Tungsten-boron nickel-rich positive electrode material and preparation method and application thereof

Abstract

The invention belongs to the technical field of positive electrode materials, and particularly relates to a tungsten-boron nickel-rich positive electrode material and a preparation method and application thereof. The invention provides a tungsten-boron nickel-rich positive electrode material preparation method, which comprises: (1) mixing a nickel source and a tungsten source, and carrying out a reaction to prepare a tungsten-substituted nickel-rich precursor; (2) mixing the tungsten-substituted nickel-rich precursor, a lithium source and an additive, performing first sintering, adding a boron source, and performing second sintering to obtain a tungsten-boron nickel-rich positive electrode material; the particle size of the tungsten-substituted nickel-rich precursor is 8-12 [mu] m. The tungsten-boron nickel-rich positive electrode material prepared by the invention has excellent cycling stability and specific discharge capacity.

Description

Technical Field

[0001] The present invention belongs to the technical field of positive electrode materials, and in particular relates to a tungsten-boron nickel-rich positive electrode material and a preparation method and application thereof. Background Art

[0002] Lithium-ion batteries have the advantages of high energy density, long life, fast charge and discharge, and no memory effect. Nickel-based layered oxides are considered to be one of the most promising positive electrode materials for lithium-ion batteries due to their high energy density and safety. x Co y Mn 1-x-y O2(NCM) and LiNi x Co y Al 1-x-y O2(NCA) has been used in the field of electric vehicles.

[0003] Studies have shown that the energy density of nickel-based layered oxides as positive electrode materials is positively correlated with their nickel content. In the prior art, the nickel content x is often increased to 0.9 or even higher to improve the energy density of the positive electrode material. However, the increase in nickel content will cause H2-H3 phase change, oxygen loss and lithium-nickel mixing, resulting in reduced cycle stability of the positive electrode material. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is to overcome the defects of the prior art that when increasing the energy density and increasing the nickel content, H2-H3 phase transition, oxygen loss and lithium-nickel mixing will be aggravated, resulting in reduced cycle stability of the positive electrode material, thereby providing a tungsten-boron nickel-rich positive electrode material and its preparation method and application.

[0005] To this end, the present invention provides the following technical solutions.

[0006] The present invention provides a method for preparing a tungsten-boron nickel-rich positive electrode material, comprising the following steps:

[0007] (1) mixing a nickel source and a tungsten source, reacting them, and preparing a tungsten-substituted nickel-rich precursor;

[0008] (2) mixing a tungsten-substituted nickel-rich precursor, a lithium source and an additive, sintering the mixture for the first time, adding a boron source, and sintering the mixture for the second time to obtain a tungsten-boron-rich nickel-rich positive electrode material;

[0009] The particle size of the tungsten-substituted nickel-rich precursor is 8-12 μm.

[0010] In an optional embodiment, the nickel source includes at least one of nickel sulfate, nickel chloride and nickel trioxide;

[0011] In an optional embodiment, the tungsten source includes at least one of tungsten hydroxide, tungsten chloride and sodium tungstate;

[0012] In an optional embodiment, the molar ratio of the nickel element in the nickel source to the tungsten element in the tungsten source is (92-95):(5-8).

[0013] The molar ratio of the nickel element in the nickel source to the tungsten element in the tungsten source is 93:7, 92:8, 95:5, etc.

[0014] In the step (1), the mixing further comprises adding an alkaline solution; the alkaline solution comprises ammonia and sodium hydroxide, wherein the ammonia solution can also act as a chelating agent.

[0015] In an optional embodiment, the specific steps of the reaction include: stirring, controlling the ammonia value of the reaction system to 5.0-7.6 g / L, and controlling the pH value of the reaction system to 9-12;

[0016] Preferably, the stirring speed is 600-1000 rpm.

[0017] The step (1), after the reaction, further comprises washing, filtering, drying, and sieving to remove magnetism to obtain a tungsten-substituted nickel-rich precursor;

[0018] In an optional embodiment, the drying temperature is 100-120°C;

[0019] In an optional embodiment, the reaction is carried out under an inert gas;

[0020] In an optional embodiment, the reaction temperature is 70-80°C;

[0021] In an optional embodiment, the reaction time is 6-9 hours.

