Effect of fluorine-containing additive on the electrochemical properties of silicon anode for lithium-ion batteries

Silicon anode is a promising candidate as an alternative to the conventional graphitic anode in lithium-ion batteries. In this work, silicon anode was modified by NH₄ F using a facile method in air. The concentration of NH₄ F on the electrochemical performance was systematically checked. The results showed that 5wt% NH₄ F-modified silicon anode exhibited enhanced cycle performances, the first discharge specific capacity was 3958 mAh·g^-1 with 86.45% as the coulombic efficiency at a current density of 0.4 A · g^-1. The capacity could maintain at 703.3 mAh·g^-1 after 50 cycles, exhibiting a much better cycle stability than pristine silicon anode (329.9 mAh·g^-1 after 50 cycles). SEM images confirm that NH₄ F can alleviate the volume expansion of silicon since LiF can generate at the surface, which is beneficial to the stability of solid-electrolyte interphase (SEI).