阅读说明：本技术 一种改性天然石墨负极材料的制备方法 (Preparation method of modified natural graphite negative electrode material ) 是由 王胜彬 张超 张臻 黄杰 于 2019-11-19 设计创作，主要内容包括：本发明公开了一种改性天然石墨负极材料的制备方法,属于锂离子电池负极材料制备技术领域。本发明的制备方法先对天然石墨同时进行提纯及氧化扩层,分离过滤出固态物后并洗涤干燥,再对天然石墨进行整形处理得到类球形石墨粉,然后将有机包覆剂包覆于类球形石墨粉的表面上,冷却至室温后取出,在惰性气氛保护下进行高温炭化,冷却至室温后即得改性天然石墨。本发明的制备方法能够有效改善天然石墨负极材料的高倍率充放电性能及首次库伦效率,且工艺简单易控,成本低,易于工业化生产。(The invention discloses a preparation method of a modified natural graphite cathode material, and belongs to the technical field of preparation of lithium ion battery cathode materials. The preparation method comprises the steps of simultaneously purifying and oxidizing and expanding layers of natural graphite, separating and filtering solid substances, washing and drying, shaping the natural graphite to obtain spheroidal graphite powder, coating an organic coating agent on the surface of the spheroidal graphite powder, cooling to room temperature, taking out, carbonizing at high temperature under the protection of inert atmosphere, and cooling to room temperature to obtain the modified natural graphite. The preparation method can effectively improve the high-rate charge-discharge performance and the first coulombic efficiency of the natural graphite cathode material, and has the advantages of simple and easily-controlled process, low cost and easy industrial production.)

1. A preparation method of a modified natural graphite negative electrode material is characterized by comprising the following steps: the method comprises the following steps:

s1, purification and oxidation layer expansion: mixing natural graphite with an oxidant, an intercalating agent and hydrofluoric acid, purifying and expanding at 0-50 ℃ for 30-120 min, separating and filtering out a solid, washing the solid to a pH value of 5-7, and drying for later use;

s2, shaping: shaping the natural graphite processed in the step S1 into spheroidal graphite powder with D50 particle size of 5-30 μm;

s3, surface coating: placing the spheroidal graphite powder treated in the step S2 in a cavity of fluidized bed equipment, spraying a solution containing an organic coating agent into a fluidized bed for coating, wherein the coating reaction time is 0.5-2 h, and taking out the spheroidal graphite powder for later use after cooling to room temperature;

s4, high-temperature carbonization: and (5) heating the natural graphite obtained in the step (S3) to 600-1200 ℃ under the protection of inert atmosphere, preserving heat for 1-6 h, and taking out after cooling to room temperature to obtain the modified natural graphite.

2. The method for preparing the modified natural graphite negative electrode material according to claim 1, characterized in that: in the step S1, the mass ratio of the natural graphite to the oxidant, the intercalating agent and the hydrofluoric acid is 1: 0.03-1.5: 0.1-15: 0.05.

3. The method for preparing the modified natural graphite negative electrode material according to claim 1 or 2, characterized in that: the natural graphite in the step S1 is at least one of high-carbon graphite, high-purity graphite, and spherical graphite.

4. The method for preparing the modified natural graphite negative electrode material according to claim 1 or 2, characterized in that: the oxidant in step S1 is at least one of concentrated nitric acid, concentrated sulfuric acid, and hydrogen peroxide.

5. The method for preparing the modified natural graphite negative electrode material according to claim 1 or 2, characterized in that: the intercalation agent in the step S1 is at least one of concentrated nitric acid, phosphoric acid, formic acid, acetic acid and oxalic acid.

6. The method for preparing the modified natural graphite negative electrode material according to claim 1, characterized in that: in the step S3, the mass ratio of the organic coating agent to the spheroidal graphite powder is 0.001-0.1: 1.

7. the method for preparing the modified natural graphite negative electrode material according to claim 1 or 6, characterized in that: the mass fraction of the solution containing the organic coating agent in the step S3 is 1-65%.

