The scary thing about news is that it is both information and a product for sale. My favorite example is weather reporting, whose original purpose was to tell listeners whether their picnic would be rained out. TV weather has also become a product, competing with others of its kind, so it has to get your attention, as in, “Killer storm grips northeast.” But I look out the window and see light snow, and by morning, we have four inches—all that excitement for nothing.
The same happens with reporting of advances in lithium-ion battery technology. Why? Because just as in politics or sports, the excitement is not what’s actually happening, but in how we feel about it. Electric-vehicle people are rooting hard for their side, and the combustion-engine types are scoffing. Partisanship! Look at all the hits we’re getting!
This morning, a friend sent me apparently sensational news about a German lab’s breakthrough development of a long-lived cell chemistry (Nickel Cobalt Aluminum or NCA) that retains 85 percent of its storage capacity after 10,000 charge/discharge cycles. At one such cycle per day, that translates to more than 27 years’ use in an electric car. Wonderful! Also, a power density of 1100 Watts/kilogram!
I wanted to know what this meant. Should I be impressed? I pulled my growing file of battery information. Hmm, here I find that LTO batteries (those with lithium titanate spinel oxide anodes) have been made to retain 80 percent of original capacity over 9000 cycles and to be capable of up to 4000 W/kg.
Then, I consulted the website, “Battery University,” and found that the battery type with which the German lab worked, NCA, is known for its long life and high specific energy and power, but its shortcomings are lower safety (heat generation during charge/discharge) and high cost (cobalt ain’t cheap).
Okay, so what did the Germans come up with? They made two basic advances. First, recognizing that chemistry proceeds at different rates at cathode and anode, they sensibly made those electrodes of different sizes so that the number of electrons coming out of the anode equaled the number going into the cathode. This greatly slowed the “plating-out” of lithium metal on electrodes that is a source of battery degradation.
Second, they optimized electrode thickness and degree of compaction—tiny granules packed together generate a compromise between maximum surface area (for energy density) and porosity; letting ions flow in or out faster or slower controls power—and found a correct mixing ratio for an effective conduction agent (certain battery types have carbon electrodes made more conductive by platinum metal).
The report said nothing about charging time. Is it 10 minutes? Three hours? That’s kind of important for the electric-vehicle peep.
Bottom line: This is clearly valuable, serious research, but it is not a revolution that will give 350-mile range to electric vehicles in a year or two. The goal of this publicly funded German research is to find an economic way to store large amounts of electric power generated by wind or solar so it can be later used for peak load or at night. It shows the value of testing over ranges of constructional variables to find their “sweet spots.” Doing the science, nailing the details.
If you want more, go to http://www.greencarcongress.com/2013/06/zsw-20130604.html.