[0022] In an optional embodiment, the ratio of the total molar amount of nickel and tungsten in the tungsten-substituted nickel-rich precursor to the molar amount of lithium in the lithium source is 1:(1.02-1.06);

[0023] In an optional embodiment, the ratio of the total molar amount of nickel element and tungsten element in the tungsten-substituted nickel-rich precursor to the molar amount of the additive is 1:(0.003-0.008);

[0024] In an optional embodiment, the lithium source includes at least one of lithium hydroxide and lithium carbonate;

[0025] In an optional embodiment, the additive includes at least one of aluminum oxide, aluminum hydroxide and aluminum chloride;

[0026] In an optional embodiment, the boron source includes at least one of boric acid, sodium borate and boron oxide.

[0027] In an optional embodiment, the temperature of the first sintering is 700-760°C;

[0028] In an optional embodiment, the first sintering is performed in an oxygen atmosphere;

[0029] In an optional embodiment, the first sintering time is 8-12 hours.

[0030] In an optional embodiment, after the first sintering, the method further comprises: mixing the obtained sintered material with water, filtering, and drying;

[0031] Preferably, the ratio of the mass of the fuel to the mass of water is 1:(0.6-1);

[0032] Preferably, based on the mass of the dried product, the added amount of the boron source is 0.1-0.3 wt %.

[0033] In an optional embodiment, the drying temperature is 120-150°C;

[0034] In an optional embodiment, the second sintering temperature is 500-600°C;

[0035] In an optional embodiment, the second sintering is performed in an oxygen atmosphere;

[0036] In an optional embodiment, the second sintering time is 4-6 hours.

[0037] In an optional embodiment, during the first sintering, the flow rate of oxygen is 0.2-0.6 L / min;

[0038] In an optional embodiment, during the second sintering, the flow rate of oxygen is 0.2-0.6 L / min;

[0039] The invention also provides a tungsten-boron nickel-rich positive electrode material prepared by the preparation method.

[0040] The present invention also provides an application of the tungsten-boron nickel-rich positive electrode material prepared by the preparation method in a lithium-ion battery.

[0041] The technical solution of the present invention has the following advantages:

[0042] 1. The preparation method of the tungsten-boron nickel-rich positive electrode material provided by the present invention comprises the following steps: (1) mixing a nickel source and a tungsten source, reacting, and obtaining a tungsten-substituted nickel-rich precursor; (2) mixing the tungsten-substituted nickel-rich precursor, a lithium source, and an additive, sintering for the first time, adding a boron source, and sintering for the second time to obtain a tungsten-boron nickel-rich positive electrode material. The tungsten-boron nickel-rich positive electrode material prepared by the present invention has excellent cycle stability and discharge specific capacity. Specifically, the preparation of the tungsten-substituted nickel-rich precursor by the present invention can make the tungsten element more evenly arranged in the tungsten-substituted nickel-rich precursor, improve the capacity and cycle stability of the prepared tungsten-boron nickel-rich positive electrode material, and avoid the agglomeration of tungsten elements on the surface to reduce performance. Tungsten replacing cobalt can reduce the lithium-nickel mixed arrangement phenomenon caused by the increase in nickel content, and improve the cycle stability of the positive electrode material. In addition, the positive electrode material of the present invention does not need to add cobalt, which can significantly reduce costs. Coated boron effectively inhibits the phase change of H2-H3, slows down the generation and expansion of cracks in the positive electrode material, stabilizes the surface lattice oxygen, slows down the oxygen loss and degradation of the surface structure; doping tungsten and coating boron has higher capacity and stronger cycle stability than single doping tungsten element or coating boron element. The present invention dopes tungsten in the positive electrode material, and tungsten can enter the unit cell, thereby ensuring the capacity. The particle size of the tungsten-substituted nickel-rich precursor is 8-12μm. If the particle size of the tungsten-substituted nickel-rich precursor is too small, its cycle performance will drop significantly and the cycle stability will deteriorate.

[0043] 2. The preparation method of the tungsten-boron nickel-rich positive electrode material provided by the present invention comprises mixing the obtained sintered material with water, filtering and drying; since the residual alkali content is high due to the first sintering, it needs to be washed with water, but the water washing will destroy the structure and cause a significant decrease in the cycle performance. The present application adds a boron source for coating, which can stabilize the structure and repair the washed structure, thereby ensuring the cycle performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0045] Figure 1 This is a SEM electron microscope image of the tungsten boron nickel-rich positive electrode material prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0046] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0047] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in the field can be used. If no manufacturer is specified for the reagents or instruments used, they are all conventional reagent products that can be obtained commercially.

