Non-Isocyanate Poly(hydroxyurethane)-Based Networks as Solid Polymer Electrolytes for Lithium Metal Batteries

We report here on the facile synthesis of poly(hydroxyurethane) (PHU) networks obtained via the ring-opening of cyclic carbonates present on bio-based carbonated soybean oil by poly(ethylene glycol) (PEG) segments of various lengths and functionalized at both ends by amines. We also explore the possibility to prepare PHU-poly(epoxy) mixed networks by additionally incorporating PEG segments functionalized at both ends by epoxides in the reaction mixture. The accordingly obtained polymer networks possess high flexibility and a good interfacial stability. After salt loading, the solid polymer electrolyte (SPE) membranes based on PHU and PHU-poly(epoxy) mixed networks exhibit ionic conductivities in the range of ~10^-4.5 to 10^-5 S cm^-1 at 60 °C with oxidation stability >4.2 V versus Li/Li⁺. Further, their long-term compatibility with lithium metal has been investigated for more than a hundred cycles in stripping and plating experiments. Those results drive the PHU-based networks toward the development of electrolytes with a high degree of control on structure and properties, dealing with the trade-off of mechanical and electrochemical properties usually met with PEG-based SPEs.