Types of Cylindrical Lithium-ion Cell

Ⅰ. Introduction to Cylindrical Lithium-Ion Cells  

Cylindrical lithium-ion batteries are classified into lithium cobalt oxide, lithium manganese oxide, and ternary material types, each with distinct advantages. These batteries are widely used in applications such as laptops, digital cameras, lighting fixtures, toys, power tools, and portable mobility devices.

Ⅱ. Structure of Cylindrical Lithium-Ion Cells  

Cylindrical lithium-ion cells refer to round lithium batteries, with the earliest model being the 18650 battery, invented by Sony in 1992. Due to its long history, the 18650 battery remains highly popular in the market.  

These batteries use a mature and efficient winding process, ensuring high automation, stable quality, and relatively low production costs.  

There are various cylindrical cell types, including 14650, 17490, 18650, 21700, and 26650. Cylindrical lithium batteries are widely produced by Japanese and Korean manufacturers, with several large-scale manufacturers also operating in China.

Ⅲ. Classification of Cylindrical Lithium-Ion Cells  

1. Cylindrical Primary Batteries  

- Common types include No. 5 (AA) and No. 7 (AAA) batteries.  

- No. 5 (AA) batteries typically measure 14mm in diameter and 49mm in height.  

- No. 7 (AAA) batteries generally measure 11mm in diameter and 44mm in height.  

2. Cylindrical Lithium-Ion Batteries  

- Common types include 18650, 16650, and 14500.  

- 18650 batteries measure 18mm in diameter and 65mm in length.  

- 14500 (AA lithium battery) measures 14mm in diameter and 50mm in length.  

Usage and Variants  

- The 18650 battery is widely used in industrial applications, laptop batteries, and high-performance flashlights but is less common for civilian use.  

- 18650 batteries come in different chemistries, including lithium-ion, lithium iron phosphate (LiFePO4), and nickel-metal hydride (rarely used). The most common type is lithium-ion.

2. Large Capacity  

- The capacity of 18650 lithium cylindrical cells typically ranges from 1200mAh to 3400mAh.  

3. Long Service Life  

- The 18650 lithium battery has a long lifespan, with a cycle life exceeding 500 charge-discharge cycles under normal use—more than twice that of standard batteries.  

4. High Safety Features  

- First introduced in 1996, the 18650 lithium battery has undergone decades of development and now benefits from fully automated production.  

- It offers excellent consistency in voltage, internal resistance, capacity, and self-discharge.  

- It is widely used across industries due to its high-temperature resistance, maintaining 100% discharge power at 65°C.  

- To prevent short circuits, the positive and negative electrodes are separated, minimizing risks.  

- A protection board can be added to prevent overcharging and over-discharging, further extending the battery’s lifespan.

5. High Voltage  

- The 18650 lithium battery typically operates at 3.6V, 3.8V, or 4.2V, significantly higher than the 1.2V of nickel-cadmium and nickel-metal hydride batteries.  

6. No Memory Effect  

- Unlike some other rechargeable batteries, 18650 lithium batteries do not require full discharge before recharging, making them more convenient to use.  

7. Scalability  

- These batteries can be connected in series or parallel to form a 18650 lithium battery pack, providing flexible energy solutions.  

8. Wide Applications  

- Used in laptops, walkie-talkies, portable DVDs, instrumentation, audio equipment, drones, toys, camcorders, digital cameras, electric vehicles, and medical devices.  

9. Cost-Effective  

- Among batteries of the same brand, 18650 lithium batteries offer competitive pricing due to mature technology, mass production, and reduced manufacturing costs, making them a high-value choice.