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Silicon @ carbon composite material with egg yolk shell structure and preparation and application thereof

A technology of carbon composite materials and egg yolk shells, applied in nanotechnology for materials and surface science, structural parts, final product manufacturing, etc., can solve problems such as structural volume changes and poor conductivity

Active Publication Date: 2019-01-22
CHANGSHA UNIVERSITY OF SCIENCE AND TECHNOLOGY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0005] In order to solve the technical deficiencies of the existing silicon-based negative electrode materials, which are prone to huge volume changes and poor conductivity, the present invention provides a method for preparing a silicon@carbon composite material with an egg yolk shell structure, aiming to obtain a silicon-based composite material with excellent electrical properties Silicon@Carbon Composites

Method used

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  • Silicon @ carbon composite material with egg yolk shell structure and preparation and application thereof
  • Silicon @ carbon composite material with egg yolk shell structure and preparation and application thereof
  • Silicon @ carbon composite material with egg yolk shell structure and preparation and application thereof

Examples

Experimental program
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Effect test

Embodiment 1

[0078] Preparation of mesoporous silicon-carbon composite (Si@C) anode material with egg yolk shell structure

[0079] Step 1): Mix the SBA-15 precursor into Mg powder (99%) and sodium chloride according to the molar ratio (SBA:Mg:NaCl=1:1.05:4), mix and grind by hand for 30 minutes in a dry method. In an argon atmosphere with 5% hydrogen, the temperature is raised to 300°C at a rate of 5°C / min and kept for 2h, and then the temperature is raised to 650°C at a heating rate of 5°C / min and the temperature is kept for 6h. The product after roasting is diluted with hydrochloric acid Carry out multiple times of cleaning and centrifugal drying to obtain mesoporous silicon nanomaterials;

[0080] Step 2): Next, ultrasonically disperse 1g of mesoporous silicon nanomaterial in 5mL of water to obtain a nanosilica dispersion, and then mix the polyvinyl alcohol solution to obtain mixed solution A (the mass ratio of mesoporous silicon nanomaterial / polyvinyl alcohol is 2 :1), and then mix the mi...

Embodiment 2

[0095] Compared with Example 1, the only difference is that in step 1), the temperature is raised to 300° C., and after holding for 2 hours, the temperature is then raised to 550° C. for 6 hours.

[0096] Assembled into a button according to the method of Example 1. The measured electrical performance is that the specific discharge capacity of the first, second, fifth, and tenth charge and discharge cycles are 834, 612, 503, 407 mAh g, respectively -1 Compared with Example 1, its cycle performance is very poor. After the 100th cycle, the capacity decays to 335mAh g -1 , At a current density of 1A g -1 Hourly discharge specific capacity is 391mAh g -1 , At 2A g -1 Hourly discharge specific capacity is 347mAh g -1 According to Example 1 and Example 2, it is found that the reaction is not complete under these conditions, and there is a layer of white silicon oxide that has not been reduced, so that the product mesoporous nano-silicon material is reduced. And because the material conta...

Embodiment 3

[0098] Compared with Example 1, the only difference is that in step 2), the ratio of mesoporous nano-silicon material, surfactant, and aluminum salt is 1:1:2.

[0099] According to the method of Example 1, it is assembled into a button, and the electrical performance is measured. After the 90th cycle, the capacity quickly decays to 183mAh g -1 Compared with Example 1, the increase in AC impedance is increased by 400%. From Example 1 and Example 3, it is found that if too much surfactant is added, these excessive surfactant molecules will be disorderly in the solution and cannot form a colloid in the solution. Therefore, it is impossible to prepare a silicon carbon negative electrode material with an egg yolk shell structure, and cannot withstand the expansion of the silicon core. So the optimal ratio of adding silicon powder, surfactant and aluminum salt is 2:1:4. Similarly, if the ammonia is added in excess, it will produce aluminum hydroxide precipitation.

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Abstract

The invention belongs to the field of battery negative electrode materials, and particularly discloses a preparation method of silicon @ carbon composite material with egg yolk shell structure, whichis characterized in that the preparation method comprises the following steps: step 1) mesoporous nano SiOX, molten salt and magnesium powder are mixed and calcined to obtain mesoporous nano silicon;2) mesoporous nano-silicon powder, the surfactant and the aluminum salt prepared in the step 1) are added into a solution at a pH value of 2, and the mesoporous nano-silicon powder, the surfactant andthe aluminum salt are added into the solution at a pH value of 2; 7, coat aluminum hydroxide colloid on that surface of nano silicon to obtain silicon / aluminum hydroxide colloid composite material; 3) silicon / aluminum hydroxide colloidal composite material is mixed with an organic carbon source, carbon is coated on the surface of the silicon / aluminum hydroxide colloidal composite material, and then the silicon / aluminum hydroxide colloidal / carbon composite material is acuquried by carbonizing operation; 4) aluminum hydroxide colloid of the material obtained in the step 3) is removed by using an acid solution and / or an alkali solution to prepare the silicon @ carbon composite material with the egg yolk shell structure. The invention can stably prepare the silicon @ carbon composite materialwith the egg yolk shell structure, and the material has excellent electrical performance.

Description

Technical field [0001] The invention belongs to the field of battery negative electrode materials, and particularly relates to a lithium ion battery negative electrode material in which a fast ion conductor carbon shell with an egg yolk shell structure is coated with a silicon-based material. Background technique [0002] Rechargeable lithium-ion batteries are known as the new generation of "green secondary batteries" because of their long working life, high energy density, low self-discharge, high power density / coulomb efficiency, no pollution, and excellent safety performance. One of the most widely used energy storage tools. People’s commercial use of lithium-ion batteries originated in 1990. In the following two decades, the use of lithium-ion batteries has grown rapidly and has been widely used in various industries, especially large-scale hybrid vehicles and small portable electronic products. The requirements for various indicators and parameters of ion batteries are also...

Claims

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Application Information

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IPC IPC(8): H01M4/36H01M4/38H01M4/485H01M4/62H01M10/0525H01M10/058B82Y30/00
CPCB82Y30/00H01M4/366H01M4/386H01M4/485H01M4/625H01M10/0525H01M10/058Y02E60/10Y02P70/50
Inventor 肖忠良夏妮宋刘斌池振振曹忠童海霞
Owner CHANGSHA UNIVERSITY OF SCIENCE AND TECHNOLOGY
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