A ternary precursor material doped with aluminum and molybdenum, and a preparation method and use thereof

Abstract

The present application relates to a kind of ternary precursor material doped with aluminum and molybdenum and its preparation method and purposes, the preparation method includes the following steps: (1) with metal salt solution, aluminum salt solution, molybdenum salt solution, precipitant solution and complexing agent solution as raw material, respectively independently with the first flow rate into to the bottom liquid, carry out coprecipitation reaction;(2) when the average particle size of product reaches the first target particle size, the first flow rate of all raw materials is respectively independently changed into second flow rate;(3) when the average particle size of product reaches the second target particle size, the flow rate of the aluminum salt solution and the molybdenum salt solution is changed into third flow rate, until the average particle size of product reaches the third target particle size, stop feeding raw material, obtain ternary precursor material doped with aluminum and molybdenum;The present application is prepared by controlling the flow rate of raw material several times, and the ternary precursor material with core-shell structure is prepared, which significantly improves the energy density and cycle life of battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery materials technology, and in particular to a ternary precursor material doped with aluminum and molybdenum, its preparation method, and its uses. Background Technology

[0002] Lithium-ion batteries, as an environmentally friendly new energy source, have been widely used in digital products, electric vehicles and energy storage. Among them, the positive electrode material plays a crucial role in battery performance. Currently, high-energy-density 8-series and 9-series ternary precursors have high nickel content and high energy density, but poor stability, and the precursors are prone to cracking during the preparation process.

[0003] To improve the defects in the aforementioned materials, bulk doping and surface coating of the precursor are simple and feasible improvement strategies. Doping elements can enhance the structural stability of the material to a certain extent, while surface coating can inhibit crack propagation, prevent the battery structure from collapsing during charging and discharging, and effectively prevent the electrolyte from corroding the cathode material. However, in the specific preparation process, there are problems such as uneven element doping and coating, complex processes, and low doping element content.

[0004] Doping ternary precursors with Al can improve material stability, mitigate cation mixing in high-nickel materials, reduce lattice distortion, and inhibit the precipitation of nickel and manganese ions from the material's interior, thereby enhancing the material's cycle performance. Furthermore, studies have shown that coating the surface of ternary precursors with Mo helps reduce Li / Ni mixing during sintering, decreasing the disorder of both ions after sintering. Additionally, Mo doping expands lithium-ion diffusion channels, facilitating solid-phase diffusion of lithium during sintering.

[0005] CN117430173A describes the preparation of a ternary precursor with an Al concentration gradient, which is then mixed with an Al source and a Li source and calcined to prepare a cathode material. This method effectively solves the problem of uneven diffusion of aluminum solid phase during sintering by gradient doping of aluminum and mixing with an aluminum source before sintering. However, after ball milling and mixing the precursor with the Al source, the degree of Al coating on the precursor surface is not high, and the diffusion effect of Li element after Al coating is not ideal.

[0006] The precursor prepared by CN115340133A relies on the synergistic effect of Mo and additives to uniformly add Mo into the precursor, ensuring the consistency of the precursor during mass production. However, this increases the production cost of the precursor, and the additives have requirements on the primary grain size, making the growth process relatively complex.

[0007] Therefore, how to provide a ternary precursor material with uniform element doping, stable material structure and performance, and low production cost, as well as its preparation method and lithium-ion battery with excellent cycle stability, has become an urgent problem to be solved. Summary of the Invention

[0008] To address the aforementioned technical problems, the present invention aims to provide an aluminum- and molybdenum-doped ternary precursor material, its preparation method, and its applications. The preparation method of the aluminum- and molybdenum-doped ternary precursor material of the present invention is simple, rapid, and highly efficient. Simultaneously, the obtained ternary precursor material combines the advantages of both aluminum and molybdenum doping, significantly improving the stability of the cathode material, increasing the battery's operating voltage and energy density, and the introduced core-shell structure can improve the battery's rate performance, effectively prevent crack propagation, and effectively inhibit electrolyte corrosion of the cathode material, thereby extending the lifespan of the lithium-ion battery.

