Porous Ion Exchange Membranes for Vanadium Redox Flow Battery

  • Poröse Ionenaustauschermembranen für die Vanadium-Redox-Flowbatterie

Luo, Tao; Weßling, Matthias (Thesis advisor); Lehnert, Werner (Thesis advisor)

Aachen (2017)
Dissertation / PhD Thesis

Dissertation, RWTH Aachen University, 2017


This thesis describes the systematic study of a new type of ion exchange membranes for the application in all vanadium redox flow batteries (VRFB). The membranes were fabricated from poly(2,5-bibenzimidazole) copolymer (ABPBI) solutions by the water vapor induced phase separation process. The resultant membranes have a symmetric cross-sectional structure with macropores (2 to 10 microns) distributed in the nanoporous membrane matrix. These membranes have extremely low permeability of vanadium ions {V(IV)} and high proton conductivity in sulfuric acid, which is paramount for VRFB. The ion transport properties of these membranes can be easily tuned by the phase separation conditions and treatment with acid. These porous ABPBI membranes lead to a very high energy efficiency of the battery compared with the commercial Nafion membranes. The long-term investigation of the membranes in oxidative V(V) electrolyte reveals excellent chemical stability of these membranes. The scalable fabrication process, tunable transport selectivity and excellent stability of these nanoporous membranes make them ideal separators for the practical application in VRFB.