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A researcher at the Centre for Solar Energy and Hydrogen Research Baden-Württemberg mixes the electrode slurry in the mixer.
© ZSW
Lithium-ion cells
27.05.2013

Cell configuration and small sample series.
© ZSW

Battery operates for more than 10,000 charge cycles

Researchers at the Centre for Solar Energy and Hydrogen Research Baden-Württemberg have developed lithium-ion batteries with a working life of over 10,000 charge cycles. In so doing, they have achieved a new standard in international technology development. As well as the cell configuration, the scientists have also produced a small sample series. The cells are designed as solar power batteries and for use in electric cars.

The lithium-ion batteries developed in the Centre for Solar Energy and Hydrogen Research Baden-Württemberg (ZSW) are among the best in their class in terms of technological development. The high performance cells exceed the international state-of-the-art technology in terms of cycle stability, an important key value for working life duration. Over 10,000 full cycles have been achieved so far. In terms of other characteristic values such as power density, the batteries attain a level which is comparable to the Asian products which have led the market until now.

The ZSW configures the cells, developed the production process and produced a small sample series in 18650 format.

Use in electric cars

Lithium-ion batteries must be able to function in the car for at least ten years without the capacity of the battery pack falling below 80 per cent of the rated value. “After 10,000 charging and discharging procedures, our lithium battery packs still have more than 85 per cent of their initial capacity,” says Dr. Magret Wohlfahrt-Mehrens, head of battery pack materials research at ZSW. The power density of the cells is 1,100 watts per kilogramme, making them competitive at an international level. For electric cars, this means short charge times and good acceleration.

Using more solar power on site

The use of self-generated solar power can be significantly increased with battery storage systems. The ZSW has determined the potential for self-generated power in residential buildings with heat pumps and battery storage systems. With smaller solar energy systems, the amount of self-used solar power increases from 30 to 45 per cent with a heat pump. If a battery is also installed, the level rises to 70 per cent. A heat pump and thermal storage system increases profitable self-use to 1,800 kWh. With a battery with 5 kWh energy used, the figure rises to 2,800 kWh.

Large cells for industry

As a next stage, the researchers at ZSW plan to develop electrodes for large lithium cells in collaboration with industrial partners. “Knowledge of the cell technology we have now demonstrated is a key requirement for the subsequent production of large cells,” says Wohlfahrt-Mehrens. However, further research and development work is needed to put this knowledge into practice in large cells.
The cells were developed in the “Elektrochemie für Elektromobilität” (electrochemistry for electric mobility) joint project, which was funded by the German Federal Ministries of Economics and Technology and for Education and Research.

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Cell configuration and small sample series
Zentrum für Sonnenenergie- und Wasserstoff-Forschung (ZSW)