Square lithium-ion battery is the most common lithium battery in daily life. It has many models and is widely used in MP3, MP4, mobile phones, model airplanes and other products.

Square lithium-ion batteries are divided into two types: metal shell package (silver white hard shell) and aluminum plastic shell package (gray white soft shell, which can be scratched with fingernails). The metal case encapsulates lithium ion battery or liquid lithium battery, and the aluminum plastic case encapsulates lithium ion polymer (polymer) battery (Lithium ion polymer battery). The chemical materials and electrochemical characteristics used by these two batteries are similar. The main difference is that the lithium-ion polymer battery uses some colloidal substances to help the battery plate fit or absorb the electrolyte, reducing the use of liquid electrolyte. The amount, so that the packaging of the battery can be changed from a metal shell to an aluminum plastic shell.

The shell of the metal case lithium battery is the negative electrode, and the positive electrode is on the protrusion on one side of the battery; the positive and negative electrodes of the aluminum-plastic case lithium battery are two plates on one side of the battery, and the shell is an insulator.

For square lithium-ion batteries, the model number is generally 6 digits. As shown in the table below. The first two digits are the thickness of the battery with 1 decimal place; the middle two digits are the width of the battery; the last two digits are the length of the battery. The unit is mm. For example, a 606168 lithium battery has a thickness of 6.0 mm, a width of 61 mm, and a length of 68 mm. (Note: Due to the different packaging methods adopted by each battery manufacturer, the capacity of the same type of square lithium-ion battery varies within 300mAh)

The nominal voltage of a square lithium-ion battery is generally 3.6-3.7V, and the charging termination voltage is generally 4.2V.