Single-crystal lithium-rich manganese-based positive electrode material and preparation method and application thereof

Abstract

This invention belongs to the field of battery technology and provides a single-crystal lithium-rich manganese-based cathode material, its preparation method, and its application. The single-crystal lithium-rich manganese-based cathode material includes a matrix core with a basic composition of xLi2MnO3·(1-x)LiMO2, and the matrix core is bulk doped with at least one of W, B, or Ru. A coating layer is disposed outside the matrix core, and the coating layer includes at least one of Li2WO4, Li3BO3, or Li3PO4. This invention constructs a synergistic system of "single-crystallization regulation - bulk doping - surface coating," combining bulk structural stability, interfacial reaction suppression, and battery application adaptation. This facilitates the simultaneous resolution of multiple problems such as structural degradation, interfacial deterioration, and parameter incompatibility, achieving comprehensive optimization of the material's overall performance.

Description

Technical Field

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

[0002] Due to limitations in capacity of conventional cathode materials, further improvements in the energy density of solid-state batteries face challenges. Researching high-energy-density cathode materials suitable for solid-state batteries is crucial to overcoming this energy density bottleneck.

[0003] The capacity contribution of lithium-rich manganese-based cathode materials (LRMO) originates from the charge compensation of the redox reactions of transition metal cations and anions, thus easily achieving a larger discharge specific capacity (>250 mAh·g). -1 and higher energy density (1000 W·h·kg) -1 Meanwhile, lithium-rich manganese-based cathode materials have low levels of elements such as cobalt and nickel, while manganese is abundant in the Earth's crust, resulting in lower cost and higher safety. When applied to solid-state batteries, they effectively prevent transition metal cations in the cathode material from dissolving into the electrolyte, thereby improving the structural stability and capacity retention of the cathode material during long-cycle operation. Therefore, using lithium-rich manganese-based cathode materials to construct solid-state batteries not only increases the energy density of solid-state batteries but also offers advantages in environmental friendliness and sustainability.

[0004] However, lithium-rich manganese-based cathode materials also have some problems. Their electronic conductivity is relatively low, and irreversible phase transitions during cycling can induce degradation of the surface and interface structures, leading to poor kinetic behavior. Specifically, at the crystal structure level, transition metal ions (especially Mn) in lithium-rich manganese-based materials... 3+ The low migration barrier of Mn facilitates cross-layer migration during charge-discharge cycles, leading to increased cation mixing between the lithium layer and transition metal layer, thus obstructing lithium-ion migration channels. Simultaneously, fluctuations in the valence state of Mn trigger the Jahn-Teller effect, causing lattice distortion and irreversible transformation of the layered structure towards spinel and rock salt phases. This, coupled with lattice oxygen escape, ultimately results in the collapse of the bulk structure, leading to continuous voltage decay and rapid capacity loss. At the surface interface level, the presence of numerous unsaturated active sites on the material surface, mismatched with the electrolyte chemical potential, easily triggers continuous interfacial side reactions, including electrolyte oxidative decomposition, Mn ion dissolution, and the formation of an unstable CEI film. This CEI film has poor conductivity and is prone to detachment, not only exacerbating the doubling of interfacial impedance but also further deteriorating ion transport efficiency, severely limiting battery cycle life. Furthermore, in terms of scalability and parameter synergy, polycrystalline materials are prone to particle breakage during cycling due to grain boundary stress concentration, while single-crystal materials require complex preparation processes and stringent parameter control, resulting in lower mass production yields and difficulty meeting the demands of large-scale applications.

[0005] In view of this, when the existing lithium-rich manganese-based materials are used in high-energy-density solid-state batteries, the anion redox reaction is difficult to be effectively activated, and the reversibility of the electrochemical reaction is poor. As a result, the lithium-rich manganese-based cathode exhibits a relatively low specific capacity and poor cycle stability in practical applications. At the same time, the regulation of battery parameters of the existing lithium-rich manganese-based cathode materials is mostly optimized in a single dimension, which easily leads to oxygen escape at high voltages, triggering the oxidation and decomposition of the electrolyte, further damaging the stability of the solid-solid interface, and ultimately making it difficult to balance the energy density and cycle stability. Summary of the Invention

