifically to a lithium-rich manganese-based material and its preparation method, a positive electrode sheet, and a battery. Background Technology

[0002] Lithium-ion batteries are rechargeable batteries with a history of over 20 years, and their applications span numerous fields including communications, transportation, military, medical, and entertainment. In recent years, with the rapid development of electric vehicles and other technologies, high-energy-density, high-power lithium-ion batteries have become the inevitable direction for future lithium-ion battery development. Currently, commercially available cathode materials mainly include LiCoO2, LiFePO4, LiMn2O4, and ternary materials, all of which have a specific capacity of less than 200 mAh / g. Cathode materials are the main factor limiting battery specific energy; therefore, to develop high-energy-density batteries, it is urgent to find cathode materials with higher specific capacity.

[0003] In recent years, lithium-rich materials, characterized by high capacity, low cost, and low toxicity, have become a research hotspot and hold promise as cathode materials for use in next-generation high-energy-density lithium-ion batteries. However, these lithium-rich materials have some inherent shortcomings, such as large initial irreversible capacity, poor rate performance, and voltage decay during cycling. These performance limitations restrict the application of lithium-rich materials as lithium-ion cathode materials. Summary of the Invention

[0004] The purpose of this invention is to overcome the aforementioned problems in the prior art and provide a lithium-rich manganese-based material and its preparation method, including a positive electrode and a battery containing the lithium-rich manganese-based material. This lithium-rich manganese-based material has a double-layer core-shell structure, where the phosphorus element in the first shell forms covalent bonds with the wylene element in the second shell, which helps to form a denser surface coating layer and improves the structural stability of the lithium-rich manganese-based material.

[0005] Furthermore, this lithium-rich manganese-based material has a double-layer core-shell structure, which can reduce the initial irreversible capacity of the battery and improve the specific capacity and cycle performance of the battery; in addition, the lithium-rich manganese-based material with a double-layer core-shell structure also has good water resistance.

[0006] To achieve the above objectives, a first aspect of the present invention provides a lithium-rich manganese-based material comprising a matrix and a shell; the shell covers the outer surface of the matrix; the shell comprises a first shell and a second shell, the first shell being located between the matrix and the second shell; wherein the first shell comprises phosphorus (P); and the second shell comprises sulfur (W).

[0007] The second aspect of the present invention provides a method for preparing the lithium-rich manganese-based material described in the first aspect of the present invention, comprising the following steps: coating the outer surface of a substrate with a first shell layer, then coating it with a second shell layer, and sintering to obtain the lithium-rich manganese-based material; preferably, the first shell layer comprises phosphorus (P); preferably, the second shell layer comprises phosphorus (W).

[0008] A third aspect of the present invention provides a positive electrode sheet comprising the lithium-rich manganese-based material described in the first aspect of the present invention, or the lithium-rich manganese-based material prepared by the preparation method described in the second aspect of the present invention.

[0009] A fourth aspect of the present invention provides a battery comprising the lithium-rich manganese-based material described in the first aspect of the present invention, or comprising the positive electrode sheet described in the third aspect of the present invention.

[0010] The present invention, by adopting the above technical solution, has the following beneficial effects:

[0011] (1) The lithium-rich manganese-based material provided by the present invention is a lithium-rich manganese-based material with a double core-shell structure. The P element in the first shell layer and the W element in the second shell layer form a covalent bond, which helps to form a denser surface coating layer, improves the structural stability of the lithium-rich manganese-based material, reduces interfacial impedance, improves the conductivity of the lithium-rich manganese-based material, and reduces electrolyte side reactions. Furthermore, the lithium-rich manganese-based material with the double core-shell structure can reduce the initial irreversible capacity of the battery and improve the specific capacity and cycle performance of the battery. The lithium-rich manganese-based material with the double core-shell structure also has good water resistance.

[0012] (2) The positive electrode provided by the present invention can provide a high capacity utilization, and has the advantages of low first-cycle irreversible capacity and good cycle performance.

[0013] (3) The battery provided by the present invention has good specific capacity and cycle performance, and can provide high capacity performance.

[0014] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and should be understood to include values ​​close to those ranges or values. For numerical ranges, endpoint values ​​of various ranges, endpoint values ​​of various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein. In this document, unless otherwise specified, data ranges include endpoints. Attached Figure Description

[0015] Figure 1 The diagram shown is a schematic diagram of the lithium-rich manganese-based material with a double core-shell structure in Example 1-1.

[0016] Figure 2The image shows the EDS cross-sectional scan results of the lithium-rich manganese-based material with a double core-shell structure in Example 1-1.

[0017] Figure 3 The XRD test results of the lithium-rich manganese-based materials of Example 1-1 and Comparative Example 1 are shown.

[0018] Figure 4 The figure shows the dQ / dV curves of the lithium-rich manganese-based material with a double core-shell structure in Example 1.

[0019] Figure 5 The first charge-discharge curves (2.0-4.6V) of Example 1 and Comparative Example 1 are shown.

[0020] Figure 6 The diagram shows the charge-discharge cycle diagrams of Example 1 and Comparative Example 1 at 2.0–4.6V and 0.5C. Detailed Implementation

[0021] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0022] Unless otherwise defined, all scientific and technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art.

[0023] Lithium-rich materials suffer from drawbacks such as large initial irreversible capacity, poor rate performance, and voltage decay during cycling. These shortcomings primarily stem from the Li₂MnO₃ component within these materials. Although the activation energy of Li₂MnO₃ contributes additional capacity, its activation during the initial charge is often accompanied by irreversible oxidation of O and oxygen evolution, leading to the degradation of Li₂MnO₃. + Irreversible insertion / extraction is the main reason for the low initial coulombic efficiency of lithium-rich materials. Moreover, the activated Li2MnO3 component will continuously transform into a spinel-like structure during subsequent cycles, which will also lead to a continuous decrease in its operating voltage; and the relatively low electrical and ionic conductivity of Li2MnO3 is also detrimental to the rate performance of lithium-rich materials. All of these factors severely restrict the performance of lithium-rich materials to a certain extent.

[0024] To overcome the shortcomings in the application of lithium-rich materials, this invention provides the following technical solution:

[0025] The first aspect of the present invention provides a lithium-rich manganese-based material, comprising a matrix and a shell; the shell covers the outer surface of the matrix; the shell comprises a first shell and a second shell, the first shell being located between the matrix and the second shell; wherein the first shell comprises phosphorus (P); and the second shell comprises sulfur (W).

