Electrochemical Performance of MnO(2)/Graphene Flower-like Microspheres Prepared by Thermally-Exfoliated Graphite

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.