Construction and electrochemical mechanism investigation of hierarchical core—shell like composite as high performance anode for potassium ion batteries

Potassium-ion batteries (PIBs) are promising candidates for next-generation energy storage devices due to the earth abundance of potassium, low cost, and stable redox potentials. However, the lack of promising high-performance electrode materials for the intercalation/deintercalation of large potassium ions is a major challenge up to date. Herein, we report a novel uniform nickel selenide nanoparticles encapsulated in nitrogen-doped carbon (defined as “NiSe@NC”) as an anode for PIBs, which exhibits superior rate performance and cyclic stability. Benefiting from the unique hierarchical core—shell like nanostructure, the intrinsic properties of metal—selenium bonds, synergetic effect of different components, and a remarkable pseudocapacitance effect, the anode exhibits a very high reversible capacity of 438 mA·h·g−1 at 50 mA·g−1, an excellent rate capability, and remarkable cycling performance over 2,000 cycles. The electrochemical mechanism were investigated by the in-situ X-ray diffraction, ex-situ high-resolution transmission electron microscopy, selected area electron diffraction, and first principle calculations. In addition, NiSe@NC anode also shows high reversible capacity of 512 mA·h·g−1 at 100 mA·g−1 with 84% initial Coulombic efficiency, remarkable rate performance, and excellent cycling life for sodium ion batteries. We believe the proposed simple approach will pave a new way to synthesize suitable anode materials for secondary ion batteries.