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Comparison of technical characteristics of lithium batteries with different packages

2018-08-30(1714) Hits

  At present, there are three main types of packaging for lithium batteries. Square, cylindrical and soft packages, cylindrical and square batteries are mostly packed with steel or aluminum shells. Soft package is packed as aluminum plastic film, in fact, soft package is a square, the market is accustomed to aluminum plastic film packaging is called soft package, some people will be called flexible package battery polymer battery. Different packaging structures mean different characteristics, each of which has its own advantages and disadvantages.

  First、Square lithium battery
  Square lithium batteries usually refer to aluminum or steel shell square batteries, the popularity of square batteries in China is very high, with the rise of automotive power batteries in recent years, the contradiction between the vehicle mileage and battery capacity is becoming increasingly prominent, domestic power battery manufacturers mostly use high energy density aluminum shell square batteries, because Square battery structure is relatively simple, unlike cylindrical batteries using high strength stainless steel as the shell and with explosion-proof safety valve and other accessories, so the overall weight of accessories to light, relatively high energy density. The square battery has two different processes: winding and lamination.
  But because square lithium batteries can be customized according to the size of the product, there are thousands of models on the market, and because of too many models, the process is difficult to unify. Square batteries are not a problem in ordinary electronic products, but for industrial equipment products requiring more than one series, parallel connection, it is better to use standardized cylindrical lithium batteries, so that the production process is guaranteed, and it will be easier to find replaceable batteries in the future.

  Second、Round lithium battery
  Cylindrical lithium batteries refer to cylindrical lithium batteries. Cylindrical lithium batteries adopt quite mature winding process, with high degree of automation, stable product quality and relatively low cost. There are many types of cylindrical lithium batteries, such as 14650, 17490, 18650, 21700, 26650 and so on. Cylindrical lithium batteries are popular in Japanese and Korean lithium batteries enterprises. There are also large-scale enterprises producing cylindrical lithium batteries in China.
  With the further expansion of the electric vehicle market and the continuous improvement of the endurance mileage requirements, vehicle enterprises have put forward higher requirements for power batteries in energy density, manufacturing costs, cycle life and product attributes. In the field of raw materials has not yet made a huge breakthrough in the premise, the appropriate increase in the volume of cylindrical batteries to obtain more battery capacity has become an exploratory direction.

  Third、Soft lithium battery
  The key materials used in soft-packed lithium batteries - cathode materials, anode materials and diaphragms - are not much different from traditional steel and aluminum-coated lithium batteries. The difference lies in soft-packed materials (aluminum-plastic composite film), which are the key and most difficult materials in soft-packed lithium batteries. Flexible packaging materials are usually divided into three layers, namely, the outer barrier layer (usually made of nylon BOPA or PET), the barrier layer (intermediate aluminum foil) and the inner layer (multi-functional high barrier layer).
  Soft-packed batteries have a series of advantages due to their packaging materials and structures, such as good safety performance. Soft-packed batteries are structurally packed with aluminum-plastic film. When safety problems occur, the soft-packed batteries usually burst with air instead of exploding like steel or aluminum-coated batteries; light weight, soft-packed batteries weigh more than the same capacity. The steel-shell lithium battery is 40% lighter than the aluminum-shell lithium battery, 20% lighter than the aluminum-shell lithium battery; the internal resistance is small, the internal resistance of the soft-package battery is smaller than the lithium battery, which can greatly reduce the battery self-consumption; the cycle performance is good, the soft-package battery cycle life is longer, 100 cycle attenuation is less than the aluminum shell 4% - 7%; the design is flexible, the shape can be changed arbitrarily, can be thinner, can be. Customized according to customer needs, develop new electric core models. The disadvantages of soft battery are poor consistency, high cost and easy leakage. The high cost can be solved by large-scale production, and the leakage can be solved by improving the quality of aluminum plastic film.

  Fourth、Comparative analysis of technical characteristics
  1.Battery shape: square lithium battery can be of any size, so it can not be compared to a cylindrical battery.
  2.Multiplier characteristics: Cylindrical lithium battery welding multipole ear process constraints, so the multiplier characteristics slightly worse than the square multipole ear scheme.
  3.Discharge platform: The same cathode material, anode material, electrolyte, so the discharge platform is the same in theory, but the square cell resistance is slightly dominant, so the discharge platform is slightly higher.
  4.Product quality: Cylindrical lithium battery technology is very mature, the probability of public secondary cutting defects is low, and winding process is more mature and automated than lamination process, lamination process is still semi-manual, so it has a negative impact on the quality of the battery.
  5.Ear welding: cylindrical lithium battery ear is easier to weld than square lithium battery, square battery easy to produce virtual welding affect battery quality.
  6.PACK Group: Circular batteries are relatively easy to use, so the PACK scheme is simple, good heat dissipation effect, square battery PACK to solve the problem of heat dissipation.
  7.Structural characteristics: The chemical activity of the square cell corner is poor, and the performance of the long-term use of the battery declines significantly.
  In short, whether cylindrical, square or flexible packaged batteries, the reason for the rapid development of the current, because they are good at their respective areas of application, have been very good application.