Macroporous, Freestanding Birnessite H_0.08MnO₂·0.7H₂O Nanobelts/Carbon Nanotube Membranes for Wearable Zinc-Ion Batteries with Superior Rate Capability and Cyclability

Rechargeable aqueous zinc-ion batteries (ZIBs) are regarded as an ideal choice for next-generation energy-storage devices. Nevertheless, the ZIB performance is still far from satisfactory due to the lack of suitable cathode materials. In this work, we demonstrated excellent zinc-ion-storage behavior in proton-type birnessite H0.08MnO2·0.7H2O nanobelts for the first time using a well-designed H0.08MnO2·0.7H2O/MWCNT composite membrane. Interestingly, our H0.08MnO2·0.7H2O nanobelts with a very high aspect ratio (∼30) facilitate the formation of abundant macropores of 0.5–5.0 μm size inside the as-constructed membrane, which provides an effective pathway for liquid electrolyte penetration during the long-term charge/discharge cycling. The resultant H0.08MnO2·0.7H2O/MWCNT composite membrane delivers a high Zn2+ diffusion coefficient of ∼8.18 × 10–14 cm2 s–1, excellent rate capability, and long-term cyclability over 1000 cycles at 3.0 A g–1. Our study not only reveals H0.08MnO2·0.7H2O as a robust cathode material for aqueous zinc-ion batteries but also demonstrates a macropore-assisted binder-free strategy to realize next-generation energy-storage devices from layered nanostructures with a high aspect ratio.