Liquid electrolyte

A liquid electrolyte for a phosphoric acid fuel cell, comprising a base A and phosphoric acid B, wherein:

• the electrolyte has a molar ratio, A:B, in a range of 1:3 to 1:50;
• the electrolyte has an ionic conductivity of 10−6 Scm−1 or more at −30° C.;
• the electrolyte has an ionic conductivity of 10−2 Scm−1 or more at 150° C.;
• the base is a pyrrolidine represented by chemical formula (3):
• wherein R1 is a hydrocarbon group having 1 to 20 carbon atoms or a hydrogen atom, and
• the temperature at which said electrolyte solidifies is lower than −30° C.