Porous manganese dioxide nanosheets on modified graphite felt for cathodes in high-capacity flexible Zinc-MnO₂ batteries

Modified graphite felt (MGF) is a flexible substrate with many advantages and a simple one-step method involving HNO₃ is designed to activate graphite felt by increasing the amount of oxygen-containing functional groups and mesopores. Owing to the etching effect, excellent hydrophilicity beneficial to loading of α-MnO₂ is achieved to facilitate the formation of MnO₂/MGF. The MnO₂/MGF structure serves as the cathode in a flexible Zn//MnO₂ battery which also consists of a cross-linked polyacrylamide hydrogel as the electrolyte and separator and a Zn flake as the anode. The flexible Zn–MnO₂ battery has excellent energy storage behaviors and cycling durability such as a high areal capacity of 1.26 mA h cm⁻² at 4 mA cm⁻² as well as capacity retention of 99.8% over 1000 cycles. Furthermore, the battery provides a remarkable energy density of 1.82 mW h cm⁻² at a power density of 3.7 mW cm⁻². The modification strategy and materials have large potential in wearable and flexible devices.