Blimey, I doubt if any battery would make you happy. I think all the Lithium chemistry batteries are amazing but I have lived with their predecessors. If you want a longer battery life from your phone, turn off the GPS, dim the screen and don't take as many photos.
If Lithium is a stepping stone where is the next step, the only elements lighter than Lithium are Hydrogen and Helium, good luck with making a battery out of them so when you use something else you will immediately be on the back foot with energy density. Of course Lithium is only one component of a battery so weight saving may yet happen elsewhere but IMHO we will be using Lithium for a good while yet.