[0006] In view of the problems existing in the prior art, the purpose of the present invention is to provide a single-crystal lithium-rich manganese-based cathode material, its preparation method and application. The single-crystal lithium-rich manganese-based cathode material includes a matrix core with a basic composition of xLi2MnO3·(1-x)LiMO2, and the matrix core is doped in the bulk phase. The doping elements include at least one of W, B or Ru; a coating layer is provided outside the matrix core, and the coating layer includes at least one of Li2WO4, Li3BO3 or Li3PO4. By constructing a synergistic system of "single-crystallization regulation - bulk-phase doping - surface coating", combining the stability of the bulk-phase structure, the suppression of interfacial reactions and the adaptation of battery applications is beneficial to synchronously solve multiple problems such as structural degradation, interfacial deterioration and parameter incoordination, and achieve an all-round optimization of the comprehensive performance of the material.

[0007] To achieve this purpose, the present invention adopts the following technical solutions: In the first aspect, the present invention provides a single-crystal lithium-rich manganese-based cathode material, the single-crystal lithium-rich manganese-based cathode material includes a matrix core doped in the bulk phase, and a coating layer covering the matrix core doped in the bulk phase; the chemical formula of the matrix core includes xLi2MnO3·(1-x)LiMO2, where 0 < x < 1, M includes Mn, and also includes Co and / or Ni; the doping elements of the bulk-phase doping include at least one of W, B or Ru; the coating layer includes at least one of Li2WO4, Li3BO3 or Li3PO4.

[0008] In the single-crystal lithium-rich manganese-based cathode material provided by this invention, bulk doping is performed on the matrix core. Bulk doping can optimize the crystal structure through the charge compensation and bonding strengthening effect of heterogeneous ions, enhance the rigidity of MO bonds, suppress the migration of transition metal ions, and synergistically stabilize the layered crystal structure, reducing phase transitions and oxygen escape during cycling, thus significantly improving the stability of the bulk structure. At the same time, the matrix core is coated, and the resulting specific surface coating layer has good chemical stability and ion conductivity. It can serve as a uniform and dense physical protective barrier on the material surface, which is beneficial for blocking electrolyte erosion and metal ion dissolution, while reducing interfacial charge transfer resistance, effectively improving the material's interfacial compatibility and rate performance. Furthermore, the monocrystalline control of the single-crystal material helps to eliminate polycrystalline grain boundary defects and stress concentration, shorten the lithium-ion diffusion path, and further facilitates the precise matching of cathode surface density, electrolyte injection volume, and voltage window, which can further balance the material's structural strength and battery energy density, and resolve the inherent contradiction between high energy and long cycle life. More importantly, the bulk doping elements W, B, and Ru can form a gradient interface with the coating materials Li₂WO₄, Li₃BO₃, or Li₃PO₄ due to their chemical homology, further strengthening the bond. Simultaneously, the lithium-based coating layer can conduct lithium ions without sacrificing rate performance. In contrast, inert coatings such as alumina only provide physical adhesion and hinder lithium-ion transport, failing to achieve the chemical synergistic effect with specific bulk doping. Therefore, by constructing a comprehensive synergistic system of "bulk doping-surface coating-single crystallization control," we can combine bulk structural stability, interface reaction suppression, and battery application adaptation, simultaneously addressing multiple issues such as structural degradation, interface deterioration, and parameter incompatibility. This breaks through the performance bottlenecks of existing single modification technologies, achieving comprehensive optimization of the material's overall performance.

[0009] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following technical solutions.

[0010] As a preferred technical solution of the present invention, the particle size range of the single-crystal lithium-rich manganese-based cathode material is 0.5μm~2μm, for example 0.5μm, 0.8μm, 1μm, 1.3μm, 1.5μm, 1.8μm or 2μm.

[0011] Preferably, the doping amount of the dopant element is 0.5at% to 3at%, for example, 0.5at%, 0.8at%, 1at%, 1.3at%, 1.5at%, 1.8at%, 2at%, 2.3at%, 2.5at%, 2.8at%, or 3at%. In this invention, at% refers to the atomic molar percentage, that is, the percentage of the molar amount of the dopant element relative to the molar amount of the matrix core with the chemical formula xLi2MnO3·(1-x)LiMO2. This doping amount is also equivalent to the percentage of the molar amount of the dopant element in the dopant relative to the molar amount of the lithium-rich manganese-based precursor during material preparation.

