From atom to device: an integrated Se cathode with atomic Co sites and dual-carbon confinement for ultrafast Li–Se batteries

Abstract

Lithium–selenium (Li–Se) batteries are attractive for high-energy-density storage because of the high volumetric capacity and relatively high electrical conductivity of selenium. However, their practical application is still hindered by severe volume expansion, limited active-material utilization, and sluggish redox kinetics. Herein, we report an integrated Se cathode (Se/Co-NC@CNFs) based on a dual-carbon confinement strategy. In this architecture, atomically dispersed Co sites are anchored on porous N-doped carbon cages (Co-NC), which are further embedded in conductive carbon nanofibers (CNFs). This configuration enables high selenium loading while providing a multifunctional framework in which the Co–N₄ sites act as electrocatalytically active centers to accelerate the conversion between Se and Li₂Se. Meanwhile, the dual-carbon confinement from the Co-NC cages and the CNFs network effectively alleviates volume changes and improves selenium retention during cycling. More importantly, the binder-free and current-collector-free electrode design greatly increases the active-material fraction, resulting in a markedly improved capacity based on the total cathode mass (347 mAh g⁻¹ versus 22 mAh g⁻¹ for the conventional Se/NC cathode). Consequently, the Se/Co-NC@CNFs cathode delivers a high reversible capacity of 520 mAh g⁻¹ at 50 A g⁻¹ (≈74C) and retains 514 mAh g⁻¹ after 3500 cycles at 15 A g⁻¹. This work provides a rational design strategy for high-performance, Li–Se batteries through atomic-scale catalysis and integrated electrode engineering.