Hard carbon derived from corn straw piths as anode materials for sodium ion batteries

Hard carbon is considered as the most promising anode material for practical sodium ion batteries. Herein, we report biomass-derived hard carbon made from corn straw piths through a simple carbonization process. X-ray diffraction patterns and Raman spectra elucidated highly disordered structures, and high-resolution transmission electron microscopy confirmed that the hard carbons have many local ordered structures containing turbostratic nanodomains and more nanovoids surround the turbostratic nanodomains. The electrochemical performances of the hard carbons were systematically investigated in sodium ion batteries. By optimizing the carbonization temperature, the sample carbonized at 1400 °C (HC1400) exhibited high reversible capacity of 310 mAh g−1 and good cycling stability; the capacity can still retain 274 mAh g−1 after 100 cycles. More importantly, HC1400 can deliver reversible capacity of 206 mAh g−1 with 79% retention rate after 700 cycles measured at a current density of 200 mA g−1, which is much better than those in most previous reports. This study provides a way to develop inexpensive, renewable, and recyclable materials from biomasses towards next-generation energy storage applications.