Integrating Conductivity, Captivity, and Immobility Ability into N/O Dual‐Doped Porous Carbon Nanocage Anchored with CNT as an Effective Se Host for Advanced K‐Se Battery

Abstract Potassium–selenium (K‐Se) batteries have attracted increasing attention for their potential as stationary energy storage systems due to their high theoretical energy density and low cost. The major challenges of these batteries are the low utilization of active selenium, sluggish kinetics, and the volume change during cycling. Herein, a N and O dual‐doped porous carbon nanocage anchored with carbon nanotubes (CNTs) (denoted as NO‐nanocage/CNT) is designed as a host for Se. This material combines multiple advantages, such as abundant N/O active sites and excellent electrical conductivity, to realize highly efficient immobilization of Se and polyselenide and fast redox kinetics. The hollow carbon skeleton, with abundant micro and mesoporous structures, shortens the diffusion distances between the ions/electrons and accommodates the volume expansion of the active materials. Density functional theory calculations further confirm that the NO‐nanocage/CNT exhibits strong chemical affinity to K₂Se, which is in agreement with the experimental results. The Se@NO‐nanocage/CNT cathode displays a remarkable reversible capacity (623 mAh g⁻¹ at 0.1 A g⁻¹) and an ultra‐long cycle life (274 mAh g⁻¹ after 3500 cycles at 1.0 A g⁻¹). The design presented in this paper offers a new approach for the design of multifunctional Se hosts for advanced alkali metal‐chalcogen batteries.