Tungsten Oxytetrachloride as a Positive Electrode for Chloride-Ion Batteries

Abstract

Rechargeable chloride-ion batteries (CIBs) are a new emerging battery technology that can potentially provide high theoretical volumetric capacities at lower cost and higher abundance. However, research on CIBs is in its early stages, and the current challenge lies in finding suitable electrodes and electrolytes. Herein, tungsten oxychloride is introduced for the first time as a cathode candidate for use in CIB. WOCl4 enables the reversible transfer of nearly one Cl− per formula unit during electrochemical cycling, corresponding to an initial discharge capacity of 120 mAh g−1. A reversible capacity of 90 mAh g−1 (75%) is retained after 50 cycles. Postmortem analysis of cycled electrodes by X-ray diffraction, X-ray photoelectron spectroscopy, and Raman spectroscopy reveals the reversible chloride-ion transfer between the electrodes through a conversion mechanism. This work paves the way for the use of tungsten chloride-based electrode materials for battery applications.