I wonder what the comparison is in J/kg? I could see lithium & capacitor hybrid systems being viable in EVs. The cybertruck's battery housing is full of plenty of deadspace, and if these caps have 1/10th the energy density you could squeeze in an extra 10+kwh of storage. Caps typically have a much longer lifespan, so I could see them acting as a great buffer for the rapid charge/discharge of regen braking.