Part of the issue is not just the density of the fuel but also the fact that the weight remains the same no matter how much of it you use. With gasoline/coal/et

Part of the issue is not just the density of the fuel but also the fact that the weight remains the same no matter how much of it you use. With gasoline/coal/etc. when you use the product it then decreases the weight of the amount of fuel stored, you don't get that loss with batteries so while you get "additional" gains with e.g. aviation fuel the further you are along your trip and the more you've burned, you don't get that with batteries.