Ternary material precursor, preparation method thereof, ternary positive electrode material and battery

Abstract

The invention provides a ternary material precursor and a preparation method thereof, a ternary positive electrode material and a battery. The ternary material precursor comprises a core, a middle layer and an outer coating layer, wherein the middle layer is coated outside the core; the outer coating layer is coated outside the middle layer; the core, the middle layer and the outer coating layer all comprise an Ni element, a Co element and an Mn element; the content of the Ni element in the core is greater than the content of the Ni element in the middle layer and the outer coating layer, and the core is doped with the Mg element. According to the ternary material precursor, the high-nickel core is adopted, and the Mg element is doped, so that the ternary positive electrode material prepared from the ternary material precursor has relatively high capacity, and the ternary positive electrode material also has relatively high structural stability and cycling stability, and therefore, a battery containing the ternary positive electrode material has high capacity and excellent cycling stability at the same time.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and relates to a ternary material precursor, and more particularly to a ternary material precursor and its preparation method, a ternary cathode material and a battery. Background Technology

[0002] Lithium-ion batteries are a new generation of high-energy, renewable, and green energy. They possess advantages such as high energy density, long cycle life, high safety, and environmental friendliness, and are now widely used in electric vehicles, mobile phones, and large-scale energy storage. However, with the rapid development of electric vehicles, the performance requirements for lithium batteries are constantly increasing; therefore, developing lithium-ion batteries with superior performance is urgently needed to improve the performance of electric vehicles.

[0003] The positive electrode, negative electrode, separator, and electrolyte are the four core materials of lithium-ion batteries, and their performance directly determines the overall performance of the battery. The excellent performance of lithium-ion batteries, such as cycle stability, capacity, and voltage, mainly depends on the preparation of the positive electrode material. Conventional positive electrode materials have low capacity, which limits the improvement of the overall capacity of lithium-ion batteries.

[0004] In the existing technology, nickel-cobalt-manganese ternary cathode materials are widely used in lithium-ion batteries due to their balanced comprehensive performance. However, despite the significant performance advantages of nickel-cobalt-manganese ternary cathode materials, they still face some challenges in practical applications, such as cycle stability, thermal stability, and structural stability at high voltage, which still cannot meet the requirements of practical applications.

[0005] Due to the shortcomings of existing nickel-cobalt-manganese ternary cathode materials, current technologies often employ single-element doping or coating to modify the nickel-cobalt-manganese ternary cathode precursor, thereby improving the performance of the nickel-cobalt-manganese ternary cathode material. However, while single-element doping modification of the nickel-cobalt-manganese ternary cathode precursor can optimize the bulk structure to some extent, it cannot solve the problem of poor surface stability, easily leading to phenomena such as transition metal dissolution and electrolyte corrosion. When modifying the nickel-cobalt-manganese ternary cathode precursor with coating, the coating layer's insufficient HF resistance during cycling makes it prone to reacting with HF in the electrolyte, causing the coating layer to fail and forming new exposed surfaces, making it difficult to effectively prevent interfacial side reactions between the electrolyte and the cathode material.

[0006] For example, CN119370916A discloses a precursor with a porous structure and a coating layer, its preparation method, and its application. The precursor includes a core and at least one coating layer. The core is a ternary precursor with a porous structure, and the outermost layer of the coating layer is an aluminum-doped ternary precursor.

[0007] For example, CN116002776A discloses a ternary precursor and its preparation method, as well as a cathode material. The ternary precursor is nickel-cobalt-manganese hydroxide. The ternary precursor includes a core layer, a connecting ring layer, and a shell layer from the inside out. The connecting ring layer has a dense structure. The core layer includes a central layer and an intermediate layer from the inside out. The average thickness of the central layer, the intermediate layer, and the shell layer is greater than the average thickness of the connecting ring layer.

[0008] In summary, the existing modified ternary material precursors all have certain drawbacks, including insufficient capacity and cycle performance of the ternary cathode materials prepared from them. Therefore, it is crucial to develop and design a novel ternary material precursor and its preparation method, as well as ternary cathode materials and batteries. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a ternary material precursor and its preparation method, a ternary cathode material, and a battery. The present invention employs a high-nickel core, combined with Mg doping, which enables the ternary cathode material prepared from the ternary material precursor to have high capacity, as well as high structural stability and cycle stability. Thus, the battery containing the ternary cathode material simultaneously possesses high capacity and excellent cycle stability.

[0010] To achieve this objective, the present invention adopts the following technical solution:

[0011] In a first aspect, the present invention provides a ternary material precursor, the ternary material precursor comprising a core, an intermediate layer covering the core, and an outer covering layer covering the intermediate layer.

[0012] The core, intermediate layer and outer cladding layer all include Ni, Co and Mn elements;

[0013] The Ni content in the core is greater than the Ni content in the intermediate layer and the outer coating layer, and the core is doped with Mg.

[0014] The ternary precursor provided by this invention has a high nickel content in its core (the molar fraction of Ni in the core is greater than the molar fraction of Ni in the intermediate layer and the outer coating layer), which can meet the high capacity requirements of ternary cathode materials. However, a high nickel content will lead to a decrease in the thermal stability and structural stability of the material. Therefore, this invention uses Mg to dope the core. On the one hand, the doping of the core with Mg suppresses the mixing of Ni cations in the core, improves the structural stability of the ternary precursor, and thus improves the structural stability of the ternary cathode material. On the other hand, the introduction of Mg also optimizes the lithium-ion diffusion channel, alleviates the volume expansion of the ternary cathode material during charging and discharging, and thus improves the cycle stability of the ternary cathode material.

[0015] In summary, the present invention employs a high-nickel core, combined with Mg doping, which enables the ternary cathode material prepared from the ternary material precursor to have high capacity, as well as high structural stability and cycle stability. Thus, the battery containing the ternary cathode material simultaneously possesses high capacity and excellent cycle stability.

[0016] Preferably, in the core, the total molar amount of Ni, Co and Mn elements is in a molar ratio of 100:(0.1~0.3) to Mg elements. For example, it can be 100:0.1, 100:0.12, 100:0.14, 100:0.16, 100:0.18, 100:0.2, 100:0.22, 100:0.24, 100:0.26, 100:0.28 or 100:0.3, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0017] Preferably, the molar ratio of Ni, Co and Mn in the core is (90~98):(1~5):(1~5).

