According to the shape of the picture, lithium-ion batteries are divided into square lithium batteries (such as commonly used mobile phone battery cells), cylindrical lithium batteries (such as 18650, 18500, etc.) and button lithium batteries; lithium batteries are divided into aluminum shell lithium batteries, Steel shell lithium battery, soft pack battery; according to the positive electrode material, it can be divided into lithium cobalt oxide, lithium iron phosphate, lithium manganese oxide, and lithium polymer battery.
There are three main packaging forms of mainstream lithium batteries, namely cylinder, square and soft package. Rectangular lithium batteries usually refer to aluminum or steel prismatic batteries, and the penetration rate of prismatic batteries is very high in China. The structure of the prismatic battery is relatively simple, unlike the cylindrical battery, which uses high-strength stainless steel as the shell and has accessories such as explosion-proof safety valves, so the overall accessories are light in weight and relatively high in energy density.
The structure of a square lithium battery
The main components of a typical prismatic lithium battery include: a top cover, a casing, a positive plate, a negative plate, a stack or winding of separators, insulating parts, safety components, etc.
Acupuncture safety device. This is to add a metal layer, such as copper foil, to the outermost of the core. When acupuncture occurs, the local high current generated at the acupuncture site quickly reduces the current per unit area through the large-area copper sheet, which can prevent the local overheating of the acupuncture site and slow down the thermal runaway of the lithium battery.
Overcharge safety protection device, this safety design can be seen on many batteries at present. Generally, it is a metal sheet, which is used with a fuse (fuse). The fuse can be designed on the positive current collector. When the lithium battery is overcharged, the pressure generated inside the lithium battery causes the overcharge safety protection device (OSD, Overcharge Safety Device) to trigger an internal short circuit, resulting in an instant Large current, so that the Fuse is fused, thereby cutting off the internal current loop of the battery.
The casing is generally a steel casing or an aluminum casing. Driven by the market's pursuit of energy density and the progress of the production process, the aluminum casing has gradually become the mainstream.
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What are the advantages and disadvantages of square lithium batteries
Advantages: Reliability of square lithium battery packaging is high; system energy efficiency is high; relative light weight, high energy density; relatively simple structure, relatively convenient expansion, is currently an important option to increase energy density by increasing monomer capacity; monomer capacity If the system is large, the system structure is relatively simple, which makes it possible to monitor the monomers one by one; another advantage brought by the simplicity of the system is that the stability is relatively good.
Disadvantages: Since the square lithium battery can be customized according to the size of the product, there are thousands of models on the market, but because of too many models, it is difficult to unify the process; the level of production automation is not high, and the differences in monomers are large Large, in large-scale applications, there is a problem that the life of the system is much lower than that of the monomer.
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