(Invited) Novel Ti4O7 /MnO2 Pseudocapacitive Composite for High Energy Density and Stability Supercapacitor

Abstract

Titanium dioxide (TiO2)-rutile has been considered as one of the promising candidates in supercapacitors due to its low cost, electrochemical stability, natural abundance, high surface area, low toxicity, and easy preparation in defined nanoscale dimensions. However, its specific capacitance is substantially lower than those of other pseudocapacitive metal oxides. In this study, we have demonstrated that the specific capacitance of TiO2-rutile can be dramatically improved by increasing oxygen deficiency. After phase transition to Magnéli phase, Ti4O7-electrode possesses a high specific capacitance of 168 F/g at 2 mV/sec, which is 10 times that of pristine TiO2-rutile. To further improve the specific capacitance, Ti4O7 is modified with 7 wt% MnO2, showing 345.5 F/g in an aqueous Li2SO4 electrolyte between 1 V and -1 V versus Ag/AgCl/saturated KCl without the problem of Mn ion dissolution. Furthermore, the composite electrode exhibits a high specific capacitance of 225 F/g even at a high scan rate of 400 mV/sec since Ti4O7 shows high conductivity. In addition, the Ti4O7/MnO2 supercapacitor exhibits 81 % capacitance retention with cycling up to 5000 cycles under the large potential range (1.6V). In view of the energy storage capacity, this new composite electrode holds great promise for next-generation high-energy supercapacitors. Figure 1