An effective strategy to prepare non-graphitic carbon with increased pseudo-graphitic content for sodium-ion battery anode with enhanced plateau capacity

The practical application of sodium-ion batteries is mainly hindered by relatively low energy density, which can be effectively overcome by increasing the pseudo-graphitic content in non-graphitic carbon (NGC) anodes. Herein, a simple and efficient strategy was reported to promote the growth of pseudo-graphitic domains in NGC thanks to the synergistic effect of pre-carbonization and NaOH etching using semi-coke as precursor. Based on pre-carbonization at 800 °C and NaOH etching with NaOH/carbon ratio of 0.5 at 600 °C, the resultant NGC (FC-800–0.5–600) exhibits a 13 % increase in percentage of pseudo-graphitic structure meanwhile 14 % decrease for graphite-like structure, but similar content of highly disordered structure compared with its counterpart. Notably, although similar in sloping capacity, FC-800–0.5–600 possesses much higher plateau capacity (<0.1 V) of 218.6 mAh g−1 than its counterpart (174.9 mAh g−1), which is attributed to the enhanced "interlayer intercalation" effect related with pseudo-graphitic structure. Thus, FC-800–0.5–600 can deliver an impressive reversible capacity of 326.8 mAh g−1 at 20 mA g−1, together with a considerable ICE of 84.7 %. This work proposed an effective strategy to increase pseudo-graphitic structure content in NGC, providing a rational guide for designing high-performance anodes in SIBs for practical use.