The most obvious difference between 18650 lithium batteries and soft pack lithium batteries in terms of appearance is that 18650 lithium batteries are cylindrical steel shell batteries with basically the same size, while soft pack lithium batteries can have any shape and size, and the outer shell is a battery packaged with aluminum-plastic film. The difference between 18650 lithium batteries and soft pack lithium batteries lies in the use of different materials such as electrolytes, conductive agents, electrode formulation ratios, and production processes.
1. Differences in electrolytes between 18650 lithium batteries and soft pack lithium batteries
Although the appearance and internal structure of 18650 lithium batteries and soft pack lithium batteries are different, the principles of these two types of batteries are basically the same. Both types of batteries have a positive electrode, negative electrode, and electrolyte. The positive electrode material is generally lithium cobalt oxide, nickel cobalt manganese oxide (ternary material), lithium iron phosphate or lithium manganese oxide, etc. The negative electrode material is generally graphite, and the electrolyte is a lithium hexafluorophosphate solution.
As the two mainstream lithium batteries in the current market, 18650 lithium batteries and lithium polymer soft pack batteries are distinguished according to the packaging material of the shell. 18650 lithium batteries are generally packaged in a steel shell (18 represents a diameter of 18mm, 65 represents a length of 65mm, and 0 represents a cylindrical battery), and the internal electrode plate and diaphragm structure is wound. The outer packaging of lithium polymer soft pack batteries uses aluminum-plastic film, and the internal electrode plates and separators are stacked layer by layer.
The main difference between the 18650 lithium battery and the soft packed lithium battery lies in the shape of the electrolyte inside the battery: the electrolyte inside the lithium polymer soft packed battery is polymer, generally gel or solid, while the electrolyte inside the 18650 lithium battery is generally liquid.
2. The advantages, disadvantages, and application fields of 18650 lithium batteries and soft pack lithium batteries are different
18650 lithium batteries and lithium polymer soft pack batteries each have their own advantages and disadvantages. At present, the production automation of 18650 lithium batteries is high, and the consistency and safety of the batteries have reached a high level. In addition, the small size and light weight of the batteries themselves give them unique advantages in terms of system development modularity and standardization. Many people believe that using 18650 lithium batteries as the power source for new energy electric vehicles is a better choice at this stage.
Compared with 18650 lithium batteries, lithium polymer soft pack batteries have higher monomer capacity and advantages such as thinness, arbitrary area and shape (ultra-thin batteries with models such as 0.33mm and 0.50mm can be produced). However, their main disadvantages are poor consistency and mechanical strength. Based on the characteristics of lithium polymer pouch batteries, they are increasingly being used in fields such as mobile phones, laptops, and mobile power supplies. However, due to the poor conductivity and high internal resistance of colloidal (or solid) electrolytes, lithium polymer soft pack batteries are now rarely used in electric vehicles.
However, the 18650 lithium battery also has an unavoidable drawback, which is its low individual capacity (generally around 2-4Ah). This makes the 18650 lithium battery require a large number of batteries for application, and the battery management system for maintaining cell consistency and battery heat dissipation more complex.
3. The difference in high current discharge performance between 18650 lithium batteries and soft pack lithium batteries
In terms of high current discharge performance of lithium batteries, soft pack lithium batteries can achieve higher rates than 18650 lithium batteries. At the same time, in terms of high current discharge stability performance, soft pack lithium batteries have better performance. In terms of equivalent discharge requirements and capacity, soft pack lithium batteries can be customized according to the shape of the product battery compartment space, achieving a more lightweight form.