Exploring the frontiers of battery technology
Batteries are the key technology for fully-electric and a major component in hybrid-electric power and propulsion systems. However, besides safety aspects, their performance and mass characteristics are crucial for on-board applications. Measures to increase the safety of cells and battery packs typically work very well, mirroring the relatively reliable operation of mobile and stationary applications. Electric vehicles generally outpace comparable combustion-based vehicles in terms of efficiency and energy consumption per distance, but do not match their range or payload capabilities. Hence, the all-dominant question addresses the development limitations of battery technology and realistic targets that may be set for future electric flight with respect to aircraft size and range capacity.
Projected medium-term theoretical specific energies range from 200 to 250 Wh/kg for a lithium battery system, including housing and the battery management system. Current lithium battery developments show reasonable specific energies of up to 350 to 500 Wh/kg at cell level, a factor of 1.5 to 2 larger, compared to today’s cell technology. Latest electrolyte trends reveal potentials for even higher specific energies. Nevertheless, the increase of specific energies for lithium batteries by an average rate of 7 % year-over-year between 1994 and 2010 will not be continued in years to come and is likely to be reduced in the future.
Future battery feasibility studies in the field of fully- or hybrid-electric power systems should focus on the identification of reasonable applications and synergy effects under the given constraints of battery prospects.
- Comparison and outlook: Current state of different electrode materials and reasonable medium-term future potentials for specific energies at cell level, scaled to the 2012 technology level.
- Past and future: Historical development of the specific energy of 18650 lithium cells and future potentials of current electrode materials under investigation, scaled to the 2012 benchmark