SnO₂/SnVA/Cu–Sn Nanocomposites with a Hierarchical Porous Structure as Integrated Electrodes for Sodium-Ion Batteries

The development of Sn anodes for sodium-ion batteries that achieve both high areal capacity and excellent cyclability remains a significant challenge. Although Sn offers a high theoretical specific capacity, it undergoes a substantial 420% volume expansion. This expansion leads to rapid degradation, as the weak bonding between Sn and the current collector cannot withstand the induced mechanical strain, ultimately causing the loss of electrical contact with the active material. Herein, this study proposes a strategy that combines the structural design of hierarchical porous (nanopores + micropores) integrated electrodes with the optimization of the Sn-current collector interface to ensure a strong and stable bonding of Sn to the current collector. The resulting hp-SnO2/SnVA/Cu–Sn integrated anode integrates the stress adaptability of hp-Cu with the strong bonding force provided by the Cu–Sn alloy, thereby achieving high areal capacity while maintaining excellent cyclability. Ultimately, the hp-SnO2/SnVA/Cu–Sn offers an outstanding areal capacity of 1.73 mAh cm–2 at a current density of 1.0 mA cm–2, with a capacity retention of 89.60% after 500 cycles. Even at a higher current density of 3.0 mA cm–2, it exhibits an areal capacity of 1.43 mAh cm–2, demonstrating exceptional cycling stability and rate performance.