ANALYSIS OF TRANSFERENCE NUMBER MEASUREMENTS BASED ON THE POTENTIOSTATIC POLARIZATION OF SOLID POLYMER ELECTROLYTES

Various methods developed to measure the lithium ion transference numb er in solid polymer electrolytes have given widely varying results. Th is may be explained by invalid assumptions made in the analyses of the transport experiments, such as the assumption of an ideal, dilute sol ution. One popular method, referred to as the steady-state current met hod, and based on the potentiostatic polarization of a symmetric cell, is analyzed here for a binary electrolyte under concentrated solution theory. The ratio of steady state to initial currents after the impos ition of a potential step is shown to involve all the transport proper ties as well as the mean molar activity coefficient of the salt. This method is compared to other methods that utilize the current/voltage r esponse of a symmetric cell, and underlying similarities in the method s are revealed.