[0009] To achieve this objective, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a method for preparing a ternary precursor material doped with aluminum and molybdenum, the method comprising the following steps:

[0011] (1) Using metal salt solution, aluminum salt solution, molybdenum salt solution, precipitant solution and complexing agent solution as raw materials, they are independently introduced into the bottom liquid at their respective first flow rates to carry out co-precipitation reaction;

[0012] (2) When the average particle size of the product reaches the first target particle size, the first flow rate of all raw materials independently changes to the second flow rate;

[0013] (3) When the average particle size of the product reaches the second target particle size, the flow rate of the aluminum salt solution and the molybdenum salt solution is changed to the third flow rate until the average particle size of the product reaches the third target particle size. Then the raw material is stopped to obtain the ternary precursor material doped with aluminum and molybdenum.

[0014] The metal salt solution includes nickel salt, cobalt salt, and manganese salt.

[0015] The method for preparing aluminum- and molybdenum-doped ternary precursor materials provided by this invention ensures that the precursor is grown and formed in one step and that the doping elements are evenly distributed in the inner and outer layers of the particles by repeatedly adjusting the flow rate of the raw materials added during the co-precipitation reaction. This ensures that small particles do not explode during the growth process. The flow rate of the aluminum salt solution is proportional to the average particle size of the product and should be fed separately, which is more conducive to the uniform distribution of aluminum elements.

[0016] This preparation method is simple, quick, and highly efficient. It is compatible with existing process equipment and improves material performance while reducing manufacturing costs.

[0017] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. The technical objectives and beneficial effects of the present invention can be better achieved and realized through the following preferred technical solutions.

[0018] In some embodiments, the first flow rate of the metal salt solution is 5 L / h-80 L / h, for example, it can be 5 L / h, 10 L / h, 20 L / h, 30 L / h, 40 L / h, 50 L / h, 60 L / h, 70 L / h or 80 L / h, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0019] The flow rate in this invention can be adjusted according to the size of the reactor.

[0020] In some embodiments, the first flow rate of the aluminum salt solution is 0.1 L / h to 10 L / h, for example, it can be 0.1 L / h, 0.5 L / h, 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 is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0021] In some embodiments, the first flow rate of the molybdenum salt solution is 0.1 L / h to 10 L / h, for example, it can be 0.1 L / h, 0.5 L / h, 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 is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0022] In some embodiments, the first flow rate of the precipitant solution is 0.1 L / h to 40 L / h, for example, it can be 0.1 L / h, 1 L / h, 5 L / h, 10 L / h, 15 L / h, 20 L / h, 25 L / h, 30 L / h, 35 L / h or 40 L / h, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0023] In some embodiments, the first flow rate of the complexing agent solution is 0.1 L / h to 20 L / h, for example, it can be 0.1 L / h, 1 L / h, 2 L / h, 5 L / h, 8 L / h, 10 L / h, 12 L / h, 15 L / h, 18 L / h or 20 L / h, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0024] In some embodiments, the third flow rate is 50L / h-60L / h, for example, it can be 50L / h, 52L / h, 55L / h, 58L / h or 60L / h, but it is not limited to the recited values, and other unrecited values within the numerical range are also applicable.

[0025] In some embodiments, the ratio of the first flow rate of the metal salt solution to the first flow rate of the precipitant solution is 2.5-3.5, for example, it can be 2.5, 2.6, 2.8, 3.0, 3.2, 3.4 or 3.5, but it is not limited to the recited values, and other unrecited values within the numerical range are also applicable.

[0026] In some embodiments, the ratio of the first flow rate of the precipitant solution to the first flow rate of the complexing agent solution is 3-7, for example, it can be 3, 3.5, 4, 4.5, 5, 5.5, 6, 6.5 or 7, but it is not limited to the recited values, and other unrecited values within the numerical range are also applicable.

[0027] In some embodiments, the molar ratio of Ni:Co:Mn in the metal salt solution is (1-a-b):a:b, wherein 0<a<1, 0<b<1, 0<a+b<1. For example, a can be 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 0.95, but it is not limited to the recited values, and other unrecited values within the numerical range are also applicable; for example, b can be 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 or 0.95, but it is not limited to the recited values, and other unrecited values within the numerical range are also applicable.

[0028] In some embodiments, the total molar concentration of Ni, Co and Mn in the metal salt solution is 1mol / L-4mol / L, for example, it can be 1mol / L, 1.5mol / L, 2mol / L, 2.5mol / L, 3mol / L, 3.5mol / L or 4mol / L, but it is not limited to the recited values, and other unrecited values within the numerical range are also applicable.

