Qiwei Tang

Submicron-sized mesoporous anatase TiO2 beads with a high specific surface synthesized by controlling reaction conditions for high-performance Li-batteries

The effect of reaction temperature and aging time on TiO2 precursor beads synthesized using a sol–gel method was studied. The size of the precursor beads decreased and deformed spheres appeared with increasing temperature. Meanwhile, TiO2 precursor beads grew with the aging time up to a reaction time of 18 h. Using a solvothermal process for the precursor beads, submicron-sized mesoporous anatase TiO2 beads (SMATBs) with a specific surface of 153.2 m2 g−1, much higher than initially reported, were synthesized by controlling the reaction conditions and were successfully employed as negative electrode for Li-ion batteries. The specific capacities of the submicron-sized mesoporous TiO2 beads are much higher than those of their counterparts at high charge–discharge rates. In the first cycle, the TiO2 beads showed discharge capacities of 172.0 mA h g−1, 129.6 mA h g−1, 117.1 mA h g−1 and 56.7 mA h g−1 at charge–discharge rates of 1 C (1 C = 170 mA g−1), 5 C, 10 C and 30 C, respectively. 85.1% discharge capacities were retained after 200 cycles at 1 C charge–discharge rate. After 600 cycles, there is still 81.8% discharge capacity retained at 5 C charge–discharge rate. Moreover, the TiO2 beads also exhibitied 86.9 mA h g−1 and 34.0 mA h g−1 discharge capacities at 10 C and 30 C charge–discharge rates over 600 cycles, respectively. In addition, the Coulombic efficiency is nearly 100% at each cycle at various charge–discharge rates.

Study on the Capacitance Performance of Graphene

In this paper, the electrochemical performance of the supercapacitors with graphene as their materials was studied. Graphite oxide were prepared by modify Hummers method. Then graphene were obtained that GO as the precursors rapidly exfoliated at the temperatures of 400°C under nitrogen atmosphere. The capacitance can reach to 342 F·g−1 at the current density of 1000 mA·g−1. The graphene exhibited an enhanced storage capacity as electrode material in Supercapacitors.