[0018] In this invention, the molar ratio of Ni to Co in the core is (90~98):(1~5), for example, it can be 90:1, 91:2, 92:2, 93:3, 94:3, 95:4, 96:4, 97:5 or 98:5, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0019] In this invention, the molar ratio of Ni to Mn in the core is (90~98):(1~5), for example, it can be 90:1, 91:2, 92:2, 93:3, 94:3, 95:4, 96:4, 97:5 or 98:5, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0020] Preferably, the ratio of the D50 particle size of the core to the sum of the thicknesses of the intermediate layer and the outer coating layer is (8.5~9.8):(2.1~3.5), for example, it can be 8.5:2.1, 8.6:2.3, 8.7:2.5, 8.8:2.7, 8.9:2.9, 9.0:3.1, 9.1:3.3, 9.2:3.5, 9.3:2.1, 9.4:2.3, 9.5:2.5, 9.6:2.7, 9.7:2.9 or 9.8:3.1, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0021] In this invention, the ratio of the core D50 particle size to the sum of the thicknesses of the intermediate layer and the outer coating layer is: core D50 particle size / (thickness of the intermediate layer + thickness of the outer coating layer).

[0022] Preferably, the D50 particle size of the core is 8.5μm to 9.8μm, for example, it can be 8.5μm, 8.6μm, 8.7μm, 8.8μm, 8.9μm, 9.0μm, 9.1μm, 9.2μm, 9.3μm, 9.4μm, 9.5μm, 9.6μm, 9.7μm or 9.8μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0023] Preferably, the thickness of the intermediate layer is 0.6μm to 1μm, for example, it can be 0.6μm, 0.65μm, 0.7μm, 0.75μm, 0.8μm, 0.85μm, 0.9μm, 0.95μm or 1μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0024] Preferably, the thickness of the outer coating layer is 1.5μm to 2.5μm, for example, it can be 1.5μm, 1.6μm, 1.7μm, 1.8μm, 1.9μm, 2.0μm, 2.1μm, 2.2μm, 2.3μm, 2.4μm or 2.5μm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0025] Preferably, the D50 particle size of the ternary material precursor is 10.6 μm to 13.3 μm, for example, it can be 10.6 μm, 10.8 μm, 11.0 μm, 11.2 μm, 11.4 μm, 11.6 μm, 11.8 μm, 12.0 μm, 12.2 μm, 12.4 μm, 12.6 μm, 12.8 μm, 13.0 μm or 13.3 μm, but it is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0026] Preferably, the Ni content in the intermediate layer is greater than the Ni content in the outer coating layer.

[0027] In this invention, the Ni content in the intermediate layer is higher than that in the outer coating layer. The intermediate layer allows the Ni content in the ternary material precursor to decrease gradually from the core to the outermost layer. This gradient structure helps to alleviate the interfacial stress caused by the difference in composition, thereby effectively suppressing the structural cracking problem that occurs in the ternary cathode material during cycling.

[0028] In this invention, the Ni content in the outer coating layer is higher than that in the intermediate layer, the nickel content in the outer coating layer is relatively low, and the molar fraction of Mn is relatively high. The outer coating layer with a higher molar fraction of Mn has higher material thermal stability and can serve as a protective layer for the ternary material precursor, thereby improving the thermal stability of the ternary cathode material prepared from the ternary material precursor. It also improves the surface stability of the ternary cathode material prepared from the ternary material precursor and reduces the interfacial side reactions between the ternary cathode material and the electrolyte.

[0029] Preferably, the molar ratio of Ni, Co and Mn in the intermediate layer is (70~80):(10~20):(10~20).

[0030] In this invention, the molar ratio of Ni to Co in the intermediate layer is (70~80):(10~20), for example, it can be 70:10, 72:12, 74:14, 75:15, 76:16, 78:18 or 80:20, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] In this invention, the molar ratio of Ni to Mn in the intermediate layer is (70~80):(10~20), for example, it can be 70:10, 72:12, 74:14, 75:15, 76:16, 78:18 or 80:20, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0032] Preferably, the molar ratio of Ni, Co and Mn in the outer coating layer is (50~60):(10~20):(20~40).

[0033] In this invention, the molar ratio of Ni to Co in the outer coating layer is (50~60):(10~20), for example, it can be 50:10, 52:12, 54:14, 55:15, 56:16, 58:18 or 60:20, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] In this invention, the molar ratio of Ni to Mn in the outer coating layer is (50~60):(20~40), for example, it can be 50:20, 52:24, 54:28, 55:30, 56:32, 58:36 or 60:40, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0035] In a second aspect, the present invention provides a method for preparing the ternary material precursor described in the first aspect, the method comprising:

[0036] (1) The mixed salt solution, along with the precipitant solution and the complexing agent solution, are simultaneously added to the base liquid to carry out the first co-precipitation, thereby obtaining a first solution with the first precipitate;

[0037] (2) The mixed salt solution, precipitant solution and complexing agent solution are simultaneously added to the first solution obtained in step (1) to carry out the second coprecipitation and obtain the second solution with the second precipitate;

[0038] (3) The mixed salt solution, precipitant solution and complexing agent solution are simultaneously added to the second solution obtained in step (2) to carry out the third co-precipitation and obtain the ternary material precursor;

[0039] The mixed salt solutions described in steps (1), (2), and (3) all contain Ni ions, Co ions, and Mn ions, and the mixed salt solution described in step (1) also contains Mg ions;

[0040] In step (1), the molar amount of Ni ions in the first coprecipitation reaction is greater than the molar amount of Ni ions in the second coprecipitation reaction and the third coprecipitation reaction in step (3).

[0041] In this invention, wet doping introduces dopant elements into the co-precipitation process, which enables the uniform distribution of dopant elements.

[0042] In this invention, when using the coprecipitation process, the formation of the multi-shell structure can be precisely controlled by adjusting the coprecipitation reaction conditions.

[0043] Preferably, in the mixed salt solution described in step (1), the ratio of the total molar amount of Ni ions, Co ions and Mn ions to the molar amount of Mg ions is 100:(0.1~0.3), for example, it can be 100:0.1, 100:0.12, 100:0.14, 100:0.16, 100:0.18, 100:0.2, 100:0.22, 100:0.24, 100:0.26, 100:0.28 or 100:0.3, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0044] Preferably, in the mixed salt solution described in step (1), the molar ratio of Ni ions, Co ions and Mn ions is (90~98):(1~5):(1~5).

[0045] In this invention, the molar ratio of Ni ions to Co ions in the mixed salt solution described in step (1) is (90~98):(1~5), for example, it can be 90:1, 91:2, 92:2, 93:3, 94:3, 95:4, 96:4, 97:5 or 98:5, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0046] In this invention, the molar ratio of Ni ions to Mn ions in the mixed salt solution described in step (1) is (90~98):(1~5), for example, it can be 90:1, 91:2, 92:2, 93:3, 94:3, 95:4, 96:4, 97:5 or 98:5, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] Preferably, the total concentration of metal ions in the mixed salt solution in step (1) is 1.0 mol / L to 2.5 mol / L, for example, it can be 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2.0 mol / L, 2.1 mol / L, 2.2 mol / L, 2.3 mol / L, 2.4 mol / L or 2.5 mol / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0048] Preferably, in the mixed salt solution described in step (1), the anions include sulfate ions and / or chloride ions.

