Lithium ion battery ultrahigh nickel positive electrode material and preparation method and application thereof

Abstract

The application discloses a kind of lithium ion battery ultra-high nickel positive electrode material and its preparation method and application, belong to lithium ion battery technical field.The ultra-high nickel positive electrode material of the present application is formed by hydrophobic transition metal diboride being coated on the surface of boron-doped lithium nickel cobalt manganese oxide positive electrode material.The surface of the ultra-high nickel active material of the present application is coated with thin and uniform transition metal diboride hydrophobic coating layer, transition metal diboride has high ion conduction capacity, and the obtained lithium ion battery has good cycle performance;Transition metal diboride can ensure hydrophobic characteristics, thereby ensuring the stability of lithium ion battery in the environment;Surface transition metal diboride and internal doped boron ion are synergistically modified, which significantly improves the cycle performance, rate performance and safety performance of the material in battery application.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, specifically to an ultra-high nickel cathode material for lithium-ion batteries, its preparation method, and its application. Background Technology

[0002] Lithium-ion batteries combine the advantages of high energy density, excellent electrochemical performance, and low self-discharge rate. Since their successful commercial application, they have been widely used in portable electronic devices, power tools, electric vehicles, and large-scale energy storage devices.

[0003] Ultra-high nickel polycrystalline materials exhibit advantages in long driving range in the electric vehicle field due to their high energy density and relatively low cobalt content. However, in actual industrial production, the low lithiation sintering temperature of ultra-high nickel materials results in a large amount of residual lithium on the surface of the sintered material. This leads to a higher pH value and increased water absorption in the slurry, which can severely damage PVDF during electrode slurry preparation, causing gelation and increasing coating difficulty. Furthermore, during battery charging and discharging, the residual lithium on the material surface is prone to side reactions with the electrolyte, generating gases such as CO2 and CO, posing safety risks.

[0004] To address the residual lithium issue, a water washing process is typically added after the sintering of ultra-high nickel polycrystalline materials to remove residual lithium from the material surface. However, during the water washing process, lithium oxide (Li₂) will form on the material surface. + / H + Exchange reactions cause degradation of the layered phases on the material surface, forming spinel and rock salt phases, thereby deteriorating the electrochemical performance of the material. Therefore, surface modification after water washing is essential. Currently, most methods employ metal oxides (TiO2, Al2O3, Y2O3, etc.) and LiMO coatings. x Compounds (M=B, Si, Al, In, etc.) are used, but conventional metal oxide coatings require high temperatures, resulting in high energy consumption and insufficient repair of surfaces damaged during washing.

[0005] Based on the above research, how to provide an ultra-high nickel battery cathode material with a uniform and thinner coating layer, high stability in the environment, high lithium-ion conductivity, and simple preparation method, which can improve the cycle performance and capacity of lithium-ion batteries, has become an urgent problem to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide an ultra-high nickel cathode material for lithium-ion batteries, its preparation method, and its application. This invention obtains boron-doped lithium nickel cobalt manganese oxide cathode material through high-temperature solid-state sintering, and coats the boron-doped lithium nickel cobalt manganese oxide cathode material with hydrophobic transition metal diborides through a liquid-phase coating method, thereby solving the problem of poor cycle stability of ultra-high nickel ternary cathode materials in the prior art.

[0007] The present invention first provides an ultra-high nickel cathode material, which is formed by coating a boron-doped lithium nickel cobalt manganese oxide cathode material with a hydrophobic transition metal diboride.

[0008] The synergistic modification of the ultra-high nickel cathode material by the surface transition metal diboride and the internal doping of boron ions significantly improves the cycle performance, rate performance and safety performance of the material in battery applications.

[0009] In the aforementioned ultra-high nickel cathode material, the hydrophobic transition metal diboride is at least one of hydrophobic TiB2, ZrB2, and HfB2.

