Ternary positive electrode material precursor and preparation method and application thereof
By introducing a core-shell structure into the ternary cathode material precursor, with a core doped with Sn and Al in a nickel-cobalt-manganese hydroxide and a shell with a tungsten-based coating, the cycle performance and structural stability issues of nickel-rich ternary cathode materials are solved, resulting in superior electrochemical performance and extended battery life.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-23
- Publication Date
- 2026-03-27
AI Technical Summary
Existing nickel-rich ternary cathode materials have problems in terms of cycle performance and structural stability, such as lithium-nickel mixing, lattice expansion and contraction, increased battery impedance and side reactions, which lead to capacity decay and reduced rate performance.
The ternary cathode material precursor with a core-shell structure has a core of nickel-cobalt-manganese hydroxide doped with Sn and Al, and a shell of tungsten-based coating. The synergistic effect of Sn and Al suppresses lithium-nickel mixing, Al enhances structural stability, and the tungsten base layer constructs a highly ionicly conductive interface protection barrier to isolate corrosive components of the electrolyte and promote lithium-ion transport.
It improves the cycle performance and structural stability of the material, suppresses voltage decay, enhances interfacial impedance and lithium-ion transport efficiency, and improves the overall performance of the battery.
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Abstract
Description
Technical Field
[0001] This invention belongs to the field of battery materials technology, specifically relating to a ternary cathode material precursor, its preparation method, and its application. Background Technology
[0002] Nickel-rich ternary cathode materials include nickel-cobalt-manganese lithium oxide and nickel-cobalt-aluminate materials, with nickel content generally exceeding 50%. Nickel is primarily the electrochemically active element; increased nickel content helps improve the material's capacity, thereby increasing energy density. The presence of cobalt reduces electrochemical polarization and improves rate performance, but excessive cobalt can reduce reversible capacity. Manganese ensures structural and thermal stability, reducing costs and improving safety, but excessive manganese can disrupt the material's original layered structure. Due to the high nickel content, nickel-rich ternary cathode materials exhibit high reversible discharge specific capacity, but their cycle performance deteriorates. This is mainly due to unstable surface properties, structural defects, lithium-nickel mixing, intergranular cracks, and micro-strain. To address these issues, researchers have proposed numerous modification strategies, primarily including surface and interface engineering, bulk doping, and morphology control.
[0003] Current nickel-cobalt-manganese ternary cathode materials still have some problems that urgently need to be solved, such as low initial charge-discharge efficiency and poor rate cycle performance. These problems will be the focus of future research on the modification of nickel-cobalt-manganese ternary cathode materials. The precursor of conventional nickel-cobalt-manganese ternary cathode materials is a secondary spherical particle formed by the agglomeration of primary particles of fine grains. Its structure is dense and its specific surface area is low. The ternary cathode material prepared subsequently will also inherit these characteristics. As the number of cycles of lithium-ion batteries increases, the primary particles in the secondary spheres have different crystal orientations and slip planes. The anisotropy of lattice expansion and contraction between grains may lead to breakage, pulverization, and structural collapse caused by the expansion or contraction of secondary particles in the later stages of cycling. This results in increased battery impedance, reduced active components, and exacerbated side reactions with the electrolyte, leading to severe capacity decay and a sharp decline in rate and cycle performance.
[0004] Therefore, how to significantly improve the electrochemical performance of nickel-cobalt-manganese ternary cathode materials is a technical problem that urgently needs to be solved. Summary of the Invention
[0005] To address the shortcomings of existing technologies, the present invention aims to provide a ternary cathode material precursor, its preparation method, and its application. This invention designs a core-shell structured ternary cathode material precursor, wherein the core is a doped nickel-cobalt-manganese hydroxide doped with element M. Sn and Al in the M element work synergistically to suppress lithium-nickel mixing: Sn, due to its ionic radius being close to that of Ni, preferentially occupies lattice defect sites on nickel, reducing lattice dislocations during lithium-ion insertion / extraction; Al, through bulk doping, strengthens the layered framework, reducing the anisotropy of lattice expansion and contraction during cycling and improving structural stability. The outer shell is a tungsten-based coating layer, which constructs a dense and highly ionicly conductive interfacial barrier. This not only isolates corrosive components in the electrolyte from direct contact with the core, suppresses side reactions between surface residual alkali and the electrolyte, and reduces interfacial impedance, but also allows the high-valence ions of tungsten to regulate the surface electronic state density, promoting rapid lithium-ion transport at the interface while preventing the dissolution of transition metals from the core. The ternary cathode material prepared based on this exhibits excellent cycling performance, and voltage decay is effectively suppressed.
[0006] To achieve this objective, the present invention adopts the following technical solution:
[0007] In a first aspect, the present invention provides a ternary cathode material precursor, the ternary cathode material precursor comprising a core and a tungsten-based coating layer covering the surface of the core;
[0008] The core is a doped nickel-cobalt-manganese hydroxide, which is doped with element M, including Sn and Al.
[0009] This invention designs a core-shell structured ternary cathode material precursor, wherein the core is a doped nickel-cobalt-manganese hydroxide doped with element M. Sn and Al in the M element work synergistically to suppress lithium-nickel mixing: Sn, due to its ionic radius being close to that of Ni, preferentially occupies lattice defect sites on nickel, reducing lattice dislocations during lithium-ion insertion / extraction; Al, through bulk doping, strengthens the layered framework, reducing the anisotropy of lattice expansion and contraction during cycling and improving structural stability. The outer shell is a tungsten-based coating layer, which constructs a dense and highly ionicly conductive interfacial barrier. This not only isolates corrosive components in the electrolyte from direct contact with the core, suppresses side reactions between surface residual alkali and the electrolyte, and reduces interfacial impedance, but also allows the high-valence ions of tungsten to regulate the surface electronic state density, promoting rapid lithium-ion transport at the interface while preventing the dissolution of transition metals from the core. The ternary cathode material prepared based on this exhibits excellent cycling performance, and voltage decay is effectively suppressed.
