阅读说明：本技术 氮掺杂中空结构石墨微球、复合负极材料及其制备方法 (Nitrogen-doped hollow-structure graphite microsphere, composite negative electrode material and preparation method of composite negative electrode material ) 是由 黄正宏 展长振 吕瑞涛 康飞宇 于 2021-07-30 设计创作，主要内容包括：本发明提出一种氮掺杂中空结构的石墨微球负极材料和氮掺杂中空硅/氧化亚硅/石墨复合的负极材料,采用中空石墨微球,内部超细石墨片具有随机取向,不仅可以减小充放电过程中锂离子扩散受阻问题,有利于电解液渗透,促进电化学动力学过程,同时中空结构可以缓解充放电过程中石墨片的膨胀应力并为硅的体积膨胀提供所需空间。将纳米硅转化成氧化亚硅进一步缓解材料的膨胀效应。氮掺杂碳层可以提高材料的导电性,阻止电解液与活性材料的副反应,提高材料的首次库伦效率,保持材料结构稳定性。(The invention provides a graphite microsphere negative electrode material with a nitrogen-doped hollow structure and a negative electrode material compounded by nitrogen-doped hollow silicon/silicon monoxide/graphite, wherein the hollow graphite microsphere is adopted, and the internal superfine graphite flakes have random orientation, so that the problem of lithium ion diffusion resistance in the charging and discharging process can be reduced, the electrolyte permeation can be facilitated, the electrochemical dynamics process can be promoted, and meanwhile, the hollow structure can relieve the expansion stress of the graphite flakes in the charging and discharging process and provide a required space for the volume expansion of silicon. Converting the nanosilica to a siliconoxide further mitigates the swelling effect of the material. The nitrogen-doped carbon layer can improve the conductivity of the material, prevent the side reaction of the electrolyte and the active material, improve the first coulombic efficiency of the material and keep the structural stability of the material.)

1. A preparation method of a graphite microsphere negative electrode material with a nitrogen-doped hollow structure is characterized by comprising the following steps: the preparation method comprises the steps of taking superfine graphite powder as a raw material, carrying out spray drying treatment in a water-alcohol mixed solution under the assistance of a surfactant and a nitrogen-containing organic matter, and then coating and carbonizing secondary particles to obtain the catalyst.

2. The method for preparing the graphite microsphere anode material with the nitrogen-doped hollow structure as claimed in claim 1, wherein the method comprises the following steps: the mass ratio of the superfine graphite powder, the surfactant and the nitrogen-containing organic matter is 1 (0.1-2) to 0.1-3.

3. A preparation method of a nitrogen-doped hollow silicon/silicon monoxide/graphite composite cathode material is characterized by comprising the following steps: superfine graphite powder and nano silicon powder are used as raw materials, spray drying treatment is carried out in a water-alcohol mixed solution under the assistance of a surfactant, a nitrogen-containing organic matter and a high molecular organic matter, and then secondary particles are coated and carbonized to obtain the catalyst.

4. The method for preparing the nitrogen-doped hollow silicon/silicon monoxide/graphite composite anode material according to claim 3, wherein the method comprises the following steps: the mass ratio of the superfine graphite, the nano silicon powder, the surfactant, the nitrogen-containing organic matter and the high molecular compound is 1 (0.05-3) to (0.1-2) to (0.1-3) to (0.01-1).

5. The method for producing the anode material according to any one of claims 1 to 4, wherein: the volume ratio of water to ethanol in the water-alcohol mixed solution is 1 (0-0.3).

6. The method for producing the anode material according to any one of claims 1 to 4, wherein: the surfactant is one or more of polyvinylpyrrolidone, sodium dodecyl benzene sulfonate and stearic acid.

7. The method for producing the anode material according to any one of claims 1 to 4, wherein: the nitrogen-containing organic matter is one or more of chitosan, dopamine hydrochloride and melamine.

8. The method for producing the anode material according to any one of claims 1 to 4, wherein: the superfine graphite is one or more of natural superfine graphite and graphite spheroidization tailings, and the particle size of the superfine graphite is less than or equal to 5 mu m.

