What is the difference between 18650 lithium battery and polymer lithium battery
Issuing time:2020-07-20 08:46
1. The 18650 battery is cylindrical and has liquid inside. Because of the battery design and material, the 18650 is suitable for large currents. Therefore, almost all notebooks and electric vehicles are designed with 18650 batteries; only super notebooks are not used because of energy saving. Instead of using 18650 batteries, polymer lithium batteries, especially tablet computers, etc.; for digital cameras, because flash charging and discharging require high voltage and instantaneous high current, they can only use 18650 similar batteries, but they are slightly smaller;
2. The advantages of polymer lithium battery are small size and large capacity. The disadvantage is that the service life is shorter than 18650. Because of the use of different designs and materials, some have liquid inside, some are dry or colloidal, and have high current discharge performance. Not as good as the 18650 cylindrical battery, so it needs large-capacity and small-volume electrical equipment, usually using polymer lithium batteries, the most typical performance is mobile phones, tablet computers and other equipment.
First of all, the 18650 battery has a cylindrical shape with liquid inside. Because of the characteristics of the battery design and raw materials, the dynamic 18650 battery is suitable for high-current discharge. Therefore, almost many high-power products on the market use 18650 lithium batteries, but ultra-thin notebooks, especially It is a tablet computer, etc., because the appearance is required to be thin, so instead of using 18650 batteries, polymer lithium batteries are used. However, high-power digital cameras are different, because the charging and discharging of the flash requires high voltage and instantaneous high current, so it can only Use 18650 power lithium batteries or other types of power batteries, but they are only slightly smaller. For example, 18500 power lithium batteries are commonly used in digital camera products; and with the advantages of high energy density and high current discharge of 18650 power lithium batteries, The so-called polymer lithium battery now refers to a lithium ion battery that uses a polymer as an electrolyte, and is divided into two types: "semi-polymer" and "all-polymer". "Semi-polymer" refers to coating a layer of polymer (usually PVDF) on the isolation membrane to make the cell's adhesion stronger, the battery can be made harder, and the electrolyte is still a liquid electrolyte. "All polymer" refers to the use of polymer to form a gel network inside the cell, and then inject electrolyte to form an electrolyte. Although "all polymer" batteries still use liquid electrolyte, the amount is much smaller, which greatly improves the safety performance of lithium-ion batteries. As far as I know, only SONY is currently mass producing "all-polymer" lithium-ion batteries.
From another aspect, polymer batteries refer to lithium-ion batteries that use aluminum-plastic packaging film as the outer packaging, which is commonly known as soft pack batteries. This kind of packaging film is composed of three layers, namely PP layer, Al layer and nylon layer. Because PP and nylon are polymers, this kind of battery is called polymer battery.
1, the price is lower
The international price of 18650 is about 1USD/pcs, which is about 3RMB/Ah if calculated according to 2Ah. The price of polymer lithium batteries is 4RMB/Ah for low-end cottage factories, 5~7RMB/Ah for mid-end, and 7RMB/Ah for mid-to-high end. Products like ATL and Lishen can generally sell for around 10RMB/Ah, and you are still unwilling to pick them up when your order is small.
2, can not be customized
SONY has always wanted to make lithium-ion batteries like alkaline batteries. There are certain industry standards, just like AA batteries and AA batteries, which are basically the same all over the world. However, because a major advantage of lithium-ion batteries is that they can be designed according to customer needs, there is no uniform standard. So far, the lithium-ion battery industry basically only has a standard model of 18650, and the others are based on customers. Need to be designed.
3, poor safety
We know that under extreme conditions (such as overcharge, high temperature, etc.), lithium-ion batteries will have violent chemical reactions inside and produce a lot of gas. The 18650 battery uses a metal shell with a certain strength. When the internal pressure reaches a certain level, the steel shell will burst and explode, causing a terrible safety accident.
This is why the room where the 18650 battery is tested generally must be protected by layers, and no one can enter during the test. Polymer batteries do not have this problem, even in extreme cases, due to the low strength of the packaging film, as long as the air pressure is slightly higher, it will rupture and will not explode. The worst case is combustion. So in terms of safety, polymer batteries are better than 18650 batteries.
4, low energy density
The capacity of a general 18650 battery can reach about 2200mAh, so the energy density is about 500Wh/L, while the energy density of polymer batteries can be close to 600Wh/L at this stage.
But polymer batteries also have their own shortcomings. The main reason is that the cost is relatively high. Since it can be designed according to customer needs, the R&D cost must be included. In addition, the variety of shapes and types have resulted in non-standard parts of various tooling and fixtures during the manufacturing process, which also increased costs accordingly. The polymer battery itself has poor versatility, which is also brought about by flexible design. It is often necessary to redesign one for customers for the difference of 1mm.
Three, the application of 18650 lithium battery
The application of lithium secondary batteries in the energy battery industry benefits from its superior performance. With the continuous development of lithium secondary battery technology, it has been widely used in our daily lives; rechargeable batteries that are used repeatedly are more and more favored by consumers. Pay attention to the energy battery industry and fully understand the battery so that we can achieve "for my use". At present, 18650 lithium batteries have certain applications in the following fields.
1. Energy storage
is mainly used in base station power supply, clean energy storage, grid power storage, home optical storage system, etc.
mainly refers to electric vehicles, electric bicycles, new energy vehicles, etc.
Mobile phones, tablets, laptops, electric toys, MP3/MP4, earphones, power banks, model airplanes, mobile power supplies, etc.