Positive electrode precursor material of core-shell structure, preparation method therefor and use thereof

Abstract

A positive electrode precursor material of a core-shell structure, a preparation method therefor and a use thereof. The positive electrode precursor material of a core-shell structure comprises a first nickel-cobalt-manganese precursor core and a second nickel-cobalt-manganese precursor shell located on the surface of the precursor core. The positive electrode precursor material of a core-shell structure contains a doping element; the proportion of the molar weight of nickel in the first nickel-cobalt-manganese precursor core in the total molar weight of nickel-cobalt-manganese is greater than or equal to 80%, and the doping element exhibits a gradient increase in the part of the first nickel-cobalt-manganese precursor core close to the shell; and the proportion of the molar weight of manganese in the second nickel-cobalt-manganese precursor core in the total molar weight of the nickel-cobalt-manganese is greater than or equal to 45%. According to the precursor material, by taking a high-nickel material as the core, and a high-manganese material as the shell, and cooperating with gradient doping of the doping element, the capacity performance is optimized under the condition of ensuring the cycle performance of the material, thus improving the performance of the lithium ion positive electrode material.

Description

A core-shell structured cathode precursor material and its preparation method and application Technical Field

[0001] The present application relates to the technical field of lithium-ion batteries, for example, a core-shell structured positive electrode precursor material and its preparation method and application. Background Art

[0002] In recent years, the application areas of lithium-ion batteries have been continuously expanding, from traditional 3C products to current electric vehicles and smart grids. The new energy industry has an increasingly urgent demand for lithium-ion batteries, especially high-energy-density lithium batteries. To meet this demand, a lot of research work has been devoted to finding and developing electrode materials with high specific capacity.

[0003] Nickel-rich layered material LiNi 1-x-y Mn x Co y O2(x+y≤0.4)(NCM) is considered to be the most promising cathode candidate material. It has a capacity of 200mAh / g and a high voltage of 3.8V (vsLi+ / Li). However, Li + / Ni 2+ Problems such as cation mixing, Li residue, poor thermal stability, and pulverization limit the cycling and rate performance of batteries. To date, scientists have tried to improve the structural stability by using a variety of strategies, including element doping, surface coating, and forming concentration gradients.

[0004] CN110880591A provides a SiO2 coated lithium ion battery positive electrode precursor material and a preparation method thereof, comprising a core and a SiO2 coating layer at least partially coated on the surface of the core, wherein the chemical structure of the core is Ni x Co y M 1‐x‐y O, wherein M is selected from Mn or Al.

[0005] CN115092974A provides a doped ternary precursor and its preparation method, ternary positive electrode material and lithium ion battery. When the precursor is prepared, the synthesis conditions are adjusted to make part of the doping element M (selected from Mg 2+ 、Al 3+ 、Zr 4+ 、Ti 4+ 、Y 3+ 、Sr 2+ 、Nb 5+ 、W 6+ 、Mo 6+One or more) undergo heterogeneous co-precipitation, wherein the separately precipitated nano M hydroxide particles or the M hydroxide particles are mixed with one or more of nickel hydroxide, cobalt hydroxide, and manganese hydroxide, whose main component is M or entirely M, have extremely high surface energy and will be adsorbed on the surface of larger crystalline ternary hydroxide precursor grains; thereby obtaining a spherical secondary particle precursor agglomerated by two significantly different primary particles.

[0006] After modification, the lithium-ion battery cathode materials in the above-mentioned literature still have problems such as insufficient structural stability, insufficient rate performance, and easy shedding of the shell in the core-shell structure.

[0007] Therefore, how to improve the structural stability of lithium-ion positive electrode materials and thus improve their electrochemical performance is a technical problem that needs to be solved urgently.

[0008] Summary of the Invention

[0009] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0010] The present application provides a core-shell structured cathode precursor material, its preparation method, and application. The precursor material provided in the present application has a high-nickel material as the core and a high-manganese material as the shell, and is doped with a gradient of doping elements. This optimizes the capacity performance while ensuring the material's cycle performance. The core-shell structure is more tightly bonded, improving the stability of the core-shell structure cathode material, thereby improving the performance of the lithium-ion cathode material.

[0011] In a first aspect, the present application provides a core-shell structured cathode precursor material, the core-shell structured cathode precursor material comprising a first nickel-cobalt-manganese precursor core and a second nickel-cobalt-manganese precursor shell layer located on the surface of the precursor core;

[0012] In which, the core-shell structured positive electrode precursor material contains doping elements; the molar amount of nickel in the first nickel-cobalt-manganese precursor core accounts for ≥80% of the total molar amount of nickel-cobalt-manganese, for example, 80%, 83%, 85%, 88%, 90%, 93%, 95% or 98%, and the doping element increases gradually in the part of the first nickel-cobalt-manganese precursor core close to the shell; the molar amount of manganese in the second nickel-cobalt-manganese precursor core accounts for ≥45% of the total molar amount of nickel-cobalt-manganese, for example, 45%, 50%, 55%, 60% or 65%, etc.

