Publication

Abstract : Silicon is a potential anode material for advanced lithium ion batteries due to its high capacity and low voltage. Interfaces play a crucial role in Coulombic efficiency and cycling stability hence interfaces engineering is inevitable to improve performance of silicon. In the present work, ultra-thin TiO2 interlayers have been introduced between the interfaces of sputtered silicon thin-films to study its effect on the cycling stability. The electrochemical investigations indicate that the TiO2 interlayer significantly improves the capacity and cycling stability. Out of the four different configurations investigated (including the bare silicon film), TiO2 interlayer between the film/current-collector is more effective and increases the stability at all rates. Reversible capacity of about 1000 mAh/g at 1.25C rate (equivalent to 5.25 A/g) and 635 mAh/g at 2.5C rate (equivalent to 10.5 A/g) at the end of 100 cycles. Further impedance spectroscopy, scanning electron microscopy and x-ray photoelectron spectroscopy studies were conducted before and after 50 cycles to understand the possible reasons for the improvements. It is observed that the SEI layer on Cu/TiO2/a-Si electrode was thin and stable with LiF and LiPFX composition leading to facile lithium diffusion and lower charge transfer resistance resulting in good electrochemical performance.