[0010] Preferably, the particle size D50 of the kernel is 8-10 μm, for example, it can be 8 μm, 8.5 μm, 9 μm, 9.5 μm or 10 μm.
[0011] Preferably, based on the amount of the doped nickel-cobalt-manganese hydroxide, the doping amount of the M element is 1000-2000 ppm, for example, it can be 1000 ppm, 1500 ppm or 2000 ppm.
[0012] In this invention, the appropriate doping amount of element M is crucial for stabilizing the material structure and improving cycling performance. Too low a doping amount may fail to provide effective structural support and improve ion migration channels; while too high a doping amount may disrupt the order of the main lattice, introducing excessive defects and leading to decreased capacity or deteriorated kinetic performance. Therefore, controlling the doping amount between 1000-2000 ppm is an optimized balance point, aiming to obtain the maximum performance gain with the minimum addition amount.
[0013] Preferably, the molar ratio of Sn to Al is (1.5-2.5):1, for example, it can be 1.5:1, 2:1 or 2.5:1, etc.
[0014] In this invention, when Sn and Al are used as doping elements in the core, Al doping helps stabilize the layered structure and suppress phase transitions; the introduction of Sn can generate a "pinning effect" through its large ionic radius, further suppressing the expansion and contraction of the lattice during cycling, thereby jointly improving the structural stability and cycle life of the material.
[0015] Preferably, the thickness of the tungsten-based coating layer is 0.5-2.5 μm, for example, it can be 0.5 μm, 1 μm, 1.5 μm, 2 μm or 2.5 μm.
[0016] In this invention, if the coating layer is too thin, it may not be able to form a continuous and effective protective layer, and its effects of improving wear resistance and isolating electrolyte corrosion will be greatly reduced; if the coating layer is too thick, it may lead to increased stress accumulation inside the coating layer, which may easily cause cracks or even peel off from the substrate under cyclic or mechanical stress, thereby damaging the overall performance and reliability of the material; at the same time, an excessively thick coating layer may also increase the resistance to lithium ion diffusion, affecting rate performance.
[0017] Preferably, the tungsten-based coating layer includes tungsten hydroxide.
[0018] In a second aspect, the present invention provides a method for preparing a ternary cathode material precursor as described in the first aspect, the method comprising the following steps:
[0019] A nickel-cobalt-manganese mixed metal salt solution, a precipitant, a complexing agent, and an M salt solution are fed concurrently into a base liquid to carry out a first coprecipitation reaction. When the particle size D50 of the product particles reaches d1, the feeding of the nickel-cobalt-manganese mixed metal salt solution and the M salt solution is stopped to obtain crystal nuclei. The M salt solution includes a Sn salt solution and an Al salt solution.
[0020] While the precipitant and complexing agent are being introduced, a W salt solution is introduced into the bottom liquid to carry out a second coprecipitation reaction. The reaction ends when the particle size D50 of the product particles is d2, and the ternary cathode material precursor is obtained.
[0021] The preparation method provided by this invention is simple, highly controllable, and low in cost, which is conducive to large-scale application.
[0022] Preferably, the nickel-cobalt-manganese mixed metal salt solution is a nickel-rich solution.
[0023] Preferably, during the first coprecipitation reaction, the pH of the reaction system is 9.5-11.5, for example, it can be 9.5, 10, 10.5, 11 or 11.5, etc., and preferably 10.2-10.8.
[0024] It should be noted that the pH of the reaction system is precisely controlled using a precipitant flow control system. That is, after the required pH for the reaction is set in the system, the system automatically adjusts the precipitant flow rate to maintain pH stability. This adjustment method minimizes human intervention and reduces operational errors. The same principle applies to the following systems.
[0025] Preferably, during the first coprecipitation reaction, the reaction temperature is 40-65℃, for example, it can be 40℃, 45℃, 50℃, 55℃, 60℃ or 65℃, etc.
[0026] Preferably, d1 is 8-10 μm, for example, it can be 8 μm, 8.5 μm, 9 μm, 9.5 μm or 10 μm, etc.
[0027] Preferably, the Sn salt solution comprises a sodium stannate solution.
[0028] Preferably, the Al salt solution comprises a sodium aluminate solution.
[0029] Preferably, the W salt solution comprises an ammonium tungstate solution.
[0030] Preferably, the precipitant comprises liquid alkali.
[0031] Preferably, the complexing agent comprises ammonia.
[0032] Preferably, during the second coprecipitation reaction, the pH of the reaction system is 9.5-11.5, for example, it can be 9.5, 10, 10.5, 11 or 11.5, etc.
[0033] Preferably, during the second coprecipitation reaction, the reaction temperature is 40-65℃, for example, it can be 40℃, 45℃, 50℃, 55℃, 60℃ or 65℃, etc.
[0034] Preferably, d2 is 8.5-10.5μm, for example, it can be 8.5μm, 9μm, 9.5μm, 10μm or 10.5μm, etc.
[0035] Preferably, during the first coprecipitation reaction and the second coprecipitation reaction, the reaction atmosphere is a low-oxygen inert mixed atmosphere.
[0036] Preferably, the low-oxygen inert mixed atmosphere includes oxygen and an inert gas. For example, the inert gas may be nitrogen. For example, the low-oxygen inert mixed atmosphere may be a mixture of air and nitrogen.
