Highly conductive, stretchable block copolymer based elastomeric networks for lithium ion batteries

Abstract

The present article entails development of an elastomeric, highly conductive, polymer electrolyte membrane (PEM) network via acrylate functionalization of poly(ethylene glycol) – block – poly(propylene glycol) – block – poly(ethylene glycol) (PEG-b-PPG-b-PEG) as a photocurable macromonomer and subsequent evaluation on electrochemical performance. By mixing as-synthesized macromonomer with ethylene carbonate (EC) plasticizer and lithium bis(trifluoromethane sulfonyl) imide (LiTFSI) salt, homogeneous melt mixtures were obtained over a wide range of compositions. Upon photopolymerization within the isotropic region, the UV-cured ternary mixture remained transparent and homogeneous, forming an elastomeric PEM network. The polymer electrolyte network-based PEM/EC/LiTFSI (20/40/40) exhibited a superionic conductivity level of ∼10−3 S/cm at room temperature; similarly other PEM compositions reached the superconductor level at battery operating temperatures of 40 ∼ 50 °C with improved thermal resistance and high elongation-at-break over 100%. The PEM further reveals a wide electrochemical window (-0.5 ∼ 4.5 V) with reasonably good capacity retention at ambient temperature of about 89%, and Coulombic efficiency of almost 100% after 50 cycles, determined by galvanostatic charge-discharge cycling at the C/3 rate.