A precursor material containing a niobium-doped shell and its preparation, cathode material and battery

Abstract

This invention provides a precursor material comprising a niobium-doped shell layer, its preparation, a cathode material, and a battery. The precursor material includes a nickel-cobalt-manganese (NiCoMn) core, an intermediate coating layer, and a NiCoMn-doped niobium shell layer. The intermediate coating layer comprises at least one set of stacked shell layers, including stacked niobium-doped NiCoMn shell layers and NiCoMn shell layers. In each stacked shell layer, the NiCoMn-doped niobium shell layer is close to the NiCoMn core, while the NiCoMn shell layer is far from the NiCoMn core. The precursor material provided by this invention employs a multi-layered niobium-doped shell layer, resulting in more uniform solid-phase diffusion of niobium during sintering, thereby achieving uniform niobium doping in the cathode material and improving the stability of the cathode material.

Description

Technical Field

[0001] This invention belongs to the field of battery technology, and relates to a precursor material containing a niobium-doped shell, and more particularly to a precursor material containing a niobium-doped shell, its preparation, a cathode material, and a battery. Background Technology

[0002] Lithium-ion batteries have rapidly developed and become commercialized due to their advantages such as high energy density, superior cycle stability, and low pollution. They play an increasingly important role in fields such as 3C digital products, electric vehicles, intelligent robots, and aerospace. Cathode materials are a key research focus in lithium-ion batteries. Among them, high-nickel ternary cathode materials exhibit superior overall performance, with excellent specific energy, specific power, and lifespan, leading to their rapid market dominance. However, for high-nickel ternary cathode materials, the high lithium-nickel mixture can cause rapid capacity decay. Currently, structural design and doping coating can effectively mitigate this phenomenon.

[0003] Studies have shown that niobium doping can improve the stability and conductivity of layered cathode materials, thereby improving their rate performance. High-nickel niobium doping internally helps reduce Li- content during subsequent calcination to prepare the cathode material. + / Ni 2+ Mixed distribution. For the surface, niobium coating can reduce the direct contact between the electrolyte and the surface of highly active cathode particles, improve cycle stability, and thus extend service life. However, the niobium distribution in niobium-doped cathode materials prepared using precursor materials disclosed in the prior art is uneven.

[0004] CN114715957A discloses a method for obtaining a nickel-cobalt-manganese ternary precursor via a co-precipitation reaction. At the end of the reaction, the ternary metal liquid is stopped, and niobium liquid is introduced to coat the precursor with niobium. Following this, lithiation and calcination are performed to obtain a niobium-doped cathode material. However, during the calcination process, niobium diffusion occurs in the nickel-cobalt-manganese ternary precursor, resulting in an uneven distribution of niobium within the precursor. This phenomenon is particularly pronounced after sintering large-particle precursors.

[0005] CN113851633B discloses a method for preparing a hydroxide precursor by co-precipitation, which is then uniformly mixed with a lithium source and a niobium source and sintered under an oxidizing atmosphere to obtain a niobium-doped ternary cathode material. The obtained niobium-doped ternary cathode material is then uniformly mixed with niobium phosphate and sintered again to obtain a niobium-doped high-nickel ternary cathode material coated with niobium phosphate. However, the steps for preparing the niobium coating in this method are relatively complex, and the niobium doping in the obtained niobium-doped ternary cathode material is not uniform enough.

[0006] Existing niobium-doped precursor materials all have certain drawbacks, including uneven niobium distribution in the cathode material prepared after calcination. Therefore, developing and designing a novel precursor material with a niobium-doped shell, as well as its preparation, cathode material, and battery are crucial. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a precursor material containing a niobium-doped shell, its preparation, a cathode material, and a battery. The precursor material provided by the present invention employs a multi-layered niobium-doped shell, which makes the solid-phase diffusion of niobium more uniform during sintering, thereby achieving uniform niobium doping in the cathode material, improving the stability of the cathode material, and increasing its conductivity. Secondly, the precursor material provided by this application uses the same element for doping and coating, which can improve the delamination phenomenon of the cathode material after sintering to a certain extent. In addition, the multi-shell structure inside the precursor material provided by this application helps to prevent cracks from propagating from the inside to the outside, improving the morphology and performance of large-particle-size ternary precursors.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a precursor material comprising a niobium-doped shell, the precursor material comprising a nickel-cobalt-manganese core, an intermediate cladding layer, and a nickel-cobalt-manganese niobium-doped shell;

[0010] The intermediate cladding layer includes at least one set of stacked shell layers, the stacked shell layers including stacked niobium-doped nickel-cobalt-manganese shell layers and nickel-cobalt-manganese shell layers, wherein the nickel-cobalt-manganese niobium-doped shell layer in each stacked shell layer is close to the nickel-cobalt-manganese core, and the nickel-cobalt-manganese shell layer is far away from the nickel-cobalt-manganese core.

[0011] The precursor material provided by this invention employs a multi-layered niobium-doped shell, which makes the solid-phase diffusion of niobium more uniform during sintering, thereby achieving the goal of uniform niobium doping in the cathode material, improving the stability of the cathode material, and increasing conductivity. Secondly, the precursor material provided by this application uses the same element for doping and coating, which can improve the delamination phenomenon of the cathode material after sintering to a certain extent. In addition, the precursor material provided by this application has a multi-shell structure inside, which helps to prevent cracks from propagating from the inside to the outside and improves the morphology and performance of large-particle-size ternary precursors.

[0012] Preferably, the D50 particle size of the nickel-cobalt-manganese core is 3 to 7 μm, for example, it can be 3 μm, 3.2 μm, 3.4 μm, 3.6 μm, 3.8 μm, 4 μm, 4.2 μm, 4.4 μm, 4.6 μm, 4.8 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm or 7 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0013] Preferably, the thickness of the niobium-doped nickel-cobalt-manganese shell layers in the stacked shell layers increases sequentially along the direction away from the nickel-cobalt-manganese core.