[0048] Example 1

[0049] This embodiment provides a method for preparing a tungsten-boron nickel-rich positive electrode material, comprising the following steps:

[0050] (1) Nickel sulfate, tungsten hydroxide, 10 mol / L ammonia water and 6 mol / L sodium hydroxide solution were mixed and placed in a 2.5 L intermittent reaction vessel, heated to 75° C. under an argon atmosphere and stirred for reaction for 6 h; rinsed and filtered with deionized water and sodium hydroxide solution, dried in an oven at 110° C., sieved and demagnetized to obtain a tungsten-substituted nickel-rich precursor with a particle size of 12 μm.

[0051] The molar ratio of nickel in the nickel source to tungsten in the tungsten source is 93:7; the ammonia value of the reaction system is controlled to be 7.0 g / L, and the pH value is 11; and the stirring speed is 600 rpm.

[0052] (2) mixing a tungsten-substituted nickel-rich precursor, lithium hydroxide and aluminum oxide in a high-speed mixer, and sintering at 730° C. for 10 hours in an oxygen atmosphere of 0.4 L / min; the ratio of the total molar amount of nickel and tungsten in the tungsten-substituted nickel-rich precursor to the molar amount of lithium in the lithium hydroxide is 1:1.04; the ratio of the total molar amount of nickel and tungsten in the tungsten-substituted nickel-rich precursor to the molar amount of aluminum oxide is 1:0.006;

[0053] (3) The product of the first sintering and water are stirred and filtered at a mass ratio of 1:0.8, and dried in a vacuum drying oven at 120° C.; 0.3 wt % of boric acid (based on the mass of the dried product) is added, mixed evenly in a high-speed mixer, and sintered at 550° C. for 5 h in an oxygen atmosphere of 0.4 L / min to obtain a tungsten-boron nickel-rich positive electrode material.

[0054] The SEM electron microscope image of the tungsten boron nickel-rich positive electrode material prepared in this embodiment is shown in Figure 1 .

[0055] Example 2

[0056] This embodiment provides a method for preparing a tungsten-boron nickel-rich positive electrode material, comprising the following steps:

[0057] (1) Nickel chloride, sodium tungstate, 10 mol / L ammonia water and 6 mol / L sodium hydroxide solution were mixed and placed in a 2.5 L intermittent reaction vessel. The mixture was heated to 70° C. and stirred for reaction for 7 h under an argon atmosphere. The mixture was rinsed and filtered with deionized water and sodium hydroxide solution, dried in an oven at 120° C., and sieved for demagnetization to obtain a tungsten-substituted nickel-rich precursor with a particle size of 12 μm.

[0058] The molar ratio of nickel in the nickel source to tungsten in the tungsten source is 92:8; the ammonia value of the reaction system is controlled to be 7.6 g / L, and the pH value is 9; and the stirring speed is 600 rpm.

[0059] (2) mixing a tungsten-substituted nickel-rich precursor, lithium hydroxide and aluminum hydroxide in a high-speed mixer, and sintering at 710° C. for 8 h in an oxygen atmosphere of 0.2 L / min; the ratio of the total molar amount of nickel and tungsten in the tungsten-substituted nickel-rich precursor to the molar amount of lithium in lithium hydroxide is 1:1.06; the ratio of the total molar amount of nickel and tungsten in the tungsten-substituted nickel-rich precursor to the molar amount of aluminum hydroxide is 1:0.003;

[0060] (3) The product of the first sintering and water are stirred and filtered at a mass ratio of 1:0.8, and dried in a vacuum drying oven at 120°C; 0.2wt% of boron oxide (based on the mass of the dried product) is added, mixed evenly in a high-speed mixer, and sintered at 600°C for 6h in an oxygen atmosphere of 0.6L / min to obtain a tungsten boron nickel-rich positive electrode material.