[0026] In this invention, on the one hand, high-valence phosphorus (P) in the first shell of the lithium-rich manganese-based material substitutes for Li sites in the precursor. Simultaneously, under the action of ion diffusion, P also diffuses from the shell into the matrix, improving the structural stability of the precursor. Furthermore, PO exhibits strong stability, effectively suppressing O points and defects, which is beneficial for inhibiting the generation and release of O2, thus improving the structural stability of the lithium-rich manganese-based material, reducing interfacial impedance, and stabilizing the surface structure. On the other hand, in the second shell, W, as the main surface coating element, can form a denser surface coating layer. The second shell, which is less prone to detachment during subsequent processing, isolates the electrolyte from direct contact with the active electrode material, significantly reducing a series of side reactions (such as reducing transition metal deposition, forming a thinner SEI film, and reducing oxygen atom deposition), thereby improving the electrochemical stability of lithium-rich manganese-based materials. Furthermore, the presence of silicon (W) is beneficial for increasing ion transport rates. Additionally, since the relatively high residual alkali content on the surface of lithium-rich materials affects material properties, gas generation, and water absorption, the second shell isolates the surface of the lithium-rich manganese-based material from air, providing a good anti-water absorption effect. Overall, the covalent bonds formed between the phosphorus (P) element in the first shell and the silicon (W) element in the second shell contribute to the formation of a denser surface coating, reducing side reactions and improving the structural stability and anti-water absorption effect of the double-core-shell structure of lithium-rich manganese-based materials.

[0027] Furthermore, coating the surface of lithium-rich manganese-based materials with a double shell (i.e., a first shell and a second shell) can alleviate the structural collapse caused by volume changes due to lithium delithiation / lithiation during charging and discharging. Doping can reduce cation mixing and improve the stability of the layered structure of lithium-rich manganese-based materials. It can also broaden the diffusion channels of lithium ions, improve the conductivity of lithium-rich manganese-based materials, reduce the initial irreversible capacity of the battery, and improve the specific capacity and cycle performance of the battery.

[0028] The shell covers the outer surface of the substrate. It can be completely covered or at least partially covered. Full coverage is preferred, as it can better enhance the protective effect of the shell and improve the stability and electrochemical performance of lithium-rich manganese-based materials.

[0029] In some embodiments, the phosphorus (P) content in the first shell is ≥50%, and the w (W) content in the second shell is ≥50%. A P content of ≥50% in the first shell can be understood as: in the first shell, if the content of all elements is 100%, the P content accounts for ≥50%. Similarly, a W content of ≥50% in the second shell can be understood as: in the second shell, if the content of all elements is 100%, the W content accounts for ≥50%.

[0030] In this invention, the element content is a mass content, which can be obtained by conventional methods in the art, such as energy dispersive spectroscopy (EDS) and inductively coupled plasma optical emission spectrometry (ICP-OES).

[0031] In some embodiments, the phosphorus (P) content in the first shell can be 50%, 52%, 55%, 60%, 65%, 70%, 75%, 80%, or 85%. Preferably, the P content in the first shell is 60-85%. When the P content is within the above range, the higher content of high-valence P doping results in more polarization states in the lithium-rich manganese-based material, which can further improve the conductivity of the lithium-rich manganese-based material, further suppress O-points and defects, and improve the structural stability of the lithium-rich manganese-based material.

[0032] In some embodiments, the W content in the second shell can be 50%, 52%, 55%, 60%, 65%, 70%, 75%, 80%, or 85%. Preferably, the W content in the second shell is 60-85%. When the W content is within the above and preferred ranges, the density of the second shell can be further improved, which is more conducive to reducing side reactions of the electrolyte, improving the electrochemical stability of lithium-rich manganese-based materials, and improving the water-resistant effect of lithium-rich manganese-based materials.

[0033] In some embodiments, the phosphorus (P) content in the shell is greater than the w (W) content. Limiting the P content to be greater than the W content in the shell can better enhance the shell's ability to suppress irreversible oxidation of oxygen and oxygen evolution, further improving the structural stability of lithium-rich manganese-based materials.

[0034] In some embodiments, the chemical formula of the lithium-rich manganese-based material is Li. 1+q Ni x Co y Mn z M uO2, where M includes one or more of Mg, Al, P, Nb, Y, Ti, Zr, Sn, W, and V, and 0 < q ≤ 1, 0.2 ≤ x ≤ 0.45, 0.02 ≤ y ≤ 0.20, 0.35 ≤ z ≤ 0.78, and 0 < u ≤ 0.2. In the chemical formula of lithium-rich manganese-based materials, x, y, z, u, and q satisfy valence equilibrium, for example, x + y + z + u = 1 - q. When lithium-rich manganese-based materials satisfy the above chemical properties, they have high capacity.

[0035] In some embodiments, the first shell layer comprises an oxide containing phosphorus (P), including: oxides containing only P, oxides containing P and other dopants, lithium oxides containing P, and lithium oxides containing P and other dopants, etc., where the dopants include one or more of Mg, Al, Nb, Y, Ti, Zr, Sn, W, and V. Exemplarily, the first shell layer comprises lithium phosphate, or a mixture of lithium phosphate and other phosphates (e.g., aluminum phosphate, magnesium phosphate, etc.).

[0036] In some embodiments, the second shell layer includes an oxide containing the element W. The oxide containing W includes: oxides containing only W, oxides containing W and other doped elements, lithium oxides containing W, and lithium oxides containing W and other doped elements. The doped elements include one or more of Mg, Al, P, Nb, Y, Ti, Zr, Sn, and V. For example, the second shell layer includes tungsten oxide, lithium tungstate, etc.

