Abstract Hybrid electric propulsion is likely to play a more prominent role for regional aircraft with 40+ passengers in the future air transport system with reduced climatic impact. In IMOTHEP, two hybrid-electric regional (HER) aircraft concepts, a conservative and a radical, are developed. Energy dense battery technologies are needed to enable hybrid-electric propulsion of regional aircraft. Furthermore, these batteries need to become commercially available within the planned development time of the new aircraft, i.e. until 2030. This paper will discuss general requirements for the HER battery and aims at providing an overview on the most promising industrial approaches for energy dense battery cell technologies – from advanced Li-ion to all-solid-state – with view of their application in air transport and forecasted availability on the market. Furthermore, results will be presented from the study performed in IMOTHEP on hybrid polymer-ceramic all-solid-state battery electrochemistry that combines lab trials with electrochemical numerical simulation.