Wearable and flexible graphene/Ti(OH)₄ fiber electrode with high volumetric capacitance and energy density

Fiber-based supercapacitors (FSCs) as flexible energy storage devices have attracted considerable attention for applications in portable and wearable electronics. However, the stacked micro-structure and poor faradaic activity of fiber electrodes assembled from two-dimensional materials severely impede dynamic transport and charge storage of electrolyte ions. Herein, we developed a novel graphene/Ti(OH)₄ (Gr/Ti(OH)₄) fiber electrode by in-situ chemical hydrolysis, self-assembly of graphene oxide/Ti(OH)₄ hybrid flakes, wet-spinning and subsequent reduction strategies. Benefiting from the strong covalent bonds and Van der Waals' force between Ti(OH)₄ and graphene flakes, the produced Gr/Ti(OH)₄ fiber electrode exhibited enhanced tensile strength of 483.60 MPa and elongation at break of 2.07 %, which are beyond most of the reported fiber based electrodes. Meanwhile, the assembled symmetric Gr/Ti(OH)₄-based FSC demonstrated high volumetric capacitance of 188.04 F cm⁻³ at 0.5 A cm⁻³, 98.6 % capacitance retention over 5000 cycles, and a high energy density of 15.39 mWh cm⁻³ at a power density of 1982.73 mW cm⁻³. Meanwhile, Gr/Ti(OH)₄ FSC also exhibited the excellent wearability and electrochemical stability, where 98 % capacitance retention of FSCs can be maintained after 1000 cycles bending at 90°. Thus, this work paves a new path for the design and fabrication of high-performance FSCs, demonstrating wide applications in wearable and portable electronics.