[0014] In this invention, away from the nickel-cobalt-manganese core, the thickness of the nickel-cobalt-manganese niobium-doped shell layers in the stacked shell layers increases sequentially, with the outermost nickel-cobalt-manganese niobium-doped shell layer being the thickest. This ensures that during the subsequent sintering of the precursor material containing the niobium-doped shell layer to prepare the cathode material, the diffusion amount of niobium inside can be relatively consistent during the solid-phase diffusion process.

[0015] Preferably, the thickness of the nickel-cobalt-manganese shell layers in the stacked shell layers decreases sequentially along the direction away from the nickel-cobalt-manganese core.

[0016] In this invention, the thickness of the nickel-cobalt-manganese shell decreases sequentially along the direction away from the nickel-cobalt-manganese core, thereby reducing the spacing between the nickel-cobalt-manganese niobium-doped shells and achieving the purpose of hindering crack propagation.

[0017] Preferably, the thickness of the nickel-cobalt-manganese-niobium-doped shell layer in the stacked shell layer is independently 0.01 to 5 μm, for example, it can be 0.01 μm, 0.02 μm, 0.05 μm, 0.07 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm or 5 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0018] Preferably, the thickness of the nickel-cobalt-manganese shell layer in the stacked shell layer is independently 0.01 to 5 μm, for example, it can be 0.01 μm, 0.02 μm, 0.05 μm, 0.07 μm, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm or 5 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0019] Preferably, the thickness of the nickel-cobalt-manganese-niobium-doped shell is greater than the thickness of the nickel-cobalt-manganese-niobium-doped shell layers in all the stacked shell layers.

[0020] Preferably, the thickness of the nickel-cobalt-manganese-niobium-doped shell is not less than 0.5 μm, for example, it can be 0.5 μm, 0.55 μm, 0.6 μm, 0.65 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 2 μm or 3 μm, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0021] Preferably, the D50 particle size of the precursor material is not less than 7 μm, for example, it can be 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm or 12 μm, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0022] Preferably, the chemical formula of the precursor material is Ni x Co y Mn z Nb m (OH)2, where 0.5 ≤ x ≤ 0.95, 0 < y ≤ 0.5, 0 < z ≤ 0.5, 0.01 ≤ m ≤ 0.03; where, for 0.5 ≤ x ≤ 0.95, the value of x can be, for example, 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9 or 0.95, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable; where, for 0 < y ≤ 0.5, the value of y can be, for example, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 or 0.5, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable; where, for 0 < z ≤ 0.5, the value of z can be, for example, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 or 0.5, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable; where, for 0.01 ≤ m ≤ 0.03, the value of m can be, for example, 0.01, 0.015, 0.02, 0.025 or 0.03, but is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0023] In a second aspect, the present invention provides a method for preparing the precursor material described in the first aspect, and the preparation method includes:

[0024] (1) Adding a mixed solution containing nickel salt, cobalt salt and manganese salt to the bottom liquid, and simultaneously adding a precipitant and a complexing agent until a nickel-cobalt-manganese core is obtained;

[0025] (2) Keeping the mixed solution, the precipitant and the complexing agent continuously introduced, and introducing a niobium source solution until a nickel-cobalt-manganese niobium-doped shell layer grows on the outside of the nickel-cobalt-manganese core obtained in step (1);

[0026] (3) Keeping the mixed solution, the precipitant and the complexing agent continuously introduced, and stopping the introduction of the niobium source solution until a nickel-cobalt-manganese shell layer grows on the outside of the nickel-cobalt-manganese niobium-doped shell layer obtained in step (2);

[0027] (4) If only one layer of nickel cobalt manganese doped niobium shell and nickel cobalt manganese shell is prepared, then the preparation of nickel cobalt manganese doped niobium shell is started directly; if more than one layer of nickel cobalt manganese doped niobium shell and nickel cobalt manganese shell is prepared, then steps (2) and (3) are repeated at least once before the preparation of nickel cobalt manganese doped niobium shell is prepared.

[0028] The method for preparing a nickel-cobalt-manganese niobium-doped shell is as follows: a mixed solution, a precipitant and a complexing agent are continuously introduced, and a niobium source solution is introduced until a nickel-cobalt-manganese niobium-doped shell is grown on the outside of the outermost nickel-cobalt-manganese shell layer.

[0029] The method for preparing precursor materials provided by this invention can prepare ternary precursors in one step. The method is simple, fast, and has high production efficiency. The cathode material prepared by precursor doping and coating has high stability, and the battery prepared with the obtained cathode material has high battery operating voltage and high battery energy density.

[0030] Preferably, the temperature of the base liquid in step (1) is 50-70°C, the pH is 9-12, and the ammonia concentration is 4-10 g / L.

[0031] The temperature of the base liquid in step (1) of the present invention is 50 to 70°C, for example, it can be 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, 62°C, 64°C, 66°C, 68°C or 70°C, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0032] The pH of the base solution in step (1) of this invention is 9 to 12, for example, it can be 9, 9.2, 9.5, 9.7, 10, 10.2, 10.5, 10.7, 11, 11.2, 11.5, 11.7 or 12, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0033] The ammonia concentration of the base liquid in step (1) of this invention is 4 to 10 g / L, for example, it can be 4 g / L, 4.5 g / L, 5 g / L, 5.5 g / L, 6 g / L, 6.5 g / L, 7 g / L, 7.5 g / L, 8 g / L, 8.5 g / L, 9 g / L, 9.5 g / L or 10 g / L, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0034] Preferably, the addition rate of the mixed solution in steps (1), (2), (3) and (4) is independently 4 to 40 L / h, for example, it can be 4 L / h, 6 L / h, 8 L / h, 10 L / h, 13 L / h, 15 L / h, 17 L / h, 20 L / h, 23 L / h, 25 L / h, 27 L / h, 30 L / h, 32 L / h, 35 L / h, 37 L / h or 40 L / h, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0035] Preferably, the concentration of nickel salt in the mixed solution in steps (1), (2), (3) and (4) is 30-95 g / L.

