Perfluorinated Single-Ion Li+ Conducting Polymer Electrolyte for Lithium-Metal Batteries

Abstract

Single-ion (Li+) conducting electrolytes with a high Li+ conductivity and transference number (LTN) are promising electrolyte candidates for eliminating the concentration polarization and inhibiting the growth of lithium dendrites in lithium-metal batteries at high power and energy densities. This study presents the synthesis and electrochemical characterization of an AB-type single-ion Li+ conducting polymer consisting of a perfluorinated lithium-salt monomer (A) covalently bonded to a polyethylene glycol monomer (B). An investigation into several plasticizers reveals that ether-based solvents with moderate dielectric constants significantly enhance the Li+ conductivity of single-ion (Li+) conducting gel polymer electrolytes (SIC-GPE) while also maintaining the mechanical integrity of SIC-GPE. The perfluorinated lithium-salt units with weakly coordinating anions provide the advantage of high Li+ conductivity (1.1 × 10–4 S cm–2) and transference number (0.92), while polyethylene glycol units contribute to high flexibility and enhance plasticizer wettability in the SIC-GPE. The interfacial stability and electrochemical performance of SIC-GPE are demonstrated in lithium-metal symmetric cells (maintaining stability for >1300 h at 1 mAh cm–2) and lithium-metal batteries (retaining 98% capacity after 200 cycles).