[0037] In some embodiments, XRD testing reveals that the lithium-rich manganese-based material exhibits a first diffraction peak at 2θ = 17-19°, with peak intensity denoted as I1, and a second diffraction peak at 2θ = 43-46°, with peak intensity denoted as I2. The ratio of I1 to I2 satisfies: 1.1 ≤ I1 / I2 ≤ 2. For example, the ratio of I1 to I2 can be 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2.0. The crystal plane corresponding to the first diffraction peak is (003), and the crystal plane corresponding to the second diffraction peak is (104). When the ratio of I1 to I2 is within the above range, the layered structure exhibits good stability, which can improve the cycle stability of the lithium-rich manganese-based material. This is because an appropriate proportion of Li / Ni mixture can effectively prevent the migration of transition metals to the Li layer under high delithiation state, and the Ni layer is slightly passivated by the lithium layer. 2+ This effectively increases the Li layer spacing, avoids the shrinkage of the Li layer under high delithiation state, and can effectively improve the rate performance and long-cycle stability of lithium-rich manganese-based materials.

[0038] Furthermore, based on the double-core-shell structure of lithium-rich manganese-based materials, which includes a first shell containing P and a second shell containing W, adjusting the ratio of I1 to I2 in the XRD test of lithium-rich manganese-based materials can better improve the cycle stability of lithium-rich manganese-based materials and further improve the cycle performance of batteries.

[0039] In some embodiments, the dQ / dV curve of the lithium-rich manganese-based material is tested, and the peak intensity in the range of 3V-4.2V is denoted as I. a The peak intensity in the range of 4.3V-4.7V is denoted as I. b I a with I b The ratio satisfies: 4≤I a / I b Ni is used in the range of ≤12.3V-4.2V. 2+ / Ni 4+ The oxidation peak is located in the range of 4.3V-4.7V, which is the oxidation peak of lattice oxygen. a with I b The ratio can be, for example, 4, 5, 6, 7, 8, 9, 10, 11, or 12, preferably 6 ≤ I. a / I b ≤10. In the dQ / dV curves of lithium-rich manganese-based materials, the value of Ni is ≤10 in the range of 3-4.2V. 2+ / Ni 4+ The oxidation peak corresponds to the preferential participation of transition metals in the reaction at low potentials. A significant oxidation peak of lattice oxygen appears in the 4.3-4.7V range. It is precisely because of the oxidation of lattice oxygen and the joint participation of transition metal ions in the redox reaction that high discharge capacity can be provided for lithium-rich manganese-based materials. The presence of a P and W double-shell can fill O vacancies, restrict O removal, reduce the initial irreversible capacity of the battery, and control Ig. a with I b A value between 4 and 12 can balance high capacity and structural stability.

[0040] Furthermore, based on the double-shell structure of lithium-rich manganese-based materials, which includes a first shell containing P and a second shell containing W, the I in the dQ / dV curve of the lithium-rich manganese-based material is further adjusted. a / I b2 The ratio of [value] can better suppress O-points and defects, improve the structural stability of lithium-rich manganese-based materials, and further improve the specific capacity and cycle performance of batteries.

[0041] In some embodiments, the porosity of the matrix is ​​lower than that of the shell. A lower matrix porosity allows the electrolyte to penetrate more easily into the active material, thereby improving the battery's charge / discharge efficiency. A relatively higher shell porosity reduces side reactions between the lithium-rich manganese-based material and the electrolyte, improving the structural stability of the lithium-rich manganese-based material.

[0042] In some embodiments, the porosity of the matrix is ​​8-30%, for example, it can be 8%, 10%, 12%, 15%, 18%, 20%, 22%, 25%, 28%, 30%, preferably 15-30%. When the porosity of the matrix is ​​within the above range, the loose core matrix can provide good buffer space during the actual compaction process, avoiding particle breakage caused by close contact of particles, and can make it easier for the electrolyte to penetrate into the active material, thereby improving the charge and discharge efficiency of the battery, taking into account both electrochemical and industrial production considerations.

[0043] In some embodiments, the porosity of the shell is 3-10%, for example, it can be 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10%, preferably 5-8%. When the porosity of the shell is within the above range, the porosity of the shell is less than that of the matrix, which can avoid the erosion of the lithium-rich manganese-based material by the electrolyte during long-term cycling and reduce the side reactions of the electrolyte.

[0044] Furthermore, based on the double-core-shell structure of lithium-rich manganese-based materials, which includes a first shell containing P and a second shell containing W, further adjustments to the porosity of the lithium-rich manganese-based material matrix and the porosity of the shell can better reduce side reactions between the lithium-rich manganese-based material and the electrolyte, improve the charge and discharge efficiency of the battery, further enhance the water-resistant effect of the lithium-rich manganese-based material, and improve the structural stability of the lithium-rich manganese-based material.

[0045] like Figure 1 and Figure 2 As shown, the lithium-rich manganese-based material has a relatively loose matrix core structure 1, a first shell layer 2, and a second shell layer 3. The matrix core structure has a large number of micropores. The core-shell structure of the lithium-rich manganese-based material consists of spherical particles with a dense outer layer and a loose inner layer. The dense shell layer can prevent air erosion and electrolyte erosion during long-term cycling, avoiding severe interfacial side reactions. The loose matrix layer provides a good buffer space to reduce particle breakage. This comprehensively improves the structural stability and electrochemical performance of the lithium-rich manganese-based material.

[0046] In some embodiments, the surface of the lithium-rich manganese-based material has a microporous structure with pore sizes ranging from 5 nm to 300 nm. This microporous structure can increase the diffusion rate of ions in the electrolyte and reduce the diffusion path of ions on the electrode surface, thereby improving the charge and discharge rate of the battery.

[0047] In some embodiments, the thickness of the first shell layer is 0.5 μm-4 μm, for example, it can be 0.5 μm, 1 μm, 2 μm, 3 μm, or 4 μm, preferably 1 μm-3 μm. When the thickness of the first shell layer is within the above range, the amount of high-valence P doping can be higher, thereby better suppressing O points and defects and improving the structural stability of lithium-rich manganese-based materials; and doping also allows lithium-rich manganese-based materials to generate more polarization states, which is beneficial to lithium ion transport and improves the conductivity of lithium-rich manganese-based materials.

[0048] In some embodiments, the thickness of the second shell layer is 10nm-1000nm, for example, it can be 10nm, 100nm, 200nm, 300nm, 400nm, 500nm, 600nm, 700nm, 800nm, 900nm, or 1000nm, preferably 200nm-800nm. When the thickness of the second shell layer is within the above range, a suitable and dense surface coating layer can be formed on the surface of the lithium-rich manganese-based material, improving the electrochemical stability and water-resistant effect of the lithium-rich manganese-based material.

