Solid polymer electrolytes with ionic liquid

The key to the development of solid polymer electrolytes with ionic conductivities approaching those of their liquid electrolyte counterparts (i.e. 

Pandey, G. R, and S. A. Hashmi. 2013. Performance of solid-state supercapacitors with ionic liquid l-ethyl-3-methylimidazohum tris(pentafluoroethyl) trifluorophosphate based gel polymer electrolyte and modified MWCNT electrodes. Electrochimica Acta 105 333-341. 

DMFC and DEFC fuel cells use a solid polymer electrolyte for ionic transport. However, they use, respectively, liquid methanol and ethanol as fuel instead of hydrogen. During chemical reactions, the fuel (methanol or ethanol) is directly oxidized in the anode. At the cathode, the reaction occurs with oxygen, producing electricity and water as a byproduct (EUis et al., 2001 Garcia et al., 2004). 

Abstract The chapter begins by discussing the characters and composition of polymer electrolytes for electrochromic devices. It then describes the four types of the polymer electrolytes dry solid polymer electrolyte, gel polymer electrolyte, porous gel polymer electrolyte and composite solid polymer electrolyte, their preparation procedures and properties especially ion conductivity of the samples. Finally, new types of polymer electrolytes including proton-conducting, alkaline, single ionic polymer electrolytes and electrolytes with ionic liquids are also introduced. 

An alternative to lithium batteries with liquid electrol5des are those with solid polymer electrolytes. Solid polymer electrodes are generally gel type electrolytes which trap solvent and salt in pores of the polymer to provide a medium for ionic conduction. Typical polymer electrolytes are shown in Table 15.8. 

Similarly to lithium ion batteries, it is intended to use in sodium ion batteries conventional aprotic electrolytes impregnating a porous separator (Celgard), solid polymer electrolytes, and much attention has been paid lately to ionic liquids. As the electrochemical window of sodium ion electrochemical systems is somewhat narrower than in the case of lithium ion systems, the probability of successful application of ionic liquids in sodium ion batteries is rather high. Of liquid electrolytes, NaPFg solutions in pure propylene carbonate (PC) and in mixtures of ethylene carbonate (EC) with diethyl carbonate (DEC), solutions of NaC104 in PC, mixtures of EC-DEC, EC—dimethyl carbonate, and so on have been described. 

Nanofiber can be considered as promising candidate for preparation o f solid or semi solid electrolyte. This is mostly because of the inherent longterm instability of electrolyte used in DSSCs usually consists of triiodide/ iodide redox coupled in organic solvents [42], Many solid or semi-solid viscous electrolytes with low level of penetration to TiO layer such as ionic liquids [43], and gel electrolytes [44] utilized to triumph over these problems. However, nanofiber with may increase the penetration of viscous polymer gel electrolytes through large and controllable pore sizes. 

A goal of polymer electrolyte researchers since the discovery of ionic conductivity in Li salt complexes of poly(ethylene oxide) has been the identification of solid polymer electrolytes which have high enough conductivity to enable the development of solid-state Li batteries with ambient temperature performance approaching that of their liquid electrolyte counterparts. The formidable nature of this challenge is evident when we consider the requirements of polymer electrolytes for such batteries. They include ... 

The similarity in the ionic transport mechanism in organic liquid electrolytes and solid polymer electrolytes is reflected in the ionic transport numbers measured in the two media. Table 3.5 lists the transport numbers for Li in LiC104 solutions in propylene carbonate (PC) and propylene carbonate/dimethoxy ethane (PC/DME) mixtures [26]. The t+ in PC/LiC104 is 0.28 which increases to between 0.40 and 0.50 with the addition of DME. This increase in t+ in PC/DME mixtures may reflect a change in the solvation characteristics of Li, and/or ionic species present, with the addition of DME. It is then possible that a range of cation transference numbers between 0.2 and 0.6 measured in polymer electrolytes is a reflection of the coordination properties of the particular polymer host with Li" and the nature of the ionic species present. 

In addition, the various types of polymer ionics can be easily fabricated into flexible thin films with large surface areas where the ions are free to move and can conduct electricity as in conventional liquid electrolytes. This has opened the challenging possibility of replacing the difficult to handle, often hazardous, liquid solutions by chemically inert, thin-layer membranes for the fabrication of advanced electrochemical devices. Particularly relevant in this respect has been the technological goal of replacing liquid electrolytes in lithium, non-aqueous batteries by a thin film of a solid polymer electrolyte which would act both as electrode separator and as a medium for ionic... 

Polymer Electrolytes. An alternative to the liquid electrolytes is a solid polymer electrolyte (SPE) formed by incorporating lithium salts into polymer matrices and casting into thin films. These can be used as both the electrolyte and separator. These electrolytes have lower ionic conductivities and low lithium-ion transport numbers compared to the liquid electrolytes, but they are less reactive with lithium, which should enhance the safety of the battery. The use of thin polymer films or operation at higher temperatures (60-100°C) compensate in part for the lower conductivity of the polymer film. The solid polymers also offer the advantages of a nonliquid battery and the flexibility of designing thin batteries in a variety of configurations. 

The ionic conductivity of most solid polymer electrolytes is significantly lower than that of the liquid electrolytes. Cells must he designed with thin electrodes and cell components to minimize the internal cell resistance. The total thickness of a cell assembly is as low as 200 fim or thinner. An alternative is to operate at higher temperatures where the conductivity is higher. While this may he acceptahle for electric-vehicle and stand-by batteries, it will not be acceptable for many portable consumer applications. Newer polymer electrolytes are being developed using plasticizers or gel-type polymers. These methods increase the conductivity of the polymers, but since they contain organic solvents, they will be more reactive with the lithium anode. 

Leveque J-M., Estager J., Draye M., Cravotto G., Boffa L. Benrath W. (2007) Synthesis of Ionic Liquids Using Non-Conventional Activation Methods An Overview, Monatsh. Chem., vol.138, n°ll, p>p.ll03-1113 (August 2007), ISSN 0026-9247 Li DY, Lin YS, Li YC, Shieh DL, Lin JL (2007) Synthesis of mesoporous pseudoboehmite and alumina templated with l-hexadecyl-2/3-dimethyl-imidazolium chloride. Microporous Mesoporous Mater., vol.108, n°l-3, pp.276-282, (February 2008), ISSN 1387-1811 MacFarlane D.R., Sun J., Meakin P., Fasoulopoulos P., Hey J. Forsyth M. (1995). Structure-property relationships in plasticized solid polymer electrolytes, Electrochimica Acta, International symposium on polymer electrolytes, vol.40, n°13-14, pp. 2131-2136, (October 1995), ISSN 0013-4686... 

Fujiwara N, Asaka K, Nishimura Y et al (2000) Preparation of gold — solid polymer electrolyte composites as electric stimuli-responsive materials. Chem Mater 12(6) 1750-1754 Fukushima T, Asaka K, Kosaka A et al (2005) Fully plastic actuator through layer-by-layer casting with ionic-liquid-based bucky gel. Angew Chem hit Ed 44 2410-2413 Gao R, Wang D, Heflin JR et al (2012) Imidazolium sulfonate-containing pentablock copolymer-ionic liquid membranes for electroactive actuators. J Mater Chem 22 13473-13476 Gogotsi Y, Nikitin A, Ye H et al (2003) Nanoporous carbide-derived carbon with tunable pore size. Nat Mater 2(9) 591-594... 

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