Gel-polymer electrolytes plasticized with pyrrolidinium-based ionanofluid for lithium battery applications

Abstract

In the present study, hexafluoropropylene copolymer (P(VDF-HFP))-based “active” polymer membranes are prepared by entrapping different extent of pyrrolidinium ionic liquid-based nanofluid (ionanofluid). X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared (FT-IR) spectroscopy are implemented to characterize the membranes. The study reveals that ionanofluid improves the electroactive phase nucleation of P(VDF-HFP) and suppresses the membranes’ crystallinity. SEM micrographs and butanol absorption study indicate that ionanofluid improves the electrolyte uptake ability and facilitates forming unified ion-conducting channels within the membranes. The 50 wt% ionanofluid (INF) incorporated gel-polymer electrolyte (GPE) exhibits the highest room-temperature ionic conductivity (2.33 × 10−3 S cm−1 at 25 °C), a high lithium-ion transference number ( $$ {t}_{{\mathrm{Li}}^{+}}\sim 0.6 $$ ), superior electrochemical stability window up to ~ 5.3 V (vs. Li/Li+) and excellent interfacial compatibility with the lithium electrode. The LiFePO4/Li battery comprising INF-based GPE demonstrates good C-rate performance and excellent cycling stability with a discharge capacity of ~ 156 mAh g−1 and ~ 116 mAh g−1 at C/5 and 2 C rates, respectively, and capacity retention of > 95% after 50 cycles at C/5 rate.