Physico-Chemical and Electrochemical Analysis of Hard-Carbon From Licorice Root Bio-Waste as Anode for Sodium Ion Batteries

Sodium-ion batteries are gaining momentum, and to accelerate their commercial viability, the development of cost-effective and environmentally sustainable materials is crucial. Although hard carbons have been already established as the anodes of choice, several controversies still exist regarding the storage mechanism and interfacial properties during cycling. Here, we present a comprehensive study of a novel hard carbon from licorice root bio-waste by coupling a wide array of physico-chemical techniques, to gain insights into the sodium storage behavior and interfacial properties. Analytical techniques like potentiostatic and galvanostatic intermittent titration were used to assess solid-state sodium-ion diffusion, while ex situ small-angle X-ray scattering and electrochemical impedance spectroscopy modeled with transmission line enabled the monitoring of pore-filling storage evolution during cycling, as well as SEI formation. Staircase potentiostatic electrochemical impedance spectroscopy, and relaxation times analysis was used to further investigate interfacial evolution and charge-transfer kinetics within the initial cycles. While each of these techniques has been previously employed in the study of hard carbons, their combined application to a single material remains relatively uncommon; this work aims at providing a comprehensive and integrated perspective on the electrochemical behavior of licorice-derived hard carbon, highlighting its potential as a sustainable anode material for next-generation sodium-ion batteries.