Electrochemical and Post-Mortem Study of Pyrrolinium-Based Ionic Liquid on a Single-Layer Pouch Cell

Ionic liquid (IL)-based electrolytes have garnered significant interest for enhancing lithium-ion battery (LIB) safety due to their non-flammability, thermal stability, high conductivity, and broad electrochemical stability. We propose novel pyrrolinium-based ionic liquids to enhance lithium-ion mobility and address safety concerns in LIBs. This study investigated LiTFSI in [Pyr13] [FSI] ionic liquid for Li-ion batteries. The cyclic stability and rate performance of single-layer full cells with commercial graphite anode and NMC532 cathode were examined for the electrolyte required per cell and compared to those using a carbonate electrolyte (LP30). Electrolytes containing LiTFSI/[Pyr13] [FSI] exhibited satisfactory rate performance and stable cycling for 100 cycles. The reversible capacity was maintained at over 22 mAh for a cycle period of 100 cycles with an electrolyte loading of 161.8 µL/cm2. These electrolytes exhibited the highest oxidation stability, surpassing 5.3 V compared to that of the Li+/Li reference electrode. Long cycle life of up to 1000 cycles was conducted, showing 80% capacity retention. Post-mortem analysis using scanning electron microscopy (SEM) and micro-Raman spectroscopy allowed observation of LiTFSI/ [Pyr13] [FSI] effects on cathode and anode active particle stability, and reduced formation of secondary reactions between the IL and battery electrodes.