Doped and coated high-nickel ternary positive electrode material as well as preparation method and application thereof

Abstract

The invention provides a doped and coated high-nickel ternary positive electrode material as well as a preparation method and application thereof. The doped and coated high-nickel ternary positive electrode material comprises a high-nickel ternary positive electrode material and a lithium metal acid salt coating layer positioned on the surface of the high-nickel ternary positive electrode material, the high-nickel ternary positive electrode material is doped with a first metal element including Ta; and the lithium metal acid salt coating layer comprises a second metal element which comprises Nb. According to the invention, through the synergistic effect of metal bulk phase molecular-level doping and a lithium metal acid salt coating layer, bulk phase structure collapse and interface side reaction are synchronously inhibited; the first metal element is doped into the high-nickel ternary positive electrode material to occupy a transition metal site to form a first metal element-O bond, so that lattice oxygen release is inhibited, mixed arrangement is reduced, phase change of the material in a deep charging and discharging process is blocked, and the cycle performance of the material is improved; the lithium metal acid salt coating layer has the ion / electron double-conduction characteristic, the rate capability is improved while the interface stability is guaranteed, and blocking of traditional inert coating on ion migration is eliminated.

Description

Technical Field

[0001] This invention relates to the field of high-nickel ternary cathode material preparation technology, and particularly to a doped and coated high-nickel ternary cathode material, its preparation method, and its application. Background Technology

[0002] With the increasing global demand for sustainable development and clean energy, the widespread application of traditional lithium-ion batteries in electric vehicles, renewable energy storage, and portable electronic devices faces severe challenges. Although lithium-ion batteries boast high energy density (>250Wh / kg) and good cycle life (>1000 cycles), the flammability of their liquid electrolytes (flash point <40℃), leakage risk, and thermal runaway tendency lead to increasingly prominent safety issues. Furthermore, interfacial side reactions intensify at high temperatures (>60℃), and ionic conductivity drops by over 80% at low temperatures (<-20℃), severely limiting applications in extreme environments. To overcome these bottlenecks, solid-state batteries utilize non-flammable inorganic solid electrolytes (such as sulfide Li6PS5Cl), fundamentally eliminating safety hazards and increasing theoretical energy density to over 400Wh / kg, making them an ideal choice for next-generation energy storage technology.

[0003] Against this backdrop, nickel-rich ternary cathode materials (LiNi) x Co y Mn z O2 (x≥0.8) has become a core material for solid-state batteries due to its high specific capacity (>200mAh / g) and cost advantages. However, its industrialization faces the following obstacles: during deep charge and discharge processes, Li2O3... ＋ / Ni 2＋ Ion mixing (mixing degree > 8%) induces lattice distortion, causing anisotropic shrinkage of the layered structure during the H2→H3 phase transition, leading to microcracks in particles and irreversible capacity decay; poor interface stability, residual alkaline compounds on the material surface react with the solid electrolyte to form a high-resistivity interface layer; extreme performance degradation, high-temperature cycling accelerates the dissolution of transition metals, low-temperature lithium-ion diffusion rate decreases, and cycling stability is insufficient.

[0004] To address the aforementioned issues, current optimization methods primarily employ two approaches: bulk doping and surface coating modification. Bulk doping involves introducing Mg... 2＋ Al 3＋ While elements occupying lattice sites can effectively reduce cation mixing, suppress phase transitions, and improve thermal stability, they are insufficient to block side reactions on the material surface. Surface coating modification, on the other hand, uses oxide coatings (such as Al₂O₃ and ZrO₂) to isolate the cathode from direct contact with the electrolyte, thereby reducing interfacial side reactions. However, existing coating materials generally suffer from low ionic and electronic conductivity (typically, ZrO₂ has an ionic conductivity <10).－10 The coating thickness (S / cm) cannot provide an effective channel for lithium-ion migration, resulting in a significant decrease in rate performance as the coating thickness increases.

[0005] For example, CN113594418A discloses a niobium-coated ternary cathode material. Its preparation process involves dissolving niobium and lithium sources, mixing them with a ternary precursor, and then drying and calcining at high temperature to form a Li3NbO4 coating layer. While this technology reduces interfacial side reactions through surface coating, it suffers from functional defects. The extremely low electronic conductivity of Li3NbO4 leads to significant capacity decay at high rates, and it does not solve the problem of bulk structure collapse. CN114524360A discloses a low-temperature hydrothermal aluminum doping process: Al is doped in a low-temperature hydrothermal environment... 3＋ A precursor is introduced, followed by high-temperature crystallization to obtain the doped material. While this technique reduces cation mixing, it suffers from insufficient doping depth. (Al) 3＋ Distributed only on the shallow surface of particles and lacking coating, the high residual lithium content at the interface limits the improvement in high-voltage cycling performance. Therefore, the core contradictions of the existing technology system are concentrated in three aspects: 1. Functional limitations: Single modification methods (doping or coating only) cannot simultaneously solve the problems of bulk structural instability and interface corrosion; 2. Performance compromises: Although the inert coating layer improves interface stability, it sacrifices ion transport capacity, forcing a decrease in rate performance; 3. Process complexity: The multi-step discrete doping and coating processes result in high production energy consumption and poor batch consistency.

[0006] Therefore, how to provide a synergistic modification method that can simultaneously achieve bulk structural stability and efficient interface protection of high-nickel ternary cathode materials, thereby improving the electrochemical performance of solid-state batteries, is a technical problem that urgently needs to be solved. Summary of the Invention

[0007] To address the aforementioned technical problems, this invention provides a doped and coated high-nickel ternary cathode material, its preparation method, and its applications. This invention utilizes the synergistic effect of bulk metal molecular-level doping and a lithium metalate coating layer to simultaneously suppress bulk structural collapse (H3 phase transition) and interfacial side reactions. The first metal element is incorporated into the high-nickel ternary cathode material, occupying transition metal sites to form a first metal element -O bond, suppressing lattice oxygen release, and reducing Li... ＋ / Ni 2＋ The mixing of materials prevents the H2→H3 phase transition during deep charge and discharge, thus improving the material's cycle performance. The lithium metal salt coating layer has both ionic and electronic conduction properties, which improves rate performance while ensuring interface stability. It also eliminates the blockage of ion migration by traditional inert coatings. In this way, the structural stability, interface problems, and electrochemical performance of high-nickel ternary cathode materials are improved through the synergistic effect of doping and coating.

