Batteries are classified into the three categories:

1. Electrochemical cells that are commonly used therein;
2. Physical cells, such as solar cells, that directly convert light energy into electrical energy in a semiconductor; and
3. Biological cells, including enzyme cells that use enzymes or microorganisms

Primary battery types branching out from electrochemical batteries include manganese batteries, alkaline batteries and mercury batteries, and are used for general purpose applications whereas lithium-ion (Li) is a type of secondary battery.

While a primary battery is disposable, a secondary battery, also known as a rechargeable battery, can be reused again after recharging.

The most widely used secondary battery is a lead-acid battery which is commonly used in vehicles.

A rechargeable dry cell, NiCad (NiCd) battery, was also introduced, and secondary batteries are advancing toward nickel-metal hydride (NiMH) batteries and Li-ion secondary batteries, all being considered toward being more environmentally safe.