WO2023142675A1

WO2023142675A1 - Preparation method for silicon-carbon negative electrode material and use thereof

Info

Publication number: WO2023142675A1
Application number: PCT/CN2022/135816
Authority: WO
Inventors: 余海军; 谢英豪; 李爱霞; 张学梅; 李长东
Original assignee: 广东邦普循环科技有限公司; 湖南邦普循环科技有限公司; 湖南邦普汽车循环有限公司
Priority date: 2022-01-28
Filing date: 2022-12-01
Publication date: 2023-08-03
Also published as: CN114551851A

Abstract

Disclosed in the present application are a preparation method for a silicon-carbon negative electrode material and the use thereof. The preparation method comprises: adding a metal salt solution into a sodium silicate solution for a reaction to obtain a silicate precipitate; calcining the silicate precipitate; placing the calcined material in a concentrated acid for heat soaking; and adding the resulting wet material into a graphene dispersion liquid, drying same by means of distillation, and heating the resulting dry material to obtain the silicon-carbon negative electrode material. In the present application, after metal ions are removed from the silicate, the resulting silicon dioxide has more atomic vacancies, such that the problem of the degradation of the cycling performance caused by volume expansion can be effectively relieved; and when the silicon dioxide is sintered with graphene, the silicon dioxide is deprived of oxygen atoms, and monatomic silicon having a higher specific capacity is formed, such that the specific capacity and cycling performance of the material are improved.

Description

Preparation method and application of silicon carbon negative electrode material

technical field

The application belongs to the technical field of lithium battery negative electrode materials, and in particular relates to a preparation method and application of a silicon carbon negative electrode material.

Background technique

Due to the advantages of high specific capacity, high charge-discharge efficiency, good cycle performance and low cost, lithium-ion batteries have gradually become a research hotspot. The rapid development of electronic products and new energy vehicle technology has put forward higher requirements for lithium-ion batteries. As an important part of lithium-ion batteries, anode materials affect the specific energy and cycle life requirements of batteries, and have always been the focus of lithium-ion battery research. With the development of lithium-ion battery technology, the development requirements of high capacity and small volume are becoming more and more obvious. Therefore, it is imminent to develop new high capacity anode materials.

In the research and application of lithium-ion battery anode materials, silicon-based anode materials have higher lithium storage capacity and lower voltage platform, and are one of the hotspots in the research of lithium-ion battery anode materials. The theoretical specific capacity of silicon-based materials is the highest. The alloy formed by it is Li _x Si, and the range of x is 0-4.4. The theoretical specific capacity of pure silicon is 4200mAh/g, while the theoretical capacity of natural graphite, a commercial negative electrode material, is only 372mAh/g. g, and silicon has no solvation, its raw material reserves are abundant, and it has higher stability than other metal materials. It is considered to be the most anticipated high-capacity lithium-ion battery anode material.

However, due to the severe volume expansion and contraction of the silicon negative electrode during the lithium insertion and removal cycle, the material structure is destroyed and pulverized, which leads to the de-powdering of the electrode sheet, and the electrical contact between the electrode active material and the current collector is lost. Seriously affect the cycle performance of the battery. On the other hand, silicon itself is a semiconductor material with very low electrical conductivity. These problems hinder the large-scale application of silicon-based anode materials in lithium-ion batteries.

In order to solve the problem that silicon anode materials are prone to stress cracking during charge and discharge, resulting in volume expansion and resulting in degradation of cycle performance, the following improvement methods are currently available: reducing the particle size of active silicon particles and preparing nano-scale materials to reduce the internal volume change. Stress; the use of nano-silicon materials and composites of other materials, such as silicon-carbon composites, to relieve the volume expansion of silicon, thereby improving its cycle life. The related technology provides a composite material of carbon nanofiber and silicon material, and when used as negative electrode material of lithium ion battery, the capacity and cycle performance are all improved. Some scholars also use the hot gas deposition method to coat a layer of carbon material on the surface of simple silicon, with a specific capacity of more than 600mAh/g, and the cycle performance is equivalent to that of carbon materials, which is significantly improved compared with that of simple silicon. However, compared with the theoretical capacity of silicon materials, the capacity and cycle performance of silicon-based negative electrodes for lithium-ion battery negative electrodes still need to be improved.

Contents of the invention

The following is an overview of the topics described in detail in this article. This summary is not intended to limit the scope of the claims.

Application This application proposes a method for preparing a silicon-carbon negative electrode material and its application.

