AMPHOTERIC ELECTROLYTE MEMBRANE WITH SELECTIVE AND BALANCED ION TRANSPORT PROPERTIES AND A REDOX FLOW BATTERY COMPRISING AN ELECTROLYTE MEMBRANE

摘要

It is the objective of the present invention to provide a membrane with high ion selectivity, a balancing influence on the vanadium transport in all-vanadium redox-flow environment, high physicochemical stability and potentially low cost. These characteristics can be obtained from an amphoteric ion exchange membrane with a defined ratio of anion and cation exchange capacity, in particular for use in a redox flow battery, comprising: a) a mechanically robust and chemically resistant base polymer film (matrix); b) ion exchange groups covalently bound to the polymer matrix, being a mixture of anion exchange groups and cation exchange groups; c) a comonomer comprising two anion exchange groups per molecule to yield a ratio of anion exchange groups to cation exchange groups of 1.5-4 (50-300% excess of anion exchange groups over cation exchange groups) in order to balance the transport of positively charged redox-active ions; d) a quaternary bonded alpha-C atom in the comonomers used to protect the resulting polymer sterically against chemical degradation; and e) optionally additional functional constituents, such as crosslinkers and / or antioxidants.