Superficial-defect engineered nickel/iron oxide nanocrystals enable high-efficient flexible fiber battery

The poor conductivity and sluggish kinetics of nickel/iron oxide in the electrochemical process significantly limits the efficient energy storage of conventional alkaline Ni/Fe battery. Herein, we report a defect engineering based superficially doping strategy to prepare manganese doped NiO and Fe2O3 nanostructured fibrous electrodes with exceptional electrochemical properties. Extensive experimental and theoretical investigations have been carried out, which indicates defect-rich shells are formed on the surface of the original metal oxide structures with improved carrier density, thus effectively boosting the capacity, rate performance and durability of electrodes. Finally, a flexible Ni/Fe fiber-shaped battery with gelled electrolyte is assembled, delivering an impressive volumetric energy density of 61.0 mW h cm(-3) and power density of 48.4 W cm(-3) with robust cycling stability of 91.2% capacity retention after 30,000 cycles, which is promising as the next-generation lightweight, wearable and rechargeable energy device.