Characteristics of Sn/Li2O multilayer composite anode for thin film microbattery

Sputtering growth of a Sn/Li₂O multilayer composite thin film is conducted to produce an anode thin film with less capacity fading than that of a pure SnO₂ film for a thin-film battery. The structural properties of the Sn/Li₂O multilayer are examined. In addition, the electrochemical characteristics of the Sn/Li₂O and pure SnO₂ thin films are compared. X-ray diffraction and transmission electron microscopy measurements reveal a Sn crystalline peak only and a Sn–Li₂O multilayer structure, respectively, in the Sn/Li₂O thin film. A SnO₂ thin film with a polycrystalline phase shows an irreversible side-reaction at 0.8 V versus Li/Li⁺, an initial charge retention of about 29%, and poor cycleability in the cut-off voltage range from 1.2 to 0 V versus Li/Li⁺. By contrast, no irreversible side-reaction is found in the Sn/Li₂O multilayer composite thin film while there is an initial charge retention of 49% and better cycleability (more than twice) than that of pure SnO₂ film after about 150 cycles. These results indicate that the Sn/Li₂O multilayer composite thin film can be used for tin-based, thin-film, microbatteries and provide motivation to pursue fabrication of Sn–Li₂O anode powder for bulk type batteries.