Hard carbon derived for lignin with robust and low-potential sodium ion storage

Hard carbon as the anode materials is the key for the development of sodium ion batteries (SIBs). However, low initial Coulomb efficiency (ICE) and specific capacity still hinder the development of hard carbon materials. Herein, hard carbon materials derived from lignin were prepared by controlling carbonization temperature, and the resulting hard carbon were used in SIBs. The storage mechanism of SIBs was discussed. In addition, the effect of carbonization temperature on the structure and chemical performance of hard carbon was investigated. As a result of its optimized microstructure, such as lower specific surface area, larger space of the interlayers and fewer defects, hard carbon from lignin carbonized at 1600 ℃ (LDHC-1600) exhibits ICE of 81.2 %, and reversible discharge capacity of 303 mA h g−1, and the ratio of low potential plateau to total capacity is 74.75 % (226.5 mA h g−1). The mechanism revealed that sodium ions are adsorbed in the slope region and the intercalation and filling mechanism in the plateau region are also verified. This study provides a type of biomass carbon anode material from lignin for application of SIBs.