Amorphous Se Restrained by Biomass-Derived Defective Carbon for Stable Na–Se Batteries

Rechargeable sodium–selenium (Na–Se) batteries have attracted increasing attention due to their high energy density and the abundant resource of Na. However, their practical application is hindered by a short lifespan due to the active material dissolution, shuttling effect, and volume variation of the Se cathode. Herein, we report a facile strategy to significantly boost the cycling stability of the Se cathode by restrained amorphous Se into a N/O-doped defective carbon matrix derived from poplar-catkin (Se@NOPCC). Density functional theory calculations and experimental results elucidate that N/O active sites on the defective carbon enable a strong chemical affinity with the Se chain and NaSe2/Na2Se discharged products, which suppresses the shuttling effect and dissolution issues. In addition, the amorphous Se embedded in the hierarchically porous carbon relieves the strain and accommodates the huge volume variation during the sodiation/desodiation process. Consequently, the designed Se@NOPCC cathode exhibits a remarkable reversible capacity of 646 mAh g–1 at 0.05 A g–1 and a long cycling life with 83.8% capacity retention over 1600 cycles at 1.0 A g–1. This work offers a possibility for building stable Na–Se batteries and will also encourage more investigations on the combination of energy application and biomass materials.