Disordered carbon anodes for Na-ion batteries-quo vadis?

Na-ion batteries (NIBs) are gradually attracting much attention as an alternative to lead-acid batteries and supplement to Li-ion batteries (LIBs) owing to the abundant Na resources and excellent cost-effectiveness. Since the most commonly used graphite as an anode material in LIBs cannot be inherently used in NIBs, tremendous efforts have been made to advance the fundamental understanding and design of suitable anode materials for NIBs, including the improvement of Na storage capacity and the study on Na storage mechanisms. According to all these studies, disordered carbons are now the most promising anode candidates for NIBs. In this review, we discuss the current challenges and remaining problems to be solved in the area of disordered carbon anode materials for NIBs and provide future insights and research directions.