[0029] In some embodiments, the concentration of the aluminum salt solution is 200mg / L-600mg / L, for example, it can be 200mg / L, 250mg / L, 300mg / L, 350mg / L, 400mg / L, 450mg / L, 500mg / L, 550mg / L or 600mg / L, but it is not limited to the recited values, and other unrecited values within the numerical range are also applicable.

[0030] In some embodiments, the concentration of the molybdenum salt solution is 600 mg / L to 1000 mg / L, for example, it can be 600 mg / L, 650 mg / L, 700 mg / L, 750 mg / L, 800 mg / L, 850 mg / L, 900 mg / L, 950 mg / L or 1000 mg / L, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0031] This invention further controls the concentration of the molybdenum salt solution to 600 mg / L-1000 mg / L. If the concentration of the molybdenum salt solution is too high, doping becomes difficult, especially during the later growth process, and small particles are easily formed. If the concentration of the molybdenum salt solution is too low, the doping amount is insufficient, and the performance improvement is not significant.

[0032] In some embodiments, the aluminum salt solution includes aluminum nitrate solution and / or aluminum sulfate solution.

[0033] In some embodiments, the molybdenum salt solution includes a molybdenum nitrate solution and / or a molybdenum sulfate solution.

[0034] In some embodiments, the second flow rate of each raw material in step (2) is independently 1.2 to 3 times the first flow rate, for example, it can be 1.2 times, 1.5 times, 1.8 times, 2.0 times, 2.2 times, 2.5 times, 2.8 times or 3 times, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] This invention further controls the second flow rate of each raw material to be 1.2 to 3 times the first flow rate. Increasing the flow rate is to ensure the growth rate. If the second flow rate is too high, hollow rings may appear inside the precursor. If the second flow rate is too low, solid rings may appear.

[0036] In some embodiments, the first target particle size is 1μm-2μm, for example, it can be 1μm, 1.2μm, 1.5μm, 1.6μm, 1.8μm or 2μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] This invention further controls the first target particle size to 1μm-2μm. Before the formation of the first target particle size, there is a nucleation stage, and the precursor spheres in the nucleation stage are generally relatively loose. If the first target particle size is too large, it will seriously affect the performance of the precursor.

[0038] In some embodiments, the base liquid includes ammonia and sodium hydroxide.

[0039] In some embodiments, the mass concentration of ammonia in the base solution is 4 g / L-8 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 or 8 g / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0040] In some embodiments, the pH of the substrate is 9.5-11.5, for example, it can be 9.5, 10, 10.5, 11 or 11.5, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0041] In some embodiments, the precipitant solution comprises a sodium hydroxide solution and / or a potassium hydroxide solution.

[0042] In some embodiments, the mass fraction of the precipitant solution is 5wt%-50wt%, for example, it can be 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, or 50wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] In some embodiments, the complexing agent solution comprises ammonia and / or ammonium salts.

[0044] In some embodiments, the ammonium salt includes ammonium bicarbonate and / or ammonium carbonate.

[0045] In some embodiments, the complexing agent solution has a mass fraction of 5wt%-50wt%, for example, it may be 5wt%, 10wt%, 15wt%, 20wt%, 25wt%, 30wt%, 35wt%, 40wt%, 45wt%, or 50wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0046] In some embodiments, the nickel salt, cobalt salt, and manganese salt each independently comprise sulfate and / or nitrate.

[0047] In some embodiments, the nickel salt comprises nickel nitrate and / or nickel sulfate.

[0048] In some embodiments, the cobalt salt includes cobalt nitrate and / or cobalt sulfate.

[0049] In some embodiments, the manganese salt includes manganese nitrate and / or manganese sulfate.

