Highly reversible carbon-nano-silicon composite anodes for lithium rechargeable batteries

A high-performance carbon-Si composite anode for lithium rechargeable batteries was developed. Si powder was coated with amorphous carbon by pyrolyzing polyvinyl chloride and chlorinated polyethylene at 900 degrees C for 2 h. The electrochemical performance of the carbon-Si composite anode depended on the Si particle size and the carbon content of the composite. A carbon-nano-size Si (average size 50 nm) composite with 48 wt.% carbon showed an excellent performance. The coulombic efficiency in the first cycle was 69.2% and the second cycle reversible discharge capacity of 970 mAh g(-1). The capacity fade on cycling was 0.24% per cycle during the first 40 cycles. The carbon-micron-sized Si (average size 4 mu m) composite showed a high coulombic efficiency of 78.6% in first cycle, but with poor cycling performance. The capacity fade within 30 cycles was 1.7% per cycle. The effect of the chlorine content in the precursor on the cycling performance was not detectable. (C) 2008 Elsevier B.V. All rights reserved.