[0049] Preferably, in the mixed salt solution described in step (2), the molar ratio of Ni ions, Co ions and Mn ions is (70~80):(10~20):(10~20).

[0050] In this invention, the molar ratio of Ni ions to Co ions in the mixed salt solution described in step (2) is (70~80):(10~20), for example, it can be 70:10, 72:12, 74:14, 75:15, 76:16, 78:18 or 80:20, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0051] In this invention, the molar ratio of Ni ions to Mn ions in the mixed salt solution described in step (2) is (70~80):(10~20), for example, it can be 70:10, 72:12, 74:14, 75:15, 76:16, 78:18 or 80:20, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0052] Preferably, the total concentration of metal ions in the mixed salt solution in step (2) is 1.0 mol / L to 2.5 mol / L, for example, it can be 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2.0 mol / L, 2.1 mol / L, 2.2 mol / L, 2.3 mol / L, 2.4 mol / L or 2.5 mol / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0053] Preferably, in the mixed salt solution described in step (2), the anions include sulfate ions and / or chloride ions.

[0054] Preferably, in the mixed salt solution described in step (3), the molar ratio of Ni ions, Co ions and Mn ions is (50~60):(10~20):(20~40).

[0055] In this invention, the molar ratio of Ni ions to Co ions in the mixed salt solution described in step (3) is (50~60):(10~20), for example, it can be 50:10, 52:12, 54:14, 55:15, 56:16, 58:18 or 60:20, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0056] In this invention, the molar ratio of Ni ions to Mn ions in the mixed salt solution described in step (3) is (50~60):(20~40), for example, it can be 50:20, 52:24, 54:28, 55:30, 56:32, 58:36 or 60:40, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0057] Preferably, the total concentration of metal ions in the mixed salt solution in step (3) is 1.0 mol / L to 2.5 mol / L, for example, it can be 1.0 mol / L, 1.1 mol / L, 1.2 mol / L, 1.3 mol / L, 1.4 mol / L, 1.5 mol / L, 1.6 mol / L, 1.7 mol / L, 1.8 mol / L, 1.9 mol / L, 2.0 mol / L, 2.1 mol / L, 2.2 mol / L, 2.3 mol / L, 2.4 mol / L or 2.5 mol / L, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0058] Preferably, in the mixed salt solution described in step (3), the anions include sulfate ions and / or chloride ions.

[0059] Preferably, in steps (1), (2) and (3), the feed flow rate of the mixed salt solution is controlled independently to be 10L / h to 80L / h.

[0060] Preferably, the pH of the base solution in step (1) is 11~12, the temperature is 40℃~80℃, and the concentration of the complexing agent in the base solution is 4g / L~12g / L.

[0061] In this invention, the pH of the base solution in step (1) is 11~12, for example, it can be 11, 11.2, 11.3, 11.4, 11.5, 11.6, 11.7, 11.8, 11.9 or 12.0, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0062] In this invention, the bottom liquid temperature in step (1) is 40℃~80℃, for example, it can be 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃ or 80℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0063] In this invention, the concentration of the complexing agent in the base liquid in step (1) is 4 g / L to 12 g / L, for example, it can be 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, 10 g / L, 11 g / L or 12 g / L, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0064] Preferably, the mass concentration of the precipitant in the precipitant solution described in steps (1), (2) and (3) is 20wt% to 40wt%, for example, it can be 20wt%, 22wt%, 24wt%, 26wt%, 28wt%, 30wt%, 32wt%, 34wt%, 36wt%, 38wt% or 40wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0065] Preferably, the precipitant solutions described in steps (1), (2), and (3) each independently include any one or at least two of sodium hydroxide solution, sodium carbonate solution, or potassium hydroxide solution. Typical but non-limiting combinations include combinations of sodium hydroxide solution and sodium carbonate solution, combinations of sodium carbonate solution and potassium hydroxide solution, combinations of sodium hydroxide solution and potassium hydroxide solution, or combinations of sodium hydroxide solution, sodium carbonate solution, and potassium hydroxide solution.

[0066] Preferably, the solvent in the precipitant solution in steps (1), (2) and (3) includes water.

[0067] Preferably, in steps (1), (2) and (3), the feed flow rate of the precipitant solution is controlled to be 2L / h to 20L / h, for example, it can be 2L / h, 4L / h, 6L / h, 8L / h, 10L / h, 12L / h, 14L / h, 16L / h, 18L / h or 20L / h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0068] Preferably, the mass concentration of the complexing agent in the complexing agent solution described in steps (1), (2) and (3) is 10wt% to 30wt%, for example, it can be 10wt%, 12wt%, 14wt%, 16wt%, 18wt%, 20wt%, 22wt%, 24wt%, 26wt%, 28wt% or 30wt%, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0069] Preferably, the complexing agent solutions in steps (1), (2), and (3) each independently comprise any one or a combination of at least two of ammonia, ethylenediaminetetraacetic acid (EDTA) solution, citric acid solution, or oxalic acid solution. Typical but non-limiting combinations include a combination of ammonia and EDTA solution, a combination of EDTA and citric acid solution, a combination of citric acid solution and oxalic acid solution, a combination of ammonia and citric acid solution, or a combination of ammonia, EDTA solution, and oxalic acid solution.

[0070] Preferably, the solvent in the complexing agent solution described in steps (1), (2) and (3) includes water.

[0071] Preferably, in steps (1), (2) and (3), the feed flow rate of the complexing agent solution is controlled to be 2L / h to 10L / h, for example, it can be 2L / h, 3L / h, 4L / h, 5L / h, 6L / h, 7L / h, 8L / h, 9L / h or 10L / h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0072] Preferably, in step (1), during the first coprecipitation, the pH is controlled to be 10-11, the complexing agent concentration is 4g / L-10g / L, and the temperature is 40℃-80℃.

[0073] In this invention, during the first coprecipitation in step (1), the pH is controlled to be 10~11, for example, it can be 10.0, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9 or 11.0, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0074] In this invention, during the first coprecipitation in step (1), the concentration of the complexing agent is controlled to be 4 g / L to 10 g / L. For example, it can be 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L or 10 g / L, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0075] In this invention, during the first coprecipitation in step (1), the temperature is controlled to be 40℃~80℃, for example, it can be 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃ or 80℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0076] Preferably, in step (2), during the second coprecipitation, the pH is controlled to be 10-11, the complexing agent concentration is 4g / L-10g / L, and the temperature is 40℃-80℃.

