MOF-Derived CoSe2@N-Doped Carbon Matrix Confined in Hollow Mesoporous Carbon Nanospheres as High-Performance Anodes for Potassium-Ion Batteries

Abstract

Highlights

A novel vacuum-assisted strategy is proposed to form N-doped carbon-encapsulated CoSe₂ nanocrystals within hollow mesoporous carbon nanospheres (CoSe₂@NC/HMCS) via a solid-state reaction.

The “dual confinement” by both the N-doped carbon matrix derived from 2-methylimidazole and the small-sized pores of the hollow mesoporous carbon nanospheres can effectively prevent the overgrowth of CoSe₂ nanocrystals.

CoSe₂@NC/HMCS exhibits an excellent electrochemical performance as the anode material for KIBs in terms of cycling stability and rate capability.

In this work, a novel vacuum-assisted strategy is proposed to homogenously form Metal–organic frameworks within hollow mesoporous carbon nanospheres (HMCSs) via a solid-state reaction. The method is applied to synthesize an ultrafine CoSe₂ nanocrystal@N-doped carbon matrix confined within HMCSs (denoted as CoSe₂@NC/HMCS) for use as advanced anodes in high-performance potassium-ion batteries (KIBs). The approach involves a solvent-free thermal treatment to form a Co-based zeolitic imidazolate framework (ZIF-67) within the HMCS templates under vacuum conditions and the subsequent selenization. Thermal treatment under vacuum facilitates the infiltration of the cobalt precursor and organic linker into the HMCS and simultaneously transforms them into stable ZIF-67 particles without any solvents. During the subsequent selenization process, the “dual confinement system”, composed of both the N-doped carbon matrix derived from the organic linker and the small-sized pores of HMCS, can effectively suppress the overgrowth of CoSe₂ nanocrystals. Thus, the resulting uniquely structured composite exhibits a stable cycling performance (442 mAh g⁻¹ at 0.1 A g⁻¹ after 120 cycles) and excellent rate capability (263 mAh g⁻¹ at 2.0 A g⁻¹) as the anode material for KIBs.