A dual boron-modified lithium-ion battery high-nickel positive electrode material and a preparation method thereof

Abstract

This invention belongs to the field of lithium-ion battery material preparation technology, and relates to a double boron modified high-nickel cathode material for lithium-ion batteries and its preparation method. The preparation method of the double boron modified high-nickel cathode material for lithium-ion batteries includes the following steps: (1) mixing a boron-containing ternary salt solution, a sodium hydroxide solution, and a complexing agent solution for reaction, and drying the solid phase obtained after solid-liquid separation of the reaction product to obtain an in-situ boron-doped hydroxide precursor; (2) uniformly mixing a lithium source with the in-situ boron-doped hydroxide precursor obtained in step (1), and obtaining an intermediate after a first sintering; uniformly mixing a boron source with the obtained intermediate, and obtaining the double boron modified high-nickel cathode material for lithium-ion batteries after a second sintering. This invention improves the electrochemical performance of the high-nickel cathode material for lithium-ion batteries by introducing boron element in situ and coating it with a uniformly fast ion conductor boron-containing compound.

Description

Technical Field

[0001] This invention belongs to the field of lithium-ion battery material preparation technology, and relates to a double boron modified high-nickel cathode material for lithium-ion batteries and its preparation method. Background Technology

[0002] Lithium-ion batteries, as a new type of green energy, have been widely used in electronic products, transportation vehicles, large-scale energy storage power stations, and aerospace and related fields. Among them, layered nickel-rich ternary cathode materials are considered one of the most promising cathode materials due to their advantages such as high charge-discharge capacity, low cost, and low toxicity. However, this material suffers from problems such as low initial coulombic efficiency and easy collapse of the layered structure, which makes it prone to voltage plateaus and rapid capacity decay during cycling, as well as poor rate performance, seriously hindering its industrialization.

[0003] To address the issues of easy structural collapse, side reactions with electrolyte, and easy dissolution of transition metals in layered nickel-rich ternary cathode materials, existing research has proposed heterogeneous element doping and / or surface coating modification methods. CN115995529A discloses an in-situ boron-doped quaternary cathode material and its preparation method and application. The preparation method includes the following steps: (1) mixing nickel salt, cobalt salt, manganese salt and borate to obtain a metal salt solution; (2) mixing a precipitant, a complexing agent and the metal salt solution obtained in step (1) to perform a co-precipitation reaction to obtain a precursor; (3) mixing lithium salt, aluminum source and the precursor obtained in step (2) to perform sintering, pulverizing and sieving to obtain a secondary material; (4) performing wet post-treatment on the secondary material obtained in step (3) to obtain the in-situ boron-doped quaternary cathode material. CN114864923A discloses a boron-doped nickel-cobalt-manganese cathode material and its preparation method. Boron can replace transition metal atoms in the crystal lattice to form BO bonds with higher bond energy, stabilizing the crystal structure, improving high-temperature storage performance, and reducing battery gas production. However, high-nickel cathode materials with simple in-situ boron doping still suffer from problems such as surface transition metal dissolution and severe side reactions with the electrolyte.

[0004] CN116553632A discloses a high-nickel cathode material, its preparation method, cathode sheet, battery, and electrical device. The high-nickel cathode material is treated with H3BO3, which reacts with residual alkali to generate fast-ion conductors Li2B4O7 and LiBO2, coating the surface of the high-nickel cathode material. This solves the problems of high residual alkali and blocked lithium-ion transport channels hindering performance in traditional high-nickel cathode materials. However, if a solid-phase method is used to process the high-nickel cathode material, there is an issue of uneven distribution of the boron-containing coating layer, with some areas of the cathode material surface still in direct contact with the electrolyte. If a liquid-phase method is used, with anhydrous ethanol as the solvent and H3BO3 as the solute, although this can improve the uneven distribution of the boron-containing coating layer, anhydrous ethanol is a flammable and explosive chemical and is not suitable for large-scale use in cathode material plants with high-temperature environments.