[0037] Preferably, the oxygen concentration in the low-oxygen inert mixed atmosphere is 0.5-1.5 vol%, for example, it can be 0.5 vol%, 1 vol%, or 1.5 vol%.
[0038] It should be noted that in the production process of ternary precursors, inert gas protection is required to prevent the oxidation of metal ions. However, for product requirements, a mixture of trace amounts of oxygen and inert gas is sometimes introduced to alter the reaction environment. During the reaction stage of ternary precursor preparation, the oxygen concentration must be strictly controlled in real time. Existing technologies for precise oxygen content control are complex and involve high labor costs. Therefore, in this application, the oxygen concentration is precisely controlled using an oxygen content controller to avoid errors caused by human operation.
[0039] In this invention, a specific concentration of oxygen is beneficial for controlling the valence state of metal ions at the molecular scale to suppress harmful cation mixing, optimizing the morphology and specific surface area of precursor particles at the microscale, and ultimately achieving higher coulombic efficiency, better cycle stability, and especially capacity retention at high voltage in macroscopic electrochemical performance.
[0040] Preferably, the pH of the base solution is 10.5-11, for example, it can be 10.5, 10.6, 10.7, 10.8, 10.9 or 11.
[0041] Preferably, the preparation method includes the following steps:
[0042] (1) A nickel-cobalt-manganese mixed metal salt solution, a precipitant, a complexing agent, and an M salt solution are fed concurrently into the reactor containing the bottom liquid. The flow rate is automatically adjusted by a precipitant flow control system to maintain the pH of the reaction system at 9.5-11.5 and the reaction temperature at 40-65℃. Stirring is started simultaneously to carry out the first co-precipitation reaction. When the particle size D50 of the product is d1, the feeding of the nickel-cobalt-manganese mixed metal salt solution and the M salt solution is stopped to obtain crystal nuclei. The M salt solution includes Sn salt solution and Al salt solution; the precipitant includes liquid alkali; and the complexing agent includes ammonia. During the co-precipitation reaction, the reaction atmosphere is a low-oxygen inert mixed atmosphere, which includes oxygen and inert gas. The oxygen concentration is controlled at 0.5-1.5 vol% by an oxygen content meter located above the reactor (function: to automatically adjust the gas flow rate through the control system based on the oxygen content meter data, so as to stabilize the oxygen content in the reactor). The stirring speed is 200-500 rpm (e.g., 200 rpm, 300 rpm, 400 rpm, or 500 rpm, etc.). The d1 is 8-10 μm.
[0043] (2) While maintaining the introduction of the precipitant and complexing agent, the W salt solution is introduced into the bottom liquid, and the flow rate is automatically adjusted by the precipitant flow control system to control the pH of the reaction system to 9.5-11.5 and the reaction temperature to 40-65℃. At the same time, stirring is turned on to carry out the second coprecipitation reaction. When the particle size D50 of the product particles is d2, the reaction ends. Then, washing and drying are performed to obtain the ternary cathode material precursor. The W salt solution includes ammonium tungstate solution. During the first coprecipitation reaction, the reaction atmosphere is a low-oxygen inert mixed atmosphere, which includes oxygen and inert gas. The oxygen concentration is controlled by an oxygen content tester located above the reactor and is controlled to be 0.5-1.5 vol%. The d2 is 8.5-10.5 μm.
[0044] Thirdly, the present invention provides a ternary cathode material, which is prepared by mixing and sintering a ternary cathode material precursor as described in the first aspect with a lithium source. For example, the lithium source may be lithium carbonate, etc.
[0045] Preferably, the outer surface of the ternary cathode material is further coated with a metal oxide-phosphate co-coating layer.
[0046] Preferably, the preparation steps of the metal oxide-phosphate co-coating layer include:
[0047] A ternary cathode material, a metal oxide, and a phosphate are mixed and heat-treated to obtain a ternary cathode material with a metal oxide-phosphate co-coating layer on its surface.
[0048] Preferably, the mixing method includes ball milling.
[0049] Preferably, the heat treatment temperature is 900-1100℃, for example, 900℃, 1000℃ or 1100℃, and the time is 8-12h, for example, 8h, 9h, 10h, 11h or 12h.
[0050] In this invention, the metal oxide-phosphate co-coating layer can greatly increase the energy barrier for oxygen release from the ternary cathode material, thereby stabilizing the surface oxygen of the Li-rich material.
[0051] Preferably, the metal oxide includes aluminum oxide.
[0052] Preferably, the phosphate comprises lanthanum phosphate.
[0053] Preferably, in the metal oxide-phosphate co-coating layer, the mass ratio of metal oxide to phosphate is 1:(0.8-1.5), for example, it can be 1:0.8, 1:0.9, 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4 or 1:1.5, etc.
[0054] In this invention, an appropriate mass ratio is beneficial for constructing a functionally synergistic composite protective layer. The electronically conductive phase (metal oxide) and the ionicly conductive phase (phosphate) can synergistically enhance the electronic-ionic mixed conductivity of the material. It is also beneficial for forming a dense and stable interface structure. By obtaining a uniform, dense coating layer that is firmly bonded to the matrix, electrolyte decomposition and transition metal dissolution can be effectively suppressed. Furthermore, it is beneficial for achieving the best performance balance. That is, within a limited total amount of coating layer added, by optimizing the synergistic ratio, the maximum improvement in cycle stability, rate performance, and safety can be obtained at the lowest capacity cost.
[0055] Fourthly, the present invention provides a lithium-ion battery, wherein the positive electrode of the lithium-ion battery includes a ternary positive electrode material as described in the third aspect, or includes a ternary positive electrode material prepared by sintering a modified ternary precursor with a lithium source as described in the first aspect.
