MgO‐Template Synthesis of Extremely High Capacity Hard Carbon for Na‐Ion Battery

Abstract Extremely high capacity hard carbon for Na‐ion battery, delivering 478 mAh g −1 , is successfully synthesized by heating a freeze‐dried mixture of magnesium gluconate and glucose by a MgO‐template technique. Influences of synthetic conditions and nano‐structures on electrochemical Na storage properties in the hard carbon are systematically studied to maximize the reversible capacity. Nano‐sized MgO particles are formed in a carbon matrix prepared by pre‐treatment of the mixture at 600 °C. Through acid leaching of MgO and carbonization at 1500 °C, resultant hard carbon demonstrates an extraordinarily large reversible capacity of 478 mAh g −1 with a high Coulombic efficiency of 88 % at the first cycle.