[0013] The doping elements in this application are conventional doping processes, and the types of elements that can be used for precursor doping are applicable to this application. They can be selected according to actual needs, including but not limited to metal elements (tungsten, aluminum, magnesium, zirconium, calcium, etc.) or non-metallic elements (nitrogen or boron, etc.). Any combination and selection can be made according to actual needs.

[0014] The precursor material provided in the present application adopts a nickel-rich material with high energy density as the core and a high manganese material with high stability as the shell, and at the same time, gradient doping of the doping elements is coordinated, and gradient doping is performed in the core structure close to the shell (the doping amount in other positions of the core and the shell is not gradient doped). This can refine the size of the primary grains, enable the manganese-rich precursor to grow better on the surface of the core, and optimize the capacity performance while ensuring the cycle performance of the material. The gradient doping also makes the bond between the core and the shell tighter, and the shell is not easy to fall off, thereby improving the stability of the core-shell structure positive electrode material, thereby improving the performance of the lithium-ion positive electrode material.

[0015] In this application, gradient doping is only performed on the part of the core close to the shell. If the entire core-shell structure is gradient doped or the doping elements are uniformly distributed in the entire core-shell structure, the shell and the core cannot be tightly combined, making the shell easy to fall off.

[0016] In one embodiment, the total doping amount of the doping element is 1000-5000 ppm, for example, 1000 ppm, 1500 ppm, 2000 ppm, 2500 ppm, 3000 ppm, 3500 ppm, 4000 ppm, 4500 ppm or 5000 ppm.

[0017] In a second aspect, the present application provides a method for preparing a core-shell structured cathode precursor material as described in the first aspect, the preparation method comprising the following steps:

[0018] Adding the first nickel-cobalt-manganese mixed salt solution, the precipitant solution, the first complexing agent solution and the dopant solution into the base solution in parallel, and sequentially performing the first stage coprecipitation reaction and the second stage coprecipitation reaction;

[0019] After the second stage coprecipitation reaction is completed, the first nickel-cobalt-manganese mixed salt solution is replaced with the second nickel-cobalt-manganese mixed salt solution, and a third stage coprecipitation reaction is performed to obtain the core-shell structured cathode precursor material;

[0020] Among them, the molar amount of nickel in the first nickel-cobalt-manganese mixed salt solution accounts for ≥80% of the total molar amount of nickel, cobalt and manganese; during the second stage co-precipitation reaction, the feed flow rate of the dopant solution is gradually increased; the molar amount of manganese in the second nickel-cobalt-manganese mixed salt solution accounts for ≥45% of the total molar amount of nickel, cobalt and manganese.

[0021] In the present application, the inlet flow rate of the co-precipitation reaction in the first stage and the second stage is kept consistent.

[0022] The present application prepares a core-shell structured precursor material by a co-precipitation method in the precursor stage, and simultaneously realizes gradient doping of doping elements, thereby avoiding the uneven doping element phenomenon caused by solid-phase doping, and obtaining a structurally stable material. While ensuring the cycle performance of the material, the capacity performance is optimized, achieving a balance between cycle and capacity performance, and the preparation method is simple to operate, does not require an additional complex preparation process, and is suitable for large-scale production.

[0023] In one embodiment, the pH value of the base solution is 10-13, for example, 10, 10.3, 10.5, 10.8, 11, 11.3, 11.5, 11.8, 12, 12.3, 12.5, 12.8 or 13.

[0024] In one embodiment, the concentration of aqueous ammonia in the base solution is 5 to 20 g / L, for example, 5 g / L, 10 g / L, 15 g / L or 20 g / L.

[0025] In one embodiment, the temperature of the base liquid is 40-80°C, such as 40°C, 50°C, 60°C, 70°C or 80°C.

[0026] In one embodiment, the stirring rate of the base liquid is 200-500 rpm, for example, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm or 500 rpm.

[0027] In one embodiment, the preparation parameters during the coprecipitation reaction can be adaptively adjusted based on the base liquid without any special limitation.

[0028] In one embodiment, the dopant solution further includes a second complexing agent.

[0029] In the present application, adding the second complexing agent solution to the dopant solution is beneficial to the uniform precipitation of the doping element, so that the doping element is evenly distributed in the precursor.

[0030] In one embodiment, the particle size of the reaction product of the first stage coprecipitation reaction is 45-55% of the final target particle size, for example, 45%, 46%, 47%, 48%, 49%, 50%, 51%, 52%, 53%, 54% or 55%.

