Paul Scherrer Institut

Fabio J Oldenburg

Lorenz Gubler

Alexander Arndt

An electrolyte membrane and method for generating the membrane provide a resistance as low as possible to minimize ohmic losses. The membrane has a low permeability for redox-active species. If redox-active species still cross the membrane, this transport is balanced during charge and discharge preventing a net vanadium flux and associated capacity fading. The membrane is mechanically robust, chemically stable in electrolyte solution, and low cost. A family of ion exchange membranes including a bilayer architecture achieves these requirements. The bilayer membrane includes two polymers, i) a polymer including N-heterocycles with electron lone pairs acting as proton acceptor sites and ii) a mechanically robust polymer acting as a support, which can be a dense cation exchange membrane or porous support layer. This bilayer architecture permits a very thin polymer film on a supporting polymer to minimize ohmic resistance and tune electrolyte transport properties of the membrane.

Bilayer electrolyte membrane and a redox flow battery comprising a bilayer electrolyte membrane

A membrane with high ion selectivity, balancing influence on vanadium transport in all-vanadium redox-flow environment, high physicochemical stability and potentially low cost is an amphoteric ion exchange membrane with defined ratio of anion and cation exchange capacity, in particular for redox flow batteries. The membrane includes a mechanically robust and chemically resistant base polymer film (matrix), ion exchange groups covalently bound to the polymer matrix, being a mixture of anion and cation exchange groups, a comonomer including 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) to balance transport of positively charged redox-active ions, a quaternary bonded alpha-C atom in comonomers to protect the resulting polymer sterically against chemical degradation. Optionally, additional functional constituents, such as crosslinkers and/or antioxidants are provided.

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Windisch, Switzerland

Fabio J Oldenburg