The steady state current and transference number measurements in polymer electrolytes

Abstract

The measurement of transference numbers using the method of steady state currents is discussed on the basis of simple models relating to polymer electrolytes. From an elementary treatment of diffusion processes and ion fluxes, it is concluded that transference numbers can be calculated accurately only when the diffusion of ion pairs and other ion aggregates is negligible. Usually the steady state current will be considerably enhanced by the diffusion of such entities, and this could have important implications for the optimisation of electrolyte properties for battery applications. It is shown in principle that a lithium battery could operate successfully even if t Li + = 0, provided that there is a plentiful supply of mobile ion pairs in solution.