The chain-mail Co@C electrocatalyst accelerating one-step solid-phase redox for advanced Li-Se batteries

Recently, Se cathodes have caught growing attention owing to their higher electronic conductivity, better compatibility with the carbonate electrolyte and comparable theoretical volumetric capacity to S cathodes. However, large volume variation, shuttle effect and sluggish redox kinetics have hindered the development of Li-Se batteries. Herein, we report chain-mail Co@C nanoparticles (Co@C NPs) embedded in macro-meso-microporous carbon nanofibers (CPCFs) with the characteristics of generalized Murray's law as a flexible Se host for advanced Li-Se batteries. The chain-mail Co@C structure protects Co from both active species and electrolyte, and then strengthens the adsorption-catalytic functions for active Se and Li₂Se, thus improving the one-step solid-phase redox. In addition, the hierarchical porous structure enhances mass transfer and relieves volume expansion. Accordingly, the Se@CPCFs cathode demonstrates a high capacity of ∼500 mA h g⁻¹ at 0.2C (1C = 675 mA g⁻¹) after 500 cycles and exhibits high-capacity retention of 97.4%, 97.6%, and 99.1% between 1 and 100, 100 and 300, and 300 and 500 cycles. An excellent rate capability at 10C with a reversible specific capacity of 438 mA h g⁻¹ is also realized. This work pioneered the utilization of chain-mail metal NPs as electrocatalysts to accelerate the solid-phase redox kinetics of Se cathodes for advanced Li-Se batteries.