[0010] In the aforementioned ultra-high nickel cathode material, the hydrophobic transition metal diboride is prepared by a high-temperature, high-pressure method and a surface modification method;

[0011] Specifically, the hydrophobic transition metal diboride is prepared by a method comprising the following steps: placing the transition metal diboride in a top press mold, pressing it into shape, wrapping it with a boron nitride crucible, then placing it in an assembly and placing it in a top press, pressurizing it to 3-7 GPa within 400-600 s, heating it to 1500-1700 ℃ within 10-20 s, processing it for 2-4 h, cooling it down within 10-20 s, and then depressurizing it down within 500-580 s; immersing the obtained blocky transition metal diboride in a 10-14 mol / L HCl solution for 15-17 h to obtain the hydrophobic transition metal diboride.

[0012] In the aforementioned ultra-high nickel cathode material, the thickness of the hydrophobic transition metal diboride coating layer is 1~15 nm, specifically 5 nm.

[0013] This invention also provides a method for preparing the above-mentioned ultra-high nickel cathode material, comprising the following steps:

[0014] (1) Boron-doped lithium nickel cobalt manganese oxide cathode material was prepared by high-temperature solid-state sintering process;

[0015] (2) Hydrophobic transition metal diborides were prepared using high temperature and high pressure methods and surface modification methods;

[0016] (3) The hydrophobic transition metal diboride is coated onto the surface of the boron-doped lithium nickel cobalt manganese oxide cathode material by liquid phase method to obtain the ultra-high nickel cathode material.

[0017] The preparation method of the above-mentioned ultra-high nickel cathode material specifically includes the following steps:

[0018] (1) The nickel cobalt manganese hydroxide precursor, lithium hydroxide and boron trioxide are ground and mixed, and sintered at high temperature to obtain boron-doped lithium cobalt manganese oxide cathode material;

[0019] (2) The transition metal diboride was placed in the mold of the top press, pressed into shape, wrapped in a boron nitride crucible, and then placed in the assembly and placed in the top press. The pressure was increased to 3-7 GPa within 400-600 s, the temperature was increased to 1500-1700 ℃ within 10-20 s, the treatment time was 2-4 h, the temperature was reduced within 10-20 s, and the pressure was reduced within 500-580 s. The obtained blocky transition metal diboride was soaked in 10-14 mol / L HCl solution for 15-17 h to obtain hydrophobic transition metal diboride.

[0020] (3) Disperse the hydrophobic transition metal diboride in a solvent; then mix it with the boron-doped lithium nickel cobalt manganese oxide cathode material, heat and stir to evaporate the solvent to obtain a mixture; place the mixture in an oxygen atmosphere for high-temperature sintering to obtain the ultra-high nickel cathode material.

[0021] In the above-mentioned method for preparing ultra-high nickel cathode material, in step (3), the mass ratio of the boron-doped lithium nickel cobalt manganese oxide cathode material to the hydrophobic transition metal diboride is 1:0.005~0.05, specifically 1:0.005, 1:0.03 or 1:0.5.

[0022] In the above-mentioned method for preparing ultra-high nickel cathode material, in step (1), the molecular formula of the nickel-cobalt-manganese hydroxide precursor is Ni. x Co y Mn (1-x-y) (OH)₂, where 0.9 < x ≤ 0.95, 0.05 ≤ y ≤ 0.1; specifically, it can be Ni 0.93 Co 0.06 Mn 0.01 (OH)2;

[0023] The molar ratio of the nickel-cobalt-manganese hydroxide precursor, lithium hydroxide, and boron trioxide is 1:1.01~1.1:0.01~0.03, specifically 1:1.02:0.02;

[0024] In step (2), the transition metal diboride is at least one of TiB2, ZrB2, and HfB2;

[0025] In step (3), the solvent is at least one of anhydrous ethanol, ethanol solution and acetone;

[0026] The mass-to-volume ratio of the hydrophobic transition metal diboride to the solvent is 1:1000~1:2000 g / mL.

