Confirming reversible Al 3+ storage mechanism through intercalation of Al 3+ into V 2 O 5 nanowires in a rechargeable aluminum battery

As a new type of multi-electron transfer device, rechargeable aluminum batteries are promising post-lithium ion batteries owing to their high theoretical energy density. However, it is unknown whether Al3+ can be reversibly stored in the lattice of the host electrode material because of its small cation diameter and high valence state, thus trapping it tightly in lattice or defect sites. Here, we report the reversible storage of Al3+ in V2O5 nanowires. It is found that Al3+ intercalates into crystalized V2O5 nanowires in the first discharge. Meanwhile, this electrochemical intercalation leads to the reduction of V5+ and the formation of an amorphous layer on the edge of nanowires. In the subsequent cycling, a new phase forms along the nanowires’ edges and a two-phase transition reaction occurs. Our findings demonstrate clearly for the first time that it is possible that Al3+ can be inserted into the metal oxide and stored reversibly through intercalation and a phase-transition reaction, which is expected to inspire more comprehensive investigations for rechargeable aluminum batteries.