A C-SiO for lithium-ion batteries x -Si composite negative electrode material preparation method

Abstract

The present invention discloses a C-SiO2 composite for lithium-ion batteries. x A method for preparing a C-Si composite negative electrode material, the method comprising the following steps: S1: preparation of a C@SiO2 composite material; S2: preparation of a C@Si3N4 composite material; S3: preparation of a C-SiO x Preparation of C-Si composite materials. The method of the present invention is used to prepare C-SiO for lithium ion batteries. x -Si composite negative electrode material, which integrates nano-silicon-based particles, porous structure and uniform carbon coating layer, and has a higher content of silicon active material, higher discharge specific capacity, and SiO x The carbon coating layer is coated on the surface of the Si particles, and the nano-silicon-based particles are dispersed in the carbon coating layer, which has better cycle stability; the preparation process is simple, the production cost is low, and it is easy to industrialize.

Description

Technical Field

[0001] The present invention relates to a C-SiO2 composite material for lithium ion batteries. x The invention relates to a preparation method of a -Si composite negative electrode material, and belongs to the technical field of lithium ion batteries. Background Art

[0002] The rapid development of electric vehicles and personal mobility products has placed higher demands on the energy density of lithium-ion batteries. As the core material of lithium-ion batteries, anode materials play an important role in improving the energy density of batteries.

[0003] Currently, the most widely used negative electrode material is graphite negative electrode material, but the theoretical specific capacity of graphite is only 372mAh / g, which is far from meeting the demand for negative electrode materials for high specific energy batteries. The theoretical specific capacity of silicon negative electrode is about 4000mAh / g, and SiO x The theoretical specific capacity is close to 2400mAh / g, which is much higher than that of graphite-based negative electrode materials, so it has good potential as a negative electrode material.

[0004] However, silicon-based negative electrode materials face large volume deformation during the charging and discharging process, which causes the electrode material to pulverize and leads to rapid capacity decay; at the same time, silicon-based negative electrode materials also face the problems of low electrical conductivity and poor rate performance.

[0005] Currently, silicon-based anode materials are often combined with graphite to improve the cycling stability of silicon-carbon composites. However, the discharge capacity ratio of commercially available silicon-carbon composites is low and needs to be further improved. Therefore, optimizing the combination of silicon-based anode materials and graphite materials is an urgent problem to be solved. Summary of the Invention

[0006] The purpose of the present invention is to overcome the problems of low conductivity and poor cycle stability of silicon-based negative electrode materials and provide a C-SiO2-based negative electrode for lithium-ion batteries. x -Si composite negative electrode material preparation method.

[0007] The concept of the present invention is to improve the conductivity and cycle stability of silicon-based negative electrode materials by constructing a silicon-carbon composite structure that integrates nano-silicon-based particles, a porous structure and a uniform carbon coating layer.

[0008] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0009] A C-SiO for lithium-ion batteries x -Si composite negative electrode material preparation method, the specific steps are as follows:

[0010] Step 1, preparation of C@SiO2 composite material:

[0011] The SiO2-containing raw material and the carbon-containing raw material are mixed in a molar ratio of 1:3 to 6 and uniformly mixed with deionized water to form a slurry, and the slurry is taken out and dried to obtain a C@SiO2 composite material;

[0012] Step 2: Preparation of C@Si3N4 composite material:

[0013] The prepared C@SiO2 composite material was placed in an atmosphere furnace, gas was introduced at a flow rate of 1000-3000 ml / min, and heat treated at a temperature of 1200-1700°C for 5-10 hours. After natural cooling, a C@Si3N4 composite material was obtained.

[0014] The introduced gas is one of nitrogen, nitrogen-methane mixed gas, nitrogen-ethylene mixed gas, nitrogen-acetylene mixed gas or nitrogen-hydrogen mixed gas;

[0015] Step 3, C-SiO x -Preparation of Si composite materials:

[0016] The prepared C@Si3N4 composite material was placed in a vacuum furnace and water vapor or CO2 gas was introduced. -2 Heat treatment at 800-1400℃ for 1-10h under vacuum of 1000Pa to oxidize and decompose Si3N4 to form SiO x phase and dispersed Si particles, namely C-SiO for lithium-ion batteries x -Si composite negative electrode material.

