High-Performance MnO2/Al Battery with In Situ Electrochemically Reformed AlxMnO2 Nanosphere Cathode

Aqueous Al-ion battery (AAIB) is regarded as a promising candidate for large-scale energy storage systems due to its high capacity, high safety, and low cost, with MnO2 proved to be a high-performance cathode. However, the potential commercial application of this type of battery is plagued by the frequent structural collapse of MnO2. Herein, an in situ, electrochemically reformed, urchin-like AlxMnO2 cathode is developed for water-in-salt electrolyte-based AAIBs. Benefiting from its unique alpha-MnO2 coated Mn2AlO4 structure, a high Al ion storage capacity is achieved together with a high discharge voltage plateau of 1.9 V by reversible MnO2 electrolysis. Consequently, the battery exhibits a high specific capacity of 285 mAh g(-1) and a high energy density of 370 Wh kg(-1) at a high current density of 500 mA g(-1). Improved stability with record capacity retention is also obtained at an ultrahigh current density of 5 A g(-1) after 500 cycles. Such a high-capacity and high-stability AlxMnO2 cathode would pave the way for in situ electrochemical transformation of cathode design and thus boost the practical application of AAIBs.

Automated summary

An in situ, electrochemically reformed, urchin-like AlxMnO2 cathode has been developed for water-in-salt electrolyte-based AAIBs, achieving high capacity and stability at high current densities, potentially boosting the practical application of AAIBs.