Process for the preparation of perfluoroalkylcyano- or perfluoroalkylcyanofluoroborates

An electrolyte comprising a compound of formula III

• Ma+[B(Rf)(CN)x(F)y]a− III,
• where
• Ma+ is a lithium, potassium, sodium, caesium or rubidium salt,
• Rf denotes a linear or branched perfluorinated alkyl group having 1 to 4 C atoms, C6F5, C6H5, partially fluorinated phenyl, or phenyl which is mono- or disubstituted by a perfluoroalkyl group having 1 to 4 C atoms, where the perfluoroalkyl group is selected independently of one another,
• a is 1, x is 1, 2 or 3, y is 0, 1 or 2 and
• x+y is 3.

The electrochemical cell containing a compound of the formula III

• Ma+[B(Rf)(CN)x(F)y]a− III,
• where
• Ma+ is a lithium, potassium, sodium, caesium or rubidium salt,
• Rf denotes a linear or branched perfluorinated alkyl group having 1 to 4 C atoms, C6F5, C6H5, partially fluorinated phenyl, or phenyl which is mono- or disubstituted by a perfluoroalkyl group having 1 to 4 C atoms, where the perfluoroalkyl group is selected independently of one another,
• a is 1, x is 1, 2 or 3, y is 0, 1 or 2 and
• x+y is 3.