[0049] In some embodiments, the lithium-rich manganese-based material satisfies one or more of the following conditions:

[0050] (a) The lithium-rich manganese-based material is a polycrystalline material, and the average particle size of the primary particles of the lithium-rich manganese-based material is 50 nm to 200 nm.

[0051] (b) The lithium-rich manganese-based material has Dv10 = 2 μm to 8 μm, Dv50 = 5 μm to 20 μm, and Dv90 = 10 μm to 30 μm;

[0052] (c) The specific surface area of ​​the lithium-rich manganese-based material is 1 m². 2 / g-5m 2 / g, preferably 1.5m 2 / g-4m 2 / g;

[0053] (d) The true density of the lithium-rich manganese-based material is 3.5 g / cm³. 3 -4.5g / cm 3 ;

[0054] (e) The compaction density of the lithium-rich manganese-based material is 2.7 g / cm³. 3 ~3.50g / cm 3 .

[0055] The lithium-rich manganese-based material can satisfy any one or more of (a)-(e), preferably all of the conditions.

[0056] In some embodiments, the lithium-rich manganese-based material is a polycrystalline material with an average primary particle size of 50 nm to 200 nm, preferably Dv50 = 55 nm to 150 nm. Smaller primary particles can increase the contact area between the lithium-rich manganese-based material and the electrolyte, effectively shortening the lithium-ion diffusion path and giving the lithium-rich manganese-based material better electrochemical performance. In this invention, "average particle size" refers to the numerical average particle size, which is the average value of all particle sizes. For example, in electron microscopy images, the morphology and size of the particles are observed through an electron microscope, and then multiple particles are measured using image analysis software to calculate the numerical average particle size.

[0057] Furthermore, based on the double-core-shell structure of lithium-rich manganese-based materials, which includes a first shell containing P and a second shell containing W, adjusting the primary particle size of the core lithium-rich manganese-based material can further improve the conductivity, specific capacity, and cycle performance of the lithium-rich manganese-based material.

[0058] In some embodiments, the lithium-rich manganese-based material has a particle size distribution of Dv10 = 2 μm to 8 μm, Dv50 = 5 μm to 20 μm, and Dv90 = 10 μm to 30 μm. Preferably, the lithium-rich manganese-based material has a particle size distribution of Dv10 = 3 μm to 5 μm, Dv50 = 8 μm to 12 μm, and Dv90 = 15 μm to 20 μm. When the lithium-rich manganese-based material meets the above particle size distribution, it can have a relatively high compaction density and a high specific capacity.

[0059] Furthermore, by adjusting the particle size distribution of lithium-rich manganese-based materials, which include a first shell containing P and a second shell containing W, the specific capacity of lithium-rich manganese-based materials can be further improved.

[0060] In some embodiments, the specific surface area of ​​the lithium-rich manganese-based material is 1 m². 2 / g-5m 2 / g, preferably 1.5m 2 / g-4m 2 / g. Lithium-rich manganese-based materials exhibit good sphericity when the specific surface area (BET value) is within the above range. Excessively large BET values ​​make it easier for the slurry to absorb water, which affects battery fabrication.

[0061] Furthermore, by adjusting the specific surface area of ​​lithium-rich manganese-based materials, which include a first shell containing phosphorus (P) and a second shell containing potassium (W), the water-resistant properties of these materials can be further improved.

[0062] In some embodiments, the true density of the lithium-rich manganese-based material is 3.5 g / cm³. 3 -4.5g / cm3 4.0g / cm 3 -4.3g / cm 3 True density can be tested using the impregnation method or the gas volume method. When the true density of lithium-rich manganese materials is within the above range, lithium-rich manganese-based materials exhibit high energy density and good electronic conductivity.

[0063] Furthermore, by adjusting the true density of lithium-rich manganese-based materials, which include a first shell containing P and a second shell containing W, the conductivity and energy density of these materials can be further improved.

[0064] In some embodiments, the compaction density of the lithium-rich manganese-based material is 2.7 g / cm³. 3 ~3.5g / cm 3 Preferred concentration: 2.8g / cm³ 3 ~3.20g / cm 3 When the compaction density of lithium-rich manganese-based materials is within the above-mentioned range, the uniform distribution and dense packing of active materials in the lithium-rich manganese-based materials can be ensured, thereby improving the capacity and energy density of the electrode.

[0065] Furthermore, by adjusting the compaction density of lithium-rich manganese-based materials, which include a first shell containing P and a second shell containing W, the energy density of these materials can be further improved.

[0066] A second aspect of the present invention provides a method for preparing the lithium-rich manganese-based material described in the first aspect of the present invention, comprising the following steps: coating the outer surface of a substrate with a first shell layer, then coating it with a second shell layer, and sintering to obtain the lithium-rich manganese-based material. Preferably, the first shell layer comprises phosphorus (P); preferably, the second shell layer comprises silicon (W).

[0067] In some embodiments, the method for preparing the lithium-rich manganese-based material specifically includes the following steps:

[0068] (1) Matrix preparation: Nickel source, cobalt source, manganese source and optionally doped metal source are prepared into salt solution in proportion, and then mixed with alkaline solution to carry out the first reaction;

[0069] (2) First shell coating: The first additive is added to the material obtained in step (1) to carry out the second reaction; the first additive includes a soluble salt containing the element P;

[0070] (3) Second shell coating: The second additive is added to the material obtained in step (2) and a third reaction is carried out to obtain the precursor; the second additive includes a soluble salt containing W element;

[0071] (4) Sintering to prepare lithium-rich manganese-based materials: The precursor obtained in step (4) is mixed with the lithium source in a certain proportion and then subjected to a high-temperature solid-phase reaction.

[0072] Step (1)

[0073] In step (1), the matrix is ​​a lithium-rich manganese-based material. The reactants include a nickel source, a cobalt source, a manganese source, and optionally a doped metal source. The doped metal source may or may not be added, depending on the specific requirements. The nickel source, cobalt source, manganese source, and doped metal source are soluble metal salts that provide Ni, Co, Mn, or the doped metal source, respectively. For example, they can be one or more of the following: acetate, sulfate, chloride, nitrate, phosphate, pyrophosphate, and tungstate containing the corresponding metal element. Preferably, the concentration of the soluble metal salt is 1-3 mol / L.

