High-yield humic acid-based hard carbons as promising anode materials for sodium-ion batteries

A low-cost and sustainable anode material is essential for the future commercialization of sodium-ion batteries (SIBs). Among all proposed anode materials for SIBs, hard carbons are considered to hold the most promise. However, high cost and low carbon yield of precursors limit its industrialization process. Here the synthesis of a biomass-derived hard carbon from leonardite humic acid (LHA) through a facile process was reported. The obtained hard carbons with an amazing high carbon yield of 60.73% were evaluated as anode for SIBs. The LHA-based hard carbons exhibit a promising anode performance with a sodium storage capacity of 345 mAh g−1, an initial coulombic efficiency up to 73% and superior cyclic stability. Combined with the facile synthesis process and abundant resource, the LHA-based hard carbons may hold a promising future as anode materials for SIBs.