Amorphous tin oxide films: preparation and characterization as an anode active material for lithium ion batteries

Tin oxide thin films were prepared by the electrostatic spray deposition at 400 degreesC, followed by annealing at 500 degreesC in air. X-ray diffraction and X-ray photoelectron spectroscopy revealed that the resulting films were amorphous SnO2. The electrochemical properties of the SnO2 films with lithium were studied by in situ conductivity measurements using an interdigitated microarray electrode as well as by cyclic voltammetry, galvanostatic cycling measurements and ac-impedance spectroscopy in 1 M LiClO4/(PC + EC). The SnO2 film electrodes exhibited reversible capacities greater than 1300 mA h g(-1) when cycled between 0.05 and 2.5 V at 0.2 mA cm(-2). However, this capacity faded rapidly after repeated cycling. If the electrode was cycled between 0 and 1.0 V, a reversible capacity of 600 mA h g(-1) was maintained for more than 100 cycles. In addition, a stable reversible capacity of about 500 mA h g(-1) was obtained even at current density as high as 2 mA cm(-2). Thus it is suggested that a higher potential than 1.5 V would cause reformation of tin oxide, which may destroy the stable nanocomposite structure of metallic tin and lithium. These arguments were supported by in situ conductivity measurements with microarray electrodes. (C) 2001 Elsevier Science Ltd. All rights reserved.