Solid Polymer-in-Ceramic Electrolyte Formed by Electrophoretic Deposition

We present here a new solid composite polymer-in-ceramic electrolyte formed by electrophoretic deposition (EPD) and saturated with lithium iodide. Composite films have been characterized by ESEM, MTGA, XPS, NMR and impedance-spectroscopy methods. We have found that the EPD of polyethylene oxide alone is impossible, either from acetone- or from ethanol-based suspensions. Addition of polyethylene imine to the suspension increases the deposition rate of both LiAlO 2 ceramic particles and polyethylene oxide, and the duration of stirring increases the PEO content in the film. Composite LiAlO 2 :LiI:P(EO) 3+x electrolyte, in which salt/ceramic grain-boundaries play a dominant role in lithium-ion transport, is characterized by high, temperature-independent conductivity (0.5 mS/cm). Lithium-ion species of higher and lower mobility have been distinguished in NMR spectra. Deconvolution of the spectra revealed that the fraction of the more mobile lithium ions was about 2% between 25 and 65°C, and it increases to 10% above 70°C.