According to one aspect of the present application, a method for preparing a silicon-carbon negative electrode material is proposed, comprising the following steps:

S1: adding the metal salt solution to the sodium silicate solution for reaction, aging after the reaction, and separating the solid and liquid to obtain the silicate precipitate;

S2: Calcining the silicate precipitate to obtain a calcined material;

S3: placing the calcined material in concentrated acid for hot soaking, then separating solid from liquid and washing with water to obtain a wet material;

S4: adding the wet material into the graphene dispersion, evaporating to dryness, and heating the obtained dry material under an inert atmosphere to obtain the silicon-carbon negative electrode material.

In some embodiments of the present application, in step S1, the metal salt solution is at least one of soluble magnesium salt, aluminum salt, nickel salt or manganese salt solutions.

In some embodiments of the present application, in step S1, the metal salt solution is added to the sodium silicate solution at a rate of 5-20 mL/min.

In some embodiments of the present application, in step S1, the concentration of the metal salt solution is 0.5-2.5 mol/L.

In some embodiments of the present application, in step S1, the concentration of the sodium silicate solution is 0.1-1.0 mol/L calculated as SiO ₂ .

In some embodiments of the present application, in step S1, the amount of sodium silicate is 1.05-1.1 times of the theoretical amount.

In some embodiments of the present application, in step S1, the temperature of the reaction is 70-95°C.

In some embodiments of the present application, in step S1, the aging time is 1-2 hours.

In some embodiments of the present application, in step S2, the calcination temperature is 700-1200°C. Further, the calcination time is 1-2h.

In some embodiments of the present application, in step S3, the concentration of the concentrated acid is 4-12mol/L; the temperature of the heat soaking is 60-120°C. Further, the time of the heat soaking is 10-120min.

In some embodiments of the present application, in step S3, the liquid-solid ratio of the concentrated acid to the calcined material is 1-3 mL/g.

In some embodiments of the present application, in step S3, the concentrated acid is at least one of sulfuric acid, hydrochloric acid or nitric acid.

In some embodiments of the present application, in step S4, the graphene dispersion is prepared by ultrasonically dispersing graphene in an organic solvent, and the mass ratio of silicon dioxide and graphene in the wet material is (0.05- 0.2):1.

In some preferred embodiments of the present application, in step S4, the organic solvent is at least one of methanol, ethanol, acetone, tetrahydrofuran, NMP, DMF, dimethyl carbonate, diethyl carbonate or ethyl methyl carbonate kind.

In some preferred embodiments of the present application, in step S4, the concentration of the graphene dispersion is 0.5-3.0 g/L.

In some embodiments of the present application, in step S4, the heating process is: first heating to 350-450° C. for 1-2 hours, and then heating to 800-1300° C. for 5-12 hours.

The application also provides the application of the preparation method in the preparation of lithium ion batteries.

According to a preferred embodiment of the present application, it has at least the following beneficial effects:

1. In this application, firstly, a silicate precipitate is formed by reacting a metal salt with sodium silicate, and the precipitate is calcined at a high temperature to crystallize the silicate, and then soaked in concentrated acid to remove metal ions to obtain a more Silicon dioxide with polyatomic vacancies, the silicon dioxide is mixed with graphene, and under the condition of cutting off oxygen, graphene takes oxygen atoms from silicon dioxide to further form oxygen-containing functional groups, while silicon dioxide is reduced to Si simple substance, so as to obtain a silicon-carbon composite negative electrode material.

2. Since the silicon dioxide produced by silicate has more atomic vacancies after removing metal ions, it can effectively alleviate the problem of cycle performance degradation caused by volume expansion when used as an anode material, and when sintered with graphene At this time, silicon dioxide is taken away by oxygen atoms to form elemental silicon with higher specific capacity, thereby improving the specific capacity and cycle performance of the material.

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

Description of drawings

The accompanying drawings are used to provide a further understanding of the technical solutions herein, and constitute a part of the description, and are used together with the embodiments of the application to explain the technical solutions herein, and do not constitute limitations to the technical solutions herein. Below in conjunction with accompanying drawing and embodiment the present application is described further, wherein:

FIG. 1 is an SEM image of the silicon-carbon negative electrode material prepared in Example 1 of the present application.

Detailed ways

The idea and technical effects of the present application will be clearly and completely described below in conjunction with the embodiments, so as to fully understand the purpose, features and effects of the present application. Apparently, the described embodiments are only some of the embodiments of the present application, not all of them. Based on the embodiments of the present application, other embodiments obtained by those skilled in the art without creative efforts belong to The protection scope of this application.

