Battery Technology—Theory and Practice
As William Pentland reports at Forbes, there is a new type of battery on the horizon: the lithium-air battery. He refers to a new study published in Science by T. Liu et al. 
Pentland calls it a “breakthrough” and, therefore, thinks that gasoline-powered engines are doomed, though perhaps not now, nor soon—or ever. A similar report at the phys.org website has the title “New design points a path to the ‘ultimate’ battery.”
What’s New?
In his report, Pentland claims that lithium-air batteries have a theoretical energy density limit of roughly 11,000 Wh/kg. As Wikipediaexplains, that high energy density results from not requiring an oxidant within the battery itself, instead it is taking oxygen from the air. However, the graph accompanying Pentland’s glowing report, while certainly interesting, shows only a roughly 10-fold increase (in theoretical) capacity to approximately 3,000 Wh/kg for a secondary (rechargeable) battery. Undoubtedly, achieving that alone would be an enormous advancement. You can see it for yourself in their graph, below:
The futuristic lithium-air battery technology promises a quantum leap forward relative to current actual technology. The big question then must be how likely it is that the new air-battery system can be designed and produced for common applications.
The Second Problem
Many systems (not just batteries) work reasonably well with ultra-pure materials under special conditions of temperature or pressure. For example, the whole fuel cell technology with hydrogen as energy carrier is highly dependent on that. Even minute traces of sulfur-containing compounds or other impurities are quick to render the catalyst and consequently the whole system inoperative.
The new type of battery technology is said to require high purity oxygen to function, not something you get in real air, even at remote sites with a pristine environment, much less in traffic along congested roads.
Theory and Practice
In short, there is a long road between laboratory experiment and real life applicability of any such development. In most cases, the technological difficulties and purity requirements are too great to ever achieve any practical or cost-effective use for civilian applications.
A few years ago, the idea of “super-capacitors” for electric power storage was hot. In theory they could store your car’s entire gasoline energy equivalent in an even smaller space compared to the size of a common fuel tank. Based on the (theoretical) limit of monomolecular layers of charged and dielectric materials, patents were granted and great-sounding “forward-looking” company statements promised phenomenal electricity storage system energy-density breakthroughs to be just around the corner. We have not heard about such capacitors for several years now.
As with most such claims, theory and practice are miles apart. So, better don’t junk your gasoline-powered car yet!
Dr. Klaus L.E. Kaiser — Bio and Archives
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