Are cylindrical lithium-ion batteries safe?
Compared to pouch and prismatic lithium-ion batteries, the 18650 cylindrical lithium-ion battery is the earliest commercially available, has the highest degree of automation in production, and is currently the lowest-cost type of power lithium battery. The characteristics of cylindrical lithium-ion batteries are as follows:
1. Good consistency among individual cells. The consistency of cylindrical lithium-ion batteries refers to the consistency of the initial performance indicators of the individual cells used in the assembly, including: capacitance, impedance, electrical characteristics of the electrodes, temperature characteristics, decay rate, etc.
2. The single cell has better mechanical properties. Compared with square and pouch cells, the closed cylinder can achieve the highest bending strength at approximately the same size.
3. The technology is mature and the production cost is low, but at the same time, the room for cost optimization has been almost exhausted.
4. Its low energy density makes it easy to control in the event of an accident, but this very fact is becoming a reason for its replacement.
Cylindrical and prismatic batteries are currently the two main directions in the industry. Cylindrical lithium-ion batteries have a separator separating the positive and negative electrodes, which are then wound together to form a core. Typically, positive and negative electrode tabs are welded onto the positive and negative electrode sheets and led out from both sides. These tabs are welded to the positive and negative electrode casings. Electrolyte is added inside the casing. Generally, due to limitations in core current density and heat dissipation, the capacity of cylindrical lithium-ion batteries cannot be made too large.
Cylindrical lithium-ion batteries have a simple structure, close positive and negative electrode interfaces, mature production lines, low cost, good heat dissipation in battery packs, and excellent safety performance. Their disadvantages are relatively high internal resistance and stringent requirements for battery pack assembly. Returning to the 18650 cylindrical lithium-ion battery, this older battery, often attacked by counterfeit power bank manufacturers, is still widely used in various electronic devices, typically power banks. In fact, in high-end applications such as professional imaging equipment and laptop batteries, the 18650 has always been a mainstay, and its large-scale application in Tesla electric vehicles has further enhanced the high safety image of this type of lithium-ion battery.
Advantages of cylindrical lithium-ion batteries:
First, it has high energy density and high average output voltage. Furthermore, it has low self-discharge. As everyone knows, good batteries are very durable because cylindrical lithium-ion batteries have no memory effect, making them extremely durable and long-lasting.
In addition, cylindrical batteries have many advantages, including superior cycle performance, rapid charging and discharging, high charging efficiency, and high output power. It's worth mentioning that cylindrical lithium-ion batteries do not contain toxic or harmful substances and are known as "green batteries," so they are safe to use.
Compared to pouch and prismatic lithium-ion batteries, the 18650 cylindrical lithium-ion battery is the earliest commercialized, most automated in production, and currently the lowest-cost type of power lithium battery. With Tesla's long-standing presence, it has essentially maintained a three-way market share with pouch and prismatic batteries.
Since Tesla announced that the Model 3 would use the 21700, the cylindrical battery family has gained a new star member. This article will explore some key technical aspects of cylindrical batteries. Unless otherwise specified, "cylindrical battery" in the following text refers specifically to the 18650.
