| 초록 |
A lithium fluoride (LiF), formed with lithium ion and fluorine ion, is one of the SEI components and thermally and chemically stable for the Lithium ion battery (LIB). In this study, the two types of C-F bonds presented as (SI) and covalent (CV) types were introduced on the graphite surface to investigate which one has main factor to form the LiF after charging step and to has more cycle stability. Disassembled anode surface after charge-discharge cycles was investigated by XPS of F1s deconvolution to confirm the LiF content. The graphite with GSI has 29% fluorine on the surface (pristine: 5%, graphite with GCV: 4%) and the most fluorine on the graphite surface is formed as LiF. To evaluate the cycle stability, assembled coin-cell was charge-discharge steps for 100 cycle at 1 C-rate. The retention between first and 100th discharge capacity of GSI is 98.9% (pristine: 89.8%, GCF: 91.7%). Thus, the semi-ionic C-F bonds can improve the cycle stability of the LIB. |
