Perfluorinated membranes and improved electrolytes for redox cells and batteries

A process for making a redox cell comprising a positive half-cell in communication with a positive half cell solution that contains at least one vanadium ion selected from the group consisting of vanadium (III), vanadium (IV) and vanadium (V);

• a negative half-cell in communication with a negative half cell solution that contains at least one vanadium ion selected from the group consisting of vanadium (II), vanadium (III) and vanadium (IV);
• and a cast perfluorinated ionically conducting membrane located between the positive half cell and the negative half cell and in contact with the positive half cell solution and the negative half cell solution and wherein the perfluorinated membrane comprises a polymer selected from the group consisting of a PTFE, perfluorosulfonic acid and a perfluorosulphonic acid/PTFE copolymer, said membrane having isotropic swelling and tensile strength properties, a conductivity at 25° C. of between 0.01 and 1 S/cm, and having a linear expansion selected from the group consisting of less than 8%, less than 5% and less than 3% in both directions from 50% Relative Humidity at 23° C. to water soaked at 23° C.,
• said process comprising:
• treating a cast perfluorinated ionically conducting membrane prior to use in the redox cell by soaking the membrane in an aqueous solution to reduce resistivity of the membrane and enhance voltage efficiency during the charge-discharge cycling of the redox celltreating the membrane prior to use in the redox cell by soaking the membrane in an aqueous solution to reduce resistivity of the membrane and enhance voltage efficiency during the charge-discharge cycling of the redox cell;
• locating the membrane between and in contact with a positive half cell and a negative half cell, and introducing a positive half cell solution into the positive half cell and a negative half cell solution into the negative half cell, wherein:
• the positive half cell solution contains at least one vanadium ion selected from the group consisting of vanadium (III), vanadium (IV) and vanadium (V);
• the negative half cell solution contains at least one vanadium ion selected from the group consisting of vanadium (II), vanadium (III) and vanadium (IV);
• and
• the perfluorinated ionically conducting membrane comprises a polymer selected from the group consisting of a PTFE, perfluorosulfonic acid and a perfluorosulphonic acid/PTFE copolymer.