[0012] Preferably, the thickness of the coating layer is 5nm to 20nm, such as 5nm, 8nm, 10nm, 13nm, 15nm, 18nm, or 20nm. In this invention, the thickness of the coating layer can be adjusted by controlling the amount of coating agent relative to the matrix core precursor during material preparation. The coating amount can be expressed as a mass percentage, for example, 1wt% to 5wt%.

[0013] In a second aspect, the present invention provides a method for preparing the single-crystal lithium-rich manganese-based cathode material described in the first aspect, comprising: Nickel, cobalt, and manganese sources are mixed with precipitants and complexing agents to carry out precipitation reactions, thereby obtaining lithium-rich manganese-based precursors. The lithium-rich manganese-based precursor, lithium source and dopant are mixed and ball-milled to dope the lithium-rich manganese-based precursor. Then a coating agent is added and mixed and ball-milled to form a coating layer, thus obtaining a doped and coated precursor. The doped precursor was mixed with a lithium source and subjected to molten salt-assisted sintering to obtain a single-crystal lithium-rich manganese-based cathode material.

[0014] The method for preparing single-crystal lithium-rich manganese-based cathode material provided by this invention achieves bulk doping and coating through the sequential effect of stepwise ball milling. The dopant added first achieves bulk doping using mechanical force, while the coating agent added later only serves as a surface coating after doping has been completed. This preparation method simplifies the single-crystal preparation process, and has high mass production yield, short cycle time, and low cost. The resulting single-crystal lithium-rich manganese-based cathode material is compatible with multiple electrolyte systems.

[0015] As a preferred embodiment of the present invention, the nickel source, cobalt source, and manganese source comprise sulfates of the corresponding metal elements; the precipitant comprises sodium hydroxide; and the complexing agent comprises ammonia.

[0016] Preferably, the pH of the precipitation reaction is 10~12, such as 10, 10.3, 10.5, 10.8, 11, 11.2, 11.5, 11.8 or 12, preferably 10.5~11; the temperature is 45℃~65℃, such as 45℃, 50℃, 55℃, 60℃ or 65℃, preferably 50℃~60℃; the stirring speed is 200rpm~600rpm, such as 200rpm, 300rpm, 400rpm, 500rpm or 600rpm, preferably 300rpm~400rpm.

[0017] As a preferred embodiment of the present invention, the dopant includes an oxide of the corresponding dopant element.

[0018] Preferably, the coating agent includes Li2WO4, Li3BO3, or Li3PO4.

[0019] Preferably, the lithium source includes lithium carbonate.

[0020] As a preferred embodiment of the present invention, the molten salt-assisted sintering is carried out in an oxygen-containing atmosphere at a temperature of 800℃~1000℃, such as 800℃, 850℃, 880℃, 900℃, 930℃, 950℃, 980℃ or 1000℃, preferably 850℃~950℃; the holding time is 2h~8h, such as 2h, 3h, 4h, 5h, 6h, 7h or 8h, preferably 4h~6h.

[0021] Preferably, the oxygen-containing atmosphere includes air.

[0022] Preferably, the preparation method further includes, after molten salt-assisted sintering, sequentially sieving, washing with water and drying to obtain a single-crystal lithium-rich manganese-based cathode material.

[0023] As a preferred technical solution of the present invention, the preparation method includes the following steps: S1. Precursor preparation: Using nickel, cobalt, and manganese sources as raw materials, sodium hydroxide as a precipitant, and ammonia as a complexing agent, the precipitation reaction was carried out by controlling pH=10.5~11, temperature 50℃~60℃, and stirring speed 300rpm~400rpm to obtain lithium-rich manganese-based hydroxide precursor. S2. Doping and Coating: In a planetary ball mill, a lithium-rich manganese-based hydroxide precursor is mixed with a lithium source. First, 0.5 at% to 3 at% of a dopant is introduced, which is at least one of oxides of W, B, or Ru, and the mixture is ball-milled. Then, a coating agent is introduced, which is at least one of Li2WO4, Li3BO3, or Li3PO4, and the mixture is ball-milled. The coating layer thickness is controlled at 5 nm to 20 nm to obtain a doped and coated precursor. S3. Sintering treatment: The obtained doped and coated precursor is sintered with molten salt in an air atmosphere, with the temperature controlled at 850℃~950℃ and held for 4h~6h to obtain submicron-sized (particle size range 0.5μm~2μm) single crystal lithium-rich manganese-based cathode material. After cooling, it is crushed and sieved, washed with water to remove impurities and dried under vacuum.

