@425a31b8 Well, as you suspect it's not the whole picture, but yes, there are indeed limitations.  There is a lot of work being done to find new chemistries or even mechanisms of storing energy, sever of which do show lots of promise, but none are truly fully developed yet.  That said, markets are *VERY* slow to switch over (look how long it took to get away from NiMH.  Some things still use it!)  Ridiculously slow actually.