08/30/2006
Lithium Here and There
I can’t recall the definition of a word making such a splash in the media. Although I planned to write at length about Pluto’s demotion, the print and TV media have more than adequately covered the International Astronomers Union’s fine-tuning of the definition of “planet”. Besides, Pluto itself isn’t aware that it ever was a planet, nor is it aware that a NASA spacecraft is headed its way powered by, of all things, plutonium!
There’s another, more scientifically important astronomical story that hasn’t received such publicity. I worked on lithium batteries for 17 years at Bell Labs but I had no idea there was not enough lithium in the universe. Very soon after the Big Bang, the elements hydrogen, helium and lithium were formed. What I did not know was that much of that lithium has been “lost”. When cosmologists looked at the spectra of very old stars, which would have formed from those early Big Bang elements, they found less than half the predicted amount of lithium. Without that lithium, their Big Bang model for the formation of the elements was in trouble.
Happily, the missing lithium has been found, as reported in the August 10 issue of Nature, by Andreas Korn and colleagues at Uppsala University in Sweden and co-authors in Denmark, Russia and France. These researchers looked carefully at spectra from 18 old stars of different ages in a particular cluster of stars. As a star ages, elements diffuse towards the center of the star and reappear at the surface thanks to turbulent mixing in the star. But not lithium. Lithium turns out not to be a very sturdy element and, as it travels towards the center of a star, it encounters temperatures of over 2.5 million degrees Kelvin. At those temperatures, lithium can’t stand the heat and breaks apart – end of that lithium! So, as a star ages the amount of lithium should decrease. Looking at the old stars of different ages, the researchers confirmed this effect and found the decreases in lithium content were in agreement with a model taking into account diffusion of lithium into the interior of a star.
With the solution of the case of the missing lithium, all is well with the Big Bang. Unfortunately, here on Earth, lithium is causing some unwelcome bangs and fiery incidents. As if we didn’t have enough to worry about with terrorist plots to blow up aircraft or pilots on the wrong runway, could danger be lurking under your fingertips as you sit in your plane with your laptop computer? I’m referring, of course, to those lithium-ion batteries that power most laptops, cell phones, digital music players and the like. Last week’s recall by Apple of 1.8 million lithium-ion batteries added to the earlier recall by Dell 4.1 million laptop batteries. Sony made all the batteries.
Less than 2 years ago, in my column of 12/1/2004, I wrote about recalls of a total of roughly a million lithium-ion cell phone batteries by Verizon and the Japanese company Kyocera. In an article in the August 14 Wall Street Journal, Corey Dade deals at length with more recent lithium battery incidents involving aircraft. One incident occurred in May on a Lufthansa flight about to take off for Munich from Chicago’s O’Hare when smoke emerged from an overhead luggage compartment. A computer case was on fire. After using a fire extinguisher, the crew threw it out a cabin door onto the ground, where the case burst into flames. After the fire department and bomb squad put out the blaze, the culprit turned out to be a laptop with a melted battery of six lithium-ion cells. The owner of the laptop said that he had bought the battery on eBay and that it might not have been built to the laptop’s specifications!
NEVER DO THIS! With any rechargeable battery, especially lithium batteries, never replace the battery with any other than the model supplied or recommended by the computer or cell phone manufacturer. As we’ve discussed before, control of the charging of lithium-ion batteries is critical. Charge them above a critical voltage and they become unsafe. Typically, the lithium- ion battery has a silicon chip in it that limits the voltage and time of charge. Or the computer may have its own charging program. If not, and you put in a lithium-ion battery without the silicon chip, you’re courting an explosion and/or fire.
On the other hand, the Dell and Apple recalls point to another problem as the cause of the laptop incidents. In an article in the August 21 issue of Chemical and Engineering News, Alex Tullo quotes Forrest Norrod of Dell as saying that particles of metal introduced in crimping operations in Sony’s manufacturing process are the culprit. The lithium-ion cells with which I’m familiar are made in a jellyroll fashion. Long strips of a cathode composite and of an anode composite are enclosed in sleeves (or equivalent) of a polymer known as a separator. The separators prevent the anode and cathode from touching each other, which would short circuit the cell. The sleeves of separator/electrode composites are then wound together like a jellyroll.
If one or more metal particle gets into the act, a metal particle or shard can puncture the very thin polymer separator (think Saran Wrap; the thickness is comparable). If this happens, and the metal particle touches both anode and cathode, it’s a short circuit inside the cell. The cell may have a fuse to protect against an external short circuit but that fuse can’t do anything to shut down an internal short. An internal short circuit can generate a spark and/or heat, depending on how “hard” the short is. By “hard” I mean how solid are the contacts of the metal particle with the two electrodes. Ironically, at Bell Labs some of our best, longest cycling lithium batteries had “soft” shorts. A hard short circuit can cause decomposition of organic solvents in a lithium-ion cell and/or can also decompose the oxide cathode material, a cobalt oxide typically. The latter decomposition yields oxygen, great for combustion! Solvent decomposition can yield gaseous compounds that build up pressure and/or react with the oxygen. None of these scenarios is good!
Surprisingly, it’s Sony, the company that introduced lithium-ion batteries to the market over a decade ago, that is having this quality control/crimping problem. Sony reportedly owns up to the problem but is also saying that computer architecture may play a role. This could be a reference to the placement of the battery in some computers close to the hot-running silicon circuitry that drives the computer. Presumably, the heat might hasten any degradation of the battery. Let’s leave that issue to the lawyers!
I can empathize with Sony in its current predicament. I can also feel the satisfaction that the missing lithium researchers must have felt when they found what happened to it. Lithium is not easy to deal with. At Bell Labs, my own experience with lithium was a real roller coaster ride. I’ve probably mentioned in earlier columns my nearly getting fired in my first year at Bell Labs when I abandoned a project involving lithium in either silicon or germanium. I found handling lithium to be too tough, only to end up my career working on lithium batteries for those 17 years! Three times during those years, a particular lithium battery that I co-invented was slated for manufacture, twice by the Western Electric Company and once by a major battery company. Three times the manufacture was canceled, twice after investment of considerable time and money. At the time, it was most frustrating and disappointing but now, in retrospect, I’m happy. It could have been our battery in those recalls!
Allen F. Bortrum
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