Mesoporous soft carbon as an anode material for sodium ion batteries with superior rate and cycling performance

Mesoporous soft carbon (MSC) was prepared from mesophase pitch using nano-CaCO3 as the template. The crystalline structure of soft carbon consists of a disordered region with a large interlayer distance benefitting sodium ion insertion/extraction and a graphitic region with good electrical conductivity favoring high rate performance. Additionally, the mesoporous structure not only shortens the path of ion diffusion but also facilitates the penetration of non-aqueous electrolytes, which can further enhance the electrochemical performance of MSC. Benefiting from its unique microstructure, the MSC delivers a reversible capacity of 331 mA h g(-1) at 30 mA g(-1), and retains a capacity of 103 mA h g(-1) at 500 mA g(-1) after 3000 cycles, indicating its excellent rate capability and cycling performance. Therefore, soft carbon with appropriate structure is expected to be another choice for anode materials of sodium ion batteries.