[0024] Thirdly, the present invention provides a positive electrode sheet containing the single-crystal lithium-rich manganese-based positive electrode material described in the first aspect.

[0025] As a preferred embodiment of the present invention, the areal density of the positive electrode sheet is 500 g / m². 2 ~700g / m 2 For example, 500g / m 2 530g / m 2 550g / m 2 580g / m 2 600g / m 2 630g / m 2 650g / m 2 680g / m 2 Or 700g / m 2 This is beneficial for balancing capacity utilization and ion transport.

[0026] Fourthly, the present invention provides a battery comprising the single-crystal lithium-rich manganese-based cathode material described in the first aspect, or the cathode sheet described in the third aspect.

[0027] As a preferred technical solution of the present invention, the battery includes a liquid battery or a solid battery; Preferably, when the battery is a liquid battery, the liquid injection volume is 0.6 mg / A·h to 1.4 mg / A·h, for example, 0.6 mg / A·h, 0.7 mg / A·h, 0.8 mg / A·h, 0.9 mg / A·h, 1 mg / A·h, 1.1 mg / A·h, 1.2 mg / A·h, 1.3 mg / A·h, or 1.4 mg / A·h.

[0028] Preferably, when the battery is a solid-state battery, the mass of the solid electrolyte accounts for 15% to 35% of the mass of the positive electrode material, such as 15%, 18%, 20%, 23%, 25%, 28%, 30%, 32%, or 35%.

[0029] Preferably, the operating voltage window of the battery is 2.0V to 4.6V, for example, it can be 2.0V, 2.3V, 2.5V, 2.8V, 3V, 3.3V, 3.5V, 3.8V, 4V, 4.2V, or 4.6V. This helps to suppress oxygen release at high voltage and lithium dendrite growth at low voltage.

[0030] It should be noted that, due to space limitations and to avoid redundancy, this invention does not exhaustively list all point values ​​within the above numerical range, but it is not limited to the listed values ​​either; other unlisted values ​​within the above numerical range are also applicable.

[0031] Compared with existing technical solutions, the present invention has at least the following beneficial effects: The monocrystalline lithium-rich manganese-based material provided by this invention achieves comprehensive improvement in material and application performance through three-dimensional synergistic modification of bulk doping, surface coating, and monocrystalline control, combined with precise matching of battery parameters: bulk doping enhances structural stability, significantly suppresses phase transition and oxygen escape, and results in minimal voltage decay over long cycles; surface coating blocks electrolyte erosion, significantly reduces interfacial impedance, and provides excellent high-rate performance; monocrystalline design and parameter optimization resolve the inherent contradiction between high energy density and long cycling, resulting in cycling stability far exceeding existing technologies.

[0032] Regarding the single-crystal lithium-rich manganese-based material provided by this invention, this invention has precisely matched the areal density, liquid injection volume, and voltage window of the positive electrode sheet and the battery. As a result, it can ultimately achieve a quadruple breakthrough in structure, interface, energy density, and economy, providing core support for the commercial application of lithium-rich manganese-based materials. Detailed Implementation

[0033] The technical solution of the present invention will be further illustrated below through specific embodiments.

[0034] Those skilled in the art will understand that the embodiments described are merely illustrative of the invention and should not be construed as limiting the invention.