8. The method for preparing the modified natural graphite negative electrode material according to claim 1 or 6, characterized in that: the organic coating agent in the step S3 is at least one of glucose, sucrose, phenolic resin, polyethylene glycol and asphalt; the solvent used in step S3 is at least one of deionized water, methanol, ethanol, and tetrahydrofuran.

9. The method for preparing the modified natural graphite negative electrode material according to claim 1, characterized in that: and the air inlet temperature of the fluidized bed in the step S3 is 60-150 ℃.

10. The method for preparing the modified natural graphite negative electrode material according to claim 1, characterized in that: the inert atmosphere in the step S4 is nitrogen, argon or helium.

Technical Field

The invention relates to the technical field of preparation of lithium ion battery cathode materials, in particular to a preparation method of a modified natural graphite cathode material.

Background

The lithium ion battery is widely applied to the fields of 3C products, power energy storage and the like, and the graphite micropowder is mainly used as a negative electrode material of the lithium ion battery at present and is a key factor influencing the performance of the lithium ion battery. The natural graphite has the characteristics of high specific capacity, good charge and discharge platform, wide source, low cost and the like, but the large-scale application of the natural graphite is limited by the defects of poor compatibility with battery electrolyte, low rate performance, poor charge and discharge cycle performance and the like. Therefore, the modification of the natural graphite to improve the electrical property and the energy storage property of the natural graphite becomes a key for the popularization and application of the natural graphite in the high-end lithium ion battery cathode material.

The Chinese patent CN108832124A discloses that the surface of natural graphite is coated with a mesoporous graphite structure after purification, the surface structure and chemical properties of natural graphite are improved, the first coulombic efficiency and cycle performance of natural graphite are improved, but the defects of natural graphite such as anisotropy and small interlayer spacing are not improved, so that the large-current charge and discharge performance of modified natural graphite is limited. CN108751187A utilizes inorganic acid to oxidize natural graphite to improve its cycle stability, but the defect and active site exposed after oxidation limit the promotion of first coulomb efficiency. CN104505491B utilizes metal ions to carry out surface amorphous carbon coating after the metal ions are subjected to layer expanding, the multiplying power performance and the cycle performance of the natural graphite are improved, but the metal ions existing in the structure gradually migrate to the surface of the negative electrode along with the charging and discharging and possibly form dendrites, and the safety of the battery is seriously influenced.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention aims to provide the preparation method of the modified natural graphite cathode material, which can effectively improve the high-rate charge-discharge performance and the first coulombic efficiency of the natural graphite cathode material, has a simple and easily-controlled process, and is easy for industrial production.

In order to solve the problems, the technical scheme adopted by the invention is as follows:

a preparation method of a modified natural graphite negative electrode material comprises the following steps:

s1, purification and oxidation layer expansion: mixing natural graphite with an oxidant, an intercalating agent and hydrofluoric acid, purifying and expanding at 0-50 ℃ for 30-120 min, separating and filtering out a solid, washing the solid to a pH value of 5-7, and drying for later use;

s2, shaping: shaping the natural graphite processed in the step S1 into spheroidal graphite powder with D50 particle size of 5-30 μm;

s3, surface coating: placing the natural graphite treated in the step S2 into a cavity of fluidized bed equipment, spraying a solution containing an organic coating agent into a fluidized bed for coating, wherein the coating reaction time is 0.5-2 h, and taking out the natural graphite for later use after cooling to room temperature;

s4, high-temperature carbonization: and (5) heating the spheroidal graphite powder obtained in the step (S3) to 600-1200 ℃ under the protection of inert atmosphere, preserving heat for 1-6 h, and taking out after cooling to room temperature to obtain the modified natural graphite.

In a preferred embodiment of the present invention, in step S1, the mass ratio of the natural graphite to the oxidizing agent, the intercalating agent, and the hydrofluoric acid is 1:0.03 to 1.5:0.1 to 15: 0.05.

In a preferred embodiment of the present invention, the natural graphite in step S1 is at least one of high-carbon graphite, high-purity graphite, and spherical graphite.

In a preferred embodiment of the present invention, the oxidizing agent in step S1 is at least one of concentrated nitric acid, concentrated sulfuric acid, and hydrogen peroxide.

