Single-Ion Flexoionic Polymer Energy Harvester under Oscillatory Flexure

The present paper aims to develop solid polymer electrolyte elastomers for energy harvesting and storage devices under dynamic natural environment. The flexoionic elastomer was synthesized by grafting 1-allyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (AMIMTFSI) to a triblock copolymer consisting of olefinic glycol moieties such as PEG-b-PPG-b-PEG end-capped with methacrylate groups (DMA). The strategy of grafting dissociated AMIM+ cations to the polyglycol triblock copolymer network allows selective (or dominant) ion polarization by the mobile TFSI–anions undergoing oscillatory motion, the concept of which is similar to single-ion transport as a means of enhancing electrochemical performance in some solid-state polymer electrolyte batteries. The 60:40 PEG-b-PPG-b-PEG-DMA/AMIMTFSI elastomer achieved a high flexoelectric coefficient on the order of about 380 μC m–1 at 1 Hz and a high energy conversion efficiency of about 14.9% under oscillatory bending mode, which opens an opportunity for energy harnessing from rolling tires.