Ultrahigh-nickel positive electrode material for lithium ion battery and preparation method and application of ultrahigh-nickel positive electrode material

Abstract

The invention discloses a lithium ion battery ultrahigh nickel positive electrode material and a preparation method and application thereof, and belongs to the technical field of lithium ion batteries. The ultrahigh nickel positive electrode material is formed by coating the surface of a boron-doped nickel cobalt lithium manganate positive electrode material with a hydrophobic transition metal diboride. The surface of the ultra-high nickel active material is coated with the thin and uniform transition metal diboride hydrophobic coating layer, transition metal diboride has high ionic conductivity, and the obtained lithium ion battery has good cycle performance; the transition metal diboride can ensure the hydrophobic property, so that the stability of the lithium ion battery in the environment is ensured; the surface transition metal diboride and internally doped boron ions are synergistically modified, so that the cycle performance, the rate capability and the safety performance of the material in battery application are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to an ultra-high nickel positive electrode material for lithium ion batteries and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have 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 have shown the advantage of long battery life in the field of electric vehicles due to their high energy density and relatively low cobalt content. However, in the actual industrial production process, due to the low temperature of the lithium sintering of ultra-high nickel materials, there will be a large amount of residual lithium on the surface of the sintered material, which will cause the pH value of the slurry to be high and easy to absorb water. In severe cases, it will destroy PVDF during the preparation of electrode slurry, causing gelation and increasing the difficulty of coating. In addition, during the battery charging and discharging process, the residual lithium on the surface of the material is prone to side reactions with the electrolyte to generate gases such as CO2 and CO, causing safety problems.

[0004] In order to solve the problem of residual lithium, a water washing process is usually added after the sintering of ultra-high nickel polycrystalline materials to remove the residual lithium on the surface of the material. However, during the water washing process, Li + / H + The exchange reaction causes the layered phase on the surface of the material to degenerate, forming spinel and rock salt phases, thereby deteriorating the electrochemical properties of the material. Therefore, it is essential to coat and modify the surface of the material after washing. At present, most of the metal oxides (TiO2, Al2O3, Y2O3, etc.), LiMO x Compounds (M=B, Si, Al, In, etc.), however, conventional metal oxide coating has a high temperature, which not only consumes a lot of energy but also cannot fully repair the surface damaged by water washing.

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

[0006] The purpose of the present invention is to provide an ultra-high nickel positive electrode material for lithium-ion batteries and a preparation method and application thereof. The present invention obtains a boron-doped nickel cobalt manganese oxide positive electrode material by high-temperature solid phase sintering, and coats a hydrophobic transition metal diboride on the boron-doped nickel cobalt manganese oxide positive electrode material by a liquid phase coating method, so as to solve the problem of poor cycle stability of ultra-high nickel ternary positive electrode materials in the prior art.

[0007] The present invention first provides an ultra-high nickel positive electrode material, which is formed by coating a hydrophobic transition metal diboride on the surface of a boron-doped nickel cobalt manganese oxide positive electrode material.

[0008] The synergistic modification of the transition metal diboride on the surface of the ultra-high nickel positive electrode material of the present invention and the boron ions doped inside significantly improves the cycle performance, rate performance and safety performance of the material in battery applications.

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

[0010] In the above-mentioned ultra-high nickel positive electrode material, the hydrophobic transition metal diboride is prepared by a high temperature and high pressure method and a surface modification method; 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, wrapping it with a boron nitride crucible after compression molding, then placing it in an assembly and placing it in a top press, pressurizing it to 3-7 GPa within 400-600 seconds, heating it to 1500-1700°C within 10-20 seconds, treating it for 2-4 hours, cooling it within 10-20 seconds, and then reducing the pressure within 500-580 seconds; soaking the obtained bulk transition metal diboride in a 10-14 mol / L HCl solution for 15-17 hours to obtain the hydrophobic transition metal diboride.

[0011] In the above-mentioned ultra-high nickel positive electrode material, the thickness of the hydrophobic transition metal diboride coating layer is 1-15 nm, specifically 5 nm.

[0012] The present invention also provides a method for preparing the above-mentioned ultra-high nickel positive electrode material, comprising the following steps: (1) Preparation of boron-doped lithium nickel cobalt manganese oxide cathode material using high temperature solid phase sintering process; (2) Preparation of hydrophobic transition metal diborides using high temperature and high pressure methods and surface modification methods; (3) The hydrophobic transition metal diboride is coated on the surface of the boron-doped nickel cobalt manganese oxide positive electrode material by a liquid phase method to obtain the ultra-high nickel positive electrode material.

