Lithium-ion batteries, though widespread in mobile computers and telephones, still have grave drawbacks such as limited energy capacity and fast ageing. Lithium-air batteries could be a favourable replacement, in particular in future electric vehicles: Since their functional principle is based on light oxygen structures instead of heavy metallic ion structures, they could store the tenfold amount of energy. An additional advantage is that lithium-air batteries do not need expensive transition metals with limited availability like cobalt, nickel or manganese. However, the lithium-air technology still is less than adequate, with one of the main shortcomings being the poor conductivity of the electrodes. In a collaborative effort with their colleagues from the St. Andrews university, researchers from the university of Graz achieved a decisive success with regard of the latter problem: Instead of carbon as today's usual electrode material, they employed titanium carbide and thus they could improve the electrodes' conductivity and stability dramatically.
The black carbon typically used in lithium-air battery electrodes is associated with a problem: In this battery type, the reaction partner for the electrochemical process is oxygen - but oxygen affects the carbon surface, with side effects that reduce the battery's rechargeability. The researchers for the first time investigated the properties of titanium carbide electrodes - and were astonished by the positive results; this material ensures a "clean" cell reaction and thus increases energy efficiency and operating life of lithium-air batteries. "With these electrodes, the batteries can be operated under higher load and the better efficiency translates into less heat" explains Graz university researcher Stefan Freudenberger.
As the next step, the researchers will increase the porosity of the titanium carbide structure by means of a new synthesis method. This will further improve the energy capacity of this battery type, they hope.