Unveiling a Novel Decomposition Pathway in Propylene Carbonate‐Based Supercapacitors: Insights from a Jelly Roll Configuration Study

This research elucidates novel insights into the electrochemical properties and degradation phenomena of propylene carbonate (PC)‐based supercapacitors at a large‐scale 18650 cylindrical jelly‐roll cell level. Central to our findings is the identification of 2‐ethyl‐4‐methyl‐1,3‐dioxolane (EMD) as a hitherto undocumented decomposition by‐product, highlighting the nuanced complexity of PC electrolyte stability. We further demonstrate that elevated operational voltages precipitate accelerated electrolyte degradation, underscoring the criticality of defining the operational voltage window for maximizing device longevity. Employing advanced analytical techniques, including gas chromatography‐mass spectrometry (GC‐MS), this study meticulously analyzes electrolyte decomposition mechanisms. The outcomes offer pivotal insights into the operational constraints and chemical resilience of PC‐based supercapacitors, contributing significantly to the optimization of supercapacitor design and application. By delineating a specific decomposition pathway, this investigation enriches the understanding of electrochemical dynamics in supercapacitor systems, providing a foundation for future research and technological advancement in energy storage devices. Using a jelly roll setup and GC‐MS/DEMS, we detected 2‐ethyl‐4‐methyl‐1,3‐dioxolane (EMD) in PC‐based supercapacitors. EMD, undetectable below 3.3 V, increased significantly at 4.1 V, indicating an oxidative ring‐opening of PC and a unique decomposition mechanism influenced by the 18650‐cylindrical configuration.