g-C3N4-coated MnO2 hollow nanorod cathode for stable aqueous Zn-ion batteries

Aqueous zinc-ion batteries are attracting considerable attention because of their high safety compared with conventional lithium-ion batteries. Manganese-based materials have been widely developed for zinc-ion batteries cathode owning to their low cost, high security and simple preparation. However, the severe volume expansion and poor stability during charging and discharging limit the further development of manganese-based cathodes. Herein, superior α-MnO2@g-C3N4 was successfully prepared for stable zinc-ion batteries (ZIBs) cathode by introducing g-C3N4 nanosheets. Compared with pure α-MnO2, α-MnO2@g-C3N4 has a specific capacity of 298 mAh·g–1 at 0.1 A·g–1. Even at 1 A·g–1, the α-MnO2@g-C3N4 still retains 100 mAh·g–1 (83.4% retention after 5000 cycles), implying its excellent cycling stability. The α-MnO2@g-C3N4-based cathode has the highest energy density (563 Wh·kg–1) and power energy density (2170 W·kg–1). This work provides new avenues for the development of a wider range of cathode materials for ZIBs.