Molten salt-assisted microporous biochar derived from poplar sawdust as an efficient cathode matrix for Li-Se battery applications

This study focuses on the employment of molten salts (ZnCl ₂-KCl-NaCl and K ₂CO ₃-Na ₂CO ₃-Li ₂CO ₃) as alternative activating agents to prepare porous biochars, which serve as efficient cathode matrices for Li-Se battery applications. Poplar sawdust was employed as the biomass feedstock, mixed with molten salts in a 1:5 mass ratio, and then pyrolyzed at a low temperature of 500 ℃ to obtain PB-Cl and PB-Carb, respectively. The obtained porous biochar samples were investigated, and processed for selenium (Se) loading using the melt-diffusion technique, resulting in composites named Se@PB-Cl and Se@PB-Carb, respectively. The composite Se@PB-Cl, with a BET surface area of 787.11 m ² g ⁻¹ and a t-plot micropores area of 691.65 m ² g ⁻¹, displayed a Se loading of 41.86 % and exhibited enhanced electrochemical performance. At 0.5 C, Se@PB-Cl after 100 cycles delivered a specific capacity of 617.03 mAh g ⁻¹. After 500 cycles, at 1 C a specific capacity of 505.9 mAh g ⁻¹ was observed. Moreover, the specific capacity of Se@PB-Carb was found to be 339.74 mAh g ⁻¹ at 0.5 C after 100 cycles, and 235.97 mAh g ⁻¹ at 1 C after 500 cycles. These findings highlight the potential of molten salt-assisted porous biochar obtained from poplar sawdust, as a cost-effective precursor for selenium-based cathodes.