Development of Inverse‐Opal‐Structured Charge‐Deficient Co9S8@nitrogen‐Doped‐Carbon to Catalytically Enable High Energy and High Power for the Two‐Electron Transfer I+/I− Electrode

Abstract 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 .