Well, not quite batteries, but supercapacitors. http://www.bris.ac.uk/news/2018/february/supercapacitor.html Those stupid enough to be taken in by the Estor scam will think "We've been here before!" but these devices seem to be a trifle more plausible. They have at least demonstrated them actually working and they seem to be one or two orders of magnitude better than existing double layer capacitors. One really nice feature of capacitors as energy stores is that they provide a very simple and accurate way of knowing how much energy you have left. It is proportional to the square of the voltage. All you need is a voltmeter, suitably calibrated. In terms of energy density, they seem to be comparable with Lithium batteries, but how they tolerate high and low temperatures, vibration, and other conditions experienced in cars is as yet unknown, as is cost. And safety is a further potential showstopper, so I'll believe it when I see it. I don't know what it will mean to Mr Musk's enormous battery factory though. Perhaps he can easily turn it over to an enormous supercapacitor factory very easily. We shall see.