Vanadium oxychloride/magnesium electrode systems for chloride ion batteries.

We report a new type of rechargeable chloride ion battery using vanadium oxychloride (VOCl) as cathode and magnesium or magnesium/magnesium chloride (MgCl2/Mg) as anode, with an emphasis on the VOCl-MgCl2/Mg full battery. The charge and discharge mechanism of the VOCl cathode has been investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and electrochemical measurements, demonstrating the chloride ion transfer during cycling. The VOCl cathode can deliver a reversible capacity of 101 mAh g(-1) at a current density of 10 mA g(-1) and a capacity of 60 mAh g(-1) was retained after 53 cycles in this first study.