Soft Carbon as Cathode with High Rate Performance for Dual-Ion Batteries via Fast PF6− Intercalation Improved by Surface Effect

Graphical From petroleum coke : Soft carbon cathode with superb rate performance for dual-ion batteries is presented. In situ XRD and Raman show that PF 6 − anions form stage-1 graphite intercalation compounds in the surface region, and directly stage-2 in the bulk, skipping the conversion from stage-4 to stage-2 due to the benefit of surface effect. The improved reaction kinetics results in better rate performance than that of conventional graphite. Dual-ion battery is a new type of battery in which both anions and cations participate in the energy storage process. However, this unique battery configuration imposes high requirements on the cathode, which typically presents a poor rate performance due to the sluggish diffusion dynamics and intercalation reaction kinetics of anions. Herein, we report petroleum coke-based soft carbon as the cathode for dual-ion batteries, exhibiting a superior rate performance with a specific capacity of 96 mAh g −1 at a rate of 2 C and 72 mAh g −1 remained even at 50 C. In situ XRD and Raman demonstrate that the anions can directly form lower-stage graphite intercalation compounds during the charge process owing to the surface effect, skipping the long evolutionary process from higher to lower stage, thus significantly improving the rate performance. This study highlights the impact of the surface effect and provides a promising perspective for dual-ion batteries.