Upcycling waste poly(ethylene terephthalate) into polymer electrolytes

Lithium-ion batteries (LiB) play an important role in energy storage in our increasingly-electrified modern world, with polymer electrolyte (PE) materials poised to revolutionise battery design by eliminating the most critical safety hazards associated with liquid electrolytes in use today. Although there is growing focus on sustainable PE designs, the use of abundant waste commodity plastics as an alternative feedstock for PE production remains surprisingly overlooked. Herein, we report the first examples of PEs obtained by chemical upcycling of waste poly(ethylene terephthalate) (PET) bottles, exploiting the susceptibility of PET's ester linkages for chemical solvolysis and the structural rigidity of the terephthalate aromatic components to allow for free-standing conductive film formation. Our PET-derived polyurethane PEs show promising ionic conductivity when used as both solid and gel polymer electrolytes, and can be assembled into a working lithium-ion battery. This sets a precedent for designing future sustainable PE materials from waste plastics and contributing towards a circular materials economy. The first working lithium-ion battery containing polymer electrolytes derived from waste poly(ethylene terephthalate) beverage bottles is demonstrated.