[0074] In some embodiments, the nickel source includes nickel sulfate hexahydrate, nickel nitrate, and nickel chloride; the cobalt source includes cobalt sulfate heptahydrate, cobalt nitrate, and cobalt chloride; and the manganese source includes manganese sulfate monohydrate, manganese nitrate, and manganese chloride.

[0075] In some embodiments, the molar ratio of Ni:Co:Mn in the nickel source, cobalt source, and manganese source is (25-35):(5-15):(50-80).

[0076] In some embodiments, the alkaline solution is one or both of hydroxides and carbonates. Preferably, the concentration of the alkaline solution is 1-3 mol / L.

[0077] In some embodiments, the alkaline solution also includes a complexing agent, which may include one or more of ammonia, ammonium oxalate, and ammonium citrate. Preferably, 10g to 20g of complexing agent is added per 1L of alkaline solution. In the process of preparing lithium-rich manganese-based materials, nickel, cobalt, and manganese sources typically react with the complexing agent in the alkaline solution to form corresponding hydroxide precipitates or complex precipitates.

[0078] In some embodiments, the conditions for the first reaction include: a reaction temperature of 20-60°C; a reaction pH of 7-12; and a reaction stirring speed of 300-1500 rpm.

[0079] Step (2)

[0080] The purpose of step (2) is to coat the surface of the material obtained in step (1) (i.e., the hydroxide precipitate) with a first shell containing phosphorus (P). The first additive includes a soluble salt containing P, such as one or both of phosphates and pyrophosphates containing P. The first additive may also optionally include soluble salts of other doped metal elements, such as, but not limited to, one or more soluble salts of Mg, Al, Nb, Y, Ti, Zr, Sn, and V. Exemplarily, the first additive includes sodium dihydrogen phosphate, ammonium dihydrogen phosphate, lithium phosphate, ammonium hydrogen phosphate, etc.

[0081] In some embodiments, the amount of the first additive added per 1000g of precursor is 10g to 20g. Limiting the amount of the first additive can control the phosphorus content in the first shell layer within a suitable range, ensuring that phosphorus plays its role in improving the structural stability of lithium-rich manganese-based materials.

[0082] In some embodiments, the conditions for the second reaction include: a reaction temperature of 20-60°C; a reaction pH of 7-12; and a reaction stirring speed of 300-1500 rpm.

[0083] Step (3)

[0084] The purpose of step (3) is to coat the surface of the material obtained in step (2) with a second shell containing W, that is, to coat the outer surface of the first shell with a second shell. The second additive includes a soluble salt containing W, such as tungstate containing W. The second additive may also optionally include soluble salts of other doped metal elements, such as, but not limited to, soluble salts of one or more of Mg, Al, Nb, Y, Ti, Zr, Sn, P, and V. Exemplarily, the second additive includes lithium tungstate, tungsten oxide, ammonium tungstate, and ammonium metatungstate.

[0085] In some embodiments, the amount of the second additive added per 1000g of precursor is 5-20g. Limiting the amount of the second additive can control the W element content in the second shell within a suitable range, ensuring the formation of a denser surface coating layer and improving the water-resistant effect of the second shell.

[0086] In some embodiments, the conditions for the third reaction include: a reaction temperature of 20-60°C; a reaction pH of 7-12; and a reaction stirring speed of 300-1500 rpm.

[0087] In some embodiments, the time interval between the addition of the second additive and the first additive is greater than 6 hours, preferably greater than 12 hours. A time interval of more than 6 hours between the addition of the second additive and the first additive can ensure that the first shell layer and the second shell layer form a clear double-layer coating structure, avoiding the formation of a mixed coating layer due to too short an interval. Compared with mixed coating, double-layer coating can better improve the structural temperature stability and water-resistant effect of lithium-rich manganese-based materials.

[0088] In some embodiments, after the second shell coating, the process further includes aging, washing, drying, and sieving. The aging time is 1-30 hours. Aging reduces impurities and structural defects in the lithium-rich manganese-based material, improving material purity and consistency, and enhancing battery cycle stability and conductivity. Washing is performed 3-10 times, using a vacuum filtration system to remove impurities. Drying includes oven drying at 70°C-150°C, with the drying time adjusted according to the drying conditions, for example, 10-36 hours. Sieving is performed with a mesh size of approximately 400 mesh to select lithium-rich manganese-based materials within a suitable particle size range.

[0089] In some embodiments, the precursor Dv50 is 8 μm to 14 μm; when the precursor Dv50 is within the above range, lithium-rich manganese-based materials with suitable particle size can be obtained, so that the lithium-rich manganese-based materials have relatively high compaction density and high specific capacity.

[0090] In some embodiments, the primary particles of the precursor have a Dv50 of 50 nm to 300 nm, and the secondary particles of the precursor have a Dv50 of 6 nm to 11 μm. The smaller particle size of the primary particles of the precursor can increase the contact area with the electrolyte, effectively shorten the lithium-ion diffusion path, and improve the electrochemical performance of lithium-rich manganese-based materials; the smaller particle size of the secondary particles can increase the compaction density of lithium-rich manganese-based materials.

[0091] Step (4)

[0092] The purpose of step (4) is to decompose, recrystallize and transform the precursor through high-temperature solid-state reaction, and finally generate lithium-rich manganese-based material with a double-layer coating structure.

[0093] In some embodiments, the mass ratio of the precursor to the lithium source is 1:(3-6), for example, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6, and more preferably 1:(4-5). The lithium source includes lithium carbonate, lithium hydroxide, etc. When the mass ratio of the precursor to the lithium source is within the above range, lithium-rich manganese-based materials with high capacity, good rate performance, and long cycle life can be prepared.

[0094] In some embodiments, the high-temperature solid-state reaction includes sintering at a first temperature and sintering at a second temperature, where the first temperature is lower than the second temperature. Preferably, the first temperature is 450°C to 600°C, and the first holding time is 4 to 8 hours; and / or, the second temperature is 750°C to 1000°C, and the second holding time is 12 to 20 hours. During the high-temperature solid-state reaction, a large amount of carbon dioxide is generated during sintering at the first temperature (medium-temperature plateau). Performing sintering at the first temperature followed by sintering at the second temperature can reduce the porosity of the lithium-rich manganese-based material and improve its morphology.

