Hierarchical 3D Oxygenated Cobalt Vanadium Selenide Nanosheets as Advanced Electrode for Flexible Zinc–Cobalt and Zinc–Air Batteries

Abstract Highly flexible quasi solid‐state batteries are promising in next‐generation energy storage sectors due to their high energy density, power density, and low manufacturing cost. However, poor cycle life seriously limits their application in industrial sectors. Herein, a novel strategy is established to design the oxygenated cobalt vanadium selenide (O‐Co x V 1‐ x Se 2 ) nanostructures for high‐performance quasi solid‐state (QSS) zinc–cobalt batteries (ZCBs) and zinc–air batteries (ZABs). Density functional theory (DFT) calculation reveals that the doping effect of Co 2+ into O‐VSe 2 nanostructure could increase the density of states near the edge of the conduction band, demonstrating ultrafast electron transport kinetics. Most interestingly, the optimal O‐Co 0.33 V 0.67 Se 2 cathode‐based QSS‐ZCB exhibits an ultrahigh specific capacity of 422.7 mAh g −1 at a current density of 1 A g −1 , excellent energy density of 186.4 Wh kg −1 , tremendous power density of 5.65 kW kg −1 , and ultralong cycle life (86.9% capacity retention after 3000 cycles). Furthermore, O‐Co 0.33 V 0.67 Se 2 air‐cathode based QSS‐ZAB delivers a peak power density of 162 mW cm −2 and ultralong cycle life over 100 h. These experimental and theoretical studies indicate that the electrochemically induced, cobalt stabilizes the vanadium is essential to boost the energy storage properties and cycle life of both ZCBs and ZABs.