Catalytic Upcycling of Recovered Ethylene Carbonate and Lithium from a Spent Lithium-Ion Battery Electrolyte into Reprocessable Copolyester Elastomers

Spent lithium-ion battery electrolytes contain valuable ethylene carbonate (EC) and lithium species that are commonly recovered as separate low-value streams. Here, we report a lithium-derived heteropolyacid ionic liquid catalyst that enables the direct upcycling of recovered electrolyte components into copolyester elastomers (PEMSs). Recovered EC was validated as an effective feedstock, while recovered lithium species were used to prepare a lithium-derived heteropolyacid ionic liquid catalyst for promoting the EC–dimethyl succinate coupling/polycondensation pathway. The resulting PEMSs exhibited low glass-transition temperatures (ca. −95 °C), stable viscoelasticity at elevated temperatures, and low residual strain in creep–recovery tests, with PEMS-2 showing less than 2% and 3% residual strain at 100 and 150 °C, respectively. Catalyst-assisted transesterification further enabled topological rearrangement and reprocessing. This work establishes a catalytic waste-to-material route for valorizing key components in spent electrolytes.