[0056] The numerical range described in this invention includes not only the point values listed above, but also any point values within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values included in the range.
[0057] Compared with the prior art, the present invention has the following beneficial effects:
[0058] (1) This invention designs a core-shell structured ternary cathode material precursor, wherein the core is a doped nickel-cobalt-manganese hydroxide doped with element M. Sn and Al in element M work together to suppress lithium-nickel mixing. Sn, due to its ionic radius being close to that of Ni, can preferentially occupy lattice defect sites on nickel sites, reducing lattice dislocations during lithium-ion insertion / extraction. Al strengthens the layered structure framework through bulk doping, reducing the anisotropy of lattice expansion and contraction during cycling and improving structural stability. The outer shell is a tungsten-based coating layer, which can construct a dense and highly ionicly conductive interface protection barrier. This not only isolates the corrosive components in the electrolyte from direct contact with the core, suppresses the side reactions of residual alkali on the surface and the electrolyte, and reduces interface impedance, but also allows the high-valence ions of tungsten to regulate the surface electronic state density, promoting the rapid transport of lithium ions at the interface and preventing the dissolution of transition metals in the core. The ternary cathode material prepared based on this has excellent cycling performance and voltage decay is effectively suppressed.
[0059] (2) The preparation method provided by the present invention is simple, low in cost and highly efficient. Detailed Implementation
[0060] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.
[0061] Example 1
[0062] This embodiment provides a ternary cathode material precursor, which includes a core and a tungsten-based coating layer covering the surface of the core;
[0063] The core is a doped nickel-cobalt-manganese hydroxide with a molar ratio of nickel, cobalt, and manganese of 8:1:1. The doped nickel-cobalt-manganese hydroxide is doped with element M, which includes Sn and Al. The particle size D50 of the core is 8 μm. Based on the molar amount of the doped nickel-cobalt-manganese hydroxide, the doping amount of element M is 1500 ppm, and the molar ratio of Sn to Al is 2:1. The thickness of the tungsten-based coating layer is 0.5 μm. The tungsten-based coating layer includes tungsten hydroxide.
[0064] This embodiment also provides a method for preparing the above-mentioned ternary cathode material precursor, the preparation method comprising the following steps:
[0065] (1) Preparation of crystal nuclei:
[0066] (a) Preparation of nickel-cobalt-manganese mixed metal salt solution: Prepared according to the molar ratio of Ni:Co:Mn of 8:1:1.
[0067] Prepare a solution of 32% caustic soda and 18% ammonia water by volume ratio of 8:3.
[0068] Preparation of the base solution: First, add 600L of pure water to the reactor, then add ammonia water to make the pH value of the base solution reach 10.8, and keep the temperature of the reactor at 65℃.
[0069] (b) The nickel-cobalt-manganese mixed metal salt solution at a flow rate of 40 L / h, the sodium stannate solution at a flow rate of 2 L / h, and the sodium aluminate solution at a flow rate of 1.5 L / h are fed into the reactor containing the bottom liquid at the same flow rate. Liquid alkali and ammonia are added simultaneously, and the flow rates are automatically adjusted by the precipitant flow control system to control the pH of the reaction system at 10.5. Stirring is started at 300 rpm to carry out the first coprecipitation reaction. When the particle size D50 of the product particles is d1, the feeding of the nickel-cobalt-manganese mixed metal salt solution, sodium stannate solution, and sodium aluminate solution is stopped to obtain crystal nuclei. During the first coprecipitation reaction, the reaction atmosphere is a low-oxygen nitrogen mixed atmosphere, which includes oxygen and nitrogen. The oxygen concentration is controlled by an oxygen content tester located above the reactor and is controlled to be 1 vol%; d1 is 8 μm.
[0070] (2) While maintaining the flow of liquid alkali and ammonia, an ammonium tungstate solution with a flow rate of 1 L / h is introduced into the bottom liquid, and the flow rate is automatically adjusted by the precipitant flow control system to control the pH of the reaction system to 10.5 and the reaction temperature to 65°C. At the same time, the stirring is turned on at a speed of 300 rpm to carry out the second coprecipitation reaction. When the particle size D50 of the product particles is d2, the reaction ends. Then, the product is centrifuged and washed, and then placed in a hot air circulating drying oven and dried at a temperature of 130°C. After sieving, the ternary cathode material precursor is obtained. In the process of the first coprecipitation reaction, the reaction atmosphere is a low-oxygen nitrogen mixed atmosphere. The low-oxygen inert mixed atmosphere includes oxygen and nitrogen. The oxygen concentration is controlled by an oxygen content tester located above the reaction vessel and is controlled to be 1 vol%. The d2 is 8.5 μm.
[0071] This embodiment also provides a ternary cathode material, which is prepared by sintering the ternary cathode material precursor and lithium carbonate as described above. The specific steps include:
[0072] (i) The ground and sieved lithium carbonate is mixed with the ternary precursor at a molar ratio of lithium ions to total transition metal ions of 1.2:0.8 to obtain a mixture.
[0073] (ii) The mixture is placed in a roller kiln, heated to 50°C and held for 8 hours, then heated to 1000°C and held for 24 hours, and then slowly cooled to room temperature of 25°C to obtain the ternary cathode material.