[0005] In summary, there is an urgent need to provide a preparation method that can simultaneously improve the uniformity of element and coating layer distribution, structural stability, electrochemical performance, and production efficiency of high-nickel cathode materials for lithium-ion batteries. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a dual-boron modified high-nickel cathode material for lithium-ion batteries and its preparation method. By introducing boron elements in situ and coating a uniformly fast-ion conductor boron-containing compound, the elemental and coating layer uniformity, structural stability, electrochemical performance, and production efficiency of the high-nickel cathode material for lithium-ion batteries are simultaneously improved.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a method for preparing a high-nickel cathode material for lithium-ion batteries with dual boron modification, the method comprising the following steps:

[0009] (1) A boron-containing ternary salt solution, a sodium hydroxide solution and a complexing agent solution are mixed and reacted. After solid-liquid separation of the reaction product, the resulting solid phase is dried to obtain an in-situ boron-doped hydroxide precursor.

[0010] (2) The lithium source and the in-situ boron-doped hydroxide precursor obtained in step (1) are uniformly mixed, and an intermediate is obtained after the first sintering; the boron source and the obtained intermediate are uniformly mixed, and the high-nickel cathode material of the double boron modified lithium-ion battery is obtained after the second sintering.

[0011] The present invention provides a method for preparing high-nickel cathode materials for lithium-ion batteries with dual boron modification. Based on the co-precipitation method that can be prepared on a large scale for industrial use, boron is introduced in situ and the boron doping content is controlled. Then, a uniformly coated fast ion conductor boron-containing compound aLi2O·bB2O3 is introduced, thereby simultaneously improving the uniformity of element and coating layer distribution, structural stability, cycle performance, rate performance, energy density and production efficiency of the lithium-ion battery cathode material. Specifically, in-situ boron doping modification of high-nickel cathode materials can improve the crystal structure of high-nickel cathode materials, enhance the wettability of boron-containing compounds aLi2O·bB2O3 (B2O3, LiBO2, Li2B4O7, Li3BO3, etc.) on the cathode material surface, improve the uniformity of boron-containing compound coating on the high-nickel cathode material surface, and reduce the direct exposure of the high-nickel cathode material surface to the electrolyte. At the same time, boron doping can introduce high-bond-energy BO bonds, improve the structural stability of high-nickel cathode materials, reduce the release of lattice oxygen, and improve high-temperature storage performance. The glass-phase boron-containing compound aLi2O·bB2O3 coating layer has high lithium-ion transport capacity, which can improve the lithium-ion diffusion rate of the cathode material and improve its rate performance while isolating the electrolyte from direct contact with the high-nickel cathode material. This invention utilizes a mature industrial co-precipitation process to prepare boron-doped lithium-ion battery cathode materials, which features simple operation and low energy consumption. Furthermore, the prepared cathode materials can achieve atomic-level uniform distribution, excellent spherical particle dispersion, high tap density, and good product consistency and repeatability.

[0012] Preferably, the metal concentration of the boron-containing ternary salt solution in step (1) is 0.5-2 mol / L, for example, it can be 0.5 mol / L, 0.8 mol / L, 1 mol / L, 1.5 mol / L or 2 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0013] Preferably, the boron doping amount of the boron-containing ternary salt solution in step (1) is 1000-10000ppm, for example, it can be 1000ppm, 3000ppm, 5000ppm, 8000ppm or 10000ppm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0014] Preferably, the boron-containing ternary salt solution in step (1) is obtained by mixing nickel salt, cobalt salt, manganese salt, boron source and deionized water.

[0015] Preferably, the molar ratio of nickel, cobalt, manganese and boron in the boron-containing ternary salt solution in step (1) is x:y:z:c, x+y+z+c=1, x≥0.6, y≤0.3, z≤0.2, c≤0.03.

[0016] The value x ≥ 0.6 can be, for example, 0.6, 0.7, 0.8 or 0.9, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0017] The value y ≤ 0.3 can be, for example, 0.3, 0.25, 0.2, 0.15, 0.1, or 0.05, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0018] The value z ≤ 0.2 can be, for example, 0.2, 0.17, 0.1, 0.09 or 0.03, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0019] The value c ≤ 0.03 can be, for example, 0.03, 0.025, 0.02, 0.015 or 0.01, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0020] 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.

[0021] 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 or cobalt chloride, or a combination of cobalt sulfate, cobalt nitrate, and cobalt chloride.

[0022] 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.

[0023] Preferably, the boron source includes any one or a combination of at least two of boric acid, boron oxide, or sodium borate. Typical but non-limiting combinations include a combination of boric acid and boron oxide, a combination of boron oxide and sodium borate, or a combination of boric acid, boron oxide, and sodium borate.

