A facile synthesis of phosphorus doped Si/SiO2/C with high coulombic efficiency and good stability as an anode material for lithium ion batteries

Abstract

Abstract Silicon (Si) has the drawbacks of large volume expansion and poor electronic conductivity to be overcome as the anode material for lithium ion batteries (LIBs). Herein, phosphorus (P) doped Si coated by dual layers of SiO2 and carbon (denoted as P-doped Si/SiO2/C) has been synthesized by a facile solid-state route. In that, commercial Si powder and polyvinyl butyral was used as raw material and carbon source, respectively. Importantly, the phosphoric acid was introduced as the doping agent, that also helped the formation of pure SiO2 coating layer rather than the mixture of SiO2 and less oxidized SiOx on surface of the Si material. The as-prepared P-doped Si/SiO2/C material exhibits an initial discharge capacity as high as 2860.3 mAh g−1 and an excellent inital coulombic efficiency of 86.7% at a current density of 200 mA g−1. After 150 cycles, charge capacity of 1389.8 mAh g−1 was retained, indicating the good cycle stability of P-doped Si/SiO2/C material, which is over three times higher than that of the Si/C material (449.2 mAh g−1) without phosphoric acid treatment. Additionally, a capacity enhancement of 25.7%, 40.7%, 79.1% 281.7% and 407.7% was achieved as compared to the Si/C material at the current densities of 100, 300, 600 1000 and 2000 mA g−1, respectively. The P-doping and SiO2 coating have played a significant role on the electrochemical performance by effectively improving the intrinsic electronic conductivity and further suppressing the volume expansion (∼40%) of Si in charge-discharge tests. It worth mentioning that the synthesis of P-doped Si/SiO2/C can be easily scaled up. Therefore, our work pave the way toward the industrilization of stable Si-based anode material with high capacity for LIBs.