Sn-Ni alloy films were prepared by annealing tin-coated nickel foils at 463 K for 0-25 h, 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 363 K. As a result, a Sn-Ni film without annealing retained a reversible capacity of 343 mAh (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. (C) 2016 Elsevier Ltd. All rights reserved.