[0036] Preferably, the nickel salt comprises any one or a combination of at least two of nickel sulfate, nickel nitrate, or nickel chloride. Typical but non-limiting combinations include a combination of nickel sulfate and nickel nitrate, a combination of nickel nitrate and nickel chloride, or a combination of nickel sulfate, nickel nitrate, and nickel chloride.

[0037] Preferably, the concentration of cobalt salt in the mixed solution in steps (1), (2), (3) and (4) is not higher than 50 g / L. For example, it can be 50 g / L, 45 g / L, 40 g / L, 35 g / L, 30 g / L, 25 g / L, 20 g / L, 15 g / L, 10 g / L, 5 g / L or 1 g / L, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0038] Preferably, the cobalt salt includes any one or a combination of at least two of cobalt sulfate, cobalt nitrate, or cobalt chloride. Typical but non-limiting combinations include a combination of cobalt sulfate and cobalt nitrate, a combination of cobalt nitrate and cobalt chloride, or a combination of cobalt sulfate, cobalt nitrate, and cobalt chloride.

[0039] Preferably, the concentration of manganese salt in the mixed solution in steps (1), (2), (3) and (4) is not higher than 50 g / L. For example, it can be 50 g / L, 45 g / L, 40 g / L, 35 g / L, 30 g / L, 25 g / L, 20 g / L, 15 g / L, 10 g / L, 5 g / L or 1 g / L, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0040] Preferably, the manganese salt includes any one or a combination of at least two of manganese sulfate, manganese nitrate, or manganese chloride. Typical but non-limiting combinations include a combination of manganese sulfate and manganese nitrate, a combination of manganese nitrate and manganese chloride, or a combination of manganese sulfate, manganese nitrate, and manganese chloride.

[0041] Preferably, the addition rate of the precipitant in steps (1), (2), (3) and (4) is 1 to 10 L / h, for example, it can be 1 L / h, 2 L / h, 3 L / h, 4 L / h, 5 L / h, 6 L / h, 7 L / h, 8 L / h, 9 L / h or 10 L / h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0042] Preferably, the addition rate of the complexing agent in steps (1), (2), (3) and (4) is 0.5 to 15 L / h, for example, it can be 0.5 L / h, 1 L / h, 1.5 L / h, 2 L / h, 3 L / h, 4 L / h, 5 L / h, 6 L / h, 7 L / h, 8 L / h, 9 L / h, 10 L / h, 11 L / h, 12 L / h, 13 L / h, 14 L / h or 15 L / h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0043] Preferably, the precipitant in steps (1), (2), (3) and (4) includes an alkaline solution with a mass concentration of 20 to 40 wt%, for example, 20 wt%, 22 wt%, 24 wt%, 26 wt%, 28 wt%, 30 wt%, 32 wt%, 34 wt%, 36 wt%, 38 wt%, or 40 wt%, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0044] Preferably, the complexing agent in steps (1), (2), (3) and (4) comprises ammonia water and / or ammonium salt solution, and the mass concentration of the complexing agent is 10 to 20 wt%, for example, it can be 10 wt%, 11 wt%, 12 wt%, 13 wt%, 14 wt%, 15 wt%, 16 wt%, 17 wt%, 18 wt%, 19 wt% or 20 wt%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0045] Preferably, steps (1), (2), (3) and (4) are all carried out in a reaction vessel, and the pH of the liquid in the reaction vessel in steps (1), (2), (3) and (4) is maintained at 9 to 12, and the ammonia concentration is 4 to 12 g / L.

[0046] In this invention, the pH of the liquid in the reaction vessel described in steps (1), (2), (3) and (4) is maintained at 9 to 12. For example, it can be 9, 9.5, 10, 10.5, 11, 11.5 or 12, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0047] In this invention, the ammonia concentration of the liquid in the reaction vessel described in steps (1), (2), (3) and (4) is 4 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.

[0048] The niobium source solution mentioned in steps (2) and (4) of this invention includes, but is not limited to, niobium salt solution. Any solution that can provide niobium element in the prior art is applicable; the niobium salt solution includes niobium oxalate solution.

[0049] The concentration of the niobium source solution in steps (2) and (4) of this invention can be any concentration below the solubility of the niobium source, and all the niobium source in the niobium source solution is dissolved.

[0050] Preferably, the concentrations of the niobium source solutions in steps (2) and (4) are independently 0.1 to 100 g / L, for example, 0.1 g / L, 0.5 g / L, 1 g / L, 2 g / L, 5 g / L, 10 g / L, 20 g / L, 30 g / L, 40 g / L, 50 g / L, 60 g / L, 70 g / L, 80 g / L, 90 g / L or 100 g / L, but are not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0051] Preferably, the inlet rate of the niobium source solution in steps (2) and (4) is 1 to 10 L / h, for example, it can be 1 L / h, 2 L / h, 3 L / h, 4 L / h, 5 L / h, 6 L / h, 7 L / h, 8 L / h, 9 L / h or 10 L / h, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0052] As a preferred embodiment of the preparation method of the present invention, the preparation method includes:

[0053] (1) Add a mixed solution containing nickel salt, cobalt salt and manganese salt to a reaction vessel containing a base liquid at a temperature of 50-70℃, pH of 9-12 and ammonia concentration of 4-10 g / L at a rate of 4-40 L / h, and simultaneously add a precipitant and a complexing agent, keeping the pH of the liquid in the reaction vessel at 9-12 and the ammonia concentration at 4-12 g / L, until a nickel-cobalt-manganese core is obtained;

[0054] (2) The mixed solution is continuously fed into the reaction vessel at a rate of 4 to 40 L / h, and the precipitant and complexing agent are continuously fed into the reaction vessel simultaneously. A niobium source solution with a concentration of 0.1 to 100 g / L is fed into the reaction vessel at a rate of 1 to 10 L / h. The pH of the liquid in the reaction vessel is maintained at 9 to 12 and the ammonia concentration is maintained at 4 to 12 / L until a niobium-cobalt-manganese shell is grown on the outside of the nickel-cobalt-manganese core obtained in step (1).

