Lithium Polymer Batteries: A Review

It's an information age we're living in, and thus, portable electronic devices are a luxury most of us either choose to live with, or have a hard time living without. Thus, we have become a race of people that have large amounts of energy stored in our pockets and on our laps. That luxury has environmental, financial and since they started exploding, personal risks involved. So we at TreeHugger thought it would be good to discuss the next step in power storage technology, the Lithium Polymer battery.

Lithium-ion batteries have taken over the portable electronics industry in the last few years. For every unit of energy they contain, they are lighter, cheaper, and smaller than other kinds of batteries. They don't suffer from the 'memory' effect that gave nickel batteries a bad name, they contain relatively few toxic metals and are fairly simple to recycle.But, in the last year, several battery makers pushed the limits of energy density in Li-ion batteries too far. Li-ion batteries use organic solvents to suspend the lithium ions. In situations where the structure of the battery is compromised, that solvent can ignite and vent from the pressurized battery. The result is a dangerous and toxic fireworks display you can see in a video at the end of this article.

In response to the dangers of packing more power into a Li-ion battery pack, portable electronics makers are turning to lithium polymer batteries. You might see it abbreviated as Li-Po (yes, like the Chinese poet) or Li-poly, or you might see it in it's complete and extended form "lithium ion polymer batteries," they all mean the same thing.

The main advantage of Li-poly batteries that has been discussed in the press recently is their reluctance to explode under duress. They will explode if over-charged, like any other battery, but they can be banged around, punctured, dropped or run over with a car and still not explode.

This desirable ability springs from the 'polymer' in Li-poly. Instead of storing the lithium ions in organic solvents, the ions are held in a non-flammable polymer matrix. But there are more advantages than just the lack of explosions. Li-poly batteries do not require a metal
casing to squeeze the battery's electrodes together so they can be up to 20% lighter than Li-ion batteries. Also, the form-factor of Li-poly batteries is much more flexible than the necessarily boxy or cylindrical Li-ion cells, and they can be as thin as a credit card.

Of course, they come with their disadvantages too. Most important to the consumer market, they are more expensive and they lose capacity faster than Li-ion batteries. But in our eyes, potential environmental concerns are significant as well. Most Li-poly batteries on the market today require some fluoropolymers in the matrix. Fluoropolymers are expensive and difficult to create, requiring a lot of energy and chemicals. And, most troubling, there are currently no good programs in place to recycle lithium-polymer batteries.

As the technology is adopted, we can hope that less resource-intensive materials can be incorporated, that the technology will become cheaper, and that low-risk, inexpensive methods of recycling will be produced. Hopefully, these technological advances will occur quickly, because their increased safety, decreased weight and flexible form factor make them absolutely perfect for use in electric cars.

But, in the meantime, I don't suggest TreeHuggers become early adopters of this technology. They need to be disposed of more rapidly than Li-ion batteries, they can't be recycled, and they contain some truly dangerous and energy intensive chemicals. The new and safer (though lower energy-density) Li-ion batteries should suit the short-term needs of the techno-treehugger.



::Lithium Polymer at Wikipedia
. See also: New Battery Design Charges in One Minute

Tags: Batteries