[0008] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a doped and coated high-nickel ternary cathode material, the doped and coated high-nickel ternary cathode material comprising a high-nickel ternary cathode material and a lithium metal salt coating layer located on the surface of the high-nickel ternary cathode material; The high-nickel ternary cathode material is doped with a first metallic element, which includes Ta. The lithium metal salt coating layer includes a second metal element, which includes Nb.

[0009] This invention incorporates a first metal element into a high-nickel ternary cathode material, which occupies transition metal sites to form -O bonds, thereby suppressing the release of lattice oxygen and reducing Li... ＋ / Ni 2＋ The mixing of these components prevents the H2→H3 phase transition in the material during deep charge and discharge, thus improving the material's cycle performance. Simultaneously, a lithium metal salt coating layer with both ionic and electronic conduction properties is constructed, protecting the interface while ensuring efficient lithium ion migration, thereby enhancing the material's electrochemical performance.

[0010] This includes a first metal element, Ta, doped into the bulk phase, and a second metal element, Nb, used as a metal element (other than lithium metal) in the lithium metal salt coating layer. 5＋ and Nb 5＋ There are fundamental differences in their dynamic behavior. 5＋ Hydrated ions have a larger radius (0.68 Å vs Nb). 5＋ The diffusion barrier is 0.64 Å, and it is even higher under high-temperature hydrothermal conditions, leading to Nb 5＋ Li3NbO4 crystal nuclei are preferentially deposited on the surface, while Ta... 5＋ Gradually diffuses into the bulk phase, and Nb 5＋ Ionic radius (0.69 Å) and Ni 3＋ The mismatch (0.56 Å) is >20%, thus it cannot stably occupy lattice sites. Furthermore, in a hydrothermal environment with pH = 10.5–11.5, Ta... 5＋ Hydrolysis product [TaO(OH)3] － The negatively charged material exhibits electrostatic repulsion with the surface of the similarly negatively charged high-nickel ternary precursor (isoelectric point pH=12.5), forcing Ta... 5＋ Diffusion into the bulk phase, while Nb 5＋ The formed [Nb6O 19 ] 8－ Clusters adsorb onto the surface Mn 3＋ Due to the presence of defect sites, the Ta content in the coating layer is extremely low, thereby enabling the first metal element to be doped into the bulk phase, and the second metal element to serve as the metal element in the lithium metal salt coating layer.

[0011] As a preferred embodiment of the present invention, the lithium metal salt coating layer includes a first lithium metal salt coating layer and a second lithium metal salt coating layer.

[0012] Preferably, the first lithium metal acid salt coating layer is located on the surface of the high-nickel ternary cathode material, and the second lithium metal acid salt coating layer is located on the surface of the first lithium metal acid salt coating layer.

[0013] As a preferred embodiment of the present invention, the first lithium metal salt coating layer is a dense layer.

[0014] Preferably, the density of the first lithium metal salt coating layer is ≥90%, such as 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, or 99%.

[0015] Preferably, the thickness of the first lithium metal salt coating layer is 5nm to 8nm, such as 5nm, 5.5nm, 6nm, 6.5nm, 7nm, 7.5nm or 8nm.

[0016] In this invention, the thickness of the first lithium metallate coating layer is controlled to be 5nm~8nm. This effectively isolates the high-nickel cathode material from direct contact with the solid electrolyte and suppresses interfacial side reactions, while ensuring that it does not significantly hinder lithium-ion migration, thus achieving a balance between interfacial stability and ionic conductivity. If the thickness of the first lithium metallate coating layer is too thin, the coating layer will be discontinuous and defective, failing to provide a complete and effective physical barrier for the highly active high-nickel ternary cathode material. Residual interfacial side reactions will significantly reduce the battery's capacity and capacity retention. If the thickness of the first lithium metallate coating layer is too thick, the migration resistance of lithium ions through the coating layer will be too great. Although interfacial stability is guaranteed, it will severely sacrifice the battery's rate performance and capacity, and exacerbate voltage polarization.

[0017] As a preferred embodiment of the present invention, the second lithium metal salt coating layer is a porous layer.

[0018] The lithium metal salt coating of this invention is a gradient double coating layer. The dense inner layer mainly contributes to the interfacial stability and has high ionic conductivity, providing a channel for lithium migration. The porous outer layer provides a larger specific surface area and more sufficient contact with the conductive agent, resulting in better electronic conductivity. The gradient double coating layer protects the interface while ensuring efficient lithium ion migration, thereby improving the electrochemical performance of the material.

[0019] Preferably, the porosity of the second lithium metal salt coating layer is 15% to 35%, such as 15%, 18%, 20%, 22%, 25%, 28%, 30%, 32%, or 35%.

[0020] Preferably, the thickness of the second lithium metal salt coating layer is 12nm~17nm, such as 12nm, 12.5nm, 13nm, 13.5nm, 14nm, 14.5nm, 15nm, 15.5nm, 16nm, 16.5nm or 17nm.

[0021] In this invention, the thickness of the second lithium metalate coating layer is controlled to be 12nm~17nm. This allows for sufficient electronic conduction pathways while maintaining the porous structure of the coating layer itself, thereby ensuring rapid lithium ion migration and achieving stable and efficient interfacial contact with the solid electrolyte and conductive agent. If the thickness of the second lithium metalate coating layer is too thin, its porous framework structure will be underdeveloped, making it impossible to construct an effective three-dimensional electronic conduction network. This results in limited improvement in the overall electronic conductivity of the material and insignificant improvement in rate performance. Furthermore, an excessively thin outer layer cannot effectively buffer volume changes during charging and discharging. If the thickness of the second lithium metalate coating layer is too thick, although electronic conductivity is improved, the transport path of lithium ions in the coating layer is too long, increasing the overall ion migration resistance and thus impairing the rate performance of the battery.

