Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The lithium battery as a source of hope

23.03.2012
Whether energy supply or electromobility – batteries are a key component. At Hannover Messe from April 23-27, researchers will present lithium batteries with improved properties: they‘re quick-charging, pliable, pressure-resistant or optimally cooled.

The future belongs to electric vehicles – the experts are convinced of this. But there are a few challenges to overcome before quietly whirring electric cars can completely replace the combustion engine. One such challenge is the power supply: batteries have to be safe, reliable and reasonably priced.

Promising developments in this area include lithium cells, which offer the highest energy density. These batteries are not just used in electric cars, though – they‘re also in demand for the storage of wind and solar energy, for medical examinations or to propel deep-sea vehicles. Fraunhofer researchers will be on hand to demonstrate lithium batteries for a variety of applications at Hannover Messe (Hall 13, Stand C10).

Quick charging and discharging

If the wind is blowing or the sun is shining, renewable energy sources often deliver more power than consumers need – so a way has to be found to store surplus energy. While lithium-ion batteries can store lots of energy, they also take a long time to charge. Supercapacitors, on the other hand, can quickly store energy, but their energy density is low. Researchers at the Fraunhofer Institute for Silicate Research ISC in the Center for Applied Electrochemistry in Würzburg are now working on developing a battery that combines the benefits of lithium-ion batteries and supercapacitors. Depending on the requirements involved, the scientists intend to produce energy-storage media that they can set either to the high energy density of a battery or to the high output density of a supercapacitor. For example: lithium-ion batteries that charge many times faster than conventional batteries.

Long service life through optimal cooling

Even just a few degrees‘ temperature difference can make a huge difference; this law also applies to lithium batteries. Adding ten degrees Celsius cuts the energy-storage medium‘s life in half. So an ingenious cooling system is indispensable. For electric-car applications, researchers at the Fraunhofer Institute for Solar Energy Systems ISE in Freiburg have developed a well-cooled battery system: the system consists of twelve flat lithium cells with a fluid-fed cooling plate on each side of each lithium cell. To get peak performance from the cooling plates, the researchers have simulated their form and tailored it to the geometry of the individual battery cells.

The effect is impressive: The cooling plates provide largely homogeneous temperature distribution in the battery module while reducing the temperature rise to just a few degrees, even under large loads. As another benefit, the scientists have attached a circuit board to each battery module to create a module-management system. The system monitors the temperature, charge and deterioration of the individual cells in the battery module and transmits the data to the battery system‘s central control unit. For this purpose, algorithms based on stochastic particle filters were developed with the aid of model-based processes.

Researchers at the Fraunhofer Institute for Chemical Technology ICT in Pfinztal rely on air cooling: They stack the individual lithium cells on top of one another, separated by narrow strips of special polymer foam. A fan is used to circulate the air. These strips offer two benefits: for one, they create channels in the interstices through which air can flow and heat can be drawn away. For another, with the cells lying directly atop the foam strips, the design is very stable. Cooling is optimal: the cells are no warmer than the air drawn away from them. Coolant pumps, coolant fluids and heat exchangers are superfluous. Cooling elements account for less than 20 percent of the cells‘ total weight – making the battery well-suited for lightweight construction in the automobile industry.

Flexible and swiveling

Lithium cells are usually rigid and immobile. Yet there is a demand for pliable cells in some applications, medicine being one example. Scientists at the Fraunhofer Institute for Silicon Technology ISIT in Itzehoe have developed the first flexible lithium battery: the battery can bend and twist. But how did researchers accomplish this? “We work with very thin electrodes,“ Dr. Reinhard Mörtel, a scientist at ISIT, reveals. In addition, the cathode, the separator and the anode all contain between one and ten percent plastic as a bonding material. This material glues the individual particles to one another, ensuring formation of the active layers. Researchers used a laminable plastic to make the flexible cells. If the layers are warmed under slight contact pressure, they adhere very tightly to one another and will not separate even if the cell is twisted or bent. One use of the cell is for sleep-laboratory patients: because most people can sleep better at home than in a laboratory, the patients take the measuring equipment home with them. The bending lithium cell permits a supply of current without the annoying cables.

Pressure-resistant, even at 600 bar

For lithium batteries to supply electricity to underwater vehicles at great depths, they must be able to withstand enormous pressure. Researchers at ISIT have come up with a battery that withstands pressures of up to 600 bar – meaning 600 times normal atmospheric pressure. These cells also offer a very high energy density. Researchers used two approaches to achieve pressure resistance: the cells they used are tension-resistant pouch cells. In pouch cells, the anode and cathode are wrapped inside a film from which all the air has been drawn out – not unlike vacuum-packed coffee.

