Pitch-derived amorphous carbon as high performance anode for sodium-ion batteries

Carbonaceous materials hold the most promising application among all anode materials for sodium-ion batteries (SIBs) because of the high storage capacity and good cycling stability. However, the high cost and the low initial Coulombic efficiency limit their further commercialization. Herein, an amorphous carbon material was fabricated through direct pyrolysis of low-cost pitch and phenolic resin at heat treatment temperatures between 1200 and 1600 °C. The electrochemical performances of the amorphous carbon were systematically investigated in SIBs with inexpensive Al foil as current collector and environmentally benign aqueous sodium alginate as binder. By optimizing the carbonization temperature and precursor, we achieved an initial Coulombic efficiency of 88% - the highest reported so far for carbon-based anodes in SIBs with a high reversible capacity of 284 mA h g−1 and excellent cycling performance. It was found that both the carbonization temperature and the mass ratio of pitch to phenolic resin have significant impact on the local structure of amorphous carbon, which leads to various electrochemical behaviors. When coupled with an air-stable O3-Na0.9[Cu0.22Fe0.30Mn0.48]O2 cathode, the full cell shows excellent electrochemical performance with an initial Coulombic efficiency of 80%, a good cycling stability and an energy density of 195 Wh/kg. This contribution provides a new approach for the development of low-cost sodium-ion batteries.