I recently read that A123, the U.S. maker of lithium-ion batteries, is the subject of a takeover offer from Chinese auto-parts-producer Wanxiang Group. Until now, A123 has been a poster child for U.S. green innovation and manufacturing. But, in fact, the battery maker has teetered on the edge of insolvency and, in 2009, was given a $249 million loan guaranteed by the Federal Reserve. “Weak demand for electric cars” has been cited as cause. Wanxiang has a history of sniffing out failing but potentially valuable auto-industry assets in the U.S. and buying them.
It’s interesting that A123 was last located in Waltham, Massachusetts. Not only was the “Waltham watch” manufactured there (the Swiss came and asked to tour the mass-production facility from which sprang the Swiss watch industry), but the very early “Orient” motorcycle was also a Waltham-made product. A lot of the original brick factory buildings remain.
As another indicator of whether or not there is a burgeoning “green industry” in the U.S.—bringing back prosperity by developing and selling era-appropriate technologies—a year ago in August, five large U.S. makers of solar panels went bust, including Solyndra, which had recently received a half-billion-dollar loan guarantee from the Fed.
So-called clean technologies, such as hybrid cars, solar electricity, etc., turn out to be expensive, affordable only by the upper-middles and above. Since it is typically members of that class who research and report the news, they assume everyone lives as comfortably as they do, and so they are able to take seriously such projects as the Chevy Volt hybrid automobile, whose production has been suspended because of low demand.
Electricity does not magically just “come out of the wall”—90 percent of it is generated by combustion of fuels or by nuclear power. Although coal has fallen to around 40 percent of power generation (natural gas has risen to 23 percent in the new era of “fracking”), in round figures, the U.S. produces a billion tons of coal annually. This works out to one 10,000-ton trainload of the stuff being shipped every five minutes.
Electric-vehicle propulsion currently depends on the use of batteries, of which the lithium-ion type, with its many variants, seems to offer greatest promise. The current kinds of lithium-ion battery are based on various kinds of solid electrodes (graphite, lithium-iron phosphate, spinel, etc.), communicating with each other through some kind of liquid electrolyte. A trend has been to give the electrodes a porous structure that increases their surface area so that more li-ions can attach themselves there. Speed of charge/discharge depends on how fast the ions can enter or leave this porous structure.
The lithium-polymer variant uses a solid polymer electrolyte. This can make the battery more compact but speed of ion movement through the solid depends on how thick it is. Keeping the two electrodes separated is necessary to cutting down internal leakage, heat generation and battery deterioration. Li-polymer batteries can be made flexible, so they can be rolled up for tighter packaging.
What are called “3D li-ion” batteries are now being developed. In place of the usual three-layer structure of cathode/electrolyte/anode, the electrodes are like two different kinds of steel wool interwoven, with the solid electrolyte taking the form of a polymer layer deposited to cover the entire surface of one of the electrodes. Because the two electrodes are, in the language of this invention “interdigitated,” the distance between them, separated by the solid electrolyte layer, can be as small as 20 billionths of a meter or .0000008 of an inch. This is .0002 the thickness of a human hair.
As an example of an “interdigitated structure,” consider the human lung, which combines tiny air passages with a total surface area equal to that of a tennis court with an equally extensive network of blood capillaries separated from it by only the thinnest of membranes through which gas exchange takes place by diffusion.
The electrodes of some future 3D battery are planned to be made of silicon nanowires, plated with tin and having a total electrode surface area 10,000 times greater than in present li-ion battery electrodes.
The problem, as you have probably noticed, is that of having a very large amount of charge separated from the opposite electrode by a very thin layer of polymer that must remain perfect and free of pinholes. Prieto Battery, a Colorado R&D operation, says that not only is its contemplated polymer electrolyte layer pinhole-free, it is also somehow self-healing.
I looked at a site on the subject of such thin electrolytes, and it mentioned the risk involved as more and more energy is piled up on one side of an extremely thin layer. Yet these Prieto folks seem confident they can come to market with a Stage One 3D battery in two years based not on nanowires but on copper foam. Further, this concept does not require use of expensive cobalt or platinum, and the only active chemical employed is said to be citric acid, which gives citrus fruits their sharp flavors.
I’ll keep poking into this from time to time.