Abstract
Ionic liquid has relatively high conductivity at room temperature and good electrochemical stability. Ionic liquid polymer electrolytes have some advantages of both ionic liquid and polymer. In this work, 1-alkyl-3-(2′,3′-dihydroxypropyl)imidazolium chloride (IL-Cl) was incorporated into waterborne polyurethane chain to composite all-solid-state polymer electrolyte matrices. The structure, thermal stability, mechanical property and ionic conductivity of the matrices were investigated by Fourier transform infrared spectroscopy (FTIR), thermogravimetric Analysis (TGA), tensile measurement and electrochemical impedance spectroscopy (EIS). The results demonstrated that when the content of IL-Cl was 14 wt%, the mechanical property of film was optimized, with a maximum tensile strength of 36 MPa and elongation at break of 1030%. In addition, as for the film with IL-Cl content of 16 wt%, its oxygen index value increased to 25.2% and ionic conductivity reached a maximum of 1.2 × 10−5 S·cm−1 at room temperature, showing high flame retardancy and ionic conductivity.
Highlights
Lithium (Li) metal is considered as the most desired anode for next-generation rechargeable batteries because of its high theoretical specific capacity of 3860 mAh·g−1 and lowest electrode potential (−3.040 V vs. standard hydrogen electrode) [1]
IWPU reached the maximum value of limiting oxygen index (LOI) when imidazolium chloride (IL-Cl) content was 16%, which was consistent with the results of TG
The results of mechanical property of IWPU films were improved a lot by adding IL-Cl, with tensile strength reaching 36 MPa and elongation at break increasing to 1106%, showing great flexibility
Summary
Lithium (Li) metal is considered as the most desired anode for next-generation rechargeable batteries because of its high theoretical specific capacity of 3860 mAh·g−1 and lowest electrode potential (−3.040 V vs. standard hydrogen electrode) [1]. The whole system benefits from these two-phases since that the hard parts afford spacial stability and the soft phases are conducive to good ionic conductivity [9] Due to this unique structure, WPU has been identified as a potential candidate polymer matrix for solid polymer electrolytes (SPEs) recently [10]. Polymers 2020, 12, 1513 prepared comb-like nonionic WPU based SPEs with ionic conductivity reaching 5.44 × 10−6 S·cm−1 when the electrolyte contained 15 wt% LiClO4 at 40 ◦ C and SPE15 possessed a wide electrochemical stability window of 0–5 V (vs Li+/Li) and thermal stability at 140 ◦ C [11]. As we know, the chemical combination of ionic liquid and WPU has little been reported yet Based on these considerations, the WPU-ionic liquid membranes were investigated for the first time as polymer electrolytes matrices for all-solid-state Li-ion batteries. FTIR, particle size distribution analysis, zeta potential analysis, tensile measurement, limiting oxygen index (LOI) and EIS were used to investigate the structure and properties of prepared polymer electrolyte matrices
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