[0024] Preferably, the concentration of the sodium hydroxide solution in step (1) is 6-10 mol / L, for example, it can be 6 mol / L, 7 mol / L, 8 mol / L, 9 mol / L or 10 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0025] Preferably, the concentration of the complexing agent solution in step (1) is 0.1-3 mol / L, for example, it can be 0.1 mol / L, 0.5 mol / L, 1 mol / L, 2 mol / L or 3 mol / L, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0026] Preferably, the complexing agent in the complexing agent solution in step (1) includes any one or a combination of at least two of ammonia, oxalic acid, sodium oxalate or salicylic acid. Typical but non-limiting combinations include a combination of ammonia and oxalic acid, a combination of sodium oxalate and salicylic acid, a combination of ammonia, oxalic acid and sodium oxalate, or a combination of ammonia, oxalic acid, sodium oxalate and salicylic acid.

[0027] Preferably, the mixing in step (1) involves simultaneously injecting the boron-containing ternary salt solution, sodium hydroxide solution, and complexing agent solution into the reaction vessel and stirring at a rate of 250-400 rpm, for example, 250 rpm, 280 rpm, 300 rpm, 350 rpm, or 400 rpm, but not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0028] Preferably, the flow rate of the boron-containing ternary salt solution is 7-9 L / h, the flow rate of the sodium hydroxide solution is 2-4 L / h, the flow rate of the complexing agent solution is 1-1.4 L / h, and the injection time into the reactor is 20-100 h.

[0029] The flow rate of the boron-containing ternary salt solution is 7-9 L / h, for example, it can be 7 L / h, 7.5 L / h, 8 L / h, 8.5 L / h or 9 L / h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0030] The flow rate of the sodium hydroxide solution is 2-4 L / h, for example, it can be 2 L / h, 2.5 L / h, 3 L / h, 3.5 L / h or 4 L / h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0031] The flow rate of the complexing agent solution is 1-1.4 L / h, for example, it can be 1 L / h, 1.1 L / h, 1.2 L / h, 1.3 L / h or 1.4 L / h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0032] The injection time into the reactor is 20-100 hours, for example, 20 hours, 40 hours, 60 hours, 80 hours or 100 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0033] Preferably, the reaction in step (1) is carried out at a temperature of 30-60°C for 45-50 hours.

[0034] The reaction temperature is 30-60℃, for example, it can be 30℃, 35℃, 40℃, 50℃ or 60℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0035] The reaction time is 45-50 hours, for example, 45 hours, 46 hours, 47 hours, 48 ​​hours or 50 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0036] Preferably, the pH value of the solution in the reaction step (1) is controlled between 9 and 12, for example, it can be 9, 10.6, 11 or 12, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0037] Preferably, the solid-liquid separation in step (1) includes centrifugation.

[0038] Preferably, the solid phase in step (1) is further subjected to a washing step before drying.

[0039] Preferably, the washing medium used for washing includes at least one of 60°C hot water, liquid alkali, or ethanol. It can be that liquid alkali or ethanol is used for washing first, followed by washing with 60°C hot water.

[0040] Preferably, the drying temperature in step (1) is 80-200℃ and the drying time is 22-26h.

[0041] The drying temperature is 80-200℃, for example, it can be 80℃, 100℃, 120℃, 150℃ or 200℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0042] The drying time is 22-26 hours, for example, it can be 22 hours, 23 hours, 24 hours, 25 hours or 26 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0043] Preferably, the drying in step (1) includes any one of ordinary drying, vacuum drying or drying under nitrogen atmosphere protection.

[0044] This invention achieves atomically uniform co-precipitation of Ni, Co, Mn, and doped B elements through step (1). The key to achieving the above objective lies in: selecting a suitable boron source dopant; selecting a complexing agent with a suitable complexing constant to balance the complexation-precipitation reaction; rationally matching the flow rates of the complexing agent solution and the boron-containing ternary salt solution; and rationally controlling the doping concentration of each component to prevent component segregation and the generation of impurity phases.

[0045] Preferably, the lithium source in step (2) includes lithium hydroxide and / or lithium carbonate.

[0046] Preferably, the molar ratio of the lithium source to the in-situ boron-doped hydroxide precursor in step (2) is 1.01-1.05 according to Li:(Ni+Co+Mn+B), for example, it can be 1.01, 1.02, 1.03, 1.04 or 1.05, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0047] Preferably, in step (2), the temperature of the first sintering is 800-1000℃ and the time is 10-20h.