[0077] In this invention, during the second coprecipitation in step (2), the pH is controlled to be 10~11, for example, it can be 10.0, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9 or 11.0, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0078] In this invention, during the second coprecipitation in step (2), the concentration of the complexing agent is controlled to be 4 g / L to 10 g / L. For example, it can be 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L or 10 g / L, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0079] In this invention, during the second coprecipitation in step (2), the temperature is controlled to be 40℃~80℃, for example, it can be 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃ or 80℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0080] Preferably, during the third coprecipitation in step (3), the pH is controlled at 10~11, the concentration of the complexing agent is 4g / L~10g / L, and the temperature is 40℃~80℃.

[0081] In this invention, during the third coprecipitation in step (3), the pH is controlled to be 10~11, for example, it can be 10.0, 10.1, 10.2, 10.3, 10.4, 10.5, 10.6, 10.7, 10.8, 10.9 or 11.0, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0082] In this invention, during the third coprecipitation in step (3), the concentration of the complexing agent is controlled to be 4 g / L to 10 g / L. For example, it can be 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L or 10 g / L, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0083] In this invention, during the third coprecipitation in step (3), the temperature is controlled at 40℃~80℃, for example, it can be 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃ or 80℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0084] Preferably, the first coprecipitation in step (1), the second coprecipitation in step (2), and the third coprecipitation in step (3) are all carried out in a protective atmosphere.

[0085] Preferably, after the third coprecipitation in step (3), the process further includes: sequential filtration, washing and drying.

[0086] As a preferred embodiment of the preparation method of the present invention, the preparation method includes:

[0087] (1) In a protective atmosphere, a mixed salt solution, a precipitant aqueous solution with a mass concentration of 20wt%~40wt% and a complexing agent aqueous solution with a mass concentration of 10wt%~30wt% are simultaneously added to a base solution with a pH of 11~12, a temperature of 40℃~80℃ and a complexing agent concentration of 4g / L~12g / L. The pH is controlled at 10~11, the complexing agent concentration is 4g / L~10g / L, and the temperature is 40℃~80℃ to carry out the first coprecipitation and obtain a first solution with a first precipitate.

[0088] In the mixed salt solution described in step (1), the total concentration of metal ions is 1.0 mol / L to 2.5 mol / L, the ratio of the total molar amount of Ni ions, Co ions and Mn ions to the molar amount of Mg ions is 100:(0.1~0.3), the molar ratio of Ni ions, Co ions and Mn ions is (90~98):(1~5):(1~5), and the anions include sulfate ions and / or chloride ions;

[0089] (2) In a protective atmosphere, a mixed salt solution, a precipitant aqueous solution with a mass concentration of 20wt%~40wt% and a complexing agent aqueous solution with a mass concentration of 10wt%~30wt% are simultaneously added to the first solution obtained in step (1). The pH is controlled at 10~11, the complexing agent concentration is 4g / L~10g / L, and the temperature is 40℃~80℃ to carry out a second coprecipitation and obtain a second solution with a second precipitate.

[0090] In the mixed salt solution described in step (2), the total concentration of metal ions is 1.0 mol / L to 2.5 mol / L, the molar ratio of Ni ions, Co ions and Mn ions is (70~80):(10~20):(10~20), and the anions include sulfate ions and / or chloride ions;

[0091] (3) In a protective atmosphere, a mixed salt solution, a precipitant aqueous solution with a mass concentration of 20wt%~40wt% and a complexing agent aqueous solution with a mass concentration of 10wt%~30wt% are simultaneously added to the second solution obtained in step (2). The pH is controlled at 10~11, the complexing agent concentration is 4g / L~10g / L, and the temperature is 40℃~80℃ for a third co-precipitation. Then, the solution is filtered, washed and dried in sequence to obtain the ternary material precursor.

[0092] In the mixed salt solution described in step (3), the total concentration of metal ions is 1.0 mol / L to 2.5 mol / L, the molar ratio of Ni ions, Co ions and Mn ions is (50~60):(10~20):(20~40), and the anions include sulfate ions and / or chloride ions;

[0093] In step (1), the molar amount of Ni ions in the first coprecipitation reaction is greater than the molar amount of Ni ions in the second coprecipitation reaction and the third coprecipitation reaction in step (3).

[0094] Thirdly, the present invention provides a ternary cathode material, which is prepared from the ternary material precursor described in the first aspect.

[0095] Preferably, the method for preparing the ternary cathode material includes:

[0096] The ternary material precursor is mixed with a lithium source and sintered in an oxygen-containing atmosphere to obtain the ternary cathode material.

[0097] Preferably, the lithium source includes lithium hydroxide and / or lithium carbonate.

[0098] Preferably, the oxygen-containing atmosphere includes an air atmosphere or an oxygen-containing atmosphere.

[0099] Preferably, the sintering temperature is 500℃~800℃ and the time is 6h~10h.

[0100] In this invention, the sintering temperature is 500℃~800℃, for example, it can be 500℃, 550℃, 600℃, 650℃, 700℃, 750℃ or 800℃, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0101] In this invention, the sintering time is 6h to 10h, for example, it can be 6h, 6.5h, 7h, 7.5h, 8h, 8.5h, 9h, 9.5h or 10h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0102] Fourthly, the present invention provides a battery comprising the ternary cathode material described in the third aspect.

[0103] 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.

[0104] Compared with the prior art, the present invention has the following beneficial effects:

[0105] The ternary precursor provided by this invention has a high nickel content in its core (the molar fraction of Ni in the core is greater than the molar fraction of Ni in the intermediate layer and the outer coating layer), which can meet the high capacity requirements of ternary cathode materials. However, a high nickel content will lead to a decrease in the thermal stability and structural stability of the material. Therefore, this invention uses Mg to dope the core. On the one hand, the doping of the core with Mg suppresses the mixing of Ni cations in the core, improves the structural stability of the ternary precursor, and thus improves the structural stability of the ternary cathode material. On the other hand, the introduction of Mg also optimizes the lithium-ion diffusion channel, alleviates the volume expansion of the ternary cathode material during charging and discharging, and thus improves the cycle stability of the ternary cathode material.

[0106] This invention employs a high-nickel core, combined with Mg doping, which enables the ternary cathode material prepared from the ternary material precursor to have high capacity, as well as high structural stability and cycle stability. This results in a battery containing ternary cathode material that simultaneously possesses high capacity and excellent cycle stability. Detailed Implementation

[0107] 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.

[0108] Example 1

[0109] This embodiment provides a ternary material precursor, which includes a core, an intermediate layer covering the core, and an outer coating layer covering the intermediate layer.

[0110] The core, intermediate layer and outer cladding layer all include Ni, Co and Mn elements;

[0111] In the core, the total molar amount of Ni, Co and Mn elements is in a molar ratio of 100:0.2 to Mg; the molar ratio of Ni, Co and Mn elements in the core is 96:2:2.