[0035] Example 1 This embodiment provides a single-crystal lithium-rich manganese-based cathode material, comprising a bulk-doped matrix core and a coating layer covering the bulk-doped matrix core; the bulk doping element is W, and the doping amount is 1 at%; the coating layer is Li₂WO₄. 4， The coating thickness is 12 nm; the particle size range of this single-crystal lithium-rich manganese-based cathode material is 0.5 μm to 2 μm; This embodiment also provides a method for preparing the single-crystal lithium-rich manganese-based cathode material: S1. Precursor Preparation: Using nickel sulfate, cobalt sulfate, and manganese sulfate as raw materials, sodium hydroxide as a precipitant, and ammonia as a complexing agent, a precipitation reaction was carried out under controlled conditions of pH=10.5, temperature 55℃, and stirring speed 400rpm to obtain Ni. 0.13 Co 0.13 Mn 0.74 (OH)2 precursor; S2. Doping and Coating: In a planetary ball mill, Ni is... 0.13 Co0.13 Mn 0.74 (OH)₂ precursor is mixed with lithium source Li₂CO₃, relative to Ni 0.13 Co 0.13 Mn 0.74 (OH)2 is first introduced with 1 at% dopant WO3 and mixed and ball-milled; then 3 wt% coating agent Li2WO4 is introduced and mixed and ball-milled, with the ball-to-material ratio controlled at 10:1, and ball-milled for 4 hours to obtain the doped and coated precursor. S3. Sintering treatment: The obtained doped and coated precursor is sintered with molten salt in air atmosphere at a sintering temperature of 900℃ for 5 hours. After cooling, it is crushed through a 200-mesh sieve, washed with water to remove impurities, and vacuum dried to obtain a single-crystal lithium-rich manganese-based cathode material.

[0036] This embodiment also provides a battery containing the monocrystalline lithium-rich manganese-based cathode material. This battery is a solid-state battery. Specifically, the monocrystalline lithium-rich manganese-based cathode material is prepared by mixing the conductive agent and binder in a mass ratio of 96:2:2 to form the cathode. This cathode is then assembled with a lithium metal anode, an electrolyte, and a separator to form a solid-state battery. Vacuum degassing is performed before encapsulation to ensure tight interface contact. The areal density of the cathode is controlled to be 600 g / m³. 2 The battery uses a sulfide electrolyte, Li6PS5Cl, at a concentration of 25 wt%; the battery voltage window is 2.0V~4.6V.

[0037] Example 2 This embodiment provides a single-crystal lithium-rich manganese-based cathode material, including a bulk-doped matrix core and a coating layer covering the bulk-doped matrix core; the bulk-doped element is B with a doping amount of 2 at%; the coating layer is Li3BO3 with a thickness of 8 nm; the particle size range of this single-crystal lithium-rich manganese-based cathode material is 0.5 μm to 2 μm. This embodiment also provides a method for preparing the single-crystal lithium-rich manganese-based cathode material: S1. Precursor Preparation: Using nickel sulfate, cobalt sulfate, and manganese sulfate as raw materials, sodium hydroxide as a precipitant, and ammonia as a complexing agent, a precipitation reaction was carried out under controlled conditions of pH=10.5, temperature 55℃, and stirring speed 400rpm to obtain Ni. 0.13 Co 0.13 Mn 0.74 (OH)2 precursor; S2. Doping and Coating: In a planetary ball mill, Ni is... 0.13 Co 0.13 Mn 0.74 (OH)₂ precursor is mixed with lithium source Li₂CO₃, relative to Ni 0.13 Co 0.13 Mn 0.74(OH)2 is first introduced with 2 at% dopant B2O3 and mixed and ball-milled; then 2 wt% coating agent Li3BO3 is introduced and mixed and ball-milled, with the ball-to-material ratio controlled at 10:1, and ball-milled for 3 hours to obtain the doped and coated precursor. S3. Sintering treatment: The obtained doped and coated precursor is sintered with molten salt in air atmosphere at a sintering temperature of 880℃ for 5.5h. After cooling, it is crushed through a 200-mesh sieve, washed with water to remove impurities, and vacuum dried to obtain a single-crystal lithium-rich manganese-based cathode material.

[0038] This embodiment also provides a battery containing the monocrystalline lithium-rich manganese-based cathode material. This battery is a solid-state battery. Specifically, the monocrystalline lithium-rich manganese-based cathode material is prepared by mixing the conductive agent and binder in a mass ratio of 96:2:2 to form the cathode. This cathode is then assembled with a lithium metal anode, an electrolyte, and a separator to form a solid-state battery. Vacuum degassing is performed before encapsulation to ensure tight interface contact. The areal density of the cathode is controlled to be 580 g / m³. 2 The battery uses a halide electrolyte, Li3InCl6, at a concentration of 22 wt%; the battery voltage window is 2.0V~4.6V.

