Preparation of hard carbon from acid-treated locust wood as anode material for sodium-ion batteries

Currently, sodium-ion batteries (SIBs) are favored by scientific researchers because of their abundance, low cost, and high safety. Furthermore, hard carbon has a low-voltage plateau and a high sodium storage capacity when used as the anode material in SIBs. Given its affordability and variety of sources, biomass hard carbon has gained interest. However, the low initial Coulombic efficiency (ICE) of biomass hard carbon significantly hinders its development. Therefore, the waste biomass black locust wood was used to prepare hard carbon at different carbonization temperatures, and the carbonization temperature suitable for black locust wood was selected to modify the precursor with 6-M HCl to study the effect of acid treatment on the microstructure of carbon materials and their electrochemical properties. The experimental results proved that the HCl-pretreated hard carbon could increase the carbon layer spacing, increase more surface active sites that favor Na⁺ storage, and decrease the specific surface area. HC-1500 and HHC-1500 possessed a first cycle charge specific capacity of 319.6 mAh/g and 382.3 mAh/g, respectively, with an increase in the first-circle Coulombic efficiency (ICE) from 62 to 67% and also had a significant improvement in the cycling performance. Therefore, treating waste biomass with hydrochloric acid is a direct and effective method to modify hard carbon and improve its electrochemical performance.

Sodium-ion batteries (SIBs) are popular due to their low cost, safety, and abundant materials. Biomass-derived hard carbon, particularly from locust wood, shows promise as an anode material but suffers from low initial coulombic efficiency (ICE). Acid treatment with 6M HCl before carbonization improves its microstructure, increases sodium storage sites, and boosts ICE from 62% to 67%. The treated hard carbon (HC-1500 and HHC-1500) demonstrates enhanced charge capacity (319.6 mAh/g and 382.3 mAh/g) and better cycling performance, making this method effective for improving electrochemical properties.