[0048] The first sintering temperature is 800-1000℃, for example, it can be 800℃, 850℃, 900℃, 950℃ or 1000℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0049] The first sintering time is 10-20h, for example, it can be 10h, 12h, 15h, 18h or 20h, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0050] This invention controls the amount of lithium source added during the first sintering process, while optimizing the sintering temperature and time to prevent the formation of impurity phases in the cathode material.

[0051] Preferably, the boron source in step (2) includes boric acid and / or boron oxide.

[0052] Preferably, the mass of the boron source in step (2) is 0.8-1.2 wt% of the total mass of the boron source and the intermediate. For example, it can be 0.8 wt%, 0.9 wt%, 1 wt%, 1.1 wt% or 1.2 wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0053] Preferably, in step (2), the second sintering temperature is 200-500℃ and the time is 2-10h.

[0054] The second sintering temperature is 200-500℃, for example, it can be 200℃, 250℃, 300℃, 400℃ or 500℃, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0055] The second sintering time is 2-10 hours, for example, it can be 2 hours, 4 hours, 5 hours, 8 hours or 10 hours, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0056] This invention controls the amount of boron source added in the second sintering process, while optimizing the sintering temperature and time to promote complete reaction of residual lithium and uniform coating of boron-containing compounds.

[0057] Secondly, the present invention provides a double boron modified high-nickel cathode material for lithium-ion batteries, wherein the double boron modified high-nickel cathode material for lithium-ion batteries is prepared by the preparation method of the double boron modified high-nickel cathode material for lithium-ion batteries described in the first aspect.

[0058] The dual-boron modified high-nickel cathode material for lithium-ion batteries provided by this invention has the general chemical formula LiNi. x Co y Mn z B d O2@aLi2O·bB2O3, d>c; the values ​​of a and b satisfy: a=0.5, b=0.5; a=1.5, b=0.5; a=1, b=2; a=0.5, b=1.5; a=1, b=2. It exhibits dual boron modification characteristics of boron doping and boron surface coating. Boron doping enhances the structural stability of the cathode material, optimizes its crystal structure, and improves the wettability of the boron-containing coating layer, thereby improving the uniformity of the coating layer distribution. The boron-containing coating layer reduces interfacial side reactions and increases the lithium-ion diffusion rate. Through synergistic modification and control of the chemical composition and surface coating of the cathode material, the elemental distribution uniformity, structural stability, cycle performance, and rate performance of the lithium-ion battery cathode material are simultaneously improved.

[0059] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of brevity, this invention will not exhaustively list the specific point values ​​included in the range.

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

[0061] This invention provides a method for preparing high-nickel cathode materials for lithium-ion batteries with dual boron modification. Based on a co-precipitation method suitable for large-scale industrial production, it introduces boron in situ and controls its doping content, followed by the introduction of a uniformly coated fast-ion conductor boron-containing compound. Through synergistic modification and control of the cathode material's chemical composition and surface coating, the method simultaneously improves the uniformity of elemental and coating layer distribution, structural stability, electrochemical performance, and production efficiency of the lithium-ion battery cathode material. This invention utilizes a mature industrial co-precipitation process to prepare boron-doped lithium-ion battery cathode materials, featuring simple operation and low energy consumption. Furthermore, the prepared cathode material achieves atomic-level uniform distribution, excellent spherical particle dispersion, high tap density, and good product consistency and repeatability. Detailed Implementation

[0062] 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.

[0063] Example 1

[0064] This embodiment provides a dual-boron modified high-nickel cathode material for lithium-ion batteries. The preparation method of the dual-boron modified high-nickel cathode material for lithium-ion batteries includes the following steps:

[0065] (1) A boron-containing ternary salt solution was obtained by mixing nickel sulfate, cobalt sulfate, manganese sulfate, boric acid and deionized water; the molar ratio of nickel, cobalt, manganese and boron in the boron-containing ternary salt solution was 0.9:0.05:0.03:0.02; a boron-containing ternary salt solution with a metal concentration of 1.5 mol / L and a boron doping amount of 5000 ppm, a sodium hydroxide solution with a concentration of 8 mol / L and ammonia solution with a concentration of 2 mol / L were simultaneously injected into the reactor at flow rates of 8 L / h, 3 L / h and 1.2 L / h, respectively, for a total injection time of 60 h. The reaction was carried out by stirring at a rate of 300 rpm, at a temperature of 50 °C for 48 h, and the pH value of the solution was controlled at 10.6; the solid phase obtained after centrifugation of the reaction product was washed sequentially with 0.5 mol / L liquid alkali and 60 °C hot water, and then dried at 120 °C for 24 h to obtain an in-situ boron-doped hydroxide precursor.

