Designing porous biochar from wheat straw by eutectic molten salt pyrolysis for high-performance Li-Se battery systems

The synthesis of an economically viable and sustainable porous carbon as a functioning electrode for lithium-selenium (Li-Se) battery systems is still a challenge. This study investigates the potential of employing waste wheat straw for synthesizing porous biochar activated by ZnCl₂-NaCl-KCl and MgCl₂-KCl-NaCl salt mixtures for Li-Se batteries. The synthesized WSB-Zn porous biochar exhibited a surface area of 417.54 m² g⁻¹ and a 2.05 nm pore diameter. The composites were synthesized via melt-diffusion technique and analyzed. Cycle stability tests (100 cycles) demonstrate that the Se@WSB-Zn composite, with 42.8 % Se loading, exhibited an admirable specific capacity of 593.43 mAh g⁻¹ at 0.5 C. It further showed a reversible capacity of 497.50 mAh g⁻¹ at 1 C even after 300 cycles and a rate performance of 373.61 mAh g⁻¹ at 2.5C. The material activated with magnesium salt (MgCl₂-KCl-NaCl), named WSB-Mg, resulted in the Se@WSB-Mg composite which consisted of 33.6 % Se and sustained cycling stability with a specific capacity of 356.73 mAh g⁻¹ after 300 cycles. This work provides an insight into the perspective of incorporating wheat straw-derived porous carbon structures achieved by molten salts into Li-Se batteries, offering an economical and eco-friendly approach for the synthesis of advanced selenium-based composites as cathodes.