Slashdot Mirror
Making Safer Lithium-Ion Batteries
itwbennett writes "Exploding iPhones may be a thing of the past. Researchers at Taiwan's Industrial Technology Research Institute have developed a new polymer, STOBA (that's self-terminated oligomers with hyper-branched architecture to you and me), that is added to the cathode material inside a lithium-ion battery to keep them from overheating. 'Fires or explosions in these batteries are caused by short circuits,' said Wu Hung-chun, a researcher at ITRI, explaining that even minor mishandling such as dropping the handset could result in damage causing a short circuit. 'The technology is ready for lithium-ion batteries used in electronic devices, mobile phones, laptops,' said Wu. And ITRI has started testing STOBA on electric car batteries."
From the wikipedia article on "Lithium": . Lithium batteries are not to be confused with lithium-ion batteries, which are high energy-density rechargeable batteries.
So I'm thinking it was the old non-Lithium-ion batteries that you could get ribbons of Lithium metal from. TFA is discussion the -ion variant battery.
Karma: Excellent. 15 moderator points expire sometime.
"Horse and buggies may now be a thing of the past due to the new honda civic comeing out this year"
You got that right! I'm finally ready to trade in ol' Bessie.
<Complete your profile by adding a signature!>
We looked at using these kinds of batteries for an engineering applicant for a client, so one of our engineers got a sample package of different sizes and shapes of batteries along with a handy CD of what you could and could not do with them. Unfortunately, the application involved possibly putting a battery on the end of an armature to power a light, something the disc explicitly warned against NOT doing -- it came with a nice set of exploding battery clips. Our client saw those and promptly refused to carry a cell phone in any piece of clothing attached to his body from there on it. I think his laptop no longer ever rested on his lap, either...
Step 1: Stop manufacturing them in China
Nearly all Li-Ion battery failures (going out with a boom, pop, or fizzle) are a result of inferior materials being substituted in the manufacturing process.
Li-Ion battery cells (the individual cells containing your delicious electrons - millions in a single manufactured cell, several of those in a single packaged battery) are expected to pop.
Over-charge them? Pop.
Drain them too fast? Pop.
Result? Slightly diminished capacity.
Over time, the capacity gets lower and lower.
The trick is they're isolated, and you don't get enough of them popping at once to cause a noticeable failure (flame, explosion, etc.).
But when you have shitty charging circuitry, shitty components measuring and regulating the current and voltage, and shitty material (like fucking paper) inside the thing, yeah, shit's gonna go up in flames.
Ni-MH is the superior fucking choice. But the self-discharge rate is too high for the plebes to accept. They've got ones that sacrifice capacity for a lower self-discharge rate (such as Sanyo's Eneloop design), but Li-Ion is firmly entrenched, unfortunately.
Apparently the polymer (as far as I can tell) undergoes a cross-linking reaction that acts to slow the movement of Lithium ions following puncture of the battery thus keeping the reaction relatively under control.
http://www.itri.org.tw/eng/Research/Focus-Area/focus-sub-area-category.asp?RootNodeId=0301&NodeId=03013&FieldCD=03200
Sigs are too short to say anything truly profound so read the above post instead.
dude... you're harshing my buzz... and I've already got my laptop's battery in pieces....
Anybody want my mod points?
I'll post this preemptively since usually when battery fires are discussed some people insist this is unavoidable if you want a high energy density, but this is not true. Whether batteries can fail catastrophically or not is mainly down to two things:
a)Whether the energy released when a cell fails is sufficient to cause nearby fails to fail, thereby causing a cascade of failed cells.
b)Whether the materials the battery is made of can react violently with materials it is likely to come into contact with when it does fail.
For traditional Lithium ion batteries the answer to both these questions is yes. The temperature necessary to cause a cell to fail is easily within the range of what is generated when a nearby cell fails. Furthermore the lithium batteries and their electrolyte burn quite well upon contact with air, adding even more energy to the reaction.
There's however no principal reason why this has to be the case. As an example if the heat capacity and conductivity of the battery is good enough it is possible to design batteries so that the failure of one cell won't heat nearby cells enough to cause them to fail. Different chemistries also have different activation energies, as an example lithium iron phosphate batteries are much safer for this reason. It is also quite plausible that one might be able to create a battery from a chemistry that doesn't react violently with oxygen.
Many batteries that use a water-based electrolytes qualify for both these criteria. Water has a high heat capacity and doesn't burn in oxygen. Unfortunately such batteries have other drawbacks. In particular while water itself won't burn it is susceptible to electrolysis at typical battery voltages, producing flammable hydrogen.
...they're full of extreme awesomeness.
And when that comes into contact with the anti-particle of awesomeness, the average iPhone user, they annihilate each other, releasing enormous amounts of energy.
Have gnu, will travel.
The additive is usually in the separator that keeps the lithium and cathode apart (which you want to do). When the battery overheats the separator breaks down and disables the battery, this has been used where I work for over 20+ years, and is in no way new tech. Putting the same thing in the cathode is like putting a guard rail on the very edge of a cliff instead of 15-20 ft from a cliff, it may stop small shorts that slowly develop in the battery, but a major short, or hole in the separator will melt down and become quite dangerous before the cathode is even involved. Plus, how hot before this effect happens? Cathode is heat treated at over 650F, I sure hope it doesnt take that much to trigger this new substance.
Im ok..
In the rc car world, the two major types of batteries in use are lipo (lithium polymer) and nimh. Nimh has less energy density, self discharge, and requires some rest after discharge still to retain full capacity when charged. I run nimh due to reasons I won't go into, but I have my eye on lifepo4, or lithium iron phosphate. They are not only more robust than traditional li cells, they go off in much the same fashion as the batteries mentioned in the article. The disadvantage to them, and why they aren't 'the thing' in rc cars is that they have a voltage disadvantage. Given the strict regulation of motors in spec class racing, a voltage disadvantage is a huge issue. In other applications, where you could pick whatever voltage and number of cells to use, these batteries are awesome. In rc, their voltage makes you pick arranging them in series at a voltage level that is a disadvantage or adding another cell and making yourself have a huge advantage -- ie, their acceptance isn't based on technical merit but existing standards in racing.
Can't be, because there is no charge for awesomeness.
"It's such a fine line between stupid and clever" -- David St. Hubbins, Spinal Tap
You can buy pure lithium from chemical supply shops. Most people buy batteries to use as batteries. And you can experiment with potentially dangerous compounds and still be safe about it. The danger isn't the fun part. If danger is what you're after then go play Russian Roulette or go streaking across a busy freeway. Having your electronics ruined by a defective battery is neither fun nor entertaining. And the normal risk of it happening is too low to be exciting even if you are looking for danger.
Also, elemental mercury ingested (or injected intravenously) is normally not that dangerous except in cases of chronic exposure, as only 0.01% is actually absorbed by your gastrointestinal tract. It's inhalation of mercury vapors that is dangerous as even small quantities inhaled can cause acute toxicity. But even without experiencing acute mercury poisoning, its cumulative nature can still cause subtle negative health effects (such as higher chances of having children with birth defects in the case of women).
Yeah but most meth cooks are also high school chemistry teachers. You do your cooking on the side and keep your reagents at work with the kids.