[0050] In some embodiments, the temperature of the coprecipitation reaction is 40°C-70°C, for example, 40°C, 45°C, 50°C, 55°C, 60°C, 65°C or 70°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0051] In some embodiments, the pH of the coprecipitation reaction is 10-12, for example, 10, 10.5, 11, 11.5 or 12, but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0052] In some embodiments, the second target particle size is 12μm-14μm, for example, it can be 12μm, 12.5μm, 13μm, 13.5μm, 13.8μm or 14μm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0053] In some embodiments, the third target particle size is 14μm-20μm, for example, it can be 15μm, 16μm, 17μm, 18μm, 19μm or 20μm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0054] As a preferred embodiment of the preparation method of the present invention, the preparation method includes the following steps:

[0055] (1) Mix and dissolve nickel salt, cobalt salt and manganese salt in water to obtain metal salt solution; pass all raw materials of metal salt solution, aluminum salt solution, molybdenum salt solution, precipitant solution and complexing agent solution into bottom liquid at flow rates of 5L / h-80L / h, 0.1L / h-10L / h, 0.1L / h-10L / h, 0.1L / h-40L / h and 0.1L / h-20L / h respectively, adjust the pH of coprecipitation reaction to 10-12, and carry out coprecipitation reaction;

[0056] (2) When the average particle size of the product reaches 1μm-2μm, the first flow rate of all raw materials is independently changed to the second flow rate, and the second flow rate is independently 5L / h-10L / h higher than their respective first flow rates.

[0057] (3) When the average particle size of the product reaches 12μm-14μm, the flow rate of the aluminum salt solution and the molybdenum salt solution is changed to 50L / h-60L / h until the average particle size of the product reaches 15μm-20μm. Then the raw material is stopped to obtain the ternary precursor material doped with aluminum and molybdenum.

[0058] In a second aspect, the present invention provides a ternary precursor material doped with aluminum and molybdenum, wherein the ternary precursor material doped with aluminum and molybdenum is prepared according to the preparation method described in the first aspect.

[0059] The aluminum and molybdenum doped ternary precursor material has a core-shell structure, wherein the chemical general formula of the core is Ni x Co y Mn z Al w (OH)2, wherein 0.8≤x≤0.98, 0<y≤0.1, 0<z≤0.1, 0.005≤w≤0.02, and x+y+z+w=1;

[0060] the chemical general formula of the shell is Ni x Co y Mn z Mo m (OH)2, wherein 0.8≤x≤0.98, 0<y≤0.1, 0<z≤0.1, 0.005≤m≤0.02, and x+y+z+m=1; the thickness of the shell is 0.1μm-3μm.

[0061] The aluminum and molybdenum doped ternary precursor material provided by the present invention has a core-shell structure, which alleviates the stress accumulation phenomenon of the positive electrode material caused by the volume change of internal unit cells; aluminum doping can improve the cation mixing phenomenon in the positive electrode material, reduce the lattice distortion phenomenon, inhibit the precipitation of nickel ions and manganese ions from the interior of the material, and effectively ensure the structural integrity of the precursor, so as to improve the cycling performance of the material; molybdenum element doping can improve the diffusion efficiency of lithium element during sintering, thereby improving the comprehensive performance of the positive electrode material.

[0062] In a third aspect, the present invention provides a positive electrode material, which is prepared by using the aluminum and molybdenum doped ternary precursor material described in the second aspect.

[0063] In a fourth aspect, the present invention provides a lithium ion battery, which comprises the positive electrode material described in the third aspect.

[0064] The lithium ion battery provided by the present invention has higher working voltage and energy density, and longer cycling life.

[0065] The numerical ranges described in the present invention not only include the above-listed point values, but also include any point values between the above numerical ranges that are not listed. For the limitation of length and the sake of conciseness, the present invention will not exhaustively list the specific point values included in the ranges.

[0066] Compared with the prior art, the present invention has at least the following beneficial effects:

[0067] (1) The preparation method of aluminum- and molybdenum-doped ternary precursor materials provided by the present invention ensures that the precursor is grown and formed in one step in the reaction system and that the doping elements are evenly distributed in the inner and outer layers of the particles by repeatedly adjusting the flow rate of the raw materials added during the co-precipitation reaction. This ensures that small particles do not burst during the growth process. The flow rate of the aluminum salt solution is proportional to the average particle size of the product and should be fed separately, which is more conducive to the uniform distribution of aluminum elements. The preparation method is simple, fast and efficient, and can be well compatible with existing process equipment. It improves the material performance while reducing the manufacturing cost.

[0068] (2) The aluminum- and molybdenum-doped ternary precursor material provided by the present invention has a core-shell structure, which alleviates the stress accumulation phenomenon caused by the change of internal cell volume in the cathode material; aluminum doping can improve the cation mixing phenomenon in the cathode material, weaken the lattice distortion phenomenon, and inhibit the precipitation of nickel ions and manganese ions from the inside of the material, effectively ensuring the integrity of the precursor structure, thereby improving the cycle performance of the material; molybdenum doping can improve the diffusion efficiency of lithium elements in the sintering process, thereby improving the comprehensive performance of the cathode material.

