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 is modified by NH4F using a facile method in air. The concentration of NH4F on the electrochemical performance is systematically checked. The 5wt%NH4F-modified silicon anode exhibits enhanced cycle and rate performances, the first discharge specific capacity is 3958 mAh·g-1 with 86.45% as the coulombic efficiency at 0.4A·g-1. The capacity can 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 NH4F can alleviate the volume expansion of silicon since LiF can be generated at the surface which is beneficial to the stability of solid-electrolyte interphase (SEI).