Liquefied or Supercritical Gases as Solvents for Electrolytes

6 Liquefied or Supercritical Cases as Solvents for Electrolytes For very special applications, where the increased efforts for low temperature and/or pressurized cells are acceptable, liquefied gases, for example, sulfur dioxide or ammonia, can be interesting solvents for electrolytes (see e.g. [3a]). Supercritical fluids show remarkable properties that are very different from other solvents. Detrimental to electrochemistry is that especially the dielectric constant in the supercritical state becomes low. For supercritical carbon dioxide, no supporting electrolyte with sufficient conductivity is known. 

Various fluorinations, which need principally much energy for the generation of the reagent fluorine, are carried out electrochemically in liquid hydrogen fluoride, even in an industrial scale [66]. Owing to the extreme toxicity and the corrosive medium, special precautions are necessary. 

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