[0013] The preparation method of the above-mentioned ultra-high nickel positive electrode material specifically comprises the following steps: (1) grinding and mixing a nickel cobalt manganese hydroxide precursor, lithium hydroxide and boron trioxide, and sintering at high temperature to obtain a boron-doped nickel cobalt manganese oxide positive electrode material; (2) placing the transition metal diboride into a top press mold, and wrapping it with a boron nitride crucible after pressing it into shape. Then placing it in an assembly and placing it in a top press, pressurizing it to 3-7 GPa within 400-600 seconds, heating it to 1500-1700 °C within 10-20 seconds, and treating it for 2-4 hours. Then, the temperature is lowered within 10-20 seconds, and the pressure is lowered within 500-580 seconds. The obtained bulk transition metal diboride is immersed in a 10-14 mol / L HCl solution for 15-17 hours to obtain a hydrophobic transition metal diboride. (3) dispersing the hydrophobic transition metal diboride in a solvent; then mixing the hydrophobic transition metal diboride with the boron-doped nickel cobalt manganese oxide positive electrode material, heating and stirring to evaporate the solvent to obtain a mixture; placing the mixture in an oxygen atmosphere and sintering at a high temperature to obtain the ultra-high nickel positive electrode material.

[0014] In the above-mentioned method for preparing ultra-high nickel positive electrode material, in step (3), the mass ratio of the boron-doped nickel cobalt manganese oxide positive electrode material to the hydrophobic transition metal diboride is 1:0.005-0.05, specifically 1:0.005, 1:0.03 or 1:0.5.

[0015] In the above-mentioned method for preparing the ultra-high nickel positive electrode 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, wherein 0.9<x≤0.95, 0.05≤y≤0.1; specifically, Ni 0.93 Co 0.06 Mn 0.01 (OH)2; 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; In step (2), the transition metal diboride is at least one of TiB2, ZrB2 and HfB2; In step (3), the solvent is at least one of anhydrous ethanol, ethanol solution and acetone; The mass volume ratio of the hydrophobic transition metal diboride to the solvent is 1:1000-1:2000 g / mL.

[0016] In the above-mentioned preparation method, in step (1), the high-temperature sintering is carried out in an oxygen atmosphere; the high-temperature sintering is firstly kept at 500-650°C for 2-8 hours, and then heated to 780-820°C for 12-16 hours; Specifically, the high temperature sintering is firstly kept at 500°C for 5 hours, and then heated to 790°C for 14 hours; In step (3), the temperature of evaporating the solvent is 65-80°C, specifically 75°C; The high temperature sintering temperature is 550-650°C, specifically 600°C; the sintering time is 2-8 hours, specifically 5 hours.

[0017] The present invention further provides an ultra-high nickel positive electrode material prepared by the above preparation method.

[0018] Finally, the application of the above-mentioned ultra-high nickel positive electrode material in the preparation of lithium-ion battery positive electrodes also falls within the protection scope of the present invention.

[0019] Compared with the prior art, the present invention has the following advantages: (1) The present invention adopts boron doping, and the high bond energy BO bond can effectively improve the stability of the crystal structure, effectively alleviate polarization, and improve the electrochemical cycle performance of the material; (2) The surface of the ultra-high nickel active material of the present invention is coated with a relatively thin and uniform transition metal diboride hydrophobic coating layer. The transition metal diboride has high ion conductivity, and the obtained 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; (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; (4) The present invention adopts a high-temperature solid-phase sintering method for doping and a liquid-phase method for coating. The preparation process is simple and the electrical performance is significantly improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The contact angle between the ultra-high nickel positive electrode material prepared in Example 2 and the solvent.

[0021] Figure 2 The contact angle between the unmodified ultra-high nickel positive electrode material prepared in Comparative Example 1 and the solvent.

[0022] Figure 3 The DSC graphs of the ultra-high nickel positive electrode materials prepared in Example 2 and Comparative Example 1 are shown. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with specific embodiments. The given examples are only for illustrating the present invention, but not for limiting the scope of the present invention.

[0024] The experimental methods in the following examples are all conventional methods unless otherwise specified.

[0025] The quantitative tests in the following examples were all repeated three times, and the results were averaged.

[0026] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0027] If no specific techniques or conditions are specified in the following examples, they can be carried out according to the techniques or conditions described in the literature in the field or according to the product instructions.

[0028] The electrochemical performance test method in the following examples is as follows: A CR2032 battery was prepared in a glove box filled with argon gas, using the positive electrode material pole piece of the embodiment and the comparative example as the positive electrode, a metal lithium sheet as the negative electrode, a polypropylene microporous membrane as the separator, and 1 mol / L LiPF6 as the electrolyte (the solvent is a mixed solvent of EC, DEC and DMC, and the volume ratio is 1:1:1). A 0.2C constant current charge and discharge test was carried out at room temperature, and the charge and discharge cut-off voltage was 2.8 V-4.35 V.

