Defect Modulation in Cobalt Manganese Oxide Sheets for Stable and High‐Energy Aqueous Aluminum‐Ion Batteries

Abstract

AbstractRechargeable aqueous Al‐ion batteries (AIBs) are promising low‐cost, safe, and high energy density systems for large‐scale energy storage. However, the strong electrostatic interaction between the Al3+ and the host material, usually leads to sluggish Al3+ diffusion kinetics and severe structure collapse of the cathode material. Consequently, aqueous AIBs currently suffer from low energy density as well as inferior rate capability and cycling stability. Here, defective cobalt manganese oxide nanosheets are reported as cathode material for aqueous AIBs to improve both reaction kinetics and stability, delivering a record high energy density of 685 Wh kg−1 (based on the masses of the cathode and anode) and a reversible capacity of 585 mAh g−1 at 100 mA g−1 with a retention of 78% after 300 cycles. The impressive energy density and cycling stability are due to a synergistic effect between the substituted cobalt atoms and the manganese vacancies, which improve the structural stability and promote both electron conductivity and ion diffusion. When applied in aqueous Zn‐ion batteries, a high specific energy of 390 Wh kg−1 at 100 mA g−1 is realized while retaining 84% initial capacity over 1000 cycles. The study offers a new pathway to building next‐generation high‐energy aqueous rechargeable metal batteries.