Biomass-Derived Hard Carbon Materials for High-Performance Sodium-Ion Battery

Using biomass-derived hard carbon materials as anode materials for sodium-ion batteries has facilitated resource recycling and brought significant economic benefits. However, the main obstacles to the large-scale application of these materials are the low Coulombic efficiency and high irreversible capacity of hard carbon materials. This study used waste moso bamboo as a carbon source to prepare and pre-oxidize hard carbon through a stepped temperature sintering process. The introduction of oxygen atoms into the carbon layers has been shown to increase the spacing between the carbon layers, which facilitates the insertion of sodium-ions into them. Moreover, the presence of oxygen-containing groups increases the number of edge and vacancy defects in the carbon skeleton, thereby enhancing the actual capacity of the material. Studies have indicated that different pre-oxidation times have varying impacts on the electrochemical properties of hard carbon materials. This study used discarded moso bamboo as the raw material, and the optimal pre-oxidation duration of bamboo-based hard carbon was determined to be 4.5 h through a series of comparative experiments. A high-performance biomass-derived hard carbon material was prepared via a stepwise sintering process. It exhibited a specific capacity of 301.4 mAh·g−1 at 0.1 C and a first-cycle Coulombic efficiency of 87%.