[0031] In one embodiment, the particle size of the reaction product of the second stage coprecipitation reaction is 85-95% of the final target particle size, for example, 85%, 86%, 87%, 88%, 89%, 80%, 81%, 82%, 83%, 84% or 85%.

[0032] In this application, the core is prepared in two stages. In the first stage, the core particle size is too large, exceeding 55%, which will lead to a high overall nickel content. + / Ni 2+ The cations are severely mixed and the cycle stability is poor; the particle size of the core obtained in the second stage is too small, less than 85%, that is, the thickness of the gradient-doped core layer is too thin, which will lead to a low overall nickel content and a low initial capacity. The particle size of the core obtained in the second stage is too large, which will lead to a too thin shell, thus affecting the core-shell contact to be not close enough and the shell is easy to fall off.

[0033] In one embodiment, during the second stage co-precipitation reaction, the feed flow rate of the dopant solution is gradually increased at a rate of 0.1 to 2 L / h, for example, 0.1 L / h, 0.3 L / h, 0.5 L / h, 0.8 L / h, 1 L / h, 1.3 L / h, 1.5 L / h, 1.8 L / h or 2 L / h.

[0034] In the present application, during the second stage of the co-precipitation reaction, if the feed flow rate of the dopant solution increases too quickly, exceeding 2 L / h, it may easily lead to poor precipitation of the doping elements, affecting the uniformity, while if it is too slow, less than 0.1 L / h, it may affect the amount of doping.

[0035] In one embodiment, the preparation method comprises the following steps:

[0036] A first nickel-cobalt-manganese mixed salt solution, a precipitant solution, a first complexing agent solution, and a dopant solution containing a second complexing agent are added concurrently to a base solution to perform a first-stage coprecipitation reaction. After the particle size of a reaction product of the first-stage coprecipitation reaction is 45-55% of the final target particle size, a second-stage coprecipitation reaction is performed. During the second-stage coprecipitation reaction, the feed flow rate of the dopant solution is gradually increased at a rate of 0.1-2 L / h until the particle size of the reaction product of the second-stage coprecipitation reaction is 85-95% of the final target particle size, and the reaction is terminated.

[0037] After the second stage coprecipitation reaction is completed, the first nickel-cobalt-manganese mixed salt solution is replaced with the second nickel-cobalt-manganese mixed salt solution, and a third stage coprecipitation reaction is performed to obtain the core-shell structured cathode precursor material;

[0038] Among them, the molar amount of nickel in the first nickel-cobalt-manganese mixed salt solution accounts for ≥80% of the total molar amount of nickel, cobalt and manganese; during the second stage co-precipitation reaction, the feed flow rate of the dopant solution is gradually increased; the molar amount of manganese in the second nickel-cobalt-manganese mixed salt solution accounts for ≥45% of the total molar amount of nickel, cobalt and manganese.

[0039] In a third aspect, the present application provides a lithium-ion positive electrode material, which is obtained by mixing and sintering the core-shell structured positive electrode precursor material as described in the first aspect with a lithium source.

[0040] In the present application, a lithium ion material is prepared from a precursor material, which improves the structural stability of the lithium ion positive electrode material, thereby achieving a dual consideration of cycle performance and capacity.

[0041] Furthermore, the precursor material of the present application can also be used in sodium batteries.

[0042] In one embodiment, the sintering is performed in an oxygen-containing atmosphere.

[0043] In the present application, the preparation process of the lithium-ion positive electrode material is all conventional technical means, and those skilled in the art can adaptably select the sintering temperature, sintering number and sintering time according to actual needs.

[0044] In a fourth aspect, the present application further provides a lithium-ion battery, which includes the lithium-ion positive electrode material as described in the third aspect.

[0045] Compared with the related art, this application has the following beneficial effects:

[0046] The precursor material provided in the present application adopts a nickel-rich material with high energy density as the core and a high manganese material with high stability as the shell, and at the same time, gradient doping of the doping elements is coordinated, and gradient doping is performed in the core structure close to the shell (the doping amount in other positions of the core and the shell is not gradient doped). The capacity performance is optimized while ensuring the cycle performance of the material. The gradient doping also makes the bond between the core and the shell tighter, and the shell is not easy to fall off, thereby improving the stability of the core-shell structure positive electrode material, thereby improving the performance of the lithium-ion positive electrode material.

[0047] Still other aspects will become apparent upon reading and understanding the detailed description. DETAILED DESCRIPTION

[0048] The technical solution of the present application is further illustrated below by specific examples. Those skilled in the art should understand that the examples are only for facilitating understanding of the present application and should not be regarded as specific limitations of the present application.

