WO2025010705A1 - Boron-doped positive electrode material precursor, and preparation method therefor and use thereof - Google Patents

Abstract

A boron-doped positive electrode material precursor, and a preparation method therefor and a use thereof. According to the preparation method, a metal hydroxide raw material is directly mixed with a solution containing borate ions, and a heating reaction is implemented to obtain a boron-doped positive electrode material precursor. The method uses the characteristic that the surface and the internal pores of the metal hydroxide are rich in a large amount of active hydroxyl, to cause the metal hydroxide and the hydroxyl of the borate ions to generate weak interaction, thereby enhancing the uniform adsorption of the boron element on the surface and the internal pores, thus obtaining a precursor having an excellent boron doping effect, and avoiding boron salt residues caused by using a boron salt and a ball milling method. Compared with existing coprecipitation methods, the precipitation efficiency of the boron element is greatly improved, and the solution obtained by separation can be recycled as a solution containing borate ions. The boron-doped positive electrode material prepared by using the precursor has good capacity performance and excellent cycle performance.

Description

A boron-doped positive electrode material precursor and its preparation method and use Technical Field

The present invention belongs to the field of ion batteries and relates to a boron-doped positive electrode material precursor and a preparation method and use thereof.

Background Art

At present, developing high-performance lithium-ion batteries is one of the important ways to solve the "range anxiety" problem of electric vehicles. Compared with the commonly used graphite negative electrodes in the market, the specific capacity of positive electrode materials is relatively low, which is one of the key factors limiting the improvement of lithium-ion battery energy density. Ternary layered positive electrode materials have the advantages of high specific capacity, long life and safety, making them one of the most popular positive electrode materials. However, due to their own defects, such as mixed arrangement of lithium and nickel layers and irreversible phase changes, the cycle life of ternary lithium-ion batteries is shortened and they are prone to safety problems.

Doping is one of the effective means to improve the structural stability of ternary cathode materials. Common doping elements are mainly metal elements, such as Mg, Ti, Mo, Zr, Nb, Zn, W, etc. Boron, as a cheap non-metallic element, is also used to modify cathode materials.

Yang-Kook Sun et al. (Adv. Energy. Mater. 2020, 2000495, 1-8) from Hanyang University in South Korea studied the effect of boron doping on high-nickel ternary cathode materials. The study showed that boron doping can refine primary particles, help form radial microstructures, reduce stress accumulation, effectively inhibit the generation of microcracks, and enable cathode materials to have good rate performance and cycle performance.

In addition, boron also has the effect of optimizing crystal planes. Guo Xiaodong et al. from Sichuan University (ACS Appl. Mater. Interfaces. 2022, 14, 2711-2719) reported a boron-doped modified lithium-rich manganese-based positive electrode material, proving that boron is easily adsorbed on the {010} crystal plane family with high specific surface energy, which makes the positive electrode material expose more highly active {010} crystal plane families during calcination, thereby facilitating smoother transmission of Li ⁺ .

Currently, boron is doped mainly in two ways:

The first is physical mixing doping, where the precursor, lithium source, and boron source are mixed evenly by a mixer and then calcined, such as CN110112403A. However, in this method, the boron element is mainly enriched on the surface and is difficult to enter the bulk phase, resulting in a poor doping effect; the second is to achieve doping during the precursor synthesis process, where the boron element is co-precipitated with the hydroxide in the form of borates, such as CN112758995A and CN110429268A, but this method has a low boron precipitation efficiency and requires the addition of a large excess of boron source. In addition, a large amount of boron is lost in the subsequent precursor alkali washing process, resulting in low doping efficiency.

Therefore, it is still necessary to develop a new boron doping technical solution to achieve better boron doping effect while reducing the impact of residual boron salts on the product.

Summary of the invention

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

In view of the problems existing in the prior art, the purpose of the present disclosure is to provide a boron-doped positive electrode material precursor and a preparation method and use thereof, wherein the preparation method directly mixes a metal hydroxide with a solution containing borate ions, and performs a heating reaction to obtain a boron-doped positive electrode material precursor. The present disclosure utilizes the characteristics of the metal hydroxide surface and internal pores being rich in a large number of active hydroxyl groups, so that the metal hydroxide and the hydroxyl groups of the borate ions produce a weak interaction, thereby enhancing the uniform adsorption of the boron element on the surface and internal pores, thereby obtaining a precursor with excellent boron doping effect, and the cycle performance of the boron-doped positive electrode material prepared using the precursor is greatly improved.

To achieve this purpose, the present invention adopts the following technical solutions:

In a first aspect, an embodiment of the present disclosure provides a boron-doped positive electrode material precursor, including a boron-doped metal hydroxide, wherein the chemical formula of the boron-doped metal _hydroxide is _MnBd (OH) ₂ , wherein M is a metal element, and n+d=1.

The embodiment of the present disclosure obtains the boron-doped positive electrode material precursor by boron-doping the positive electrode material precursor, wherein the boron element penetrates into the interior of the material and is evenly distributed. Changing the doping amount (content) of the boron element can adjust and improve the capacity and cycle performance of the further obtained boron-doped positive electrode material.

The following are optional technical solutions for the embodiments of the present disclosure, but are not intended to be limitations of the technical solutions provided by the embodiments of the present disclosure. Through the following technical solutions, the technical objectives and beneficial effects of the embodiments of the present disclosure can be better achieved and realized.

As an optional technical solution of the embodiment of the present disclosure, the boron-doped metal hydroxide is a homogeneous solid solution.

In one embodiment, the boron content in the boron-doped positive electrode material precursor is 500-8000ppm, for example, 500ppm, 600ppm, 700ppm, 800ppm, 900ppm, 1000ppm, 1200ppm, 1400ppm, 1600ppm, 1800ppm, 2000ppm, 2200ppm, 2400ppm, 2600ppm, 2800ppm, 3000ppm, 3200ppm, 3400ppm, 3600ppm, 3800ppm, 400 0ppm, 4200ppm, 4400ppm, 4600ppm, 4800ppm, 5000ppm, 5200ppm, 5400ppm, 5600ppm, 5800ppm, 6000ppm, 6200ppm, 6400ppm, 6600ppm, 6800ppm, 7000ppm, 7200ppm, 7400ppm, 7600ppm, 7800ppm or 8000ppm, but is not limited to the listed values, and other values not listed within the above numerical range are also applicable.

In one embodiment, 0.001≤d≤0.07, for example, 0.001, 0.003, 0.005, 0.008, 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06, 0.065 or 0.07, but is not limited to the listed values, and other values not listed within the above numerical range are also applicable.

In one embodiment, M includes any one or a combination of at least two of Ni, Co or Mn, and typical but non-limiting examples of the combination include a combination of Ni and Co, a combination of Ni and Mn, or a combination of Co and Mn.

In one embodiment, M also includes Al.

In one embodiment, the boron-doped metal hydroxide has a chemical formula of Ni _a Co _b X _c B _d (OH) ₂ , wherein 0.5≤a≤0.9, such as 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85 or 0.9, etc.; 0.02≤b≤0.5, such as 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 or 0.5, etc.; 0.02≤c≤0.5, such as 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 or 0.5, etc. 0.5, etc., 0.001≤d≤0.07, for example, 0.001, 0.003, 0.005, 0.008, 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06, 0.065 or 0.07, etc., a+b+c+d=1, X includes Mn and/or Al, but is not limited to the listed values, and other values not listed within the above numerical range are also applicable.

In one embodiment, the specific surface area of the boron-doped metal hydroxide is 6 to 45 m ² /g, for example, 6 m ² /g, 9 m ² /g, 12 m ² /g, 15 m ² /g, 18 m ² /g, 21 m ² /g, 24 m ² /g, 27 m ² /g, 30 m ² /g, 33 m ² /g, 39 m ² /g, 39 m ² /g, 42 m ² /g or 45 m ² /g, but is not limited to the listed values, and other values not listed within the above numerical range are also applicable.

In one embodiment, the porosity of the boron-doped metal hydroxide is 0.01% to 0.18%, for example 0.01%, 0.02%, 0.04%, 0.06%, 0.08%, 0.1%, 0.12%, 0.14%, 0.16% or 0.28%, etc., but is not limited to the listed values, and other unlisted values within the above numerical range are also applicable.

In a second aspect, the present disclosure provides a method for preparing a boron-doped positive electrode material precursor, comprising the following steps:

The metal hydroxide raw material is mixed with a solution containing borate ions, and heated to react to obtain a boron-doped positive electrode material precursor.

The embodiment of the present disclosure directly uses metal hydroxide as a raw material, mixes it with a solution containing borate ions, and utilizes the characteristics of the metal hydroxide surface and internal pores rich in a large number of active hydroxyl groups to produce weak interactions with the hydroxyl groups of the borate ions, thereby enhancing the uniform adsorption of boron elements on the surface and internal pores, thereby obtaining a precursor with excellent boron doping effect, and at the same time, avoiding the use of boron salts and spherical The boron salt residue caused by the grinding method. Therefore, compared with the co-precipitation method of the prior art, the precipitation efficiency of the boron element is greatly improved, and the separated solution can be recycled as a solution containing borate ions. The preparation method described in the embodiment of the present disclosure has a simple process, low equipment investment, and low cost. It matches the existing precursor industrial production line and has the potential for large-scale industrialization.

As an optional technical solution of the embodiment of the present disclosure, the metal hydroxide raw material includes M(OH) ₂ , wherein M is a metal element.

In one embodiment, M includes any one or a combination of at least two of Ni, Co or Mn, and typical but non-limiting examples of the combination include a combination of Ni and Co, a combination of Ni and Mn, or a combination of Co and Mn.

In one embodiment, M also includes Al.

In one embodiment, the metal hydroxide raw material is _NiaCobXc (OH) ₂ , 0.5≤a≤0.9, such as 0.5, 0.55, 0.6, _0.65 , 0.7, 0.75, 0.8 _, 0.85 or 0.9; 0.05≤b≤0.5, such as 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 or 0.5; 0.05≤c≤0.5, such as 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45 or 0.5, a+b+c=1, X includes Mn and/or Al, but is not limited to the listed values, and other values not listed within the above numerical range are also applicable.

In the embodiment of the present disclosure, the metal hydroxide can be selected as a ternary metal hydroxide, so that a boron-doped ternary positive electrode material can be prepared in the end. Boron doping in the ternary positive electrode material has a more obvious effect of improving structural stability, rate and cycle performance. The metal hydroxide can be purchased as a commercial product and used directly.

In one embodiment, the specific surface area of the metal hydroxide raw material is 6 to 45 m ² /g, for example, 6 m ² /g, 9 m ² /g, 12 m ² /g, 15 m ² /g, 18 m ² /g, 21 m ² /g, 24 m ² /g, 27 m ² /g, 30 m ² /g, 33 m ² /g, 39 m ² /g, 39 m ² /g, 42 m ² /g or 45 m ² /g, but is not limited to the above values. Other values not listed within the range also apply.

In one embodiment, the porosity of the metal hydroxide raw material is 0.01% to 0.18%, for example 0.01%, 0.02%, 0.04%, 0.06%, 0.08%, 0.1%, 0.12%, 0.14%, 0.16% or 0.28%, etc., but is not limited to the listed values, and other unlisted values within the above numerical range are also applicable.

As an optional technical solution of an embodiment of the present disclosure, a method for preparing the solution containing borate ions includes: dissolving any one of boric acid, borax or boron trioxide, or a combination of at least two of them in water; typical but non-limiting examples of the combination include a combination of boric acid and borax, a combination of boric acid and boron trioxide, or a combination of borax and boron trioxide.

In one embodiment, the molar concentration of boron element in the solution containing borate ions is 0.1-3 mol/L, for example, 0.1 mol/L, 0.3 mol/L, 0.5 mol/L, 0.7 mol/L, 0.9 mol/L, 1.1 mol/L, 1.3 mol/L, 1.5 mol/L, 1.7 mol/L, 1.9 mol/L, 2.1 mol/L, 2.3 mol/L, 2.5 mol/L, 2.7 mol/L, 2.9 mol/L or 0.1 mol/L, etc., but is not limited to the listed values, and other values not listed within the above numerical range are also applicable.

In one embodiment, the molar amount of the metal hydroxide raw material is 1 to 50 times the molar amount of the boron element in the solution containing borate ions, for example, 1 times, 3 times, 5 times, 7 times, 9 times, 11 times, 13 times, 15 times, 17 times, 19 times, 21 times, 23 times, 25 times, 27 times, 29 times, 31 times, 33 times, 35 times, 37 times, 39 times, 41 times, 43 times, 45 times, 47 times, 49 times or 50 times, but is not limited to the listed values, and other values not listed within the above numerical range are equally applicable.

As an optional technical solution for an embodiment of the present disclosure, the heating reaction method includes any one of water bath heating, microwave heating, ultrasonic heating or hydrothermal kettle heating, or a combination of at least two of them. Typical but non-limiting examples of the combination include a combination of water bath heating and microwave heating, a combination of water bath heating and ultrasonic heating, a combination of water bath heating and hydrothermal kettle heating, a combination of microwave heating and ultrasonic heating, a combination of microwave heating and hydrothermal kettle heating, or a combination of ultrasonic heating and hydrothermal kettle heating.

Heat and mass transfer can be enhanced by using microwave heating, ultrasonic heating and hydrothermal heating, making it easier for boron to penetrate into the precursor.

In one embodiment, the temperature of the heating reaction is 50-150°C, for example 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, etc., but is not limited to the listed values, and other unlisted values within the above numerical range are also applicable.

When the temperature of the heating reaction is higher within the optional range, boron is more easily adsorbed into the precursor, and the adsorbed boron content is higher.

In one embodiment, the heating reaction time is 2 to 8 hours, for example 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours or 8 hours, but is not limited to the listed values, and other values not listed within the above numerical range are also applicable.

In one embodiment, the preparation method further comprises performing solid-liquid separation after the heating reaction, and sequentially washing, drying, sieving and demagnetizing the separated solid to obtain the boron-doped positive electrode material precursor.

In one embodiment, the solid-liquid separation comprises centrifugation.

In one embodiment, the washing liquid of the washing comprises pure water.

In one embodiment, the separation liquid is used as a solution containing borate ions.

The disclosed embodiment can optionally separate the obtained boron-doped positive electrode material precursor from the solution by solid-liquid separation, such as centrifugation, so that the separated solid can obtain the target product after washing and drying processes, and the separated liquid can be recycled. Since the disclosed embodiment uses boric acid as a raw material, and the solution contains only borate ions, the content of boric acid in the solution can be greatly increased, thereby increasing the boron doping rate and doping effect, making it easier for boron doping to penetrate into the interior, and on the other hand, it can avoid a large amount of boric acid waste, and a large amount of boric acid retained in the separated solution can still be used, so the use of raw materials can be saved, effectively reducing costs.

In a third aspect, an embodiment of the present disclosure provides a positive electrode material, wherein the positive electrode material is prepared using the boron-doped positive electrode material precursor described in the first aspect.

In a fourth aspect, the present disclosure provides a method for preparing the positive electrode material according to the third aspect, the method comprising the following steps:

The boron-doped positive electrode material precursor described in the first aspect is mixed with a lithium salt and sintered to obtain a positive electrode material.

As an optional technical solution of the embodiment of the present disclosure, the ratio of the total molar amount of metal elements in the boron-doped positive electrode material precursor to the molar amount of lithium elements in the lithium salt is 1:(0.99~1.04), for example, 1:0.99, 1:1, 1:1.01, 1:1.02, 1:1.03 or 1:1.04, etc., but is not limited to the listed values, and other unlisted values within the above numerical range are also applicable.

In one embodiment, the lithium salt includes lithium hydroxide.

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

In one embodiment, the sintering is a two-stage sintering.

In one embodiment, the heating rate of the first stage sintering in the two-stage sintering is 1-3°C/min, for example, 1°C/min, 1.5°C/min, 2°C/min, 2.5°C/min or 3°C/min, the holding temperature is 400-440°C, for example, 400°C, 405°C, 410°C, 415°C, 420°C, 425°C, 430°C, 435°C or 440°C, and the holding time is 3-5h, for example, 3h, 3.5h, 4h, 4.5h or 5h, but is not limited to the listed values, and other values not listed within the above numerical range are also applicable.

In one embodiment, the heating rate of the second stage sintering in the two-stage sintering is 1 to 3°C/min, for example, 1°C/min, 1.5°C/min, 2°C/min, 2.5°C/min or 3°C/min, the holding temperature is 700 to 740°C, for example, 700°C, 705°C, 710°C, 715°C, 720°C, 725°C, 730°C, 735°C or 740°C, and the holding time is 7 to 9h, for example, 7h, 7.5h, 8h, 8.5h or 9h, but is not limited to the listed values, and other values not listed within the above numerical range are also applicable.

In a fifth aspect, an embodiment of the present disclosure provides a positive electrode plate, wherein the positive electrode plate contains the positive electrode material described in the third aspect.

In a sixth aspect, an embodiment of the present disclosure provides a lithium-ion battery, wherein the lithium-ion battery contains the positive electrode sheet described in the fourth aspect.

Compared with the prior art solutions, the present invention has at least the following beneficial effects:

The present invention directly mixes a metal hydroxide with a solution containing borate ions, and utilizes the characteristics of the metal hydroxide surface and internal pores being rich in a large number of active hydroxyl groups to produce weak interactions with the hydroxyl groups of the borate ions, thereby enhancing the uniform adsorption of the boron element on the surface and internal pores, thereby obtaining a precursor with excellent boron doping effect. At the same time, the boron salt residues caused by the use of boron salts and ball milling are avoided, and the content of boric acid in the solution can be greatly increased, thereby improving the boron doping rate and doping effect, making it easier for boron doping to penetrate into the interior, and compared with the coprecipitation method of the prior art, the precipitation efficiency of the boron element is greatly improved, and the separated solution can be used as a solution containing borate ions for recycling. The preparation method disclosed in the present invention has a simple process, low equipment investment, and low cost, matches the existing precursor industrial production line, and has the potential for large-scale industrialization.

Other aspects will be apparent upon reading and understanding the drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are used to provide further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the technical solution of this article and do not constitute a limitation on the technical solution of this article.

FIG1 is a scanning electron microscope image of the boron-doped cathode material precursor obtained in Example 1;

FIG2 is a cross-sectional view of the boron-doped positive electrode material precursor obtained in Example 1;

FIG. 3 is a distribution diagram of the boron element in FIG. 2 .

DETAILED DESCRIPTION

The technical solution of the present disclosure is further described below through specific implementation methods. Those skilled in the art should understand that the embodiments are only to help understand the present disclosure and should not be regarded as specific limitations of the present disclosure.

Example 1

This embodiment provides a boron-doped ternary cathode material precursor and a preparation method thereof, the preparation method comprising the following steps:

(1) preparing 16 L of an aqueous solution with a boron concentration of 0.4 mol/L using boric acid, wherein the total molar amount of the boron element is 6.4 mol;

(2) 20 kg of Ni _0.90 Co _0.05 Mn _0.05 (OH) ₂ metal hydroxide raw material with a specific surface area of 15 m ² /g and a porosity of 0.04% was added to the above aqueous solution, and the molar ratio of Ni _0.90 Co _0.05 Mn _0.05 (OH) ₂ to boron element was controlled to be 34;

(3) The mixture was placed in a water bath, heated to 70°C, stirred at 500 rpm, and reacted for 8 hours; then centrifuged, washed with pure water, dried, sieved, and demagnetized to obtain a boron-doped ternary cathode material precursor.

Example 2

This embodiment provides a boron-doped ternary cathode material precursor and a preparation method thereof, the preparation method comprising the following steps:

(1) using boron trioxide to prepare 16 L of an aqueous solution having a boron concentration of 1.9 mol/L, the total molar amount of the boron element being 30.4 mol;

(2) 20 kg of Ni _0.80 Co _0.10 Mn _0.10 (OH) ₂ metal hydroxide raw material with a specific surface area of 38 m ² /g and a porosity of 0.15% was added to the above aqueous solution, and the molar ratio of Ni _0.80 Co _0.10 Mn _0.10 (OH) ₂ to boron element was controlled to be 7.1;

(3) The mixture is transferred to a microwave reactor, heated to 100° C., and reacted for 2 h; then centrifuged, washed with pure water, dried, sieved, and demagnetized to obtain a boron-doped ternary cathode material precursor.

Example 3

This embodiment provides a boron-doped ternary cathode material precursor and a preparation method thereof, the preparation method comprising the following steps:

(1) using borax to prepare 16 L of an aqueous solution having a boron concentration of 0.8 mol/L, the total molar amount of the boron element being 12.8 mol;

(2) 20 kg of Ni _0.60 Co _0.20 Al _0.20 (OH) ₂ metal hydroxide raw material with a specific surface area of 21 m ² /g and a porosity of 0.09% was added to the above aqueous solution, and the molar ratio of Ni _0.60 Co _0.20 Al _0.20 (OH) ₂ to boron element was controlled to be 17;

(3) The mixture was transferred to an ultrasonic instrument with an ultrasonic frequency of 50 kHz, heated to 50°C, and reacted for 4 hours; then centrifuged, washed with pure water, dried, sieved, and demagnetized to obtain a boron-doped ternary cathode material precursor.

Example 4

This embodiment provides a boron-doped ternary cathode material precursor and a preparation method thereof, the preparation method comprising the following steps:

(1) using borax to prepare 1 L of an aqueous solution with a boron concentration of 0.4 mol/L, the total molar amount of the boron element is 0.4 mol;

(2) 1 kg of Ni _0.70 Co _0.20 Mn _0.10 (OH) ₂ metal hydroxide raw material with a specific surface area of 10 m ² /g and a porosity of 0.03% was added to the above aqueous solution, and the molar ratio of Ni _0.70 Co _0.20 Mn _0.10 (OH) ₂ to boron element was controlled to be 27;

(3) The mixture is transferred to a hydrothermal reactor, sealed, placed in an oven and heated to 150° C. for reaction for 8 h; then centrifuged, washed with pure water, dried, sieved, and demagnetized to obtain a boron-doped ternary cathode material precursor.

Example 5

The present embodiment provides a boron-doped ternary positive electrode material precursor and a preparation method thereof. The preparation method is exactly the same as that in Example 1, except that in step (2), the amount of Ni _0.90 Co _0.05 Mn _0.05 (OH) ₂ is adjusted from 20 kg to 0.6 kg, so that the molar ratio of Ni _0.90 Co _0.05 Mn _0.05 (OH) ₂ to boron element is changed from 34 to 1.

Example 6

The present embodiment provides a boron-doped ternary positive electrode material precursor and a preparation method thereof. The preparation method is exactly the same as that in Example 1, except that in step (2), the amount of Ni _0.90 Co _0.05 Mn _0.05 (OH) ₂ is adjusted from 20 kg to 23.5 kg, so that the molar ratio of Ni _0.90 Co _0.05 Mn _0.05 (OH) ₂ to boron element is changed from 34 to 40.

Example 7

The present embodiment provides a boron-doped ternary positive electrode material precursor and a preparation method thereof. The preparation method is exactly the same as that in Example 1, except that in step (2), the amount of Ni _0.90 Co _0.05 Mn _0.05 (OH) ₂ is adjusted from 20 kg to 29.5 kg, so that the molar ratio of Ni _0.90 Co _0.05 Mn _0.05 (OH) ₂ to boron element is changed from 34 to 50.

Example 8

The present embodiment provides a boron-doped ternary positive electrode material precursor and a preparation method thereof. The preparation method is exactly the same as that in Example 1, except that in step (2), the amount of Ni _0.90 Co _0.05 Mn _0.05 (OH) ₂ is adjusted from 20 kg to 31.2 kg, so that the molar ratio of Ni _0.90 Co _0.05 Mn _0.05 (OH) ₂ to boron element is changed from 34 to 53.

Example 9

This embodiment provides a boron-doped ternary cathode material precursor and a preparation method thereof. The preparation method is identical to that of Embodiment 1 except that the heating temperature is adjusted from 70° C. to 40° C. in step (3).

Example 10

This embodiment provides a boron-doped ternary cathode material precursor and a preparation method thereof. The preparation method is identical to that of Embodiment 1 except that the heating temperature is adjusted from 70° C. to 90° C. in step (3).

Embodiment 11

This embodiment provides a boron-doped ternary cathode material precursor and a preparation method thereof. The preparation method is identical to that of Embodiment 1 except that in step (3), the mixture is placed in a microwave reactor and the reaction is carried out at a temperature of 70°C.

Example 12

This embodiment provides a boron-doped ternary cathode material precursor and a preparation method thereof. The preparation method is identical to that of Embodiment 1 except that in step (3), the mixture is placed in an ultrasonic instrument and the reaction is carried out at a temperature of 70°C.

Example 13

This embodiment provides a boron-doped ternary cathode material precursor and a preparation method thereof. The preparation method is identical to that of Embodiment 1 except that in step (2), a Ni _0.90 Co _0.05 Mn _0.05 (OH) ₂ metal hydroxide raw material with a specific surface area of 6 m ² /g and a porosity of 0.02% is used instead.

Embodiment 14

This embodiment provides a boron-doped ternary cathode material precursor and a preparation method thereof. The preparation method uses the separated liquid obtained by centrifugation in step (3) of embodiment 1 as an aqueous solution containing boric acid in step (1). The preparation method comprises the following steps:

(1) recovering the separated liquid after centrifugation in step (3) of Example 1, testing its boron content, and re-preparing 16 L of an aqueous solution with a boron concentration of 0.4 mol/L by adding boric acid and water, and the total molar amount of boron element is 6.4 mol;

(2) 20 kg of Ni _0.90 Co _0.05 Mn _0.05 (OH) ₂ metal hydroxide raw material with a specific surface area of 15 m ² /g and a porosity of 0.04% was added to the above aqueous solution, and the molar ratio of Ni _0.90 Co _0.05 Mn _0.05 (OH) ₂ to boron element was controlled to be 34;

(3) The mixture was placed in a water bath, heated to 70°C, stirred at 500 rpm, and reacted for 8 hours; then centrifuged, washed with pure water, dried, sieved, and demagnetized to obtain a boron-doped ternary cathode material precursor.

Embodiment 15

This embodiment provides a boron-doped ternary cathode material precursor and a preparation method thereof. The preparation method uses sodium borohydride instead of boric acid in step (1). Other than that, the conditions are exactly the same as those in Example 1.

Control group 1

This control group 1 provides a boron-doped ternary cathode material precursor and a preparation method thereof, wherein the preparation method is a coprecipitation method, comprising the following steps:

(1) A mixed metal salt aqueous solution A of cobalt sulfate, nickel sulfate and manganese sulfate was prepared, wherein the total concentration of metal ions was 1.8 mol/L and the molar ratio of nickel:cobalt:manganese was 90:5:5; a sodium hydroxide aqueous solution (10 mol/L) was prepared, and 871 g of boric acid was added to 100 kg of the sodium hydroxide aqueous solution, which was marked as alkali solution B; and a 10% by mass ammonia aqueous solution C was prepared.

(2) 250 L of deionized water was introduced into a 300 L reactor, heated to 65° C., stirred at a rate of 450 rpm, and the prepared alkali solution B and ammonia water C were introduced into the reactor. The pH in the reactor was adjusted to 11.5 and the ammonia value to 2.2 g/L.

(3) introducing liquid metal A into the reactor, and adjusting the pH to increase the particle size. When the particle size reaches the required value, the slurry is transferred to the aging reactor. The entire reaction time is controlled within 120 to 168 hours.

(4) The slurry in the aging kettle was centrifuged and then washed with 360L of hot water and dried at 120°C for 12h. At this time, the boron content in the dried material was tested to be 1963ppm, and the boron doping amount accounted for 35% of the boron input amount;

(5) The dried material in (4) was washed with a 0.8 mol/L hot sodium hydroxide solution (temperature 60° C.) in a centrifuge for 30 min, then washed with 60° C. water for 30 min, dried at 120° C. for 12 h, sieved, and iron removed to obtain a precursor product.

Control group 2

The control group used the Ni _0.90 Co _0.05 Mn _0.05 (OH) ₂ metal hydroxide raw material with a specific surface area of 15 m ² /g and a porosity of 0.04% in Example 1 as a precursor.

Figure 1 is a scanning electron microscope image of the boron-doped ternary positive electrode material precursor obtained in Example 1, Figure 2 is its cross-sectional view, and Figure 3 is the distribution of the B element in the cross-sectional view. It can be seen from the figure that the primary particles of the precursor are in the shape of fine needles and are arranged crosswise. The cross-sectional view shows that there are many tiny pores inside the precursor. The electron probe mapping data reveals that the B element is evenly distributed inside and outside the precursor.

The boron doping amount (boron content) in the precursors obtained in the test examples and comparative examples was analyzed by inductively coupled plasma emission spectrometry (ICP) through sample pretreatment by burning. The effective amount of the corresponding raw materials (boric acid, borax and boron trioxide) was calculated according to the boron doping amount. The proportion of the boron doping amount to the boron input amount was calculated based on the total amount of raw materials actually added (input amount). The results are recorded in Table 1.

The precursors obtained in the embodiment and the comparative example are then prepared as positive electrode materials: the dried material of the precursor and the lithium hydroxide mixture are placed in a box furnace, and the ratio of the total molar amount of the metal element in the boron-doped ternary positive electrode material precursor to the molar amount of the lithium element in the lithium hydroxide is 1:1.03; two-stage sintering is performed under an oxygen atmosphere: the temperature of the first stage sintering is 420°C, the holding time is 4h, and the heating rate is 2°C/min; the temperature of the second stage sintering is 720°C, the holding time is 8h, and the heating rate is 2°C/min; after the sintering is completed and cooled to room temperature, Obtain the corresponding positive electrode material.

According to the mass ratio of positive electrode material: acetylene black: polyvinylidene fluoride (PVDF) = 8:1:1, mix and grind evenly, add appropriate amount of solvent NMP (1-methyl-2-pyrrolidone), stir for 8h, and evenly coat the stirred slurry on aluminum foil with a thickness of 200μm, and dry it in a vacuum oven at 80℃ for 8h to obtain the electrode plate. Celgard 2400 polypropylene diaphragm is used, metal lithium sheet is used for the negative electrode, and the electrolyte is a DMC/EC (volume ratio 1:1) mixed solution of 1mol/L LiPF6. The charge and discharge performance is tested on the blue battery test system, the test voltage is 2.8~4.3V, and the button battery 100-cycle discharge cycle data under 25℃ and 0.1C conditions are obtained.

The results are recorded in Table 1.

Table 1

Note: “/” means no boron doping was performed and no calculation is required.

From Table 1, we can conclude that:

It can be concluded from Example 1, Examples 5-8 and Control Group 2 that the molar ratio of metal hydroxide to boron is The larger the boron ratio, the less boron content is doped, but the proportion of boron doping to boron input increases. The boron doping amount is inversely proportional to the first discharge capacity and directly proportional to the cycle retention rate. Compared with the non-boron doped precursor, the stability of the boron-doped positive electrode material is greatly improved.

It can be concluded from Example 1 and Examples 9-10 that the higher the temperature, the higher the boron doping amount.

It can be concluded from Example 1 and Examples 11-12 that, compared with stirring heating, microwave heating and ultrasonic heating are helpful for the boron element to penetrate into the interior of the precursor, and the boron doping amount is higher.

It can be concluded from Example 1 and Example 13 that the lower the specific surface area and porosity of the metal hydroxide, the less the adsorbed boron content and the less the boron doping amount.

Control group 1 adopts the coprecipitation method, and its boric acid precipitation efficiency is low during the coprecipitation reaction, and boron is further lost during the alkali washing process. Compared with Example 1, the coprecipitation boron doping method uses more boron at the same boron content. Compared with the coprecipitation method, the boron doping achieved by adsorption in the present disclosure has little effect on the discharge capacity and cycle performance, but the adsorption doping has a higher utilization efficiency of boron, and the boron-containing aqueous solution can be reused many times, and the cost is low. It can be concluded from Examples 1 and 14 that the recovered boron-containing aqueous solution has little effect on the performance of the positive electrode material.

It can be concluded from Example 1 and Example 15 that the doping efficiency of sodium borohydride is lower than that of boric acid.

Claims (15)

A boron-doped positive electrode material precursor comprises a boron-doped metal hydroxide, wherein the chemical formula of the boron-doped metal _hydroxide is _MnBd (OH) ₂ , wherein M is a metal element and n+d=1. The boron-doped positive electrode material precursor according to claim 1, wherein the boron content in the boron-doped positive electrode material precursor is 500 to 8000 ppm; Optionally, 0.001≤d≤0.07; Optionally, M includes any one of Ni, Co or Mn, or a combination of at least two of them. The boron-doped positive electrode material precursor according to claim 2, wherein M also includes Al. The boron-doped cathode material precursor according to claim 1, wherein the chemical formula of the boron-doped metal hydroxide is _NiaCobXcBd ( _OH ) ₂ , wherein 0.5≤a≤0.9, _{0.02≤b≤0.5} , 0.02≤c≤0.5, _{0.001≤d≤0.07} , a+b+c+d=1, and X includes Mn and/or Al. The boron-doped positive electrode material precursor according to any one of claims 1 to 4, wherein the boron-doped metal hydroxide is a homogeneous solid solution; Optionally, the specific surface area of the boron-doped metal hydroxide is 6 to 45 m ² /g; Optionally, the porosity of the boron-doped metal hydroxide is 0.01% to 0.18%. A method for preparing a boron-doped positive electrode material precursor comprises the following steps: The metal hydroxide raw material is mixed with a solution containing borate ions, and heated to react to obtain a boron-doped positive electrode material precursor. The preparation method according to claim 6, wherein the metal hydroxide raw material comprises M(OH) ₂ , wherein M is a metal element; Optionally, M includes any one or a combination of at least two of Ni, Co or Mn; Optionally, M also includes Al; Optionally, the metal hydroxide raw material is Ni _a Co _b X _c (OH) ₂ , wherein 0.5≤a≤0.9, 0.05≤b≤0.5, 0.05≤c≤0.5, a+b+c=1, and X includes Mn and/or Al. The preparation method according to claim 6 or 7, wherein the specific surface area of the metal hydroxide raw material is 6 to 45 m ² /g; Optionally, the porosity of the metal hydroxide raw material is 0.01% to 0.18%. The preparation method according to any one of claims 6 to 8, wherein the method for preparing the solution containing borate ions comprises: dissolving any one or a combination of at least two of boric acid, borax or boron trioxide in water; Optionally, in the solution containing borate ions, the molar concentration of boron element is 0.1 to 3 mol/L; Optionally, the molar amount of the metal hydroxide raw material is 1 to 50 times the molar amount of the boron element in the solution containing borate ions; Optionally, the heating reaction method includes any one of water bath heating, microwave heating, ultrasonic heating or hydrothermal kettle heating, or a combination of at least two thereof; Optionally, the temperature of the heating reaction is 50 to 150°C; Optionally, the heating reaction time is 2 to 8 hours. The preparation method according to any one of claims 6 to 9, wherein the preparation method further comprises performing solid-liquid separation after the heating reaction, and washing, drying, sieving and demagnetizing the separated solid in sequence to obtain the boron-doped positive electrode material precursor; Optionally, the solid-liquid separation comprises centrifugation; Optionally, the washing liquid for washing comprises pure water; Optionally, the separation liquid is used as a solution containing borate ions. A positive electrode material, wherein the positive electrode material is prepared using the boron-doped positive electrode material precursor according to any one of claims 1 to 5. A method for preparing the positive electrode material according to claim 11, the method comprising the following steps: The boron-doped positive electrode material precursor according to any one of claims 1 to 5 is mixed with a lithium salt and sintered. junction to obtain the positive electrode material. The method according to claim 12, wherein the ratio of the total molar amount of the metal element in the boron-doped positive electrode material precursor to the molar amount of the lithium element in the lithium salt is 1:(0.99-1.04); Optionally, the lithium salt comprises lithium hydroxide; Optionally, the sintering is performed in an oxygen-containing atmosphere; Optionally, the sintering is a two-stage sintering; Optionally, the heating rate of the first stage of the two-stage sintering is 1-3°C/min, the holding temperature is 400-440°C, and the holding time is 3-5h; Optionally, the heating rate of the second stage sintering in the two-stage sintering is 1-3°C/min, the holding temperature is 700-740°C, and the holding time is 7-9h. A positive electrode sheet comprising the positive electrode material according to claim 12. A lithium ion battery comprising the positive electrode sheet according to claim 14.