[0029] Example 1 (1) According to the commercial precursor Ni 0.93 Co 0.06 Mn 0.01 (OH)2, LiOH·H2O, and B2O3 are mixed in a molar ratio of 1:1.02:0.02, and the mixture is placed in a tubular furnace after mechanical grinding, and calcined at a high temperature in an oxygen atmosphere, pre-sintered at 500°C for 5 h, then heated to 790°C for 14 h, and cooled to obtain a boron-doped nickel cobalt manganese oxide positive electrode material.

[0030] (2) The commercially available HfB2 was placed in the mold of a six-sided top press (model: 6×14400 KN). After pressing and forming, the HfB2 was wrapped in a boron nitride crucible, placed in an assembly and placed in a press. The pressure was increased to 5 GPa within 480 s, and the temperature was raised to 1600 °C within 15 s for 3 h. After the heating was completed, the temperature was lowered within 15 s, and the pressure was lowered within 540 s. The sample was then taken out and the boron nitride wrapped on the sample was carefully removed. The obtained block HfB2 was immersed in 12 mol / L HCl solution for 16 h, washed with anhydrous ethanol, filtered, and dried to obtain hydrophobic HfB2.

[0031] (3) Weigh 0.03 g of the hydrophobic HfB2 prepared in step (2) and dissolve it in 50 mL of anhydrous ethanol. Ultrasonicate for 10 min, then transfer it to a magnetic stirring device and stir it at 3500 r / min. Add 1 g of the boron-doped nickel cobalt manganese oxide positive electrode 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 obtained mixture to 600 °C at a heating rate of 2 °C / min in an O2 atmosphere, and sinter for 5 h to obtain an ultra-high nickel positive electrode material with a coating layer thickness of 5 nm.

[0032] Example 2-3 Except for the different amounts of hydrophobic HfB2 in step (3), which is 0.005 g in Example 2 and 0.5 g in Example 3, the other synthesis conditions are the same as those in Example 1 to obtain an ultra-high nickel positive electrode material.

[0033] Comparative Example 1 (Unmodified Ultra-High Nickel Cathode Material) According to the commercial 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, and after mechanical grinding, the mixture is placed in a tubular furnace and calcined at a high temperature in an oxygen atmosphere. The pre-sintering is carried out at 500°C for 5 hours, and then the temperature is raised to 790°C for 14 hours. After cooling, the unmodified ultra-high nickel positive electrode material is obtained.

[0034] Comparative Example 2 (boron-doped ultra-high nickel positive electrode material) According to the commercial precursor Ni 0.93 Co 0.06 Mn 0.01 (OH)2, LiOH·H2O, and B2O3 are mixed in a molar ratio of 1:1.02:0.01, and after mechanical grinding, the mixture is placed in a tubular furnace and calcined at a high temperature in an oxygen atmosphere. The pre-sintering is carried out at 500°C for 5 hours, and then the temperature is raised to 790°C for 14 hours. After cooling, a boron-doped ultra-high nickel positive electrode material is obtained.

[0035] Comparative Example 3 (HfB2-coated ultra-high nickel cathode material) In addition to the use of LiOH·H2O and precursor Ni in step (1), 0.93 Co 0.06 Mn 0.01 Except for mechanical grinding with a (OH)2 molar ratio of 1.02:1, the other synthesis conditions are the same as those in Example 1 to obtain an HfB2-coated ultra-high nickel positive electrode material.

[0036] Table 1 Performance of ultra-high nickel positive electrode materials prepared in Examples and Comparative Examples

[0037] Table 1 is a summary table of the electrical properties of button cells prepared from the positive electrode material pole pieces prepared in the embodiments and comparative examples. It can be seen from Table 1 that the ultra-high nickel positive electrode materials prepared in Examples 1-3 have advantages in the first discharge specific capacity compared with the unmodified ultra-high nickel positive electrode material in Comparative Example 1, the boron-doped ultra-high nickel positive electrode material in Comparative Example 2, and the HfB2-coated ultra-high nickel positive electrode material in Comparative Example 3, and have good capacity retention after 100 cycles. Example 2 is the best example, indicating that the ultra-high nickel positive electrode material of the present invention has better electrochemical performance.

[0038] Figure 1 and Figure 2 They are the contact angles of the ultra-high nickel positive electrode materials prepared in Example 2 and Comparative Example 1 with the solvent (water), respectively; as can be seen from the figure, the contact angle of the unmodified ultra-high nickel positive electrode material in Comparative Example 1 is 60.3°, and the contact angle of the ultra-high nickel positive electrode material prepared in Example 2 is 120.5°, indicating that the transformation of the positive electrode material from hydrophilicity to hydrophobicity is achieved by boron doping and coating.