As a preferred embodiment of the present invention, the intercalation agent in step S1 is at least one of concentrated nitric acid, phosphoric acid, formic acid, acetic acid and oxalic acid.

In a preferred embodiment of the present invention, the mass ratio of the organic coating agent to the spheroidal graphite powder in step S3 is 0.001 to 0.1: 1

In a preferred embodiment of the present invention, the organic coating agent-containing solution in step S3 is present in an amount of 1 to 65% by mass.

In a preferred embodiment of the present invention, the organic coating agent in step S3 is at least one of glucose, sucrose, phenolic resin, polyethylene glycol, and asphalt; the solvent used in step S3 is at least one of deionized water, methanol, ethanol, and tetrahydrofuran.

In a preferred embodiment of the present invention, the temperature of the gas supplied to the fluidized bed in step S3 is 60 to 150 ℃.

As a preferred embodiment of the present invention, the inert atmosphere in step S4 is nitrogen, argon or helium.

Compared with the prior art, the invention has the beneficial effects that:

(1) the preparation method of the invention synchronously carries out the purification process and the oxidation layer expanding process of the natural graphite, simplifies the process, increases the types of the raw materials of the natural graphite which can be processed, and enlarges the universality of the preparation process;

(2) according to the invention, the organic matter or inorganic acid radical is used for expanding the graphite sheet layer, so that the high-rate charge and discharge capacity of the graphite cathode material is improved; compared with the method of using metal ions to expand the layer, the method improves the safety of the modified natural graphite as the negative electrode, and can also use inorganic acid radical decomposition products to dope the graphite, so as to change the electron density of the graphite sheet layer, thereby improving the electrochemical performance;

(3) compared with the traditional coating process, the novel coating process of the fluidized bed can realize the uniform coating of an extremely thin coating layer, avoid the corrosion of electrolyte to graphite layers caused by nonuniform coating and improve the circulation stability;

in conclusion, the preparation method provided by the invention can effectively improve the high-rate charge-discharge performance and the first coulombic efficiency of the natural graphite cathode material, and is simple and easy to control in process, low in cost and easy for industrial production.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments.

A preparation method of a modified natural graphite negative electrode material comprises the following steps:

s1, purification and oxidation layer expansion: mixing natural graphite with an oxidant, an intercalating agent and hydrofluoric acid according to a mass ratio of 1: 0.03-1.5: 0.1-15: 0.05, purifying and expanding at 0-50 ℃ for 30-120 min, separating and filtering out a solid, washing the solid to a pH value of 5-7, and drying for later use;

s2, shaping: shaping the natural graphite processed in the step S1 into spheroidal graphite powder with D50 particle size of 5-30 μm;

s3, surface coating: placing the natural graphite treated in the step S2 into a cavity of fluidized bed equipment, spraying a solution containing an organic coating agent into a fluidized bed for coating, wherein the air inlet temperature of the fluidized bed is 60-150 ℃, the coating reaction time is 0.5-2 h, and taking out the natural graphite for later use after cooling to room temperature;

s4, high-temperature carbonization: and (5) heating the natural graphite obtained in the step (S3) to 600-1200 ℃ under the protection of inert atmosphere, preserving heat for 1-6 h, and taking out after cooling to room temperature to obtain the modified natural graphite.

In the above step, the natural graphite in step S1 is at least one of high-carbon graphite, high-purity graphite, and spherical graphite, and when the spherical graphite is used as the natural graphite, the shaping process in step S2 does not need to be performed on the natural graphite. The oxidant is at least one of concentrated nitric acid, concentrated sulfuric acid and hydrogen peroxide, and the intercalation agent is at least one of concentrated nitric acid, phosphoric acid, formic acid, acetic acid and oxalic acid.

In the step S3, the mass ratio of the organic coating agent to the spheroidal graphite powder is 0.001-0.1: 1; the mass fraction of the solution containing the organic coating agent is 1-65%. Specifically, the organic coating agent is at least one of glucose, sucrose, phenolic resin, polyethylene glycol and asphalt; the solvent is at least one of deionized water, methanol, ethanol and tetrahydrofuran.

The inert atmosphere in step S4 is nitrogen or argon or helium.