I think molten salt (latent heat) batteries could push the boundaries further as researchers continue to design salt mixtures with lower melting points and high

I think molten salt (latent heat) batteries could push the boundaries further as researchers continue to design salt mixtures with lower melting points and higher and higher delta_k's (economic considerations of compounds included). Though for usage in cars would imply some kind of small/portable vacuum storage tanks and a way to put the heat to work (most likely initially through a steam engine and eventually directly to electricity via advanced thermocouples[0]) [0] https://arxiv.org/abs/1308.5935 https://arxiv.org/abs/1308.5935