High-Power-Density, High-Energy-Density Fluorinated Graphene for Primary Lithium Batteries

Li/CF_x is one of the highest-energy-density primary batteries; however, poor rate capability hinders its practical applications in high-power devices. Here we report a preparation of fluorinated graphene (GF_x) with superior performance through a direct gas fluorination method. We find that the so-called "semi-ionic" C-F bond content in all C-F bonds presents a more critical impact on rate performance of the GF_x in comparison with sp² C content in the GF_x, morphology, structure, and specific surface area of the materials. The rate capability remains excellent before the semi-ionic C-F bond proportion in the GF_x decreases. Thus, by optimizing semi-ionic C-F content in our GF_x, we obtain the optimal x of 0.8, with which the GF_0.8 exhibits a very high energy density of 1,073 Wh kg^-1 and an excellent power density of 21,460 W kg^-1 at a high current density of 10 A g^-1. More importantly, our approach opens a new avenue to obtain fluorinated carbon with high energy densities without compromising high power densities.