Dramatically Enhanced Li-Ion Storage of ZnO@C Anodes through TiO2 Homogeneous Hybridization

Amorphous nanoparticles of ZnO and TiO2 embedded in carbon nanocages (AZTCNCs) were successfully synthesized through a simple annealing process of TiO2 -coated zeolitic imidazolate framework-8 (ZIF-8). In the current anode of AZTCNCs, tiny ZnO and TiO2 nanoparticles were uniformly distributed in the carbon matrix (carbon nanocages), which could effectively buffer the volume expansion of electroactive ZnO and provide excellent electric conductivity. After fully investigating the electrochemical performance of the AZTCNCs samples obtained with different additive amounts of tetrabutyl orthotitanate (TBOT) for TiO2 coating, it has been found that AZT-30 (0.1 g ZIF-8 with 30 mL TBOT) shows the best cycle stability (510 mAhg-1 after 350 cycles at 200 mAg-1 ) and a superior rate capability (610 mAhg-1 after 3500 cycles at 2 Ag-1 ). The greatly enhanced Li-ion storage performance could be ascribed to the fact that the introduction of amorphous TiO2 could activate the reversible lithiation/delithiation reaction of ZnO during the charge/discharge process.