CuCo-Layered Double Hydroxide Nanosheet-Based Polyhedrons for Flexible Supercapacitor Cells

Herein, a flexible high-performance supercapacitor cell using nanostructured CuCo-layered double hydroxide (LDH) as power source electrode material is reported for the first time, where the CuCo-LDH hollow nanopolyhedrons are developed by tuning the Cu/Co ratio in the LDH host layers. Among various Cu/Co ratios, a solid-state symmetrical and flexible cell made with active Cu1.65Co1-LDH nanomaterial in [EMIM][BF4] electrolyte furnishes a specific capacity of 609.4 C g–1 and a specific capacitance of 244 F g–1 (0.603 F g–1 considering the total dry mass of the device) and exhibits a wide cell voltage of 2.5 V and is expected to be considered one of the best among the LDH family. It delivers high energy density (52.89 Wh kg–1) and power density (1215 W kg–1) values and tunable bending (0 to 180°) and twisting conditions. The flexible cell offers long-term stability (89% retention after 10000 charge–discharge cycles) and steady Coulombic efficiency at different bending angles. This work also offers valuable concepts for understanding the exceptional charge storage characteristics as accredited to high surface area furnishing abundant active sites, shortened ion diffusion length, and consequent faster ion switching, synergism between balanced Cu and Co ions, and major surface versus bulk charge contribution processes.