Metal‐organic framework‐derived carbon‐cobalt oxysulfide nanocage heterostructure electrode for efficient hybrid supercapacitors

Summary Construction of hybrid supercapacitors (HSCs) with defect engineered electrodes derived from single metal‐organic frameworks (zeolitic imidazolate frameworks, ZIF‐67) via control of the thermal influences showed unique structural features and rich electrochemical properties. Designing the three‐dimensional Co oxysulfide nanograins with carbon frame (CoOS‐C)‐based positive electrode surfaces through sulfidation with tunable defect states along with N‐ and S‐doping states improved the electrical energy storage; further, the possibility of having a carbon‐based skeleton surface influenced the effective rate capability during the charge‐discharge process. This unique nanostructural feature with encapsulation of porous N‐ and S‐doped graphitic carbon enabled improved rate performance by enhancing the stability of the electrode material and shortening the ion‐diffusion paths by the synergistic effect. Owing to the tunable defect functionality, the CoOS‐C based electrode exhibited a high storage capacity of 708.8 C g −1 at 1 A g −1 and an excellent rate capability with long‐term cyclic stability, with more than 93% capacity retention after 3000 cycles. Furthermore, the fabricated HSCs operated within a wide potential window of 1 to 1.6 V, which allowed excellent rate capability with a high‐energy density of 31.7 W h kg −1 at a specific power density of 800 W kg −1 with long‐term cyclic stability up to 10 000 cycles.