Structure of cylindrical lithium batteries
Cylindrical lithium batteries refer to round lithium batteries. The earliest cylindrical lithium battery was the 18650 lithium battery invented by Sony Corporation of Japan in 1992. Because of its long history, the 18650 cylindrical lithium battery has a very high market penetration rate. Cylindrical lithium batteries utilize a mature winding process, have a high degree of automation, stable product quality, and relatively low cost. There are many models of cylindrical lithium batteries, such as the common 14650, 17490, 18650, 21700, and 26650. Cylindrical lithium batteries are more popular among lithium battery companies in Japan and South Korea, and there are also a considerable number of companies producing cylindrical lithium batteries in China.
As the electric vehicle market expands and demands for longer driving ranges increase, automakers are placing higher demands on power batteries in terms of energy density, manufacturing costs, cycle life, and added product attributes. Without significant breakthroughs in raw materials, increasing the volume of cylindrical batteries to achieve greater capacity has become a viable option. Tesla has already begun mass production of its 21700 batteries, planning to use them in its Model 3. If successful in testing on other Tesla models, they will replace the previously used 18650 batteries. Tesla's approach may lead to a global "21700 trend."
Cylindrical lithium battery classification by model
I. Cylindrical primary batteries, mainly AA and AAA batteries; other models are not listed here, please consult the manufacturer for details.
A standard AA battery typically measures 14mm in diameter and 49mm in height.
A standard size 7 battery typically measures 11mm in diameter and 44mm in height.
II. Cylindrical lithium batteries, mainly models such as 18650, 16650, 14500, etc.
18650 means 18 mm in diameter and 65 mm in length. A size 5 battery, on the other hand, is 14500, with a diameter of 14 mm and a length of 50 mm. 18650 batteries are generally more commonly used in industrial applications and less so in consumer use; they are most commonly found in laptop batteries and high-end flashlights.
18650 is just a battery size model. Depending on the type of battery, it can be divided into lithium-ion 18650, lithium iron phosphate 18650, and nickel-metal hydride 18650 (rare). The most common 18650 is lithium-ion.
1. Large capacity: The capacity of 18650 lithium batteries is generally between 1200mAh and 3400mAh.
2. Long lifespan: 18650 lithium batteries have a very long lifespan, with a cycle life of more than 500 cycles under normal use, which is more than twice that of ordinary batteries.
3. High Safety Performance: 18650 lithium batteries boast high safety performance. Introduced in 1996, the 18650 lithium battery has undergone decades of development and now achieves fully automated production. Its voltage, internal resistance, capacity, and self-discharge consistency are excellent, making it a preferred choice across various industries. It also exhibits good high-temperature resistance, achieving 100% discharge efficiency at 65 degrees Celsius. To prevent short circuits, the positive and negative terminals of the 18650 lithium battery are separate, minimizing the possibility of a short circuit. A protection board can be added to prevent overcharging and over-discharging, further extending the battery's lifespan.
4. High voltage: The voltage of 18650 lithium batteries is generally 3.6V, 3.8V and 4.2V, which is much higher than the 1.2V voltage of nickel-cadmium and nickel-metal hydride batteries.
5. No memory effect: There is no need to completely discharge the remaining power before charging, making it convenient to use.
6. Can be connected in series or parallel to form an 18650 lithium battery pack.
7. Wide range of applications: laptops, walkie-talkies, portable DVDs, instruments, audio equipment, model airplanes, toys, cameras, digital cameras, new energy vehicles, medical devices and other electronic equipment.
8. When compared to other brands, the battery is more competitively priced. The various components of the battery are already mass-produced and mature, which greatly reduces production costs. Therefore, it is the best choice in terms of cost performance.
