The stationary storage market is developing rapidly, with more than 25,000 new installations expected this year. So far, the lithium cell business has been almost exclusively in Asian hands. Yes, there are renowned German or Austrian suppliers of storage units, but their cells entirely come from China, Korea or Japan.
So there is no room for a German manufacturer? Of course there is: The company Litarion, based in Kamenz near Dresden, has started to capture the market for stationary lithium cells. About 170 employees produce and sell their key components: the electrodes and a specialised separator which reliably keeps the cathode and the anode apart. “This separator is made entirely of ceramics,” Fritz Müller, head of sales at Litarion, explains. “It was originally developed back when this company was still owned by Degussa, or later Evonik. Our separator that we call Separion has been used by Li-Tec to build lithium cells since 2007. These in turn are built into the e-Smart. About two million cells have been built here in Kamenz, enough for around 20,000 electric Smarts.”
Turning over a new leaf
The spring of 2015 saw the end of Li-Tec. Degussa had already been taken over by Evonik, but the corporation left the market for lithium cells. In Mai 2015, the patents and the machines for producing the cell components were passed on to the Canadian battery manufacturer Electrovaya, who then proceeded to breathe new life into the factory and re-start it under the name Litarion. “Here we build the components for our Litacell LC-40 lithium cells which produce 40 ampere hours,” Fritz Müller says. “We build the electrodes and the separator. The cell is completed in China, according to Litarion’s specifications and permanently monitored by our engineers. The battery packs in turn are assembled by Electrovaya in Canada and Taiwan.”
In April, the first battery packs with a capacity of two and four kilowatt hours respectively returned to Germany, as both test samples and prototypes. Electrovaya gives a ten-year warranty and indicates the service life as being 9,000 full charging cycles.
Highest quality thanks to e-cars
Before, the company had their greatest success making traction batteries for Daimler-Benz. Now they are looking to start over, among others with stationary storage units. “The run-up to getting lithium cells certified for EVs is very long and take a great deal of effort,” Müller remarks. “That is why we decided to get involved in home storage units, but our cells can also still be found in forklifts or electric busses.”
An important factor is that Litarion remembers the automotive industry’s quality standards, and will now apply these to their home storage or grid storage units. Central to everything is the all-ceramic separator made of aluminium oxide. It passes Hazard level 3 in Eucar’s nail penetration test. Separion is no polyolefine with a ceramic coating, as it is common in many lithium cells, but rather a non-woven polymer (PET) that soaks up the ceramics in such a way that after drying, Separion is 80 percent ceramics and only one fifth PET fibres. If a nail penetrates the cell, it will not catch fire or explode like a Molotov cocktail.
Very heat and nail resistant
And the separator has a number of advantages: “On the one hand, it is strongly impregnated in electrolytes, it acts like a sponge,” Pia Küsgens, doctor of chemistry and in charge of business development at Litarion, explains. “It releases these electrolytes during its service life, which means that the cell lasts very long.” After 9,000 full charging cycles, the cell still achieves about 80 percent of its original nominal capacity.
Also, the Separion does not shrink very much. Only above 250 degrees Celsius does it begin to become soft and lose its form. Other separators made from polypropylene or polyethylene already begin to melt at 130 degrees and start to contract at 100 degrees. At this point, the separator fails to perform its most important function: Sufficiently separating the (graphite) anode from the cathode (consisting a nickel-manganese-cobalt alloy on a thin sheet of aluminium), which will result in a short circuit. The cell will then become hot, leading to what is known as the thermal runaway effect, which has already caused a few batteries to start burning.
Avoiding internal short circuits
That does not happen with Separion: Because the separator retains its shape even at high temperatures, the cells are well-protected from internal shorts and thermal runaway. This proves vital in the dreaded nail penetration test, where a thick steel spike is driven through the cell. Even under such conditions, the cell barely heats up.
The Separion is available in two versions: The P20 which is 21 micrometres thick and the P30 which is 28 micrometres thick. In late May, the output of the cells rose to 45 ampere hours. Litarion’s R&D department is constantly working on improving the Litacell. The next increase in energy density is planned for early 2017. The Kamenz factory has a production capacity of 500 megawatt hours per year; enough for about 2.5 million cells. “For example, we supply system integrators all over Europe,” Fritz Müller says. “We confident that we will be able to enter the market with a very high-quality and safe cell made in Germany.”
The battery packs have an ambient temperature range of minus 20 to plus 60 degrees Celsius. If run continuously at a discharge rate of 1C/1C, free standing batteries reach a temperature of approx. 30 degrees Celsius. If discharging at 5C, which would mean retrieving the battery’s entire energy within 12 minutes, the cells would still have 93 percent of their capacity left. (Heiko Schwarzburger)
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