[0039] Example 3 This embodiment provides a single-crystal lithium-rich manganese-based cathode material, comprising a bulk-doped matrix core and a coating layer covering the bulk-doped matrix core; the bulk-doped element is Ru with a doping amount of 0.8 at%; the coating layer is Li3PO4 with a thickness of 18 nm; the particle size range of this single-crystal lithium-rich manganese-based cathode material is 0.5 μm to 2 μm; This embodiment also provides a method for preparing the single-crystal lithium-rich manganese-based cathode material: S1. Precursor Preparation: Using nickel sulfate, cobalt sulfate, and manganese sulfate as raw materials, sodium hydroxide as a precipitant, and ammonia as a complexing agent, a precipitation reaction was carried out under controlled conditions of pH=10.5, temperature 55℃, and stirring speed 400rpm to obtain Ni. 0.13 Co 0.13 Mn 0.74 (OH)2 precursor; S2. Doping and Coating: In a planetary ball mill, Ni is... 0.13 Co 0.13 Mn 0.74 (OH)₂ precursor is mixed with lithium source Li₂CO₃, relative to Ni 0.13 Co 0.13 Mn 0.74 (OH)2 is first introduced with 0.8 at% dopant RuO2 and mixed and ball-milled; then 4 wt% coating agent Li3PO4 is introduced and mixed and ball-milled, with the ball-to-material ratio controlled at 10:1, and ball-milled for 5 hours to obtain the doped and coated precursor; S3. Sintering treatment: The obtained doped and coated precursor was sintered with molten salt in an air atmosphere at a temperature of 920℃ for 4.5h. After cooling, it was crushed through a 200-mesh sieve, washed with water to remove impurities, and vacuum dried to obtain a single-crystal lithium-rich manganese-based cathode material.

[0040] This embodiment also provides a battery containing the monocrystalline lithium-rich manganese-based cathode material, which is a liquid battery: the monocrystalline lithium-rich manganese-based cathode material is prepared by mixing the conductive agent and binder in a mass ratio of 96:2:2 to form the cathode, which is then assembled with a silicon-based anode, an electrolyte (1 mol / L LiPF6, EC, DMC and EMC in a volume ratio of 1:1:1) and a separator to form a liquid battery. Vacuum degassing is performed before encapsulation to ensure tight contact at the interface; wherein, the areal density of the cathode is controlled to be 620 g / m³. 2 The electrolyte injection volume is 1.0 mg / A·h; the battery voltage window is 2.0V~4.6V.

[0041] Example 4 The difference between this embodiment and Embodiment 1 is that the doping amount of the doping element is adjusted from 1 at% to 0.5 at%. Apart from the above, the other conditions are exactly the same as in Embodiment 1.

[0042] Example 5 The difference between this embodiment and Embodiment 1 is that the doping amount of the dopant element is adjusted from 1 at% to 3 at%. Apart from the above, the other conditions are exactly the same as in Embodiment 1.

[0043] Example 6 The difference between this embodiment and Embodiment 1 is that the amount of coating agent was adjusted to change the thickness of the coating layer, so that the coating layer was adjusted from 12nm to 0.5nm. Apart from the above, the other conditions are exactly the same as those in Embodiment 1.

[0044] Example 7 The difference between this embodiment and Embodiment 1 is that the amount of coating agent was adjusted to change the thickness of the coating layer, so that the coating layer was adjusted from 12nm to 20nm. Apart from the above, the other conditions are exactly the same as those in Embodiment 1.

[0045] Example 8 The difference between this embodiment and Embodiment 1 is that in step S2, the coating agent Li2WO4 is replaced with WO3, which is the same as the dopant. Apart from the above, the other conditions are exactly the same as in Embodiment 1.

[0046] Example 9 The difference between this embodiment and Embodiment 1 is that in step S2, the dopant WO3 is replaced with the same coating agent Li2WO4. Apart from the above, the other conditions are exactly the same as in Embodiment 1.