[0066] (2) Lithium hydroxide and the in-situ boron-doped hydroxide precursor obtained in step (1) are uniformly mixed. The molar ratio of lithium hydroxide to the in-situ boron-doped hydroxide precursor is Li:(Ni+Co+Mn+B)=1.04. Then, after a first sintering at 900℃ for 15h, an intermediate is obtained. Boric acid and the obtained intermediate are uniformly mixed. The mass of boric acid is 1wt% of the total mass of boric acid and the intermediate. Then, after a second sintering at 300℃ for 5h, the double boron modified lithium-ion battery high-nickel cathode material is obtained.

[0067] Example 2

[0068] This embodiment provides a dual-boron modified high-nickel cathode material for lithium-ion batteries. The preparation method of the dual-boron modified high-nickel cathode material for lithium-ion batteries includes the following steps:

[0069] (1) A boron-containing ternary salt solution was obtained by mixing nickel nitrate, cobalt nitrate, manganese nitrate, boron oxide and deionized water; the molar ratio of nickel, cobalt, manganese and boron in the boron-containing ternary salt solution was 0.8:0.1:0.09:0.01; a boron-containing ternary salt solution with a metal concentration of 0.5 mol / L and a boron doping amount of 10000 ppm, a sodium hydroxide solution with a concentration of 6 mol / L and an oxalic acid solution with a concentration of 0.1 mol / L were simultaneously injected into the reactor at flow rates of 7 L / h, 2 L / h and 1 L / h, respectively, for a total injection time of 20 h. The reaction was carried out by stirring at a rate of 250 rpm, at a temperature of 60 °C for 45 h, and the pH value of the solution was controlled at 9; the solid phase obtained after centrifugation of the reaction product was washed sequentially with 0.5 mol / L liquid alkali and 60 °C hot water, and then dried at 200 °C for 22 h to obtain an in-situ boron-doped hydroxide precursor.

[0070] (2) Lithium hydroxide and the in-situ boron-doped hydroxide precursor obtained in step (1) are uniformly mixed. The molar ratio of lithium hydroxide to the in-situ boron-doped hydroxide precursor is Li:(Ni+Co+Mn+B)=1.01. Then, after a first sintering at 1000℃ for 10h, an intermediate is obtained. Boric acid and the obtained intermediate are uniformly mixed. The mass of boric acid is 0.8wt% of the total mass of boric acid and intermediate. Then, after a second sintering at 500℃ for 2h, the double boron modified lithium-ion battery high-nickel cathode material is obtained.

[0071] Example 3

[0072] This embodiment provides a dual-boron modified high-nickel cathode material for lithium-ion batteries. The preparation method of the dual-boron modified high-nickel cathode material for lithium-ion batteries includes the following steps:

[0073] (1) A boron-containing ternary salt solution was obtained by mixing nickel chloride, cobalt chloride, manganese chloride, sodium borate and deionized water; the molar ratio of nickel, cobalt, manganese and boron in the boron-containing ternary salt solution was 0.6:0.2:0.17:0.03; a boron-containing ternary salt solution with a metal concentration of 2 mol / L and a boron doping amount of 1000 ppm, a sodium hydroxide solution with a concentration of 10 mol / L and a salicylic acid solution with a concentration of 3 mol / L were simultaneously injected into the reactor at flow rates of 9 L / h, 4 L / h and 1.4 L / h, respectively, for a total injection time of 100 h. The reaction was carried out by stirring at a rate of 400 rpm, at a temperature of 30 °C for 50 h, and the pH value of the solution was controlled at 12; the solid phase obtained after centrifugation of the reaction product was washed sequentially with 0.5 mol / L liquid alkali and 60 °C hot water, and then dried at 80 °C for 26 h to obtain an in-situ boron-doped hydroxide precursor.

