Batteries: One size fits all

Energy Environ. Sci. http://doi.org/bppt (2016)

In comparison with their non-aqueous counterparts, rechargeable aqueous batteries offer an alternative and attractive energy storage means owing to their low cost and high safety. However, rechargeable aqueous batteries using metal cations such as Li⁺, Mg²⁺ and Al³⁺ as charge carriers often suffer from poor electrochemical performance. Furthermore, although many electrode materials possess promising properties for Li-ion batteries, in general those do not work well for non-Li⁺ monovalent ion or multivalent ion batteries. David Lou and colleagues in Singapore and China have now reported reversible redox reactions of a bismuth oxide (Bi₂O₃) electrode material in a diverse range of metal ion salts and demonstrated high performance of an aqueous Bi₂O₃/LiMn₂O₄ full cell.

The researchers showed that the Bi₂O₃ material works as a remarkable rechargeable electrode in a total of seventeen metal ion electrolytes including Na⁺, K⁺, Mg²⁺, Ca²⁺, Sr²⁺ and even Al³⁺-based nitrates/chlorides/sulfates. In addition to showing the stable and significant redox behaviours, the Bi₂O₃ electrode also effectively suppressed hydrogen evolution, an undesired reaction that often occurs in aqueous electrolytes. The researchers ascribed the charge storage mechanism in the Bi₂O₃ electrode to a conversion reaction from the face-centred cubic Bi₂O₃ to elemental Bi, which is in contrast to the conventional intercalation mechanism that often does not involve significant changes in valence state.