[0027] In the above preparation method, in step (1), the high-temperature sintering is carried out in an oxygen atmosphere; the high-temperature sintering is to first hold at 500~650 ℃ for 2~8 h, and then raise the temperature to 780~820 ℃ and hold for 12~16 h.

[0028] Specifically, the high-temperature sintering involves first holding at 500 ℃ for 5 h, and then raising the temperature to 790 ℃ and holding for 14 h.

[0029] In step (3), the temperature for evaporating the solvent is 65~80 ℃, specifically 75 ℃;

[0030] The high-temperature sintering temperature is 550~650 ℃, specifically 600 ℃; the time is 2~8 h, specifically 5 h.

[0031] The present invention further provides an ultra-high nickel cathode material prepared by the above preparation method.

[0032] Finally, the application of the aforementioned ultra-high nickel cathode material in the preparation of lithium-ion battery cathodes also falls within the scope of protection of this invention.

[0033] Compared with the prior art, the present invention has the following advantages:

[0034] (1) The present invention uses boron doping. The high bond energy of BO bonds can effectively improve the stability of the crystal structure, effectively alleviate polarization, and improve the electrochemical cycling performance of the material.

[0035] (2) The ultra-high nickel active material of the present invention is coated with a thin and uniform hydrophobic coating layer of transition metal diboride. The transition metal diboride has high ion conductivity, and the resulting lithium-ion battery has good cycle performance. The transition metal diboride can ensure hydrophobic properties, thereby ensuring the stability of the lithium-ion battery in the environment.

[0036] (3) The synergistic modification of the surface transition metal diboride and the internal doped boron ions of the present invention significantly improves the cycle performance, rate performance and safety performance of the material in battery applications;

[0037] (4) The present invention uses high-temperature solid-phase sintering for doping and liquid-phase coating for coating. The preparation process is simple and the electrical performance is significantly improved. Attached Figure Description

[0038] Figure 1 The contact angle between the ultra-high nickel cathode material prepared in Example 2 and the solvent is shown.

[0039] Figure 2 The contact angle between the unmodified ultra-high nickel cathode material prepared in Comparative Example 1 and the solvent.

[0040] Figure 3 The coin cell DSC images are of the ultra-high nickel cathode materials prepared in Example 2 and Comparative Example 1. Detailed Implementation

[0041] The present invention will be further described in detail below with reference to specific embodiments. The embodiments given are only for illustrating the present invention and are not intended to limit the scope of the present invention.

[0042] Unless otherwise specified, the experimental methods described in the following examples are conventional methods.

[0043] In the quantitative experiments in the following examples, three replicate experiments were set up, and the average value of the results was taken.

[0044] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0045] Unless otherwise specified in the following embodiments, any techniques or conditions not described herein may be performed in accordance with the techniques or conditions described in the literature in this field or in accordance with the product manual.

[0046] The electrochemical performance testing methods in the following examples are as follows:

[0047] Using the positive electrode material sheets from the examples and comparative examples as the positive electrode, lithium metal sheets as the negative electrode, polypropylene microporous membranes as the separator, and 1 mol / L LiPF6 as the electrolyte (a mixed solvent of EC, DEC, and DMC in a volume ratio of 1:1:1), a CR2032 type battery was fabricated in an argon-filled glove box. Constant current charge-discharge tests were conducted at room temperature at 0.2C, with charge-discharge cutoff voltages ranging from 2.8 V to 4.35 V.

[0048] Example 1

[0049] (1) According to the commercially available precursor Ni 0.93 Co 0.06 Mn 0.01 The mixture of (OH)2, LiOH·H2O, and B2O3 in a molar ratio of 1:1.02:0.02 was mechanically ground and then placed in a tube furnace for high-temperature calcination in an oxygen atmosphere. The mixture was pre-sintered at 500°C for 5 h, then heated to 790°C for 14 h, and finally cooled to obtain boron-doped lithium nickel cobalt manganese oxide cathode material.