[0074] (2) Lithium carbonate and the in-situ boron-doped hydroxide precursor obtained in step (1) are uniformly mixed. The molar ratio of lithium carbonate to the in-situ boron-doped hydroxide precursor is Li:(Ni+Co+Mn+B)=1.05. Then, after a first sintering at 800℃ for 20h, an intermediate is obtained. Boron oxide and the obtained intermediate are uniformly mixed. The mass of boron oxide is 1.2wt% of the total mass of boron oxide and the intermediate. Then, after a second sintering at 200℃ for 10h, the double boron modified lithium-ion battery high-nickel cathode material is obtained.

[0075] Example 4

[0076] This embodiment provides a double boron modified high nickel cathode material for lithium-ion batteries. The difference between the preparation method of the double boron modified high nickel cathode material for lithium-ion batteries and that of Embodiment 1 is that the flow rates of the boron-containing ternary salt solution, sodium hydroxide solution and ammonia solution in step (1) are all adjusted to 5 L / h, while the rest are the same as in Embodiment 1.

[0077] Example 5

[0078] This embodiment provides a double boron modified high nickel cathode material for lithium-ion batteries. The preparation method of the double boron modified high nickel cathode material for lithium-ion batteries differs from that of Embodiment 1 in that, except for adjusting the boron doping amount of the boron-containing ternary salt solution in step (1) to 500 ppm, the rest is the same as that of Embodiment 1.

[0079] Example 6

[0080] This embodiment provides a double boron modified high nickel cathode material for lithium-ion batteries. The preparation method of the double boron modified high nickel cathode material for lithium-ion batteries differs from that of Embodiment 1 in that, except for adjusting the boron doping amount of the boron-containing ternary salt solution in step (1) to 15000ppm, the rest is the same as that of Embodiment 1.

[0081] Example 7

[0082] This embodiment provides a double boron modified high nickel cathode material for lithium-ion batteries. The preparation method of the double boron modified high nickel cathode material for lithium-ion batteries differs from that of Embodiment 1 in that, except that the mass of boric acid in step (2) is adjusted to 0.5 wt% of the total mass of boric acid and intermediates, the rest is the same as that of Embodiment 1.

[0083] Example 8

[0084] This embodiment provides a double boron modified high nickel cathode material for lithium-ion batteries. The preparation method of the double boron modified high nickel cathode material for lithium-ion batteries differs from that of Embodiment 1 in that, except that the mass of boric acid in step (2) is adjusted to 1.5 wt% of the total mass of boric acid and intermediates, the rest is the same as that of Embodiment 1.

[0085] Example 9

[0086] This embodiment provides a double boron modified high nickel cathode material for lithium-ion batteries. The preparation method of the double boron modified high nickel cathode material for lithium-ion batteries differs from that of Embodiment 1 in that, except for adjusting the second sintering temperature in step (2) to 180°C, the rest is the same as that of Embodiment 1.

[0087] Example 10

[0088] This embodiment provides a double boron modified high nickel cathode material for lithium-ion batteries. The preparation method of the double boron modified high nickel cathode material for lithium-ion batteries differs from that of Embodiment 1 in that, except for adjusting the second sintering temperature in step (2) to 520°C, the rest is the same as that of Embodiment 1.

[0089] Comparative Example 1

[0090] This comparative example provides a high-nickel cathode material for lithium-ion batteries. The preparation method of the high-nickel cathode material for lithium-ion batteries differs from that of Example 1 in that the boron-containing ternary salt solution in step (1) is adjusted to a ternary salt solution, which is obtained by mixing nickel sulfate, cobalt sulfate, manganese sulfate and deionized water. The molar ratio of nickel, cobalt and manganese in the ternary salt solution is 0.9:0.05:0.05. The intermediate obtained in step (2) is the high-nickel cathode material for lithium-ion batteries. All other aspects are the same as in Example 1.

[0091] Comparative Example 2

[0092] This comparative example provides a boron-doped high-nickel cathode material for lithium-ion batteries. The difference between the preparation method of the boron-doped high-nickel cathode material for lithium-ion batteries and that of Example 1 is that the intermediate obtained in step (2) is the boron-doped high-nickel cathode material for lithium-ion batteries, while the rest is the same as that of Example 1.

[0093] Comparative Example 3

[0094] This comparative example provides a boron-coated high-nickel cathode material for lithium-ion batteries. The preparation method of the boron-coated high-nickel cathode material for lithium-ion batteries differs from that of Example 1 in that the boron-containing ternary salt solution in step (1) is adjusted to a ternary salt solution, which is obtained by mixing nickel sulfate, cobalt sulfate, manganese sulfate and deionized water. The molar ratio of nickel, cobalt and manganese in the ternary salt solution is 0.9:0.05:0.05, and the rest is the same as in Example 1.

