Preparation method of lithium ion battery porous silicon carbon composite negative material

Abstract

The invention puts forwards a preparation method of a lithium ion battery porous silicon carbon composite negative material. The prepared porous silicon carbon composite material simultaneously has the characteristics of high capacity and excellent circulating stability. Micron silicon and nanometer aluminum powder are promoted to be compounded by utilizing a high-energy ball milling method, a porous silicon material can be formed through acid etching, and through a porous structure, the volume change of silicon in the discharging process is relieved to a great extent. Meanwhile, the stress generated by the volume change of the silicon can be effectively buffered through taking graphite as a dispersion matrix and in combination with a secondary surface amorphous carbon coating technology of the composite material, so that the circulating stability of the material is improved. The preparation method of the material has the advantages of simplicity, low cost and easiness in industrial production.

Description

[0001] technical field [0002] The invention relates to a preparation method of a lithium-ion battery negative electrode material, in particular to a preparation method of a lithium-ion battery silicon-carbon composite negative electrode material. [0003] technical background [0004] As a green, high-energy and environmentally friendly chemical power source, lithium-ion batteries have been widely used in portable devices such as mobile phones and notebooks. As a high-energy power source for the development of high-power batteries such as electric vehicles and motorcycles, it is urgent to increase the energy density of ion batteries. At present, graphite carbon has good cycle performance as the negative electrode material of lithium-ion secondary batteries, but the disadvantage is that the specific capacity is low, and the performance of carbon electrodes is greatly affected by the preparation process, which limits the application of high-energy lithium-ion batteries such...

AI Technical Summary

Problems solved by technology

However, silicon-based negative electrode materials are accompanied by large volume changes (>300%) during charge and discharge, and continuous volume changes can easily lead to material structure collapse and electrode material peeling, resulting in silicon particle breakage and pulverization, resulting in conductive network Separation occurs between silicon particles, the capacity drops rapidly, and the cycle performance deteriorates

In response to these problems, researchers have widely used the method of compounding silicon-based composite materials to improve their cycle performance. Using the synergistic effect between the components of the composite material, the purpose of complementary advantages can be achieved, such as with conductive polymers, metal nitrides, etc. , silicon oxide composites have been improved to a certain extent, but not ideal

It has been reported that using nano-silicon as the active material and coating it with amorphous carbon, the silicon-carbon composite material can have high lithium storage capacity and good cycle performance at the same time. For example, Magasinski et al. adopted a bottom-up self-assembly route, A silicon-carbon composite material with a hierarchical structure was prepared. The porosity of the particle itself can adjust the volume change of silicon during the intercalation / extraction process, and the reversible capacity reaches 1950 mAh / g (Nature materials. 2010, 9: 353-358), However, nano-silicon raw materials are expensive and the output is low, and the cost of the prepared silicon-carbon composite material is high and it is difficult to achieve the goal of industrialization and commercialization.

Kim et al prepared a silicon-carbon composite material with a reversible capacity of 613 mAh / g using cheap micron silicon powder as raw material by mechanical force-chemical ball milling (Journal of Power Sources. 2010, 195: 6031–6036), Li Hong et al. A silicon-carbon composite material with a "Yuanxiao" structure has been invented with commercial micro-silicon as raw material, which has high charging capacity and good safety (authorized announcement number CN 1328805C). There will be a serious volume effect during the discharge process, which will reduce the capacity retention rate during the cycle, and the prepared material will have poor cycle performance