Electrolyte for a lithium/thionyl chloride electric cell, a method of preparing said electrolyte and an electric cell which includes said electrolyte

DETAILED DESCRIPTION The present invention provides an electrolyte for an electric cell whose negative active material is constituted by lithium and whose positive active material is constituted by thionyl chloride, the electrolyte containing at least one solvent and at least one solute, said solvent being thionyl chloride and said solute being chosen from the group which includes lithium tetrachloroaluminate and lithium hexachloroantimonate, wherein said electrolyte further includes a complex chosen from the group which includes AlCl.
sub.
3,SO.
sub.
2 and SbCl.
sub.
5,SO.
sub.
2.
In this way, the electrolyte includes aluminum chloride or antimony pentachloride combined with the lithium chloride and a complex of sulphur dioxide with aluminum chloride or antimony pentachloride, but it includes neither an excess of lithium chloride (which, besides, is not soluble) nor an excess of sulphur dioxide.
Advantageous proportions of the ingredients are as follows: for 3 moles of aluminum chloride or of antimony pentachloride, 2 moles of lithium chloride and 1 mole of sulphur dioxide.
In primary cells which contain the electrolyte thus obtained, the delay in the voltage rise is null or negligible even after long periods of storage or rest.
It is possible to add a second solvent such as phosphoryl chloride or sulfuryl chloride to the thionyl chloride, in particular with a view to providing a second plateau at the end of discharge.
The invention also provides a method of preparing the above-described electrolyte.
Several methods can be put into practice, all of which provide the electrolyte in accordance with the invention.
According to a first method, firstly a Lewis acid chosen from the group which includes aluminum chloride and antimony pentachloride, secondly lithium chloride and lastly sulphur dioxide are added to the thionyl chloride in quantities which correspond to the contents required in the electrolyte, the molar proportions being such that there is an excess of said Lewis acid relative to the lithium chloride by a molar quantity equal to that of the sulphur dioxide