[0069] (3) The lithium-ion battery provided by the present invention has higher operating voltage and energy density, and longer cycle life. Detailed Implementation

[0070] 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.

[0071] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0072] Unless otherwise specified, all reagents and consumables used in the following examples and comparative examples were purchased from conventional reagent manufacturers in the art; unless otherwise specified, the experimental methods and techniques used were conventional methods and techniques in the art.

[0073] Example 1

[0074] This embodiment provides a ternary precursor material doped with aluminum and molybdenum. The ternary precursor material has a core-shell structure, wherein the core has the chemical formula Ni. 0.89 Co 0.06 Mn 0.04 Al 0.01(OH)2, the chemical formula of the shell is Ni 0.89 Co 0.06 Mn 0.04 Mo 0.01 (OH)2, the shell thickness is 1μm;

[0075] The preparation method of the aluminum- and molybdenum-doped ternary precursor material provided in this embodiment includes the following steps:

[0076] (1) Nickel nitrate, cobalt nitrate and manganese nitrate are mixed and dissolved in water to obtain a metal salt solution; the metal salt solution, aluminum nitrate solution, molybdenum nitrate solution, sodium hydroxide solution and ammonia water are passed into the bottom liquid at flow rates of 30 L / h, 3 L / h, 3 L / h, 10 L / h and 15 L / h respectively, and the pH of the coprecipitation reaction is adjusted to 11 to carry out the coprecipitation reaction;

[0077] The concentrations of aluminum nitrate solution and molybdenum nitrate solution in the metal salt solution were 400 mg / L and 500 mg / L, respectively. The pH of the base solution was 11, the mass fraction of sodium hydroxide solution was 30 wt%, and the mass fraction of ammonia solution was 35 wt%.

[0078] (2) When the average particle size of the product reaches 1.5 μm, the first flow rate of all raw materials is independently changed to the second flow rate, and the second flow rate is independently twice the first flow rate.

[0079] (3) When the average particle size of the product reaches 13 μm, the flow rate of aluminum nitrate solution and molybdenum nitrate solution is changed to 55 L / h until the average particle size of the product reaches 20 μm. Then the raw material is stopped to obtain the ternary precursor material doped with aluminum and molybdenum.

[0080] Example 2

[0081] This embodiment provides a ternary precursor material doped with aluminum and molybdenum. The ternary precursor material has a core-shell structure, wherein the core has the chemical formula Ni. 0.895 Co 0.06 Mn 0.04 Al 0.005 (OH)2, the chemical formula of the shell is Ni 0.888 Co 0.06 Mn 0.04 Mo 0.012 (OH)2, with a shell thickness of 0.5 μm;

[0082] The preparation method of the aluminum- and molybdenum-doped ternary precursor material provided in this embodiment includes the following steps:

[0083] (1) Nickel sulfate, cobalt sulfate and manganese sulfate are mixed and dissolved in water to obtain a metal salt solution; the metal salt solution, aluminum nitrate solution, molybdenum nitrate solution, potassium hydroxide and ammonium bicarbonate are introduced into the bottom liquid at flow rates of 5 L / h, 1 L / h, 1 L / h, 2 L / h and 5 L / h respectively, and the pH of the coprecipitation reaction is adjusted to 10 to carry out the coprecipitation reaction;

[0084] The concentrations of aluminum nitrate solution and molybdenum nitrate solution in the metal salt solution were 200 mg / L and 600 mg / L, respectively. The pH of the bottom solution was 10, the mass fraction of potassium hydroxide was 5 wt%, and the mass fraction of ammonium bicarbonate was 5 wt%.

[0085] (2) When the average particle size of the product reaches 1 μm, the first flow rate of all raw materials is independently changed to the second flow rate, and the second flow rate is independently 1.2 times the first flow rate;

[0086] (3) When the average particle size of the product reaches 12 μm, the flow rate of aluminum nitrate solution and molybdenum nitrate solution is changed to 50 L / h until the average particle size of the product reaches 15 μm. Then the raw material is stopped to obtain the ternary precursor material doped with aluminum and molybdenum.

