Flexible All-Solid-State Asymmetric Supercapacitors Based on PPy-Decorated SrFeO 3-δ Perovskites on Carbon Cloth.

The defective structure and high oxygen vacancy concentration of SrFeO 3-δ perovskite enable fast ion-electron transport, but its low conductivity still hinders the high electrochemical performance. Herein, to enhance the conductivity of SrFeO 3-δ -based electrodes, polypyrrole-modified SrFeO 3-δ perovskite on carbon cloth (PPy@SFO@CC) has been successfully fabricated by electrodeposition of polypyrrole (PPy) on the surface of SFO@CC. The optimal PPy700@SFO@CC electrode exhibits a specific capacitance of 421 F g -1 at 1 A g -1 . It was found that the outside PPy layer not only accelerates the electron transport and ion diffusion but also creates more oxygen vacancies in SrFeO 3-δ , enhancing the charge storage performance significantly. Moreover, the NiCo 2 O 4 @CC//PPy700@SFO@CC device maintains a specific capacitance of 63.6% after 3000 cycles, which is ascribed to the weak adhesion forces between the active materials and carbon cloth. Finally, the all-solid-state flexible supercapacitor NiCo 2 O 4 @CC//PPy700@SFO@CC is constructed with PVA-KOH as the solid electrolyte, delivering an energy density of 16.9 W h kg -1 at a power density of 984 W kg -1 . The flexible supercapacitor retains 69% of its specific capacitance after 1000 bending and folding times, demonstrating a certain degree of foldability. The present study opens new avenues for perovskite oxide-based flexible all-solid-state supercapacitors.