[0050] (2) The commercially purchased HfB2 was placed in the mold of a six-sided press (model: 6×14400 KN), pressed into shape, and then wrapped with a boron nitride crucible. The mixture was then placed in the press and pressurized to 5 GPa within 480 s, heated to 1600 ℃ within 15 s, and the time was 3 h. After heating, the temperature was reduced within 15 s, and the pressure was reduced within 540 s. The sample was then removed, and the boron nitride wrapped on the sample was carefully removed. The resulting block HfB2 was soaked in 12 mol / L HCl solution for 16 h, washed with anhydrous ethanol, filtered, and dried to obtain hydrophobic HfB2.

[0051] (3) Weigh 0.03 g of the hydrophobic HfB2 prepared in step (2) and dissolve it in 50 mL of anhydrous ethanol. Sonicate for 10 min, then transfer it to a magnetic stirrer and stir at 3500 r / min. Add 1 g of the boron-doped nickel cobalt manganese oxide cathode material prepared in step (1) and continue stirring for 30 min. Then, raise the temperature to 75 °C and continue stirring until the anhydrous ethanol is completely evaporated. Finally, heat the resulting mixture to 600 °C at a heating rate of 2 °C / min under an O2 atmosphere and sinter for 5 h to obtain an ultra-high nickel cathode material with a coating thickness of 5 nm.

[0052] Example 2-3

[0053] Except for the different amounts of hydrophobic HfB2 in step (3), the amount in Example 2 was 0.005 g and the amount in Example 3 was 0.5 g. All other synthesis conditions were the same as in Example 1, and ultra-high nickel cathode material was obtained.

[0054] Comparative Example 1 (Unmodified ultra-high nickel cathode material)

[0055] According to the commercially available precursor Ni 0.93 Co 0.06 Mn 0.01 (OH)2 and LiOH·H2O are mixed in a molar ratio of 1:1.02, mechanically ground, and then placed in a tube furnace for high-temperature calcination in an oxygen atmosphere. The mixture is pre-sintered at 500 °C for 5 h, then heated to 790 °C for 14 h, and cooled to obtain the unmodified ultra-high nickel cathode material.

[0056] Comparative Example 2 (Boron-doped ultra-high nickel cathode material)

[0057] According to the commercially available precursor Ni 0.93 Co 0.06 Mn 0.01The mixture of (OH)2, LiOH·H2O, and B2O3 in a molar ratio of 1:1.02:0.01 was mechanically ground and then placed in a tube furnace for high-temperature calcination in an oxygen atmosphere. The mixture was pre-sintered at 500 °C for 5 h, then heated to 790 °C for 14 h, and finally cooled to obtain boron-doped ultra-high nickel cathode material.

[0058] Comparative Example 3 (HfB2-coated ultra-high nickel cathode material)

[0059] In addition to using LiOH·H2O and precursor Ni in step (1) 0.93 Co 0.06 Mn 0.01 Except for mechanical grinding of (OH)2 in a molar ratio of 1.02:1, all other synthesis conditions were the same as in Example 1, resulting in HfB2-coated ultra-high nickel cathode material.

[0060] Table 1. Performance of the ultra-high nickel cathode materials prepared in the examples and comparative examples.

[0061]

[0062] Table 1 summarizes the electrical performance of button batteries prepared from the cathode materials of the examples and comparative examples. As can be seen from Table 1, the ultra-high nickel cathode materials prepared in Examples 1-3, compared with the unmodified ultra-high nickel cathode material of Comparative Example 1, the boron-doped ultra-high nickel cathode material of Comparative Example 2, and the HfB2-coated ultra-high nickel cathode material of Comparative Example 3, not only have an advantage in initial discharge specific capacity but also better capacity retention after 100 cycles. Example 2 is the best example, demonstrating that the ultra-high nickel cathode material of the present invention has better electrochemical performance.

