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.

Automated summary

The limited Na-storage capacity of graphite anodes for sodium-ion batteries can be significantly enhanced by incorporating nanosized Sn. The composite, prepared by simple annealing of graphite with SnCl2, shows high specific capacity, excellent cycle life, and initial Coulomb efficiency. The study suggests the potential of using Sn-enhanced graphite as an anode for high-performance sodium-ion hybrid capacitors.