Preparation method of expanded graphite/silicon@carbon negative electrode material for lithium ion batteries

Abstract

The invention relates to a preparation method of an expanded graphite / silicon@carbon negative electrode material for lithium ion batteries. The method comprises the following steps: introducing oxygen-containing functional groups to the lamellae of expanded graphite subjected to acid treatment to obtain oxidized expanded graphite, soaking the oxidized expanded graphite in an ethanol solution to obtain an oxidized expanded graphite ethanol solution mixture containing rich hydroxyls on the surface, stirring the mixture with a silane coupling agent to obtain an alkylated expanded graphite ethanol solution mixture, adding silicon nanoparticles to obtain an alkylated expanded graphite / silicon ethanol mixed solution, adding the mixed solution into an amorphous carbon precursor, reacting, collecting the precipitate, drying, carbonizing, and soaking in a hydrofluoric acid solution to obtain the expanded graphite / silicon@carbon negative electrode material for lithium ion batteries. The method has the advantages of favorable loop stability and favorable magnification property.

Description

technical field [0001] The invention relates to an expanded graphite / silicon@carbon negative electrode material for a lithium ion battery and a preparation method thereof. [0002] technical background [0003] Lithium-ion batteries have the advantages of high theoretical specific capacity, long cycle life, and high safety, and are widely used in portable electronic devices, such as mobile phones, computers, and digital cameras. Commercial lithium-ion battery anode material graphite has low lithium storage capacity (theoretical specific capacity is 372mAh / g) and poor rate performance, which cannot meet the energy demand of large-scale energy storage devices. Therefore, it is particularly important to develop anode materials for lithium-ion batteries with high capacity and long cycle life. Silicon has attracted the attention of many researchers because of its high theoretical specific capacity (4200mAh / g), low charge and discharge voltage, and abundant reserves. However, the...

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Problems solved by technology

[0006] 1. Simple physical mixing has problems such as agglomeration of silicon nanoparticles and uneven mixing of expanded graphite and silicon nanoparticles

[0007] 2. Although the method of ball milling improves the mixing degree of expanded graphite and silicon nanoparticles to a certain extent, due to the insufficient bonding force between silicon nanoparticles and expanded graphite, silicon nanoparticles fall off from expanded graphite sheets during charging and discharging.

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