Electrochemical performance of CoSe 2 with mixed phases decorated with N-doped rGO in potassium-ion batteries.

Potassium-ion batteries (PIBs) have received much attention as next-generation energy storage systems because of their abundance, low cost, and slightly lower standard redox potential than lithium-ion batteries (LIBs). Nevertheless, they still face great challenges in the design of the best electrode materials for applications. Herein, we have successfully synthesized nano-sized CoSe ₂ encapsulated by N-doped reduced graphene oxide (denoted as CoSe ₂ @N-rGO) by a direct one-step hydrothermal method, including both orthorhombic and cubic CoSe ₂ phases. The CoSe ₂ @N-rGO anodes exhibit a high reversible capacity of 599.3 mA h g ^-1 at 0.05 A g ^-1 in the initial cycle, and in particular, they also exhibit a cycling stability of 421 mA h g ^-1 after 100 cycles at 0.2 A g ^-1 . Density functional theory (DFT) calculations show that CoSe ₂ with N-doped carbon can greatly accelerate electron transfer and enhance the rate performance. In addition, the intrinsic causes of the higher electrochemical performance of orthorhombic CoSe ₂ than that of cubic CoSe ₂ are also discussed.
Competing Interests: There are no conflicts to declare.
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