Solid electrolytes based on cellulose nanocrystals with protic ionic liquid for next-generation fuel cells

Abstract

The search for solid electrolytes which have good proton conductivity in anhydrous conditions, thermal and mechanical stability, and are at the same time environmentally friendly and easy to manufacture is a big challenge which we have undertaken. This work presents new solid electrolytes based on cellulose nanocrystals with protic ionic liquid 1-methylimidazolium bis(trifluoromethylsulfonyl) imide (PIL) which have been obtained and whose thermal and conductivity properties and nanoscale organization has been determined. Two membranes were synthesized which differ as to the amount of absorbed PIL. They show excellent thermal stability up to 200 °C. The maximum value of ionic conductivity is about 10−2 S/m at 200 °C in anhydrous conditions and falls in the range of 10−3–10−2 S/m for temperatures from 150 to 200 °C. The correlation between the transport properties of membranes and their nanostructure has been probed by solid-state nuclear magnetic resonance spectroscopy. The thermal and conductivity properties of the new materials can compete with currently available membranes. Further work on a composite with a similar chemical composition should lead to obtaining a membrane capable of operating in next-generation fuel cells (T > 120 °C).