Tin‐Containing Graphite for Sodium‐Ion Batteries and Hybrid Capacitors

Abstract

Abstract The limited Na‐storage capacity of graphite anodes for sodium‐ion batteries (∼110 mAh g −1 ) is significantly enhanced by the incorporation of nanosized Sn (17 wt%). The composite (SntGraphite), prepared by simple annealing of graphite with SnCl 2 , shows a specific capacity of 223 mAh g −1 (at 50 mA g −1 ) combined with excellent cycle life (i. e., 96 % of capacity retention after 2,200 cycles at 1 A g −1 ) and initial Coulomb efficiency (90 %). The combined storage of sodium in graphite (by solvent co‐intercalation) and Sn (by alloy formation) is followed by in situ X‐ray diffraction and in situ electrochemical dilatometry (ECD). While the additional tin almost doubles the electrode capacity, its contribution to the electrode expansion (∼3 %) is surprisingly small. The use of SntGraphite as anode for sodium‐ion hybrid capacitors with activated carbon as cathode provides a maximum energy and power density of ∼93 Wh kg −1 and 7.8 kW kg −1 , with a capacity retention of ∼80 % after 8,000 cycles.