[0095] In some embodiments, the atmosphere used for the high-temperature solid-state reaction includes one or more of oxygen, compressed air, nitrogen, argon, and carbon dioxide, with compressed air replenished at a rate of 1 L to 50 L / min per cubic meter of space. Preferably, the atmosphere used for the high-temperature solid-state reaction includes air, with compressed air replenished at a rate of 30 L to 40 L / min per cubic meter of space. When the gas replenishment rate is within the above range, it will increase the redox reaction rate in the high-temperature solid-state reaction, promote uniform grain growth, and result in lithium-rich manganese-based materials with better crystallinity and smaller particle size, thereby improving the electrochemical performance of lithium-rich manganese-based materials.

[0096] A third aspect of the present invention provides a positive electrode sheet comprising the lithium-rich manganese-based material described in the first aspect of the present invention, or the lithium-rich manganese-based material prepared by the preparation method described in the second aspect of the present invention.

[0097] In some embodiments, the compaction density of the positive electrode is 2.7 g / cm³. 3 ~3.5g / cm 3 Preferred concentration: 2.8g / cm³ 3 ~3.20g / cm 3 When the compaction density of the cathode sheet is within the above-mentioned range, the utilization rate of lithium-rich manganese-based materials and the energy density of the battery can be improved. Furthermore, by adjusting the compaction density of the cathode sheet based on the double-layer core-shell structure of the lithium-rich manganese-based material, which includes a first shell containing phosphorus (P) and a second shell containing potassium (W), the energy density of the battery can be further improved.

[0098] In some embodiments, the positive electrode sheet includes a positive current collector and a positive active material layer disposed on at least one surface of the positive current collector. The positive active material layer includes the aforementioned double-shell-coated lithium-rich manganese-based material, and further includes a conductive agent and a binder. The positive current collector includes, but is not limited to, aluminum, aluminum alloys, nickel, nickel alloys, titanium, and titanium alloys. The conductive agent includes at least one selected from conductive carbon black (SP), acetylene black, Ketjen black, graphene, conductive carbon fiber, 350G, carbon nanotubes (CNTs), metal powder, and carbon fiber; the binder includes at least one selected from sodium carboxymethyl cellulose, styrene-butadiene rubber (SBR), polytetrafluoroethylene, and polyethylene oxide.

[0099] A fourth aspect of the present invention provides a battery comprising the lithium-rich manganese-based material described in the first aspect of the present invention, or comprising the positive electrode sheet described in the third aspect of the present invention.

[0100] In some embodiments, the battery further includes an electrolyte; the electrolyte includes a non-aqueous organic solvent, a conductive lithium salt, and additives. Preferably, the non-aqueous organic solvent includes at least one of cyclic carbonates and at least one of linear carbonates and linear carboxylic acid esters. Preferably, the conductive lithium salt includes one or more of lithium hexafluorophosphate, lithium bis(fluorosulfonyl)imide, lithium bis(trifluoromethyl)sulfonylimide, lithium difluorophosphate, lithium tetrafluoroborate, lithium hexafluoroantimonyate, lithium hexafluoroarsenate, lithium difluorooxalateborate, lithium tetrafluorooxalate phosphate, lithium difluorobis(oxalate)phosphate, lithium bis(oxalate)borate, lithium 4,5-dicyano-2-trifluoromethyl-imidazolium lithium, lithium di(trifluoromethyl)imide, lithium di(pentafluoroethyl)imide, lithium tri(trifluoromethyl)methyl, and lithium di(trifluoromethyl)imide. Preferably, the additives include one or more of nitrile compounds, vinylene carbonate, and 1,3-propenesulfonyl lactone.

[0101] In some embodiments, the battery further includes a negative electrode sheet. The negative electrode sheet includes a negative current collector and a layer of negative active material coated on one or both surfaces of the negative current collector. The negative current collector includes copper, stainless steel, aluminum, nickel, titanium, carbon cloth, or a composite of these materials. The negative active material layer includes a negative active material, a conductive agent, and a binder. Preferably, the negative active material includes at least one of artificial graphite, natural graphite, hard carbon, mesophase carbon microspheres, lithium titanate, silicon carbide, silicon suboxide, and silicon alloys.

[0102] In some embodiments, the battery further includes a separator. Preferably, the separator substrate comprises polypropylene, for example, a coated polypropylene separator having a ceramic layer coated on one or both sides of a polypropylene substrate. The ceramic material in the ceramic layer includes, but is not limited to, one or more of CeO2, MgAl2O4, ZrO, and TiO2.

[0103] The battery provided by this invention has good specific capacity and cycle performance, and can provide high capacity utilization.

[0104] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0105] Unless otherwise specified, all materials and reagents used in the following examples are commercially available. The invention is described in detail below with reference to specific embodiments, which are intended to understand but not limit the invention. The batteries in the examples and comparative examples were prepared according to the following methods.

[0106] Example 1-1:

[0107] 1. Preparation of positive electrode sheet: Lithium-rich manganese-based material, conductive agent acetylene black, and binder PVDF (polyvinylidene fluoride) are thoroughly mixed in an N-methylpyrrolidone solvent system at a mass ratio of 90:5:5. The mixture is then coated onto aluminum foil, dried, and cold-pressed to form the corresponding positive electrode sheet. The preparation method of the lithium-rich manganese-based material is as follows:

[0108] (1) Weigh out nickel sulfate hexahydrate, cobalt sulfate heptahydrate, and manganese sulfate monohydrate in the molar ratio (Ni:Co:Mn=30:8:62). Prepare a salt solution with a concentration of 2 mol / L for Ni+Co+Mn and an alkaline solution with a concentration of 2 mol / L for sodium carbonate. Add the salt and alkaline solutions to the reactor through a peristaltic pump. After the reaction reaches the target particle size (Dv50=8μm~14μm), add the first additive sodium dihydrogen phosphate and stir continuously for more than 12 hours. Then add the second additive tungsten oxide and stir continuously for more than 12 hours. Then age for 24 hours, filter, and dry in a forced-air oven at 130℃ for 24 hours. Pass through a 400-mesh sieve to obtain the precursor.

