High-Performance and Highly Safe Solvate Ionic Liquid-Based Gel Polymer Electrolyte by Rapid UV-Curing for Lithium-Ion Batteries

Abstract

Utilizing ionic liquids (ILs) with low flammability as the precursor component for a gel polymer electrolyte is a smart strategy out of safety concerns. Solvate ionic liquids (SILs) consist of equimolar lithium bis­(trifluoromethylsulfonyl)­imide and tetraglyme, alleviating the main problems of high viscosity and low Li+ conductivity of conventional ILs. In this study, within a very short time of 30 s, a SIL turns immobile using efficient and controllable UV-curing with an ethoxylated trimethylolpropane triacrylate (ETPTA) network, forming a homogeneous SIL-based gel polymer electrolyte (SGPE) with enhanced thermal stability (216 °C), robust mechanical strength (compression modulus: 1.701 MPa), and high ionic conductivity (0.63 mS cm–1 at room temperature). A Li|SGPE|LiFePO4 cell demonstrates high charge/discharge reversibility and cycling stability with a capacity retention rate of 99.7% after 750 cycles and an average Coulombic efficiency of 99.7%, owing to its excellent electrochemical compatibility with Li-metal. A close-contact electrode/electrolyte interface is formed by in situ curing of the electrolyte on the electrode surface, which enables the pouch full cell to work stably under the conditions of cutting/bending. In view of the excellent mechanical, thermal, and electrochemical performances of SGPE, it is believed to be a promising gel polymer electrolyte for constructing high-safety lithium-ion batteries (LIBs).

A Brief Review of Gel Polymer Electrolytes Using In Situ Polymerization for Lithium-ion Polymer Batteries

“…The solvated ionic liquid-based gel polymer electrolyte (SGPE) is reported, which was prepared by ETPTA, TPO, LiTFSI, and tetraethylene glycol dimethyl ether (TEGDME) [ 102 ]. The high thermal decomposition temperature of SGPE was observed at 216 °C, whereas liquid electrolyte-based polymer electrolyte (LGPE) composed of ETPTA and commercial liquid electrolyte showed a low decomposition temperature of 129 °C.…”

“… ( a ) Demonstration of the in situ and ex situ pouch-cell-powered LED during folding deformation [ 102 ]. Copyright ® 2022, American Chemical Society; ( b ) cross-sectional SEM image of interface between electrode and electrolyte; and ( c ) AC impedance of conventional and integrated ASSLIBs after first and fifteen cycle.…”

Recent advances in designing solid-state electrolytes to reduce the working temperature of lithium batteries

“…The polymer conversion is 99.8%, which eliminates the residue of monomers in the battery and improves the solid-solid interface. 147 Moreover, the synergistic effect of the system during Li + transport results in an ionic conductivity of 1.07 Â 10 À3 S cm À1 and the migration number of lithium ions of 0.62 at 30 1C.…”

Solvate ionic liquid-derived solid polymer electrolyte with lithium bis(oxalato) borate as a functional additive for solid-state lithium metal batteries

“…15,16 Because of a series of merits offered by SIL, a few reports have attempted to employ the SIL [Li(G n ) 1 ]X (X is counter anion) as both the lithium resource and liquid plasticizer to develop advanced SPEs with favorable ionic transport properties and high safety. For instance, Gao et al 17 constructed a gel polymer electrolyte by rapid UV-initiated polymerization with ethoxylated trimethylolpropane triacrylate (ETPTA) as a polymer monomer added into the SIL solution. The obtained SIL-based gel electrolyte exhibited enhanced thermal stability, robust mechanical strength and high ionic conductivity.…”