[0061] Example 3

[0062] This embodiment provides a method for preparing a tungsten-boron nickel-rich positive electrode material, comprising the following steps:

[0063] (1) Nickel trioxide, nickel chloride, tungsten hydroxide, 10 mol / L ammonia water and 6 mol / L sodium hydroxide solution were mixed and placed in a 2.5 L intermittent reaction vessel. The mixture was heated to 80° C. and stirred for reaction for 8 h under an argon atmosphere. The mixture was rinsed and filtered with deionized water and sodium hydroxide solution, dried in an oven at 120° C., and sieved to remove magnetism, thereby obtaining a tungsten-substituted nickel-rich precursor with a particle size of 9 μm.

[0064] The molar ratio of nickel in the nickel source to tungsten in the tungsten source is 95:5; the ammonia value of the reaction system is controlled to be 5 g / L, and the pH value is 12; and the stirring speed is 1000 rpm.

[0065] (2) mixing a tungsten-substituted nickel-rich precursor, lithium hydroxide and aluminum hydroxide in a high-speed mixer, and sintering at 700° C. for 12 hours in an oxygen atmosphere of 0.4 L / min; the ratio of the total molar amount of nickel and tungsten in the tungsten-substituted nickel-rich precursor to the molar amount of lithium in the lithium hydroxide is 1:1.02; the ratio of the total molar amount of nickel and tungsten in the tungsten-substituted nickel-rich precursor to the molar amount of aluminum hydroxide is 1:0.008;

[0066] (3) The product of the first sintering and water are stirred and filtered at a mass ratio of 1:0.8, and dried in a vacuum drying oven at 120°C; 0.1wt% of boron oxide (based on the mass of the dried product) is added, mixed evenly in a high-speed mixer, and sintered at 500°C for 4h in an oxygen atmosphere of 0.6L / min to obtain a tungsten boron nickel-rich positive electrode material.

[0067] Comparative Example 1

[0068] This comparative example provides a method for preparing a positive electrode material. Compared with Example 1, the only difference is that in step (3), boric acid is not added.

[0069] Comparative Example 2

[0070] This comparative example provides a method for preparing a positive electrode material. Compared with Example 1, the only difference is that in step (1), tungsten hydroxide is not added; and in step (3), boric acid is not added.

[0071] Comparative Example 3

[0072] This comparative example provides a method for preparing a positive electrode material. Compared with Example 1, the only difference is that in step (1), no tungsten hydroxide is added; in step (3), tungsten hydroxide is added in the same molar amount as in step (1) of Example 1.

[0073] Test Case

[0074] The performance of the tungsten boron nickel-rich positive electrode materials prepared in the above embodiments and the positive electrode materials prepared in the comparative examples were tested as follows:

[0075] Particle size test method: Malvern laser particle sizer (Master sizer 2000E) was used for testing;

[0076] Assemble button cells: Weigh tungsten boron nickel-rich cathode material, acetylene black, and PVDF (polyvinylidene fluoride) in a mass ratio of 95:2.5:2.5, mix, add appropriate amount of deionized water, grind thoroughly, and then apply on aluminum foil, dry under vacuum at 120°C for 12 hours, cool naturally, and slice using a slicer to obtain a circular electrode with a diameter of 14 mm. The battery model is CR2025 button half-cell, the electrolyte is LiPF6 solution, the solvent in the electrolyte includes ethylene carbonate: dimethyl carbonate: methyl ethyl carbonate in a volume ratio of 1:1:1, and the concentration of LiPF6 in the electrolyte is 1 mol / L.

[0077] (1) 0.2C discharge specific capacity test method: At room temperature, the battery was charged at 0.2C to a voltage of 4.25V, then charged at a constant voltage (voltage of 4.25V) to a current of 20mA, and allowed to stand for 10min; then charged at a constant current of 0.2C to 2.7V, allowed to stand for 10min, and cycled 3 times. The results are shown in Table 1.

[0078] (2) 1C discharge specific capacity measurement: At room temperature, the above battery (the battery obtained after operating according to test method (1)) was charged at 1C constant current to 3.75V, and then charged at constant voltage (voltage is 3.75V) to a current of 20mA, and allowed to stand for 10 minutes; then charged at 1C constant current to 2.7V, allowed to stand for 10 minutes, and cycled 100 times. The results are shown in Table 1.

[0079] Cycle performance = (100th discharge specific capacity / 1st 1C discharge specific capacity) × 100%.

