Heterogeneous Engineering and Carbon Confinement Strategy to Synergistically Boost the Sodium Storage Performance of Transition Metal Selenides

Abstract

Transition metal selenides (TMSs) are considered as an ideal anode material for sodium-ion batteries (SIBs) owing to their low cost and high theoretical capacity. However, their practical application has been limited by many factors such as poor electronic conductivity, slow reaction kinetics and severe agglomeration during electrochemical reactions. Herein, the dual-carbon-confined CoSe2/FeSe2@NC@C nanocubes with heterogeneous structure are synthesized using ZIF-67 as the template by ion exchange, resorcin-formaldehyde (RF) coating, and subsequent in situ carbonization and selenidation. The N-doped porous carbon promotes rapid electrolyte penetration and minimises clumping of active materials during charging and discharging, while the RF-derived carbon framework reduces the cycling stress and maintains the integrity of the material structure. More importantly, the electric field at the heterogeneous interface drives electron redistribution, optimizing the electronic structure and enhancing the reaction kinetics of the anode material. As a result, the nanocubes of CoSe2/FeSe2@NC@C exhibits superior sodium storage performance, delivering a high discharge capacity of 512.6 mA h g-1 at 0.5 A g-1 after 150 cycles and giving a discharge capacity of 298.2 mA h g-1 at 10 A g-1 with a CE close to 100.0% even after 1,000 cycles. This study proposes a viable method to synthesize high-performance anodes for SIBs by a synergetic effect of heterogeneous interfacial engineering and a carbon confinement strategy.

Keywords: Sodium-ion batteries, Transition metal selenides, ZIF-67, Nanocubes, Heterogeneous interface, Carbon confinement