German researchers make progress on a long-lasting battery for electric cars

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Battery technology is one of the major hurdles to the mass adoption of electric vehicles, and batteries that lose their capacity are also the scourge of our gadget-filled lives. One potential solution to this problem has recently been announced by a German research center, which claims to have produced a long-life and high-power battery.

The issue with batteries is that they lose capacity and reliability over time as they are charged and discharged. The very chemical reactions that make lithium-ion an effective technology also ultimately lead to its undoing, eventually causing capacity fade and lower rates that kill the battery. This problem is compounded at high temperatures, like those in electric vehicles.

Ford Focus ElectricBut the Center for Solar Energy and Hydrogen Research (its German acronym is ZSW), a non-profit research consortium, says that its newly developed batteries last as long, or longer than, most people own a car, meaning that EV owners would never have to worry about replacing this costly auto component.

When the car and its other parts outlive the battery — which in modern EVs is usually rated to last about 10 years — it can be cost-prohibitive to opt for an electric vehicle. ZSW claims its battery could be charged every day for as long as 27 years, or 10,000 charge and discharge cycles, while still retaining more than 85 percent of its initial capacity. The battery charging time also takes just 30 minutes, a considerable improvement over some EV charging times now, which can range from six to eight hours with a basic charger.

A 10,000-cycle lifetime is a hit out of the current ballpark. Many companies make cells that can cycle 3,000 times, but the higher specific energy of the battery, the harder it is to achieve high cycle life. ZSW does not specify the energy density of their battery. What they do say is that it has 1,100 watts per kilogram; that’s power, or how fast you could accelerate a car with such a battery.

The Details Behind GE's WattStation Electric Car ChargerHowever, that figure doesn’t tell us how far you could drive the car (energy), and is probably not the four-fold improvement on current tech claimed by ZSW (it’s difficult to assess this without knowing the battery’s specific energy density, or watt-hours per kilogram). Because battery performance specifications are coupled, an equally high lifetime could be achieved by a lower energy battery cycling at low rates under ideal lab conditions.

ZSW’s announcement is vague on the details, but at least one report suggests that changes to the manufacturing process have improved the battery’s performance. Last year ZSW scientists published research detailing improvements achieved through manipulating electrode thickness and compacting, and the type and mixing of conductors. The battery space is also crowded with startups trying to come up with enhanced electrode chemistries (here are 13 companies in this field worth watching in 2013).

The prototype batteries from ZSW are of the cylindrical small form 18650 format, the kind used in older laptops and the Tesla Roadster, for example. These batteries typically have a capacity of 2.2-3.4 amp-hours. The capacity of the ZSW batteries isn’t clear, but it may be reasonable to assume it’s not groundbreaking, given that their announcement touts fast charge/discharge speeds (i.e. high power, which is often inversely correlated with specific energy).

Besides electric vehicles, these new batteries could be used for grid storage, and ZSW is planning next to develop larger pouch cells and prismatic, or flat, cells that pack well for applications in phones or cars. ZSW’s battery announcement also coincided with a new industry cooperation agreement signed on May 29 with partners including BMW, Daimler, and Rockwood Lithium.

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