Lithium Ion Batteries Power Modern Electronics
As an industry, portable electronics are built on a foundation of lithium ion (Li-on) rechargeable batteries. Cell phones, laptops, and MP3 players would hardly be practical without them. There are four reasons for this.
First, and most obvious, is that they are rechargeable. If we were stuck with only disposable one-shot batteries, mobile operation would be a luxury. Like all rechargeable batteries, Li-on batteries rely on a reversible chemical reaction, with electrons flowing one way during charging and the other way during use. As the name implies, the chemical reactions in Li-on batteries is based on a gel form of the element lithium.
Second, Li-on batteries are dense, meaning they pack a punch, power-wise, so your cell phone doesn't have to be a brick stuffed with large batteries. Rated in watt-hours per kilogram (Wh/kg), the sealed lead-acid batteries in your car deliver between 30 and 50 Wh/kg and are considered "portable" only because your car has wheels; old nickel-cadmium (NiCad) batteries deliver between 45 and 80 Wh/kg; nickel metal hydride (NiMH) batteries can reach 120 Wh/kg; but Li-on batteries can reach 180 Wh/kg.
The choice is obvious (except that NiMH works better in cold weather, and its charging and protection circuits are cheaper to make).
Third, Li-on batteries are relatively eco-friendly compared to other kinds of batteries. NiCad has been largely abandoned because of concerns over the environmental effects of cadmium. NiMH batteries are constrained by the supply of lanthanum. But the lithium for Li-on batteries is abundant in the Andes Mountains of South America, and some predict it will become to Bolivia what oil currently is to Saudi Arabia.
The fourth reason electronics makers love Li-on batteries is they don't have to be funky little cylinders. They can be molded into different shapes, letting device designers be creative.
Li-on batteries also don’t have a memory effect, meaning they don't lose capacity if they are recharged after being only partly drained. (NiMH batteries were famous for that problem.) And they lose power slowly when sitting on a shelf, at a rate of less than 10 percent monthly.
The biggest downside of Li-on batteries is that, like other rechargeable battery technologies, it's become more difficult to pack more power into them. While electronics continue to double in power every other year, battery vendors have only been able to double battery power about every other decade.
In the case of Li-on, improvements have mostly come from making the layers of lithium gel thinner, but that has led to fires and factory recalls when they were made so thin that the batteries shorted.
Labs occasionally trumpet some battery technology break-through, offering many-fold improvements in power density. Jaded insiders say that anything will work in the lab, and they'll just wait for it to appear on the market. On the whole, the wait continues.