Discussion on the Liquid Injection Means of Soft Pack Battery

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2019-12-30

With the development of social science and technology, there are two kinds of liquid injection methods used in soft pack batteries. Next, by the small series for everyone to introduce, soft pack battery electrolyte two kinds of liquid injection means what.

1. One is to place the pressed semi-finished positive and negative electrodes and diaphragm batteries in the electrolyte for static absorption, and then place them at a temperature of 50~60 degrees Celsius for several hours. After the porous electrode fully absorbs the electrolyte, it is taken out, and the excess electrolyte is squeezed out before assembling with the aluminum plastic case.

2. The second is to press the semi-finished products directly into the aluminum plastic shell, and then encapsulate the aluminum plastic shell after injecting the electrolyte into the battery by means of liquid injection.

Although the above two methods have disadvantages to varying degrees. But there are certain benefits. What are the specific shortcomings?

1. The first method adopts static absorption. Although high temperature is conducive to the diffusion of electrolyte in porous medium, it still cannot avoid the problem that electrolyte cannot penetrate into the porous electrode due to the existence of air, and cannot guarantee the consistency of battery infiltration, which will lead to serious uneven distribution of electrolyte and affect the formation of SEI film. During the subsequent use of the battery, charge and discharge increase ohmic polarization, electrochemical polarization, and concentration polarization, and during charge and discharge, side reactions occur to generate gas, and a stable SEI film cannot be formed.

2. After the second method uses LBM (lattice Bloztamnn) fluid mechanics simulation, it is found that the phenomenon of uneven distribution of electrolyte will still occur. At the end of the flow, the diffusion of electrolyte in the porous electrode is slow due to the small flow rate and pressure difference, while the diffusion speed of electrolyte between the positive and negative electrodes and the diaphragm is inconsistent due to the differences in porosity and porous medium morphology, the faster diffusing channels will surround the slower diffusing channels, forming air traps, affecting the local SEI film formation. Therefore, it is of great technical and scientific value to improve the consistency, electrical performance and safety performance in the production process of soft-pack lithium-ion power battery, and to study the new soft-pack battery injection system and injection method.