New compositions of liquid organic electrolytes with working temperatures of up to–50°С were developed for low-temperature primary Li/CF x power sources. Five different compositions of organic electrolytes with a 15-crown-5 (2 vol %) addition and without it were studied on laboratory Li/CF x power sources. 1МLiBF4 (LiPF6) in an ethylene carbonate/dimethyl carbonate/methyl propionate/ethylmethyl carbonate (EC/DMC/MP/EMC) (1: 1: 1: 2) mixture and 1 М LiPF6 in an EC/DMC/EMC (1: 1: 3) mixture each with a 15-crown-5 (2 vol %) addition were found to be the best compositions of organic electrolytes with working temperatures of up to–50°С. The electrochemical tests at 20 and–50°С in the Li/CF x system showed that the 15-crown-5 addition increased the length of the discharge plateau at–50°С three- or fourfold. The mechanisms responsible for the increase in the discharge capacity of the CF x cathode in the presence of a crown ether addition were suggested.