[0109] (2) The obtained precursor and battery-grade lithium carbonate were mixed in a mass ratio of precursor: lithium carbonate = 1:0.45. After the mixture was uniform, it was packed into a sintering pan and sintered. The sintering temperature curve was divided into two plateaus. The middle plateau was sintered at 550℃ for 6 hours and the high-temperature plateau was sintered at 800℃ for 16 hours. After sintering, the material was dried to obtain lithium-rich manganese-based material, which was then packaged and stored in a dry environment.

[0110] from Figure 3 It can be seen that, after XRD testing, the peak intensity of the first diffraction peak in the range of 2θ = 17-19° of the lithium-rich manganese-based material is I1, and the peak intensity of the second diffraction peak in the range of 2θ = 43-46° is I2, with a ratio of I1 to I2 of 1.4. The lithium-rich manganese-based material has a superlattice oxidation peak at around 2θ = 20°, which is a specific XRD peak position that appears in the lithium-rich manganese-based material.

[0111] from Figure 4 The dQ / dV curves show that the lithium-rich manganese-based material of Example 1 (i.e., Example 1-1) exhibits a significant oxidation peak of lattice oxygen in the 4.3-4.7V range, providing a high discharge capacity for the lithium-rich manganese-based material. From... Figure 5It can be seen that the coin cell of Example 1 has a higher specific capacity. From Figure 6 It can be seen that the curve of Example 1 (i.e. Example 1-1) is relatively more stable in the overall cycle, and the capacity retention rate of Example 1 has a certain advantage in terms of relative capacity.

[0112] The lithium-rich manganese-based material obtained above is used to prepare a positive electrode sheet and assembled into a battery, which is carried out by the following method:

[0113] 2. Negative electrode: Lithium metal sheet.

[0114] 3. Preparation of the diaphragm: A ceramic layer (the ceramic material is MgAl2O4, and the thickness of the ceramic layer is 3μm) is coated on one side of a polypropylene diaphragm with a thickness of 5μm.

[0115] 4. Assemble the above positive electrode, separator, and negative electrode into the corresponding lithium-ion coin cell and inject electrolyte (electrolyte is 1M LiPF6, EC / DMC / EMC (V / V / V) = 1 / 1 / 1)).

[0116] The main difference between Examples 1-10 and Comparative Examples 1-7 is the different raw material components, ratios, or preparation conditions in the preparation of lithium-rich manganese-based materials. The specific differences are shown in Table 1.

[0117] Table 1

[0118]

[0119]

[0120] Note: "*" indicates that the corresponding parameters in this embodiment or comparative example are the same as those in Embodiment 1-1; " / " indicates that no test was performed.

[0121] In Example 1, the phosphorus (P) content in the first shell was adjusted by changing the amount of the first additive added; the amount added refers to the percentage of the total mass of the precursor. In Example 2, the w (W) content in the second shell was adjusted by changing the amount of the second additive added; the amount added refers to the percentage of the total mass of the precursor. In Examples 3 and 4, the I1 / I2 and I... were changed by adjusting the sintering process during preparation. a / I bThe ratio of [missing information]. In Example 5, the types of additives were changed: the first additive was an equal amount of lithium phosphate replacing sodium dihydrogen phosphate, and the second additive was an equal amount of lithium tungstate replacing tungsten oxide. In Example 6, the porosity of the shell layer was adjusted by modifying the sintering process during preparation. In Examples 7 and 8, the thickness of the first and second shell layers was adjusted by modifying the addition time (coating time) of the first and second additives. In Examples 9 and 10, the BET and primary particle size of the lithium-rich manganese-based material were adjusted by modifying the sintering process during preparation. In Comparative Examples 2-4, the P element content in the first shell layer and the W element content in the second shell layer were adjusted by changing the amount of the first and second additives added. The amount added refers to the percentage of the total mass of the precursor.

[0122] Comparative Example 1: The same as Example 1-1, except that the lithium-rich manganese-based material without coating was used instead of the double-core-shell structure lithium-rich manganese-based material, that is, the lithium-rich manganese-based material was not coated with any shell.

[0123] Comparative Example 5: The same as Example 1-1, except that no second additive was added.

[0124] Comparative Example 6: The same as Example 1-1, except that the first additive was not added.

[0125] Comparative Example 7: The same as Example 1-1 was performed, except that the order of adding the first additive and the second additive was reversed, that is, the second additive was added first, and the first additive was added after an interval of 12 hours.

[0126] Comparative Example 8: The first additive and the second additive were added simultaneously, i.e., the time interval was 0.

[0127] The button cells obtained in the above embodiments and comparative examples were subjected to the following performance tests:

[0128] 1. Test the first-cycle capacity at 2-4.6V.

[0129] After the coin cell is fabricated, it is left to stand for 12 hours to allow the electrolyte to fully impregnate before being tested in an in-cabinet. The Blue Electric testing system is used to execute the charge and discharge program, and the specific steps of the program are as follows:

[0130] (1) Let stand for 10 minutes; charge at 0.1C to 4.6V, and set the recording time to 1 minute;

[0131] (2) Charge at 4.6V until the current is less than 0.025C, and set the recording time to 1min;

[0132] (3) Let stand for 10 minutes; discharge at 0.1C to 2V, and record for 1 minute.

[0133] The initial irreversible capacity is reflected in the charge-discharge efficiency (coulomb efficiency).

[0134] 2. 2.5-4.6V 0.1C / 1C charge / discharge:

[0135] After the coin cell is fabricated, it is left to stand for 12 hours to allow the electrolyte to fully impregnate before being tested in an in-cabinet. The Blue Electric testing system is used to execute the charge and discharge program, and the specific steps of the program are as follows:

[0136] (1) Let stand for 10 minutes; charge at 0.1C to 4.6V, and set the recording time to 1 minute;

[0137] (2) Charge at 4.6V until the current is less than 0.025C, and set the recording time to 1min;

[0138] (3) Let stand for 10 minutes; discharge at 0.1C to 2V, and record for 1 minute;

[0139] (4) Let stand for 10 minutes; charge at 0.1C to 4.6V, and set the recording time to 1 minute;

[0140] (5) Charge at 4.6V until the current is less than 0.025C, and set the recording time to 1min;

[0141] (6) Let stand for 10 minutes; discharge at 0.1C to 2.5V, and set the recording time to 1 minute;

[0142] (7) Let stand for 10 minutes; charge at 0.1C to 4.6V, and set the recording time to 1 minute;

[0143] (8) Charge at 4.6V until the current is less than 0.025C, and set the recording time to 1min;

[0144] (9) Let stand for 10 minutes; discharge at 1C to 2.5V, and set the recording time to 0.1 minutes; end the test.

