ZnIn2S4: A promising anode material with high electrochemical performance for sodium-ion batteries

Abstract In this study, ZnIn2S4 (B-ZIS) and ZnIn2S4/C (S-ZIS) composites anode are synthesized using hydrothermal method and followed by ball-milling process. The initial discharge/charge capacities for bare ZnIn2S4 (B-ZIS) are 524 and 378 mAh g−1 under a current density of 1 A g−1, which suffers from gradually capacity fading. To improve its cycle stability, high-energy ball-milling process (HEBM) with carbon black is applied to fabricate S-ZIS spherical particles. The as-obtained composite anode exhibits enhanced electrochemical performances not only on cycle stability, but also reversible capacity. The discharge and charge capacity of S-ZIS approach to 823 and 679 mAh g−1 at the first cycle and retain 468 and 459 mAh g−1 after 500 cycles at the high current density of 1 A g−1. Furthermore, ex situ X-ray diffraction (XRD) and ex situ X-ray photoelectron spectroscopy (XPS) techniques are used to monitor the evaluation of crystal structure of B-ZIS during charge and discharge processes. The results indicate that the metallic Zn and In were observed at low potential voltage during sodiation process and successfully converted back to spinel phase at above 0.5 V. The presence of high reversibility nature of B-ZIS may leads to the superior cycling and excellent rate capability of S-ZIS which makes ZnIn2S4 a potential anode material of sodium ion batteries.