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

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 (Co9S8@NC) catalyst with unique charge-deficient states is developed to promote the reaction kinetics of the I-/I+ electrode. The charge-deficient Co9S8@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 & Vert;I+/I-0/I- battery equipped with the Co9S8@NC catalyst can deliver a high energy density of 554 Wh kg(-1) and a stable cycle life of 5000 cycles at 30 degrees C. Moreover, at a subzero temperature of -30 degrees 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).