Electrochemical properties of nitrogen-doped carbons prepared by the thermal reduction of furfurylamine-intercalated graphite oxide

Abstract

Nitrogen-doped carbons were prepared by the thermal reduction of furfurylamine-intercalated graphite oxide. The nitrogen atom content in the resulting samples was around 6 wt% and was almost constant, independent of the thermal reduction temperature. The nitrogen atoms were introduced in the forms of pyridinic, pyrrolic and graphitic, and the amount of graphitic nitrogen greatly increased for the sample prepared at 800 °C. The discharge capacity above 1.0 V greatly decreased for nitrogen-doped carbon samples when used as anodes of a lithium ion battery. It reached a maximum value of 334 mA h/g for the sample prepared at 500 °C. X-ray diffraction measurements during a charge-discharge cycle indicated that lithium ions were stored between and extracted from the layers in the material and the increase in the interlayer spacing after lithium storage was similar to that observed for graphite. This result has been well reproduced by theoretical calculations and nitrogen atoms stayed at almost the same position even after the intercalation of lithium ions. This would prevent the intercalation of a large amount of lithium and accordingly lower the capacity.