Facile Production of Defect Controllable Hard Carbon Anode Materials for Long-Term Sodium Storage

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