18650 lithium battery and soft pack battery which is more suitable for electric cars?

18650 lithium battery and soft pack battery which is more suitable for electric cars?

Same as world-renowned electric car brands, what makes them different in choice of power battery? In field of automotive power battery applications, where are the advantages and disadvantages of the 18650-lithium battery and the soft battery?

The difference in electrolyte morphology is key

As two mainstream power batteries on the market, 18650 batteries and lithium polymer soft pack batteries are distinguished by the package material of the casing. The 18650 battery is generally a steel casing package (18 indicates a diameter of 18 mm, 65 indicates a length of 65 mm, and 0 indicates a cylindrical battery), and the structure of the inner electrode sheet and the diaphragm is a wound type. The lithium polymer soft pack battery is made of aluminum plastic film, and the inner electrode sheet and the diaphragm are stacked (stacked one by one).

Although the shape and internal structure are different, the principles of the two batteries are basically the same. Both batteries have a positive electrode, a negative electrode and an electrolyte. The positive electrode material is generally lithium cobaltate, lithium nickel cobalt manganese oxide (ternary material), lithium iron phosphate or lithium manganate, and the negative electrode material is generally graphite, and the electrolyte is Lithium hexafluorophosphate solution.

The main difference between the two is that the electrolyte is different in one of the internal materials of the battery: the electrolyte inside the lithium polymer soft pack battery is a polymer, generally gel or solid, and the electrolyte inside the 18650 battery is generally liquid.

Each has its own advantages and disadvantages, different application fields

18650 lithium battery and lithium polymer soft pack battery have their own advantages and disadvantages. At present, 18650 battery production has a high degree of automation, battery consistency and safety have reached a high level, coupled with the small size and light weight of the battery itself, it has unique advantages in the modularization and standardization of system development. Many people believe that the use of 18650 battery as the source of power for new energy electric vehicles is the best choice at this stage.

However, the 18650 battery also has the disadvantage of being unavoidable, that is, the monomer capacity is low (generally around 2~4Ah). This makes the 18650 battery require a lot of batteries for application, and the battery management system that maintains cell consistency and battery cooling is more complicated.

Compared with the 18650 battery, the lithium polymer soft pack battery has a high capacity, and has the advantages of being thinner, arbitrarily aread, and arbitrarily shaped (it is possible to produce ultra-thin batteries of 0.33 mm, 0.50 mm, etc.) The main disadvantages are poor consistency and poor mechanical strength. Based on the characteristics of lithium polymer soft pack batteries, lithium polymer soft pack batteries are increasingly being used in mobile phones, notebook computers, mobile power supplies and other fields. However, due to the poor conductivity of the colloidal (or solid) electrolyte and the large internal resistance, lithium polymer soft pack batteries are rarely used in electric vehicles.

Soft pack batteries are not all lithium polymer batteries

Since lithium polymer soft pack batteries are rarely used in electric vehicles, what type of batteries are Nissan Leaf's cascading soft pack batteries?

In fact, although lithium polymer soft pack batteries are generally referred to as soft pack batteries, soft pack batteries are not all lithium polymer batteries because they can also use liquid electrolyte. Nissan Leaf's battery is a soft pack battery with liquid electrolyte.

Whether it is a lithium polymer soft pack battery or a soft pack battery whose internal material are a liquid electrolyte is generally package in an aluminum plastic film. Aluminum plastic film is thin, and mechanical strength is poor. In the extreme case of collision of e automobile, aluminum plastic film is easily damage and causes an accident, which is a major defect of soft pack battery used in new energy vehicle.

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