[0022] In a second aspect, the present invention also provides a method for preparing the doped and coated high-nickel ternary cathode material according to the first aspect, the method comprising the following steps: (1) The high-nickel ternary precursor was dispersed in a mixed solution and subjected to a hydrothermal reaction to obtain an intermediate material; The mixed solution includes a first metal element salt, a second metal element salt, a first lithium source, and a solvent; The intermediate material includes a high-nickel ternary precursor and a lithium metal salt coating layer located on the surface of the high-nickel ternary precursor. The high-nickel ternary precursor is doped with a first metal element, which includes Ta. The lithium metal salt coating layer includes a second metal element, which includes Nb. (2) The second lithium source and the intermediate material described in step (1) are mixed evenly and then calcined to obtain a doped and coated high-nickel ternary cathode material.

[0023] This invention develops a one-step hydrothermal method to simultaneously complete bulk doping of metal elements and coating of lithium metal salts, avoiding particle breakage and residual lithium accumulation caused by multiple high-temperature processes, thereby significantly improving production efficiency and material consistency. Furthermore, the synthesis process is simple, easy to operate, requires minimal equipment, and is low-cost, making it suitable for large-scale production.

[0024] As a preferred technical solution of the present invention, the chemical formula of the high-nickel ternary precursor in step (1) is Ni x Coy Mn 1-x-y (OH)2, where 0.8≤x<1, for example, x can be 0.8, 0.82, 0.85, 0.88, 0.9, 0.92, 0.95, 0.98 or 0.99, etc., and 0<y<0.2, for example, y can be 0.01, 0.05, 0.08, 0.1, 0.12, 0.15, 0.18 or 0.19, etc.

[0025] It should be noted that the preparation method of the high-nickel ternary precursor is not subject to specific requirements or special limitations in this invention. Commonly used preparation methods in the art are applicable to this invention, and those skilled in the art can make adaptive selections and adjustments according to actual conditions.

[0026] For example, the present invention provides a method for preparing a high-nickel ternary precursor, the method comprising the following preparation steps: According to Ni x Co y Mn 1-x-y (OH)₂, where 0.8 ≤ x < 1, 0 < y < 0.2, was used to prepare a nickel-cobalt-manganese ternary metal mixed salt solution. The precipitant solution and complexing agent solution were mixed to obtain a mixed solution. The nickel-cobalt-manganese ternary metal mixed salt solution and the mixed solution were slowly added in parallel to the reaction vessel for co-precipitation. Throughout the process, the pH value of the reaction environment was controlled between 10.5 and 11.5 by adjusting the flow rate of the mixed solution, the rotation speed was maintained at 400 rpm to 550 rpm, and the temperature was maintained at 50℃ to 65℃. After the reaction, the resulting solution was centrifuged sequentially with 2% to 4% NaOH and aqueous solution. The precipitate obtained after washing was dried to obtain Ni. x Co y Mn 1-x-y (OH)2 high-nickel ternary precursor.

[0027] Preferably, in the mixed solution of step (1), the molar ratio of the first metal element salt, the second metal element salt and the first lithium source is (0.5~1.5):(2~4):(4~6), for example 1:3:4, 0.5:2:6, 1.5:4:4, 0.5:3:5, 1:2:4 or 1:4:6, etc.

[0028] This invention regulates the molar ratio of the first metal element salt, the second metal element salt, and the first lithium source to (0.5~1.5):(2~4):(4~6). Within this optimal range, the content of the doping element ensures effective Ta doping into the bulk phase for structural stability while simultaneously ensuring the formation of a complete and gradient-structured Li3NbO4 coating layer. If the proportion of the first metal element salt is too low, insufficient bulk doping weakens the structural stabilization effect; if it is too high, it affects the electrochemical activity of the host material. If the proportion of the second metal element salt is too low, the coating layer is incomplete, resulting in insufficient interface protection; if it is too high, an excessively thick coating layer hinders lithium-ion migration.

[0029] Preferably, the molar concentration of the mixed solution is 0.05 mol / L to 0.2 mol / L, for example, 0.05 mol / L, 0.08 mol / L, 0.1 mol / L, 0.12 mol / L, 0.15 mol / L, 0.18 mol / L, or 0.2 mol / L.

[0030] As a preferred technical solution of the present invention, the hydrothermal reaction in step (1) includes a first hydrothermal reaction and a second hydrothermal reaction.

[0031] Preferably, the total time of the hydrothermal reaction in step (1) is 8h to 12h, for example, 8h, 8.5h, 9h, 9.5h, 10h, 10.5h, 11h, 11.5h or 12h.

[0032] Preferably, the time for the first hydrothermal reaction is 3h to 5h, for example, 3h, 3.2h, 3.5h, 3.8h, 4h, 4.2h, 4.5h, 4.8h or 5h.

[0033] Preferably, after the first hydrothermal reaction is completed, a first lithium metal salt coating layer is obtained.

[0034] Preferably, after the second hydrothermal reaction is completed, a second lithium metal salt coating layer is obtained.

[0035] In this invention, the pH of the reaction liquid in the reaction vessel is different for different hydrothermal reaction times. In the first hydrothermal reaction stage, the high pH environment promotes the rapid hydrolysis of metal cations, forming a dense first lithium metal salt coating layer on the particle surface, providing ion channels. In the second hydrothermal reaction stage, the pH decreases, the deposition rate of metal cations slows down, and a porous second lithium metal salt coating layer is formed, which is rich in electrons and improves conductivity.

[0036] Preferably, the first hydrothermal reaction and the second hydrothermal reaction are at the same temperature.

[0037] Preferably, the temperatures of the first hydrothermal reaction and the second hydrothermal reaction are both 150℃~200℃, such as 150℃, 155℃, 160℃, 165℃, 170℃, 175℃, 180℃, 185℃, 190℃, 195℃ or 200℃.

[0038] In this invention, the density and thickness of the first lithium metal salt coating layer, and the porosity and thickness of the second lithium metal salt coating layer are controlled by adjusting the hydrothermal reaction time (including the time of the first hydrothermal reaction and the time of the second hydrothermal reaction) and the hydrothermal reaction temperature.

[0039] As a preferred technical solution of the present invention, in step (1), the first metal element salt includes tantalum salt.

[0040] Preferably, in step (1), the second metal element salt includes a niobium salt.

