A recent study evaluating garnet-type solid electrolytes for lithium metal batteries finds that their expected energy density advantages may be overstated. The research reveals that an all-solid-state lithium metal battery (ASSLMB) using lithium lanthanum zirconium oxide (LLZO) would achieve a gravimetric energy density of only 272 Wh/kg, a marginal increase over the 250–270 Wh/kg offered by current lithium-ion batteries.