[0047] Comparative Example 1 This comparative example provides a lithium-rich manganese-based cathode material, including a matrix core that is not doped; and a coating layer of Li2WO4 covering the matrix core. That is, in step S2 of the preparation method, only the coating agent is used and no dopant is used. Except for the above, the other conditions are exactly the same as those in Example 1.

[0048] Comparative Example 2 This comparative example provides a lithium-rich manganese-based cathode material, including a bulk-doped matrix, wherein the bulk-doped dopant element is W, and no coating layer is provided. That is, in step S2 of the preparation method, only the dopant is used and no coating agent is used. Except for the above, the other conditions are exactly the same as those in Example 1.

[0049] Comparative Example 3 This comparative example provides a lithium-rich manganese-based cathode material, comprising a bulk-doped matrix core and a coating layer covering the bulk-doped matrix core; the bulk-doped dopant is W with a doping amount of 1 at%; the coating layer is Al2O3, that is, in step S2 of the preparation method, the coating agent is replaced with Al2O3, and all other conditions are exactly the same as in Example 1.

[0050] Comparative Example 4 This comparative example provides a lithium-rich manganese-based cathode material, comprising a bulk-doped matrix core and a coating layer covering the bulk-doped matrix core; the bulk-doped dopant is Al with a doping amount of 1 at%; the coating layer is Li2WO4, that is, in step S2 of the preparation method, the dopant is replaced with Al2O3, and all other conditions are exactly the same as in Example 1.

[0051] The batteries obtained in the embodiments and comparative examples were tested as follows: 1) First-cycle discharge specific capacity and first coulombic efficiency test, the test conditions are 0.1C rate, and the voltage test window is 2.0V~4.6V; 2) Cyclic performance test: The test conditions are 100 charge-discharge cycles at a 0.5C rate. The capacity retention rate and voltage decay rate are tested and calculated. 3) Rate test: After discharging at 1C and 5C rates respectively, calculate the ratio of capacity retention rate; 4) Interface impedance test: The interface impedance is tested and calculated using EIS testing instruments and methods; The specific test results are shown in the table below.

[0052] Table 1 As can be seen from Table 1: Compared with Comparative Examples 1 and 2, in Comparative Example 1, single bulk doping (such as Ru, B, and W doping) can only suppress the bulk phase transition to a certain extent, but cannot isolate the direct contact between the material and the electrolyte, making it difficult to solve the problems of interfacial side reactions and Mn ion dissolution. In Comparative Example 2, simple surface coating (such as Li3PO4 and Al2O3 coating) can construct a physical isolation layer and alleviate interfacial degradation, but its effect on improving bulk cation mixing and lattice distortion is limited. Furthermore, independent process optimization or parameter adjustment cannot simultaneously resolve the multiple contradictions of structural stability, interfacial compatibility, and large-scale production. In contrast, the single-crystal lithium-rich manganese-based cathode materials provided in Examples 1, 2, and 3 of this invention are beneficial for suppressing phase transitions and oxygen escape in lithium-rich manganese-based materials, reducing voltage decay rates, optimizing material-electrolyte interface compatibility, reducing side reactions and lowering interface impedance. They can achieve synergistic matching between material modification and battery parameters, balancing energy density and cycle life. At the same time, the single-crystal preparation process is simplified, which can improve batch consistency, adapt to large-scale production, and obtain a universal material that is compatible with both solid-state and liquid electrolytes, which is beneficial for expanding the application scenarios of high-energy-density batteries.

[0053] Comparing Example 1 with Comparative Examples 3 and 4, it can be seen that Comparative Examples 3 and 4 cannot achieve the effect of Example 1. This is because the specific bulk doping elements in Example 1 form a chemical synergy with the substances in the coating layer, which can form a gradient interface and increase the strength of the bond.

[0054] Compared with Examples 4-7, Example 1 shows that the amount of bulk doping and the amount of coating have an impact on the performance of the obtained lithium-rich manganese-based material. In this invention, the amount of doping element is controlled at 0.5at%~3at%, and the thickness of coating layer is controlled at 5nm~20nm.

[0055] Compared with Examples 1, 8, and 9, using a single substance for simultaneous doping and coating cannot achieve the optimal effect of the specific combination of dopant and coating agent as in Example 1.