[0074] Example 2
[0075] This embodiment provides a ternary cathode material precursor, which includes a core and a tungsten-based coating layer covering the surface of the core;
[0076] The core is a doped nickel-cobalt-manganese hydroxide with a molar ratio of nickel, cobalt, and manganese of 8:1:1. The doped nickel-cobalt-manganese hydroxide is doped with element M, which includes Sn and Al. The particle size D50 of the core is 9 μm. Based on the molar amount of the doped nickel-cobalt-manganese hydroxide, the doping amount of element M is 1000 ppm, and the molar ratio of Sn to Al is 1.5:1. The thickness of the tungsten-based coating layer is 1.5 μm, and the tungsten-based coating layer includes tungsten hydroxide.
[0077] This embodiment also provides a method for preparing the above-mentioned ternary cathode material precursor, the preparation method comprising the following steps:
[0078] (1) Preparation of crystal nuclei:
[0079] (a) Preparation of nickel-cobalt-manganese mixed metal salt solution: Prepared according to the molar ratio of Ni:Co:Mn of 8:1:1.
[0080] Prepare a solution of 32% caustic soda and 18% ammonia water by volume ratio of 8:3.
[0081] Preparation of the base solution: First, add 600L of pure water to the reactor, then add ammonia water to make the pH value of the base solution reach 10.8, and keep the temperature of the reactor at 50℃.
[0082] (b) The nickel-cobalt-manganese mixed metal salt solution at a flow rate of 40 L / h, the sodium stannate solution at a flow rate of 1.5 L / h, and the sodium aluminate solution at a flow rate of 1 L / h are fed into the reactor containing the bottom liquid at the same flow rate. Liquid alkali and ammonia are added simultaneously, and the flow rates are automatically adjusted by the precipitant flow control system to control the pH of the reaction system at 10.2. Stirring is started at 200 rpm to carry out the first coprecipitation reaction. When the particle size D50 of the product particles is d1, the feeding of the nickel-cobalt-manganese mixed metal salt solution, sodium stannate solution, and sodium aluminate solution is stopped to obtain crystal nuclei. During the first coprecipitation reaction, the reaction atmosphere is a low-oxygen nitrogen mixed atmosphere, which includes oxygen and nitrogen. The oxygen concentration is controlled by an oxygen content tester located above the reactor and is controlled to be 0.5 vol%; d1 is 9 μm.
[0083] (2) While maintaining the flow of liquid alkali and ammonia, an ammonium tungstate solution with a flow rate of 3 L / h is introduced into the bottom liquid, and the flow rate is automatically adjusted by the precipitant flow control system to control the pH of the reaction system to 10.2 and the reaction temperature to 50°C. At the same time, the stirring is turned on at a speed of 200 rpm to carry out the second coprecipitation reaction. When the particle size D50 of the product particles is d2, the reaction ends. Then, the product is centrifuged and washed, and then placed in a hot air circulating drying oven and dried at a temperature of 130°C. After sieving, the ternary cathode material precursor is obtained. In the process of the first coprecipitation reaction, the reaction atmosphere is a low-oxygen nitrogen mixed atmosphere. The low-oxygen inert mixed atmosphere includes oxygen and nitrogen. The oxygen concentration is controlled by an oxygen content tester located above the reaction vessel and is controlled to be 0.5 vol%. The d2 is 10.5 μm.
[0084] This embodiment also provides a ternary cathode material, which is prepared by sintering the ternary cathode material precursor and lithium carbonate as described above. The specific steps include:
[0085] (i) The ground and sieved lithium carbonate is mixed with the ternary precursor at a molar ratio of lithium ions to total transition metal ions of 1.2:0.8 to obtain a mixture.
[0086] (ii) The mixture is placed in a roller kiln, heated to 50°C and held for 8 hours, then heated to 1000°C and held for 24 hours, and then slowly cooled to room temperature of 25°C to obtain the ternary cathode material.
[0087] Example 3
[0088] This embodiment provides a ternary cathode material precursor, which includes a core and a tungsten-based coating layer covering the surface of the core;
[0089] The core is a doped nickel-cobalt-manganese hydroxide with a molar ratio of nickel, cobalt, and manganese of 8:1:1. The doped nickel-cobalt-manganese hydroxide is doped with element M, which includes Sn and Al. The core has a particle size D50 of 8.5 μm. Based on the molar amount of the doped nickel-cobalt-manganese hydroxide, the doping amount of element M is 2000 ppm, and the molar ratio of Sn to Al is 2.5:1. The tungsten-based coating layer has a thickness of 1 μm and includes tungsten hydroxide.
[0090] This embodiment also provides a method for preparing the above-mentioned ternary cathode material precursor, the preparation method comprising the following steps:
[0091] (1) Preparation of crystal nuclei:
[0092] (a) Preparation of nickel-cobalt-manganese mixed metal salt solution: Prepared according to the molar ratio of Ni:Co:Mn of 8:1:1.
[0093] Prepare a solution of 32% caustic soda and 18% ammonia water by volume ratio of 8:3.
[0094] Preparation of the base solution: First, add 600L of pure water to the reactor, then add ammonia water to make the pH value of the base solution reach 10.8, and keep the temperature of the reactor at 40℃.
[0095] (b) The nickel-cobalt-manganese mixed metal salt solution at a flow rate of 40 L / h, the sodium stannate solution at a flow rate of 3 L / h, and the sodium aluminate solution at a flow rate of 2 L / h are fed into the reactor containing the bottom liquid at the same flow rate. Liquid alkali and ammonia are added simultaneously, and the flow rate is automatically adjusted by the precipitant flow control system to control the pH of the reaction system at 10.8. Stirring is started at 500 rpm to carry out the first coprecipitation reaction. When the particle size D50 of the product particles is d1, the feeding of the nickel-cobalt-manganese mixed metal salt solution, sodium stannate solution, and sodium aluminate solution is stopped to obtain crystal nuclei. During the first coprecipitation reaction, the reaction atmosphere is a low-oxygen nitrogen mixed atmosphere, which includes oxygen and nitrogen. The oxygen concentration is controlled by an oxygen content tester located above the reactor and is controlled at 1.5 vol%; d1 is 8.5 μm.
