A one-dimensional channel self-standing MOF cathode for ultrahigh-energy-density flexible Ni–Zn batteries

The realization of high flexibility and high energy density for wearable energy storage devices places high demands on each electrode and electrolyte. For a single electrode, high loading, efficient ion channels, and good flexibility are critical. In this study, we construct one-dimensional (1D) channel self-standing Ni-MOF-74 grown on carbon nanotube fibers (Ni-MOF-74@CNTF) as a binder-free cathode of Ni–Zn batteries for the first time. Benefiting from the large surface area, regular 1D open channel structure and fast electron transfer, the cathode exhibits a large volume capacity and high rate performance. Combined with a Zn anode, an aqueous rechargeable Ni–Zn battery with a high discharge voltage of ∼1.75 V is assembled, which demonstrates a remarkable reversible capacity of 184.5 mA h cm−3 at a current density of 0.25 A cm−3. The flexible quasi-solid-state Ni-MOF-74//Zn battery achieves a maximum energy density of 186.28 mW h cm−3 and a maximum power density of 8.4 W cm−3. It also exhibits outstanding electrochemical ability and flexible performance, with negligible capacity attenuation under different bending angles. Our work provides an effective strategy for the production of novel self-supporting MOF-based electrode materials and is of great significance for promoting their application in wearable energy storage devices.