[0017] Preferably, the SiO2-containing raw material is any one or a mixture of two or more of nano-SiO2, silica, quartz, silicon powder, silica sol, silicic acid, methyl silicate, ethyl silicate, propyl silicate and butyl silicate, with a particle size of 10 to 100 nm;

[0018] Preferably, the carbon-containing raw material is any one or a mixture of two or more of sucrose, glucose, resin, citric acid, carbon fiber, acetylene black, carbon black, carbon nanotubes and graphene;

[0019] Preferably, in step 1, the mixing step specifically includes: placing the mixture into a mixer, adding deionized water, and processing at a speed of 200 to 500 r / min for 1 to 10 hours,

[0020] Furthermore, in the step 1, the drying step specifically includes: taking out the slurry and drying it at 80-150° C. for 5-10 hours.

[0021] Preferably, the C-SiO x SiO-Si composite materials x In this phase, 0<x<2.

[0022] Preferably, the C-SiO x -Si composite negative electrode material has a hollow structure, with nanoporous Si particles 1 dispersed inside, SiO x 2 attached to the surface of Si particle 1, C3 evenly coated on SiO x - The outer surface of the Si composite particle 1.

[0023] Beneficial effects of the present invention: C-SiO2 for lithium-ion batteries prepared by this method x -Si composite negative electrode material, has the following advantages:

[0024] (1) Preparation of C-SiO x -Si composite negative electrode material, which integrates nano-silicon-based particles, porous structure and uniform carbon coating layer, and has a higher content of silicon active material and higher discharge specific capacity;

[0025] (2) Prepared C-SiOx-Si composite negative electrode material, SiO x The carbon coating layer is coated on the surface of Si particles, and the nano-silicon-based particles are dispersed in the carbon coating layer, which has better cycle stability;

[0026] (3) Prepared C-SiO x -Si composite negative electrode material, simple process flow, low production cost, and easy industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 C-SiO x -Schematic diagram of the structure of Si composite negative electrode material

[0028] Reference numeral 1 represents nano-Si particles, reference numeral 2 represents SiOx layer, and reference numeral 3 represents surface C coating layer.

[0029] Figure 2 C-SiO x -Si composite negative electrode material constant current charge and discharge cycle curve at 0.1A / g current density

[0030] The horizontal axis is the number of cycles; the vertical axis is the discharge capacity, unit mAh / g DETAILED DESCRIPTION

[0031] The present invention will be further described below with reference to the accompanying drawings and examples.

[0032] Example 1

[0033] The steps of preparing the all-solid-state battery cell for lithium-ion batteries are as follows:

[0034] C-SiO for lithium-ion batteries xThe steps for preparing the -Si composite negative electrode material are as follows:

[0035] Step 1: Preparation of C@SiO2 composite material

[0036] 20g 30nm SiO2, 20g starch, and 10g carbon fiber were placed in a mixer, deionized water was added, and the mixture was processed at a speed of 350r / min for 6h. The slurry was taken out and dried at 120℃ for 8h to obtain a C@SiO2 composite material.

[0037] Step 2: Preparation of C@Si3N4 composite material

[0038] The prepared C@SiO2 composite material was placed in an atmosphere furnace, and nitrogen-methane mixed gas was introduced at a flow rate of 1500ml / min. It was heat treated at 1500℃ for 5h and naturally cooled to obtain a C@Si3N4 composite material.

[0039] Step 3, C-SiO x Preparation of -Si composite materials

[0040] The prepared C@Si3N4 composite material was placed in a vacuum furnace, steam was introduced, and heat treated at 1200℃ for 8h under a vacuum degree of 100Pa to oxidize and decompose Si3N4 to form SiO x phase and dispersed Si particles, namely C-SiO for lithium-ion batteries x -Si composite negative electrode material.

[0041] Prepared C-SiO x -Si composite negative electrode material structure diagram Figure 1 As shown, the composite material is divided into three parts: nano silicon particles, SiO x layer and surface carbon coating.

[0042] Example 2

[0043] C-SiO for lithium-ion batteries x The steps for preparing the -Si composite negative electrode material are as follows:

[0044] Step 1: Preparation of C@SiO2 composite material

[0045] 30g 50nm SiO2, 30g resin, and 10g carbon nanotubes were placed in a mixer, deionized water was added, and the mixture was processed at a speed of 400r / min for 8h. The slurry was taken out and dried at 120℃ for 8h to obtain a C@SiO2 composite material.

