Analysis of the Causes of Liquid Leakage of Soft Packed Lithium Batteries

Leakage analysis of soft-packed lithium batteries Today, regarding the corrosion and leakage of soft-packed batteries in the assembly of soft-packed batteries, the important process of battery sealing effect is the packaging process, and the quality of packaging directly determines the performance of the battery. Briefly speaking, the packaging is not very clear, and we need to analyze it in detail from the type of leakage. Generally speaking, the reasons for the corrosion and leakage of aluminum-plastic films can be divided into three categories: (1) Chemical corrosion. For lithium batteries, because water reacts with the electrolyte to attack HF, hydrofluoric acid is particularly corrosive. The strong acid will attack the aluminum plastic film, the collection solution, and the positive electrode data severely. The reaction is as follows: When the film is corroded, the battery will be broken. (2) Electrochemical corrosion It is difficult to find the corrosion leakage of the electrochemical reaction of the soft battery. Generally, with the extension of the use time, the corrosion leakage of the battery will be found to be gradually serious. Due to the long incubation time of this failure form, once it occurs, it is easy to constitute a customer's trust crisis. Electrochemical corrosion generally has two situations: ion short circuit. The aluminum layer of the aluminum film forms an ion short-circuit channel with the anode. Electronic short circuit. The aluminum layer of the aluminum film and the anode form an electronic short-circuit channel. In this way, the aluminum-plastic film aluminum layer of the encapsulated battery forms a short circuit with the anode. The anode is the cathode of the battery, in the low-potential part. Once exposed to aluminum, electrochemical reactions will occur through the highly conductive electrolyte, causing the aluminum layer to continue to be consumed. The two necessary conditions for the battery to be attacked and corroded during short-circuit, both are indispensable. The simple structure of the ion channel is that the PP layer of the sealing part is broken during the heat sealing process, or the PP layer is broken during the folding process, thereby forming an ion channel between the aluminum layer and the negative electrode. The simple composition of the electronic short-circuit channel is: the packaging position of the polar ear is destroyed, and the negative ear is in contact with the aluminum layer to form an electronic channel. If the cathode extends too long, it is easy to form direct contact with the aluminum layer during heat sealing, forming an electronic short circuit. In addition to the electronic channels inside the battery, the external contact between the negative tab and the aluminum layer is also one of the reasons for the corrosion and leakage of the soft package. This happens faster. When ion channels and electronic channels are formed, the aluminum-layer aluminum-plastic film gradually intercalates lithium ions to form an aluminum-lithium alloy. The water after the corrosion of the aluminum layer can immerse in the battery unscrupulously, attacking more serious damage, and causing the appearance of the soft pack battery leakage failure. (3) Physical reasons. Due to improper use of the battery and accidental bumping, the battery itself will swell and the packaging will fail, which will also cause the battery to leak. Misuse of the battery, including battery overcharge, over discharge, high temperature use, etc., can cause gas to appear in the battery, and swelling can aggravate the packaging failure. No matter the battery is used in normal temperature cycle, high temperature cycle, or high temperature, it will produce different degrees of inflation and gas production. According to the current research results, the essence of cell fouling is caused by the explosion and differentiation of the electrolyte. There are two conditions for electrolyte differentiation. Electrolyte impurities, such as water and metal impurities, gas electrolyte differentiation, and the other is a low electrolyte electrochemical window, which constitutes the differentiation in the process of charging, EC electrolyte, December, such as solvent Get electrons, free radicals will attack, and directly lead to free radical reactions such as low-boiling hydrocarbons, esters, ethers and carbon dioxide. If there is too much water in the battery, it will also cause more gas to appear, forming the battery drum, and forming the weak part of the package to break. Disclaimer: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete.