阅读说明：本技术 锂离子电池负极材料及其制备方法和应用 (Lithium ion battery cathode material and preparation method and application thereof ) 是由 权泽卫 侯振 赵西夏 于 2019-08-16 设计创作，主要内容包括：本发明属于锂离子电池技术领域,尤其涉及一种锂离子电池负极材料的制备方法,包括：在惰性气体氛围下,将锡前驱体与有机溶剂混合后,添加表面活性剂升温至200～215℃,再添加还原剂反应5～10分钟后；然后添加锑前驱体反应5～7分钟,形成锡锑纳米晶合金粗产物；最后,通过短链配体置换得到粒径均匀的锡锑纳米晶合金负极材料。本发明制得的粒径均匀的锡锑纳米晶合金负极材料作为一种双金属合金材料,由于锡和锑与锂离子的合金化反应电位不同,可以有效抑制充放电过程中负极材料的体积变化和材料内部产生的应力对材料结构的破坏,从而维持材料结构的稳定性,有效提高了锂离子电池的循环稳定性和安全性能,且具备高理论容量。(The invention belongs to the technical field of lithium ion batteries, and particularly relates to a preparation method of a lithium ion battery cathode material, which comprises the following steps: mixing a tin precursor with an organic solvent under an inert gas atmosphere, adding a surfactant, heating to 200-215 ℃, adding a reducing agent, and reacting for 5-10 minutes; then adding an antimony precursor for reaction for 5-7 minutes to form a crude product of the tin-antimony nanocrystalline alloy; and finally, replacing the short-chain ligand to obtain the tin-antimony nanocrystalline alloy cathode material with uniform particle size. The tin-antimony nanocrystalline alloy cathode material with uniform particle size, which is prepared by the invention, is used as a bimetallic alloy material, and because of different alloying reaction potentials of tin, antimony and lithium ions, the volume change of the cathode material and the damage of stress generated in the material to the material structure in the charging and discharging process can be effectively inhibited, so that the stability of the material structure is maintained, the cycle stability and the safety performance of a lithium ion battery are effectively improved, and the bimetallic alloy cathode material has high theoretical capacity.)

1. The preparation method of the lithium ion battery negative electrode material is characterized by comprising the following steps of:

obtaining a tin precursor, and mixing and degassing the tin precursor and an organic solvent under an inert gas atmosphere to obtain a first reaction solution;

obtaining a surfactant, adding the surfactant into the first reaction liquid under an inert gas atmosphere, and heating to 200-215 ℃ to obtain a second reaction liquid;

obtaining a reducing agent, adding the reducing agent into the second reaction liquid under the inert gas atmosphere, and reacting for 5-10 minutes to obtain a third reaction liquid;

obtaining an antimony precursor, adding the antimony precursor into the third reaction liquid in an inert gas atmosphere, reacting for 5-7 minutes, and purifying to obtain a crude product of the tin-antimony nanocrystalline alloy;

and obtaining a short-chain ligand, and mixing the short-chain ligand with the crude product of the tin-antimony nanocrystalline alloy to obtain the tin-antimony nanocrystalline alloy cathode material.

2. The method for preparing the negative electrode material of the lithium ion battery according to claim 1, wherein the molar ratio of the surfactant to the reducing agent to the antimony precursor to the tin precursor is (0.05-0.1): 1:1: (2-4).

3. The method for preparing the negative electrode material for the lithium ion battery according to claim 1 or 2, wherein the step of performing mixed degassing treatment of the tin precursor and the organic solvent comprises: and mixing the organic solvent and the tin precursor in an inert gas atmosphere, and then carrying out vacuum degassing for 5-10 minutes to obtain a first reaction solution.

4. The preparation method of the negative electrode material for the lithium ion battery according to claim 3, wherein the step of adding the surfactant to the first reaction solution and raising the temperature to 200-215 ℃ comprises: and adding the surfactant into the first reaction liquid, and heating to 200-215 ℃ at a speed of 5-10 ℃/min to obtain a second reaction liquid.

5. The method for preparing the negative electrode material for the lithium ion battery according to claim 1, 2 or 4, wherein the tin precursor is selected from stannous chloride and/or stannic chloride; and/or the presence of a gas in the gas,

the organic solvent is a mixed solution of oleylamine and 1-octadecene, wherein the mixing ratio of oleylamine to 1-octadecene is 1: (7.5-10); and/or the presence of a gas in the gas,

the surfactant is selected from hexamethyldisilazane and/or tri-n-octylphosphine; and/or the presence of a gas in the gas,

the reducing agent is selected from tungsten carbonyl and/or carbon monoxide; and/or the presence of a gas in the gas,

the antimony precursor is selected from antimony chloride and/or antimony triiodide; and/or the presence of a gas in the gas,

the short-chain ligand is selected from n-butylamine and/or thiol.

6. The method for preparing the negative electrode material for the lithium ion battery according to claim 5, wherein the step of adding the reducing agent to the second reaction solution comprises: under the inert gas atmosphere, obtaining tungsten carbonyl and dissolving the tungsten carbonyl in an organic solvent to obtain a tungsten carbonyl solution with the concentration of 10 mg/ml-20 mg/ml; then adding the tungsten carbonyl solution into the second reaction solution; and/or the presence of a gas in the gas,

the step of adding the antimony precursor to the third reaction liquid includes: and (3) dissolving antimony chloride in an organic solvent under an inert gas atmosphere to obtain an antimony precursor solution with the concentration of 10-20 mg/ml, and adding the antimony precursor solution into the third reaction solution.

7. The method for preparing the negative electrode material of the lithium ion battery according to claim 1, 2, 4 or 6, wherein the purification treatment step comprises: and adding the antimony precursor into the third reaction liquid, reacting for 5-7 minutes, cooling to room temperature, and carrying out centrifugal treatment for 2-3 times by using acetone or a mixed solution of n-hexane and ethanol as an eluent to obtain a crude product of the tin-antimony nanocrystalline alloy.

8. The method for preparing the negative electrode material of the lithium ion battery according to claim 7, wherein the step of mixing the short-chain ligand with the crude tin-antimony nanocrystalline alloy product comprises the following steps: and mixing the short-chain ligand with the crude product of the tin-antimony nanocrystalline alloy, stirring for more than 10 hours, and separating to obtain the tin-antimony nanocrystalline alloy cathode material.

9. The lithium ion battery negative electrode material is characterized by comprising a tin-antimony nanocrystalline alloy, wherein the grain diameter of the tin-antimony nanocrystalline alloy is 15-30 nanometers.

10. A lithium ion battery is characterized by comprising a positive electrode, a negative electrode, a separator and an electrolyte, wherein the negative electrode comprises the lithium ion battery negative electrode material prepared by the method of any one of claims 1 to 8 or the lithium ion battery negative electrode material of claim 9.

Technical Field

The invention belongs to the technical field of lithium ion batteries, and particularly relates to a lithium ion battery cathode material and a preparation method thereof, namely a lithium ion battery.

Background

The lithium ion battery has the advantages of high voltage, large energy density, stable discharge voltage, good low-temperature performance, excellent safety performance, long storage and service life, small self-discharge, no memory effect, wide working temperature range, environmental friendliness and the like, is an ideal chemical energy source recognized by the society at present, is an energy storage and conversion device commonly used in modern life, and is widely applied to portable electronic devices such as mobile phones, portable computers and the like, large-scale energy storage power stations and electric automobiles. A lithium ion battery is a secondary battery (recyclable) that mainly operates by movement of lithium ions between a positive electrode and a negative electrode. During charging and discharging, Li⁺Intercalation and deintercalation to and from two electrodes: upon charging, Li⁺The lithium ion battery is extracted from the positive electrode and is inserted into the negative electrode through the electrolyte, and the negative electrode is in a lithium-rich state; the opposite is true during discharge. With the rapid development of science and technology and economy in modern society and the rapid development of new energy automobiles, smart grids, communication base stations and other emerging fields, not only higher requirements on the electrical properties such as energy density, service life and the like of lithium ion batteries are provided, but also higher and higher requirements on the safety such as stability and the like of the lithium ion batteries are provided.

At present, the actual energy density of a lithium ion battery system taking graphite (with the theoretical capacity of 372mAh/g) as a negative electrode is gradually close to the theoretical limit value, which cannot meet the urgent demand of the rapid development of social science and technology and economy on the energy density of the battery. The alloy negative electrode material has larger theoretical lithium storage capacity and lower lithium storage potential compared with graphite. Wherein the tin cathode is capable of forming Li with Li₂₂Sn₅The alloy has a high theoretical capacity of 993mAh/g, and is considered to be one of the most promising substitutes for the graphite cathode material of the lithium ion battery. However, the volume expansion of the tin negative electrode material is greatly changed during the charge and discharge processes, which causes pulverization and cracking of the active material, thereby directly causing a great reduction in the electrode capacity and deterioration in cycle performance.

Disclosure of Invention

The invention aims to provide a preparation method of a lithium ion battery cathode material, and aims to solve the technical problems that the volume expansion change of the existing lithium ion battery tin cathode material is huge in the charging and discharging processes, so that the active substance is pulverized and cracked, the electrode capacity is directly reduced greatly, and the cycle performance is deteriorated.

The invention also aims to provide a lithium ion battery cathode material.

Another object of the present invention is to provide a lithium ion battery.

In order to achieve the purpose of the invention, the technical scheme adopted by the invention is as follows:

a preparation method of a lithium ion battery negative electrode material comprises the following steps:

obtaining a tin precursor, and mixing and degassing the tin precursor and an organic solvent under an inert gas atmosphere to obtain a first reaction solution;

obtaining a surfactant, adding the surfactant into the first reaction liquid under an inert gas atmosphere, and heating to 200-215 ℃ to obtain a second reaction liquid;

obtaining a reducing agent, adding the reducing agent into the second reaction liquid under the inert gas atmosphere, and reacting for 5-10 minutes to obtain a third reaction liquid;

obtaining an antimony precursor, adding the antimony precursor into the third reaction liquid in an inert gas atmosphere, reacting for 5-7 minutes, and purifying to obtain a crude product of the tin-antimony nanocrystalline alloy;

and obtaining a short-chain ligand, and mixing the short-chain ligand with the crude product of the tin-antimony nanocrystalline alloy to obtain the tin-antimony nanocrystalline alloy cathode material.

Preferably, the molar ratio of the surfactant, the reducing agent, the antimony precursor and the tin precursor is (0.05-0.1): 1:1: (2-4).

Preferably, the step of performing a mixed degassing treatment of the tin precursor with an organic solvent includes: and mixing the organic solvent and the tin precursor in an inert gas atmosphere, and then carrying out vacuum degassing for 5-10 minutes to obtain a first reaction solution.

Preferably, the step of adding the surfactant to the first reaction solution and raising the temperature to 200-215 ℃ comprises: and adding the surfactant into the first reaction liquid, and heating to 200-215 ℃ at a speed of 5-10 ℃/min to obtain a second reaction liquid.

Preferably, the tin precursor is selected from stannous chloride and/or stannic chloride; and/or the presence of a gas in the gas,

the organic solvent is a mixed solution of oleylamine and 1-octadecene, wherein the mixing ratio of oleylamine to 1-octadecene is 1: (7.5-10); and/or the presence of a gas in the gas,

the surfactant is selected from hexamethyldisilazane and/or tri-n-octylphosphine; and/or the presence of a gas in the gas,

the reducing agent is selected from tungsten carbonyl and/or carbon monoxide; and/or the presence of a gas in the gas,

the antimony precursor is selected from antimony chloride or antimony triiodide; and/or the presence of a gas in the gas,

the short-chain ligand is selected from n-butylamine and/or thiol.

Preferably, the step of adding the reducing agent to the second reaction liquid includes: under the inert gas atmosphere, obtaining tungsten carbonyl and dissolving the tungsten carbonyl in an organic solvent to obtain a tungsten carbonyl solution with the concentration of 10-20 mg/ml; then adding the tungsten carbonyl solution into the second reaction solution; and/or the presence of a gas in the gas,

the step of adding the antimony precursor to the third reaction liquid includes: and dissolving antimony chloride in an organic solvent under an inert gas atmosphere to obtain an antimony precursor solution with the concentration of 10-20 mg/ml, and adding the antimony precursor solution into the third reaction solution.

Preferably, the step of purifying comprises: and adding the antimony precursor into the third reaction liquid, reacting for 5-7 minutes, cooling to room temperature, and carrying out centrifugal treatment for 2-3 times by using acetone or a mixed solution of n-hexane and ethanol as an eluent to obtain a crude product of the tin-antimony nanocrystalline alloy.

Preferably, the step of mixing the short-chain ligand and the crude tin-antimony nanocrystalline alloy product comprises the following steps: and mixing the short-chain ligand with the crude product of the tin-antimony nanocrystalline alloy, stirring for more than 10 hours, and separating to obtain the tin-antimony nanocrystalline alloy cathode material.

The lithium ion battery cathode material comprises a tin-antimony nanocrystalline alloy, wherein the grain size of the tin-antimony nanocrystalline alloy is 15-30 nanometers.

A lithium ion battery comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, wherein the negative electrode contains the lithium ion battery negative electrode material prepared by the method or contains the lithium ion battery negative electrode material.

The preparation method of the lithium ion battery cathode material provided by the invention comprises the steps of mixing a tin precursor with an organic solvent in an inert gas atmosphere, adding a surfactant, heating to 200-215 ℃, adding a reducing agent, reacting for 5-10 minutes, and reducing the tin precursor into tin nanocrystals under the action of the surfactant and the reducing agent by controlling the reaction temperature and the reaction time; then, adding an antimony precursor, and reacting for 5-7 minutes at the temperature of the reaction system (200-215 ℃), so that the antimony in the antimony precursor and the tin nanocrystals are subjected to coordination displacement to form a crude tin-antimony nanocrystal alloy product; and finally, replacing the long-chain ligand on the surface of the crude product of the tin-antimony nanocrystalline alloy with a short chain through the short-chain ligand to obtain the tin-antimony nanocrystalline alloy cathode material with uniform particle size. The preparation method provided by the invention is simple to operate, and easy to realize batch production and application, and the prepared tin-antimony nanocrystalline alloy cathode material with uniform particle size is used as a bimetallic alloy material, not only has high theoretical capacity, but also has an extremely thick potential advantage.

The lithium ion battery cathode material provided by the invention comprises a tin-antimony nanocrystalline alloy material, the particle size of the tin-antimony nanocrystalline alloy material is 15-30 nanometers, and the alloy material can be prepared by the preparation method.

The lithium ion battery provided by the invention contains the lithium ion battery cathode material which has the advantages of high theoretical capacity, good stability, small volume change, difficult pulverization or cracking, good safety performance and obvious potential advantage, so the lithium ion battery also has the advantages of good cycle stability, high capacity, safety, long cycle life and the like.

Drawings

Fig. 1 is an X-ray diffraction spectrum of a tin-antimony nanocrystalline alloy (left) and tin and antimony nanocrystals (right) provided in an embodiment of the present invention.

Fig. 2 is a transmission electron microscope image of tin-antimony nanocrystalline alloy (a), antimony nanocrystals (b), and tin nanocrystals (c) provided in an embodiment of the present invention.

Fig. 3 is a graph showing the cycle performance and coulombic efficiency test at 100mAh/g for the lithium ion batteries provided in example 1 and comparative examples 1 and 2 of the present invention.

Fig. 4 is a graph of the cycle performance and coulombic efficiency test at 200mAh/g for the lithium ion batteries provided in example 1 and comparative examples 1 and 2 of the present invention.

Fig. 5 is a rate capability test chart of the lithium ion batteries provided in example 1 and comparative examples 1 and 2 of the present invention.

Detailed Description

In order to make the purpose, technical solution and technical effect of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention is clearly and completely described, and it is obvious that the described embodiments are a part of the embodiments of the present invention, but not all embodiments. All other embodiments obtained by a person of ordinary skill in the art without any inventive step in connection with the embodiments of the present invention shall fall within the scope of protection of the present invention.

In the description of the present invention, it is to be understood that the terms "first", "second" and the like are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implying any number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless specifically defined otherwise.

The weight of the related components mentioned in the description of the embodiments of the present invention may not only refer to the specific content of each component, but also represent the proportional relationship of the weight among the components, and therefore, the content of the related components is scaled up or down within the scope disclosed in the description of the embodiments of the present invention as long as it is in accordance with the description of the embodiments of the present invention. Specifically, the weight described in the description of the embodiment of the present invention may be a unit of mass known in the chemical industry field, such as μ g, mg, g, and kg.

The embodiment of the invention provides a preparation method of a lithium ion battery cathode material, which comprises the following steps:

s10, obtaining a tin precursor, and mixing and degassing the tin precursor and an organic solvent in an inert gas atmosphere to obtain a first reaction solution;

s20, obtaining a surfactant, adding the surfactant into the first reaction liquid in an inert gas atmosphere, and heating to 200-215 ℃ to obtain a second reaction liquid;

s30, obtaining a reducing agent, adding the reducing agent into the second reaction liquid in an inert gas atmosphere, and reacting for 5-10 minutes to obtain a third reaction liquid;

s40, obtaining an antimony precursor, adding the antimony precursor into the third reaction liquid in an inert gas atmosphere, reacting for 5-7 minutes, and purifying to obtain a crude tin-antimony nanocrystalline alloy product;

s50, obtaining a short-chain ligand, and mixing the short-chain ligand with the tin-antimony nanocrystalline alloy crude product to obtain the tin-antimony nanocrystalline alloy cathode material.

According to the preparation method of the lithium ion battery cathode material provided by the embodiment of the invention, under the inert gas atmosphere, after a tin precursor is mixed with an organic solvent, a surfactant is added, the temperature is raised to 200-215 ℃, a reducing agent is added, and after the reaction is carried out for 5-10 minutes, the tin precursor is reduced into tin nanocrystals under the action of the surfactant and the reducing agent by controlling the reaction temperature and the reaction time; then, adding an antimony precursor, and reacting for 5-7 minutes at the temperature of the reaction system (200-215 ℃), so that the antimony in the antimony precursor and the tin nanocrystals are subjected to coordination displacement to form a crude tin-antimony nanocrystal alloy product; and finally, replacing the long-chain ligand on the surface of the crude product of the tin-antimony nanocrystalline alloy with a short chain through the short-chain ligand to obtain the tin-antimony nanocrystalline alloy cathode material with uniform particle size. The preparation method provided by the embodiment of the invention is simple to operate, and easy to realize batch production and application, and the prepared tin-antimony nanocrystalline alloy cathode material with uniform particle size has high theoretical capacity and unique potential advantage as a bimetallic alloy material, and can effectively inhibit the volume change of the cathode material and the damage of stress generated in the material to the material structure in the charging and discharging process due to different alloying reaction potentials of tin, antimony and lithium ions, so that the stability of the material structure is maintained, and the cycle stability and the safety performance of a lithium ion battery are effectively improved.

In a preferred embodiment, the size of the tin-antimony nanocrystalline alloy is 15-30 nanometers, and the tin-antimony nanocrystalline alloy negative electrode material with a small particle size not only has a better active specific surface area, but also has better expansion and contraction performance and higher stability compared with the alloy with a large particle size and a small particle size, and is beneficial to improving the cycling stability of the negative electrode material.

Specifically, in step S10, a tin precursor is obtained, and the tin precursor and an organic solvent are mixed and degassed in an inert gas atmosphere to obtain a first reaction solution. According to the embodiment of the invention, after the tin precursor is obtained in the inert gas atmosphere, the tin precursor and the organic solvent are subjected to mixed degassing treatment, so that the tin precursor is dissolved in the organic solvent, oxygen dissolved in a mixed reaction system of the tin precursor and the organic solvent is removed through degassing treatment, oxidation of tin, antimony and tin-antimony alloy in subsequent reaction by the oxygen is avoided, and side reaction is prevented.

As a preferred embodiment, the step of performing a mixed degassing treatment of the tin precursor with an organic solvent includes: and mixing the organic solvent and the tin precursor in an inert gas atmosphere, and then carrying out vacuum degassing for 5-10 minutes to obtain a first reaction solution. According to the embodiment of the invention, the mixed solution of the organic solvent and the tin precursor is subjected to vacuum degassing for 5-10 minutes, so that oxygen in the mixed solution is fully removed, oxidation of tin, antimony and tin-antimony alloy in subsequent reaction by the oxygen is avoided, and side reaction is prevented. In some embodiments, the vacuum degassing time may be 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, or 10 minutes.

As a preferred embodiment, the tin precursor is stannous chloride and/or stannic chloride. The tin precursor in the embodiment of the invention is stannous chloride, stannic chloride or a mixture of the stannous chloride and the stannic chloride, and the selected tin precursor is beneficial to the subsequent reduction process, so that the tin precursor can be quickly reduced, and thus, the tin nanocrystals in the reaction system have the same nucleation rate and conditions, and the tin nanocrystals with proper particle size are obtained. The subsequent coordination displacement reaction of antimony to the tin nanocrystals is facilitated, so that the uniform tin-antimony nanocrystal alloy is prepared, and if the iodine salt or other tin precursors are adopted, the uniform tin-antimony nanocrystal alloy cannot be obtained in the subsequent preparation process.

As a more preferable embodiment, the tin precursor is stannous chloride, and the stannic chloride has better reduction performance and is more beneficial to the preparation of the tin-antimony nanocrystalline alloy.

As a preferred embodiment, the organic solvent is a mixed solution of oleylamine and 1-octadecene, wherein the mixing ratio of oleylamine and 1-octadecene is 1: (7.5-10). According to the embodiment of the invention, the mixed solution of oleylamine and 1-octadecene is used as the organic solvent of the system, on one hand, the two solvents have high solubility to each raw material, so that each raw material is fully dissolved in the organic solvent, and an environment system is provided for mutual contact and reaction among all substances; oleylamine and 1-octadecene, on the other hand, were present in a ratio of 1: (7.5-10), wherein the oleylamine has a certain reduction coordination capacity, the reduction speed of a subsequent precursor can be influenced by adjusting the reasonable mixing ratio of oleylamine and 1-octadecene, and the ratio of (1: the mixing ratio of (7.5-10) is most beneficial to the reduction of the precursor in the reaction system, so that the formation of the tin-antimony nanocrystalline alloy is improved, and the reaction efficiency is improved.

In some embodiments, the mixing ratio of the oleylamine and the 1-octadecene may be 1: 9. 1: 10. 1.2: 9 or, 1.2: 10, etc.

In some embodiments, the tin precursor is stannous chloride and/or stannic chloride; the organic solvent is a mixed solution of oleylamine and 1-octadecene, wherein the mixing ratio of oleylamine to 1-octadecene is 1: (7.5-10).

Specifically, in the step S20, a surfactant is obtained, and the surfactant is added to the first reaction solution under an inert gas atmosphere, and the temperature is raised to 200 to 215 ℃ to obtain a second reaction solution. After the surfactant is obtained, the surfactant is added into the first reaction solution in the atmosphere of inert gas, and then the temperature is raised to 200-215 ℃ so that the tin precursor is fully dissolved in the organic solvent. The surface active agent not only can effectively control the replacement rate of the tin nano-crystal by the subsequent antimony, but also can enable the crystal face of the subsequently generated tin-antimony alloy to be more uniform, and the tin-antimony nano-crystal alloy with uniform grain size is formed. If the temperature is too low, the solubility of the tin precursor is poor, and the mutual reaction among substances is influenced; if the temperature is too high, the tin simple substance will be melted and agglomerated, and the tin nano-crystal cannot be formed, and the tin-antimony nano-crystal alloy cannot be prepared.

In some embodiments, after the surfactant is captured, it is added to the first reaction solution under an inert gas atmosphere and then warmed to 200 ℃, 205 ℃, 210 ℃, or 215 ℃.

In a preferred embodiment, the step of adding the surfactant to the first reaction solution and raising the temperature to 200 to 215 ℃ comprises: and adding the surfactant into the first reaction liquid, and heating to 200-215 ℃ at a speed of 5-10 ℃/min to obtain a second reaction liquid. Because oleylamine in the organic solution has a certain reduction effect, the temperature of a reaction system formed by the surfactant and the first reaction liquid is increased to 200-215 ℃ at the temperature increase rate of 5-10 ℃/min, the temperature increase rate is most beneficial to forming tin nanoparticles with proper size by a tin precursor, and if the temperature increase rate is too high, the formed tin particles are too large, so that the subsequent replacement reaction of antimony on the tin nanoparticles is not facilitated, and the tin-antimony nanocrystalline alloy cannot be obtained; if the temperature rise rate is too slow, the formed tin particles are too small, the small tin particles are not beneficial to the subsequent replacement of antimony, the antimony is easy to nucleate by itself, and the tin-antimony nanocrystalline alloy cannot be obtained.

In some embodiments, the surfactant is added to the first reaction solution, and the temperature is raised to 200-215 ℃ at a rate of 5 ℃/min, 6 ℃/min, 7 ℃/min, 8 ℃/min, 9 ℃/min, or 10 ℃/min to obtain a second reaction solution.

As a preferred embodiment, the surfactant is selected from hexamethyldisilazane and/or tri-n-octylphosphine. The hexamethyldisilazane and/or tri-n-octylphosphine surfactant adopted in the embodiment of the invention has a good promoting effect on the generation of the tin-antimony nanocrystalline alloy with uniform grain size, and can control the generation rate of the tin-antimony nanocrystalline alloy, thereby controlling the size of the tin-antimony nanocrystalline alloy, and optimizing the crystal phase surface of the tin-antimony nanocrystalline alloy, so that the prepared tin-antimony nanocrystalline alloy has uniform grain size and more regular morphology, and is beneficial to improving the electrochemical performance of a negative electrode material. More preferably, the surfactant is selected from hexamethyldisilazane.

Specifically, in the step S30, a reducing agent is obtained, and the reducing agent is added to the second reaction solution in an inert gas atmosphere to react for 5 to 10 minutes, so as to obtain a third reaction solution. According to the embodiment of the invention, the reducing agent is added into the second reaction solution at 205-215 ℃ in the atmosphere of inert gas to react for 5-10 minutes, under the high-temperature reaction condition, each substance component in the reaction system has the best reaction activity, and the reducing agent rapidly reduces all tin precursors in the reaction system into the tin simple substance at the same time, so that the tin precursors are rapidly reduced, and the tin simple substance has the same growth condition. The reaction time is controlled to be 5-10 minutes, and the growth time of the tin nano-crystal is controlled, so that the size of tin nano-crystal particles is controlled, and the formed tin particles have the most appropriate particle size and are convenient for the subsequent antimony replacement reaction. If the reaction time is too long, the formed tin nanocrystalline particles are too large, which is not beneficial to the subsequent replacement reaction of antimony on the tin nanocrystalline particles and cannot obtain the tin-antimony nanocrystalline alloy; if the reaction time is too short, the formed tin particles are too small, the too small tin particles are not beneficial to the replacement of the subsequent antimony, the antimony is easy to nucleate by itself, and the tin-antimony nanocrystalline alloy cannot be obtained.

As a preferred embodiment, the reducing agent is selected from tungsten carbonyls and/or carbon monoxide. According to the embodiment of the invention, tungsten carbonyl, carbon monoxide or a mixture of the tungsten carbonyl and the carbon monoxide are used as a reducing agent, so that the tin precursor has the best reduction effect, the tin precursor is rapidly reduced to generate a tin simple substance, tin nanocrystalline particles with uniform particle size are generated in a reaction system, and the subsequent replacement reaction of antimony is facilitated. The reducing agent in the embodiment of the invention can also adopt any other reducing agent capable of realizing the effect of the invention. More preferably, the reducing agent is selected from tungsten carbonyls.

As a preferred embodiment, the step of adding the reducing agent to the second reaction liquid includes: under the inert gas atmosphere, obtaining tungsten carbonyl and dissolving the tungsten carbonyl in an organic solvent to obtain a tungsten carbonyl solution with the concentration of 10-20 mg/ml; and then adding the tungsten carbonyl solution to the second reaction solution. According to the embodiment of the invention, the reducing agent is firstly dissolved in the organic solvent and then added into the reaction system in the form of the solvent, so that the reducing agent can be rapidly and uniformly dispersed in the reaction system after being added into the reaction system, and can be timely and fully contacted with the tin precursor, thereby being beneficial to the reduction reaction of the reducing agent on the tin precursor. In order to avoid the influence of a newly added solvent on the temperature and dissolved oxygen of a reaction system, the reducing agent is added in the form of a solution with the concentration of 10-20 mg/ml. In some embodiments, the concentration of the tungsten carbonyl solution can be 10mg/ml, 12mg/ml, 14mg/ml, 16mg/ml, 18mg/ml, or 20 mg/ml.

In some embodiments, the step of adding the reducing agent to the second reaction liquid comprises: under the inert gas atmosphere, obtaining tungsten carbonyl and dissolving the tungsten carbonyl in methylbenzene to obtain a tungsten carbonyl solution with the concentration of (10-20) mg/ml; and then adding the tungsten carbonyl solution to the second reaction solution.

Specifically, in the step S40, obtaining an antimony precursor, adding the antimony precursor to the third reaction solution in an inert gas atmosphere, reacting for 5-7 minutes, and purifying to obtain a crude product of the tin-antimony nanocrystalline alloy. According to the embodiment of the invention, an antimony precursor is obtained under inert gas and then added into a third reaction solution with the reaction temperature of 205-215 ℃, and the reaction time is controlled to be 5-7 minutes, so that tin nanocrystalline particles are partially replaced by antimony, and the tin-antimony nanocrystalline alloy is formed. If the reaction time is too short, the replacement of the tin nanocrystals by antimony is insufficient, and the tin-antimony nanocrystal alloy with uniform particle size and excellent performance cannot be obtained; if the reaction time is too long, the tin nanocrystals are completely replaced by the active metal antimony to form antimony nanocrystal particles, and the tin returns to the solvent in an ionic form, so that the tin-antimony nanocrystal alloy cannot be obtained.

As a preferred embodiment, the antimony precursor is selected from antimony chloride and/or antimony triiodide. According to the embodiment of the invention, antimony chloride and/or antimony triiodide are/is used as an antimony precursor, so that the replacement reaction of antimony on tin nanocrystalline particles in a reaction system is facilitated, and the uniform tin-antimony nanocrystalline alloy is obtained. More preferably, the antimony precursor is selected from antimony chloride.

As a preferred embodiment, the step of adding the antimony precursor to the third reaction liquid includes: and dissolving antimony chloride in an organic solvent under an inert gas atmosphere to obtain an antimony precursor solution with the concentration of 10-20 mg/ml, and adding the antimony precursor solution into the third reaction solution. According to the embodiment of the invention, the antimony precursor is firstly dissolved in the organic solvent, and then the solvent is added into the reaction system, so that the antimony precursor can be rapidly and uniformly dispersed in the reaction system after being added into the reaction system and is fully contacted with the tin nano-crystal, uniform replacement reaction of antimony on tin nano-crystal particles is facilitated, and uniform tin-antimony nano-gold alloy is obtained. In order to avoid the influence of a newly added solvent on the temperature and dissolved oxygen of a reaction system, antimony precursor antimony chloride is added in the form of a solution with the concentration of 10-20 mg/ml. In one embodiment, the concentration of the antimony chloride solution may be 10mg/ml, 12mg/ml, 14mg/ml, 16mg/ml, 18mg/ml, or 20 mg/ml.

In some embodiments, the step of adding the antimony precursor to the third reaction liquid comprises: and dissolving antimony chloride in toluene under the inert gas atmosphere to obtain an antimony precursor solution with the concentration of 10-20 mg/ml, and adding the antimony precursor solution into the third reaction solution.

As a preferred embodiment, the step of purifying treatment comprises: and adding the antimony precursor into the third reaction liquid, reacting for 5-7 minutes, cooling to room temperature, and carrying out centrifugal treatment for 2-3 times by using acetone or a mixed solution of n-hexane and ethanol as an eluent to obtain a crude product of the tin-antimony nanocrystalline alloy. The method comprises the step of washing and purifying a solution after reaction cooling by using acetone or a mixed solution of normal hexane and ethanol as an eluent, wherein the acetone and the normal hexane have good dispersion solubility on a crude product of the tin-antimony nanocrystalline alloy, and the ethanol can dissolve an organic solvent, so that organic solvents such as oleylamine and 1-octadecene are removed, and the crude product of the tin-antimony nanocrystalline alloy is obtained.

