The common 18650 lithium battery is divided into a lithium-ion battery and a lithium iron phosphate battery. The lithium-ion battery voltage is 3.7V, the charge cut-off voltage is 4.2v, the lithium iron phosphate battery has a nominal voltage of 3.2V, the charge cut-off voltage is 3.6v, the capacity is usually 1200mAh-3350mAh, and the common capacity is 2200mAh-2600mAh.

Lithium-ion batteries: Lithium-ion batteries are widely used because of their lightweight, large capacity, and no memory effect. Many digital devices use lithium-ion batteries as power supplies, although they are relatively expensive. Lithium-ion batteries have a high energy density, and their capacity is 1.5 to 2 times that of nickel-hydrogen batteries of the same weight and has a very low self-discharge rate. In addition, the lithium-ion battery has almost no “memory effect” and does not contain toxic substances, which is also an important reason for its wide application. In addition, please note that the external lithium battery is generally marked with English 4.2V lithium-ion battery or 4.2V lithium secondary battery, 4.2V lithium-ion rechargeable battery, so users must look at the appearance of the battery block when buying the battery, to prevent the battery type is not seen. The cadmium-nickel and nickel hydride batteries are mistaken for lithium batteries.

Advantage
1. Large capacity 18650 lithium battery capacity is generally between 1200mah ~ 3600mah, and the general battery capacity is only about 800mah, if combined into a 18650 lithium battery pack, then 18650 lithium battery pack can easily break through 5000mah.
2. Long life 18650 lithium battery has a long service life, the normal life cycle can reach more than 500 times, more than twice the average battery.
3. High safety performance 18650 lithium battery safety performance, no explosion, no burning; non-toxic, non-polluting, after RoHS trademark certification; all kinds of safety performance in one go, cycle times greater than 500 times; high-temperature performance, 65 degrees The discharge efficiency is up to 100%. In order to prevent battery short circuit, the positive and negative poles of the 18650 lithium battery are separated. So the possibility of its short circuit has been reduced to the extreme. A protective plate can be added to prevent the battery from overcharging and over-discharging, which also extends the battery life.
4. High voltage 18650 lithium battery voltage is generally at 3.6V, 3.8V and 4.2V, much higher than the 1.2V voltage of nickel-cadmium and nickel-hydrogen batteries.
5. No memory effect It is not necessary to empty the remaining power before charging, easy to use.
6. The internal resistance of the small polymer cell is smaller than that of the general liquid cell. The internal resistance of the domestic polymer cell can even be less than 35mΩ, which greatly reduces the self-consumption of the battery and prolongs the standby time of the mobile phone. It can fully reach the level of international standards. This polymer lithium battery that supports large discharge currents is an ideal choice for remote control models and is the most promising alternative to nickel-metal hydride batteries.
7. It can be combined in series or in parallel to form a 18650 lithium battery pack.
8. A wide range of applications Laptops, walkie-talkies, portable DVD, instrumentation, audio equipment, aircraft models, toys, cameras, digital cameras, and other electronic equipment.

Disadvantage
The biggest disadvantage of the 18650 lithium battery is that his volume has been fixed. It is not very well positioned when it is installed in some notebooks or some products. Of course, this shortcoming can also be said to be an advantage. This is a lithium battery equivalent to other polymer lithium batteries. This is a disadvantage in terms of customizable and transformable size. It is an advantage over some products with specified battery specifications.
The 18650 lithium battery is prone to short circuit or explosion, and it is also relative to the polymer lithium battery. If it is relatively normal, this disadvantage is not so obvious.
18650 lithium battery production needs to have a protection circuit to prevent the battery from being overcharged and causing discharge. Of course, this is a must for lithium batteries, which is also a disadvantage of lithium batteries, because the materials used in lithium batteries are basically lithium cobalt oxide materials, and lithium batteries of lithium cobalt oxide materials can not discharge at high current, safety Poor.
The production conditions of the 18650 lithium battery are high. Compared with the general battery production, the 18650 lithium battery has high requirements on the production conditions, which undoubtedly increases the production cost.