[0041] Preferably, in step (1), the first metal element salt and the second metal element salt each independently include a chloride salt.

[0042] Preferably, in step (1), the first lithium source includes lithium hydroxide.

[0043] Preferably, the solvent in step (1) includes deionized water.

[0044] As a preferred technical solution of the present invention, in step (2), the second lithium source includes at least one of lithium hydroxide, lithium nitrate or lithium acetate, preferably lithium hydroxide.

[0045] Preferably, in step (2), the molar ratio of the intermediate material to the second lithium source is 1:(1.03~1.05), for example, 1:1.03, 1:1.04 or 1:1.05.

[0046] Preferably, the calcination in step (2) includes primary calcination and secondary calcination.

[0047] Preferably, the calcination in step (2) is carried out in an oxygen atmosphere.

[0048] Preferably, the heating rate of the first calcination in step (2) is 3℃ / min to 5℃ / min, for example, 3℃ / min, 3.5℃ / min, 4℃ / min, 4.5℃ / min or 5℃ / min.

[0049] Preferably, the holding temperature for the first calcination in step (2) is 300℃~500℃, such as 300℃, 320℃, 350℃, 380℃, 400℃, 420℃, 450℃, 480℃ or 500℃.

[0050] Preferably, the holding time for the first calcination in step (2) is 3h to 5h, for example, 3h, 3.5h, 4h, 4.5h or 5h.

[0051] Preferably, the heating rate of the secondary calcination in step (2) is 2℃ / min to 3℃ / min, for example, 2℃ / min, 2.2℃ / min, 2.5℃ / min, 2.8℃ / min or 3℃ / min.

[0052] Preferably, the holding temperature for the secondary calcination in step (2) is 600℃~800℃, such as 600℃, 620℃, 650℃, 680℃, 700℃, 720℃, 750℃, 780℃ or 800℃.

[0053] Preferably, the heat preservation time for the secondary calcination in step (2) is 8h~12h, for example 8h, 9h, 10h, 11h or 12h.

[0054] As a preferred technical solution of the present invention, the preparation method includes the following steps: (1) The high-nickel ternary precursor, with the general chemical formula Ni x Co y Mn 1-x-y (OH)2, where 0.8≤x<1, 0<y<0.2, is dispersed in a mixed solution with a molar concentration of 0.05mol / L~0.2mol / L. After a first hydrothermal reaction for 3h~5h and a second hydrothermal reaction at 150℃~200℃, an intermediate material is obtained. The total hydrothermal reaction time is 8h~12h. The mixed solution includes a first metal element salt, a second metal element salt, a first lithium source, and a solvent, wherein the molar ratio of the first metal element salt, the second metal element salt, and the first lithium source is (0.5~1.5):(2~4):(4~6). The intermediate material includes a high-nickel ternary precursor and a lithium metal salt coating layer on the surface of the high-nickel ternary precursor. After the first hydrothermal reaction is completed, a first lithium metal salt coating layer is obtained. After the second hydrothermal reaction is completed, a second lithium metal salt coating layer is obtained. The high-nickel ternary precursor is doped with a first metal element, which includes Ta. The lithium metal salt coating layer includes a second metal element, which includes Nb. (2) Mix the second lithium source and the intermediate material described in step (1) evenly, with the molar ratio of the intermediate material to the second lithium source being 1:(1.03~1.05). In an oxygen atmosphere, heat the material to 300℃~500℃ at a heating rate of 3℃ / min~5℃ / min and hold for 3h~5h for a first calcination. Then heat the material to 600℃~800℃ at a heating rate of 2℃ / min~3℃ / min and hold for 8h~12h for a second calcination to obtain a doped and coated high-nickel ternary cathode material.

[0055] Thirdly, the present invention also provides a lithium solid-state battery, the lithium solid-state battery comprising the doped and coated high-nickel ternary cathode material as described in the first aspect, or the doped and coated high-nickel ternary cathode material prepared by the preparation method described in the second aspect.

[0056] Compared with the prior art, the present invention has at least the following beneficial effects: 1) This invention simultaneously suppresses bulk structure collapse (H3 phase transition) and interfacial side reactions through the synergistic effect of bulk molecular-level doping of the metal phase and lithium metalate coating. The first metal element is incorporated into the high-nickel ternary cathode material, occupying transition metal sites to form a first metal element -O bond, suppressing the release of lattice oxygen and reducing Li... ＋ / Ni 2＋ The mixing of materials prevents the H2→H3 phase transition during deep charge and discharge, thus improving the material's cycle performance. The lithium metal salt coating layer has both ionic and electronic conduction properties, which improves rate performance while ensuring interface stability. It also eliminates the blockage of ion migration by traditional inert coatings. In this way, the structural stability, interface problems, and electrochemical performance of high-nickel ternary cathode materials are improved through the synergistic effect of doping and coating.

[0057] 2) This invention develops a one-step hydrothermal method to simultaneously complete bulk doping of metal elements and coating of lithium metal salts, avoiding particle breakage and residual lithium accumulation caused by multi-step high-temperature processing, thereby significantly improving production efficiency and material consistency. Furthermore, the preparation method of the doped and coated high-nickel ternary cathode material provided by this invention has a simple synthesis process, is easy to operate, has low equipment requirements, and is low in cost, making it suitable for large-scale production. Detailed Implementation

[0058] To facilitate understanding of the present invention, the following embodiments are provided. Those skilled in the art should understand that these embodiments are merely illustrative and should not be construed as limiting the scope of the invention.

[0059] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0060] Example 1 This embodiment provides a doped and coated high-nickel ternary cathode material and its preparation method. The doped and coated high-nickel ternary cathode material includes a Ta-doped high-nickel ternary cathode material and a first Li3NbO4 coating layer on the surface (density 95%, thickness 6nm), and a second Li3NbO4 coating layer on the surface of the first Li3NbO4 coating layer (porosity 25%, thickness 15nm).

