Manipulating the morphology and the electronic structures of nickel-cobalt selenides@N-doped carbon for aqueous alkaline batteries

Morphology engineering and surface modification are efficient approaches to enhance the electrochemical performance of transition metal chalcogenides. In the present work, (Ni,Co)Se2@N-doped carbon with different morphologies derived from Prussian blue analogous were synthesized. The influence of chemical etching on the morphology, elec-tronic structure and electrochemical performance and activity of (Ni,Co)Se2@N-doped carbon were investigated. The results demonstrated that the chemical etching not only resulted in increased proportion of metal ions with low oxidation states, but also caused the reduction of the nickel and cobalt species on the surface. Therefore, better reversibility and enhanced reaction kinetics were observed in (Ni,Co)Se2@N-doped carbon nanocages despite that the resultant nanocubes showed higher specific capacity (432.1 C g- 1 at 0.5 mA cm-2). Moreover, an aqueous alkaline battery was assembled by integrating commercial activated carbon and (Ni,Co)Se2@N-doped carbon nanocubes as negative and positive electrode, respectively, which could reach a working voltage of 1.65 V and achieve an energy density of 28.2 W h kg-1 at 307 W kg-1 and remain 18.5 W h kg-1 at 3.07 kW kg-1. Our study on (Ni,Co)Se2@N-doped carbon provides helpful inspiration to design nickel-cobalt selenides with excellent electrochemical performance as active materials for aqueous alkaline batteries.

Automated summary

This study focuses on the synthesis of (Ni,Co)Se2@N-doped carbon materials with different morphologies using chemical etching method and investigates their morphology, electronic structure, and electrochemical performance. The results demonstrate that chemical etching can enhance the proportion of metal ions with low oxidation states and reduce the surface nickel and cobalt species, leading to improved reversibility and reaction kinetics. Moreover, assembling an alkaline battery with these materials as electrodes achieves high specific capacity and energy density.