Facile synthesis of high quality hard carbon anode from Eucalyptus wood for sodium-ion batteries

Hard carbon is generally considered to be an attractive disordered carbon anodes for Na-ion batteries (NIBs). Herein, a type of Eucalyptus wood-derived hard carbon (HC) material is reported for efficient Na storage, which holds several merits such as high initial Columbic efficiency (89.1%), moderate carbon yield (21%) and satisfying electrochemical performance simultaneously. Natural holey structure inherited from wood lead to hierarchical porous morphology of the resulting HC. The structural and morphological properties have been characterized by XRD, XPS, BET, SEM, TEM and Raman spectroscopy. Small angle X-ray scattering analysis (SAXS) is used to obtain the closed pore information. The optimal HC was got by changing pyrolysis temperature to regulate the open and closed pores. It has a high specific capacity of about 300 mAh g−1 and a good capacity retention of 93% after 200 cycles at 0.1 A g−1 in the range of 2–0.01 V. A considerably high desodiation capacity of 239 mAh g−1 can be delivered even at 5 A g−1. This may provide a rational guide for designing hard carbon anode with comprehensive merits for NIBs.