Improving proton conductivity and ionic selectivity of porous polyolefin membranes by chitosan deposition

The paper presents a new method for modifying polyolefin membranes using chitosan deposition in order to apply them as a separator in the redox flow batteries with an aqueous electrolyte. Chitosan is deposited from an aqueous carbonic acid under high pressure of saturating carbon dioxide, which allows to increase the affinity of the composite membrane to aqueous electrolyte and, as a consequence, to increase the proton conductivity. In addition, the deposition of a chitosan film makes it possible to reduce the pore size, which means an increase in the ionic selectivity of the porous membrane. In the article, membranes modified with chitosan for different times were obtained. It was shown that as a result of the proposed treatment, the ionic selectivity of membranes increases from 0.2·107 ms·min/cm3 to 5·107 ms·min/cm3.