Integrating selenium confinement in two-dimensional carbon matrix with Co catalysis for high-performance sodium-ion batteries

The energy storage of sodium-selenium (Na-Se) batteries is largely impeded by inferior reaction kinetics and polyselenides intermediates shuttling. Herein, we propose the synthesis of two-dimensional porous carbon materials with cobalt (Co) nanoparticles (C/Co) as selenium host via the carbonization of Zn/Co bimetallic organic frameworks (Zn/Co -MOF) for the first time. Density functional theory (DFT) calculations demonstrate that Co nanoparticles catalyst exhibits effective adsorption of polyselenide species, facilitating the conversion of long-chain polyselenides, and effectively reducing the energy barrier, thus promoting high kinetics in the electrochemistry of sodium-selenium batteries. And the uniform micro/mesoporous structure of the C/Co matrix provides efficient channels for ion diffusion and electron transfer. The Se/CCo cathode demonstrates superior performance, delivering a high initial capacity of 669.3 mAh g−1 and retaining a capacity of 410.9 mAh g−1 over 1000 cycles at 0.5 C. This excellent cycling stability and rate capability of the Se/CCo composite is attributed to the unique structure of 2D carbon matrix and effective catalysis of Co nanoparticles, thereby enabling higher utilization of active Se species. This work may provide important insights into the improvement of advanced materials for Na-Se batteries.