9. An anode material produced by the method for producing an anode material according to any one of claims 1 to 8.

10. A lithium ion battery prepared using the negative electrode material of claim 9.

Technical Field

The invention relates to the technical field of lithium ion battery materials, in particular to a graphite microsphere negative electrode material with a nitrogen-doped hollow structure, a nitrogen-doped hollow silicon/silicon monoxide/graphite composite negative electrode material and a preparation method thereof.

Background

Compared with the traditional secondary batteries such as lead-acid batteries, nickel-cadmium batteries, nickel-hydrogen batteries and the like, the lithium ion batteries have the characteristics of high energy density, long cycle life, no memory effect and the like, and are widely applied to the digital aspects such as mobile phones, notebook computers and the like. With the rapid development of the fields of electric automobiles, aerospace and the like, higher requirements are put forward on the performance of the lithium ion battery. One of the key factors determining the performance of the lithium ion battery is the negative electrode material of the lithium ion battery. Common negative electrode materials of lithium ion batteries include graphite materials, amorphous carbon materials, nanocarbon materials, silicon-based materials, lithium titanate and the like.

For the artificial graphite cathode material, the reversible capacity is about 330mAh g^-1On the left and right, the capacity attenuation is obviously intensified at high multiplying power, and the artificial graphite needs to be graphitized at the high temperature of more than 2500 ℃ in the preparation process, so that huge energy is consumed, the price fluctuation of raw materials is large, and the high multiplying power cycle performance is poor. In contrast, natural graphite negative electrode materials have good lithium intercalation/deintercalation stability and high reversible capacity (>350mAh/g) and low preparation cost, and the like, and has certain application in the lithium ion battery cathode material market. Most of the existing natural graphite cathode materials are spherical or ellipsoidal particles formed by curling and removing edges and corners of a graphite sheet through an air flow milling process, and the orientations of inner layer sheets of the particles are basically consistent. The rapid intercalation/deintercalation of lithium ions between graphite layers is seriously hindered, the volume expansion and the stripping of sheet layers of the graphite are caused, and the multiplying power and the cycling stability of the material are reduced, so that the spherical natural graphite with the structure is not suitable for the large-scale application of the negative electrode material of the power lithium ion battery.

In recent years, silicon-based negative electrode materials attract extensive attention of researchers at home and abroad, and become a new hot spot of negative electrode materials. The elementary silicon material has an ultrahigh theorySpecific capacity (about 4200mAh g^-1) Low charge and discharge platform, low reaction activity with electrolyte and rich storage in earth crust. But also has the problems of continuous fracture and reformation of SEI film, material pulverization and the like caused by serious volume expansion in the charging and discharging process. Although the theoretical capacity of the silica material is smaller than that of pure silicon, Li is generated during charge and discharge₂O and Li₄SiO₄The volume expansion effect of the material can be well inhibited by the inactive phases, but the inactive phases can consume part of lithium, so that the problem of low coulombic efficiency for the first time exists.

Therefore, the development of a brand-new lithium ion negative electrode material makes up the defects of the material, the obtained rate is high, the cycling stability is better, the volume effect is smaller, the expansion effect is low, and the first coulombic efficiency of the material is improved, so that the problem to be solved is urgent.

Disclosure of Invention

The invention aims to provide a high-rate long-cycle power lithium ion negative electrode material and a preparation method thereof. According to the hollow graphite microsphere obtained by the method, the graphite flakes in the hollow graphite microsphere have random orientation, so that the problem of lithium ion diffusion resistance in the charging and discharging process can be reduced, the electrolyte permeation is facilitated, the electrochemical dynamics process is promoted, and meanwhile, the expansion stress of the graphite flakes in the charging and discharging process can be relieved by the hollow structure, and a required space is provided for the volume expansion of silicon. Converting the nanosilica to a siliconoxide further mitigates the swelling effect of the material. The nitrogen-doped carbon layer can improve the conductivity of the material, prevent the side reaction of the electrolyte and the active material, improve the first coulombic efficiency of the material and keep the structural stability of the material.

In order to solve the technical problems, the invention provides a preparation method of a graphite microsphere negative electrode material with a nitrogen-doped hollow structure, which is obtained by taking superfine graphite powder as a raw material, carrying out spray drying treatment in a water-alcohol mixed solution under the assistance of a surfactant and a nitrogen-containing organic matter, and then coating and carbonizing secondary particles.

