Rational design and construction of iron oxide and titanium carbide MXene hierarchical structure with promoted energy storage properties for flexible battery

Aqueous rechargeable Ni/Fe batteries are appropriate energy storage devices for portable and wearable electronics due to their outstanding safety and cost-effectiveness. However, their energy storage properties are limited by the sluggish kinetics of iron-based anodes. Herein, we design and construct a high-performance iron-based material with a hierarchical structure developed by electrodepositing iron oxide (Fe2O3) nanosheets on titanium carbide (Ti3C2Tx) MXene nanoplates modified carbon fiber (3D-MXene/Fe2O3). Taking advantage of the interaction between Fe2O3 and the terminal functional groups on Ti3C2Tx MXene, such a hierarchical structure offers improved conductivity, enhanced ion-diffusion paths, and high electrochemical stability. The fabricated 3D-MXene/Fe2O3 anode delivers a high volumetric specific capacity of 38.2 mAh cm-3, and improved capacity retention. After being coupled with NiCoO cathode, the fibrous Ni/Fe battery shows a maximum volumetric specific capacity of 35.1 mAh cm-3 and an extraordinary energy density of 56.2 mWh cm-3. Meanwhile, the as-prepared Ni/Fe battery confirms good cycling durability (92.9% for 12,500 cycles), and mechanical flexibility also verifies the potential practical application of our device. Thus, this study can provide a powerful route toward high-performance anodes for next-generation wearable energy storage devices.