Ionic conduction properties of PVDF-HFP type gel polymer electrolytes withlithium imide salts

Conduction properties of gel polymer electrolytes composed of lithium imide salts, LiN(CF3SO2)(2), LiN(C2F5SO2)(2), and PVDF-HFP copolymer were invest igated using the pulsed-field gradient NMR and complex impedance techniques . The diffusion coefficients of the gel decreased with an increase in the p olymer fraction in the gel. Carrier concentration exhibited 3 orders of mag nitude variation in the fraction change in polymer from 80% to 20%. These r esults suggest that the polymer interacts with the electrolyte to affect th e carrier concentration and mobility of the gel electrolytes. The interacti ve effect of polymer would be detected in the measurements of spin-lattice relaxation time (T-1). The deviation of the symmetric curve of the temperat ure dependence of T-1 could be divided into two components, one was consist ent with the component of solution and independent of the polymer fraction and the other depended on the polymer fraction in the gel.