Fluorinated Carbon Nanohorns as Cathode Materials for Ultra-High Power Li/CFx Batteries.

Abstract

Fluorinated carbon (CFx) has ultrahigh theoretical energy density among cathode materials for lithium primary batteries. CFx, as an active material in the cathode, plays a decisive role in performance. However, the performance of commercialized fluorinated graphite (FG) does not meet this continuously increasing performance demand. One effective way to increase the overall performance is to manipulate carbon-fluorine (C─F) bonds. In this study, carbon nanohorns are first used as a carbon source and are fluorinated at relatively low temperatures to obtain a new type of CFx with semi-ionic C─F bonds. Carbon nanohorns with a high degree of fluorination achieved a specific capacity comparable to that of commercial FG. Density functional theory (DFT) calculations revealed that curvature structure regulated its C─F bond configuration, thermodynamic parameters, and ion diffusion pathway. The dominant semi-ionic C─F bonds guarantee good conductivity, which improves rate performance. Fluorinated carbon nanohorns delivered a power density of 92.5kWkg-1 at 50 C and an energy density of 707.6Whkg-1 . This result demonstrates the effectiveness of tailored C─F bonds and that the carbon nanohorns shorten the Li+ diffusion path. This excellent performance indicates the importance of designing the carbon source and paves new possibilities for future research.