Q: Why do rechargeable batteries lose their storage capacity over time?
A: In rechargeable lithium-ion batteries - the most common type, used in things like laptop computer batteries and cell phone batteries - one of the two electrodes is graphite, a form of pure carbon consisting of sheets of carbon atoms.
Lithium ions are forced between the carbon sheets when the battery is charged and come back out again when the battery is discharged, explains Robert Hamers, a Wisconsin Distinguished Professor and chair of the UW-Madison chemistry department.
"The first few times that a battery is charged, a chemical reaction occurs on the graphite, forming a thin protective layer," Hamers says. "Over time, this layer slowly becomes thicker and eventually begins to block the flow of electrical current needed to charge the battery, degrading the performance."
A second reason the storage capacity diminishes is physical wear of the graphite itself, he adds. "There is a large volume change as the graphite expands and contracts. Over time that causes the graphite to flake and small particles to break off."
In nickel-metal-hydride batteries, the second-most common rechargeable battery, a small amount of water helps carry electrical charges between the two electrodes. Each time the battery is charged or discharged, side reactions convert some of the water to hydrogen and oxygen, which slowly leak out of the cell. When there is not enough water left, the battery dies.
ibm laptop batteries: ibm ThinkPad T22 battery, ibm ThinkPad T23 laptop battery, ThinkPad T40 battery, ThinkPad T41 laptop battery, ibm ThinkPad T42 battery, ThinkPad R31 laptop battery, ibm ThinkPad R30 battery, ThinkPad R50 battery, ibm ThinkPad X31 battery, ThinkPad X40 laptop battery
It looks like you're new here. If you want to get involved, click one of these buttons!