Based On Silicon Carbon Composite Material For High Performance Lithium Ion Battery

Since rechargeable lithium ion batteries(LIBS) were invented by Sony in 1992, they were used in many fields, which is due to their many advantages, such as lighter weight, higher energy density, longer cycle life, more environmentally friendly than the traditional lead-acid batteries, etc. However commercial lithium ion batteries anode materials are still using graphite as anode, which hadn't changed too much for nearly twenty years. Inaddition, they were suffering from low specific capacity. Hence, researches for high capacity lithium ion battery anode materials have become the key to improve the battery storage performance. Various anode materials have been studied in terms of high storage capacity and cyclic stability in the last couple of decades[4]. Among these, silicon is considered to be the next generation lithium-ion anode materials with the highest theoretical specific capacity(Li4.4Si=4200 mAh/g) of all the known materials and mature silicon semiconductor industry. However, the application of silicon still have significant challenges such as large volume changes(>300%) during lithiation and delithiation, unstable solid-electrolyte interphases(SEI), low electrical conductivity and low initial coulombic efficiency.In this article, we use plasma enhanced equipment to prepare low dimension and high purity silicon nanoparticles and P doped silica nanoparticles. Though improving the gas control system, plasma enhanced equipment reaction cavity system, collecting system and exhaust gas treatment system, finally we obtained the average diameter of 7.3 nm and the purity of 99.95% siliconnano particles.Since siliconnano particles are easy to reunite, we modified silicon nanoparticles by silane coupling agent KH550. As a result, the dispersion of nano silicon in oil system were improved, and a cell based on the preparation of the modified material cycle stability is also improved. In addition, we also studied the effect of different adhesive and electrolyte additive in lithium ion batteries, and found that hydrophilic binders are more suitable for silicon-based anodes and electrolyte additive can improve the cyclic stability and initial coulombic efficiency.We also synthesized sodium alginate as pyrolytic carbon to coat silicon nanoparticles, thermal reduction of graphene oxide to coat silicon nanoparticles and n-Si nanoparticles as lithium-ion battery anodes. Thermal reduction of graphene oxide can be used as a skeleton structure to coat silicon nanoparticles and provide high-speed channel for lithium ions transport due to the good conductivity of graphene. Among these, RGO/n-Si nanocomposite materials shows an excellent cycle performance(200 mAh/g for 200 cycles) and good ratio performance(under the current rate of 5 C, discharge specific capacity is 705 mAh/g).