High performance batteries (especially Li ion or nickel metal hydride accumulators) are a substantial element of the power supply in space systems. The capacity and reversibility of rechargeable lithium batteries depend strongly on the microstructure of the electrodes.
How Nanomaterials Can Improve the Power Density and Durability of Batteries
Nanostructured materials offer improvements regarding power density and durability by control of charge diffusion and the oxidation state on a nanoscale level. As nanostructured materials for electrodes e.g. carbon aerogels, CNT, vanadium oxide or LiCoO2-particles are examined as cathode materials and nanostructured Sn/Sb oxides as anode materials. It has been reported that in lithium ion batteries, a sixfold increase in reversible charge capacity could be obtained by evenly distributed nanoparticles from cobalt, nickel and ferric oxides in the electrode material.
Thin Film Batteries, Thin Film Solar Cells, Deposition Procedures and Thermal Spray Procedures
The increasing miniaturization of electronic components requires flexible batteries integrable into circuits. Here, thin film batteries (in particular Li ion batteries), whose dimensions and power density can be adapted to the respective chip components, offer advantages. For energy generation, thin film solar cells can be integrated directly into the same device. For the production of thin layers with good electronic characteristics, usually complex high vacuum deposition procedures are required. Cheaper and simpler thermal spray procedures could be applied by using nanoscale precursors, which yield high-quality layers due to the increased reactivity of nanoparticles.
Capacitors, Supercapacitors and Nanostructured Thin Film Electrodes
Capacitors represent a further important component for energy storage in space systems, particularly for short-term high power applications (pulsed power applications). In relation to power density, however, capacitors are clearly inferior to batteries. The development of supercapacitors or "nanocaps" aims at a significant increase of power density. This could be realized, for example, by metallic nano-electrodes with ultra thin pseudo capacity, increased internal resistance and capacity. Such nanostructured thin film electrodes are developed at present in a BMBF (Bundesministerium für Bildung und Forschung - the German Federal Ministry of Education and Research) research project with the participation of Dornier GmbH. As electrolytes, self-assembled electrically-charged polymer layers are used.
Using Nanoporous Carbon Aerogels as Electrode Materials in Supercapacitors
Also, nanoporous carbon aerogels, because of their extremely large internal surface, controllable pore distribution and pore diameter, are suitable as graphitic electrode materials for supercapacitors. The electrical conductivity can be increased by intercalation with the nanoparticles of alkali metals.
Using Nanoscale Spinel Structures and Carbon Nanotubes in Supercapacitors
Likewise, nanoscale spinel structures (MgAl2O4) and carbon nanotubes are considered as electrode material in supercapacitors, which, however, are still too expensive for competitive applications. Companies such as Panasonic, Maxwell or Ness already offer supercapacitors commercially, whereby performance characteristics do not correspond yet to those of a postulated "nanocap", which is to be realized approximately by 2005.