Hard Carbon Anodes for Na-Ion Batteries

Based on the structural properties, especially the ability to be graphitized, carbon materials can be divided into three major types: hard carbon, soft carbon, and graphite. Until now, hard carbons have been considered to be the most promising anode materials for Na-ion batteries (NIBs) at the commercial level because of their low cost as well as great electrochemical capacity and stability. This chapter introduces the structures and their corresponding characterizations of hard carbon anode materials for NIBs. Although many research groups have made remarkable achievements in hard carbons for NIBs, the sodium storage mechanisms of carbon anode materials are still under debate. Given that hard carbons have different disordered structures, pore structures and heteroatoms, and so on, it is not surprising that sodium storage behaviors at the sloping or plateau areas of the galvanostatic charge–discharge curves are difficult to interpret