Not all batteries are heavy, yes edison batteries are heavy as are lead acid, ni-cad are lighter ni-mh are too.
Supercapacitors are light
We have been increasing battery capacity per unit of mass for a while and as massive money pours into this it will continue.
More of a problem is a standardized charging infrastructure.
But soon enough the Mr. Fusion breakthrough will change everything.
Fusion power has been 20 years away for the last 50 years . . .
Just drop a banana peel in the hopper.
Nissan Leaf battery pack weighs 700 lb and when new holds as much energy as THREE gallons of gas (weight 21 lb) and takes 11 hours to recharge at 220 volts. So you have the equivalent of a car that holds three gallons of gas and takes 11 hours to fill. Further it costs $8500 to replace the batteries when they deteriorate to the point of uselessness. NO THANKS. You’re welcome to waste your money on something like that I’ll stick with fossil fuel