When we talk about rechargeable batteries in gadgets, we almost always
mean lithium ion batteries, or something very similar.
In short, the lithium ion batteries work like this: A positive electrode (cathode), made of non-metallic lithium, is connected to a negative electrode (anode), made of carbon. To charge a battery is to repel ions (electrically charged atoms) of from the lithium cathode over to the carbon anode, where they deposit themselves. The release of these ions later—or more specifically, the current caused by their flow back to the lithium cathode—is where your laptop or cellphone gets its power from.
At its heart, this is a chemical process; charging and discharging are both chemical reactions, and the passage of ions from cathode to anode, or vice-versa, represents a fundamental change in the makeup of each.
Virtually every other kind of battery works on these same physical principles; lithium ion batteries are just some of the best suited for use in consumer electronics. They’re light, compact, hold a hell of a charge, and most importantly, can be charged hundreds of times before deteriorating significantly. They have long lives. But not unlimited ones.
Why They Die
Battery death starts the second they leave the factory. It’s unavoidable and irreversible, and in lithium ion batteries, can totally destroy even a rarely used, mildly charged battery in as little as a few years. With
Saving your battery
Those of us stuck with the slowly expiring batteries of today will have to help ourselves. Luckily, there’s quite a bitwe can do. Lithium ion batteries degrade much more quickly when hot, so keeping a laptop ventilated is vital. (This is as easy as not using a pillow as a laptop table, or placing a bit of folded paper under the rear of the laptop’s base to enhance air flow.)Rechargable batteries also die more quickly if they’re left fully charged, so instead of keeping a laptop plugged in all the time, let it rest a bit, or plug/unplug it through a workday. Accordingly, phone batteries tend to last longer than laptop batteries simply because of how people charge and de-charge them. For the stunning correlation between heat, charge level and battery life, see Battery University’s article here.
constant use (and abuse), a lithium ion’s lifespan can be under two years-less—if losing more than a third of its capacity counts as death. Knowing that batteries work using a chemical process, it’s reasonable to expect some degradation. After all, no chemical reaction is perfect, and all result in some kind of energy loss, often producing unwanted results or substances. Batteries are no different.
“As batteries age, obstacles arise that reduce ion flow, and eventually make them unusable,” says Isidor Buchman, President of battery diagnostics and analysis companyCadex. “There are certain buildups that occur on the electrodes that inhibit ion flow,” he says. This results in a steady decline in performance.
What he’s talking about, mostly, is the gradual degradation of the cathode—the lithium part—by means of slow, unavoidable chemical changes. Repeated subtraction and addition of ions actually alters the structure of the lithium material, making it less receptive to future exchanges—a bit like a rag that’s been soaked and wrung a few hundred times too many. It becomes threadbare, molecularly speaking.
http://gizmodo.com/5681005/giz-explains-why-batteries-die
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