Li-Po Batteries Explained

If you are interested in radio controlled aircrafts and stuff, you've probably heard about Li-Po batteries. They are very common in RC planes, cars, boats etc. because they have several advantages over other batteries like less weight, variety of form factors, high discharge rates etc. So what are these "Lithium Polymer" battries? How are they different from the common Li-ion batteries (which are found on mobile phones etc.)? And most importantly, are they really "Lithium Polymer"?

To understand these, we must first look at the more common Li-ion battery, and then move on to Li-Po batteries.

Lithium-ion Batteries - The predecessor of Li-Po

Lithium-ion batteries - also known as Li-ion or LIBs - is one of the most common types of rechargeable batteries used in consumer electronics. They are especially popular in portable electronic devices such as mobile phones. This is because they offer several advantages like high energy density, no memory effect, low self-discharge rates etc.

As with all batteries, the lithium-ion batteries also contain an anode, cathode and an electrolyte. Typically, the anode of a Li-ion is made of a carbon material (such as graphite) while the cathode is made from a metal oxide. The electrolyte (which is responsible for the ion exchange between the electrodes) is made of a lithium salt in an organic solvent.

The Structure of a Cylindrical Li-ion Battery

The organic solvent based electrolyte used in these are highly flammable, which could even cause explosions if the battery is misused. Because of this, Li-ion batteries are normally enclosed in hard metal cans which can be cylindrical, pouch like or prismatic in shape. This adds weight to the battery and doesn't allow much variety in shape and size. This is the main reason radio hobbyists who use radio controlled aircrafts and cars, have moved on to Li-Po batteries.

Let's look at the basics of Li-Pos in the next post.

References
http://batteryuniversity.com/learn/article/the_li_polymer_battery_substance_or_hype
http://en.wikipedia.org/wiki/Lithium-ion_polymer_battery
http://en.wikipedia.org/wiki/Lithium-ion_battery

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