Polycaprolactone(PCL) solid polymer electrolytes (SPEs) offers a biodegradable sustainable alternative material for SPE battery systems, the interfacial dynamics between PCL and Li metal are insufficiently explored. This study utilizes operando ATR-FTIR spectroscopy to compare the interfacial behaviors of crosslinked (cl) and non-crosslinked PCL5LiTFSI SPEs. A series of electrochemical measurement reveals that the crosslinked network provides better electrochemical performance by enhancing mechanical strength and of the SPEs and stability to Li metal. Key findings from operando measurment results include the formation of localized ordered PCL segments and TFSI- anion redistribution during Li plating/stripping process. Notably, we introduced a novel visualization approach by transforming operando spectra into penetration depth-dependent band ratio maps. This technique effectively captures the dynamic structural evolution and interfacial changes, offering critical insights into the interfacial stability of PCL-based solid-state batteries.