Carbonization temperature dependent structural modifications of waste coffee grounds derived hard carbons and their electrochemical behaviors as anode materials for sodium ion batteries

This study explores the development and characterization of hard carbon anodes for sodium-ion batteries produced from waste coffee grounds, synthesized at both 1000 °C and 1500 °C. Importantly, this work highlights the potential of using biomass-derived hard carbons as sustainable and effective material for anode for sodium-ion batteries, contributing to the advancement of energy storage systems with increasing global demands for environmentally friendly and cost-effective technologies. The research focuses on the electrochemical performance of these hard carbons, examining how different carbonization temperatures impact their structural and electrochemical properties. Utilizing advanced analytical methods, the structural changes correlating with temperature increase were identified, including modifications in carbon atom arrangements, which significantly influence the electrochemical behaviors of the hard carbons. Our research specifically focuses on how the structural differences affect the division of capacity contribution from sloping region (above 0.1 V) and plateau regions (below 0.1 V). Electrochemical test results revealed that hard carbon with higher degree of order and reduced microstructural defects, demonstrated improved capacity values. At the same time, the highly ordered hard carbon exhibits drastic capacity loss upon increasing of current densities. The results from this study not only advance our understanding of hard carbons but also open pathways for the future exploration of hard carbons for additional improvements.