I think you're referring to Molten Salt batteries.... Maybe.
They are quite wisely used in certain fields, and are extremely effective, unfortunately they (currently) only work at very high temperatures, so are unsuitable as the primary energy source for an EV.
http://en.wikipedia.org/wiki/Molten_salt_battery
Maybe in the future - but way off for the time being.
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Re: Who remembers sodium-sulphur?
I think you're referring to Molten Salt batteries.... Maybe.
They are quite wisely used in certain fields, and are extremely effective, unfortunately they (currently) only work at very high temperatures, so are unsuitable as the primary energy source for an EV.
http://en.wikipedia.org/wiki/Molten_salt_battery
Maybe in the future - but way off for the time being.