Wherein the mass ratio of the superfine graphite powder, the surfactant and the nitrogen-containing organic matter is 1 (0.1-2) to 0.1-3.

The invention also provides a preparation method of the nitrogen-doped hollow silicon/silicon monoxide/graphite composite cathode material, which is obtained by taking superfine graphite powder and nano silicon powder as raw materials, carrying out spray drying treatment in a water-alcohol mixed solution under the assistance of a surfactant, a nitrogen-containing organic matter and a high-molecular organic matter, and then coating and carbonizing secondary particles.

Wherein the mass ratio of the superfine graphite, the nano silicon powder, the surfactant, the nitrogen-containing organic matter and the high molecular compound is 1 (0.05-3) to (0.1-2) to (0.1-3) to (0.01-1).

Wherein the volume ratio of water to ethanol in the water-alcohol mixed solution is 1 (0-0.3).

Wherein the surfactant is one or more of polyvinylpyrrolidone, sodium dodecyl benzene sulfonate and stearic acid.

The nitrogen-containing organic matter is one or more of chitosan, dopamine hydrochloride and melamine.

Wherein the superfine graphite is one or more of natural superfine graphite and graphite spheroidization tailings, and the particle size is less than or equal to 5 mu m.

The invention also provides the cathode material prepared by the preparation method.

The invention also provides a lithium ion battery prepared by adopting the cathode material.

The invention has the advantages of

The preparation method is simple in preparation process and low in cost, the prepared material is suitable for large-scale production, and meanwhile, the method can be applied in industrialization. The obtained nitrogen-doped hollow graphite microspheres and the silicon/silicon monoxide/graphite composite material used for the lithium ion battery cathode material show good electrochemical performance, compared with commercial graphite, the multiplying power performance of the obtained cathode material is obviously improved, and the obtained cathode material has more excellent cycling stability under the condition of high current density.

Drawings

FIG. 1 is a scanning electron micrograph of a nitrogen-doped hollow graphite microsphere prepared according to the present invention.

FIG. 2 shows that the sample 3 of the present invention has a g value of 100mAh^-1Electrochemical performance curve at current density.

Detailed Description

The invention provides a preparation method of a graphite microsphere negative electrode material with a nitrogen-doped hollow structure, which comprises the following steps:

firstly, dissolving a surfactant and a nitrogenous organic matter in a dispersion medium to obtain a solution;

secondly, dispersing the superfine graphite powder in the solution prepared in the first step, uniformly stirring, and performing ultrasonic treatment to obtain uniform slurry;

thirdly, spray drying and granulating to obtain a powder material;

step four, optionally, fully mixing the powder material obtained in the step three with a coating material;

fifthly, carbonizing treatment;

and sixthly, cooling to obtain the product.

The dispersion medium in the first step is water and ethanol, and the volume ratio of the water to the absolute ethanol is 1 (0-0.3).

The surfactant is one or more of polyvinylpyrrolidone, sodium dodecyl benzene sulfonate and stearic acid.

The mass ratio of the superfine graphite powder to the surfactant is 1 (0.1-2).

The nitrogen-containing organic matter is one or more of chitosan, dopamine hydrochloride and melamine.

The mass ratio of the superfine graphite powder to the nitrogen-containing organic matter is 1 (0.1-3).

The superfine graphite powder is one or a mixture of natural superfine graphite and graphite spheroidization tailings, and the particle size of the superfine graphite powder is less than or equal to 5 mu m.

And in the fourth step, the coating material is one or a mixture of citric acid, polyvinyl nitrile and asphalt.

The coating material accounts for 1-30% of the mass of the powder material after spray drying.

In the fifth step, the carbonization temperature in the carbonization process is firstly at the temperature of 100 ℃ and 400 ℃ for heat treatment for 1 to 3 hours, and then the carbonization is carried out at the temperature of 600 ℃ and 1100 ℃ for 2 to 5 hours.