[0055] (3) The mixed solution is continuously fed into the reaction vessel at a rate of 4 to 40 L / h. The precipitant and complexing agent are continuously fed into the reaction vessel simultaneously, and the niobium source solution is stopped. The pH of the liquid in the reaction vessel is kept at 9 to 12 and the ammonia concentration is kept at 4 to 12 / L until the nickel cobalt manganese niobium-doped shell obtained in step (2) is grown on the outside to obtain the nickel cobalt manganese shell.

[0056] (4) If only one layer of nickel cobalt manganese doped niobium shell and nickel cobalt manganese shell is prepared, then the preparation of nickel cobalt manganese doped niobium shell is started directly; if more than one layer of nickel cobalt manganese doped niobium shell and nickel cobalt manganese shell is prepared, then steps (2) and (3) are repeated at least once before the preparation of nickel cobalt manganese doped niobium shell is prepared.

[0057] The method for preparing a nickel-cobalt-manganese niobium-doped shell is as follows: a mixed solution is continuously fed into the reaction vessel at a rate of 4–40 L / h, a precipitant and a complexing agent are simultaneously and continuously fed into the reaction vessel, a niobium source solution with a concentration of 0.1–100 g / L is fed into the reaction vessel at a rate of 1–10 L / h, the pH of the liquid in the reaction vessel is maintained at 9–12, and the ammonia concentration is maintained at 4–12 g / L, until a nickel-cobalt-manganese niobium-doped shell is grown on the outside of the outermost nickel-cobalt-manganese shell layer.

[0058] Thirdly, the present invention provides a positive electrode material, wherein the positive electrode sheet comprises the precursor material described in the first aspect.

[0059] Fourthly, the present invention provides a battery comprising the positive electrode material described in the third aspect.

[0060] Compared with the prior art, the present invention has the following beneficial effects:

[0061] (1) The precursor material containing niobium-doped shell provided by the present invention adopts a multi-layer niobium-doped shell method, which makes the solid-phase diffusion of niobium more uniform during sintering, thereby achieving the purpose of uniform niobium doping in the cathode material, improving the stability of the cathode material and increasing conductivity; secondly, the precursor material provided by the present application uses the same element for doping and coating, which can improve the delamination phenomenon of the cathode material after sintering to a certain extent; in addition, the precursor material provided by the present application has a multi-shell structure inside, which is beneficial to prevent cracks from propagating from the inside to the outside and improve the morphology and performance of large-particle-size ternary precursors.

[0062] (2) The method for preparing precursor materials provided by the present invention can prepare ternary precursors in one step. The method is simple, fast and efficient. The cathode material prepared by precursor doping and coating has high stability. The battery prepared with the obtained cathode material has high battery working voltage and high battery energy density. Detailed Implementation

[0063] 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.

[0064] Example 1

[0065] This embodiment provides a precursor material containing a niobium-doped shell, wherein the precursor material has a D50 particle size of 13 μm; the precursor material includes a nickel-cobalt-manganese core with a D50 particle size of 5 μm, an intermediate coating layer, and a nickel-cobalt-manganese niobium-doped shell with a thickness of 1.5 μm;

[0066] The intermediate cladding layer includes a first stacked shell layer and a second stacked shell layer, both of which include a niobium-doped nickel-cobalt-manganese shell layer and a nickel-cobalt-manganese shell layer stacked together.

[0067] The first stacked shell layer has a niobium-doped nickel-cobalt-manganese shell layer with a thickness of 0.5 μm and a nickel-cobalt-manganese shell layer with a thickness of 3 μm; the second stacked shell layer has a niobium-doped nickel-cobalt-manganese shell layer with a thickness of 1 μm and a nickel-cobalt-manganese shell layer with a thickness of 2 μm.

[0068] The preparation method of the precursor material is as follows:

[0069] (1) Add a mixed solution containing nickel sulfate, cobalt sulfate and manganese sulfate (the total concentration of metal ions in the mixed solution is 100 g / L, and the molar ratio of nickel ions, cobalt ions and manganese ions is 90:6:4) to a reaction vessel containing a base liquid at a temperature of 60℃, pH of 10.5 and ammonia concentration of 7 g / L at a rate of 20 L / h, and simultaneously add sodium hydroxide solution and ammonia water to maintain the pH of the liquid in the reaction vessel at 10.5 and the ammonia concentration at 8 g / L until a nickel cobalt manganese core is obtained;

[0070] (2) The mixed solution is continuously fed into the reaction vessel at a rate of 20 L / h. Sodium hydroxide solution and ammonia water are simultaneously and continuously fed into the reaction vessel. Niobium oxalate solution with a concentration of 50 g / L is fed into the reaction vessel at a rate of 5 L / h. The pH of the liquid in the reaction vessel is kept at 10.5 and the ammonia concentration is 8 g / L until the nickel cobalt manganese core obtained in step (1) grows to obtain a nickel cobalt manganese niobium-doped shell.

