They are all lithium batteries and are in two different forms.
902030 is a rectangular lithium battery, the specific size is 9MM × width 20MM × length 90MM, generally used in small, powerful power equipment, usually used in toys, ship models and aircraft models to provide electricity.
18650 battery, 18 indicates a diameter of 18 mm, 65 indicates a length of 65 mm, and 0 indicates a cylindrical battery. Due to the large capacity per unit density, most of them are used in laptop batteries. In addition to the 18650 lithium battery, the stability of the 18650 is very good at work. It is widely used in various electronic fields: it is often used in high-grade glare. Flashlights, portable power supplies, wireless data transmitters, electric warm clothing, shoes, portable instrumentation, portable lighting equipment, portable printers, industrial instruments, medical instruments, etc. So that the current electric car part is also used as the power output of the 18650 battery pack.
The voltage is generally between 3.7 and 4.2V, and some batteries can discharge to a voltage of about 3.4V, but not lower than 2.75V, which will cause permanent damage to the battery.