Pore structure manipulation‐enhanced sodium storage of calcium‐lignosulfonate‐based hard carbon

Abstract Sodium‐ion batteries (SIBs) have attracted a lot of attention owing to their low cost, as well as similar working mechanism and manufacturing technique to lithium‐ion batteries. However, the practical application of SIBs is severely hindered by limited electrode materials. Disordered carbons are reported to be promising as anode materials for SIBs. Here, for the first time, calcium lignosulfonate (LSCa), one papermaking waste, is explored as a novel low‐cost precursor for carbon materials of SIBs. The optimized LSCa‐derived carbon delivers a high reversible capacity of 317 mA h g −1 at 30 mA g −1 with ~60% plateau capacity, and it retains a capacity of 170 mA h g −1 even at 3000 mA g −1 . These achievements are ascribed to the larger d 002 values, smaller defects, and more closed pores, compared with the original sample from the direct carbonization of LSCa.