Thank you! Is it safe to say you want the wires transmitting the power to be cold, ideally, but the battery itself not necessarily so? (Thinking about the electric grid, etc here as well.)
Indeed, pretty much any conductor (that carries high current) would be more efficient (lower resistance) at lower temperatures. So the losses in the cables would be lower. However, that's a tiny part compared to the temperature needed for the battery chemistry to be efficient on its own.