I heard a programme on R4 a couple of years ago regarding electricity storage in cars & phones etc. The main issue was the materials used to make the batteries, which weren’t really up to the job these days. Traditionally money had been spent on improving the product, but not the batteries.
Some solutions were to improve charging time by using a super capacitor that would take the initial charge and gradually trickle it in to the battery for use. They also had a car designer from a Japanese manufacturer talk about what they’d been looking in to. One idea was to use the paint, or car body to store power. They’d managed to store some power, but not yet learnt how to store enough to be of any use. The point is, lots of avenues are currently being explored so there is hope.