Analogous graphite carbon sheets derived from corn stalks as high performance sodium-ion battery anodes
Biomass derived carbon (BMC) materials have attracted much attention due to their high performance and abundant sources. Herein, analogous graphite carbon sheets (AGCS) from corn stalks have been synthesized via a simple high temperature carbonization and expansion process. A morphology study showed that the obtained carbon sheets retained the natural cross-sectional honeycomb-like shape and the longitudinal hollow tubular array structure of the corn stalks, which provided abundant macropores and micropores to facilitate sodium ion transportation and electrolyte diffusion. X-ray diffraction analysis showed that the interlayer spacing of the carbon sheets is larger (0.384 nm) than that of graphite (0.335 nm), which allowed sodium ion to be de/intercalated. When used as an anode for sodium ion batteries, the sample carbonized at 1200 °C (AGCS-1200) showed a better sodium ion storage performance than that carbonized at 900 °C (BMC-900). AGCS-1200 exhibits a stable reversible capacity of 231 mA h g−1 after 200 cycles at 0.25C (1C = 200 mA g−1), while the capacity value for BMC-900 was 162 mA h g−1 after 100 cycles. What’s more, a better rate capability for AGCS-1200 (232, 136 mA h g−1) than that of BMC-900 (125, 68 mA h g−1) at rates of 1C and 5C, respectively, is demonstrated. Significantly, the AGCs-1200 anode shows an excellent long-term cycling stability, which delivers a capacity of 42 mA h g−1 after 2000 charge–discharge cycles at a very high rate of 15C.