The second approach involves the separator: the separator separates the anode and the cathode from one another to prevent short-circuiting. Usually, these separators are made of a thin layer of fiberglass that mechanical forces can easily destroy: the result is a short-circuit that can wipe out the entire battery. Researchers have now developed a ceramic-reinforced separator that offers considerably more safety. Another benefit: the separator is rollable and can easily be commercially processed.

Improved safety for lithium cells

Safety is an important criterion when it comes to batteries. With lithium batteries, the aim is to prevent short-circuiting. Short-circuits occur if the two electrodes come in contact with one another. Separator layers are designed to keep them apart. But if the lithium ions crystallize to dendrites – tree-like crystal structures of the kind found in snowflakes – these dendrites could pierce the separators. In the future, a new electrolyte will prevent short-circuiting: it contains ceramic elements. They make it more difficult for dendrites to pierce the separator. Another safety benefit: the ceramic structures are flame-proof, making it more difficult to ignite the electrolytes. Some 80 percent of all incidences of damage can be prevented through use of the new electrolyte being developed by researchers at ISC. This is particularly important for lithium batteries with very high energy densities.

Researchers at the recently opened ICT Battery Testing Center are investigating the safety of certain battery types. Are the electrolyte and battery materials compatible? What happens if the electrolyte is exposed to excessive temperatures or other difficult environmental conditions? The researchers are looking into how internal conditions such as a cell‘s chemical composition and layout, and external conditions such as ambient temperature, affect battery quality and battery life.

Contact
Dr. Victor Trapp
Fraunhofer Institute for Silicate Research ISC
Neunerplatz 2
97082 Würzburg, Germany
Phone +49 931 4100-370 Fax +49 931 4100-570 Send E-MailSimon Schwunk
Fraunhofer Institute for Solar Energy Systems ISE
Heidenhofstraße 2
79110 Freiburg, Germany
Phone +49 761 4588-5219 Send E-MailDipl.-Ing. Thomas Berger
Fraunhofer Institute for Chemical Technology ICT
Joseph-von-Fraunhofer-Straße 7
76327 Pfinztal, Germany
Phone +49 721 4640-319 Send E-MailDr. Reinhard Mörtel
Fraunhofer Institute for Silicon Technology ISIT
Fraunhoferstraße 1
25524 Itzehoe, Germany
Phone +49 4821 17-4317 Fax +49 4821 17-4350

Dr. Victor Trapp | Fraunhofer Institute
Further information:
http://www.fraunhofer.de/en/press/research-news/2012/march/the-lithium-battery-as-a-source-of-hope.html

More articles from Trade Fair News:

nachricht COMPAMED 2016 connected medical devices and people
23.11.2016 | IVAM Fachverband für Mikrotechnik

nachricht Successfully transferring Industrie 4.0 into reality
21.11.2016 | Deutsches Forschungszentrum für Künstliche Intelligenz GmbH, DFKI

All articles from Trade Fair News >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

Im Focus: Molecules change shape when wet

Broadband rotational spectroscopy unravels structural reshaping of isolated molecules in the gas phase to accommodate water

In two recent publications in the Journal of Chemical Physics and in the Journal of Physical Chemistry Letters, researchers around Melanie Schnell from the Max...

Im Focus: Fraunhofer ISE Develops Highly Compact, High Frequency DC/DC Converter for Aviation

The efficiency of power electronic systems is not solely dependent on electrical efficiency but also on weight, for example, in mobile systems. When the weight of relevant components and devices in airplanes, for instance, is reduced, fuel savings can be achieved and correspondingly greenhouse gas emissions decreased. New materials and components based on gallium nitride (GaN) can help to reduce weight and increase the efficiency. With these new materials, power electronic switches can be operated at higher switching frequency, resulting in higher power density and lower material costs.

Researchers at the Fraunhofer Institute for Solar Energy Systems ISE together with partners have investigated how these materials can be used to make power...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

UTSA study describes new minimally invasive device to treat cancer and other illnesses

02.12.2016 | Medical Engineering

Plasma-zapping process could yield trans fat-free soybean oil product

02.12.2016 | Agricultural and Forestry Science

What do Netflix, Google and planetary systems have in common?

02.12.2016 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>