The difference between 21700 and 18650 batteries is the size, specified capacity and application area.
1. Various sizes: 18650 lithium battery, diameter 18MM, length (height) 65MM. Usually they are round. The 21700 lithium battery, with a diameter of 21mm and a length (height) of 70mm, is generally called a lithium ion battery.
2. Different specifications and capacities: The capacity of 18650 lithium-ion is between 1200 mAh and 3600 mAh, but the most mature technology is generally between 2000 mAh and 3200 mAh. The capacity of the 21,700 lithium-ion batteries ranges from 3,000 mah to 5,000 mah.
3. Different application fields: 18650 lithium ion battery is suitable for rechargeable battery lighting, processing and manufacturing equipment lithium batteries, rechargeable battery inflatable tools, electric vehicle charger batteriesEU, lithium electric batteries, 3C digital products, smart home, etc.
Charging and discharging principle of lithium battery
The working principle of lithium-ion battery refers to its charging and discharging principle. discharge. When the battery is charged, lithium ions are generated on the positive electrode of the battery and the generated lithium ions move to the negative electrode via the electrolyte. The carbon used as a negative electrode has a layered structure with numerous micropores. The lithium ions that reach the negative electrode are integrated into the micropores of the carbon layer. The more lithium ions, the higher the charging capacity.
Similarly, when the battery is discharged (that is, the process when we use the battery), the lithium ions embedded in the carbon layer of the negative electrode are released and return towards the electrodepositive. The more lithium ions that return to the positive electrode, the higher the discharge capacity. What we usually call battery capacity refers to the discharge capacity.
It is not difficult to see that during the charging and discharging process of lithium-ion batteries, lithium ions are in a state of movement from the positive electrode → the negative electrode → the positive electrode. If we compare the lithium-ion battery to a rocking chair, the two ends of the rocking chair are the poles of the battery, and the lithium ions are like excellent athletes, running back and forth at both ends of the rocking chair. So, experts have given the lithium-ion battery a nice name: rocking chair battery.