[0087] Example 3

[0088] This embodiment provides a ternary precursor material doped with aluminum and molybdenum. The ternary precursor material has a core-shell structure, wherein the core has the chemical formula Ni. 0.885 Co 0.06 Mn 0.04 Al 0.015 (OH)2, the chemical formula of the shell is Ni 0.88 Co 0.06 Mn 0.04 Mo 0.02 (OH)2, with a shell thickness of 1.5 μm;

[0089] The preparation method of the aluminum- and molybdenum-doped ternary precursor material provided in this embodiment includes the following steps:

[0090] (1) Nickel nitrate, cobalt nitrate and manganese nitrate are mixed and dissolved in water to obtain a metal salt solution; the metal salt solution, aluminum nitrate solution, molybdenum nitrate solution, sodium hydroxide solution and ammonia water are passed into the bottom liquid at flow rates of 24 L / h, 8 L / h, 10 L / h, 20 L / h and 18 L / h respectively, and the pH of the coprecipitation reaction is adjusted to 12 to carry out the coprecipitation reaction;

[0091] The concentrations of the aluminum salt solution and the molybdenum salt solution in the metal salt solution were 600 mg / L and 1000 mg / L respectively. The pH of the base solution was 12, the mass fraction of the sodium hydroxide solution was 50 wt%, and the mass fraction of the ammonia solution was 50 wt%.

[0092] (2) When the average particle size of the product reaches 2 μm, the first flow rate of all raw materials is independently changed to the second flow rate, and the second flow rate is independently 2.5 times the first flow rate;

[0093] (3) When the average particle size of the product reaches 14 μm, the flow rate of the aluminum salt solution and the molybdenum salt solution is changed to 60 L / h until the average particle size of the product reaches 20 μm. Then the raw material is stopped to obtain the ternary precursor material doped with aluminum and molybdenum.

[0094] Example 4

[0095] This embodiment provides a ternary precursor material doped with aluminum and molybdenum. The only difference from Embodiment 1 is that when preparing the ternary precursor material doped with aluminum and molybdenum, the concentration of the molybdenum nitrate solution in step (1) is 300 mg / L, and the other steps remain unchanged.

[0096] Example 5

[0097] This embodiment provides a ternary precursor material doped with aluminum and molybdenum. The only difference from Embodiment 1 is that when preparing the ternary precursor material doped with aluminum and molybdenum, the concentration of the molybdenum nitrate solution in step (1) is 1500 mg / L, and the other steps remain unchanged.

[0098] Example 6

[0099] This embodiment provides a ternary precursor material doped with aluminum and molybdenum. The only difference from Embodiment 1 is that, in preparing the ternary precursor material doped with aluminum and molybdenum, the second flow rate of each raw material in step (2) is independently 5 L / h lower than its respective first flow rate, while the other steps remain unchanged.

[0100] Example 7

[0101] This embodiment provides a ternary precursor material doped with aluminum and molybdenum. The only difference from Embodiment 1 is that, in preparing the ternary precursor material doped with aluminum and molybdenum, the second flow rate of each raw material in step (2) is independently 15 L / h higher than its respective first flow rate, while the other steps remain unchanged.

[0102] Example 8

[0103] This embodiment provides a ternary precursor material doped with aluminum and molybdenum. The only difference from Embodiment 1 is that when preparing the ternary precursor material doped with aluminum and molybdenum, the first target particle size in step (2) is 0.5 μm, and the other steps remain unchanged.

[0104] Example 9

[0105] This embodiment provides a ternary precursor material doped with aluminum and molybdenum. The only difference from Embodiment 1 is that when preparing the ternary precursor material doped with aluminum and molybdenum, the first target particle size in step (2) is 5 μm, and the other steps remain unchanged.

[0106] Comparative Example 1

[0107] This comparative example provides a ternary precursor material doped with aluminum and molybdenum. The only difference from Example 1 is that, in preparing this ternary precursor material doped with aluminum and molybdenum, the second flow rate in step (2) is the same as the first flow rate, and the third flow rate in step (3) is the same as the first flow rate. That is, no flow rate adjustment is performed, and the other steps remain unchanged.

[0108] Comparative Example 2

[0109] This comparative example provides an aluminum-doped ternary precursor material. The only difference from Example 1 is that molybdenum nitrate solution was not added in steps (1), (2) and (3) when preparing the aluminum-doped ternary precursor material, while the other steps remained unchanged.