[0061] The preparation method includes the following steps: (1) According to Ni 0.8 Co 0.1 Mn 0.1 To prepare a mixed metal sulfate solution (using deionized water as solvent) of NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O with a molar concentration of 2 mol / L, 40 wt% NaOH solution and 22 wt% ammonia solution were mixed to obtain a mixed solution. The two solutions were then slowly added concurrently to the reactor for co-precipitation. Throughout the process, the pH of the reaction environment was controlled to fluctuate between 11 and 11.5 by adjusting the flow rate of the mixed solution. The rotation speed was maintained at 500 rpm, and the temperature at 60℃. After 48 hours of reaction, the resulting solution was centrifuged sequentially with 3% NaOH and aqueous solution. The washed precipitate was then dried to obtain NiSO4·6H2O. 0.8 Co 0.1 Mn 0.1 (OH)2 high-nickel ternary precursor; TaCl5, NbCl5, and LiOH were mixed in a molar ratio of 1:3:4 to prepare a mixed solution with a molar concentration of 0.1 mol / L (using deionized water as the solvent). Ni... 0.8 Co 0.1 Mn 0.1 (OH)2 is dispersed in a mixed solution and subjected to a first hydrothermal reaction at 180°C for 3 hours (pH ≥ 10.5 during the first hydrothermal reaction) to form a first lithium metal salt coating layer (Li3NbO4). Then, a second hydrothermal reaction is carried out at 180°C for 7 hours (pH < 10.5 during the second hydrothermal reaction) to form a second lithium metal salt coating layer (Li3NbO4). During the hydrothermal process, Ta is doped into the interior of the high-nickel ternary precursor. The resulting product is filtered, washed, and dried to obtain an intermediate material. (2) Mix LiOH·H2O and intermediate materials evenly at a molar ratio of 1.05:1. In an oxygen atmosphere, heat the mixture to 400℃ at a heating rate of 5℃ / min and hold for 4h for a first calcination. Then heat the mixture to 700℃ at a heating rate of 3℃ / min and hold for 10h for a second calcination to obtain a doped and coated high-nickel ternary cathode material.

[0062] Example 2 This embodiment provides a doped and coated high-nickel ternary cathode material and its preparation method. The difference between the doped and coated high-nickel ternary cathode material and that in Embodiment 1 is that the density of the first Li3NbO4 coating layer is 92% and the thickness is 5nm, and the porosity of the second Li3NbO4 coating layer is 18% and the thickness is 12nm. The remaining structure and parameters are consistent with those in Embodiment 1.

[0063] The preparation method differs from that in Example 1 in that the first hydrothermal reaction takes 2.5 hours and the second hydrothermal reaction takes 5.5 hours, while the remaining preparation methods and parameters are the same as in Example 1.

[0064] Example 3 This embodiment provides a doped and coated high-nickel ternary cathode material and its preparation method. The difference between the doped and coated high-nickel ternary cathode material and that in Embodiment 1 is that the density of the first Li3NbO4 coating layer is 91% and the thickness is 5.5 nm, the porosity of the second Li3NbO4 coating layer is 20% and the thickness is 13.5 nm, and the remaining structure and parameters are consistent with those in Embodiment 1.

[0065] The preparation method described herein differs from that in Example 1 in that the first hydrothermal reaction takes 3.2 hours and the second hydrothermal reaction takes 5.7 hours, while the remaining preparation methods and parameters are consistent with those in Example 1.

[0066] Example 4 This embodiment provides a doped and coated high-nickel ternary cathode material and its preparation method. The difference between the doped and coated high-nickel ternary cathode material and that in Embodiment 1 is that the density of the first Li3NbO4 coating layer is 91% and the thickness is 6nm, and the porosity of the second Li3NbO4 coating layer is 32% and the thickness is 14nm. The remaining structure and parameters are the same as those in Embodiment 1.

[0067] The preparation method described herein differs from that in Example 1 in that the first hydrothermal reaction takes 3.5 hours and the second hydrothermal reaction takes 5.8 hours, while the remaining preparation methods and parameters are consistent with those in Example 1.

[0068] Example 5 This embodiment provides a doped and coated high-nickel ternary cathode material and its preparation method. The difference between the doped and coated high-nickel ternary cathode material and that in Embodiment 1 is that the density of the first Li3NbO4 coating layer is 90% and the thickness is 5nm, and the porosity of the second Li3NbO4 coating layer is 30% and the thickness is 13nm. The remaining structure and parameters are consistent with those in Embodiment 1.

[0069] The difference between the preparation method described herein and Example 1 is that the first hydrothermal reaction time is 2.5 h and the second hydrothermal reaction time is 5.6 h, while the remaining preparation methods and parameters are consistent with those of Example 1.

[0070] Example 6 This embodiment provides a doped and coated high-nickel ternary cathode material and its preparation method. The difference between the preparation method and that in Embodiment 1 is that the holding temperature of the first calcination in step (2) is 500°C, while the other preparation methods and parameters are consistent with those in Embodiment 1.

[0071] Example 7 This embodiment provides a doped and coated high-nickel ternary cathode material and its preparation method. The doped and coated high-nickel ternary cathode material includes a Ta-doped high-nickel ternary cathode material and a first Li3NbO4 coating layer on the surface (density 95%, thickness 6nm), and a second Li3NbO4 coating layer on the surface of the first Li3NbO4 coating layer (porosity 25%, thickness 15nm). The remaining preparation methods and parameters are consistent with those in Example 1.

[0072] The difference between the preparation method described above and Example 1 is that a mixed metal sulfate solution of NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O (solvent: deionized water) is prepared to obtain Ni. 0.9 Co 0.05 Mn 0.05 The (OH)2 high-nickel ternary precursor was prepared using the same methods and parameters as in Example 1.

[0073] Example 8 This embodiment provides a doped and coated high-nickel ternary cathode material and its preparation method. The doped and coated high-nickel ternary cathode material includes a Ta-doped high-nickel ternary cathode material and a first Li3NbO4 coating layer on the surface (density 90%, thickness 5nm), and a second Li3NbO4 coating layer on the surface of the first Li3NbO4 coating layer (porosity 18%, thickness 12nm).