[0056] In summary, this invention develops a multi-dimensional lithium-rich manganese-based modification strategy that enables bulk structure regulation, interface performance optimization, and process parameter synergy. This strategy can be a key approach to address the defects of lithium-rich manganese-based cathode materials and improve their comprehensive electrochemical performance and scalability.

[0057] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details of the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0058] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0059] Furthermore, various different embodiments of the present invention can be combined arbitrarily, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. A single-crystalline lithium-rich manganese-based cathode material, characterized in that, The single-crystalline lithium-rich manganese-based cathode material includes a matrix core with bulk doping, and a coating layer covering the matrix core with bulk doping; the chemical formula of the matrix core includes xLi2MnO3·(1-x)LiMO2, where 0 < x < 1, M includes Mn, and also includes Co and / or Ni; the doping element for the bulk doping includes at least one of W, B, or Ru; the coating layer includes at least one of Li2WO4, Li3BO3, or Li3PO4. 2.The single-crystalline lithium-rich manganese-based cathode material of claim 1, wherein, The particle size range of the single-crystalline lithium-rich manganese-based cathode material is 0.5 μm to 2 μm; Preferably, the doping amount of the doping element is 0.5 at% to 3 at%; Preferably, the thickness of the coating layer is 5 nm to 20 nm.

3. A method for preparing a single-crystal lithium-rich manganese-based cathode material as described in claim 1 or 2, characterized in that, It includes: Mixing a nickel source, a cobalt source, and a manganese source with a precipitating agent and a complexing agent, and performing a precipitation reaction to obtain a lithium-rich manganese-based precursor; Mixing and ball-milling the lithium-rich manganese-based precursor, a lithium source, and a dopant to dope the lithium-rich manganese-based precursor, and then adding a coating agent for mixing and ball-milling to form a coating layer, thereby obtaining a doped and coated precursor; Performing molten salt-assisted sintering on the doped and coated precursor to obtain a single-crystalline lithium-rich manganese-based cathode material.

4. The method for preparing single-crystal lithium-rich manganese-based cathode material according to claim 3, characterized in that, The nickel source, cobalt source, and manganese source include sulfates of corresponding metal elements; the precipitating agent includes sodium hydroxide; the complexing agent includes ammonia water; Preferably, the pH of the precipitation reaction is 10 to 12, the temperature is 45°C to 65°C, and the stirring speed is 200 rpm to 600 rpm.

5. The method for preparing single-crystal lithium-rich manganese-based cathode material according to claim 3 or 4, characterized in that, The dopant includes oxides of corresponding doping elements; Preferably, the coating agent includes Li2WO4, Li3BO3, or Li3PO4; Preferably, the lithium source includes lithium carbonate.

6. The method for preparing the single-crystal lithium-rich manganese-based cathode material according to any one of claims 3-5, characterized in that, The molten salt-assisted sintering is carried out in an oxygen-containing atmosphere, the temperature is 800°C to 1000°C, and the heat preservation time is 2 h to 8 h; Preferably, the oxygen-containing atmosphere includes air; Preferably, the preparation method further includes, after the molten salt-assisted sintering is completed, performing sieving, washing with water, and drying in sequence to obtain a single-crystalline lithium-rich manganese-based cathode material.

7. A positive electrode sheet, characterized in that, The positive electrode sheet contains the single-crystalline lithium-rich manganese-based cathode material according to claim 1 or 2.

8. The positive electrode sheet according to claim 7, characterized in that, The areal density of the positive electrode sheet is 500 g / m 2 700 g / m 2 .

9. A battery, characterized in that, The battery contains the single-crystalline lithium-rich manganese-based cathode material according to claim 1 or 2, or contains the positive electrode sheet according to claim 7 or 8.

10. The battery according to claim 9, characterized in that, The battery includes a liquid battery or a solid-state battery; Preferably, when the battery is a liquid battery, the injection amount is 0.6 mg / A·h to 1.4 mg / A·h; Preferably, when the battery is a solid-state battery, the mass of the solid electrolyte accounts for 15% to 35% of the mass of the cathode material; Preferably, the working voltage window of the battery is 2.0 V to 4.6 V.

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