Hierarchical Storage Behavior of Tetrafluoroborate Anion in Graphite Electrodes

Anion-intercalated graphite is one of the feasible solutions for high-energy devices. Various characteristics of graphite may influence its overall performance. In this work, three homologous graphites with different particle sizes are selected as positive electrodes to accommodate tetrafluoroborate anion from propylene carbonate, based on activated carbon/graphite capacitors. In situ X-ray diffraction, Raman spectroscopy and electrochemical dilatometry are combined organically to identify the hierarchical storage behavior of anions in graphite electrodes. The graphite with minimal size exhibits a prior anion accumulation in the shallow region before notable expansion in the crystal structure. This extra charge storage leads to a higher capacity at the normal current density (0.1 A g(-1)), however, also drags down the anionic de-intercalation process and causes a significant capacity fade at high discharge rate. (c) 2019 The Electrochemical Society.