Lithium complex in polyacrylonitrile/EC/PC gel-type electrolyte

Lithium complex with C=N group of polyacrylonitrile (PAN) in the PAN-based electrolyte plasticized (7.5 wt% of the total weight) with binary mixture, ethylene carbonate (EC) and propylene carbonate (PC) are present. At low sa lt concentration, lithium is exchanged rapidly between the polymer substrat e and the EC/PC mixture. But with increasing salt content the electrolyte v iscosity increases, and the formation of a weak complex between lithium ion and the CN group in PAN is observed. Sudden increase in the Li-7 chemical shifts substantially broadened line-width in Li-7 NMR and the two-fold incr ease of the activation energy in variable temperature (LiT1)-Li-7 relaxatio n measurements indicated clear presence of the complex. However, the conduc tivity is not substantially decreased with the appearance of the complex. T he result suggested that the ion transport through the more direct lithium site-jump along the polymer chain is equally effective as the ion diffusion through the EC/PC solvent. (C) 2001 Elsevier Science Ltd. All rights reser ved.