Lithium-ion batteries are divided into square lithium batteries (such as commonly used cell phone battery cells), column lithium batteries (such as 18650, 18500, etc.) and button lithium batteries by shape; lithium batteries are divided into aluminum-shell lithium batteries, steel-shell lithium batteries, soft pack batteries by outer package material; lithium cobalt acid, lithium iron phosphate, lithium manganate, lithium polymer by cathode material.
At present, there are three main forms of mainstream lithium battery package, namely cylindrical, square and soft package. Square lithium battery usually refers to aluminum or steel case square battery, the popularity of square battery is very high in China. The structure of the square battery is simpler, unlike the cylindrical battery that uses stainless steel with higher strength as the shell and accessories such as explosion-proof safety valves, so the overall weight of the accessories is lighter and the relative energy density is higher.
Structure of square lithium battery
A typical square lithium battery, the main components include: top cover, shell, positive plate, negative plate, diaphragm consisting of laminated or wound, insulating parts, safety components, etc.. Among them, the two in the red circle are the safety structure, NSD pinprick safety device; OSD overcharge protection device.
Pinprick safety protection device. This is a metal layer, such as a copper sheet, added to the outermost part of the coil core. When a pinprick occurs, the local high current generated at the pinprick location is quickly reduced by the large area of the copper sheet, which prevents local overheating at the pinprick location and reduces the thermal runaway of the lithium battery.
Overcharge safety protection device, the current safety design can be seen on many batteries. Generally a metal sheet, with the use of fuse, fuse can be designed to the positive collector fluid, overcharge the internal pressure generated by the lithium battery makes the OSD trigger an internal short circuit, resulting in an instantaneous high current, so that the Fuse fuse, thereby cutting off the internal current circuit of the battery.
The shell is generally steel or aluminum, with the market driven by the pursuit of energy density and the progress of the production process, aluminum shell gradually become mainstream.
What are the advantages and disadvantages of square lithium battery?
Advantages, high reliability of square lithium battery package; high energy efficiency of the system; relatively light weight, high energy density; simpler structure, relatively easy to expand, is an important option to improve energy density by increasing the capacity of a single cell; large capacity of a single cell, the system composition is relatively simple, making it possible to monitor the single cell one by one; another benefit of a simple system is relatively good stability.
Disadvantages, because the square lithium battery can be customized according to the size of the product, so there are thousands of models on the market, and precisely because there are so many models, it is difficult to unify the process; the level of production automation is not high, the variability of the single cell is large, and in large-scale applications, there is the problem that the system life is much lower than the life of the single cell.