[0071] (3) Keep the mixed solution continuously fed into the reaction vessel at a rate of 20 L / h, and keep the sodium hydroxide solution and ammonia water continuously fed into the reaction vessel at the same time, and stop the feeding of niobium oxalate solution. Keep the pH of the liquid in the reaction vessel at 10.5 and the ammonia concentration at 8 / L until the nickel cobalt manganese niobium-doped shell obtained in step (2) grows to obtain the nickel cobalt manganese shell.

[0072] (4) Repeat steps (2) and (3) once, and then prepare a nickel-cobalt-manganese-doped niobium shell;

[0073] The method for preparing a nickel-cobalt-manganese niobium-doped shell is as follows: a mixed solution is continuously fed into the reaction vessel at a rate of 20 L / h, sodium hydroxide solution and ammonia water are simultaneously and continuously fed into the reaction vessel, and a niobium oxalate solution with a concentration of 50 g / L is fed into the reaction vessel at a rate of 5 L / h. The pH of the liquid in the reaction vessel is maintained at 10.5 and the ammonia concentration is 8 g / L, until a nickel-cobalt-manganese niobium-doped shell is grown on the outside of the outermost nickel-cobalt-manganese shell layer.

[0074] Example 2

[0075] This embodiment provides a precursor material containing a niobium-doped shell, wherein the precursor material has a D50 particle size of 7 μm; the precursor material includes a nickel-cobalt-manganese core with a D50 particle size of 3 μm, an intermediate coating layer, and a nickel-cobalt-manganese niobium-doped shell with a thickness of 1 μm;

[0076] The intermediate cladding layer includes a stacked shell layer, which includes a niobium-doped nickel-cobalt-manganese shell layer and a nickel-cobalt-manganese shell layer stacked together.

[0077] The thickness of the nickel-cobalt-manganese-niobium-doped shell in the stacked shell is 1 μm, and the thickness of the nickel-cobalt-manganese shell is 2 μm.

[0078] The preparation method of the precursor material is as follows:

[0079] (1) Add a mixed solution containing nickel sulfate, cobalt sulfate and manganese sulfate (the total concentration of metal ions in the mixed solution is 100 g / L, and the molar ratio of nickel ions, cobalt ions and manganese ions is 90:6:4) to a reaction vessel containing a bottom liquid at a temperature of 50℃, pH of 9 and ammonia concentration of 4 g / L at a rate of 40 L / h, and simultaneously add sodium hydroxide solution and ammonia water to maintain the pH of the liquid in the reaction vessel at 9 and the ammonia concentration at 4 g / L until a nickel cobalt manganese core is obtained;

[0080] (2) The mixed solution is continuously fed into the reaction vessel at a rate of 40 L / h. Sodium hydroxide solution and ammonia water are simultaneously and continuously fed into the reaction vessel. Niobium oxalate solution with a concentration of 0.1 g / L is fed into the reaction vessel at a rate of 10 L / h. The pH of the liquid in the reaction vessel is kept at 9 and the ammonia concentration is 4 g / L until the nickel cobalt manganese core obtained in step (1) grows to obtain a nickel cobalt manganese niobium-doped shell.

[0081] (3) The mixed solution is continuously fed into the reaction vessel at a rate of 40 L / h. Sodium hydroxide solution and ammonia water are continuously fed into the reaction vessel simultaneously, and the feeding of niobium oxalate solution is stopped. The pH of the liquid in the reaction vessel is kept at 9 and the ammonia concentration is 4 / L until the niobium-doped shell of nickel cobalt manganese obtained in step (2) is grown on the outside to obtain a nickel cobalt manganese shell.

[0082] (4) Directly begin the preparation of the nickel-cobalt-manganese-doped niobium shell;

[0083] The method for preparing a nickel-cobalt-manganese niobium-doped shell is as follows: a mixed solution is continuously fed into the reaction vessel at a rate of 40 L / h, sodium hydroxide solution and ammonia water are simultaneously and continuously fed into the reaction vessel, and a niobium oxalate solution with a concentration of 0.1 g / L is fed into the reaction vessel at a rate of 10 L / h. The pH of the liquid in the reaction vessel is maintained at 9 and the ammonia concentration is 4 g / L, until a nickel-cobalt-manganese niobium-doped shell is grown on the outside of the outermost nickel-cobalt-manganese shell layer.

[0084] Example 3

[0085] This embodiment provides a precursor material containing a niobium-doped shell, wherein the precursor material has a D50 particle size of 20 μm; the precursor material includes a nickel-cobalt-manganese core with a D50 particle size of 7 μm, an intermediate coating layer, and a nickel-cobalt-manganese niobium-doped shell with a thickness of 3 μm;

[0086] The intermediate coating layer includes a first stacked shell layer, a second stacked shell layer, a third stacked shell layer and a fourth stacked shell layer, wherein the first stacked shell layer, the second stacked shell layer, the third stacked shell layer and the fourth stacked shell layer each include a niobium-doped nickel-cobalt-manganese shell layer and a nickel-cobalt-manganese shell layer stacked together.

[0087] The first stacked shell layer has a nickel-cobalt-manganese-niobium doped shell layer with a thickness of 0.5 μm and a nickel-cobalt-manganese shell layer with a thickness of 2 μm; the second stacked shell layer has a nickel-cobalt-manganese-niobium doped shell layer with a thickness of 1 μm and a nickel-cobalt-manganese shell layer with a thickness of 1.5 μm; the third stacked shell layer has a nickel-cobalt-manganese-niobium doped shell layer with a thickness of 1.5 μm and a nickel-cobalt-manganese shell layer with a thickness of 1 μm; and the fourth stacked shell layer has a nickel-cobalt-manganese-niobium doped shell layer with a thickness of 2 μm and a nickel-cobalt-manganese shell layer with a thickness of 0.5 μm.

