I don't think that's true, both volumetric and mass densities for lithium ion batteries are very low (https://upload.wikimedia.org/wikipedia/commons/c/c6/Energy

I don't think that's true, both volumetric and mass densities for lithium ion batteries are very low (https://upload.wikimedia.org/wikipedia/commons/c/c6/Energy_density.svg https://upload.wikimedia.org/wikipedia/commons/c/c6/Energy_d...).