Crosslinked polytetrahydrofuran-based solid-state electrolytes with improved mechanical stability and electrochemical performance

Solid-state lithium-ion batteries using polymer electrolytes are viewed as a promising approach for the next generation of high-energy-density and safe solid-state batteries. Still, solid polymer electrolytes (SPEs) face real-world application challenges due to poor room temperature performance, inadequate stability, interface contact issues, and low mechanical strength. Herein, we present a novel crosslinked polytetrahydrofuran-based solid-state electrolyte (aPTHF*) with the varying ratios of lithium bis(trifluoromethanesulfonyl)imide salt (LiTFSI), fabricated via UV-photocrosslinking process. To enhance mechanical and chemical stability, aPTHF-based SPE formulations (aPEP) were also produced by incorporating poly(ethylene glycol) diacrylate (PEGDA) and trimethylolpropane ethoxylate triacrylate (ETPTA) oligomers into the structure. The designed unique structure facilitated ion migration, and the highest value of ionic conductivity was 3.16 × 10^-5 S·cm^-1 at 80 °C for aPEP4 formulation. Fabricated SPEs demonstrated high mechanical strength with a tensile strength of 13 MPa and a broad electrochemical stability window of around 5 V which allowed good interfacial stability with the LFP electrode, showing cycling stability at C/10 in an all-solid-state battery. Moreover, Li|aPEP4|LFP pouch cells were assembled, and the flexible cell and remained functional even after being bent and folded over 20 times. The flexible electrolyte demonstrated in this research offers a promising system for future studies on all-solid-state batteries.