Graphene-like Graphite as a Novel Cathode Material with a Large Capacity and Moderate Operating Potential for Dual Carbon Batteries

Abstract

Dual carbon batteries have recently attracted significant attention because of their ecofriendliness and reliability. In this study, graphene-like graphite (GLG) was prepared by thermal reduction of graphite oxide to be used as a cathode material, and the electrochemical PF6 − anion-intercalation reaction into GLG was investigated. Decreasing the heat-treatment temperature of GLGs from 900 °C to 600 °C resulted in increasing the reversible capacities and interlayer distances of GLG samples. Among them, GLG synthesized at 700 °C (GLG700) showed the largest discharge capacity of 137 mAh g−1, which was much larger than that of graphite (52 mAh g−1). Variations in the X-ray diffraction patterns and Raman spectra of GLG700 indicated that the stage number reached 1 at 4.8 V (vs Li+/Li) while that of graphite was 2 at the same potential. This indicates that GLG could store PF6 − anion in every interlayer, which is probably one of the main causes of the larger capacity. The charge–discharge cycling test of GLG700 showed that the capacity gradually increased during cycling, and the coulombic efficiency was approximately 97% at every cycle after the 5th cycle. These results clearly demonstrate that GLG can be used as a cathode material with a large capacity for dual carbon batteries.