[0063] Figure 1 and Figure 2 The figures show the contact angles of the ultra-high nickel cathode materials prepared in Example 2 and Comparative Example 1 with the solvent (water), respectively. As can be seen from the figures, the contact angle of the unmodified ultra-high nickel cathode material in Comparative Example 1 is 60.3º, and the contact angle of the ultra-high nickel cathode material prepared in Example 2 is 120.5º, indicating that the cathode material has been transformed from hydrophilic to hydrophobic through boron doping and coating.

[0064] Figure 3 The figures show the coin cell DSC diagrams of the ultra-high nickel cathode materials prepared in Example 2 and Comparative Example 1, with the coin cell voltage ranging from 2.8 to 4.35 V. It is evident from the figures that the peak exothermic temperature of the sample in Example 2 is 224.58 °C, which is 6.84 °C higher than that of the undoped sample (Comparative Example 1), indicating that the solution of the present invention can improve the safety performance of ultra-high nickel materials.

Claims

1. A method for preparing an ultra-high nickel cathode material, comprising the following steps: (1) The nickel cobalt manganese hydroxide precursor, lithium hydroxide and boron trioxide are ground and mixed, and sintered at high temperature to obtain boron-doped lithium cobalt manganese oxide cathode material; (2) The transition metal diboride was placed in the mold of the top press, pressed into shape, wrapped in a boron nitride crucible, and then placed in the assembly and placed in the top press. The pressure was increased to 3-7 GPa within 400-600 s, the temperature was increased to 1500-1700 ℃ within 10-20 s, the treatment time was 2-4 h, the temperature was reduced within 10-20 s, and the pressure was reduced within 500-580 s. The obtained blocky transition metal diboride was soaked in 10-14 mol / L HCl solution for 15-17 h to obtain hydrophobic transition metal diboride. In step (2), the transition metal diboride is at least one of TiB2, ZrB2, and HfB2; (3) Disperse the hydrophobic transition metal diboride in a solvent; then mix it with the boron-doped lithium nickel cobalt manganese oxide cathode material, heat and stir to evaporate the solvent to obtain a mixture; place the mixture in an oxygen atmosphere for high-temperature sintering to obtain the ultra-high nickel cathode material.

2. The method for preparing the ultra-high nickel cathode material according to claim 1, characterized in that: In step (3), the mass ratio of the boron-doped lithium nickel cobalt manganese oxide cathode material to the transition metal diboride is 1:0.005~0.

05.

3. The method for preparing the ultra-high nickel cathode material according to claim 1, characterized in that: In step (1), the molecular formula of the nickel-cobalt-manganese hydroxide precursor is Ni x Co y Mn (1-x-y) (OH)2, where 0.9 < x ≤ 0.95, 0.05 ≤ y ≤ 0.1; The molar ratio of the nickel-cobalt-manganese hydroxide precursor, lithium hydroxide, and boron trioxide is 1:1.01~1.1:0.01~0.03; In step (3), the solvent is at least one of anhydrous ethanol, ethanol solution and acetone; The mass-to-volume ratio of the hydrophobic transition metal diboride to the solvent is 1:1000~1:2000 g / mL.

4. The method for preparing the ultra-high nickel cathode material according to claim 3, characterized in that: In step (1), the molecular formula of the nickel-cobalt-manganese hydroxide precursor is Ni 0.93 Co 0.06 Mn 0.01 (OH)2.

5. The preparation method according to claim 1, characterized in that: In step (1), the high-temperature sintering is carried out in an oxygen atmosphere; the high-temperature sintering is to first hold at 500~650 ℃ for 2~8 h, and then raise the temperature to 780~820 ℃ and hold for 12~16 h. In step (3), the temperature for evaporating the solvent is 65~80 ℃; The high-temperature sintering temperature is 550~650 ℃, and the time is 2~8 h.

6. The ultra-high nickel cathode material prepared by the preparation method according to any one of claims 1-5.

7. The application of the ultra-high nickel cathode material according to claim 6 in the preparation of lithium-ion battery cathodes.

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