Electrochemical properties for ionic liquid/polymer electrolyte systems

Abstract

The ionic liquid (1‐ethyl‐3‐methylimidazolium hexafluorouphophate) ([emim][PF6]) with different molecular weights of poly(ethylene oxide) (PEO) (MW = 4600; 10,000; 14,000; 20,000; 35,000, and 100,000) has been characterized at various temperatures and compositions using phase behaviors and ionic conductivity. A molecular thermodynamic model based on a combination of the previous theory (BH model) by Chang et al., a nonrandomness theory (NR model), and the Pitzer‐Debye‐Hückel theory modified by Guggenheim (PDH model) considered not only short‐range specific interactions between the polymer and a cation of the ionic liquid (IL), but also long‐range electrostatic forces between anions and cations within the IL. We have derived a new melting point depression theory based on this BH‐NR‐PDH model. We also established an ionic conductivity model, based on the Nernst‐Einstein equation, in which the diffusion coefficient is derived from the BH‐NR‐PDH model. The proposed model takes into account that the mobility of cations in the IL and the motions of the polymer host by expressing the effective chemical potential as the sum of the chemical potentials of the polymer and the IL. To describe the segmental motion of the cation and polymer chain, the effective coordinated unit parameter is introduced. The derived coordinated unit parameter for each state is used to determine the ionic conductivities of the given systems. Quantitative results from the proposed model are in good agreement with experimental data. The results indicate that the molecular weight of the polymer and the surrounding temperature play important roles in determining eutectic points and ionic conductivities of the given systems. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 212–219, 2010

Influences of liquid electrolyte and polyimide identity on the structure and conductivity of polyimide–poly(ethylene glycol) materials

“…Also, once in the polymer, the liquid electrolyte could leach out of the polymer over time, which would also decrease the ion concentration, and thus, the conductivity. Evaporation of the ionic liquid is less likely than that of the phosphoric acid solution because of its better possible association with the polymer from interaction of its hydrophobic components, in addition to its low vapor pressure . Overall, the ionic liquid incorporation is expected to yield a higher ion concentration in the polymer, and the data support this claim.…”

Recent Progress on Magnetorheological Solids: Materials, Fabrication, Testing, and Applications

“…[140] IL has recently been used for the preparation of polymer-IL composite materials due to the high ionic conductivity and the broad electrochemical window. [237,238] The advantages of IL material are utilized in the fabrication of electro responsive actuators, e.g., conducting membranes for thin-film transistors and fuel cells. [5] A dielectric elastomer, which is a well-known electroelastomer, belongs to a favorable class of EAP.…”

Structural and transport studies on polymeric membranes of PEO containing ionic liquid, EMIM-TY: Evidence of complexation

“…The question to be addressed in this paper is whether the ionic liquid EMIM-TY going into the polymer PEO acts as; (a) solvent or (b) electrolyte or (c) both as solvent and electrolyte or (d) an agent to produce "solventswollen" polymer electrolyte [27][28][29] or polymer-salt complex type electrolyte. A few studies are available in literature [30][31][32][33][34][35] which show that the ether oxygen of the PEO-backbone complexes with the ionic liquid cation (EMIM + ) which, in turn, affects the transport as well as phase behaviour. The present paper reports detailed studies on PEO + EMIM-TY based polymeric membranes using DSC, XRD, FTIR and temperature dependent conductivity and viscosity measurements.…”