Preparation of nanoporous SiO2/C derived from rice husk as anode material in SiO2/C||LiFePO4 full-cell through alkaline activation treatment

Abstract

Silicon-based materials such as pure silicon (Si), silicon monoxide (SiO), silica (SiO2), are considered promising anode for future high power energy Li-ion batteries. Among them, SiO2 has garnered attention owing to its outstanding features such as high theoretical capacity (1961 mAh g−1), abundant reserve, and low-cost processing. However, the large expansion and shrinkage of the Si and SiO2 volume during lithiation/delithiation reaction are still the main barriers for practical application. In this study, SiO2 derived from rice husks and activated by KOH displayed a nanoporous structure with a porous matrix carbon that can absorb the volume expansion during lithiation process and facilitate the diffusion of Li+ ion along the pores to minimise the dendrite growth at the local area. Through activation treatment, the surface area of SiO2 increases up to 278.875 m2 g−1 with a pore volume of 0.191 cm3 g−1 and the average pore diameter is about 0.771 nm. The cycling results showed that rice husk ash mixed with KOH at a ratio of 1:0.5 offered the best capacity retention of SiO2/C anode material in half-cell. In full-cell configuration of SiO2/C||LiFePO4, the the negative electrode/positive electrode capacity ratio (N/P) ratio of 1.2 exhibited the most stable performance with the highest capacity retention.