Almond Shell as a Microporous Carbon Source for Sustainable Cathodes in Lithium⁻Sulfur Batteries

A microporous carbon derived from biomass (almond shells) and activated with phosphoric acid was analysed as a cathodic matrix in Li⁻S batteries. By studying the parameters of the carbonization process of this biomass residue, certain conditions were determined to obtain a high surface area of carbon (967 m² g^-1) and high porosity (0.49 cm³ g^-1). This carbon was capable of accommodating up to 60% by weight of sulfur, infiltrated by the disulphide method. The C⁻S composite released an initial specific capacity of 915 mAh g^-1 in the Li⁻S cell at a current density of 100 mA g^-1 with a high retention capacity of 760 mAh g^-1 after 100 cycles and a coulombic efficiency close to 100%. The good performance of the composite was also observed under higher current rates (up to 1000 mA g^-1). The overall electrochemical behaviour of this microporous carbon acting as a sulfur host reinforces the possibility of using biomass residues as sustainable sources of materials for energy storage.