Energy Storage Systems
The energy storage systems research unit in the Insitute for Nanotechnology (leader: Maximilian Fichtner) consists of a multidisciplinary group of researchers combining chemists and physicists, experimental and theoretical research.
An increasing fraction of renewable energies is expected to contribute to the global energy demand in the future and energy storage systems are needed for an efficient use of discontinuous sources such as wind and solar power. In this context, nanostructured architectures employing a 3-D structuring for power storage and conversion (batteries, supercapacitors, hydrogen storage materials, fuel cells, photovoltaics) provide many advantages over existing technologies to minimize power losses, improve charge/discharge rates, and enhance energy densities, because functional units in these architectures consist of interconnected ~10 nm domains and mesopores (10-50 nm), for example. In this regard, nanoscience and nanotechnology offer promising approaches as all the elementary steps of energy conversion (charge transfer, molecular rearrangement, chemical reactions, etc.) take place on the nanoscale.
For practical reasons, it is one of the favourable options to store energy in electrical and chemical storage devices such as batteries, supercapacitors and hydrogen storage systems.
One of the main problems in the development of hydrogen driven cars is the storage of hydrogen on board of the vehicle. First storage tanks on the basis of conventional cryo- and high pressure vessels are available. However, their storage capacity is not sufficient to reaching the international targets for 2010 in this field (6 mass% H in the system) and there are safety issues related with a 700 bar tank. Only metal hydrides have the physical potential to reach the targeted storage densities at the moment.
The group at the INT works on the development of novel solid storage materials for hydrogen. They are based on nanocomposites which mainly consist of a hydrogen carrier material (i.e. complex metal hydride) and dopants with catalytic function. Recently, additional aspects such as upscale production, system integration and safety tests have been integrated in the working program. System integration and safety tests have been performed in collaboration with other institutes (IKET, IMVT) of the HyTecGroup.
The work on batteries focuses on the development of nanostructured cathode materials for Li ion batteries based on reactive nanocomposites for example. The aim is to develop materials with gravimetric energy storage capacities that are considerably above the ones of current battery materials (i.e. approx. 250 Wh/kg). Targeted properties are the energy capacity, the power density, the cycling stability, and the sustainability of the materials.
A non-nucleophilic electrolyte was synthesized from standard chemicals which can be used in-situ. It shows a stripping/plating efficiency > 99% and has an unprecedented electrochemical stability window of 3.9 V. The electrolyte is compatible with a sulfur cathode and it opens the door to the development and application of new high voltage cathodes for Mg batteries (see also Zh. Zhao-Karger, X. Zhao, O. Fuhr and M. Fichtner, RSC ADVANCES 3 (2013) 16330-16335).
Our paper "Small Ti clusters for catalysis of hydrogen exchange in NaAlH4" from 2003 in Nanotechnology has recently been awarded as one of the TOP 25 papers of the journal of the last 10 years.