Nitrogen and fluorine co-doped graphene for ultra-stable lithium metal anodes

The heteroatom doping strategies have been utilized to effectively improve the performance of the carbon-based hosts, such as graphene, for lithium (Li) metal in high energy density lithium metal batteries. However, solely doped graphene hosts often need the assistance of other materials with either better lithiophilicity or electronic conductance to achieve smooth and efficient deposition of Li, which adds extra weight or volume. Herein, graphene co-doped by nitrogen and fluorine (NFG) is employed as a stable host for Li, where the N-doping provides lithiophilicity and electronic conductivity lacked by F-doping and the F-doping facilitates fast formation of solid electrolyte interphase (SEI) retarded by N-doping. The well regulation of Li plating/stripping and SEI formation is verified by quickly stabilized and small-magnitude voltage hysteresis, which stands out in Li hosts based on doped graphene and leads to excellent long-term cycling performance of NFG based electrodes. A voltage hysteresis of 20 mV is observed for more than 850 h in the symmetrical cell. The remarkable efficiency of lithium usage is confirmed by the high-capacity retention of a full cell paired with LiFePO4 (LFP), which exceeds 70% after 500 cycles. This work presents an innovative perspective on the control of Li plating/stripping by simultaneously introducing two kinds of dopants into graphene and paving the way for exploring practical Li metal batteries.