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

Abstract

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.