The invention also provides a preparation method of the nitrogen-doped hollow silicon/silicon monoxide/graphite composite negative electrode material, which comprises the following steps:

firstly, dissolving a surfactant, a nitrogenous organic matter and a macromolecular compound in a dispersion medium to obtain a solution;

secondly, dispersing the superfine graphite powder and the nano silicon powder in the solution prepared in the first step, uniformly stirring, and performing ultrasonic treatment to obtain uniform slurry;

thirdly, spray drying and granulating to obtain a powder material;

fourthly, fully mixing the powder material obtained in the third step with a coating material;

fifthly, carbonizing treatment;

and sixthly, cooling to obtain the product.

The dispersion medium in the first step is water and ethanol, and the volume ratio of the water to the absolute ethanol is 1 (0-0.3).

The surfactant is one or more of polyvinylpyrrolidone, sodium dodecyl benzene sulfonate and stearic acid.

The mass ratio of the superfine graphite powder to the surfactant is 1 (0.1-2).

The nitrogen-containing organic matter is one or more of chitosan, dopamine hydrochloride and melamine.

The mass ratio of the superfine graphite powder to the nitrogen-containing organic matter is 1 (0.1-3).

The high molecular compound is one or more of polyvinyl alcohol, sodium alginate, sodium carboxymethylcellulose and phenolic resin.

The mass ratio of the superfine graphite powder to the high molecular compound is 1 (0.01-1).

The superfine graphite powder is one or a mixture of natural superfine graphite and graphite spheroidization tailings, and the particle size of the superfine graphite powder is less than or equal to 5 mu m.

The mass ratio of the superfine graphite powder to the nano silicon powder is 1 (0.05-3).

And in the fourth step, the coating material is one or a mixture of citric acid, polyvinyl nitrile and asphalt.

The coating material accounts for 1-30% of the mass of the powder material after spray drying.

In the fifth step, the carbonization temperature in the carbonization process is firstly at the temperature of 100 ℃ and 400 ℃ for heat treatment for 1 to 3 hours, and then the carbonization is carried out at the temperature of 600 ℃ and 1100 ℃ for 2 to 5 hours.

The following embodiments are described in detail to solve the technical problems by applying technical means to the present invention, and the implementation process of achieving the technical effects can be fully understood and implemented.

Comparative example 1

Uniformly mixing superfine graphite powder, conductive carbon black, CMC and SBR in deionized water according to a mass ratio of 8:1:0.5:0.5 to prepare slurry, coating the slurry on a copper foil, drying, rolling a film and punching to obtain a lithium ion battery negative electrode sheet, forming a lithium ion half battery with the lithium electrode sheet, and preparing the lithium ion half battery with LiPF₆The 2032 type button cell is assembled by organic electrolyte and is subjected to constant current charge and discharge test. At 100mA g^-1The first discharge capacity of the lithium secondary battery is 420mAh g under the current density^-1The charge capacity was 297mAh g^-1。

Example 1

Dissolving a surfactant PVP accounting for 0.5 percent of the mass of the superfine graphite and melamine accounting for 2 percent of the mass of the superfine graphite in a mixed solution with the ratio of water to absolute ethyl alcohol being 4:1, dispersing 2g of superfine graphite powder in the solution, stirring and carrying out ultrasonic treatment for 10-120min, atomizing, drying and granulating the obtained uniform slurry on a spray dryer to obtain a powder material, placing the powder material in a tubular furnace for carbonization under the atmosphere of argon, wherein the treatment temperature is 100-400 ℃, the heat treatment is carried out for 1-3 hours, and the carbonization is carried out for 2-5 hours at the high temperature of 600-1000 ℃. Uniformly mixing the obtained nitrogen-doped hollow graphite nodule negative electrode material (figure 1) with conductive carbon black, CMC and SBR in deionized water according to the mass ratio of 8:1:0.5:0.5 to prepare slurry, coating and mixingDrying, rolling and punching on copper foil to obtain negative plate of lithium ion battery, forming lithium ion half battery with lithium plate, and using LiPF₆The 2032 type button cell is assembled by organic electrolyte and is subjected to constant current charge and discharge test. At 100mA g^-1The first discharge capacity of the lithium secondary battery is 454mAh g^-1The charging capacity is 334mAh g^-1。

