High Capacity Si-C Nanomaterials with Long Cycle Life for Lithium-Ion Battery

摘要

Si is very promising candidate for the anode material in lithium-ion battery as its theoretical specific capacity is 4200mAh/g, compared with graphite's 372mAh/g. However, volume changes during cycles cause pulverization and capacity fade. Improving cycle life and volume expansion are major challenges for the commercialization of Si anode. To solve these problems, Orange Power has mainly researched with two respects. One is attempting to realize non-spherical Si nanoparticle with low crystallinity for alleviating hoop tensile strength, which minimized pulverization of Si particles during cycles. Non-spherical nano-sized Si particles (D50 : 70～80nm, D100＜200nm) were obtained by simple milling process. In addition, its crystallinity was dramatically reduced by milling. The other is to construct clamping layer on the outer shell of Si-core for buffering volume expansion of Si-core. Clamping layer (Silicon carbide) was formed between nano-Si core and outmost carbon shell during carbonization process. Electrochemical measurements were carried out using anode prepared by mixture of graphite and Orange Power's Si-C nano-composite. The mixture ratio of graphite/Si-C nano-composite is 95/5. This anode showed initial capacity of 410mAh/g and initial coulombic efficiency of 88%. (Converting these values into Si-C nano-composite, the capacity and coulombic efficiency were 1600mAh/g and 72%, respectively.) In addition, its volume expansion was under 40% when lithiated. In pouch full cell test, its capacity retention was more than 80% after 300 cycles. We believe that Orange Power's Si-C nano-composite can be the substitution for high capacity anode materials.