Interface engineered and surface modulated electrode materials for ultrahigh-energy-density wearable NiCo//Fe batteries

The rational design and construction of high-performance fiber-shaped NiCo//Fe batteries is of great importance for the development of portable and wearable electronics. Electrode materials with all hierarchical core-shell heterostructures have great potential for use in high-performance NiCo//Fe batteries as a result of their good conductivity, high mass loading, and short ion-diffusion paths. Herein is proposed a novel freestanding core-shell positive and negative electrode materials developed by depositing NiCoP nanosheets on nanoflake arrays (NiCoP@NiCoP NFAs) and Fe2O3 nanoneedles on TiN nanowire arrays (TiN@Fe2O3 NWAs) directly grown on carbon nanotube fibers (CNTFs). The fabricated NiCoP@NiCoP NFAs/CNTF was validated to be an ultrahigh capacity cathode (1.07 mAh cm(-2) at 2 mA cm(-2)), matching well with the similarly constructed TiN@Fe2O3 NWAs/CNTF anode (0.92 mAh cm(-2) at 2 mA cm(-2)). These electrodes were successfully developed into a high-performance NiCo//Fe battery that exhibited an extraordinary capacity of 0.77 mAh cm(-2) and a remarkable energy density of 265.2 mWh cm(-3). The flexible battery demonstrated an excellent cycling lifespan with 89.4% capacity retention after 4000 cycles. This pioneering study describes a powerful strategy for the rational construction of high-performance electrode materials with hierarchical core-shell heterostructures and constitutes a novel approach for the development of new-generation wearable aqueous rechargeable batteries.