[0049] Example 1

[0050] This embodiment provides a positive electrode precursor material, the precursor is a core-shell structure, the core includes a chemical formula of Ni 0.9 Co 0.05 Mn 0.05 (OH)2 first nickel cobalt manganese precursor material, the shell layer includes a chemical formula of Ni 0.45 Co 0.05Mn 0.5 A second nickel-cobalt-manganese precursor material of (OH)2, wherein the precursor material is doped with Al element from the core to the surface; the Al element is doped in a gradient manner in the part of the core close to the shell.

[0051] The preparation method of the positive electrode precursor material is as follows:

[0052] (1) nickel salt, cobalt salt, and manganese salt metal salts are prepared into a 2 mol / L aqueous solution A1 at a metal molar ratio of 90:5:5, and nickel salt, cobalt salt, and manganese salt metal salts are prepared into a 2 mol / L aqueous solution A2 at a metal molar ratio of 45:5:50, 32% industrial liquid caustic soda is used as a precipitant B, and 15% ammonia water is used as a complexing agent C;

[0053] Al2(SO4)3 and FeSO4 were prepared into a 0.1 mol / L aqueous solution at a metal molar ratio of 1:1, and 0.1 mol / L EDTA was used as a complexing agent D. The mixture was mixed and stirred to form a metal ion complexing solution E;

[0054] Prepare the base liquid and introduce N2 as the protective gas. Adjust the pH of the base liquid to the range of 11.5-11.8, the ammonia concentration to 6.0-6.5 g / L, the temperature to 44 ° C, and the stirring speed to 380 rpm.

[0055] (2) Solution A1, solution B, solution C, and solution E were simultaneously pumped into the reactor at a rate of 40 L / h, 13.8 L / h, 2 L / h, and 8.1 L / h, respectively. The pH value during the stable reaction period was controlled within 10.5, the ammonia concentration was controlled within the range of 5.0-6.5 g / L, the total alkali concentration was controlled within the range of 14 g / L, and the stirring speed was 380 rpm to carry out a coprecipitation reaction.

[0056] When the inner layer nickel-cobalt-manganese ternary precursor grows to a particle size of 4 μm (first stage coprecipitation reaction), the initial feed flow rates of the nickel-cobalt-manganese solution, ammonia solution, liquid alkali solution, and doping solution remain unchanged, but the feed flow rate of the doping solution is gradually increased at a rate of 2 L / h until the ternary precursor grows to 7 μm and stops (second stage coprecipitation reaction);

[0057] Solution A2, solution B, solution C and solution E were pumped into the above mixed solution at speeds of 40 L / h, 13.8 L / h, 2 L / h and 8.1 L / h, respectively, keeping the pH, supernatant ammonia concentration, temperature, stirring speed and other parameters stable. After the target particle size D50 reached 8 μm, the feeding was stopped (third stage coprecipitation reaction), and centrifugal washing, drying, screening, iron removal, and packaging were performed to obtain the core-shell structured gradient-doped positive electrode precursor material.

[0058] Example 2

[0059] This embodiment provides a positive electrode precursor material, the precursor is a core-shell structure, the core includes a chemical formula of Ni 0.8 Co 0.1 Mn 0.1 (OH)2 first nickel cobalt manganese precursor material, the shell layer includes a chemical formula of Ni 0.45 Co 0.1 Mn 0.45 A second nickel-cobalt-manganese precursor material of (OH)2, wherein the precursor material is doped with Zr element from the core to the surface; the Zr element is doped in a gradient manner in the part of the core close to the shell.

[0060] The preparation method of the positive electrode precursor material is as follows:

[0061] (1) nickel salt, cobalt salt, and manganese salt metal salts are prepared into a 2 mol / L aqueous solution A1 at a metal molar ratio of 90:5:5, and nickel salt, cobalt salt, and manganese salt metal salts are prepared into a 2 mol / L aqueous solution A2 at a metal molar ratio of 45:5:50, 32% industrial liquid caustic soda is used as a precipitant B, and 15% ammonia water is used as a complexing agent C;

[0062] Al2(SO4)3 and FeSO4 were prepared into a 0.1 mol / L aqueous solution at a metal molar ratio of 1:1, and 0.1 mol / L EDTA was used as a complexing agent D. The mixture was mixed and stirred to form a metal ion complexing solution E;

[0063] Prepare the base liquid and introduce N2 as the protective gas. Adjust the pH of the base liquid to the range of 11.5-11.8, the ammonia concentration to 6.0-6.5 g / L, the temperature to 44 ° C, and the stirring speed to 380 rpm.

