Electrochemical characterization of poly(ethylene oxide)- zinc chloride system and its application in rechargeable batteries

The system PEOnZnCl2 with n=4-16 was studied in view of its potential application in a solid state rechargeable zinc battery. A.c. conductivity and cationic transference number measurements, in the temperature range 20-150ºC, were performed and the electrochemical stability window was established for the polymer electrolyte with n=4 composition. The ionic conductivity, σ, of this film, follows a VTF behaviour, with an activation energy of 3.3 ± 0.2 kJ mol-1 and σ values were found between 2.50x10-7 S cm-1 at 24ºC and 4.81x10-4 S cm-1 at 145ºC. Acceptable zinc ion transference numbers of 0.36 (medium value) and decomposition voltage values between 3.19V (20ºC) and 1.44V (150ºC) were estimated. Cyclic voltammetric studies using Zn/PEO4ZnCl2/Zn cell indicated reversibility of the Zn/Zn2+ couple at the electrode/electrolyte interface. Several cells Zn(-)/PEO4ZnCl2/Nb2O5(+) were assembled and studied at 55ºC, with several discharge current densities. Results of cell’s discharge profiles, capacity values, charge-discharge cycles behaviour and stability are reported