Example 1

In this embodiment, a silicon carbon negative electrode material is prepared, and the specific process is as follows:

Step 1, preparation metal ion concentration is the magnesium chloride solution A of 1.0mol/L;

Step 2, preparation concentration (in terms of _SiO ) is the sodium silicate solution B of 1.0mol/L;

Step 3, adding the magnesium chloride solution A prepared in step 1 to the sodium silicate solution B prepared in step 2 at a rate of 10 mL/min for reaction, the reaction temperature is controlled at 70°C, and the amount of sodium silicate is 1.05 times the theoretical amount ;

Step 4, after the reaction is finished, continue to age for 2 hours;

Step 5, the material is subjected to solid-liquid separation to obtain a solid material;

Step 6, calcining the solid material at a temperature of 1200° C. for 2 hours to obtain a calcined material;

Step 7, according to the liquid-solid ratio of 1mL/g, soak the calcined material in sulfuric acid with a concentration of 12mol/L for 60min, and the soaking temperature is 120°C;

Step 8, the material is subjected to solid-liquid separation, and then washed with pure water to obtain a wet material;

Step 9, taking graphene according to the mass ratio of silica and graphene in the wet material is 5%, and ultrasonically dispersing in ethanol to obtain a graphene dispersion with a graphene concentration of 3.0g/L;

Step 10, adding the wet material to the graphene dispersion, stirring evenly, and evaporating to dryness to obtain a powder material;

Step 11, heating the powder material to 450° C. for 2 hours under an inert gas, and then heating to 800° C. for 5 hours to obtain a silicon-carbon negative electrode material.

Example 2

Step 1, the preparation metal ion concentration is the aluminum sulfate solution A of 2.0mol/L;

Step 2, preparation concentration (in terms of _SiO ) is the sodium silicate solution B of 0.5mol/L;

Step 3, add the aluminum sulfate solution A prepared in step 1 to the sodium silicate solution B prepared in step 2 at a rate of 20mL/min for reaction, control the reaction temperature to 85°C, and the amount of sodium silicate to be 1.05 of the theoretical amount times;

Step 4, after the reaction is over, continue aging for 1 hour;

Step 6, calcining the solid material at a temperature of 1100° C. for 2 hours to obtain a calcined material;

Step 7, according to the liquid-solid ratio of 2mL/g, soak the calcined material in hydrochloric acid with a concentration of 8mol/L for 120min, and the soaking temperature is 60°C;

Step 9, weighing graphene according to the mass ratio of silicon dioxide and graphene in the wet material to 10%, and ultrasonically dispersing in acetone to obtain a graphene dispersion with a graphene concentration of 0.5g/L;

Step 11, heating the powder material to 350° C. for 2 hours under an inert gas, and then heating to 1000° C. for 8 hours to obtain a silicon-carbon negative electrode material.

Example 3

Step 1, preparation metal ion concentration is the nickel sulfate solution A of 2.5mol/L;

Step 2, preparation concentration (calculated as _SiO ) is the sodium silicate solution B of 0.1mol/L;

Step 3, add the metal salt solution A prepared in step 1 to the sodium silicate solution B prepared in step 2 at a rate of 5mL/min for reaction, control the reaction temperature at 95°C, and use 1.1% of the theoretical amount of sodium silicate times;

Step 4, after the reaction is finished, continue to age for 2 hours;

Step 6, calcining the solid material at a temperature of 700° C. for 2 hours to obtain a calcined material;

Step 7, according to the liquid-solid ratio of 3mL/g, soak the calcined material in nitric acid with a concentration of 4mol/L for 120min, and the soaking temperature is 70°C;

Step 9, weighing graphene according to the mass ratio of silicon dioxide and graphene in the wet material to 20%, and ultrasonically dispersing in tetrahydrofuran to obtain a graphene dispersion with a graphene concentration of 1.0 g/L;

In step 11, the powder material is heated to 400° C. for 2 hours under an inert gas, and then heated to 1200° C. for 12 hours to obtain a silicon-carbon negative electrode material.

Comparative example 1

This comparative example prepares a kind of silicon carbon negative electrode material, and the difference with embodiment 1 is that the wet material is replaced with commercially available nano-scale silicon dioxide powder (analytically pure, 5-20nm), and the specific process is:

Step 1, according to the mass ratio of silicon dioxide powder and graphene is 5% to take graphene, and ultrasonic dispersion in ethanol, obtains the graphene dispersion liquid that graphene concentration is 3.0g/L;

Step 2, adding silicon dioxide powder to the graphene dispersion, stirring evenly, and evaporating to dryness to obtain a powder;

Step 3, heating the powder material to 450° C. for 2 hours under an inert gas, and then heating to 800° C. for 5 hours to obtain a silicon-carbon negative electrode material.

