Sn Negative Electrode Consists of Amorphous Structures for Sodium ion Secondary Batteries

Tin(Sn) and its alloys have been attracting attentions as a negative electrode material for sodium-ion secondary batteries with high theoretical capacity (Na 15 Sn 4 , ca. 847 mAh/g) and high electromotiveforce. There still remains the issue as regards the discharge capacity decrease with increasing the number of cycles. In order to improve cycle performance, there are many studies such as using Sn-Ni alloy, however, using Sn based alloy as negative electrode materials and it suffer from the disadvantage of lowering of discharge capacity. In this study, a deposition process for making Sn film which consists of amorphous structure for negative electrode of sodium ion secondary batteries utilizing electordeposition from aqueous bath was developed. The effect of additives on the surface morphology and microstructure of Sn film was investigated. Furthermore, we evaluated the effect of amorphous structure in the Sn film on cycle performance of the Sn negative electrode. Sn film has a good cycle characteristic (>50 cycles) and discharge capacity (> 400 mAh/g). Amorphous structure in the Sn film showed a microscopic effect on the volume change by sodiation and desodiation.