[0039] Figure 3 The buckling DSC graphs of the ultra-high nickel positive electrode materials prepared in Example 2 and Comparative Example 1 have a buckling voltage range of 2.8-4.35 V. It can be clearly seen from the figure 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 scheme of the present invention can improve the safety performance of ultra-high nickel materials.

Claims

1. An ultra-high nickel positive electrode material, characterized in that: The ultra-high nickel positive electrode material is formed by coating a hydrophobic transition metal diboride on the surface of a boron-doped nickel cobalt manganese oxide positive electrode material.

2. The ultra-high nickel positive electrode material according to claim 1, characterized in that: The hydrophobic transition metal diboride is at least one of hydrophobic TiB2, ZrB2 and HfB2.

3. The ultra-high nickel positive electrode material according to claim 1 or 2, characterized in that: The hydrophobic transition metal diboride is prepared by a high temperature and high pressure method and a surface modification method; 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, wrapping it with a boron nitride crucible after compression molding, then placing it in an assembly and placing it in a top press, pressurizing it to 3-7 GPa within 400-600 seconds, heating it to 1500-1700°C within 10-20 seconds, treating it for 2-4 hours, cooling it within 10-20 seconds, and then reducing the pressure within 500-580 seconds; soaking the obtained bulk transition metal diboride in a 10-14 mol / L HCl solution for 15-17 hours to obtain the hydrophobic transition metal diboride.

4. The method for preparing the ultra-high nickel positive electrode material according to any one of claims 1 to 3, comprising the following steps: (1) Preparation of boron-doped lithium nickel cobalt manganese oxide cathode material using high temperature solid phase sintering process; (2) Preparation of hydrophobic transition metal diborides using high temperature and high pressure methods and surface modification methods; (3) The hydrophobic transition metal diboride is coated on the surface of the boron-doped nickel cobalt manganese oxide positive electrode material by a liquid phase method to obtain the ultra-high nickel positive electrode material.

5. The method for preparing the ultra-high nickel positive electrode material according to claim 4, characterized in that: The preparation method comprises the following steps: (1) grinding and mixing a nickel cobalt manganese hydroxide precursor, lithium hydroxide and boron trioxide, and sintering at high temperature to obtain a boron-doped nickel cobalt manganese oxide positive electrode material; (2) placing the transition metal diboride into a top press mold, and wrapping it with a boron nitride crucible after pressing it into shape. Then placing it in an assembly and placing it in a top press, pressurizing it to 3-7 GPa within 400-600 seconds, heating it to 1500-1700 °C within 10-20 seconds, and treating it for 2-4 hours. Then, the temperature is lowered within 10-20 seconds, and the pressure is lowered within 500-580 seconds. The obtained bulk transition metal diboride is immersed in a 10-14 mol / L HCl solution for 15-17 hours to obtain a hydrophobic transition metal diboride. (3) dispersing the hydrophobic transition metal diboride in a solvent; then mixing the hydrophobic transition metal diboride with the boron-doped nickel cobalt manganese oxide positive electrode material, heating and stirring to evaporate the solvent to obtain a mixture; placing the mixture in an oxygen atmosphere and sintering at a high temperature to obtain the ultra-high nickel positive electrode material.

6. The method for preparing the ultra-high nickel positive electrode material according to claim 4 or 5, characterized in that: In step (3), the mass ratio of the boron-doped nickel cobalt lithium manganese oxide positive electrode material to the transition metal diboride is 1:0.005-0.

05.

7. The method for preparing the ultra-high nickel positive electrode material according to claim 5, 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, wherein 0.9<x≤0.95, 0.05≤y≤0.1; specifically, Ni 0.93 Co 0.06 Mn 0.01 (OH)2; 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 (2), the transition metal diboride is at least one of TiB2, ZrB2 and HfB2; In step (3), the solvent is at least one of anhydrous ethanol, ethanol solution and acetone; The mass volume ratio of the hydrophobic transition metal diboride and the solvent is 1:1000-1:2000 g / mL.

8. The preparation method according to claim 5, characterized in that: In step (1), the high temperature sintering is carried out in an oxygen atmosphere; the high temperature sintering is firstly kept at 500-650°C for 2-8 hours, and then heated to 780-820°C for 12-16 hours; In step (3), the temperature of evaporating the solvent is 65-80°C; The high temperature sintering temperature is 550-650°C and the time is 2-8 hours.

9. The ultra-high nickel positive electrode material prepared by the preparation method according to any one of claims 4 to 8.

10. Use of the ultra-high nickel positive electrode material according to claim 9 in preparing a positive electrode for a lithium-ion battery.

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