Abstract
Lithium-oxygen batteries (LOBs) with remarkably higher energy density characteristics have become a critical focus of current battery research and development. However, the commercialization of LOBs faces several key challenges, including limited cycle life, excessive voltage hysteresis, and poor rate capability. Nickel-cobalt bimetallic catalysts have attracted considerable research interests due to their superior catalytic activity towards oxygen reduction reaction and oxygen evolution reaction. However, the cycling stability of nickel-cobalt bimetallic catalysts is overlooked to some extent.
Therefore, in this work, nickel-cobalt bimetallic catalysts with oxygen group elements including NiCo2O4 (NiCoO), NiCo2S4 (NiCoS), CoSe2-type solid solution NiCoSe (NiCoSe), and CoTe2/NiTe2 heterojunction (NiCoTe) are synthesized for LOBs. Among them, the NiCoSe featured a CoSe2-type solid solution microstructure, exhibits improved reversibility and superior cycling stability. It is found that the solid solution structure of NiCoSe cathode results in its electronic structure change and shows abundant electronic states near the Fermi level (Ef).
In addition, the excellent thermodynamic stability on both (100) and (111) planes, effectively delaying structural collapse of the NiCoSe cathode during cycling. Impressively, the LOBs with NiCoSe cathode deliver a cycle life exceeding 100 cycles at 0.02 mA cm−2 and 0.1 mAh cm−2, which is far superior to the other three cathodes.
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