Preparation and characterization of ZnO/SnO_2 composite thin films as high-capacity anode for lithium-ion batteries

摘要

The ZnO/SnO_2 composite thin films were prepared on copper collectors as anode for LIBs by electron beam evaporation, with ZnO thin layer grown by magnetron sputtering. The structure, surface morphology and elemental composition were investigated by X-ray diffraction and scanning electron microscopy with an energy-dispersive X-ray spectrometer. The active materials were mainly composed of tin oxide thin films characterized with nanosized particles with dozens of nanometers. The cyclic voltammograms (CV), discharge/charge and rate performances were employed to characterize electrochemical properties of prepared thin-film electrode material. The CV curves revealed a typical alloying/dealloying of tin oxide with stepwise redox reactions according to the cathodic and anodic peaks. The significant improvement in specific capacity is observed in the curves of ZnO/SnO_2 thin-film electrode, comparing with alone SnO_2 thin-film anode. The discharge-specific capacity for ZnO/SnO_2 thin film is 758.93, 465.7, 430.9, 344.7, 246.3 and 152.4 mAh/g, at the rate of 0.05C, 0.2C, 0.5C, C, 2C and 4C, respectively, about 5-10 times larger than that of alone SnO_2 thin-film anode. The rate performance of the composite thin film has also been enhanced by introducing the ZnO thin layer. It is a good strategy to applying the ZnO in-terlayer to strengthen the electrochemical performances of SnO_2 and decrease the irreversible capacity loss.