Effect of ether group on the electrochemical stability of zwitterionic imidazolium compounds

The cathodic stability of the zwitterionic imidazolium compounds was significantly enhanced by the introduction of an ether group at 1 or 2-position on the imidazolium ring. The cycle performance tests showed that the initial cell capacity was maintained almost unchanged up to 100 cycles at 0.5 and 1 C when 2.5 wt.% of 2-butoxymethyl-1-methylimidazolium-3-propylsulfonate or 2-butoxymethyl-1-butylimidazolium-3-propyisulfonate was added to the model electrolyte (1 M LiPF6 in ethylene carbonate, dimethyl carbonate and ethylmethyl carbonate (1/1/1 v/v/v)). Structures of zwitterionic compounds and their interactions with lithium ions were theoretically investigated. (c) 2008 Elsevier B.V. All rights reserved.