[0110] test:

[0111] Cathode materials were prepared using the ternary precursor materials obtained in the examples and comparative examples, respectively. The preparation methods of the cathode materials include the following methods:

[0112] The ternary precursor materials prepared in the examples and comparative examples were mixed with lithium hydroxide at a mass ratio of 1:1.2 for 30 min, calcined at 500℃ for 4 h, calcined at 750℃ for 12 h, and cooled in the furnace to obtain the cathode material.

[0113] A positive electrode sheet is prepared using the above-mentioned positive electrode material, and the preparation method of the positive electrode sheet includes:

[0114] The positive electrode material, carbon black and PVDF are added to NMP in a mass ratio of 96:2:2 to prepare a uniform slurry. The slurry is coated on aluminum foil and dried at 80°C for 12 hours. The positive electrode sheet is obtained by rolling. The wide electrode sheet is cut into the width required for the battery to complete the electrode sheet manufacturing.

[0115] Using the aforementioned positive electrode as the positive electrode and graphite as the negative electrode, and 1 mol / L LiFP6 (volume ratio EC:DEC = 1:1 as solvent) as the electrolyte, lithium-ion batteries were assembled. The performance of the lithium-ion batteries was tested at room temperature under the following conditions: voltage range of 2.7V-4.4V and current density of 1C. The test results are shown in Table 1 below.

[0116] Table 1

[0117]

[0118] The test results show that:

[0119] (1) As can be seen from Examples 1-3, the present invention ensures that the precursor is grown and formed in one step and the doping elements are evenly distributed in the inner and outer layers of the particles by repeatedly controlling the flow rate of the raw materials added during the co-precipitation reaction. Aluminum doping can improve the cation mixing phenomenon in the cathode material, reduce the lattice distortion phenomenon, and inhibit the precipitation of nickel and manganese ions from the inside of the material, effectively ensuring the integrity of the precursor structure, thereby improving the cycle performance of the material. Molybdenum can expand the lattice spacing, ensuring the diffusion efficiency of lithium and the structural integrity of the material. At the same time, the core-shell structure can further alleviate the stress accumulation phenomenon caused by the change of internal cell volume in the cathode material. It significantly improves the working voltage, energy density and cycle life of lithium-ion batteries.

[0120] (2) By comparing Example 1 with Examples 4-5, it can be seen that the present invention further controls the concentration of molybdenum salt solution to 600mg / L-1000mg / L. If the concentration of molybdenum salt solution is too high, the doping is difficult, especially in the later growth process, small particles are easily formed; if the concentration of molybdenum salt solution is too low, the doping amount is insufficient and the performance improvement is not significant.

[0121] (3) By comparing Example 1 with Example 6-7, it can be seen that the present invention further controls the second flow rate of each raw material to be 1.2 times to 3 times the first flow rate. The flow rate is increased to ensure the growth rate. If the second flow rate is too large, hollow rings may appear inside the precursor. If the second flow rate is too small, solid rings may appear.

[0122] (4) By comparing Example 1 with Example 8-9, it can be seen that the present invention further improves the first target particle size by 1μm-2μm. Before the formation of the first target particle size, it is the nucleation stage. The precursor spheres in the nucleation stage are generally loose. If the first target particle size is too large, it will seriously affect the performance of the precursor.

[0123] (5) As can be seen from Example 1 and Comparative Example 1, by controlling the flow rate of the raw materials into the reaction base liquid during the co-precipitation reaction process, the present invention can ensure that the precursor is grown and formed in one step in the reaction system and that the doped elements are evenly distributed in the inner and outer layers of the particles, thus ensuring that small particles do not explode during the growth process, thereby improving the rate capability and long-cycle stability of the ternary precursor material.

[0124] (6) As can be seen from Example 1 and Comparative Example 2, the present invention can obtain more stable battery performance by simultaneously doping aluminum and molybdenum. However, when molybdenum is not doped, the rate performance and long-cycle stability of lithium-ion batteries decrease significantly.