[0064] (2) Solution A1, solution B, solution C, and solution E were simultaneously pumped into the reactor at a rate of 40 L / h, 13.8 L / h, 2 L / h, and 8.1 L / h, respectively. The pH value during the stable reaction period was controlled within 10.5, the ammonia concentration was controlled within the range of 5.0-6.5 g / L, the total alkali concentration was controlled within the range of 14 g / L, and the stirring speed was 380 rpm to carry out a coprecipitation reaction.

[0065] When the inner layer nickel-cobalt-manganese ternary precursor grows to a particle size of 4 μm (first stage coprecipitation reaction), the initial feed flow rates of the nickel-cobalt-manganese solution, ammonia solution, liquid alkali solution, and doping solution remain unchanged, but the feed flow rate of the doping solution is gradually increased at an increasing rate of 0.2 L / h until the ternary precursor grows to 7 μm and stops (second stage coprecipitation reaction);

[0066] Solution A2, solution B, solution C and solution E were pumped into the above mixed solution at speeds of 40 L / h, 13.8 L / h, 2 L / h and 8.1 L / h, respectively, keeping the pH, supernatant ammonia concentration, temperature, stirring speed and other parameters stable. After the target particle size D50 reached 8 μm, the feeding was stopped (third stage coprecipitation reaction), and centrifugal washing, drying, screening, iron removal, and packaging were performed to obtain the core-shell structured gradient-doped positive electrode precursor material.

[0067] Example 3

[0068] The difference between this embodiment and embodiment 1 is that the doping elements in this embodiment include Al, Cu and Fe;

[0069] In the preparation method, in step (1): Al2(SO4)3, CuSO4, and FeSO4 are prepared into a 0.1 mol / L aqueous solution at a metal molar ratio of 1:1:1, EDTA with a concentration of 0.1 mol / L is used as a complexing agent D, and the mixture is mixed and stirred to form a metal ion complexing solution E.

[0070] The rest of the preparation methods and parameters were the same as those in Example 1.

[0071] Example 4

[0072] This embodiment provides a positive electrode precursor material, the precursor is a core-shell structure, the core includes a chemical formula of Ni 0.9 Co 0.05 Mn 0.05 (OH)2 first nickel cobalt manganese precursor material, the shell layer includes a chemical formula of Ni 0.45 Co 0.05 Mn 0.5 A second nickel-cobalt-manganese precursor material of (OH)2, wherein the precursor material is doped with Al element from the core to the surface; the Al element is doped in a gradient manner in the part of the core close to the shell.

[0073] The preparation method of the positive electrode precursor material is as follows:

[0074] (1) nickel salt, cobalt salt, and manganese salt metal salts are prepared into a 2 mol / L aqueous solution A1 at a metal molar ratio of 90:5:5, and nickel salt, cobalt salt, and manganese salt metal salts are prepared into a 2 mol / L aqueous solution A2 at a metal molar ratio of 45:5:50, 32% industrial liquid caustic soda is used as a precipitant B, and 15% ammonia water is used as a complexing agent C;

[0075] Al2(SO4)3 and FeSO4 were prepared into a 0.1 mol / L aqueous solution at a metal molar ratio of 1:1, and 0.1 mol / L EDTA was used as a complexing agent D. The mixture was mixed and stirred to form a metal ion complexing solution E;

[0076] Prepare the base liquid and introduce N2 as the protective gas. Adjust the pH of the base liquid to the range of 11.5-11.8, the ammonia concentration to 6.0-6.5 g / L, the temperature to 44 ° C, and the stirring speed to 380 rpm.

[0077] (2) Solution A1, solution B, solution C, and solution E were simultaneously pumped into the reactor at a rate of 40 L / h, 13.8 L / h, 2 L / h, and 8.1 L / h, respectively. The pH value during the stable reaction period was controlled within 10.5, the ammonia concentration was controlled within the range of 5.0-6.5 g / L, the total alkali concentration was controlled within the range of 14 g / L, and the stirring speed was 380 rpm to carry out a coprecipitation reaction.

[0078] When the inner layer nickel-cobalt-manganese ternary precursor grows to a particle size of 4.4 μm (first stage coprecipitation reaction), the initial feed flow rates of the nickel-cobalt-manganese solution, ammonia solution, liquid alkali solution, and doping solution remain unchanged, but the feed flow rate of the doping solution is gradually increased at an increasing rate of 0.2 L / h until the ternary precursor grows to 7.6 μm and stops (second stage coprecipitation reaction);

[0079] Solution A2, solution B, solution C and solution E were pumped into the above mixed solution at speeds of 40 L / h, 13.8 L / h, 2 L / h and 8.1 L / h, respectively, keeping the pH, supernatant ammonia concentration, temperature, stirring speed and other parameters stable. After the target particle size D50 reached 8 μm, the feeding was stopped (third stage coprecipitation reaction), and centrifugal washing, drying, screening, iron removal, and packaging were performed to obtain the core-shell structured gradient-doped positive electrode precursor material.

