Revisiting on the effect and role of TiO2 layer thickness on SnO2 for enhanced electrochemical performance for lithium-ion batteries

Abstract

Careful modulation of surficial and interfacial properties of electrode materials is a critical factor for determining overall electrochemical characteristics. Recent studies have indicated that metal oxide nanocoating layer (such as titanium (IV) oxide (TiO2)) on metal oxide anodes (such as tin (IV) oxide (SnO2)) exhibited superior electrochemical properties, but fundamental research on the effect and role of TiO2 layer thickness has been limited. Here we have successfully conducted in-depth study on how the thickness of TiO2 overlayer on SnO2 can have significant influence in the overall parameters of electrochemistry. It is revealed that TiO2 overlayer with 12 nm shows good cycle retention (75.8%) even after 80 cycles and retains capacity of 438.3 mAh g−1 even at high current density (5000 mA g−1). Surprisingly, it was further discovered that TiO2 layer not only alleviates the volume expansion but also helps to facilitate Li ion transport compared with SnO2. The improvements in both ionic and electrical conductivity of TiO2 layer are main factors in better cycle retention and rate capabilities. Finally, in situ transmission electron microscopy analysis was adopted to observe the growth dynamics of solid electrolyte interphase layer on TiO2@SnO2, which demonstrates that TiO2 overlayer results in homogeneous and thinner interphase layer compared with SnO2 NTs.