Electrochemical energy storage has very well known and finite physical limits. Lithium, one of the most active metals on the periodic chart is king when it comes to moving ions. There won’t be anything better anytime soon. There is a reason the hundreds of billions of dollars put into battery research yields no results. We understand the physics behind modern rechargeable batteries exceptionally well. Remember, common hydrocarbon fuels contain the same energy they always did. We were never able to make a gasoline that contained twice the energy, despite claims in the 1930’s that we were able to do so. What we did instead was to vastly improve engine efficiency. We don’t have that option with 93-95% efficient electric motors.