[0046] Step 2: Preparation of C@Si3N4 composite material

[0047] The prepared C@SiO2 composite material was placed in an atmosphere furnace, and nitrogen-acetylene mixed gas was introduced at a flow rate of 2000 ml / min. The mixture was heat treated at 1450°C for 8 h, and then naturally cooled to obtain a C@Si3N4 composite material.

[0048] Step 3, C-SiO x Preparation of -Si composite materials

[0049] The prepared C@Si3N4 composite material was placed in a vacuum furnace, steam was introduced, and heat treated at 1300℃ for 5h under a vacuum degree of 1000Pa to oxidize and decompose Si3N4 to form SiO x phase and dispersed Si particles, namely C-SiO for lithium-ion batteries x -Si composite negative electrode material.

[0050] The prepared C-SiOx-Si composite negative electrode material and metallic lithium were assembled into a button cell and subjected to constant current charge and discharge test at a current density of 0.1 A / g. The 100 cycle curves are shown in FIG. Figure 2 As shown, it can be seen that the prepared C-SiO x -Si composite negative electrode material has a first discharge specific capacity of 1713.2mAh / g, and a capacity retention rate of 85% after 100 cycles, demonstrating excellent electrochemical performance.

Claims

1. A C-SiO for lithium-ion batteries x -Si composite negative electrode material preparation method, characterized in that, The preparation method of the composite negative electrode material comprises the following steps: Step 1, preparation of C@SiO2 composite material: The SiO2-containing raw material and the carbon-containing raw material are mixed in a molar ratio of 1:3-6 and mixed evenly with deionized water to form a slurry, and the slurry is taken out and dried to obtain a C@SiO2 composite material; Step 2: Preparation of C@Si3N4 composite material: The prepared C@SiO2 composite material was placed in an atmosphere furnace, and gas was introduced at a flow rate of 1000-3000 ml / min. The material was heat treated at a temperature of 1200-1700°C for 5-10 h. After natural cooling, a C@Si3N4 composite material was obtained. The introduced gas is one of nitrogen, nitrogen-methane mixed gas, nitrogen-ethylene mixed gas, nitrogen-acetylene mixed gas or nitrogen-hydrogen mixed gas; Step 3, C-SiO x -Preparation of Si composite materials: The prepared C@Si3N4 composite material was placed in a vacuum furnace and steam or CO2 gas was introduced. -2 Heat treatment at 800~1400℃ for 1~10 h under vacuum degree of ~1000 Pa to oxidize and decompose Si3N4 to form SiO x phase and dispersed Si particles, namely C-SiO for lithium-ion batteries x -Si composite negative electrode material.

2. The C-SiO2 for lithium-ion batteries according to claim 1 x -Si composite negative electrode material preparation method, characterized in that, The SiO2-containing raw material is any one of nano-SiO2, silica, quartz, silicon powder, silica sol, silicic acid, methyl silicate, ethyl silicate, propyl silicate and butyl silicate, or a mixture of two or more thereof, and the particle size is 10 to 100 nm.

3. The C-SiO2 for lithium ion batteries according to claim 1 x -Si composite negative electrode material preparation method, characterized in that, The carbon-containing raw material is any one of sucrose, glucose, resin, citric acid, carbon fiber, carbon black, carbon nanotube and graphene, or a mixture of two or more thereof.

4. The C-SiO2 for lithium ion battery according to claim 1 x -Si composite negative electrode material preparation method, characterized in that, In the step 1, the mixing step specifically includes: placing the mixture into a mixer, adding deionized water, and processing at a speed of 200-500 r / min for 1-10 hours.

5. The C-SiO2 for lithium ion battery according to claim 4 x -Si composite negative electrode material preparation method, characterized in that, In the step 1, the drying step specifically includes: taking out the slurry and drying it at 80-150° C. for 5-10 hours.

6. The C-SiO for lithium ion battery according to claim 1 x -Si composite negative electrode material preparation method, characterized in that, The C-SiO x SiO-Si composite materials x In this phase, 0<x<2.

7. The C-SiO for lithium ion battery according to claim 1 x -Si composite negative electrode material preparation method, characterized in that, The C-SiO x -Si composite negative electrode material has a hollow structure, with nanoporous Si particles (1) dispersed inside, SiO x (2) attached to the surface of Si particles, C (3) evenly coated on SiO x -Si composite particle surface.

8. A lithium ion battery, characterized in that: The negative electrode material of the lithium ion battery is C-SiO prepared by the preparation method according to any one of claims 1 to 7. x -Si composite negative electrode material.

Images