Ionic conductivity and diffusion coefficients of lithium salt polymer electrolytes measured with dielectric spectroscopy

Ionic conductivity, diffusion coefficients, mobility and ionic concentration for lithium salts dissolved in polymer electrolytes are determined by the modeling of the dielectric loss and spectra. Cation and anion diffusion coefficients are quantified using the Trukhan model depending on the assumed ratio of the cation to anion diffusion coefficients. Measurements are performed for polymer electrolytes consisting of polyethylene oxide (PEO) with dissolved LiClO 4 salts for different sample thicknesses and temperatures ranging from 5 to 105 °C, which comprises both the crystalline and amorphous phases of the composite electrolyte. A good phenomenological description of the dielectric loss spectra is obtained for both the semi-crystalline and amorphous phases. The fraction of mobile ions is estimated to vary from 0.002% at 25 °C (semi-crystalline phase) up to 0.05% at 80 °C (amorphous phase).
This research has been supported by the IMIDIC/2009/152 project, granted by the Generalitat Valenciana (Valencia, Spain) through the Institute for Small and Medium Industry (IMPIVA) and the European Union by FEDER funds. Dr. A. Munar acknowledges the support of the Ramon y Cajal programme08-18-463B-750, and Grant MAT2009-14602, Ministerio de Ciencia e Innovacion, Spain.