Comparative example 2

In this comparative example, a silicon-carbon negative electrode material was prepared. The difference from Example 2 is that the wet material is replaced with commercially available silicon dioxide powder (analytical pure), and the specific process is as follows:

Step 1, according to the mass ratio of silicon dioxide powder and graphene is 10%, graphene is weighed, and ultrasonically dispersed in acetone to obtain a graphene dispersion with a graphene concentration of 0.5g/L;

Step 3, heating the powder material to 350° C. for 2 hours under an inert gas, and then heating to 1000° C. for 8 hours to obtain a silicon-carbon negative electrode material.

Comparative example 3

In this comparative example, a silicon-carbon negative electrode material was prepared. The difference from Example 3 is that the wet material is replaced with commercially available silicon dioxide powder (analytical pure), and the specific process is as follows:

Step 1, according to the mass ratio of silicon dioxide powder and graphene is 20%, graphene is weighed, and ultrasonically dispersed in tetrahydrofuran to obtain a graphene dispersion with a graphene concentration of 1.0g/L;

In step 3, the powder material is heated to 400° C. for 2 hours under an inert gas, and then heated to 1200° C. for 12 hours to obtain a silicon-carbon negative electrode material.

Test case

The silicon-carbon negative electrode material obtained in Examples 1-3 and Comparative Examples 1-3 was stirred evenly with a conductive agent (SP) and a binder (CMC/SBR) to prepare an electrode slurry, and the slurry was evenly coated on a thickness of On a 9 μm copper foil current collector, dry it under vacuum at 105°C for 12 hours, and cut it to obtain the negative electrode sheet. A 2032-type coin cell was assembled in a glove box filled with high-purity argon. The charge and discharge performance test is carried out on the button battery, the charge and discharge cut-off voltage range is 5mV-1.5V, and the test temperature is 25°C. The test results are shown in Table 1.

Table 1

It can be seen from Table 1 that the specific capacity and cycle performance of the comparative examples are lower than those of the examples. This is because the silicon dioxide produced by the examples has more atomic vacancies after the silicate precipitates are soaked in concentrated acid to remove metal ions. , when used as a negative electrode material, it can effectively alleviate the problem of cycle performance degradation caused by volume expansion, and at the same time, more atomic vacancies can accommodate more lithium, and the specific capacity is improved.

The embodiments of the present application have been described in detail above in conjunction with the accompanying drawings, but the present application is not limited to the above-mentioned embodiments, and within the scope of knowledge of those of ordinary skill in the art, various modifications can be made without departing from the purpose of the present application. Variety. In addition, the embodiments of the present application and the features in the embodiments can be combined with each other under the condition of no conflict.

Claims

A method for preparing a silicon-carbon negative electrode material, comprising the following steps:

S1: adding the metal salt solution to the sodium silicate solution for reaction, aging after the reaction, and separating the solid and liquid to obtain the silicate precipitate;

S2: Calcining the silicate precipitate to obtain a calcined material;

S3: placing the calcined material in concentrated acid for hot soaking, then separating solid from liquid and washing with water to obtain a wet material;

S4: adding the wet material into the graphene dispersion, evaporating to dryness, and heating the obtained dry material under an inert atmosphere to obtain the silicon-carbon negative electrode material.
The preparation method according to claim 1, wherein, in step S1, the metal salt solution is at least one of soluble magnesium salt, aluminum salt, nickel salt or manganese salt solutions.
The preparation method according to claim 1, wherein, in step S1, the concentration of the metal salt solution is 0.5-2.5mol/L.
The preparation method according to claim 1, wherein, in step S1, in terms of SiO 2 , the concentration of the sodium silicate solution is 0.1-1.0mol/L.
The preparation method according to claim 1, wherein, in step S1, the temperature of the reaction is 70-95°C.
The preparation method according to claim 1, wherein, in step S2, the temperature of the calcination is 700-1200°C.
The preparation method according to claim 1, wherein, in step S3, the concentration of the concentrated acid is 4-12mol/L; the temperature of the hot soaking is 60-120°C.
The preparation method according to claim 1, wherein, in step S3, the liquid-solid ratio of the concentrated acid to the calcined material is 1-3mL/g.
The preparation method according to claim 1, wherein, in step S4, the graphene dispersion is obtained by ultrasonically dispersing graphene in an organic solvent, and the mass ratio of silicon dioxide and graphene in the wet material is (0.05-0.2):1.
preparation method according to claim 1, wherein, in step S4, the concentration of described graphene dispersion liquid is 0.5-3.0g/L.
The preparation method according to claim 1, wherein, in step S4, the heating process is: first heating to 350-450° C. for 1-2 hours, and then heating to 800-1300° C. for 5-12 hours.
Application of the preparation method described in any one of claims 1-9 in the preparation of lithium ion batteries.