[0074] The preparation method includes the following steps: (1) According to Ni 0.8 Co 0.1 Mn 0.1To prepare a mixed metal sulfate solution (using deionized water as solvent) of NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O with a molar concentration of 1.8 mol / L, 40 wt% NaOH solution and 22 wt% ammonia solution were mixed to obtain a mixed solution. The two solutions were then slowly added concurrently to the reactor for co-precipitation. Throughout the process, the pH of the reaction environment was controlled to fluctuate between 11 and 11.5 by adjusting the flow rate of the mixed solution. The rotation speed was maintained at 500 rpm, and the temperature at 60℃. After 50 hours of reaction, the resulting solution was centrifuged sequentially with 3% NaOH and aqueous solution. The precipitate obtained after washing was dried to obtain NiSO4·6H2O. 0.8 Co 0.1 Mn 0.1 (OH)2 high-nickel ternary precursor; TaCl5, NbCl5, and LiOH were mixed in a molar ratio of 1:2.5:4 to prepare a mixed solution with a molar concentration of 0.2 mol / L (using deionized water as the solvent). Ni... 0.8 Co 0.1 Mn 0.1 (OH)2 is dispersed in a mixed solution and subjected to a first hydrothermal reaction at 150°C for 3 hours (pH ≥ 10.5 during the first hydrothermal reaction) to form a first lithium metal salt coating layer (Li3NbO4). Then, a second hydrothermal reaction is carried out at 150°C for 6 hours (pH < 10.5 during the second hydrothermal reaction) to form a second lithium metal salt coating layer (Li3NbO4). At the same time, Ta is doped into the interior of the high-nickel ternary precursor during the hydrothermal process. The obtained product is filtered, washed and dried to obtain an intermediate material. (2) Mix LiOH·H2O and intermediate materials evenly at a molar ratio of 1.05:1. In an oxygen atmosphere, heat the mixture to 300℃ at a heating rate of 3℃ / min and hold for 5h for a first calcination. Then heat the mixture to 600℃ at a heating rate of 2℃ / min and hold for 12h for a second calcination to obtain a doped and coated high-nickel ternary cathode material.

[0075] Example 9 This embodiment provides a doped and coated high-nickel ternary cathode material and its preparation method. The doped and coated high-nickel ternary cathode material includes a Ta-doped high-nickel ternary cathode material and a first Li3NbO4 coating layer on the surface (density 90%, thickness 8nm), and a second Li3NbO4 coating layer on the surface of the first Li3NbO4 coating layer (porosity 35%, thickness 17nm).

[0076] The preparation method includes the following steps: (1) According to Ni 0.8 Co 0.1 Mn0.1 To prepare a mixed metal sulfate solution (using deionized water as solvent) of NiSO4·6H2O, CoSO4·7H2O, and MnSO4·H2O with a molar concentration of 1.8 mol / L, 40 wt% NaOH solution and 22 wt% ammonia solution were mixed to obtain a mixed solution. The two solutions were then slowly added concurrently to the reactor for a co-precipitation reaction. Throughout the process, the pH of the reaction environment was controlled to fluctuate between 11 and 11.5 by adjusting the flow rate of the mixed solution. The rotation speed was maintained at 500 rpm, and the temperature at 60℃. After 20 hours of reaction, the resulting solution was centrifuged sequentially with 3% NaOH and aqueous solution. The washed precipitate was then dried to obtain NiSO4·6H2O. 0.8 Co 0.1 Mn 0.1 (OH)2 high-nickel ternary precursor; TaCl5, NbCl5, and LiOH were mixed in a molar ratio of 1:3.5:4 to prepare a mixed solution with a molar concentration of 0.1 mol / L (using deionized water as the solvent). Ni... 0.8 Co 0.1 Mn 0.1 (OH)2 is dispersed in a mixed solution and subjected to a first hydrothermal reaction at 200°C for 4 hours (pH ≥ 10.5 during the first hydrothermal reaction) to form a first lithium metal salt coating layer (Li3NbO4). Then, a second hydrothermal reaction is carried out at 200°C for 8 hours (pH < 10.5 during the second hydrothermal reaction) to form a second lithium metal salt coating layer (Li3NbO4). During the hydrothermal process, Ta is doped into the interior of the high-nickel ternary precursor. The resulting product is filtered, washed, and dried to obtain an intermediate material. (2) Mix LiOH·H2O and intermediate materials evenly at a molar ratio of 1.05:1. In an oxygen atmosphere, heat the mixture to 500℃ at a heating rate of 5℃ / min and hold for 3h for a first calcination. Then heat the mixture to 800℃ at a heating rate of 2.5℃ / min and hold for 8h for a second calcination to obtain a doped and coated high-nickel ternary cathode material.

[0077] Example 10 This embodiment provides a doped and coated high-nickel ternary cathode material and its preparation method. The difference between the doped and coated high-nickel ternary cathode material and that in Embodiment 1 is that the density of the first Li3NbO4 coating layer is 88% and the thickness is 10 nm, and the porosity of the second Li3NbO4 coating layer is 38% and the thickness is 20 nm. The remaining structure and parameters are the same as those in Embodiment 1.

[0078] The difference between the preparation method described herein and Example 1 is that the first hydrothermal reaction takes 6 hours and the second hydrothermal reaction takes 8 hours, while the remaining preparation methods and parameters are the same as in Example 1.

[0079] Example 11 This embodiment provides a doped and coated high-nickel ternary cathode material and its preparation method. The difference between the doped and coated high-nickel ternary cathode material and that in Embodiment 1 is that the density of the first Li3NbO4 coating layer is 93% and the thickness is 3nm, and the porosity of the second Li3NbO4 coating layer is 12% and the thickness is 10nm. The remaining structure and parameters are the same as those in Embodiment 1.

[0080] The difference between the preparation method described herein and Example 1 is that the first hydrothermal reaction takes 1.5 hours and the second hydrothermal reaction takes 4 hours, while the remaining preparation methods and parameters are consistent with those of Example 1.

[0081] Example 12 This embodiment provides a doped and coated high-nickel ternary cathode material and its preparation method. The difference between the preparation method and that in Example 1 is that in step (1), TaCl5, NbCl5 and LiOH are mixed in a molar ratio of 0.3:3:4, while the rest of the preparation methods and parameters are the same as in Example 1.

