Imide ions, polymer electrolytes

The first use of ionic liquids in free radical addition polymerization was as an extension to the doping of polymers with simple electrolytes for the preparation of ion-conducting polymers. Several groups have prepared polymers suitable for doping with ambient-temperature ionic liquids, with the aim of producing polymer electrolytes of high ionic conductance. Many of the prepared polymers are related to the ionic liquids employed for example, poly(l-butyl-4-vinylpyridinium bromide) and poly(l-ethyl-3-vinylimidazolium bis(trifluoromethanesulfonyl)imide [38 1]. 

Table 1. Some imide ions and carbanions used in salts to enhance polymer electrolyte conductivity and reduce crystallinity...

There is as yet no consolidated opinion as to the optimum electrolyte for lithium-sulfiir batteries. Experiments with solid polymer electrolyte are described, but aprotic electrolyte in a Celgard-type separator commonly used in lithium ion batteries is applied more frequently. A large number of electrolytes has been studied that differ both in solvents and the lithium salt. The greatest acceptance was gained by lithium imide solutions in dioxolane (or in a mixture of dioxolane and dimethoxyethane) and also lithium perchlorate solutions in sulfone. Dissolution of polysulfides in electrolyfe is accompanied by a noticeable increase in viscosity and specific resistance of electrolyte. It is the great complexity of the composition of the electrochemical system and that of the processes occurring therein that prevent as yet commercialization of lithium-sulfiir electrolytes. 

Single lithium ion conducting polymer electrolytes have been prepared by the copolymerizahon of hthium(4-styrenesulfonyl)(trifluoromethanesulfonyl) imide and methoxy-poly(ethylene glycol) acrylate [117]. The highest ionic conduchvihes for the copolymer electrolytes are 7.6 x 10 S cm at 25 °C and then grow to reach 10 " S cm at 60 °C, at a raho of ethylene oxide to Li+ of 20.5. 

Feng S, Shi D, Liu F, Zheng L, Nie J, Feng W, et al. Single lithium-ion conducting polymer electrolytes based on poly[(4-sty-renesulfonyl)(trifluoromethanesulfonyl)imide] anions. Electrochimica Acta 2013 93 254-63. 

McFarlane DR, Sun J, Golding J, Meakin P, Forsyth M High conductivity molten salts based on the imide ion. In 6th international symposium on polymer electrolytes (ISPE-6), Hayama, Japan, 01-06 Nov 1998. Pergamon-Elsevier Science Ltd., oxford, pp 1271-1278... 

Li L, Wang J, Yang P, Guo S, Wang H, Yang X, Ma X, Yang S, Wu B (2013) Preparation and characterization of gel polymer electrolytes containing N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl) imide ionic liquid for lithium ion batteries. Electrochim Acta 88 147-156. doi 10.1016/j.electacta.2012.10.018... 

Efforts were made to reduce the reactivity of Im toward Al. Other salts that could passivate A1 were used as additives with Lilm, and the results were encouraging.Also, structural modification of the imide anion was made by extending the perfluori-nated alkyl chain and was found to be effective, although at the price of lower ion conductivity. Although Lilm has never been used in any commercial lithium ion devices, it remains an interesting salt to be investigated, especially for the polymer-based electrolytes. ... 

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