Vanadium oxychloride as cathode for rechargeable aluminum batteries

Vanadium oxychloride (VOCl) with layered structure may be a potential cathode material for rechargeable aluminum batteries (RABs) due to its large interlayer spacing and high theoretical capacity. Herein, the VOCl material is employed as the cathode material of RABs for the first time. The corresponding electrochemical performance and mechanisms of the VOCl cathode are investigated. The VOCl cathode after the first charge delivers a high reversible discharge capacity of 124.7 mAh g⁻¹, which is ascribed to the AlCl₄⁻ deintercalation and the subsequent Al³⁺ intercalation. However, the discharge capacity fades to 41.5 mAh g⁻¹ after 100 cycles, which is mainly caused by the irreversible AlCl₄⁻ intercalation/deintercalation during cycling. The electrochemical capacity of the VOCl cathode in the RAB is dominated by the Al³⁺ intercalation/deintercalation after the first cycle, as confirmed by the electrochemical tests, energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). In addition, it is found that there is no evident lattice expansion when the AlCl₄⁻ or Al³⁺ is intercalated into the interlayers of VOCl.