Facile Production\nof Defect Controllable Hard Carbon\nAnode Materials for Long-Term Sodium Storage

Sodium-ion batteries (SIBs), as low-cost energy storage\nalternatives\nto the lithium-ion ones, have attracted considerable attention. However,\nthe anode material of SIBs, i.e., hard carbon (HC), still suffers\na demand exceeding the supply. The current routes for HC production\nare either costly or the carbon sources are hard to collect in large\nscale. In this work, we proposed a facile and low-cost route for hard\ncarbon as a sodium battery anode with long cycling stability. By taking\nthe commercially available and cheap phenolic formaldehyde resin and\nmelamine formaldehyde resin as carbon sources, hard carbons with tunable\ndefect structures endow the batteries with a high initial Coulombic\nefficiency (ICE, >83%), high rate performance (>200 mAh/g at\n2 C),\nand long cycling stability at 2 C (capacity retention at 4000 cycles\n>80%). The commercially available low-cost carbon source and facile\npreparation method for high-performance HCs are ready for SIB industrialization.