18650 lithium battery vs polymer battery
Lithium polymer batteries refer to lithium ion batteries that use polymers as electrolytes, and are divided into two types: "semi-polymer" and "full-polymer". "Semi-polymer" means that a layer of polymer (usually PVDF) is coated on the separator to make the adhesion of the cell stronger, the battery can be made harder, and its electrolyte is still a liquid electrolyte.
The "all-polymer" refers to the use of polymers to form a gel network inside the cell, and then inject the electrolyte to form the electrolyte. Although "all-polymer" batteries still use liquid electrolyte, the amount is much smaller, which greatly improves the safety performance of lithium-ion batteries. According to the Keheng New Energy team, only SONY is mass-producing "all-polymer" lithium-ion batteries.
On the other hand, polymer batteries refer to lithium-ion batteries that use aluminum-plastic packaging films as outer packaging, which are commonly known as soft-pack batteries. This packaging film is composed of three layers, namely PP layer, Al layer and nylon layer. Since PP and nylon are polymers, this kind of battery is called a polymer battery.
The difference between 18650 lithium battery and polymer battery is as follows
1. Lower price
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 ones, and more than 7RMB/Ah for mid-to-high-end ones. Like ATL and Lishen, they can generally sell for about 10RMB/Ah. The MOQ requirements for orders from 18650 lithium battery manufacturers are very high.
2. Can not be customized
SONY has always wanted to make lithium-ion batteries like alkaline batteries, with certain industrial standards, just like AA batteries and AA batteries, which are basically the same all over the world. However, because one of the advantages of lithium-ion batteries is that the shape can be designed according to the needs of customers, it is impossible to have a unified standard, so now the lithium-ion battery industry basically only has a standard model of 18650, and the others are based on customers. needs to be designed.
3. Poor security
We know that under extreme conditions (such as overcharge, high temperature, etc.), a lithium-ion battery will undergo a violent chemical reaction inside, producing a large amount of gas. The 18650 battery uses a metal shell, which has a certain strength. When the internal air pressure reaches a certain level, the steel shell will rupture and explode, resulting in a terrifying safety accident.
This is why the room where the 18650 battery is tested must generally be protected with 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, and the worst case is burning.
So in terms of safety, polymer batteries are better than 18650 batteries.