Issue 7, 2022 - Research on membrane materials for high-performance flow batteries has progressed

Recently, the Li Pioneer research team of the Energy Storage Technology Research Department of the Dalian Institute of Chemical Physics, Chinese Academy of Sciences has made new progress in the large-scale preparation and application of membrane materials for high-performance and low-cost alkaline system flow batteries, and realized the large-area preparation of non-fluorinated cationic conduction membranes through the continuous roll-to-roll membrane making process, and its application
in the energy storage technology of alkaline system flow batteries.

At present, the research on ion conduction membranes for alkaline system flow batteries is very limited, and perfluorosulfonic acid ion exchange membrane (Nafion) has become the preferred membrane material
for flow batteries and even alkaline system flow batteries due to its excellent stability.
However, Nafion membrane has problems such as
complex production process, great harm to the environment and human health due to by-products in the production process, high price, and low ion conductivity under alkaline system, resulting in low battery efficiency.
The development of low-cost, controllable structure and simple preparation process of non-fluorinated anion exchange membranes is expected to solve the above problems
.

However, under the alkaline system, the quaternary amine group on the traditional non-fluorinated anion exchange membrane - quaternary amine anion conduction membrane will undergo Hoffmann elimination and nucleophilic substitution reaction, which makes the stability of this type of membrane poor
.

It is found that the membrane material prepared by the team has excellent alkali resistance stability due to its rigid skeleton structure and charge characteristics, and the discrete sulfonic acid groups on the backbone can form a continuous hydrogen bond network in the membrane, so that the hydroxyl group is rapidly transferred in the membrane with the Grotthuss mechanism, thereby improving the conductivity
of the membrane material.

The research team uses the developed membrane material to integrate a 4 kW alkaline zinc-iron flow battery stack, and the energy efficiency of the stack can reach more than
85% under the condition of 80 mA / square centimeter working current density.