[0095] Coin cell half-cells were prepared using the double boron modified high-nickel cathode materials for lithium-ion batteries provided in Examples 1-10 and the high-nickel cathode materials for lithium-ion batteries, boron-doped high-nickel cathode materials for lithium-ion batteries, and boron-coated high-nickel cathode materials for lithium-ion batteries provided in Comparative Examples 1-3, respectively. Electrochemical performance tests were then conducted. The specific steps were as follows: the positive electrode active material, conductive carbon black, and binder PVDF were mixed in a mass ratio of 90:5:5, and the mixture was coated onto aluminum foil after being mixed with NMP as a solvent. After vacuum drying at 100°C, a positive electrode sheet was obtained. Then, the negative electrode sheet (lithium sheet), the positive electrode sheet, the electrolyte (1 mol / L LiPF6, EC:DEC:EMC = 1:1:1), and the separator were assembled into a battery. Specific capacity and cycle test conditions: The battery was charged and discharged at 25±2℃ with a charge / discharge voltage of 4.25-2.5V. The cycle rates for the first three weeks were 0.2C, 0.25C, and 0.5C, respectively, followed by a cycle rate of 1C (1C=185mAh / g). The initial charge capacity, initial discharge capacity, and 100-cycle performance were tested. The results are shown in Table 1.

[0096] Table 1

[0097]

[0098] As can be seen from Table 1, the battery made from the high-nickel cathode material of the double boron modified lithium-ion battery provided by the present invention has good electrochemical performance.

[0099] A comparison of Examples 1 and 4 shows that injecting boron-containing ternary salt solution, sodium hydroxide solution, and complexing agent solution at the same flow rate leads to an excessively high reaction pH, generating a large number of small particulate products. The increased specific surface area exacerbates side reactions in the cathode material, reducing both initial efficiency and cycle performance. A comparison of Examples 1 and Examples 5 and 6 shows that excessively low boron doping concentration results in weak "pinning" of boron atoms within the crystal, leading to decreased cycle performance. Excessively high boron doping concentration leads to a decrease in the migration rate of lithium ions within the cathode material, resulting in reduced capacity. A comparison of Examples 1 and Examples 7 and 8 shows that excessively low boron source content during boron coating leads to… The coating layer is prone to cracking, re-exposing the surface of the cathode material, which then reacts with the electrolyte and consumes the electrolyte, resulting in reduced cycle performance. Excessive boron source content leads to reduced charge transfer ability between particles, resulting in decreased rate performance and reduced capacity. As can be seen from the comparison between Examples 1 and Examples 9 and 10, if the second sintering temperature is too low, the crystallinity of the boron coating layer will decrease, and the lithium ion migration ability will decrease, resulting in reduced rate performance. If the temperature is too high, the boron element in the boron coating layer will migrate and diffuse into the cathode material, resulting in excessive boron content in the cathode material and excessive residual lithium on the surface, leading to a decrease in both rate performance and cycle performance.

[0100] As can be seen from the comparison between Example 1 and Comparative Examples 1-3, the electrochemical performance of the high-nickel cathode material for lithium-ion batteries will be significantly reduced if boron doping and boron coating are not performed, or only boron doping is performed without boron coating, or only boron coating is performed without boron doping.

[0101] In summary, the preparation method of the dual-boron modified high-nickel cathode material for lithium-ion batteries provided by this invention is based on a co-precipitation method that can be prepared on a large scale for industrial applications. Boron is introduced in situ and its doping content is controlled. Then, a uniformly coated fast-ion conductor boron-containing compound is introduced. Through synergistic modification and control of the chemical composition and surface coating of the cathode material, the elemental and coating layer distribution uniformity, structural stability, electrochemical performance, and production efficiency of the lithium-ion battery cathode material are simultaneously improved. This invention utilizes a mature industrial co-precipitation process to prepare boron-doped lithium-ion battery cathode materials, featuring simple operation and low energy consumption. Furthermore, the prepared cathode material achieves atomic-level uniform distribution, excellent spherical particle dispersion, high tap density, and good product consistency and repeatability.