[0112] The molar ratio of Ni, Co and Mn elements in the intermediate layer is 70:10:20;

[0113] The molar ratio of Ni, Co and Mn elements in the outer coating layer is 50:20:30;

[0114] The ratio of the D50 particle size of the core to the sum of the thicknesses of the intermediate layer and the outer coating layer is 8.5:2.6. The D50 particle size of the core is 8.5 μm, the thickness of the intermediate layer is 0.6 μm, the thickness of the outer coating layer is 2 μm, and the D50 particle size of the ternary material precursor is 11.1 μm.

[0115] The preparation method of the ternary material precursor includes:

[0116] (1) In a nitrogen atmosphere, a mixed salt solution, a sodium hydroxide aqueous solution with a mass concentration of 30 wt% and an ammonia solution with a mass concentration of 20 wt% are simultaneously added to a bottom solution with a pH of 11.5, a temperature of 60°C and an ammonia concentration of 8 g / L. The pH is controlled at 10.8, the ammonia concentration is 7 g / L and the temperature is 60°C to carry out the first coprecipitation and obtain a first solution with a first precipitate.

[0117] In the mixed salt solution described in step (1), the total concentration of metal ions is 2.0 mol / L, the ratio of the total molar amount of Ni ions, Co ions and Mn ions to the molar amount of Mg ions is 100:0.2, the molar ratio of Ni ions, Co ions and Mn ions is 96:2:2, and the anion is sulfate ions;

[0118] (2) In a nitrogen atmosphere, a mixed salt solution, a sodium hydroxide aqueous solution with a mass concentration of 30 wt%, and ammonia solution with a mass concentration of 20 wt% are simultaneously added to the first solution obtained in step (1). The pH is controlled at 10.5, the ammonia concentration is 6 g / L, and the temperature is 60 °C to carry out a second coprecipitation and obtain a second solution with a second precipitate.

[0119] In the mixed salt solution described in step (2), the total concentration of metal ions is 2.0 mol / L, the molar ratio of Ni ions, Co ions and Mn ions is 70:10:20, and the anion is sulfate ions;

[0120] (3) In a nitrogen atmosphere, a mixed salt solution, a sodium hydroxide aqueous solution with a mass concentration of 30 wt%, and ammonia solution with a mass concentration of 20 wt% are simultaneously added to the second solution obtained in step (2). The pH is controlled at 10.2, the ammonia concentration is 6 g / L, and the temperature is 60℃. A third co-precipitation is carried out, followed by filtration, washing, and drying to obtain the ternary material precursor.

[0121] In the mixed salt solution described in step (3), the total concentration of metal ions is 2.0 mol / L, the molar ratio of Ni ions, Co ions and Mn ions is 50:20:30, and the anion is sulfate ions.

[0122] Example 2

[0123] This embodiment provides a ternary material precursor, which includes a core, an intermediate layer covering the core, and an outer coating layer covering the intermediate layer.

[0124] The core, intermediate layer and outer cladding layer all include Ni, Co and Mn elements;

[0125] In the core, the total molar amount of Ni, Co and Mn elements is in a molar ratio of 100:0.2 to that of Mg; the molar ratio of Ni, Co and Mn elements in the core is 92:4:4.

[0126] The molar ratio of Ni, Co and Mn elements in the intermediate layer is 80:10:10;

[0127] The molar ratio of Ni, Co and Mn elements in the outer coating layer is 60:20:20;

[0128] The ratio of the D50 particle size of the core to the sum of the thicknesses of the intermediate layer and the outer coating layer is 9.8:3.2. The D50 particle size of the core is 9.8 μm, the thickness of the intermediate layer is 1 μm, the thickness of the outer coating layer is 2.2 μm, and the D50 particle size of the ternary material precursor is 13 μm.

[0129] The preparation method of the ternary material precursor includes:

[0130] (1) In an argon atmosphere, a mixed salt solution, a 30 wt% sodium hydroxide aqueous solution and a 20 wt% ethylenediaminetetraacetic acid solution are simultaneously added to a base solution with a pH of 11.5, a temperature of 60°C and an ethylenediaminetetraacetic acid concentration of 8 g / L. The pH is controlled at 10.8, the ethylenediaminetetraacetic acid concentration is 7 g / L, and the temperature is 60°C to carry out the first coprecipitation, thereby obtaining a first solution with a first precipitate.

[0131] In the mixed salt solution described in step (1), the total concentration of metal ions is 2.5 mol / L, the ratio of the total molar amount of Ni ions, Co ions and Mn ions to the molar amount of Mg ions is 100:0.2, the molar ratio of Ni ions, Co ions and Mn ions is 92:4:4, and the anion is chloride ions;

[0132] (2) In an argon atmosphere, a mixed salt solution, a sodium hydroxide aqueous solution with a mass concentration of 30 wt%, and an ethylenediaminetetraacetic acid solution with a mass concentration of 20 wt% are simultaneously added to the first solution obtained in step (1). The pH is controlled at 10.5, the concentration of ethylenediaminetetraacetic acid is 6 g / L, and the temperature is 60 °C to carry out a second coprecipitation and obtain a second solution with a second precipitate.

[0133] In the mixed salt solution described in step (2), the total concentration of metal ions is 2.5 mol / L, the molar ratio of Ni ions, Co ions and Mn ions is 80:10:10, and the anion is chloride ions;

[0134] (3) In an argon atmosphere, a mixed salt solution, a sodium hydroxide aqueous solution with a mass concentration of 30 wt%, and an ethylenediaminetetraacetic acid solution with a mass concentration of 20 wt% are simultaneously added to the second solution obtained in step (2). The pH is controlled at 10.2, the concentration of ethylenediaminetetraacetic acid is 5 g / L, and the temperature is 60 °C. A third coprecipitation is carried out, followed by filtration, washing, and drying to obtain the ternary material precursor.

[0135] In the mixed salt solution described in step (3), the total concentration of metal ions is 2.5 mol / L, the molar ratio of Ni ions, Co ions and Mn ions is 60:20:20, and the anion is chloride ions.

[0136] Example 3

[0137] This embodiment provides a ternary material precursor, which includes a core, an intermediate layer covering the core, and an outer coating layer covering the intermediate layer.

[0138] The core, intermediate layer and outer cladding layer all include Ni, Co and Mn elements;

[0139] In the core, the total molar amount of Ni, Co and Mn elements is in a molar ratio of 100:0.1 to Mg; the molar ratio of Ni, Co and Mn elements in the core is 90:5:5.

[0140] The molar ratio of Ni, Co and Mn elements in the intermediate layer is 70:20:10;

[0141] The molar ratio of Ni, Co and Mn elements in the outer coating layer is 50:10:40;

[0142] The ratio of the D50 particle size of the core to the sum of the thicknesses of the intermediate layer and the outer coating layer is 8.5:3.5. The D50 particle size of the core is 8.5 μm, the thickness of the intermediate layer is 1 μm, the thickness of the outer coating layer is 2.5 μm, and the D50 particle size of the ternary material precursor is 12.0 μm.