[0088] The preparation method of the precursor material is as follows:

[0089] (1) Add a mixed solution containing nickel sulfate, cobalt sulfate and manganese sulfate (the total concentration of metal ions in the mixed solution is 100 g / L, and the molar ratio of nickel ions, cobalt ions and manganese ions is 90:6:4) to a reaction vessel containing a bottom liquid at a temperature of 70℃, pH of 12 and ammonia concentration of 10 g / L at a rate of 4 h / h, and simultaneously add sodium hydroxide solution and ammonia water, keeping the pH of the liquid in the reaction vessel at 12 and the ammonia concentration at 12 g / L, until a nickel cobalt manganese core is obtained;

[0090] (2) The mixed solution is continuously fed into the reaction vessel at a rate of 4 L / h. Sodium hydroxide solution and ammonia water are simultaneously and continuously fed into the reaction vessel. Niobium oxalate solution with a concentration of 100 g / L is fed into the reaction vessel at a rate of 1 L / h. The pH of the liquid in the reaction vessel is kept at 12 and the ammonia concentration is kept at 12 / L until the nickel cobalt manganese core obtained in step (1) grows to obtain a nickel cobalt manganese niobium-doped shell.

[0091] (3) Keep the mixed solution continuously fed into the reaction vessel at a rate of 4L / h, and keep the sodium hydroxide solution and ammonia water continuously fed into the reaction vessel at the same time, and stop the feeding of niobium oxalate solution. Keep the pH of the liquid in the reaction vessel at 12 and the ammonia concentration at 12 / L until the nickel cobalt manganese niobium-doped shell obtained in step (2) grows to obtain the nickel cobalt manganese shell.

[0092] (4) Repeat steps (2) and (3) three times, and then prepare a nickel-cobalt-manganese-doped niobium shell;

[0093] The method for preparing a nickel-cobalt-manganese niobium-doped shell is as follows: a mixed solution is continuously fed into the reaction vessel at a rate of 4 L / h, sodium hydroxide solution and ammonia water are simultaneously and continuously fed into the reaction vessel, and a niobium oxalate solution with a concentration of 100 g / L is fed into the reaction vessel at a rate of 1 L / h. The pH of the liquid in the reaction vessel is maintained at 12, and the ammonia concentration is 12 / L, until a nickel-cobalt-manganese niobium-doped shell is grown on the outside of the outermost nickel-cobalt-manganese shell layer.

[0094] Example 4

[0095] This embodiment provides a precursor material containing a niobium-doped shell. Except that the thickness of the niobium-doped shell in the stacked shells first decreases and then increases along the direction away from the nickel-cobalt-manganese core, that is, along the direction away from the nickel-cobalt-manganese core, the thickness of the niobium-doped shell in the first stacked shell is 1.5 μm, the thickness of the niobium-doped shell in the second stacked shell is 1 μm, the thickness of the niobium-doped shell in the third stacked shell is 0.5 μm, and the thickness of the niobium-doped shell in the fourth stacked shell is 2 μm, the other properties are the same as in Embodiment 3.

[0096] Example 5

[0097] This embodiment provides a precursor material containing a niobium-doped shell. Except that the thickness of the niobium-doped shell in the stacked shell decreases sequentially along the direction away from the nickel-cobalt-manganese core, that is, along the direction away from the nickel-cobalt-manganese core, the thickness of the niobium-doped shell in the first stacked shell is 2 μm, the thickness of the niobium-doped shell in the second stacked shell is 1.5 μm, the thickness of the niobium-doped shell in the third stacked shell is 1 μm, and the thickness of the niobium-doped shell in the fourth stacked shell is 0.5 μm, the other properties are the same as in Embodiment 3.

[0098] Example 6

[0099] This embodiment provides a precursor material containing a niobium-doped shell. Except that the thickness of the nickel-cobalt-manganese shell in the stacked shell first increases and then decreases along the direction away from the nickel-cobalt-manganese core, that is, along the direction away from the nickel-cobalt-manganese core, the thickness of the nickel-cobalt-manganese shell in the first stacked shell is 0.5 μm, the thickness of the nickel-cobalt-manganese shell in the second stacked shell is 2 μm, the thickness of the nickel-cobalt-manganese shell in the third stacked shell is 1.5 μm, and the thickness of the nickel-cobalt-manganese shell in the fourth stacked shell is 1 μm, the other properties are the same as in Embodiment 3.

[0100] Example 7

[0101] This embodiment provides a precursor material containing a niobium-doped shell. Except that the thickness of the nickel-cobalt-manganese shell in the stacked shell increases sequentially along the direction away from the nickel-cobalt-manganese core, that is, along the direction away from the nickel-cobalt-manganese core, the thickness of the nickel-cobalt-manganese shell in the first stacked shell is 0.5 μm, the thickness of the nickel-cobalt-manganese shell in the second stacked shell is 1 μm, the thickness of the nickel-cobalt-manganese shell in the third stacked shell is 1.5 μm, and the thickness of the nickel-cobalt-manganese shell in the fourth stacked shell is 2 μm, the other properties are the same as in Embodiment 3.

[0102] Example 8

[0103] This embodiment provides a precursor material containing a niobium-doped shell, which is the same as in Example 1 except that the thickness of the nickel-cobalt-manganese niobium-doped shell is 0.4 μm.

[0104] Comparative Example 1

[0105] This comparative example provides a precursor material containing a niobium-doped shell. Except for omitting the first and second stacked shell layers sequentially covering the nickel-cobalt-manganese core, thereby increasing the D50 particle size of the nickel-cobalt-manganese core, and keeping the thickness of the niobium-doped shell unchanged, thus keeping the D50 particle size of the precursor material unchanged, everything else is the same as in Example 1.

[0106] Comparative Example 2

[0107] This comparative example provides a precursor material containing a niobium-doped shell. Except for omitting the nickel-cobalt-manganese niobium-doped shell covering the outermost layer of the stacked shell, which increases the D50 particle size of the nickel-cobalt-manganese core, and keeping the thickness of the first and second stacked shells that sequentially cover the nickel-cobalt-manganese core unchanged, thus keeping the D50 particle size of the precursor material unchanged, everything else is the same as in Example 1.

