Dielectric properties and I-V characteristics of Li _0.5 La _0.5 TiO ₃ solid electrolyte for ceramic supercapacitors

Solid electrolyte is crucial important for the developing of next generation supercapacitors. Tetragonal perovskite Li _0.5 La _0.5 TiO ₃ (LLTO) solid electrolyte ceramics were prepared by using conventional solid-state reaction method. Clear interfaces between the metal electrodes (Ag, Au or Pt) and the LLTO ceramics were observed. Nominal colossal permittivity at low frequency and strong frequency dispersion were observed in LLTO samples with different metal electrodes. The leakage currents decrease exponentially after the application of a stepwise DC voltage and show dramatic differences between different electrodes. The current-voltage (I-V) characteristic curves also indicate the differences, where the peak currents at maximum 5 V loading are 5.1 nA for sample with Ag electrode, 138.9 nA for Au electrode and 13.5 μA for Pt electrode. In addition, there is a clear redox current peak at about 4 V in LLTO/Pt sample and a blurred peak in LLTO/Au sample at around 2 V, which indicates an electrochemical reaction between LLTO and Pt/Au electrodes. These differences are attributed to the redox reaction of the Schottky contact interface between samples and electrodes. These interfacial I-V characteristics between LLTO and metal electrodes help us to understand the underlying mechanism in the future solid electrical double layer ceramic supercapacitors.