Types of lithium-ion battery pack cells
There are three main types of battery cells widely used in the market: 18650 cells, polymer cells, and lithium iron phosphate cells.
I. 18650 battery cells
18650 lithium-ion batteries refer to batteries with a diameter of 18mm and a length of 65mm; the "0" indicates a cylindrical shape. 18650 cell technology is relatively mature, with a stable battery structure, high specific capacity, and outstanding overall performance. Furthermore, its small size allows for its use in a wide range of applications.
II. Polymer Battery Cells
The difference between polymer batteries and traditional lithium-ion batteries lies in their manufacturing process. Lithium-ion batteries are wound together, resulting in a softer form factor. Polymer batteries are stacked together, resulting in a rigider form factor. For the same volume, polymer batteries have a larger capacity, approximately 30% higher. They are also safer, with a lower risk of explosion, and have a longer lifespan.
III. Lithium iron phosphate cells
Lithium iron phosphate (LFP) battery cells are made from resources that are more abundant on Earth. The PO bonds in the lithium iron phosphate crystals within the cells are stable and difficult to decompose. Unlike lithium cobalt oxide, they do not experience structural collapse and heat generation or form strong oxidizing substances even at high temperatures or during overcharging, thus offering excellent safety.
What is the technological level of lithium-ion battery pack cells?
In terms of lithium-ion battery cell technology, there is still a significant gap between domestic and international standards. This article will analyze the technological level of domestic lithium-ion battery cells by examining the three packaging systems used in lithium-ion battery packs: prismatic, cylindrical, and pouch. These three packaging systems are the most widely used worldwide.
Square shell
Regarding prismatic lithium-ion battery cells, some domestic companies have already achieved an energy density of 240Wh/kg and plan to increase it to 300Wh/kg by 2020. Internationally, some foreign companies produce lithium-ion cells with an energy density 10Wh/kg higher than their domestic counterparts, reaching 250Wh/kg. However, industry insiders speculate that the cathode materials used in these higher energy density cells may differ from those used domestically. While domestic companies still lag behind foreign companies in energy density, the gap is not significant, and the choice of cell materials may differ. If a comparison of technological levels is desired, the energy density of prismatic cells of the same specifications is more comparable. Therefore, from a purely technological perspective, the difference between domestic and foreign technologies may not be substantial.
cylinder
Regarding cylindrical cells, domestic manufacturers have achieved an energy density of 240Wh/kg, while foreign technology has reached 250Wh/kg. Both cylindrical and prismatic cells lag behind foreign counterparts by 10Wh/kg in energy density. However, domestic companies are working diligently to catch up, and it's believed that reaching the technological level of foreign lithium-ion cells is not far off.
Soft pack
If pouch cells are to be compared with cells using other packaging methods in terms of energy density, then pouch cells will definitely be able to reach a high density level of 200Wh/kg more quickly in terms of technology.
