Constructing a mesoporous carbon nanobowls embedded with ultrafine CoSe₂ Nanocrystals for High-Performance potassium ion battery electrode

In the quest for advanced electrode materials for potassium ion batteries (KIBs), an innovative anode featuring ultrafine CoSe₂ nanocrystals embedded within mesoporous carbon nanobowls (CoSe₂@MCNBs) is presented herein. Diverging from conventional hollow carbon nanospheres, the distinctive bowl structure is crafted to enhance the structural integrity and volumetric energy density of the electrodes. CoSe₂@MCNBs synthesized using an iterative drop and dry method followed by selenization exhibit well-preserved morphology with a shell thickness of 20 nm. The successful integration of ultrafine CoSe₂ nanocrystals into MCNBs imparts the nanobowls with the benefits of conventional hollow carbon-based composites, including abundant ion storage sites and high electrical conductivity. Simultaneously, the bowl structure boasts a higher packing density than the conventional hollow mesoporous carbon sphere (HMCS) structure, significantly augmenting the volumetric energy density of the fabricated electrode. Capitalizing on these advantages, the CoSe₂@MCNB electrode displays exceptional cycling stability, achieving a reversible capacity of 523 mA h g⁻¹ after 500 cycles at 0.5 A/g and an impressive rate capacity of 247 mA h g⁻¹ at 2.0 A/g. This study demonstrates the strong potential of CoSe₂@MCNB as an electrode material for the next generation of KIBs.