[0080] Example 5

[0081] This embodiment provides a positive electrode precursor material, the precursor is a core-shell structure, the core includes a chemical formula of Ni 0.9 Co 0.05 Mn 0.05 (OH)2 first nickel cobalt manganese precursor material, the shell layer includes a chemical formula of Ni 0.45 Co 0.05 Mn 0.5 A second nickel-cobalt-manganese precursor material of (OH)2, wherein the precursor material is doped with Al element from the core to the surface; the Al element is doped in a gradient manner in the part of the core close to the shell.

[0082] The preparation method of the positive electrode precursor material is as follows:

[0083] (1) nickel salt, cobalt salt, and manganese salt metal salts are prepared into a 2 mol / L aqueous solution A1 at a metal molar ratio of 90:5:5, and nickel salt, cobalt salt, and manganese salt metal salts are prepared into a 2 mol / L aqueous solution A2 at a metal molar ratio of 45:5:50, 32% industrial liquid caustic soda is used as a precipitant B, and 15% ammonia water is used as a complexing agent C;

[0084] Al2(SO4)3 and FeSO4 were prepared into a 0.1 mol / L aqueous solution at a metal molar ratio of 1:1, and 0.1 mol / L EDTA was used as a complexing agent D. The mixture was mixed and stirred to form a metal ion complexing solution E;

[0085] Prepare the base liquid and introduce N2 as the protective gas. Adjust the pH of the base liquid to the range of 11.5-11.8, the ammonia concentration to 6.0-6.5 g / L, the temperature to 44 ° C, and the stirring speed to 380 rpm.

[0086] (2) Solution A1, solution B, solution C, and solution E were simultaneously pumped into the reactor at a rate of 40 L / h, 13.8 L / h, 2 L / h, and 8.1 L / h, respectively. The pH value during the stable reaction period was controlled within 10.5, the ammonia concentration was controlled within the range of 5.0-6.5 g / L, the total alkali concentration was controlled within the range of 14 g / L, and the stirring speed was 380 rpm to carry out a coprecipitation reaction.

[0087] When the inner layer nickel-cobalt-manganese ternary precursor grows to a particle size of 4 μm (first stage coprecipitation reaction), the initial feed flow rates of the nickel-cobalt-manganese solution, ammonia solution, liquid alkali solution, and doping solution remain unchanged, but the feed flow rate of the doping solution is gradually increased at a rate of 2 L / h until the ternary precursor grows to 6.8 μm and stops (second stage coprecipitation reaction);

[0088] Solution A2, solution B, solution C and solution E were pumped into the above mixed solution at speeds of 40 L / h, 13.8 L / h, 2 L / h and 8.1 L / h, respectively, keeping the pH, supernatant ammonia concentration, temperature, stirring speed and other parameters stable. After the target particle size D50 reached 8 μm, the feeding was stopped (third stage coprecipitation reaction), and centrifugal washing, drying, screening, iron removal, and packaging were performed to obtain the core-shell structured gradient-doped positive electrode precursor material.

[0089] Example 6

[0090] The difference between this embodiment and embodiment 1 is that the particle size obtained by the first stage coprecipitation reaction in step (2) of this embodiment is 4.8 μm (60% of the final target particle size).

[0091] The rest of the preparation methods and parameters were the same as those in Example 1.

[0092] Example 7

[0093] The difference between this embodiment and embodiment 1 is that the particle size obtained by the second stage coprecipitation reaction in step (2) of this embodiment is 6.4 μm (80% of the final target particle size).

[0094] The rest of the preparation methods and parameters were the same as those in Example 1.

[0095] Example 8

[0096] The difference between this embodiment 1 and embodiment 1 is that during the second stage coprecipitation reaction in step (2) of this embodiment, the feed flow rate of the doping solution E is gradually increased at an increasing rate of 2.5 L / h.

[0097] The rest of the preparation methods and parameters were the same as those in Example 1.

[0098] Comparative Example 1

[0099] This comparative example provides a positive electrode precursor material, which is not doped in any way and has a non-core-shell structure, that is, a pure core.

[0100] The preparation method comprises the following steps:

[0101] (1) nickel salt, cobalt salt, manganese salt and other metal salts are prepared into a 2 mol / L aqueous solution A1 at a metal molar ratio of 90:5:5, 32% industrial liquid caustic soda is used as a precipitant B, and 15% ammonia water is used as a complexing agent C;

[0102] Prepare the base solution and introduce N2 as the protective gas. Adjust the pH of the base solution to 11.2-11.6, the ammonia concentration to 6-6.5 g / L, the temperature to 42°C, and the stirring speed to 380 rpm.

