I worked out I could extend the range of a small EV by 120 miles with 250kg of Lead Acid. That's the weight of three adult male humans. Which you can put in the back of a car without breaking it.
Adding weight to an EV doesn't use much more power. It uses more to accelerate, but you get more back from braking. It uses more to go uphill, but you get more back going downhill. When going at a constant speed, the air resistance is what matters, which is unchanged. You just need stronger suspension.
AFAIK we still haven't mastered recycling lithium.