A Facile Method to Transform Pickled Olive Wastes Into Sulfur-Doped Carbon for Sodium-Ion Battery Electrode

This work provides a novel, low-cost, and effective method to prepare disordered carbon materials for advanced sodium-ion batteries using biomass. A large amount of olive stone waste is yearly produced in the world, and it could be re-used for fine applications other than fuel for heat production. After treatment with sulfuric acid solution and carbonization process, wastes of olive stone are efficiently transformed into optimized carbon electrode material. XRD, XRF and XPS, electron microscopy, and physical gas adsorption are used for the compositional, microstructural, and textural characterization of the carbons. During the synthesis, impurities are removed, C-S links are formed and micropores pores are created. Sulfuric acid acts like S-dopant. The latent pores, or pores closed to nitrogen, can be found using CO₂ adsorption, and are very suitable for accommodation for sodium. The results reveal that the reversible capacity is raised from ca. 200 mAh g^-1 to ca. 250 mAh g^-1 for the carbon obtained through treatment with sulfuric acid. The improved electrochemistry is the result of the s-doping and the porosity.