An Electrochemical Study on the Impact of Charging Parameters on the Electrochemical Performance of Alloy-Based C/Sn Composite Anodes for Sodium-Ion Batteries

Abstract

The electrochemical performance of C/Sn composite anodes (≈11 wt% carbon) for sodium-ion batteries is systematically investigated under varying charging conditions. Galvanostatic cycling with potential limitation reveals a significant influence of charging protocols on capacity and stability. An optimized protocol, starting with a low current (74.4 mA g−1) followed by higher currents (372 mA g−1), achieves a first discharge capacity of 749 mAh g−1, an initial Coulombic efficiency of 84.0%, and a stable capacity of 536 mAh g−1 after 100 cycles. A thorough investigation of charge/discharge profiles and incremental capacity analysis reveals a novel, current-induced desodiation process at 0.2 V, enhancing cyclability. Asymmetric cycling reveals interdependence between sodiation and desodiation, with capacity fading linked to a reaction at 0.26 V. Cut-off potential adjustments allows isolation of individual dealloying processes. The first process at 0.15 V remains stable under varying charging currents, while the second desodiation process (≈0.26 V) transforms from phase transition to solid solution. Long-term cycling identifies potential indicators of performance degradation, which could be mitigated by modifying cycling parameters. An advanced understanding of the complex electrochemical mechanisms in the Na/Sn alloy system is essential for developing protocols to further improve high-capacity anode materials for sodium-ion batteries.