When the production of lithium-ion batteries, when the production of the pole piece is completed, the process of winding or stacking will be used to assemble the positive and negative electrode pieces and diaphragm of lithium-ion batteries into cells, after which the cells will be hot pressed into shape, and the lithium battery PACK factory briefly introduces the main points and purposes of these processes.
First, the purpose of the process
Whether winding or Z-stack, the diaphragm will generate tension, and in the process will make the diaphragm way to go elongated, resulting in the diaphragm to go in the direction of shrinkage increases, the diaphragm will squeeze the pole piece, the core will be deformed, deformation of the core appearance of poor flatness, diaphragm internal wrinkle defects, the finished lithium-ion battery will have low capacity, poor cycling performance self discharge failure and other problems. This phenomenon is especially obvious in the winding process, the consistency of the cell will also become poor. Will also increase the difficulty of the cell into the shell.
Hot pressing shaping has two main purposes.
1) to improve the flatness of the lithium-ion battery surface, improve the quality of the cell, so that the cell size and other parameters of a high degree of consistency.
(2) eliminate the diaphragm fold, squeeze out the internal gas, so that the diaphragm and the positive and negative pole piece closely together, shorten the lithium ion diffusion distance, reduce the internal resistance of the battery.
Second, the process of hot pressing and shaping of electric cells is as follows.
The core to be processed is placed on the template, set the booster cylinder pressure and template temperature, so that the core is shaped under a certain temperature and pressure.
During the hot pressing and shaping of the cell, the cell is tested for insulation voltage at the same time to detect whether there is a micro short circuit inside the cell.
Third, the main points of the process
The main process parameters of core hot pressing and shaping are pressurization pressure, pressurization time and template temperature. Under the suitable process parameters, there is almost no air inside the thick cell, the diaphragm and the pole piece are closely bonded together, and the loose cell can become a hard block.
Diaphragm is the core component of the battery, isolating the positive and negative electron conduction of lithium batteries, while allowing the reciprocal passage of lithium ions between the two poles, the microporous structure of the diaphragm is an important channel for these ions to and from the positive and negative poles, its breathable performance will directly affect the performance of the battery. If the permeability of the diaphragm is not good, it will affect the conduction of lithium ions between the positive and negative electrodes, affecting the charging and discharging of lithium batteries.
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