Sn–Ni alloy films were prepared by annealing tin-coated nickel foils at 463K for 0–25h, and their charge–discharge characteristics as negative electrodes for sodium secondary batteries were studied in an intermediate temperature ionic liquid Na[FSA]–K[FSA] (FSA=bis(fluorosulfonyl)amide) at 363K. As a result, a Sn–Ni film without annealing retained a reversible capacity of 343mAh (g-Sn)−1 after 100 charge–discharge cycles. In contrast, the annealed films had lower capacities and poorer cycleability. Possible mechanisms to understand the cycling performance were identified by X-ray diffraction and field-emission scanning electron microscopy studies.