Nitrogen and Sulfur Co-doped Mesoporous Carbon for Sodium Ion Batteries

Enhanced sodium ion storage capacity of carbon anodes can be realized by heteroatom doping. Designing doped carbons with superior rate performance, high initial Coulombic efficiency (ICE), and excellent cyclability is still vital for practical application of sodium ion batteries. Herein, nitrogen and sulfur co-doped mesoporous carbons have been successfully synthesized from rhodanine using SBA-15 as the template, and the doped carbons exhibit ultrahigh ICE of 90.9%, show superior rate performance with a high capacity of 236 mA h g–1 tested at 10 A g–1, and maintain 88% of their initial capacity even after 5000 cycles in ether-based electrolyte. High nitrogen and sulfur co-doping level, interconnected mesoporous structure, and optimized electrolyte ensure rapid electron/ion transfer. The kinetics analysis indicates that ultrahigh capacitive contribution of 84.5% at 0.2 mV s–1 and 93.9% at 1 mV s–1 can be achieved. Ex situ XPS analysis indicates that heteroatom doping can introduce irreversible capacity, and the functional groups should be strictly controlled for boosting the electrochemical performance. These results open a promising avenue to realize advanced carbon anodes for sodium ion storage by doping with ether-based electrolyte.