Kunlei Zhu

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.

In situ synthesis of mesoporous single-grain layer anatase TiO2 nanosheets without additives via a mild and simple process for a long-term Li-ion battery

There are few reports on mesoporous anatase TiO2 nanosheets being synthesized without additives and ex situ templates under mild conditions. In this study, mesoporous single-grain layer anatase (MSGLA) TiO2 nanosheets were first synthesized in situ without additives in a new methanol–tetrabutyl titanate (TBT) system on a large scale using a simple and easily reproducible method. The formation mechanism of the MSGLA TiO2 nanosheets was investigated in detail. The results suggest that MSGLA TiO2 nanosheets can be obtained after a simple thermal treatment of amorphous TiO2 sheets that are converted in situ from the precursor Ti(OC4H9)4−n(OCH3)n (1 ≤ n ≤ 4) (TBM), which is gained easily via the transesterification reactions of TBT and anhydrous methanol at room temperature. Moreover, the MSGLA TiO2 nanosheets were applied successfully as anode materials for Li-ion batteries (LIB) and exhibited a discharge capacity of ∼73 mA h g−1 with obvious voltage plateaus over 4000 cycles (a test time of ∼50 days) at 5 C (1 C = 170 mA g−1) and Coulombic efficiencies of each cycle approaching 100%, highlighting them as promising materials for long-term LIB.