The Technical University of Munich, Institute of Astronautics is conducting a test campaign at very low temperatures. The first results are very promising. The following graph shows a capacity test of a 18650 cell from 0 °C up to -50 °C.

The graph clearly shows that even at -20°C there is very little capacity loss, whereby one must keep in mind that the energy is not lost but will be recovered as the cell slightly heats up when drawing current. This allows even to start engines at -40°C by pulsing the batteries until they reach -30 °C, at which point enough energy is available.