[0145] 3. Cycling performance at 2–4.6V and 0.5C

[0146] After the coin cell is fabricated, it is left to stand for 12 hours to allow the electrolyte to fully impregnate before being tested in an in-cabinet. The Blue Electric testing system is used to execute the charge and discharge program, and the specific steps of the program are as follows:

[0147] (1) Let stand for 10 minutes; charge at 0.1C to 4.6V, and set the recording time to 1 minute;

[0148] (2) Charge at 4.6V until the current is less than 0.025C, and set the recording time to 1min;

[0149] (3) Let stand for 10 minutes; discharge at 0.1C to 2V, and record for 1 minute;

[0150] (4) Let stand for 10 minutes; charge at 0.5C to 4.6V, and set the recording time to 1 minute;

[0151] (5) Charge at 4.6V until the current is less than 0.025C, and set the recording time to 1min;

[0152] (6) Let stand for 10 minutes; discharge at 0.5C to 2V, and set the recording time to 1 minute;

[0153] Repeat steps 6-10, and end the test after 100 repetitions.

[0154] 4. Water-resistant properties

[0155] Under dew point conditions, after the material is sintered, it is cooled with the furnace until the furnace temperature drops below 150°C. The sagger is then removed, and the material is collected immediately after exiting the furnace and 60 minutes after exiting the furnace for moisture testing (coulometric method). Moisture data are collected.

[0156] The results of the above battery performance tests are recorded in Table 2.

[0157]

[0158]

[0159]

[0160] In summary, this application provides a lithium-rich manganese-based cathode material that can be prepared using existing processes and equipment. This lithium-rich manganese-based material has a double-layer core-shell structure, in which the P element in the first shell layer and the W element in the second shell layer form covalent bonds, which helps to form a denser surface coating layer, improves the structural stability of the lithium-rich manganese-based material, reduces the initial irreversible capacity of the battery, and improves the specific capacity and cycle performance of the battery. In addition, the lithium-rich manganese-based material with this double-layer core-shell structure also has good water resistance.

[0161] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A lithium-rich manganese-based material, characterized in that, It includes a substrate and a shell; the shell covers the outer surface of the substrate; the shell includes a first shell and a second shell, with the first shell located between the substrate and the second shell; The first shell includes the P element, and the second shell includes the W element.

2. The lithium-rich manganese-based material according to claim 1, characterized in that, In the first shell, the content of P element is ≥50%, preferably 60-85%; And / or, in the second shell, the W element content is ≥50%, preferably 60-85%; Preferably, in the shell, the content of P element is greater than the content of W element.

3. The lithium-rich manganese-based material according to claim 1, characterized in that, The chemical formula of the lithium-rich manganese-based material matrix is ​​Li 1+q Ni x Co y Mn z M u O2, wherein M includes one or more of Mg, Al, P, Nb, Y, Ti, Zr, Sn, W, and V, and 0 < q ≤ 1, 0.2 ≤ x ≤ 0.45, 0.02 ≤ y ≤ 0.20, 0.35 ≤ z ≤ 0.78, and 0 < u ≤ 0.2; And / or, the first shell layer comprises an oxide containing the element P; And / or, the second shell layer comprises an oxide containing the element W.

4. The lithium-rich manganese-based material according to claim 1, characterized in that, The lithium-rich manganese-based material has a first diffraction peak at 2θ = 17-19°, with peak intensity denoted as I1, and a second diffraction peak at 2θ = 43-46°, with peak intensity denoted as I2. The ratio of I1 to I2 satisfies: 1.1 ≤ I1 / I2 ≤ 2.

5. The lithium-rich manganese-based material according to claim 1, characterized in that, The peak intensity of the dQ / dV curve of the lithium-rich manganese-based material in the range of 3V-4.2V is denoted as I. a The peak intensity in the range of 4.3V-4.7V is denoted as I. b I a with I b The ratio satisfies: 4≤I a / I b ≤12.

6. The lithium-rich manganese-based material according to claim 1, characterized in that, The porosity of the matrix is ​​less than the porosity of the shell; Preferably, the porosity of the matrix is ​​8-30%, more preferably 15-30%; and / or, the porosity of the shell is 3-10%, more preferably 5-8%; Preferably, the surface of the lithium-rich manganese-based material has a microporous structure, and the pore size of the micropores is 5nm-300nm; Preferably, the thickness of the first shell layer is 0.5μm-4μm; and / or, the thickness of the second shell layer is 10nm-1000nm.

7. The lithium-rich manganese-based material according to any one of claims 1-6, characterized in that, The lithium-rich manganese-based material satisfies one or more of the following conditions: (a) The lithium-rich manganese-based material is a polycrystalline material, and the average particle size of the primary particles of the lithium-rich manganese-based material is 50 nm to 200 nm. (b) The lithium-rich manganese-based material has Dv10 = 2 μm to 8 μm, Dv50 = 5 μm to 20 μm, and Dv90 = 10 μm to 30 μm; (c) The specific surface area of ​​the lithium-rich manganese-based material is 1 m². 2 / g-5m 2 / g; (d) The true density of the lithium-rich manganese-based material is 3.5 g / cm³. 3 -4.5g / cm 3 ; (e) The compaction density of the lithium-rich manganese-based material is 2.7 g / cm³. 3 ~3.5g / cm 3 .

8. A method for preparing the lithium-rich manganese-based material according to any one of claims 1-6, characterized in that, Includes the following steps: The lithium-rich manganese-based material is obtained by coating the outer surface of the substrate with a first shell layer, then coating it with a second shell layer, and sintering. Preferably, the first shell layer includes the element P; Preferably, the second shell layer comprises the element W.

9. A positive electrode plate, characterized in that, Includes the lithium-rich manganese-based material according to any one of claims 1-7, or the lithium-rich manganese-based material prepared by the method of claim 8.

10. A battery, characterized in that, Includes the lithium-rich manganese-based material according to any one of claims 1-7, or includes the positive electrode sheet according to claim 9; Preferably, the compaction density of the positive electrode sheet is 2.7 g / cm³. 3 ~3.5g / cm 3 .

Images