[0096] (2) While maintaining the flow of liquid alkali and ammonia, an ammonium tungstate solution with a flow rate of 2 L / h is introduced into the bottom liquid, and the flow rate is automatically adjusted by the precipitant flow control system to control the pH of the reaction system to 10.8 and the reaction temperature to 40°C. At the same time, the stirring is turned on at a speed of 500 rpm to carry out the second coprecipitation reaction. When the particle size D50 of the product particles is d2, the reaction ends. Then, the product is centrifuged and washed, and then placed in a hot air circulating drying oven and dried at a temperature of 130°C. After sieving, the ternary cathode material precursor is obtained. In the process of the first coprecipitation reaction, the reaction atmosphere is a low-oxygen nitrogen mixed atmosphere. The low-oxygen inert mixed atmosphere includes oxygen and nitrogen. The oxygen concentration is controlled by an oxygen content tester located above the reaction vessel and is controlled to be 1.5 vol%. The d2 is 9.5 μm.
[0097] This embodiment also provides a ternary cathode material, which is prepared by sintering the ternary cathode material precursor and lithium carbonate as described above. The specific steps include:
[0098] (i) The ground and sieved lithium carbonate is mixed with the ternary precursor at a molar ratio of lithium ions to total transition metal ions of 1.2:0.8 to obtain a mixture.
[0099] (ii) The mixture is placed in a roller kiln, heated to 50°C and held for 8 hours, then heated to 1000°C and held for 24 hours, and then slowly cooled to room temperature of 25°C to obtain the ternary cathode material.
[0100] Example 4
[0101] The difference between this embodiment and Embodiment 1 is that the surface of the ternary cathode material is coated with a 30nm thick metal oxide-phosphate co-coating layer, and the preparation steps include:
[0102] Alumina and lanthanum phosphate were ground and mixed in a ball mill at a mass ratio of 1:1.2 to obtain abrasive material.
[0103] The ternary cathode material and the abrasive were ground and mixed in a ball mill, and then placed in a roller kiln for heat treatment at 1000°C in an air atmosphere for 10 hours to obtain a ternary cathode material with a metal oxide-phosphate co-coating layer on the surface.
[0104] The remaining preparation methods and parameters are consistent with those in Example 1.
[0105] Example 5
[0106] The difference between this embodiment and Embodiment 1 is that, based on the amount of the doped nickel-cobalt-manganese hydroxide, the doping amount of element M is 500 ppm.
[0107] The remaining preparation methods and parameters are consistent with those in Example 1.
[0108] Example 6
[0109] The difference between this embodiment and Embodiment 1 is that, based on the amount of the doped nickel-cobalt-manganese hydroxide, the doping amount of element M is 2500 ppm.
[0110] The remaining preparation methods and parameters are consistent with those in Example 1.
[0111] Example 7
[0112] The difference between this embodiment and Embodiment 1 is that the molar ratio of Sn to Al is 1:1.
[0113] The remaining preparation methods and parameters are consistent with those in Example 1.
[0114] Example 8
[0115] The difference between this embodiment and Embodiment 1 is that the molar ratio of Sn to Al is 3:1.
[0116] The remaining preparation methods and parameters are consistent with those in Example 1.
[0117] Example 9
[0118] The difference between this embodiment and Embodiment 1 is that the thickness of the tungsten-based coating layer is 0.2 μm.
[0119] The remaining preparation methods and parameters are consistent with those in Example 1.
[0120] Example 10
[0121] The difference between this embodiment and Embodiment 1 is that the thickness of the tungsten-based coating layer is 3 μm.
[0122] The remaining preparation methods and parameters are consistent with those in Example 1.
[0123] Example 11
[0124] The difference between this embodiment and embodiment 1 is that the low-oxygen inert mixed atmosphere described in steps (1) and (2) is replaced with a pure nitrogen atmosphere.
[0125] The remaining preparation methods and parameters are consistent with those in Example 1.
[0126] Example 12
[0127] The difference between this embodiment and Embodiment 4 is that the mass ratio of alumina to lanthanum phosphate is 1:1.8.
[0128] The remaining preparation methods and parameters are consistent with those in Example 4.
[0129] Example 13
[0130] The difference between this embodiment and Embodiment 4 is that the mass ratio of alumina to lanthanum phosphate is 1:0.5.
[0131] The remaining preparation methods and parameters are consistent with those in Example 4.
[0132] Comparative Example 1
[0133] The difference between this comparative example and Example 1 is that the M element is Sn element, and the doping amount is 1500ppm.
[0134] The remaining preparation methods and parameters are consistent with those in Example 1.
[0135] Comparative Example 2
[0136] The difference between this comparative example and Example 1 is that the M element is Al element, and the doping amount is 1500ppm.
[0137] The remaining preparation methods and parameters are consistent with those in Example 1.
[0138] Comparative Example 3
[0139] The difference between this comparative example and Example 1 is that no tungsten-based coating layer is provided, i.e., step (2) is not performed, and d1 is 8.5 μm.
[0140] The remaining preparation methods and parameters are consistent with those in Example 1.
[0141] Performance testing
[0142] The ternary cathode material, polyvinylidene fluoride, and acetylene black provided in the above embodiments and comparative examples were mixed in a mass ratio of 8:1:1 to form a slurry, which was then coated on aluminum foil to obtain a cathode sheet; a lithium sheet was used as the anode sheet; lithium hexafluorophosphate was used as the solute in the electrolyte, and the solvent was a combination of ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1; a polypropylene separator was used; and a CR2032 coin cell was assembled.