[0143] The preparation method of the ternary material precursor includes:

[0144] (1) In a nitrogen atmosphere, a mixed salt solution, a sodium hydroxide aqueous solution with a mass concentration of 40 wt% and an ammonia solution with a mass concentration of 30 wt% are simultaneously added to a bottom solution with a pH of 12, a temperature of 40°C and an ammonia concentration of 12 g / L. The pH is controlled at 11, the ammonia concentration is 10 g / L and the temperature is 40°C to carry out the first coprecipitation and obtain a first solution with a first precipitate.

[0145] In the mixed salt solution described in step (1), the total concentration of metal ions is 1.0 mol / L, the ratio of the total molar amount of Ni ions, Co ions and Mn ions to the molar amount of Mg ions is 100:0.1, the molar ratio of Ni ions, Co ions and Mn ions is 90:5:5, and the anion is sulfate ions;

[0146] (2) In a nitrogen atmosphere, a mixed salt solution, a sodium hydroxide aqueous solution with a mass concentration of 40 wt%, and ammonia solution with a mass concentration of 30 wt% are simultaneously added to the first solution obtained in step (1). The pH is controlled at 11, the ammonia concentration is 9 g / L, and the temperature is 40 °C to carry out a second coprecipitation and obtain a second solution with a second precipitate.

[0147] In the mixed salt solution described in step (2), the total concentration of metal ions is 1.0 mol / L, the molar ratio of Ni ions, Co ions and Mn ions is 70:20:10, and the anion is sulfate ions;

[0148] (3) In a nitrogen atmosphere, a mixed salt solution, a sodium hydroxide aqueous solution with a mass concentration of 40 wt%, and ammonia solution with a mass concentration of 30 wt% are simultaneously added to the second solution obtained in step (2). The pH is controlled at 11, the ammonia concentration is 9 g / L, and the temperature is 40℃. A third co-precipitation is carried out, followed by filtration, washing, and drying to obtain the ternary material precursor.

[0149] In the mixed salt solution described in step (3), the total concentration of metal ions is 1.0 mol / L, the molar ratio of Ni ions, Co ions and Mn ions is 50:10:40, and the anion is sulfate ions.

[0150] Example 4

[0151] This embodiment provides a ternary material precursor, which includes a core, an intermediate layer covering the core, and an outer coating layer covering the intermediate layer.

[0152] The core, intermediate layer and outer cladding layer all include Ni, Co and Mn elements;

[0153] In the core, the total molar amount of Ni, Co and Mn elements is in a molar ratio of 100:0.3 to Mg; the molar ratio of Ni, Co and Mn elements in the core is 98:1:1.

[0154] The molar ratio of Ni, Co and Mn elements in the intermediate layer is 80:10:10;

[0155] The molar ratio of Ni, Co and Mn elements in the outer coating layer is 60:10:30;

[0156] The ratio of the D50 particle size of the core to the sum of the thicknesses of the intermediate layer and the outer coating layer is 9.8:2.1. The D50 particle size of the core is 9.8 μm, the thickness of the intermediate layer is 0.6 μm, the thickness of the outer coating layer is 1.5 μm, and the D50 particle size of the ternary material precursor is 11.9 μm.

[0157] The preparation method of the ternary material precursor includes:

[0158] (1) In a nitrogen atmosphere, a mixed salt solution, a sodium hydroxide aqueous solution with a mass concentration of 20 wt%, and an ammonia solution with a mass concentration of 10 wt% are simultaneously added to a bottom solution with a pH of 11, a temperature of 80°C, and an ammonia concentration of 4 g / L. The pH is controlled at 10, the ammonia concentration is 4 g / L, and the temperature is 80°C to carry out the first coprecipitation and obtain a first solution with a first precipitate.

[0159] In the mixed salt solution described in step (1), the total concentration of metal ions is 2.5 mol / L, the ratio of the total molar amount of Ni ions, Co ions and Mn ions to the molar amount of Mg ions is 100:0.3, the molar ratio of Ni ions, Co ions and Mn ions is 98:1:1, and the anion is sulfate ions;

[0160] (2) In a nitrogen atmosphere, a mixed salt solution, a sodium hydroxide aqueous solution with a mass concentration of 20 wt%, and ammonia solution with a mass concentration of 10 wt% are simultaneously added to the first solution obtained in step (1). The pH is controlled at 10, the ammonia concentration is 4 g / L, and the temperature is 80℃ to carry out a second coprecipitation and obtain a second solution with a second precipitate.

[0161] In the mixed salt solution described in step (2), the total concentration of metal ions is 2.5 mol / L, the molar ratio of Ni ions, Co ions and Mn ions is 80:10:10, and the anion is sulfate ions;

[0162] (3) In a nitrogen atmosphere, a mixed salt solution, a sodium hydroxide aqueous solution with a mass concentration of 20 wt%, and ammonia solution with a mass concentration of 10 wt% are simultaneously added to the second solution obtained in step (2). The pH is controlled at 10, the ammonia concentration is 4 g / L, and the temperature is 80℃. A third co-precipitation is carried out, followed by filtration, washing, and drying to obtain the ternary material precursor.

[0163] In the mixed salt solution described in step (3), the total concentration of metal ions is 2.5 mol / L, the molar ratio of Ni ions, Co ions and Mn ions is 60:10:30, and the anion is sulfate ions.

[0164] Example 5

[0165] This embodiment provides a ternary material precursor, wherein, except for the core, the total molar amount of Ni, Co and Mn elements is in a molar ratio of 100:0.05 to Mg.

[0166] In step (1) of the method for preparing the ternary material precursor, the ratio of the total molar amount of Ni ions, Co ions and Mn ions to the molar amount of Mg ions in the mixed salt solution is 100:0.05, and all other steps are the same as in Example 1.

[0167] Example 6

[0168] This embodiment provides a ternary material precursor, wherein, except for the core, the total molar amount of Ni, Co and Mn elements is in a molar ratio of 100:0.5 to Mg.

[0169] In step (1) of the method for preparing the ternary material precursor, the ratio of the total molar amount of Ni ions, Co ions and Mn ions to the molar amount of Mg ions in the mixed salt solution is 100:0.5, and all other steps are the same as in Example 1.

[0170] Example 7

[0171] This embodiment provides a ternary material precursor, which is the same as in Embodiment 1 except that the ratio of the D50 particle size of the core to the sum of the thicknesses of the intermediate layer and the outer coating layer is 7.5:3.6, the D50 particle size of the core is 7.5 μm, the thickness of the intermediate layer is 1.0 μm, the thickness of the outer coating layer is 2.6 μm, and the D50 particle size of the ternary material precursor is 11.1 μm.

