Stretching Ion Conducting Polymer Electrolytes: In-Situ Correlation of Mechanical, Ionic Transport, and Optical Properties

Abstract

In this work we perform mechanical stretching tests while monitoring optical and ionic transport properties of ion-intercalated semi-crystalline polyethylene-oxide (PEO) electrolytes in-situ. Utilizing ionic liquid (EMIBF 4 ) -PEO electrolytes, we demonstrate a correlation between the degree of crystallinity, which depends on the ion concentration, and the Young's modulus, ultimate tensile strength, and yield stress. Upon stretching solid-state PEO electrolytes, we observe an anisotropic increase in ionic conductivity that we correlate to the optical polarized Raman spectroscopic and microscopic signatures of polymer domain alignment -especially notable in the plastic regime. In-situ Raman spectroscopic studies indicate mechanically-induced ionic transport effects originate from chemical and structural rearrangement of polymer chains, and are independent of the ion species utilized. To emphasize this, we demonstrate the ideas of this study to be similarly transferrable to LiPF 6 and LiI/I 2 intercalated PEO solid-state electrolytes which exhibit similar mechanical-ionic transport response as ionic liquids. This study lays the groundwork for studying the mechanochemistry of solid-state electrolytes, with relevance toward specific electrolyte configurations employed in supercapacitors, lithium ion batteries, and dye sensitized solar cells.A key challenge for future energy storage and conversion systems is the development of fully integrated, mechanical load-bearing device architectures. Such devices require both a solid-state electrolyte and active material coupled to the electrolyte with mechanical integrity under normal operating conditions. 1-4 For this reason, polymer electrolytes have received considerable attention due to the analog between a fully solid-state storage system and a conventional reinforced composite material, where the polymer plays the role of enabling mechanical rigidity and also allowing ions to shuttle between electrodes. Solid-state polymer electrolytes also increase device safety and lower environmental impact since they are air-stable and involve no toxic, volatile species. These solid state electrolytes are central to the development of next-generation energy storage and conversion devices, and in particular supercapacitors, 5-14 metal-ion and metalair batteries, 1,15-21 and dye-sensitized solar cells. 19,[22][23][24][25][26] Each of these device platforms requires an electrolyte permitting ion transport between electrodes, and general understanding of processes in these materials impacts devices capable of fast charge-discharge operation, energy storage capability on par with fossil fuels, and low-cost solar energy conversion devices, respectively. In each of these cases using solid state electrolytes is imperative to ensure a modicum of thermal stability, simplicity in packaging, and most importantly to provide a strong mechanical interface between the active materials.Many materials have been suggested for solid state electrolytes. The majority of these materials involve ion-intercal...

Multifunctional high strength and high energy epoxy composite structural supercapacitors with wet-dry operational stability

“…Polymer electrolytes, such as polyethylene oxide (PEO), poly(ethylene glycol)-diglycidylether (PEGDGE), polyvinyl alcohol (PVA), and polyvinylidene uoride (PVdF) ionic liquid (IL) composites have been lauded as candidates for solid state electrolytes for energy storage systems, such as batteries and supercapacitors. 22,23,[30][31][32][33][34][35][36][37] However, most polymers exhibit extreme environmentally-induced uctuations in ionic transport and mechanical properties, challenging their use for structural systems. Unlike packaged devices, structural energy storage systems must exhibit invariant energy storage performance when subjected to environmental conditions, such as rain or humidity.…”

Structural supercapacitors using a solid resin electrolyte with carbonized electrospun cellulose/carbon nanotube electrodes

“…Therefore, in real applications, the concentration of ILs in the electrolyte matrix should be adjusted to balance the multifunctionality of the structural supercapacitor. This balance can be also achieved by using alternative electrolyte matrices, such as polyethylene glycol (PEG) [32], polyethylene-oxide (PEO) [33], or a diglycidylether of bisphenol-A (DGEBA) [34]. Electrical conductivity increases for carbon fibres produced at higher temperatures [35]; the CF2000 sample is therefore expected to have an increased conductivity compared to CF900, and therefore improved capacitive properties.…”

PAMPS/MMT composite hydrogel electrolyte for solid-state supercapacitors

“…Gel-polymer electrolytes (GPEs) always exhibit high conductivity than that of dry solid-polymer electrolytes. Various polymers [4][5][6][7][8] , such as poly(ethylene oxide) (PEO), poly(vinyl alcohol) (PVA), poly(acrylonitrile), Poly(ethylene glycol) (PEG), poly(vinylidene fluoride) (PVDF) and so on, have been reported to form GPEs with conductivities ranging between 10 -4 and 10 -3 S cm -1 under ambient conditions. GPEs have high swell capacity of ionic or salt solutions to improve their ionic conductivities, and also have good mechanical properties such as flexibility and stretchability.…”

“…The addition of inorganic material improves the proportion of amorphous region in polymer, helps chain segments move easily, meanwhile, increases the interface stability between polyelectrolyte and electrode. 4 The composites from polymer and clays have been researched widely [21] , of which sodium montmorillonite (Na-MMT) shows a better performance in water-absorption, ion-exchange and water-dispersive capacities. As far as the application of supercapacitor is concerned, electrolytes affect the capacitance, operation voltage, energy density and power density.…”