Lithium Ion Batteries
Without the lithium ion battery, modern cell phones would not be what they are today: light, portable and able to operate for long periods of time between charges. Compared to other types of batteries, lithium ion batteries emit a lot of power, can be created in virtually any shape, and weigh relatively little. For these reasons, they are used extensively in portable devices such as cell phones, MP3 players, laptops and GPS devices.
Features
A lithium ion battery is usually made up of multiple cells which all contribute to power storage and output. Each cell is itself a small battery. A lithium ion cell is composed of three primary parts: an anode, a cathode and an electrolyte separator. As in an alkaline or lead acid battery, the lithium ion battery has positive and negative nodes. The anode, made of a kind of lithium metal, is the positive node. The cathode, made of carbon (usually graphite), is the negative node. Positively charged lithium ions can adhere to the materials used in both the anode and the cathode, and it is the movement of these ions which allows the battery to both provide energy and receive a charge. Different materials are used to increase the power, longevity and charge times of the battery.
Providing Power
When a lithium ion battery discharges, as when it is powering your cell phone, the ions migrate from the positively charged anode to the negatively charged cathode, releasing energy in the process. The electrolyte separator between them allows the ions to move between the two nodes, but not too quickly. The separator also acts as a thermal layer between the cathode and the anode. If the separator fails, the energy is released all at once, causing the battery to heat up and catch fire or explode.
Storing Power
When you charge your cell phone, the reverse process takes place. As electricity moves through the cell, the lithium ions migrate from the negatively charged cathode to the positively charged anode where they wait for a circuit to be closed, allowing them to release the charge as they return to the graphite cathode.
Dead Cell Phone Syndrome
While they last significantly longer than other types of batteries, lithium ion batteries do not last forever. A typical lithium ion battery will deliver between 300 and 500 discharges before performance begins to degrade. Also, lithium ion batteries, whether in use or not, will age because their components are prone to oxidation. A battery stored on the shelf will begin to degrade after two to three years. Lithium ion batteries are heat sensitive and should not be exposed to high temperatures.
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