Polymer electrolyte films for energy applications

by | Jan 21, 2013

MIT researchers change film morphologies by making simple changes in LbL assembly conditions.

A mechanically robust membrane with high ionic conductivity and selectivity is an important component in many electrochemical energy devices such as fuel cells, batteries, and photovoltaics.  The ability to control and improve independently the mechanical, ionic conductivity, and selectivity properties of a membrane is highly desirable in the development of next generation electrochemical devices.

Given the importance of these qualities to the future of development in this field, a group of MIT researchers have demonstrated the use of layer-by-layer (LbL) assembly to generate three different polymer film morphologies on highly porous electrospun fiber mats: webbed coatings, conformal fiber coatings, and pore-bridging films.  Specifically, they found that depending on the use of dip-LbL or spray-LbL, and the application of vacuum through the membrane during the spray-LbL assembly method, the polyelectrolyte film either fills the voids of the mat with the proton conducting material or forms a continuous fuel-blocking layer of the same low methanol-permeability film.

Furthermore, the mechanical properties of the composite mat they created are superior to the stand-alone LbL film, particularly under hydrated conditions.  Their study demonstrates the versatility and flexibility of this technique, since any ion conducting LbL system may be sprayed onto any electrospun fiber mat, allowing for independent control of functionality and mechanical properties.