The effect of UV-crosslinking on the phase behaviour, ionic conductivity, and morphology of the prepared PCIL-SPEs are shown in Figure and Figure . As illustrated in Figure , both the melting point and enthalpy decrease dramatically after introducing CIL (Li:IL molar ratio = 1:1) to PEO, with the melting transition temperature drops from 65 °C of pure PEO to 38 °C of SPE10:1:1, and the Tg broadens significantly, suggesting a more complex heterogenous system. Notably, a small peak at approximately -20°C appears in SPE10:1:1, attributed to a phase transition in the C3mpyrFSI/LiFSI mixture, suggesting limits in IL solubility and potential phase separation. Crosslinking SPE10:1:1 to create SPE10:1:1-CL results in the disappearance of both the melting and phase transition peaks, with a new, pronounced Tg appearing at -74 °C. This suggests that crosslinking leads to a highly amorphous structure and enhances the uptake of IL in PEO matrix. In addition, the presence of a single Tg in the crosslinked materials indicates a good miscibility between IL and the PEO matrices. To summarize, crosslinking effectively hinders crystallization of PEO and PEO-LiFSI complexes and increases the IL uptake in the crosslinked network, which is crucial for achieving high ionic conductivity due to the resulting high amorphicity of the SPEs.