From longan peel waste to energy storage: Porous activated carbon as a cathode matrix for advanced Li/Na-selenium batteries

This paper explores the potential of Longan peel waste (LPw) as a sustainable and cost-effective matrix for selenium-based cathodes in Li-Se and Na-Se batteries. Following activation, we created LP₂—a designation for the carbon precursor derived from LPw, activated at a 1:2 ratio of carbonized LPw to KOH. This nomenclature, where ‘LP' stands for ‘Longan peel' and ‘2′ reflects the optimization of this ratio, led to a hierarchical porous structure with an average pore size of 3.0307 ​nm and a significant BET surface area of 111.9386 ​m² ​g^-1. Selenium was incorporated into the LP₂ matrix using a simple melt diffusion technique, yielding the composite Se@LP₂. In Li-Se batteries, Se@LP₂ exhibited an initial discharge capacity of 1033.75 mAh g⁻¹ ​at 0.1C. At a 1C rate, the composite demonstrated a capacity retention of 301.14 mAh g⁻¹ after 550 cycles and 380.91 mAh g⁻¹ after 100 cycles. Moreover, for Na-Se batteries, the composite showcased a capacity retention of 347.18 mAh g⁻¹ after 100 cycles at 0.1C. These findings underscore LP₂'s potential as a viable and efficient matrix for selenium-based cathodes, revealing promising prospects for the advancement of highly efficient Li-Se and Na-Se batteries.