[0125] In summary, this invention, by repeatedly controlling the flow rate of raw materials added during the co-precipitation reaction, ensures that the precursor is grown and formed in one step within the reaction system, and that the doping elements are uniformly distributed in the inner and outer layers of the particles. Aluminum doping can improve the cation mixing phenomenon in the cathode material, reduce lattice distortion, and inhibit the precipitation of nickel and manganese ions from the material interior, effectively ensuring the structural integrity of the precursor and thus improving the cycle performance of the material. Molybdenum can expand the lattice spacing, ensuring the diffusion efficiency of lithium and the structural integrity of the material. At the same time, the core-shell structure can further alleviate the stress accumulation phenomenon caused by the internal cell volume change of the cathode material. This significantly improves the operating voltage, energy density, and cycle life of the lithium-ion battery.

[0126] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a ternary precursor material doped with aluminum and molybdenum, characterized in that, The preparation method includes the following steps: (1) Using metal salt solution, aluminum salt solution, molybdenum salt solution, precipitant solution and complexing agent solution as raw materials, they are independently introduced into the bottom liquid at their respective first flow rates to carry out co-precipitation reaction; (2) When the average particle size of the product reaches the first target particle size, the first flow rate of all raw materials independently changes to the second flow rate; (3) When the average particle size of the product reaches the second target particle size, the flow rate of the aluminum salt solution and the molybdenum salt solution is changed to the third flow rate until the average particle size of the product reaches the third target particle size. Then the raw material is stopped to obtain the ternary precursor material doped with aluminum and molybdenum. The metal salt solution includes nickel salt, cobalt salt, and manganese salt.

2. The preparation method according to claim 1, characterized in that, The first flow rate of the metal salt solution in step (1) is 5 L / h-80 L / h; And / or, the first flow rate of the aluminum salt solution is 0.1 L / h-10 L / h; And / or, the first flow rate of the molybdenum salt solution is 0.1 L / h-10 L / h; And / or, the first flow rate of the precipitant solution is 0.1 L / h-40 L / h; And / or, the first flow rate of the complexing agent solution is 0.1 L / h-20 L / h; And / or, the third flow rate is 50 L / h - 60 L / h; And / or, the ratio of the first flow rate of the metal salt solution to the first flow rate of the precipitant solution is 2.5-3.5; And / or, the ratio of the first flow rate of the precipitant solution to the first flow rate of the complexing agent solution is 3-7.

3. The preparation method according to claim 1 or 2, characterized in that, In step (1), the molar ratio of Ni:Co:Mn in the metal salt solution is (1-ab):a:b, where 0 <a<1,0<b<1,0<a+b<1; And / or, the concentration of the aluminum salt solution is 200 mg / L-600 mg / L; And / or, the concentration of the molybdenum salt solution is 600 mg / L-1000 mg / L.

4. The preparation method according to any one of claims 1-3, characterized in that, The first target particle size is 1μm-2μm; And / or, in step (2), the second flow rate of each raw material is independently 1.2 to 3 times the first flow rate.

5. The preparation method according to any one of claims 1-4, characterized in that, The pH of the substrate solution in step (1) is 9.5-11.5; And / or, the precipitant solution includes sodium hydroxide solution and / or potassium hydroxide solution; And / or, the complexing agent solution comprises ammonia and / or ammonium salts.

6. The preparation method according to any one of claims 1-5, characterized in that, The temperature for the coprecipitation reaction is 40℃-70℃; And / or, the pH of the coprecipitation reaction is 10-12.

7. The preparation method according to any one of claims 1-6, characterized in that, Step (3) The second target particle size is 12μm-14μm; And / or, the third target particle size is 14μm-20μm.

8. A ternary precursor material doped with aluminum and molybdenum, characterized in that, The preparation method according to any one of claims 1-7 is used to prepare the following; The aluminum- and molybdenum-doped ternary precursor material has a core-shell structure, wherein the general chemical formula of the core is Ni x Co y Mn z Al w (OH)2, wherein 0.8≤x≤0.98, 0<y≤0.1, 0<z≤0.1, 0.005≤w≤0.02, and x+y+z+w=1; the general chemical formula of the shell is Ni x Co y Mn z Mo m (OH)2, wherein 0.8≤x≤0.98, 0<y≤0.1, 0<z≤0.1, 0.005≤m≤0.02, and x+y+z+m=1; The shell thickness is 0.1μm-3μm.

9. A positive electrode material, characterized in that, The cathode material is prepared using the ternary precursor material doped with aluminum and molybdenum as described in claim 8.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode material as described in claim 9.

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