[0082] Example 13 This embodiment provides a doped and coated high-nickel ternary cathode material and its preparation method. The difference between the preparation method and that in Example 1 is that in step (1), TaCl5, NbCl5 and LiOH are mixed in a molar ratio of 2:3:4, while the rest of the preparation methods and parameters are the same as in Example 1.

[0083] Comparative Example 1 This comparative example provides a high-nickel ternary cathode material and its preparation method. The difference between the preparation method and that in Example 1 is that step (1) of preparing Ni is omitted. 0.8 Co 0.1 Mn 0.1 The step of dispersing (OH)2 in a mixed solution to prepare intermediate materials, and directly dispersing Ni 0.8 Co 0.1 Mn 0.1 (OH)2 and LiOH·H2O were mixed uniformly at a molar ratio of 1:1.05. The mixture was then heated to 500℃ at a heating rate of 5℃ / min and held for 5 hours in an oxygen atmosphere for a first calcination. The mixture was then heated to 750℃ at a heating rate of 3℃ / min and held for 10 hours for a second calcination to obtain a high-nickel ternary cathode material. The remaining preparation methods and parameters were consistent with those in Example 1.

[0084] Comparative Example 2 This comparative example provides a doped high-nickel ternary cathode material and its preparation method. The difference between the preparation method and that of Example 1 is that TaCl5 and LiOH are mixed at a molar ratio of 1:4 to prepare a mixed solution with a molar concentration of 0.1 mol / L. Ni... 0.8 Co 0.1 Mn 0.1 (OH)2 was dispersed in the above mixed solution to obtain a doped high-nickel ternary cathode material. The remaining preparation methods and parameters were the same as in Example 1.

[0085] Comparative Example 3 This comparative example provides a coated high-nickel ternary cathode material and its preparation method. The difference between this preparation method and that of Example 1 is that NbCl5 and LiOH are mixed in a molar ratio of 3:4 to prepare a mixed solution with a molar concentration of 0.1 mol / L. Ni... 0.8 Co 0.1 Mn 0.1 (OH)2 is dispersed in the above mixed solution to obtain a coated high-nickel ternary cathode material. The remaining preparation methods and parameters are consistent with those in Example 1.

[0086] Application Examples 1-13 and Comparative Application Examples 1-3 The cathode materials provided in Examples 1-13 and Comparative Examples 1-3, along with Li6PS5Cl and carbon black, were mixed in a ratio of 69:30:1 to serve as the cathode material for solid-state batteries and used to assemble solid-state batteries. Li6PS5Cl was used as the solid electrolyte and synthesized by the following method: stoichiometric Li2S, P2S5, and LiCl were mixed with 50 zirconium dioxide balls (U=10mm) in a zirconium dioxide pot. After ball milling at 500 rpm for 14 hours, a Li6PS5Cl precursor was obtained. After ball milling, the mixture was sealed in a quartz bottle and kept under inert conditions, then annealed at 450°C for 8 hours to obtain the Li6PS5Cl solid electrolyte. Using graphite as the anode, solid-state batteries were finally fabricated on an electrolyte / cathode disk in a glove box filled with Ar at a pressure of 6.8 MPa, corresponding to Application Examples 1-13 and Comparative Application Examples 1-3, respectively.

[0087] The electrochemical performance of solid-state batteries corresponding to use cases 1-13 and comparative application examples 1-3 is tested using the following specific methods: at 25°C, 1C rate, and a voltage range of 2.8V-4.3V, the initial discharge capacity and capacity retention after 50 cycles are tested. Specific test parameters are shown in Table 1.

[0088] Table 1 The test results show that: (1) As can be seen from Application Examples 1-9, the present invention simultaneously suppresses bulk structure collapse (H3 phase transition) and interfacial side reactions through the synergistic effect of bulk molecular-level doping of metal and lithium metal salt coating layer; the first metal element is incorporated into the high-nickel ternary cathode material, occupies the transition metal site to form the first metal element -O bond, suppresses the release of lattice oxygen, and reduces Li ＋ / Ni 2＋ The mixing of materials prevents the H2→H3 phase transition during deep charge and discharge, thus improving the material's cycle performance. The lithium metal salt coating layer has both ionic and electronic conduction properties, which improves rate performance while ensuring interface stability. It also eliminates the blockage of ion migration by traditional inert coatings. In this way, the structural stability, interface problems, and electrochemical performance of the cathode material are improved through the synergistic effect of doping and coating. Specifically, the initial discharge capacity is 170mAh / g~188mAh / g, and the capacity retention rate is 80.5%~92.5%.

[0089] Furthermore, the synergistic effect of the bulk metal molecular-level doping and the lithium metal salt coating layer of the present invention can effectively improve the electrochemical performance of high-nickel ternary materials with different nickel contents, demonstrating good versatility and application prospects.

[0090] (2) As can be seen from Application Examples 1 and 10-11, the present invention regulates the thickness of the first lithium metal acid salt coating layer to 5nm-8nm, which can effectively isolate the direct contact between the high-nickel cathode material and the solid electrolyte, suppress interfacial side reactions, and ensure that it does not significantly hinder the migration of lithium ions, thereby achieving a balance between interfacial stability and ionic conductivity. The present invention regulates the thickness of the second lithium metal acid salt coating layer to 12nm-17nm, which can provide sufficient electronic conduction pathways while maintaining the porous structure of the coating layer itself, thereby ensuring the rapid migration of lithium ions and achieving stable and efficient interfacial contact with the solid electrolyte and conductive agent. When the coating layer thickness is too thin (Application Example 11), it will affect the cycle performance; when the coating layer thickness is too thick (Application Example 10), it will affect the first discharge specific capacity, which also shows that the coating layer thickness regulated by the present invention is the key to further achieving a balance between high discharge specific capacity and long cycle life.

[0091] (3) As can be seen from Application Example 1 and Application Examples 12-13, in the mixed solution of step (1) of the present invention, the molar ratio of the first metal element salt, the second metal element salt and the first lithium source is (0.5-1.5):(2-4):(4-6), so that the content of the doped element is within the above-mentioned better range, which can ensure that the Ta element is effectively doped into the bulk phase to stabilize the structure.

