Investigating FeVO₄ as a cathode material for aqueous aluminum-ion battery

Developing an aluminum-ion aqueous battery is extremely attractive for prospects of creating a super cheap, environmentally friendly and safe energy storage system. However, a lack of reversible cathode materials hampers the use of metallic Al as a high-capacity anode in an aqueous electrolyte. As opposed to insertion-type cathodes, the performance of conversion-type cathodes for Al-ion electrochemistry in an aqueous electrolytic environment remains poorly explored. As a first attempt to understand the performance of such conversion type materials for Al-ion intake, we herein report FeVO₄ as a potential cathode material with a significantly high capacity of 350 mA h g⁻¹. We use a combination of inhouse and synchrotron-based characterization techniques to confirm Al-ion electrochemical reaction with FeVO₄, and also determine how electrolyte pH has a mechanistic influence on the reversibility of aluminum-ion aqueous batteries.