In January 2017, Tesla, the world’s leading brand of electric vehicles, claimed that the company’s Gigafactory begins to produce lithium-ion batteries. It is a cylindrical “2170 lithium battery” developed by Tesla together with Panasonic that will be used for the new model 3 Series.
From 18650 to 2170, cylindrical lithium-ion batteries seem to be becoming more and more accepted by the market. However, while Tesla sticks to the 18650 cylindrical batteries, the other two of the world’s largest electric car brands, Nissan and Chevrolet Volt’s choice is different. According to the Reports, Nissan, Chevrolet Volt to choose a battery power laminated by a Soft Pack battery.
What are the reasons for the world-famous brand of electric cars that make them different from the choice of power source? What are the Pros and Cons of the 18650 lithium-ion batteries and soft-pack batteries in the automotive battery industry?
Nissan Leaf Battery（soft pack）
Will the soft pack batteries that are more suitable for electric vehicles?
Different forms of electrolyte
As the current market for the two main battery power, 18650 battery, and lithium polymer battery is soft over the shell packaging material. The 18650 battery is usually a steel shell package (18 means 18mm diameter, 65 indicates length-65mm, 0 is a cylindrical battery), parts of the inner electrode and diaphragm are the Type of winding. The outer package of lithium-polymer soft-packaged battery uses aluminum polyethylene film, a piece, an inner electrode and a double-layer diaphragm (one layer on the stack level).
Although the shape and internal structure are different, the principles of the two batteries are basically the same. Both batteries have positive, negative and electrolyte, cathode materials, usually lithium-cobalt, nickel cobalt lithium manganese acid (ternary materials), lithium-iron-phosphate or lithium manganese oxide, cathode materials, usually graphite, electrolyte six Of lithium fluoride with a solution of phosphate.
The main difference between them is that one of the internal materials of the battery-electrolyte is different: the lithium polymer battery is a soft package inside the electrolyte used by the polymer, usually a gel or solid, and 18650 cells of the internal electrolyte are usually liquid.
Both of them has Advantages and Disadvantages
18650 lithium-ion batteries and lithium-polymer batteries in soft packaging have their advantages and disadvantages. At present, 18650 battery has reached a higher level of production automation, battery compliance, security, and lightweight, all of these advantages make more suitable for mass production. Many people believe that at this stage using the 18650 battery as a power source is the best choice for electric vehicles.
Tesla 18650 Battery
However, the 18650 battery also has unavoidable drawbacks, that is, the energy density capacity is relatively low (typically about 2-4acs). This requires a large number of batteries to maintain a long distance drive, but to maintain the consistency of so huge number of battery cells will need complex battery management systems, and till now only Tesla has the technology.
This is quite different from lithium polymer battery, which has the advantages of a thin shape, arbitrary area and arbitrary shape (0.33mm, 0.50mm, and other ultra-thin battery models). the lipo battery main drawback is a poor consistency, Weak mechanical strength.
Based on the features of lithium-polymer soft-pack batteries, lithium-polymer flexible batteries are increasingly being used in mobile phones, laptops, mobile devices and other areas. However, since the conductivity of the colloid (or solid) electrolyte is not very good, the internal resistance is greater, the lithium-polymer soft battery bag is rarely used in electric vehicles.
But Soft-pack batteries are not lithium-polymer batteries.
Since lithium-polymer soft-packaged batteries are rarely used on electric vehicles, which batteries are cascaded soft-pack batteries that Nissan hears?
In fact, although a lithium-polymer battery is soft, it is usually called a soft battery, but since a soft battery can be used with a liquid electrolyte, so a soft battery is not a lithium polymer battery. Nissan battery is a soft battery that uses liquid electrolytes.
Whether it is a lithium polymer soft pack battery or the internal material for the liquid electrolyte of the soft pack battery, soft package batteries are generally used aluminum plastic film packaging. and the thickness of the aluminum plastic film thin, the mechanical strength is poor, in the case of car collisions and other extreme circumstances, the aluminum plastic film is prone to damage caused by accidents, this is the application of soft package batteries in the new energy vehicles major defects.
It is reported that, in order to ensure safety, Nissan’s EV Car battery module was added to an aluminum shell. Even so, the battery leakage is still a fatal flaw in the Nissan Battery, the Nissan, however, are often criticized as “leakage King” for car insiders.