I don't know a lot about batteries -- it is obvious that weight doesn't change as the charge is depleted, but is there any (even theoretical) reason to think th

I don't know a lot about batteries -- it is obvious that weight doesn't change as the charge is depleted, but is there any (even theoretical) reason to think that batteries can be made much lighter? E.g. any research into very lightweight battery technologies? Maybe supercapacitors could be lightweight?