[0080] Table 1 Performance results of various embodiments and comparative examples

[0081]

[0082] As can be seen from Table 1, after the batteries are made of the tungsten boron nickel-rich positive electrode material prepared by the preparation method of the present invention in the test example, their 0.2C discharge specific capacity is greater than 214.6 mAh / g, and the 1C discharge specific capacity is greater than 203.3 mAh / g. The cycle performance after 100 cycles is maintained at more than 92.5% of the initial discharge capacity.

[0083] By comparing Example 1 with Comparative Examples 1-2, it can be seen that the 0.2C discharge specific capacity, 1C discharge specific capacity and cycle performance after 100 cycles of Comparative Example 1 without adding a boron source coating and Comparative Example 2 without adding a tungsten source and a boron source are greatly reduced; this indicates that the 0.2C discharge specific capacity, 1C discharge specific capacity and cycle performance after 100 cycles of the tungsten boron nickel-rich positive electrode material prepared by the preparation method of the present invention are the best.

[0084] By comparing Example 1 and Comparative Example 3, it can be seen that compared with directly mixing and sintering the precursor, lithium source and tungsten source to obtain the positive electrode material, the tungsten prepared in the present application is used to replace the nickel-rich precursor to prepare the tungsten-boron nickel-rich positive electrode material, which has a higher discharge specific capacity and better cycle performance.

[0085] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived from these are still within the scope of protection of the invention.

Claims

1. A method for preparing a tungsten-boron nickel-rich positive electrode material, characterized in that: The steps include: (1) mixing a nickel source and a tungsten source, reacting them, and obtaining a tungsten-substituted nickel-rich precursor; (2) mixing a tungsten-substituted nickel-rich precursor, a lithium source and an additive, sintering the mixture for the first time, adding a boron source, and sintering the mixture for the second time to obtain a tungsten-boron-rich nickel positive electrode material; The particle size of the tungsten-substituted nickel-rich precursor is 8-12 μm.

2. The preparation method according to claim 1, characterized in that: The nickel source comprises at least one of nickel sulfate, nickel chloride and nickel trioxide; and / or, The tungsten source includes at least one of tungsten hydroxide, tungsten chloride and sodium tungstate; and / or, The molar ratio of the nickel element in the nickel source to the tungsten element in the tungsten source is (92-95):(5-8).

3. The preparation method according to claim 1 or 2, characterized in that: The specific steps of the reaction include: stirring, controlling the ammonia value of the reaction system to 5.0-7.6 g / L, and controlling the pH value of the reaction system to 9-12; Preferably, the stirring speed is 600-1000 rpm.

4. The preparation method according to any one of claims 1 to 3, characterized in that The reaction is carried out under an inert gas; and / or, The reaction temperature is 70-80°C; and / or, The reaction time is 6-9h.

5. The preparation method according to claim 1, characterized in that: The ratio of the total molar amount of nickel and tungsten in the tungsten-substituted nickel-rich precursor to the molar amount of lithium in the lithium source is 1:(1.02-1.06); and / or, The ratio of the total molar amount of nickel and tungsten in the tungsten-substituted nickel-rich precursor to the molar amount of the additive is 1:(0.003-0.008); and / or, The lithium source comprises at least one of lithium hydroxide and lithium carbonate; and / or, The additive comprises at least one of aluminum oxide, aluminum hydroxide and aluminum chloride; and / or, The boron source includes at least one of boric acid, sodium borate and boron oxide.

6. The preparation method according to claim 5, characterized in that: The first sintering temperature is 700-760° C.; and / or, The first sintering is performed in an oxygen atmosphere; and / or, The first sintering time is 8-12 hours.

7. The preparation method according to claim 6, characterized in that: After the first sintering, the further step includes: mixing the obtained first sintered material with water, filtering, and drying; Preferably, the ratio of the mass of the fuel to the mass of water is 1:(0.6-1); Preferably, based on the mass of the dried product, the added amount of the boron source is 0.1-0.3 wt %.

8. The preparation method according to claim 1, characterized in that: The second sintering temperature is 500-600° C.; and / or, The second sintering is performed in an oxygen atmosphere; and / or, The second sintering time is 4-6 hours.

9. The tungsten boron nickel-rich positive electrode material prepared according to any one of claims 1 to 8.

10. Use of the tungsten-boron nickel-rich positive electrode material prepared according to any one of claims 1 to 8 in lithium-ion batteries.

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