Lithium ion conducting polymerized ionic liquid pentablock terpolymers as solid-state electrolytes

• Published in: Polymer (Guilford) Vol. 161; no. C; pp. 128 - 138
• Main Authors: Chen, Tzu-Ling, Sun, Rui, Willis, Carl, Morgan, Brian F., Beyer, Frederick L., Elabd, Yossef A.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier Ltd 14.01.2019; Elsevier BV; Elsevier
• Subjects: Batteries; Battery; Bromination; Cations; Conducting polymers; Electrochemistry; Electrolytes; Feasibility studies; Ion currents; Ionic liquid; Ionic liquids; Ions; Lithium; Lithium-ion batteries; Molten salt electrolytes; Multiblock polymer; Polymerization; Propylene; Rechargeable batteries; Solid electrolytes; Stripping; Styrene; Terpolymers; Trifluoromethane; Battery; Multiblock polymer; Ionic liquid
• ISSN: 0032-3861; 1873-2291
• DOI: 10.1016/j.polymer.2018.12.013

In this study, a lithium ion conducting polymerized ionic liquid pentablock terpolymer (PILPTP) was investigated as a solid polymer electrolyte (SPE) for lithium ion batteries. The ABCBA pentablock terpolymer, poly(tbS-b-EP-b-MS-b-EP-b-tbS) (tbS = tert-butyl-styrene; EP = ethylene-r-propylene; MS = 4-methylstyrene), was brominated and quaternized to covalently attach two different cations (methylimidazolium and methylpyrrolidinium) to the C block and subsequently ion exchanged to form two different TFSI-exchanged PILPTPs (MPyr-TFSI and MIm-TFSI; TFSI = bis(trifluoromethane)sulfonimide). Free standing, mechanically stable, transparent SPE films were produced with MPyr-TFSI and MIm-TFSI containing 1 M Li-TFSI/ionic liquid (IL) (IL = EMIm-TFSI or PYR14-TFSI; EMIm = 1-ethyl-3-methylimidazolium, PYR14 = 1-butyl-1-methylpyrrolidinium), referred to as MPyr-TFSI + Li-TFSI/PYR14-TFSI and MIm-TFSI + Li-TFSI/EMIm-TFSI. Both SPEs show promising ionic conductivities, electrochemical stabilities, and stripping and plating stabilities. Specifically, the MIm-TFSI + Li-TFSI/EMIm-TFSI SPE possessed an ionic conductivity of 0.1 mS cm−1 at 28 °C; the MPyr-TFSI + Li-TFSI/PYR14-TFSI SPE possessed an electrochemical stability window of 4.2 V versus Li/Li+ at room temperature; the MPyr-TFSI + Li-TFSI/PYR14-TFSI SPE exhibited stable stripping and plating overvoltage profiles over 500 cycles at 70 °C. These results demonstrate the feasibility of a PIL multiblock polymer as an SPE for lithium ion batteries. [Display omitted] •Polymerized ionic liquid pentablock terpolymers (PILPTPs) for lithium ion batteries.•PILPTPs possess high electrochemical stability and high ionic conductivity.•PILPTPs possess microphase separated morphologies and high thermal stability.•PILPTPs are suitable for solid polymer electrolytes for lithium ion batteries.