Hydroxyl−functionalized polythiophene−coated CoNi−SeS/hollow carbon sphere electrodes for quasi−solid−state supercapacitors

Supercapacitors are a new class of energy storage devices with long cycle life, good reversibility, stability and safety. A (Poly (3,4-propylenedioxythiophene) − OH/CoNi−SeS @Hollow carbon sphere) PProDOT−OH/CoNi−SeS @HCS composite material is synthesized via a sulfurization/selenization ion exchange method and in−situ oxidation , which exhibits excellent electrochemical performance and a heterogeneous structure with multi-phase interfaces. The material's mass specific capacity is as high as 775.1C g −1 at 1 A g −1 . Even if it is increased to 20 A g −1 , it can still maintain 80.4 % of the capacitance. By combining the designed polyvinyl alcohol (PVA)/potassium hydroxide (KOH) hydrogel electrolyte, a conformal interface was formed, which combines both high conductivity and electrochemical stability. After assembling into a quasi-solid-state AC//PVA/KOH//PProDOT−OH/CoNi−SeS@HCS device, when the energy density is as high as 84.8 Wh kg −1 , the power density is 8000 W kg −1 . The subsequent 20,000 cycle stability test can still prove the excellence of the device, with the Coulombic efficiency as high as 98.81 % and the capacitance retention rate as high as 82.85 %. The better capacitance performance is achieved due to the synergistic effect of the conductive polymer, the hollow structure, the modified electronic structure and the multi-component system.