Electrochemical Performance of MnO2/Graphene Flower-like Microspheres Prepared by Thermally-Exfoliated Graphite
Xuyue Liu, Bing Liang, Xiaodong Hong, Jiapeng Long
Abstract
To enhance the electrochemical performance of MnO 2 /graphene composite, herein, thermally-exfoliated graphite (TE-G) is adopted as a raw material, and a hydrothermal reaction is conducted to achieve the exfoliation of TE-G and the loading of MnO 2 nanosheets. Through optimizing the TE-G/KMnO 4 ratio in the redox reaction between carbon and KMnO 4 , flower-like MnO 2 /G microspheres (MnO 2 /G-10) are obtained with 83.2% MnO 2 and 16.8% residual graphene. Meanwhile, corresponding MnO 2 /rGO composites are prepared by using rGO as raw materials. Serving as a working electrode in a three-electrode system, MnO 2 /G-10 composite displays a specific capacitance of 500 F g −1 at 1 A g −1 , outstanding rate performance, and capacitance retention of 85.3% for 5,000 cycles. The performance is much better than that of optimized MnO 2 /rGO composite. We ascribe this to the high carbon fraction in TE-G resulting in a high fraction of MnO 2 in composite, and the oxygen-containing groups in rGO reduce the resulting MnO 2 fraction in the composite. The superior electrochemical performance of MnO 2 /G-10 is dependent on the hierarchical porous structure constructed by MnO 2 nanosheet arrays and the residual graphene layer in the composite. In addition, a supercapacitor assembled by TE-G negative electrode and MnO 2 /G positive electrode also exhibits superior performance. In consideration of the low cost of raw materials, the MnO 2 /G composite exhibits great application potential in the field of supercapacitors.