[0172] Example 8

[0173] This embodiment provides a ternary material precursor, which is the same as in Embodiment 1 except that the ratio of the D50 particle size of the core to the sum of the thicknesses of the intermediate layer and the outer coating layer is 10:1.1, the D50 particle size of the core is 10.0 μm, the thickness of the intermediate layer is 0.3 μm, the thickness of the outer coating layer is 0.8 μm, and the D50 particle size of the ternary material precursor is 11.1 μm.

[0174] Comparative Example 1

[0175] This comparative example provides a ternary material precursor, except that the Mg element in the core is omitted;

[0176] In other words, step (1) of the preparation method of the ternary material precursor is omitted. Except for the Mg ions in the mixed salt solution, everything else is the same as in Example 1.

[0177] Comparative Example 2

[0178] This comparative example provides a ternary material precursor, except that the Mg element in the core is omitted and the intermediate layer contains the Mg element, and the total molar amount of Ni, Co and Mn elements in the intermediate layer is in a molar ratio of 100:0.2 to the Mg element.

[0179] That is, the Mg ions in the mixed salt solution in step (1) of the preparation method of the ternary material precursor are omitted; and the Mg ions are included in the mixed salt solution in step (2), and the ratio of the total molar amount of Ni ions, Co ions and Mn ions to the molar amount of Mg ions is 100:0.2, except that the rest are the same as in Example 1.

[0180] Comparative Example 3

[0181] This comparative example provides a ternary material precursor, except that the Mg element in the core is omitted and the outer coating layer contains the Mg element, and the total molar amount of Ni, Co and Mn elements in the outer coating layer is in a molar ratio of 100:0.2 to the Mg element.

[0182] That is, the Mg ions in the mixed salt solution in step (1) of the preparation method of the ternary material precursor are omitted; and the Mg ions are included in the mixed salt solution in step (2), and the ratio of the total molar amount of Ni ions, Co ions and Mn ions to the molar amount of Mg ions is 100:0.2, except that the rest are the same as in Example 1.

[0183] Ternary cathode materials were prepared using the ternary precursors provided in the above embodiments and comparative examples. The method for preparing ternary cathode materials is as follows: the ternary precursors and lithium hydroxide are mixed in a ratio of 1:1.05 and sintered at 650°C for 8 hours to obtain ternary cathode materials.

[0184] The positive electrode sheet is prepared using the ternary positive electrode material. The method for preparing the positive electrode sheet is as follows: the obtained ternary positive electrode material, conductive carbon black and polyvinylidene fluoride are mixed in a mass ratio of 90:5:5, and N-methylpyrrolidone is used as a solvent to stir and obtain a slurry; the slurry is uniformly coated onto aluminum foil using a doctor blade with a coating gap of 100 μm; after coating, it is first dried by blowing air, then rolled and cut into circular electrode sheets, and then vacuum dried and cooled to obtain a positive electrode sheet for button half-cells.

[0185] A coin cell is prepared using the aforementioned positive electrode sheet. The method for preparing the coin cell is as follows: using the obtained coin half-cell positive electrode sheet as the positive electrode, a lithium metal sheet as the negative electrode, a PP microporous membrane as the separator, and a lithium battery basic electrolyte (the solvent includes: 20 wt% ethylene carbonate, 30 wt% dimethyl carbonate, and 50 wt% methyl ethyl carbonate; the solvent includes: 1.0 mol / L lithium hexafluorophosphate), and then assembling the cells to obtain the coin cell.

[0186] The electrochemical performance of the obtained coin cells was tested. The test method was as follows: the electrochemical performance of the coin cells was tested at a rate of 0.1C within a voltage range of 2.8~4.3V at 25℃. The initial discharge capacity at 25℃ and the capacity retention rate after 300 cycles are shown in Table 1.

[0187] Table 1

[0188]

[0189] From Table 1, we can obtain:

[0190] (1) The ternary cathode materials prepared using the ternary precursors provided in Examples 1-4 have higher initial discharge capacity and higher cycle stability;

[0191] (2) By comparing Examples 1 with 5 and 6, it can be seen that in the core of the present invention, the total molar amount of Ni, Co and Mn elements and the molar ratio of Mg elements will affect the performance of the ternary precursor and the ternary cathode material. When the total molar amount of Ni, Co and Mn elements and the molar ratio of Mg elements in the core is 100:(0.1~0.3), the ternary precursor and the ternary cathode material have better comprehensive performance. This is because the Mg doping amount in the core reaches the best balance under this molar ratio. The appropriate amount of Mg doping optimizes the lithium ion migration channel and reduces the volume change stress during cycling. Thus, while maintaining high capacity, it significantly improves the cycling stability of the material and avoids the negative impact of excessive doping on lithium ion diffusion kinetics and capacity.

[0192] (3) By comparing Examples 1 with 7 and 8, it can be seen that the ratio of the D50 particle size of the core to the sum of the thicknesses of the intermediate layer and the outer coating layer will affect the performance of the ternary precursor and the ternary cathode material. When the ratio of the D50 particle size of the core to the sum of the thicknesses of the intermediate layer and the outer coating layer is (8.5~9.8):(2.1~3.5), the ternary precursor and the ternary cathode material have better overall performance. This is because this ratio optimizes the structural stress distribution and ion transport dynamics of the ternary precursor and the ternary cathode material. The appropriate core size provides a guarantee for high capacity, while the intermediate layer and the outer coating layer with appropriate thickness can effectively stabilize the interface performance of the ternary cathode material prepared from the ternary precursor and suppress microcracks and side reactions caused by lattice parameter mismatch during cycling.

[0193] (4) By comparing Example 1 with Comparative Examples 1 to 3, it can be seen that the ternary precursor provided by the present invention has a high nickel content in the core (the molar fraction of Ni in the core is greater than the molar fraction of Ni in the intermediate layer and the outer coating layer), which can meet the high capacity requirements of the ternary cathode material. However, the high nickel content will lead to a decrease in the thermal stability and structural stability of the material. Therefore, in the present invention, Mg is used to dope the core. On the one hand, the doping of the core with Mg element inhibits the mixing of Ni cations in the core and improves the structural stability of the ternary precursor, thereby improving the structural stability of the ternary cathode material. On the other hand, the introduction of Mg element also optimizes the lithium ion diffusion channel and alleviates the volume expansion of the ternary cathode material during charging and discharging, thereby improving the cycle stability of the ternary cathode material.

[0194] This invention employs a high-nickel core, combined with Mg doping, which enables the ternary cathode material prepared from the ternary material precursor to have high capacity, as well as high structural stability and cycle stability. This results in a battery containing ternary cathode material that simultaneously possesses high capacity and excellent cycle stability.

