Cylindrical Batteries And Soft Packs Who Are More Suitable For Electric Cars?

- Feb 16, 2017-

In January 2017, the world's leading electric car brand Tesla announced that the company's Nevada-based super factory (Gigafactory) has begun mass production of lithium-ion battery. This cylindrical "2170 lithium battery" is Tesla and Panasonic co-designed, will be used for Tesla energy storage products and the new Model 3 sedan.

From 18650 to 2170, the limestone of the cylindrical lithium-ion battery seems to be getting more and more Sheng. However, although Tesla is attached to the 18650 as the representative of the cylindrical battery, the other two world electric car brands, Nissan hear the wind and Chevrolet Vaughan's choice is different. Data show that Nissan hear the wind, Chevrolet Wo Lan Da in the choice of power battery is a stack of flexible battery pack.

With the world famous electric car brand, what reason they make the choice of power battery is very different? In the field of automotive power battery applications, 18650 lithium battery and soft battery the advantages and disadvantages of their own where?

Round batteries and soft batteries who are more suitable for electric cars?

The shape of the electrolyte is different

As the current market, the two mainstream power battery, 18650 battery and lithium polymer soft package battery according to the shell packaging material and distinguish. 18650 battery is generally steel shell package (18 for 18 mm in diameter, 65 for 65 mm in length and 0 for cylindrical battery). The structure of the internal electrode and diaphragm is wound. Lithium polymer soft package battery packaging is the use of aluminum plastic film, the internal electrode pads and diaphragms are stacked (layer by layer stack).

Although the shape and internal structure is different, but the two batteries basically the same principle. The two batteries have positive, negative and electrolyte, the cathode material is generally lithium cobalt oxide, nickel cobalt manganese manganate (ternary material), lithium iron phosphate or lithium manganate, anode material is generally graphite, the electrolyte was Lithium hexafluorophosphate solution.

The main difference between the two is the battery internal material - the electrolyte of the different forms: lithium polymer soft battery internal electrolyte is used in the polymer, usually gel or solid, and 18650 battery internal electrolyte is generally liquid. 18650 lithium battery and lithium polymer flexible battery battery have their own advantages and disadvantages. At present, 18650 battery production of a high degree of automation, battery consistency, security have reached a high level, coupled with the battery itself is small, light weight, so that the system development in the modular and standardized degree has a unique advantage. Many people believe that the use of 18650 battery as a source of power for new energy vehicles, at this stage is the best choice.

However, the 18650 battery can not avoid the shortcomings, that is, monomer capacity is low (generally around 2 ~ 4Ah). This makes the 18650 battery in the application of the required number of batteries is very much to maintain the consistency of batteries, battery cooling battery management system is also more complex.

Compared with the 18650 battery, lithium polymer flexible battery single cell capacity is high, and has a thin, any area and any shape, etc. (can produce 0.33mm, 0.50mm and other models of ultra-thin battery) , The main drawback is poor consistency, poor mechanical strength. Based on the characteristics of lithium polymer flexible battery, lithium polymer flexible battery is increasingly being used in mobile phones, laptops, mobile power and other fields. However, because the colloid (or solid) electrolyte conductivity is not very good, large internal resistance, lithium polymer flexible battery is now rarely used in electric vehicles.

Soft battery is not all lithium polymer battery

Since lithium polymer soft battery is rarely used in electric vehicles, then, Nissan hear the wind of the stack of flexible battery pack is what type of battery?

In fact, although the lithium polymer package is generally referred to as flexible battery pack, but because the flexible battery can also use liquid electrolyte, so the soft battery is not all lithium polymer battery. Nissan hear the wind battery is the use of liquid electrolyte battery pack.

Whether the lithium polymer soft battery, or the internal material for the liquid electrolyte of the flexible battery, flexible battery is generally used in aluminum plastic film package. The aluminum film thickness is thin, the mechanical strength is poor, in the car collision and other extreme cases, aluminum plastic film is prone to damage caused by accidents, which is the use of soft batteries in the new energy vehicles on the main flaws.

It is reported that, in order to ensure safety, Nissan hear the wind in the four components of the battery module outside the addition of an aluminum case to policy. Even so, the battery leakage is still Nissan hear the fatal flaw of the battery, Nissan hear the wind battery in the riders in the "leakage of the king" of the title, often criticized.