18650 lithium battery

The 18650 lithium battery cell is currently one of the most commonly used cells for mobile power supplies and notebook batteries. The common form is a cylindrical cell with a diameter of 18mm and a length of 65mm. The most common lithium battery on the market is Cylindrical (cylindrical) packaging, which is the most widely used in the field of notebooks and strong light flashlights. The advantage of such packaging is that the specifications are unified, which is convenient for automation and large-scale production; in addition, there is Prismatic (square ) Soft package packaging is common in mobile phones and tablet computers. The most direct benefit of this type of package is its lightness and thinness, which makes it easy to control the thickness of the product.

   Many netizens talked about 18650 batteries, worried that they contained "liquid lithium ion", and talked about 18650 discoloration and panic explosion. To this end, some netizens disassembled an 18650 battery cell in their hands to find out what happened inside.

Violent dismantling of 18650 batteries, in-depth understanding of internal material structure

   First of all, when removing the battery cell, remember to discharge the light. Here, the 18650 battery cell is discharged until it fails and there is no voltage.

Violent dismantling of 18650 batteries, in-depth understanding of internal material structure

   Then, use needle-nose pliers to violently tear open the battery cap from the position of the battery cell, separate the positive and negative steel shells, exposing the safety valve and the rolled positive and negative materials.

Violent dismantling of 18650 batteries, in-depth understanding of internal material structure

  The safety valve is the standard configuration of every 18650 lithium battery cell, and it is also the most important explosion-proof barrier. The working principle of the safety valve: When the internal temperature of the battery is abnormal and the air pressure rises to 1.0-1.2Mpa, the safety valve opens to remove the internal gas to avoid explosion caused by excessive pressure. And Prismatic square soft-packed batteries, when the internal air pressure rises, the most common "pregnancy" bulge phenomenon.

Violent dismantling of 18650 batteries, in-depth understanding of internal material structure

   Popular science here is the positive electrode inside the cell. Now the common 2000-3000mAh capacity batteries such as Samsung, Panasonic, Sanyo, LG, etc., the internal cathode material has been fully upgraded from the first generation LiCoO2 lithium cobalt oxide to a ternary material, the chemical name is LiNi-Co-MnO2 nickel Cobalt manganese. The direct benefits: longer service life, safer and better performance. Speaking of this, Prismatic square soft package packaged mobile phone tablet batteries are also made of LiNi-Co-MnO2 nickel cobalt manganese material, but it is different from the 18650 Cylindrical package.

Violent dismantling of 18650 batteries, in-depth understanding of internal material structure

   Finally, take a close-up of the material inside the cell. The copper foil in the picture is used to coat LiNi-Co-MnO2 nickel-cobalt-manganese cathode material, on the contrary, aluminum foil is used to coat graphene. The capacity of the battery cell is based on the blending ratio of these formulas. Imitation is risky, and disassembly needs to be cautious.

   Conclusion: Through violent dismantling of the 18650 lithium battery cell, it was found that no liquid was flowing out of the battery, so there is no saying that "liquid lithium ion" is easy to explode. In fact, under normal circumstances, as long as it is used correctly, without charging or encountering extreme environments, 18650 batteries will not cause safety hazards.