[0195] 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 ternary material precursor, characterized in that, The ternary material precursor includes a core, an intermediate layer covering the core, and an outer coating layer covering the intermediate layer. The core, intermediate layer and outer cladding layer all include Ni, Co and Mn elements; The Ni content in the core is greater than the Ni content in the intermediate layer and the outer coating layer, and the core is doped with Mg.

2. The ternary material precursor according to claim 1, characterized in that, In the core, the total molar amount of Ni, Co and Mn elements is in a molar ratio of 100:(0.1~0.3) to Mg elements. Preferably, the molar ratio of Ni, Co and Mn in the core is (90~98):(1~5):(1~5).

3. The ternary material precursor according to claim 1 or 2, characterized in that, The ratio of the D50 particle size of the core to the sum of the thicknesses of the intermediate layer and the outer coating layer is (8.5~9.8):(2.1~3.5); Preferably, the D50 particle size of the core is 8.5μm~9.8μm; Preferably, the thickness of the intermediate layer is 0.6 μm to 1 μm; Preferably, the thickness of the outer coating layer is 1.5μm to 2.5μm.

4. The ternary material precursor according to any one of claims 1 to 3, characterized in that, The Ni content in the intermediate layer is greater than the Ni content in the outer coating layer; Preferably, the molar ratio of Ni, Co and Mn in the intermediate layer is (70~80):(10~20):(10~20); Preferably, the molar ratio of Ni, Co and Mn in the outer coating layer is (50~60):(10~20):(20~40).

5. A method for preparing the ternary material precursor according to any one of claims 1 to 4, characterized in that, The preparation method includes: (1) The mixed salt solution, along with the precipitant solution and the complexing agent solution, are simultaneously added to the base liquid to carry out the first co-precipitation, thereby obtaining a first solution with the first precipitate; (2) The mixed salt solution, precipitant solution and complexing agent solution are simultaneously added to the first solution obtained in step (1) to carry out the second coprecipitation and obtain the second solution with the second precipitate; (3) The mixed salt solution, precipitant solution and complexing agent solution are simultaneously added to the second solution obtained in step (2) to carry out the third co-precipitation and obtain the ternary material precursor; The mixed salt solutions described in steps (1), (2), and (3) all contain Ni ions, Co ions, and Mn ions, and the mixed salt solution described in step (1) also contains Mg ions; In step (1), the molar amount of Ni ions in the first coprecipitation reaction is greater than the molar amount of Ni ions in the second coprecipitation reaction and the third coprecipitation reaction in step (3).

6. The preparation method according to claim 5, characterized in that, In the mixed salt solution described in step (1), the ratio of the total molar amount of Ni ions, Co ions and Mn ions to the molar amount of Mg ions is 100:(0.1~0.3); Preferably, in the mixed salt solution described in step (1), the molar ratio of Ni ions, Co ions and Mn ions is (90~98):(1~5):(1~5); Preferably, the total concentration of metal ions in the mixed salt solution in step (1) is 1.0 mol / L to 2.5 mol / L.

7. The preparation method according to claim 5, characterized in that, In the mixed salt solution described in step (2), the molar ratio of Ni ions, Co ions and Mn ions is (70~80):(10~20):(10~20); Preferably, in the mixed salt solution described in step (2), the total concentration of metal ions is 1.0 mol / L to 2.5 mol / L; Preferably, in the mixed salt solution described in step (3), the molar ratio of Ni ions, Co ions and Mn ions is (50~60):(10~20):(20~40); Preferably, in the mixed salt solution described in step (3), the total concentration of metal ions is 1.0 mol / L to 2.5 mol / L; Preferably, in step (1), during the first coprecipitation, the pH is controlled to be 10-11, the complexing agent concentration is 4g / L-10g / L, and the temperature is 40℃-80℃; Preferably, in step (2), during the second coprecipitation, the pH is controlled to be 10-11, the complexing agent concentration is 4g / L-10g / L, and the temperature is 40℃-80℃; Preferably, during the third coprecipitation in step (3), the pH is controlled at 10~11, the concentration of the complexing agent is 4g / L~10g / L, and the temperature is 40℃~80℃.

8. The preparation method according to claim 5, characterized in that, The preparation method includes: (1) In a protective atmosphere, a mixed salt solution, a precipitant aqueous solution with a mass concentration of 20wt%~40wt% and a complexing agent aqueous solution with a mass concentration of 10wt%~30wt% are simultaneously added to a base solution with a pH of 11~12, a temperature of 40℃~80℃ and a complexing agent concentration of 4g / L~12g / L. The pH is controlled at 10~11, the complexing agent concentration is 4g / L~10g / L, and the temperature is 40℃~80℃ to carry out the first coprecipitation and obtain a first solution with a first precipitate. In the mixed salt solution described in step (1), the total concentration of metal ions is 1.0 mol / L to 2.5 mol / L, the ratio of the total molar amount of Ni ions, Co ions and Mn ions to the molar amount of Mg ions is 100:(0.1~0.3), the molar ratio of Ni ions, Co ions and Mn ions is (90~98):(1~5):(1~5), and the anions include sulfate ions and / or chloride ions; (2) In a protective atmosphere, a mixed salt solution, a precipitant aqueous solution with a mass concentration of 20wt%~40wt% and a complexing agent aqueous solution with a mass concentration of 10wt%~30wt% are simultaneously added to the first solution obtained in step (1). The pH is controlled at 10~11, the complexing agent concentration is 4g / L~10g / L, and the temperature is 40℃~80℃ to carry out a second coprecipitation and obtain a second solution with a second precipitate. In the mixed salt solution described in step (2), the total concentration of metal ions is 1.0 mol / L to 2.5 mol / L, and the molar ratio of Ni ions, Co ions and Mn ions is (70~80):(10~20):(10~20). The anions include sulfate ions and / or chloride ions. (3) In a protective atmosphere, a mixed salt solution, a precipitant aqueous solution with a mass concentration of 20wt%~40wt% and a complexing agent aqueous solution with a mass concentration of 10wt%~30wt% are simultaneously added to the second solution obtained in step (2). The pH is controlled at 10~11, the complexing agent concentration is 4g / L~10g / L, and the temperature is 40℃~80℃ for a third co-precipitation. Then, the solution is filtered, washed and dried in sequence to obtain the ternary material precursor. In the mixed salt solution described in step (3), the total concentration of metal ions is 1.0 mol / L to 2.5 mol / L, and the molar ratio of Ni ions, Co ions and Mn ions is (50~60):(10~20):(20~40). The anions include sulfate ions and / or chloride ions. In step (1), the molar amount of Ni ions in the first coprecipitation reaction is greater than the molar amount of Ni ions in the second coprecipitation reaction and the third coprecipitation reaction in step (3).

9. A ternary cathode material, characterized in that, The ternary cathode material is prepared from the ternary material precursor described in any one of claims 1 to 4.

10. A battery, characterized in that, The battery comprises the ternary cathode material as described in claim 9.

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