Example 2

Dissolving a surfactant PVP accounting for 0.5 percent of the mass of the superfine graphite and melamine accounting for 15 percent of the mass of the superfine graphite in a mixed solution of water and ethanol, wherein the ratio of the water to the absolute ethanol is 4:1, dispersing the superfine graphite powder in the solution, stirring and carrying out ultrasonic treatment for 10-120min, atomizing, drying and granulating the obtained uniform slurry on a spray dryer to obtain a powder material, fully mixing the powder material and asphalt, then putting the powder material in a tubular furnace for carbonization under the atmosphere of argon, wherein the treatment temperature is 100 DEG, the treatment temperature is 400 ℃, the heat treatment is 1-3 hours, and the carbonization is carried out at the high temperature of 600 DEG for 1000 ℃ for 2-5 hours. Uniformly mixing the obtained nitrogen-doped hollow graphite nodule negative electrode material with conductive carbon black, CMC and SBR in deionized water according to the mass ratio of 8:1:0.5:0.5 to prepare slurry, coating the slurry on a copper foil, drying, rolling a film and punching to obtain a lithium ion battery negative electrode sheet, forming a lithium ion half battery with the lithium sheet, and preparing the lithium ion half battery by using LiPF₆The 2032 type button cell is assembled by organic electrolyte and is subjected to constant current charge and discharge test. At 100mA g^-1Current density of (A) in example 2, the first discharge capacity was 433mAh g^-1The charging capacity is 341mAh g^-1Both capacity and first coulombic efficiency were improved compared to comparative example 1. In 1Ag^-1Under the current density, the specific capacity of the obtained nitrogen-doped hollow graphite cathode material is 266mAh g^-1The specific capacity is much higher than 204mAh g of the superfine graphite electrode^-1And the high-power-factor performance is shown.

Example 3

Dissolving surfactant PVP (polyvinyl pyrrolidone) 0.5 wt% of superfine graphite, sodium alginate 0.05 wt% of superfine graphite and melamine 15 wt% of superfine graphite in water solution, and mixing superfine graphite 2g and graphite 20 wt%Dispersing the nano silicon powder in the solution, stirring and carrying out ultrasonic treatment for 10-120min, atomizing, drying and granulating the obtained uniform slurry on a spray dryer to obtain a powder material, fully mixing the powder material with asphalt, and then putting the powder material in a tubular furnace for carbonization under argon atmosphere, wherein the treatment temperature is 100-400 ℃, the heat treatment is 1-3 hours, and the carbonization is carried out at the high temperature of 600-1000 ℃ for 2-5 hours. Uniformly mixing the obtained nitrogen-doped hollow silicon/silicon monoxide/graphite negative electrode material with conductive carbon black, CMC and SBR in deionized water according to the mass ratio of 8:1:0.5:0.5 to prepare slurry, coating the slurry on a copper foil, drying, rolling a film and punching to obtain a lithium ion battery negative electrode sheet, forming a lithium ion half battery with the lithium sheet, and using LiPF₆The 2032 type button cell is assembled by organic electrolyte and is subjected to constant current charge and discharge test. As shown in FIG. 2, at 100mA g^-1The first discharge capacity of the lithium secondary battery is 797.5mAh g^-1The charging capacity is 644.1mAh g^-1The first coulombic efficiency was 81%.

It can be seen from the examples and comparative examples that, by using the graphite microsphere negative electrode material with a nitrogen-doped hollow structure and the hollow silicon/silicon monoxide/graphite composite negative electrode material, the internal graphite flakes have random orientations, which not only can reduce the problem of lithium ion diffusion resistance in the charging and discharging process, facilitate electrolyte permeation and promote the electrochemical dynamic process, but also the hollow structure can relieve the expansion stress of the graphite flakes in the charging and discharging process and provide a required space for the volume expansion of silicon. The nano silicon is converted into the silicon monoxide, so that the expansion effect of the material is further relieved, and the electrochemical performance of the material is improved.

All of the above mentioned intellectual property rights are not intended to be restrictive to other forms of implementing the new and/or new products. Those skilled in the art will take advantage of this important information, and the foregoing will be modified to achieve similar performance. However, all modifications or alterations are based on the new products of the invention and belong to the reserved rights.

The foregoing is directed to preferred embodiments of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow. However, any simple modification, equivalent change and modification of the above embodiments according to the technical essence of the present invention are within the protection scope of the technical solution of the present invention.