High-Performance flexible Quasi-Solid-State aqueous Nickel-Iron battery enabled by MOF-Derived N-Doped carbon hollow nanowall arrays

The development of portable, flexible and wearable electronic devices has accelerated ever-growing demand for high-performance power sources with high specific energy/power density, high-level safety, low cost, and highly flexible features. Herein, a flexible quasi-solid-state aqueous nickel–iron (QSSA Ni-Fe) battery with high energy and power densities is rationally developed using ultrathin Ni(OH)2 nanoflakes and porous ɑ-Fe2O3 nanorods conformally deposited on vertically aligned MOF-derived N-doped carbon hollow nanowalls supported by carbon textiles (NC/CTs) as the cathode (Ni(OH)2@NC/CTs) and anode (ɑ-Fe2O3@NC/CTs), respectively. The obtained flexible QSSA Ni-Fe battery delivers optimal electrochemical performance, including high energy density (155.4 Wh Kg−1), high power density (14.0 KW Kg−1) and excellent cycling stability (∼86.1 % retention after 10,000 cycles). Impressively, the flexible QSSA Ni-Fe battery delivers stable electrochemical performance even under different bending conditions. The excellent electrochemical properties may be attributed to the following reasons: (i) The ultrathin Ni(OH)2 nanoflakes and porous ɑ-Fe2O3 nanorods deposited on 2D hollow NC arrays possess a high porosity and large specific surface area; (ii) The 2D hollow NC arrays on flexible CTs not only increase the electrical conductivity, but also function as a scaffold to hold the active materials (such as Ni(OH)2 or ɑ-Fe2O3) and thus maintain the structural integrity of the composites. This work provides a novel approach to design and develop QSSA batteries with satisfactory electrochemical properties and excellent flexibility, and have greater potential for future flexible and wearable electronic devices.