Tin-Containing Graphite For Sodium-Ion Batteries And Hybrid Capacitors

The limited Na-storage capacity of graphite anodes for sodium-ion batteries (similar to 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 SnCl2, 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 (similar to 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 similar to 93 Wh kg(-1)and 7.8 kW kg(-1), with a capacity retention of similar to 80 % after 8,000 cycles.