[0143] The CR2032 coin cell was subjected to its first charge-discharge performance test: under constant current conditions, the first charge-discharge cycle was performed at a rate of 0.1C, the first discharge specific capacity was measured and the first coulombic efficiency was calculated.
[0144] Cyclic performance testing was performed on the CR2032 coin cell: Under constant current conditions, charge and discharge cycles were performed at a rate of 1C within a voltage range of 2.8V to 4.3V for 100 cycles. The discharge capacity of the 100th cycle was recorded, and the capacity retention rate relative to the first discharge capacity was calculated.
[0145] The test results are shown in Table 1.
[0146] Table 1
[0147]
[0148] analyze:
[0149] As shown in Table 1, this invention designs a core-shell structured ternary cathode material precursor, wherein the core is a doped nickel-cobalt-manganese hydroxide doped with element M. Sn and Al in element M work synergistically to suppress lithium-nickel mixing: Sn, due to its ionic radius being close to that of Ni, can preferentially occupy lattice defect sites on nickel sites, reducing lattice dislocations during lithium-ion insertion / extraction. Al, through bulk doping, strengthens the layered structure framework, reducing the anisotropy of lattice expansion and contraction during cycling and improving structural stability. The outer shell is a tungsten-based coating layer, which can construct a dense and highly ionicly conductive interfacial barrier. This not only isolates corrosive components in the electrolyte from direct contact with the core, suppresses side reactions between surface residual alkali and the electrolyte, and reduces interfacial impedance, but also allows the high-valence ions of tungsten to regulate the surface electronic state density, promoting rapid lithium-ion transport at the interface while preventing the dissolution of transition metals in the core. The ternary cathode material prepared based on this exhibits excellent cycling performance, and voltage decay is effectively suppressed.
[0150] A comparison of Examples 1 and 5-6 shows that if the doping amount of element M in the doped nickel-cobalt-manganese hydroxide is too small, its effect on stabilizing the material structure, improving conductivity, and suppressing side reactions is limited. This may lead to insufficient structural stability of the material, making it more prone to irreversible phase transitions during cycling, while the improvement in conductivity is not significant, ultimately resulting in a lower initial coulombic efficiency and a decrease in cycle capacity retention. If the doping amount of element M in the doped nickel-cobalt-manganese hydroxide is too large, it may destroy the crystal structure of the main material, introducing too many lattice defects or impurity phases. This will not only occupy the lithium-ion diffusion channels and reduce the lithium-ion diffusion rate, but may also affect the overall compactness and continuity of the electronic conductivity network of the material due to the segregation of excessive dopant elements at grain boundaries. As a result, the initial discharge specific capacity of the material may decrease, and the rate performance and long-term cycle stability will deteriorate.
[0151] As can be seen from the comparison between Example 1 and Examples 7-8, if the molar ratio of Sn to Al is too small, the material particles may exhibit poor adaptability to volume changes during charging and discharging, making them prone to microcracks, thereby damaging the cycle life and structural integrity of the material. If the molar ratio of Sn to Al is too large, it may promote the formation of brittle intermetallic compounds or lead to abnormal grain growth in some systems. This will also deteriorate the mechanical properties of the material and may negatively affect the electrochemical activity due to the formation of an undesirable second phase, resulting in the deterioration of the overall electrochemical performance (such as capacity and efficiency) of the electrode material.
[0152] As can be seen from the comparison between Example 1 and Examples 9-10, if the thickness of the tungsten-based coating is too small, it cannot effectively improve the cycle stability and interface stability of the material; if the thickness of the tungsten-based coating is too large, it will lead to a decrease in the rate performance of the material, and the excessively thick inactive coating may also reduce the overall energy density (specific capacity) of the material.
[0153] As can be seen from the comparison between Example 1 and Example 11, if the low-oxygen inert mixed atmosphere described in steps (1) and (2) is replaced with a pure nitrogen atmosphere, the crystal structure defects of the cathode material will increase and the lattice stability will deteriorate. The direct consequence is that the initial coulombic efficiency of the material will decrease (the number of side reactions will increase), and the structural decay will accelerate during cycling, and the capacity retention rate will decrease significantly.
[0154] A comparison of Examples 4 and 12-13 shows that if the mass ratio of alumina to lanthanum phosphate is too small, the interfacial bonding force weakens, the integrity of the coating layer is damaged, ion transport channels are blocked, and kinetic performance decreases; the effective coating components are diluted, resulting in insufficient structural stabilization. If the mass ratio of alumina to lanthanum phosphate is too large, the coating layer becomes too dense and rigid, making lithium-ion conduction difficult; brittleness increases, making it prone to cracking during cycling; the synergistic modification effect is lost, and the beneficial effects of La cannot be exerted.
[0155] As can be seen from the comparison between Example 1 and Comparative Examples 1-2, if the M element is a single Sn element, the material will have shortcomings in terms of structural stability, cycle life or rate performance under high voltage; if the M element is a single Al element, it will exhibit higher structural stability, but the first discharge specific capacity and electronic conductivity may not be as good as the material with multiple elements co-doped.
[0156] As can be seen from the comparison between Example 1 and Comparative Example 3, without the tungsten-based coating layer, the material will be directly exposed to the electrolyte, leading to a sharp increase in interfacial side reactions, severe dissolution of transition metals, and rapid deterioration of the surface structure. This will directly result in a significant decrease in the material's initial coulombic efficiency, a sharp decline in cycle performance (capacity retention), and potentially worsening rate performance due to increased interfacial impedance.
