Mainstream lithium battery packaging forms: round, square and soft pack.
Cylindrical lithium batteries are divided into: lithium iron phosphate, lithium cobalt oxide, lithium manganate, cobalt, manganese mixed ternary materials of different systems, the shell is divided into two kinds of steel shell and polymer, batteries of different material systems have different advantages.
The market penetration rate is very high. The cylindrical lithium battery adopts a fairly mature winding process, with a high degree of automation, stable product quality and relatively low cost.
Cylindrical lithium batteries are more popular among Japanese and Korean lithium battery companies, and there are also large-scale enterprises in China that produce cylindrical lithium batteries.
The structure of a typical cylindrical lithium battery includes: positive cover, safety valve, PTC element, current cut-off mechanism, gasket, positive electrode, negative electrode, separator, and casing.
Square lithium-ion batteries, commonly referred to as aluminum or steel square battery cases, find that the popularity of batteries is very high in China. With the rise of automotive power lithium batteries in recent years, the battery capacity has become increasingly prominent, and Chinese power lithium battery manufacturers are mostly used. The aluminum shell square battery with high battery energy density is mainly used. The square battery is not like the cylindrical battery. The high strength stainless steel is used as the shell and the accessories such as explosion-proof safety valve are used. The overall accessories are light in weight and high in density. Square cells are wound and laminated in two different processes.
However, since the square lithium battery can be customized according to the size of the product, there are thousands of types in the market, and the process is difficult to unify. There is no problem with the use of square batteries in general electronic products, but for multiple series and parallel industrial equipment products, it is best to use standardized cylindrical lithium-ion batteries, which is guaranteed and easier to find replaceable batteries.
The key materials used in soft-pack lithium-ion batteries are the positive electrode materials, negative electrode materials and separators, which are not much different from traditional aluminum-shell lithium-ion batteries. The biggest difference is the flexible packaging material (aluminum-plastic composite film). The most critical and technically difficult material in batteries. Flexible packaging is usually divided into three layers, namely the outer resistance layer (usually an outer protective layer composed of nylon BOPA or PET), a permeation resistance layer (aluminum foil middle layer) and an inner layer (multifunctional high barrier layer).
Pouch battery packaging materials and structures have a series of advantages, such as: good safety features, selection of pouch battery structure, aluminum plastic film packaging, security attack, pouch battery weight is 40% lighter than steel-ion battery of the same capacity, It is 20% lighter than aluminum-lithium-ion batteries and has low internal resistance. The internal resistance of the battery is smaller than that of the lithium battery.
It has a good cycle function, which makes the cycle life of the soft pack battery longer. The attenuation of 100 cycles is 4%-7% smaller than that of the aluminum shell. The design is flexible, the shape can be changed, and it can be thinner. It can be customized to develop new models. Battery. The disadvantages of soft pack batteries are poor consistency, high cost, and short-term attack leakage. High cost can be dealt with by mass production, and leakage can be dealt with by improving the quality of aluminum plastic film.
The above three structural characteristics: the chemical activity at the corners of the square battery is poor, and the long-term use of the battery performance is more obvious.