The problem with Li-Ion batteries overheating is that an internal short develops within one of the cells and causes a thermal runaway condition that will typically destroy any nearby cells (or the whole battery).
Typically a short will develop if the battery is over discharged (see
here for a long explanation).
I've had relatively large Li-Ion batteries in my past 3 vehicles now without any issue (23kWh, 8kWh, and now 60kWh)--two of which had/have thermal management controllers to keep temps in line. In all cases the batteries are prevented from discharging too much.