Method for preparing silicon carbide alloy negative electrode material for lithium ion battery

Abstract

The invention discloses a method for preparing a silicon carbide alloy negative electrode material for a lithium ion battery; and a technical problem to be solved is to increase the circulation performance and the specific capacity of a silicon carbide composite negative electrode material. The method comprises the following steps of: dispersing nanometer silica powder in an organic solution to form a uniform nanometer silicon suspending liquid, then adding a silane coupling agent to the nanometer silicon suspending liquid, and finally carrying out carbon coating and thermal treatment. Compared with the prior art, the method has the advantages of increasing the dispersiveness of nanometer silicon particles in a silicon carbide composite material and inhibiting the volume effect caused by the conglobation of silicon in a lithium intercalation and deintercalation process by adding the silane coupling agent, thereby increasing the circulation performance and the specific capacity of the silicon carbide composite negative electrode material, wherein the capacity of the silicon carbide composite negative electrode material is larger than 500mAh / g, and the capacity retention rate is above 97% when the silicon carbide composite negative electrode material is circulated for 50 times; and according to the preparing method, the preparation cost is low, the technology is simple and controllable, and the silicon carbide alloy negative electrode materials with different capacities can be easily prepared by adjusting a weight proportion of Si powder, graphite and an organic matter.

Description

technical field [0001] The invention relates to a preparation method of a negative electrode material for a lithium ion battery, in particular to a preparation method of a silicon-carbon alloy negative electrode material. technical background [0002] As an energy storage system, lithium-ion batteries have attracted much attention due to their high energy efficiency, high energy density, and excellent storage performance. With the increasing demand for energy materials in the fast-growing economy, and the strong demand for new, efficient and environmentally friendly energy materials for products such as portable electronic devices and new energy vehicles, lithium-ion battery materials have developed rapidly. At present, graphite-based carbon anode materials are widely used in lithium-ion batteries. However, the theoretical lithium storage capacity of graphite-based carbon anode materials is low (372mAh / g), which can no longer meet the high-power or large-capacity requirement...

AI Technical Summary

Problems solved by technology

At present, graphite-based carbon anode materials are widely used in lithium-ion batteries. However, the theoretical lithium storage capacity of graphite-based carbon anode materials is low (372mAh / g), which can no longer meet the high-power or large-capacity requirements of new products for lithium-ion batteries. Therefore, the development of new high-performance anode materials is extremely urgent.

[0003] Silicon materials are considered to be one of the ideal candidate materials to replace graphite anode materials due to their high lithium storage capacity (theoretical capacity 4200mAh / g) and abundant resources. However, silicon has a serious volume effect in the process of intercalating lithium. Lithium atoms form alloy Li 4.4 For Si, the volume expansion reaches 300%. When the lithium ions are extracted, the volume shrinks severely. The continuous volume change will easily lead to the collapse of the material structure and the peeling off of the electrode material, resulting in poor cycle stability of the electrode.

Studies have shown that the use of nano-silicon to prepare silicon-carbon composite anode materials can reduce the absolute volume change of silicon, reduce the diffusion distance of lithium ions, and increase the electrochemical reaction rate. However, active nano-silicon particles are easy to agglomerate during charge and discharge. , resulting in capacity attenuation

In the prior art, the silicon-carbon alloy material prepared by ball milling or pyrolysis method has poor uniformity, and the dispersion of nano-silicon particles in the composite material is not good, which affects the performance of the silicon-carbon material

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