Lithium-ion batteries, or Li-ion batteries, are different from regular lithium batteries because the Li-ion batteries are rechargeable. It's the type of battery typically used today to power laptops, cell phones and other devices. The lithium-ion batteries are divided into two sides by a perforated layer called an electrolyte. The lithium ions pass through the electrolyte, creating an electric current. If tiny bits of metal get stuck in the electrolyte's perforations, the battery can overheat and combust. Lithium ions passing too quickly through the electrolyte can also cause the battery to overheat.

Working of Lithium Ion batteries:

The lithium-ion cell has a structure with a positive electrode layer, usually of lithium cobalt oxide; a negative electrode layer made of a specialty carbon; and a micro-perforated separator layer. The sheets are submerged in a solvent that acts as the electrolyte.

The separator is a thin sheet of micro-perforated plastic that keeps the negative & positive layers from contacting while allowing the Lithium ions to pass through. The battery is charged by sending ions from the positive layer to the negative layer.

When a device uses battery power, the ions pass from the negative layer through the separator to the positive layer.

If the separator layer is damaged, whether during manufacturing or when mishandled, it can allow contact between negative & positive layers, which rapidly generates heat. This can cause electrolyte to expand rapidly & make the battery explode or ignite.

Advantages

• Very low profile - batteries resembling the profile of a credit card are feasible.
• Flexible form factor - manufacturers are not bound by standard cell formats. With high volume any reasonable size can be produced economically.
• Lightweight - gelled electrolytes enable simplified packaging by eliminating the metal shell.

• Improved safety - more resistant to overcharge; less chance for electrolyte leakage.

   

Limitations

• Lower energy density and decreased cycle count compared to lithium-ion.
• Expensive to manufacture.
• No standard sizes. Most cells are produced for high volume consumer markets.

• Higher cost-to-energy ratio than lithium-ion.

   

Applications

Lithium-ion batteries are widely used in the area of mobile phone, cordless phone, laptop, backup power source, UPS, power tools, digital products, etc. Li-polymer batteries could be used in even more applications because of the changeable shape, such as bluetooth, toys, aero modelling, GPS, etc.