I think storage of energy like you say is a really important piece of the renewable puzzle. I see lots of development in thsi area, particularly on the large scale, whilst tesla gets all the headlines for their grid connected Powerwall installations there is lots of progress on other technologies too, such as pumped hydro storage, to molten salt energy storage to fly wheels using magnetic bearings. Whilst these technologies wont necessarily be suitable for your car or phone, what they will do is allow the electricity grid to be powered by more renewables, so at least when you are charging your electric car, you know coal hasn't been burnt in the process.
RE: Batteries play a major role when it comes to clean energy