Medical University of South Carolina

Laura A Murdock

Brian C Benicewicz

Fei Huang

Lihui Wang

Andrew Pingitore

Novel PBI films which may be used in electrochemical cells, such as redox flow batteries, are disclosed. Additionally, disclosed herein are membranes which comprise the novel PBI films which may be free from an organic solvent, and have a tensile strength at break of at least 25 MPa after drying.

Polybenzimidazole films

A novel process for making PBI films starting from gel PBI membranes polymerized and casted in the PPA process wherein acid-imbibed gel PBIs are neutralized in a series of water baths and undergo controlled drying in association with a substrate material, yielding a PBI film without the use of organic solvents.

PBI films formed without use of organic solvents

Disclosed are redox flow battery membranes, redox flow batteries incorporating the membranes, and methods of forming the membranes. The membranes include a polybenzimidazole gel membrane that is capable of incorporating a high liquid content without loss of structure that is formed according to a process that includes in situ hydrolysis of a polyphosphoric acid solvent. The membranes are imbibed with a redox flow battery supporting electrolyte such as sulfuric acid and can operate at very high ionic conductivities of about 100 mS/cm or greater. Redox flow batteries incorporating the PBI-based membranes can operate at high current densities of about 100 mA/cmor greater.

Polybenzimidazole (PBI) membranes for redox flow batteries

The current disclosure teaches one to achieve PBI membranes with high ionic conductivity and low mechanical creep for the first time. This is in contrast to previous teachings of PBI membrane fabrication methods, which yield PBIs with either high ionic conductivity and high mechanical creep or low ionic conductivity and low mechanical creep. The membranes produced according to the disclosed process provide doped membranes for applications in fuel cells and electrolysis devices such as electrochemical separation devices.

Proton-conducting PBI membrane processing with enhanced performance and durability

Disclosed are redox flow battery membranes, redox flow batteries incorporating the membranes, and methods of forming the membranes. The membranes include a densified polybenzimidazole gel membrane that is capable of incorporating a high liquid content without loss of structure that is formed according to a process that includes in situ hydrolysis of a polyphosphoric acid solvent followed by densification of the gel membrane. The densified membranes are then imbibed with a redox flow battery supporting electrolyte such as sulfuric acid and can operate at very high ionic conductivities of about 50 mS/cm or greater and with low permeability of redox couple ions, e.g. vanadium ions, of about 10cm/s or less. Redox flow batteries incorporating the membranes can operate at current densities of about 50 mA/cmor greater.

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Columbia, SC, United States of America

Laura A Murdock