[0103] (2) Solution A, solution B, and solution C were simultaneously pumped into the reactor at a rate of 40 L / h, 13.8 L / h, and 2 L / h, respectively. The pH value during the reaction stabilization period was controlled within the range of 10.2-10.5, the ammonia concentration was controlled within the range of 6.5 g / L, the total alkali concentration was controlled within the range of 14 g / L, and the stirring speed was controlled within the range of 380 rpm. A coprecipitation reaction was performed. The entire reaction time was 90 h.

[0104] (3) After D50 reaches 8 μm, the feeding is stopped and the product is centrifuged, washed, dried, screened, iron removed, and packaged to obtain a high-nickel ternary precursor.

[0105] Comparative Example 2

[0106] The difference between this comparative example and Example 1 is that in the positive electrode precursor material provided in this comparative example, the doping element Al is not doped in a gradient-incremental manner, and the feed flow rate of the dopant solution remains unchanged throughout the entire preparation process.

[0107] The rest of the preparation methods and parameters were the same as those in Example 1.

[0108] Comparative Example 3

[0109] The difference between this comparative example and Example 1 is that the positive electrode precursor material in this comparative example is a non-core-shell structure, that is, the chemical formula of the core is maintained and the same Al gradient doping as in Example 1 is performed.

[0110] In the preparation method, solution A2 is not prepared, and A1 is used as the main element solution throughout the preparation process.

[0111] The rest of the preparation methods and parameters were the same as those in Example 1.

[0112] The positive electrode precursor materials provided by Examples 1-8 and Comparative Examples 1-3 were uniformly mixed with lithium hydroxide in a mortar at a ratio of 1:1.05, and calcined at 850° C. for 20 h to obtain a positive electrode material.

[0113] The lithium ion positive electrode materials provided in Examples 1-8 and Comparative Examples 1-3 were used as positive electrode active materials, and lithium sheets were used as counter electrodes to prepare button batteries.

[0114] The performance tests were performed on the lithium-ion batteries provided in Examples 1-8 and Comparative Examples 1-3 under the following test conditions:

[0115] The battery performance test system (model: BTS05 / 10C8D-HP) of Shenghong Electric Co., Ltd. was used to test the initial discharge capacity and 100-cycle capacity retention rate at a charge and discharge current of 0.5C.

[0116] The test results are shown in Table 1, which also shows the doping amounts of the doping elements provided in Examples 1-8 and Comparative Examples 1-3.

[0117] Table 1

[0118] From the data results of Example 1 and Example 6, it can be seen that the particle size of the first stage co-precipitation reaction is too large, exceeding 55% of the target particle size, which is not conducive to the cyclic stability of the material.

[0119] From the data results of Example 1 and Example 7, it can be seen that if the particle size of the second stage co-precipitation reaction is too small, less than 85% of the target particle size, the recycling performance of the material will be affected.

[0120] From the data results of Example 1 and Example 8, it can be seen that the increase rate during the second stage of the co-precipitation reaction is too fast, which will lead to uneven distribution of doping elements and poor capacity and cycle performance.

[0121] From the data results of Example 1 and Comparative Example 1, it can be seen that the precursor material provided in the present application has a stable structure and achieves a balance between cycle performance and capacity.

[0122] From the data results of Example 1 and Comparative Examples 2 and 3, it can be seen that pure core-shell structure and pure gradient doping are unable to achieve the requirements of high capacity and high cycle, that is, the positive electrode precursor material provided in this application achieves a synergistic effect.

[0123] In summary, the precursor material provided in the present application adopts a nickel-rich material with high energy density as the core and a high manganese material with high stability as the shell, and at the same time, the gradient doping of the doping elements is coordinated, and gradient doping is performed in the core structure close to the shell (the doping amount in other positions of the core and the shell is not gradient doped). The capacity performance is optimized while ensuring the cycle performance of the material, and the gradient doping also makes the bonding between the core and the shell tighter, and the shell is not easy to fall off, thereby improving the stability of the core-shell structure positive electrode material, thereby improving the performance of the lithium-ion positive electrode material.

[0124] The applicant declares that the above is only a specific implementation method of the present application, but the protection scope of the present application is not limited thereto. Technical personnel in the relevant technical field should understand that any changes or substitutions that can be easily thought of by technical personnel in the relevant technical field within the technical scope disclosed in this application fall within the protection scope and disclosure scope of this application.

Claims

1. A core-shell structured cathode precursor material, wherein: The core-shell structured positive electrode precursor material comprises a first nickel-cobalt-manganese precursor core and a second nickel-cobalt-manganese precursor shell layer located on the surface of the precursor core; Among them, the core-shell structured positive electrode precursor material contains doping elements; the molar amount of nickel in the core of the first nickel-cobalt-manganese precursor accounts for ≥80% of the total molar amount of nickel-cobalt-manganese, and the doping element increases gradually in the part of the core of the first nickel-cobalt-manganese precursor close to the shell layer; the molar amount of manganese in the core of the second nickel-cobalt-manganese precursor accounts for ≥45% of the total molar amount of nickel-cobalt-manganese.

