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Fraunhofer ISE says 25-Ah silicon-rich pouch cells kept over 83% capacity after 1,000+ cycles at 280 Wh/kg. The 330 Wh/kg figure is a projection, and low cell pressure speeds fade.
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A StrOboBatt pouch cell as shown in the Fraunhofer ISE release. The photo shows the cell format, not the tested 25-Ah silicon-anode cells specifically.
Image: Fraunhofer ISE
Source · Press image from the Fraunhofer ISE newsroom, used for news reporting.
Fraunhofer ISE in Freiburg ran 25-Ah pouch cells with silicon-rich anodes through more than 1,000 full charge cycles, and the silicon-anode cells kept over 83% of their original capacity, the institute said on October 20.
The cells reached 280 Wh/kg at cell level, measured in a non-optimized research format the institute calls PrecISE. That is a lab measurement. The institute expects about 330 Wh/kg in an industrially optimized pouch format, but that figure is a projection and has not been demonstrated.
Fraunhofer ISE measured 280 Wh/kg in a non-optimized research cell; the roughly 330 Wh/kg industrial figure is its projection.
Illustration (AI-generated)
Most lithium-ion cells use graphite for the anode, the electrode that stores lithium while the battery charges. Fraunhofer ISE says silicon has a theoretical specific capacity about ten times higher than graphite. The catch, in the institute's words, is limited cycle life, which has so far held back industrial use.
Project scientist Lukas Dold, who leads battery materials technology and scaling at the institute, says 1,000 cycles at 80% retention or better is considered an important target for silicon-rich anodes. The StrOboBatt project cells cleared it, according to the institute.
The team built 40-layer cells from commercially available electrode foils. The anode combined a silicon-carbon composite with graphite, paired with a nickel-rich nickel-manganese-cobalt oxide cathode. The composite made up 51% of the anode active material. The anodes delivered more than 1,000 mAh/g and more than 5 mAh/cm². The cells were built on a semi-automatic line in the institute's cleanroom.
Silicon swells and shrinks as it takes up and releases lithium, so mechanical pressure matters. At 1,000 kPa of axial pressure the cells kept over 83% of capacity after more than 1,000 cycles. At 300 kPa, usable capacity fell significantly faster, especially at 1C operation, which means a full charge or discharge in one hour.
The institute also reports a growing gap between capacity measured at a low discharge rate and capacity available in regular 1C operation. Its researchers say real-world operating conditions must be weighed alongside pure capacity retention.
The result comes from one research group's test cells, not from a commercial product, and the release gives no timeline for production cells. electrive, which covered the result on October 22, framed it as a step toward more range at the same battery weight in electric vehicles. The release does not say whether the 1,000 kPa test pressure can be reproduced inside a vehicle pack.