In some embodiments, the antimony precursor is added into the third reaction solution, the reaction is carried out for 5 to 7 minutes, then the reaction solution is cooled to room temperature, and the crude product of the tin-antimony nanocrystalline alloy is obtained by taking a 1:1 mixed solution of acetone or n-hexane and ethanol as an eluent and carrying out centrifugal treatment for 2 to 3 times.

Specifically, in step S50, a short-chain ligand is obtained, and the short-chain ligand and the coarse product of the tin-antimony nanocrystalline alloy are mixed to obtain the tin-antimony nanocrystalline alloy negative electrode material. According to the embodiment of the invention, the short-chain ligand and the tin-antimony nanocrystalline alloy crude product are mixed, the short-chain ligand attacks oleylamine and 1-octadecene long-chain ligand on the surface of the tin-antimony nanocrystalline alloy crude product and replaces the oleylamine and the 1-octadecene long-chain ligand into short chains, so that the electrochemical performance of the lithium ion battery negative electrode material is improved, the tin-antimony nanocrystalline alloy negative electrode material is obtained, and the tin-antimony nanocrystalline alloy crude product with the long chains on the surface can cause the ionic conductivity of the alloy to be poor and is not easy to generate physical and chemical reactions.

As a preferred embodiment, the step of mixing the short-chain ligand with the tin-antimony nanocrystalline alloy crude product comprises: and mixing the short-chain ligand with the crude product of the tin-antimony nanocrystalline alloy, stirring for more than 10 hours, and separating to obtain the tin-antimony nanocrystalline alloy cathode material. In the embodiment of the invention, the short-chain ligand is mixed with the crude product of the tin-antimony nanocrystalline alloy and then stirred for more than 10 hours, so that the short-chain ligand fully replaces the long chain on the surface of the crude product of the tin-antimony nanocrystalline alloy, and the tin-antimony nanocrystalline alloy is obtained.

In some embodiments, the step of mixing the short chain ligand with the tin-antimony nanocrystalline alloy raw product comprises: and mixing the short-chain ligand with the crude tin-antimony nanocrystalline alloy product, and stirring for 12 hours, 15 hours, 17 hours or 20 hours.

As a preferred embodiment, the short chain ligand includes, but is not limited to, n-butylamine, thiol, or mixtures thereof. According to the embodiment of the invention, n-butylamine and mercaptan are both short-chain ligands, and have a good replacement effect on long chains on the surface of the crude product of the tin-antimony nanocrystalline alloy.

As a preferred embodiment, the molar ratio of the surfactant, the reducing agent, the antimony precursor, and the tin precursor is (0.05 to 0.1): 1:1: (2-4). The molar ratio of the embodiment of the invention is (0.05-0.1): 1:1: and (2) the surfactant, the reducing agent, the antimony precursor and the tin precursor can effectively ensure the optimal reaction efficiency among the components of the substances, and are favorable for preparing the tin-antimony nanocrystalline alloy cathode material.

In some embodiments, the tin precursor is selected from stannous chloride and/or stannic chloride; the organic solvent is a mixed solution of oleylamine and 1-octadecene, wherein the mixing ratio of oleylamine to 1-octadecene is 1: (7.5-10); the surfactant is selected from hexamethyldisilazane and/or tri-n-octylphosphine; the reducing agent is selected from tungsten carbonyl and/or carbon monoxide; the antimony precursor is selected from antimony chloride and/or antimony triiodide; the short-chain ligand is selected from n-butylamine and/or thiol.

Correspondingly, the embodiment of the invention also provides a lithium ion battery cathode material, which comprises the tin-antimony nanocrystalline alloy, wherein the grain diameter of the tin-antimony nanocrystalline alloy is 15-30 nanometers.

The lithium ion battery cathode material provided by the embodiment of the invention comprises a tin-antimony nanocrystalline alloy material with the particle size of 15-30 nanometers, and the alloy material can be prepared by the preparation method.

Correspondingly, the lithium ion battery comprises a positive electrode, a negative electrode, a diaphragm and electrolyte, wherein the negative electrode contains the lithium ion battery negative electrode material prepared by the method or contains the lithium ion battery negative electrode material.

The lithium ion battery provided by the embodiment of the invention contains the lithium ion battery cathode material which has the advantages of high theoretical capacity, good stability, small volume change, difficult pulverization or cracking, good safety performance and obvious potential advantage, so the lithium ion battery also has the advantages of good cycle stability, high capacity, safety, long cycle life and the like.

In order to make the above implementation details and operations of the present invention clearly understood by those skilled in the art and to make the progress of the lithium ion battery anode material and the preparation method thereof obviously reflected, the above technical solutions are illustrated by a plurality of examples below.