Grid-scale renewable energy need not be--indeed, should not be--primarily chemical batteries. A simple way to store a lot of energy is to use the energy to pump water into a reservoir, then you have hydro power available when you need it. A lot of such clever technologies are in the pipeline in various stages from invention to prototype to pilot deployment and even full deployment. So let's not get hung up on Musk's piles of li-on cells (which have their place too).