There is two densities to care about when talking about energy sources. Energy density per volume unit and energy density per mass unit. Hydrogen has a very hi

There is two densities to care about when talking about energy sources. Energy density per volume unit and energy density per mass unit. Hydrogen has a very high energy density per mass unit (the highest of the chemical reaction energy sources). But lower energy density per volume than Li. The two figures matter for different use cases, cargo-ships and aviation want to optimize for energy density per mass, while small passenger transport (e.g. scooters, cars...) wants to optimize for energy density per volume. Energy density per mass graph: https://en.wikipedia.org/wiki/Energy_density#/media/File:Energy_density.svg https://en.wikipedia.org/wiki/Energy_density#/media/File:Ene...