Efficient conversion of sand to nano-silicon and its energetic Si-C composite anode design for high volumetric capacity lithium-ion battery

Silicon is an attractive anode material for Li-ion cells, which can provide energy density 30% higher than any of the today's commercial Li-ion cells. In the current study, environmentally benign, high abundant, and low cost sand (SiO2) source has been used to prepare nano-silicon via scalable metallothermic reduction method using micro wave heating. In this research, we have developed and optimized a method to synthesis high purity nano silicon powder that takes only 5 min microwave heating of sand and magnesium mixture at 800 degrees C. Carbon coated nano-silicon electrode material is prepared by a unique method of coating, polymerization and finally insitu carbonization of furfuryl alcohol on to the high purity nano-silicon. The electrochemical performance of a half cell using the carbon coated high purity Si is showed a stable capacity of 1500 mAh g(-1) at 6 A g(-1) for over 200 cycles. A full cell is fabricated using lithium cobalt oxide having thickness approximate to 56 mu m as cathode and carbon coated silicon thin anode of thickness approximate to 9 mu m. The fabricated full cell of compact size exhibits excellent volumetric capacity retention of 1649 mAh cm(-3) at 0.5 C rate (C = 4200 mAh g(-1)) and extended cycle life (600 cycles). The full cell is demonstrated on an LED lantern and LED display board.