2. The core-shell structured cathode precursor material according to claim 1, wherein: The total doping amount of the doping elements is 1000-5000 ppm.

3. A method for preparing a core-shell structured cathode precursor material as claimed in claim 1 or 2, comprising the following steps: Adding the first nickel-cobalt-manganese mixed salt solution, the precipitant solution, the first complexing agent solution and the doping agent solution into the base solution in parallel, and sequentially performing a first stage coprecipitation reaction and a second stage coprecipitation reaction; After the second stage coprecipitation reaction is completed, the first nickel-cobalt-manganese mixed salt solution is replaced with the second nickel-cobalt-manganese mixed salt solution, and a third stage coprecipitation reaction is performed to obtain the positive electrode precursor material of the core-shell structure; Among them, the molar amount of nickel in the first nickel-cobalt-manganese mixed salt solution accounts for ≥80% of the total molar amount of nickel, cobalt and manganese; during the second stage co-precipitation reaction, the feed flow rate of the dopant solution is gradually increased; the molar amount of manganese in the second nickel-cobalt-manganese mixed salt solution accounts for ≥45% of the total molar amount of nickel, cobalt and manganese.

4. The method for preparing a core-shell structured cathode precursor material according to claim 3, wherein: The pH value of the base liquid is 10-13.

5. The method for preparing a core-shell structured cathode precursor material according to claim 3 or 4, wherein: The concentration of the ammonia water in the base solution is 5-20 g / L.

6. The method for preparing a core-shell structured cathode precursor material according to any one of claims 3 to 5, wherein: The temperature of the base liquid is 40-80°C.

7. The method for preparing a core-shell structured cathode precursor material according to any one of claims 3 to 6, wherein: The stirring rate of the base liquid is 200-500 rpm.

8. The method for preparing a core-shell structured cathode precursor material according to any one of claims 3 to 7, wherein: The dopant solution also includes a second complexing agent.

9. The method for preparing a core-shell structured cathode precursor material according to any one of claims 3 to 8, wherein: The particle size of the reaction product of the first stage coprecipitation reaction is 45-55% of the final target particle size.

10. The method for preparing a core-shell structured cathode precursor material according to any one of claims 3 to 9, wherein: The particle size of the reaction product of the second stage coprecipitation reaction is 85-95% of the final target particle size.

11. The method for preparing a core-shell structured cathode precursor material according to any one of claims 3 to 10, wherein: During the second stage coprecipitation reaction, the feed flow rate of the dopant solution is gradually increased at a rate of 0.1 to 2 L / h.

12. The method for preparing a core-shell structured cathode precursor material according to any one of claims 3 to 11, comprising the following steps: A first nickel-cobalt-manganese mixed salt solution, a precipitant solution, a first complexing agent solution and a doping agent solution containing a second complexing agent are added to a base solution in parallel to perform a first-stage coprecipitation reaction. After the particle size of the reaction product of the first-stage coprecipitation reaction is 45-55% of the final target particle size, a second-stage coprecipitation reaction is performed. During the second-stage coprecipitation reaction, the feed flow rate of the doping agent solution is gradually increased at a rate of 0.1-2 L / h until the particle size of the reaction product of the second-stage coprecipitation reaction is 85-95% of the final target particle size, and the reaction is terminated. After the second stage of coprecipitation reaction, the first nickel-cobalt-manganese mixed salt solution is replaced with the second nickel-cobalt-manganese Mixing the salt solution and performing a third-stage coprecipitation reaction to obtain the positive electrode precursor material of the core-shell structure; Among them, the molar amount of nickel in the first nickel-cobalt-manganese mixed salt solution accounts for ≥80% of the total molar amount of nickel, cobalt and manganese; during the second stage co-precipitation reaction, the feed flow rate of the dopant solution is gradually increased; the molar amount of manganese in the second nickel-cobalt-manganese mixed salt solution accounts for ≥45% of the total molar amount of nickel, cobalt and manganese.

13. A lithium ion positive electrode material, wherein: The lithium ion positive electrode material is obtained by mixing and sintering the core-shell structured positive electrode precursor material according to any one of claims 1 or 2 with a lithium source.

14. The lithium ion positive electrode material according to claim 13, wherein The sintering is performed in an oxygen-containing atmosphere.

15. A lithium ion battery, wherein: The lithium ion battery comprises the lithium ion positive electrode material as claimed in claim 13 or 14.

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