[0108] Comparative Example 3

[0109] This comparative example provides a precursor material that is identical to Example 1, except that the first and second stacked shell layers and the niobium-doped shell layer sequentially covering the nickel-cobalt-manganese core are omitted, thereby increasing the D50 particle size of the nickel-cobalt-manganese core and keeping the D50 particle size of the precursor material unchanged.

[0110] The precursor materials provided in the above embodiments and comparative examples were mixed with lithium carbonate and sintered at 400°C for 360 min to prepare the cathode material.

[0111] The positive electrode sheet was prepared using the obtained positive electrode material: The obtained positive electrode material, conductive carbon black SP (TIMCAL) and polyvinylidene fluoride PVDF (HSV900) were mixed in a mass ratio of 90:5:5, with N-methylpyrrolidone as the solvent. The mixture was stirred into a slurry, and the slurry was uniformly coated onto aluminum foil using a doctor blade with a coating gap of 100 μm. After coating, the foil was first dried by blowing air, then rolled and cut into circular electrode sheets, and then vacuum dried at 120°C. The weight of the electrode sheets was then measured to obtain the positive electrode sheet of the button half-cell. The negative electrode was a lithium metal sheet, the separator was a PP microporous membrane, and the electrolyte was a basic lithium battery electrolyte. The positive electrode sheet, lithium metal sheet, separator and electrolyte were assembled to obtain a button cell.

[0112] The obtained battery was subjected to a stability test. The stability test method was as follows: the capacity retention rate of the battery after 100 cycles at 25°C was obtained as shown in Table 1.

[0113] Table 1

[0114]

[0115] From Table 1, we can obtain:

[0116] (1) The batteries prepared using the precursor materials containing niobium-doped shells provided in Examples 1 to 3 have excellent cycle performance;

[0117] (2) By comparing Example 1 with Examples 4 and 5, it can be seen that in the present invention, the thickness variation of the nickel-cobalt-manganese-niobium-doped shell layer in the stacked shell layer along the direction away from the nickel-cobalt-manganese core will affect the performance of the precursor material, thereby affecting the performance of the battery. When the thickness of the nickel-cobalt-manganese-niobium-doped shell layer in the stacked shell layer first decreases and then increases along the direction away from the nickel-cobalt-manganese core, or when the thickness of the nickel-cobalt-manganese-niobium-doped shell layer in the stacked shell layer decreases sequentially along the direction away from the nickel-cobalt-manganese core, the capacity retention rate of the battery will deteriorate. This is due to the uneven diffusion of niobium during the sintering preparation of the cathode material.

[0118] (3) By comparing Example 1 with Examples 6 and 7, it can be seen that in the present invention, the change in the thickness of the nickel-cobalt-manganese shell layer in the stacked shell layer along the direction away from the nickel-cobalt-manganese core will affect the performance of the precursor material, thereby affecting the performance of the battery. When the thickness of the nickel-cobalt-manganese shell layer in the stacked shell layer first increases and then decreases along the direction away from the nickel-cobalt-manganese core, or when the thickness of the nickel-cobalt-manganese shell layer in the stacked shell layer increases sequentially along the direction away from the nickel-cobalt-manganese core, it will lead to the capacity retention rate of the battery. This is also due to the uneven diffusion of niobium during the sintering preparation of the cathode material.

[0119] (4) By comparing Example 1 and Example 8, it can be seen that the thickness of the nickel-cobalt-manganese niobium-doped shell in the present invention will affect the performance of the precursor material, thereby affecting the performance of the battery. When the thickness of the nickel-cobalt-manganese niobium-doped shell is too small, the capacity retention rate of the battery will be worse. This is because the niobium-doped shell is too thin and cannot play a protective role, and the battery stability is not significantly improved.

[0120] (5) As can be seen from the comparison between Example 1 and Comparative Examples 1 to 3, the precursor material provided by the present invention adopts a multi-layer niobium-doped shell, which makes the solid-phase diffusion of niobium more uniform during sintering, thereby achieving the purpose of uniform niobium doping in the cathode material, improving the stability of the cathode material and increasing conductivity; secondly, the precursor material provided by the present application uses the same element for doping and coating, which can improve the layering phenomenon of the cathode material after sintering to a certain extent; in addition, the precursor material provided by the present application has a multi-shell structure inside, which is beneficial to prevent cracks from propagating from the inside to the outside and improve the morphology and performance of large-particle-size ternary precursors.

[0121] 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 precursor material comprising a niobium-doped shell, characterized in that, The precursor material includes a nickel-cobalt-manganese core, an intermediate cladding layer, and a nickel-cobalt-manganese niobium-doped outer shell. The intermediate cladding layer includes at least four sets of stacked shells, each stacked shell including a niobium-doped nickel-cobalt-manganese shell and a nickel-cobalt-manganese shell, wherein the niobium-doped nickel-cobalt-manganese shell in each stacked shell is close to the nickel-cobalt-manganese core, and the nickel-cobalt-manganese shell is far from the nickel-cobalt-manganese core. Along the direction away from the nickel-cobalt-manganese core, the thickness of the niobium-doped nickel-cobalt-manganese shells in the stacked shells increases sequentially. Along the direction away from the nickel-cobalt-manganese core, the thickness of the nickel-cobalt-manganese shells in the stacked shells decreases sequentially. The thickness of the nickel-cobalt-manganese-doped niobium shell is not less than 0.5 μm.

2. The precursor material according to claim 1, characterized in that, The D50 particle size of the nickel-cobalt-manganese core is 3–7 μm.

