Enhanced electrochemical performance of N, F co-doped and etched needle coke-based lithium-ion battery anode materials by NF3 plasma treatment

Abstract

NF3 plasma treatments were used to improve the electrochemical properties of needle coke-based lithium-ion battery (LIB) anode materials. The effects of the NF3 plasma treatments on the chemical, structural, and morphological properties of the needle cokes were evaluated with various analyses, and simultaneous heteroatom doping coupled with surface etching was identified. With these effects, N and F functional groups and micropores were generated on the surfaces of the needle cokes. The NF3 plasma-modified needle cokes were analyzed with LIB performance tests, and considerable enhancements were observed in the discharge capacities, rate capabilities and cycling stabilities. The resulting nitrogen functional groups and micropores improved the lithium storage capacities and rates by providing lithium-ion adsorption sites. The fluorine functional groups enhanced the cycling stability by forming LiF-based SEI layers. These effects of the NF3 plasma treatment on the electrochemical properties were proven with analytical techniques, and mechanisms for the overall process were suggested based on the results. The NF3 plasma-treated needle cokes are promising materials for fast charging LIB anodes with high stabilities and competitive discharge capacities.