Electrochemical performance of copper phosphosulfide (Cu3PS4) towards magnesium ion storage

•Cu3PS4 and Cu3PS4-SWCNT composite have been synthesized and characterized.•Rechargeable Mg battery with high capacity and cycling stability are achieved.•Rate performance up to 2 A g−1 is observed.•Ex situ Raman and XPS studies reveal conversion reaction as the mechanism of storage. Rechargeable magnesium batteries are good alternates for large scale energy storage applications and development of electrolytes as well as electrode materials are being pursued. In the present study, a cost-effective electrode material made of naturally abundant elements, Cu3PS4 is proposed for rechargeable magnesium battery. The electrochemical performance of Cu3PS4 is evaluated in different potential ranges. Further enhancement in the performance is achieved by using a carbon nanotube composite. The optimized electrode can deliver high capacity of 130 mAh g−1 at 50 mA g−1 current density and high cycling stability of 500 cycles with 80 % capacity retention at 1000 mA g−1 current density at room temperature. The possible mechanism for Mg2+ storage is probed by ex-situ X-ray diffraction (XRD), Raman spectroscopy and X-ray photoelectron spectroscopy (XPS).