Lithium-polymer battery: how it differs from lithium-ion

A lithium-polymer battery (Li-Po, LiPo) is a type of lithium battery in which the electrolyte is a gel or polymer and the casing is a flexible "pouch" instead of a metal cylinder. That means the battery can be made thin and in almost any shape.

Li-Po: a flexible pouch instead of a metal can

In plain words

A classic cylindrical lithium-ion battery is like a tin can: sturdy, but you cannot change its shape. A lithium-polymer one is like a juice pouch: it can be flat, long or curved to fit a thin phone or watch. But the pouch must be protected from punctures.

How it works

It works on the same principle as lithium-ion: lithium ions move between the electrodes.
The electrolyte is held in a polymer or gel.
The casing is flexible laminated foil, not a metal can.
The battery can be made very thin and shaped to fit the device.
Damage or overheating can make the pouch swell.

Thin batteries for thin devices

Where you'll see it

Almost all modern phones, tablets, watches, earbuds and thin laptops use pouch-style batteries, often called Li-Po. Power banks use both Li-Po and cylindrical Li-ion cells (18650, 21700).

Does it matter when buying

For you as a user the difference from Li-ion is small: the care rules are the same. Important: a swollen battery is a signal to stop using the device at once and take it to a service centre. In power banks, Li-Po is often lighter and thinner for the same capacity.

Myths

Myth: Li-Po is a completely different technology from Li-ion. Reality: It is a type of lithium battery with a different electrolyte and casing design.
Myth: Li-Po batteries do not swell. Reality: The flexible casing is exactly what makes swelling visible.

FAQ

Which is better for a power bank - Li-Po or 18650?

Li-Po is thinner and lighter; 18650 cells are often cheaper and tougher.

Why did my battery swell?

Wear, overheating or damage produce gases inside.

Can a Li-Po battery be punctured?

No - it is dangerous and can catch fire.