Hiroyuki Akashi

An Ionic Conductivity and Spectroscopic Study of Ionic Transport Mechanism in Fire‐Retardant Polyacrylonitrile‐Based Gel Electrolytes for Li Polymer Batteries

Solvation reaction and the Li + ion conduction mechanism in fire-retardant poly[acrylonitrile] (PAN)-based gel electrolytes complexed with ethylene carbonate (EC), proplylene carbonate (PC), and LiPF 6 were investigated using Fourier transform Raman scattering spectroscopy (FT-Raman) and conventional complex impedance measurements. FT-Raman spectroscopy eliminated the fluorescence problem of the gel electrolytes, showing that the mole fraction of EC-solvating Li + ions is significantly affected by the LiPF 6 concentration rather than the PAN ratio. Based on deconvolution analysis, the solvation numbers of Li + ions were estimated to be 4.0 to 5.4 in the salt concentration range of 0.28 to 1.35 mol kg -1 , which is corresponding to that in liquid electrolyte-based EC and PC. As for the ionic conduction property of PAN-based gel electrolytes, the activation energy of ionic conduction estimated from the Arrhenius equation is more strongly dependent on the LiPF 6 concentration than the PAN ratio in the temperature range from -20 °C to room temperature. These results confirm that Li + ions dominantly interact with EC and PC dispersed in the network structure of the gel electrolytes and also the polymer chains of PAN make a rigid framework which scarcely interacts with the Li + ions at ambient temperature