New batteries with liquid cathode and air electrode
The energy density of Li-ion batteries has doubled over the last 20 years and has reached almost 0.2 kWh/kg. The potential for further improvement is limited.  However, new batteries with a new concept and the direct oxidation of a light metal with oxygen from air are able to reach an energy density of 1 kWh/kg. Exchangeable electrodes require a liquid fuel, e.g. metal nano particles, liquid metals, liquid hydrides etc. Making use of air as oxidant requires an efficient air electrode adapted to the electrochemical reaction.

Hydrogen production by electrolysis and storage in solid and liquid hydrides
Hydrogen exhibits the greatest gravimetric energy density of all combustibles know today, i.e. three times the energy density of the fossil fuels. The efficient production of hydrogen from renewable electricity requires improved electrolysers using tailored materials for membranes and electrodes. The availability of a safe and effective way to store hydrogen reversibly is a second major issue for large scale use of hydrogen as an energy carrier. Hydrogen storage in solids offers a safe alternative to the technically established storage in compressed or liquid form.

Reaction of hydrogen with CO₂ from the atmosphere to hydrocarbons
The storage of hydrogen in hydrocarbons is very convenient and if the CO₂ is ab-sorbed from the atmosphere to react with hydrogen, the synthetic hydrocarbons are CO₂ neutral. Starting from findings by Sabatier in 1902,  it is known that CO₂ can be reduced by H₂ over a catalyst producing eventually (Fischer-Tropsch) hydrocarbons and water.  If the hydrogen is produced from renewable energy sources by electrolysis and the carbon dioxide is extracted from the atmosphere, the hydrocarbons from such a process represent a CO₂ neutral synthetic fuel.