[0102] 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 high-nickel cathode material for lithium-ion batteries with dual boron modification, characterized in that, The preparation method includes the following steps: (1) A boron-containing ternary salt solution, a sodium hydroxide solution and a complexing agent solution are mixed and reacted. After solid-liquid separation of the reaction product, the resulting solid phase is dried to obtain an in-situ boron-doped hydroxide precursor. (2) The lithium source and the in-situ boron-doped hydroxide precursor obtained in step (1) are uniformly mixed, and an intermediate is obtained after the first sintering; the boron source and the obtained intermediate are uniformly mixed, and the high-nickel cathode material of the double boron modified lithium-ion battery is obtained after the second sintering.

2. The production method according to claim 1, characterized by, The metal concentration of the boron-containing ternary salt solution in step (1) is 0.5-2 mol / L.

3. The preparation method according to claim 1, characterized in that, The boron doping amount of the boron-containing ternary salt solution in step (1) is 1000-10000 ppm.

4. The production method according to claim 1, characterized by, The boron-containing ternary salt solution in step (1) is obtained by mixing nickel salt, cobalt salt, manganese salt, boron source and deionized water.

5. The preparation method according to claim 4, characterized in that, In step (1), the molar ratio of nickel, cobalt, manganese and boron in the boron-containing ternary salt solution is x:y:z:c, x+y+z+c=1, x≥0.6, y≤0.3, z≤0.2, c≤0.

03.

6. The preparation method according to claim 4, characterized in that, The nickel salt includes any one or a combination of at least two of nickel sulfate, nickel nitrate, or nickel chloride.

7. The preparation method according to claim 4, characterized in that, The cobalt salt includes any one or a combination of at least two of cobalt sulfate, cobalt nitrate, or cobalt chloride.

8. The preparation method according to claim 4, characterized in that, The manganese salt includes any one or a combination of at least two of manganese sulfate, manganese nitrate, or manganese chloride.

9. The method of claim 4, wherein, The boron source includes any one or a combination of at least two of boric acid, boron oxide, or sodium borate.

10. The method of claim 1, wherein, The concentration of the sodium hydroxide solution in step (1) is 6-10 mol / L.

11. The method of claim 1, wherein, The concentration of the complexing agent solution in step (1) is 0.1-3 mol / L.

12. The method of claim 1, wherein, The complexing agent in the complexing agent solution in step (1) includes any one or a combination of at least two of ammonia, oxalic acid, sodium oxalate or salicylic acid.

13. The method of claim 1, wherein, The mixing in step (1) involves simultaneously injecting the boron-containing ternary salt solution, sodium hydroxide solution, and complexing agent solution into the reactor and stirring at a rate of 250-400 rpm.

14. The method of claim 13, wherein, The flow rate of the boron-containing ternary salt solution is 7-9 L / h, the flow rate of the sodium hydroxide solution is 2-4 L / h, the flow rate of the complexing agent solution is 1-1.4 L / h, and the injection time into the reactor is 20-100 h.

15. The method of claim 1, wherein, The reaction in step (1) is carried out at a temperature of 30-60℃ for 45-50 hours.

16. The method of claim 1, wherein, The pH value of the solution in step (1) is controlled at 9-12.

17. The method of claim 1, wherein, Before the solid phase in step (1) is dried, a washing step is also included.

18. The method of claim 1, wherein, The drying temperature in step (1) is 80-200℃ and the drying time is 22-26h.

19. The method of claim 1, wherein, The lithium source in step (2) includes lithium hydroxide and / or lithium carbonate.

20. The method of claim 1, wherein, In step (2), the molar ratio of the lithium source to the in-situ boron-doped hydroxide precursor is 1.01-1.05 according to Li:(Ni+Co+Mn+B).

21. The method of claim 1, wherein, Step (2) The temperature of the first sintering is 800-1000℃ and the time is 10-20h.

22. The preparation method according to claim 1, characterized in that, The boron source in step (2) includes boric acid and / or boron oxide.

23. The method of claim 1, wherein, The mass of the boron source in step (2) is 0.8-1.2 wt% of the total mass of the boron source and the intermediate.

24. The method of claim 1, wherein, The second sintering temperature in step (2) is 200-500℃, and the time is 2-10h.

25. A dual boron-modified lithium-ion battery high-nickel cathode material, characterized in that, The double boron-modified high-nickel cathode material for lithium ion batteries is prepared by the method in any one of claims 1-24.

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