The surface morphology of the prepared SPEs was characterized by SEM analysis as shown in Figure . Compared to SPE10:1:1, the crosslinked SPE10:1:1-CL shows a dense, smooth surface with a high degree of amorphous nature. The nonuniform and hardly homogeneous texture of SPE10:1:1 transformed into a finer wrinkled feature after crosslinking, which might be due to the increased encompassing of lithium salt and IL, leading to a more homogenous and mechanically robust network. 13,36 Raman spectroscopy was performed on linear SPE10:1:1 and crosslinked SPE10:1:1-CL to investigate and reveal the effect of crosslinking on cation-anion interactions by identifying the states of FSI -in the Raman shift between 700 and 800 cm -1 (full Raman spectra is given in Figure , Supporting Information). The -SNS stretching mode of FSI -in the PCIL- SPEs was deconvoluted into three constituent peaks: free FSI -at 721-723 cm -1 , Li + -FSI -ion pairs at 725 cm -1 , and complexed FSI -anions at 730-735 cm -1 (aggregated ion clusters). As shown in Figure , the SPE10:1:1 (Fig. ) has a low proportion of the free FSI -state (28%) and a high proportion of Li + -FSI -ion pairs (46%). In contrast, the crosslinked SPE10:1:1-CL (Fig. ) is rich in free FSI -anions (53%) and contains very low proportion of Li + -FSI -ion pairs (10%), likely ascribed to the crosslinking of the EO chains that form a crosslinked network with high dissociation ability. The resulting high solvation environment may lead to an increased Li + -EO coordination that can lower the highest occupied molecular orbital (HOMO) level of PEO and therefore benefit the electrochemical stability of the SPE. The SPE10:1:1-CL also exhibited higher proportion of complexed FSI - anions, indicating the presence of aggregated ion clusters. The crosslinked polymer network may have helped to segregate the large, aggregated domains into more uniformly distributed ion clusters to facilitate Li + transport. Therefore, we believe that crosslinking results in enhanced Li + solvation and more uniformly distributed ion clusters which would account for the high ionic conductivity and the potential high electrochemical stability of the crosslinked SPE10:1:1-CL. The electrochemical stability window (ESW) of the linear SPE10:1:1 and crosslinked SPE10:1:1-CL was evaluated in a Li||SS cell by LSV measurements. As shown in Figure , the linear SPE10:1:1 begins to oxidize slowly above 4V vs. Li + /Li, a common behaviour in PEO-based SPEs. In contrast, the crosslinked SPE10:1:1-CL showed high electrochemical stability up to 4.9V vs. Li + /Li (5µA cm -2 current density was used as the cut-off of a current rise ). This indicates its excellent oxidation stability and suitability for use with highenergy 4V-classs electrodes. The enhanced electrochemical stability of SPE10:1:1-CL can be attributed to its crosslinked network, which limits the mobility of linear EO chains and therefore reduces their likelihood of oxidation at the cathode surface as illustrated in the inserts in Figure . Furthermore, the crosslinking changes the coordination environment enhancing more Li + -EO coordination and promoting the formation of FSI --rich ion clusters, as evidenced by Raman analysis. These coordinated ions and surrounding ion clusters likely form a protective layer that prevents further oxidation of EO, synergistically contributing to the enhanced oxidation stability.