3. The precursor material according to claim 1, characterized in that, The thickness of the nickel-cobalt-manganese-niobium-doped shells in the stacked shells is independently 0.01–5 μm.

4. The precursor material according to claim 1, characterized in that, The thickness of the nickel-cobalt-manganese shell in the stacked shell is independently 0.01–5 μm.

5. The precursor material according to claim 1, characterized in that, The thickness of the nickel-cobalt-manganese niobium-doped shell is greater than the thickness of the nickel-cobalt-manganese niobium-doped shell in all the stacked shell layers.

6. The precursor material according to any one of claims 1 to 5, characterized in that, The D50 particle size of the precursor material is not less than 7 μm.

7. A method for preparing the precursor material according to any one of claims 1 to 6, characterized in that, The preparation method includes: (1) Add a mixed solution containing nickel salt, cobalt salt and manganese salt to the bottom solution, and simultaneously add precipitant and complexing agent until nickel-cobalt-manganese core is obtained; (2) Keep the mixed solution, precipitant and complexing agent continuously introduced, and introduce niobium source solution until the nickel cobalt manganese core obtained in step (1) grows to obtain a nickel cobalt manganese niobium-doped shell. (3) Keep the mixed solution, precipitant and complexing agent continuously flowing in, and stop the flow of niobium source solution until the nickel cobalt manganese niobium-doped shell obtained in step (2) grows on the outside to obtain a nickel cobalt manganese shell. (4) If only one layer of nickel cobalt manganese doped niobium shell and nickel cobalt manganese shell is prepared, then the preparation of nickel cobalt manganese doped niobium shell is started directly; if more than one layer of nickel cobalt manganese doped niobium shell and nickel cobalt manganese shell is prepared, then steps (2) and (3) are repeated at least once before the preparation of nickel cobalt manganese doped niobium shell is prepared. The method for preparing a nickel-cobalt-manganese niobium-doped shell is as follows: a mixed solution, a precipitant and a complexing agent are continuously introduced, and a niobium source solution is introduced until a nickel-cobalt-manganese niobium-doped shell is grown on the outside of the outermost nickel-cobalt-manganese shell layer.

8. The preparation method according to claim 7, characterized in that, The temperature of the base solution in step (1) is 50-70℃, the pH is 9-12, and the ammonia concentration is 4-10g / L.

9. The preparation method according to claim 7, characterized in that, The addition rate of the mixed solution in steps (1), (2), (3) and (4) is 4 to 40 L / h, respectively.

10. The preparation method according to claim 7, characterized in that, Steps (1), (2), (3) and (4) are all carried out in a reaction vessel. The pH of the liquid in the reaction vessel in steps (1), (2), (3) and (4) is maintained at 9 to 12 and the ammonia concentration is 4 to 12 g / L.

11. The preparation method according to claim 7, characterized in that, The concentrations of the niobium source solutions in steps (2) and (4) are independently 0.1–100 g / L.

12. The preparation method according to claim 7, characterized in that, The niobium source solution introduced in steps (2) and (4) is introduced at a rate of 1 to 10 L / h.

13. The preparation method according to claim 7, characterized in that, The preparation method includes: (1) Add a mixed solution containing nickel salt, cobalt salt and manganese salt to a reaction vessel containing a base liquid at a temperature of 50-70℃, pH of 9-12 and ammonia concentration of 4-10 g / L at a rate of 4-40 L / h, and simultaneously add a precipitant and a complexing agent, keeping the pH of the liquid in the reaction vessel at 9-12 and the ammonia concentration at 4-12 g / L, until a nickel-cobalt-manganese core is obtained; (2) The mixed solution is continuously fed into the reaction vessel at a rate of 4 to 40 L / h. The precipitant and complexing agent are simultaneously and continuously fed into the reaction vessel. A niobium source solution with a concentration of 0.1 to 100 g / L is fed into the reaction vessel at a rate of 1 to 10 L / h. The pH of the liquid in the reaction vessel is maintained at 9 to 12 and the ammonia concentration is maintained at 4 to 12 / L until a niobium-cobalt-manganese shell is grown on the outside of the nickel-cobalt-manganese core obtained in step (1). (3) The mixed solution is continuously fed into the reaction vessel at a rate of 4 to 40 L / h. The precipitant and complexing agent are continuously fed into the reaction vessel simultaneously, and the niobium source solution is stopped. The pH of the liquid in the reaction vessel is kept at 9 to 12 and the ammonia concentration is kept at 4 to 12 / L until the nickel cobalt manganese niobium-doped shell obtained in step (2) is grown on the outside to obtain the nickel cobalt manganese shell. (4) If only one layer of nickel cobalt manganese doped niobium shell and nickel cobalt manganese shell is prepared, then the preparation of nickel cobalt manganese doped niobium shell is started directly; if more than one layer of nickel cobalt manganese doped niobium shell and nickel cobalt manganese shell is prepared, then steps (2) and (3) are repeated at least once before the preparation of nickel cobalt manganese doped niobium shell is prepared. The method for preparing a nickel-cobalt-manganese niobium-doped shell is as follows: a mixed solution is continuously fed into the reaction vessel at a rate of 4–40 L / h, a precipitant and a complexing agent are simultaneously and continuously fed into the reaction vessel, a niobium source solution with a concentration of 0.1–100 g / L is fed into the reaction vessel at a rate of 1–10 L / h, the pH of the liquid in the reaction vessel is maintained at 9–12, and the ammonia concentration is maintained at 4–12 g / L, until a nickel-cobalt-manganese niobium-doped shell is grown on the outside of the outermost nickel-cobalt-manganese shell layer.

14. A positive electrode material, characterized in that, The cathode material is prepared by sintering the precursor material as described in any one of claims 1 to 6.

15. A battery, characterized in that, The battery comprises the positive electrode material as described in claim 14.

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