[0157] It should be noted that the technical solution of the present invention is illustrated through the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.
Claims
1. A ternary cathode material precursor, characterized in that, The ternary positive electrode material precursor comprises an inner core and a tungsten-based coating layer coated on the surface of the inner core; The inner core is a doped nickel-cobalt-manganese hydroxide, and the doped nickel-cobalt-manganese hydroxide is doped with an M element, and the M element comprises Sn and Al. 2.The ternary cathode material precursor of claim 1, wherein, The particle size D50 of the inner core is 8-10 μm; Preferably, the doping amount of the M element is 1000-2000 ppm based on the amount of substance of the doped nickel-cobalt-manganese hydroxide; Preferably, the molar ratio of Sn to Al is (1.5-2.5):
1. 3.The ternary cathode material precursor of claim 1 or 2, characterized in that, The thickness of the tungsten-based coating layer is 0.5-2.5 μm; Preferably, the tungsten-based coating layer comprises a tungsten hydroxide.
4. A method for preparing the ternary cathode material precursor according to any one of claims 1-3, characterized in that, The preparation method comprises the following steps: The nickel-cobalt-manganese mixed metal salt solution, the precipitating agent, the complexing agent, and the M salt solution are passed into the bottom liquid in parallel to perform a first co-precipitation reaction, and when the particle size D50 of the product particles is d1, the feeding of the nickel-cobalt-manganese mixed metal salt solution and the M salt solution is stopped to obtain a crystal nucleus; wherein the M salt solution comprises a Sn salt solution and an Al salt solution; While the precipitating agent and the complexing agent are being passed in, the W salt solution is passed into the bottom liquid to perform a second co-precipitation reaction, and when the particle size D50 of the product particles is d2, the reaction is ended to obtain the ternary positive electrode material precursor.
5. The preparation method according to claim 4, characterized in that, During the first co-precipitation reaction, the pH of the reaction system is 9.5-11.5, and is preferably 10.2-10.8; Preferably, during the first co-precipitation reaction, the reaction temperature is 40-65°C; Preferably, d1 is 8-10 μm; Preferably, the Sn salt solution comprises a sodium stannate solution; Preferably, the Al salt solution comprises a sodium metaaluminate solution.
6. The production method according to claim 4 or 5, characterized by, The W salt solution comprises an ammonium tungstate solution; Preferably, during the second co-precipitation reaction, the pH of the reaction system is 9.5-11.5; Preferably, during the second co-precipitation reaction, the reaction temperature is 40-65°C; Preferably, d2 is 8.5-10.5 μm.
7. The method of any one of claims 4-6, wherein the method further comprises, During the first co-precipitation reaction and the second co-precipitation reaction, the reaction atmosphere is a low-oxygen inert mixed gas atmosphere; Preferably, in the low-oxygen inert mixed gas atmosphere, the concentration of oxygen is 0.5-1.5 vol%; Preferably, the pH of the bottom liquid is 10.5-11.
8. The method of any one of claims 4-7, wherein, The preparation method comprises the following steps: (1) nickel-cobalt-manganese mixed metal salt solution, precipitant, complexing agent and M salt solution are passed into the reactor where the bottom liquid is located in a concurrent manner, and the flow rate is automatically adjusted by a precipitant flow control system, so that the pH of the reaction system is controlled to be 9.5-11.5, the reaction temperature is 40-65℃, and stirring is started at the same time, to carry out the first co-precipitation reaction, and when the particle size D50 of the product particles is d1, the feeding of the nickel-cobalt-manganese mixed metal salt solution and the M salt solution is stopped, to obtain crystal nuclei; wherein the M salt solution includes Sn salt solution and Al salt solution; the precipitant includes liquid alkali, and the complexing agent includes ammonia water; during the first co-precipitation reaction, the reaction atmosphere is a low-oxygen inert mixed atmosphere, which includes oxygen and inert gas, wherein the concentration of oxygen is controlled to be 0.5-1.5vol% by an oxygen content tester located above the reactor; the stirring speed is 200-500rpm; and d1 is 8-10μm; (2) while the precipitant and the complexing agent are being passed in, W salt solution is passed into the bottom liquid, and the flow rate is automatically adjusted by a precipitant flow control system, so that the pH of the reaction system is controlled to be 9.5-11.5, the reaction temperature is 40-65℃, and stirring is started at the same time, to carry out the second co-precipitation reaction, and when the particle size D50 of the product particles is d2, the reaction is ended, and then washing and drying are carried out, to obtain a ternary positive electrode material precursor; wherein the W salt solution includes ammonium tungstate solution; during the first co-precipitation reaction, the reaction atmosphere is a low-oxygen inert mixed atmosphere, which includes oxygen and inert gas, wherein the concentration of oxygen is controlled to be 0.5-1.5vol% by an oxygen content tester located above the reactor; and d2 is 8.5-10.5μm.
9. A ternary cathode material, characterized in that, The ternary positive electrode material is prepared by mixing and sintering the ternary positive electrode material precursor and a lithium source according to any one of claims 1-3; Preferably, the outer surface of the ternary positive electrode material is further coated with a metal oxide-phosphate co-coating layer; Preferably, the metal oxide includes aluminum oxide; Preferably, the phosphate includes lanthanum phosphate; Preferably, in the metal oxide-phosphate co-coating layer, the mass ratio of metal oxide to phosphate is 1:(0.8-1.5).
10. A lithium-ion battery, characterized by, The positive electrode sheet of the lithium ion battery includes the ternary positive electrode material according to claim 9, or a ternary positive electrode material prepared by mixing and sintering the ternary positive electrode material precursor and a lithium source according to any one of claims 1-3.