[0092] (4) Through Application Example 1 and Comparative Application Examples 1-3, it can be seen from the first discharge capacity and capacity retention rate of the battery that neither doping nor coating the high-nickel ternary cathode material, or only doping or only coating, can effectively improve the electrochemical performance. That is, a single modification method cannot solve the dual problems of bulk structure degradation and interfacial side reactions faced by high-nickel ternary cathode materials in solid-state batteries. However, through the synergistic effect of the metal bulk molecular-level doping and lithium metal salt coating layer of the present invention, a breakthrough in comprehensive performance can be achieved.

[0093] In summary, this invention simultaneously suppresses bulk structure collapse (H3 phase transition) and interfacial side reactions through the synergistic effect of bulk molecular-level doping of the metal phase and lithium metalate coating; the incorporation of a first metal element into the high-nickel ternary cathode material occupies transition metal sites to form a first metal element -O bond, suppressing the release of lattice oxygen and reducing Li ＋ / Ni 2＋ The mixing of materials prevents the H2→H3 phase transition during deep charge and discharge, thus improving the material's cycle performance. The lithium metal salt coating layer has both ionic and electronic conduction properties, which improves rate performance while ensuring interface stability. It also eliminates the blockage of ion migration by traditional inert coatings. In this way, the structural stability, interface problems, and electrochemical performance of high-nickel ternary cathode materials are improved through the synergistic effect of doping and coating.

[0094] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A doped and coated high-nickel ternary cathode material, characterized in that, The doped and coated high-nickel ternary cathode material includes a high-nickel ternary cathode material and a lithium metal salt coating layer located on the surface of the high-nickel ternary cathode material; The high-nickel ternary cathode material is doped with a first metallic element, which includes Ta. The lithium metal salt coating layer includes a second metal element, which includes Nb.

2. The doped and coated high-nickel ternary cathode material according to claim 1, characterized in that, The lithium metal salt coating layer includes a first lithium metal salt coating layer and a second lithium metal salt coating layer; Preferably, the first lithium metal acid salt coating layer is located on the surface of the high-nickel ternary cathode material, and the second lithium metal acid salt coating layer is located on the surface of the first lithium metal acid salt coating layer.

3. The doped and coated high-nickel ternary cathode material according to claim 2, characterized in that, The first lithium metal salt coating layer is a dense layer; Preferably, the density of the first lithium metal salt coating layer is ≥90%; Preferably, the thickness of the first lithium metal salt coating layer is 5 nm to 8 nm.

4. The doped and coated high-nickel ternary cathode material according to claim 2, characterized in that, The second lithium metal salt coating layer is a porous layer; Preferably, the porosity of the second lithium metal salt coating layer is 15%~35%; Preferably, the thickness of the second lithium metal salt coating layer is 12nm~17nm.

5. A method for preparing a doped and coated high-nickel ternary cathode material according to any one of claims 1 to 4, characterized in that, The preparation method includes the following steps: (1) The high-nickel ternary precursor was dispersed in a mixed solution and subjected to a hydrothermal reaction to obtain an intermediate material; The mixed solution includes a first metal element salt, a second metal element salt, a first lithium source, and a solvent; The intermediate material includes a high-nickel ternary precursor and a lithium metal salt coating layer located on the surface of the high-nickel ternary precursor. The high-nickel ternary precursor is doped with a first metal element, which includes Ta. The lithium metal salt coating layer includes a second metal element, which includes Nb. (2) The second lithium source and the intermediate material described in step (1) are mixed evenly and then calcined to obtain a doped and coated high-nickel ternary cathode material.

6. The preparation method according to claim 5, characterized in that, The general chemical formula of the high-nickel ternary precursor in step (1) is Ni x Co y Mn 1-x-y (OH)2, where 0.8 ≤ x < 1, 0 < y < 0.2; Preferably, in the mixed solution of step (1), the molar ratio of the first metal element salt, the second metal element salt and the first lithium source is (0.5~1.5):(2~4):(4~6); Preferably, the molar concentration of the mixed solution is 0.05 mol / L to 0.2 mol / L.

7. The preparation method according to claim 5 or 6, characterized in that, The hydrothermal reaction in step (1) includes a first hydrothermal reaction and a second hydrothermal reaction; Preferably, the total time for the hydrothermal reaction in step (1) is 8h~12h; Preferably, the first hydrothermal reaction takes 3 to 5 hours. Preferably, after the first hydrothermal reaction is completed, a first lithium metal salt coating layer is obtained; Preferably, after the second hydrothermal reaction is completed, a second lithium metal salt coating layer is obtained; Preferably, the first hydrothermal reaction and the second hydrothermal reaction are at the same temperature; Preferably, the temperatures of the first hydrothermal reaction and the second hydrothermal reaction are both 150°C to 200°C.

8. The preparation method according to any one of claims 5 to 7, characterized in that, Step (1) The first metal element salt includes tantalum salt; Preferably, in step (1), the second metal element salt includes a niobium salt; Preferably, in step (1), the first lithium source includes lithium hydroxide.

9. The preparation method according to any one of claims 5 to 8, characterized in that, Step (2) The second lithium source includes at least one of lithium hydroxide, lithium nitrate or lithium acetate, preferably lithium hydroxide; Preferably, in step (2), the molar ratio of the intermediate material to the second lithium source is 1:(1.03~1.05); Preferably, the calcination in step (2) includes primary calcination and secondary calcination; Preferably, the calcination in step (2) is carried out in an oxygen atmosphere; Preferably, the heating rate of the first calcination in step (2) is 3℃ / min to 5℃ / min; Preferably, the holding temperature for the first calcination in step (2) is 300℃~500℃; Preferably, the holding time for the first calcination in step (2) is 3h~5h; Preferably, the heating rate of the secondary calcination in step (2) is 2℃ / min~3℃ / min; Preferably, the holding temperature for the secondary calcination in step (2) is 600℃~800℃; Preferably, the heat preservation time for the secondary calcination in step (2) is 8h~12h.

10. A lithium solid-state battery, characterized in that, The lithium solid-state battery includes the doped and coated high-nickel ternary cathode material as described in any one of claims 1 to 4, or the doped and coated high-nickel ternary cathode material prepared by the preparation method described in any one of claims 5 to 9.

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