Development of Inverse-Opal-Structured Charge-Deficient Co 9 S 8 @nitrogen-Doped-Carbon to Catalytically Enable High Energy and High Power for the Two-Electron Transfer I + /I - Electrode.

The iodine (I) electrode involving two-electron transfer chemistry by converting between I + and I - , has the potential to deliver theoretically doubled capacity and higher working voltage platforms, thus achieving higher energy density. However, owing to the slow kinetics of the cascade two-electron transfer reactions, the system suffers from large overpotentials and low power density, especially at high working currents and low temperatures. Here, an inverse-opal-structured cobalt sulfide@nitrogen-doped-carbon (Co 9 S 8 @NC) catalyst with unique charge-deficient states is developed to promote the reaction kinetics of the I - /I + electrode. The charge-deficient Co 9 S 8 @NC catalyst not only enables strong physicochemical adsorption with the iodine species but also significantly reduces the activation energy and interfacial charge transfer resistance of the cascade I + /I 0 /I - conversion reaction. Consequently, the prototypical Zn‖I + /I 0 /I - battery equipped with the Co 9 S 8 @NC catalyst can deliver a high energy density of 554 Wh kg -1 and a stable cycle life of 5000 cycles at 30 °C. Moreover, at a subzero temperature of -30 °C, the battery can exhibit enhanced kinetics and a high power density of 1514 W kg -1 , high energy density of 485 Wh kg -1 .