Date: 2025-06-12 hits: 106
A. Introduction
The safety of lithium batteries has always been one of the key factors restricting their widespread application, among which the leakage problem is particularly prominent. Leakage will not only lead to a decline in battery performance, but may also cause safety hazards and economic losses such as short circuits and fires. Therefore, in-depth research on the leakage problem in the manufacturing process of lithium battery cells is of great significance to improving the safety and reliability of lithium batteries.
B. Overview of lithium battery cell manufacturing process
The manufacturing of lithium battery cells mainly includes the preparation of positive electrode materials, the preparation of negative electrode materials, the preparation of diaphragms, the assembly and formation of cells. Among these links, any problem may lead to leakage. For example, in the preparation process of positive electrode materials, if the purity of the raw materials is not enough or the particle size distribution is uneven, it will cause the diaphragm to be perforated or the pole piece to be deformed in the subsequent cell assembly, causing leakage. In the cell assembly process, if the connection process is improper or the use of sealant is not standardized, it will also cause the battery shell to be poorly sealed, and then leakage will occur.
C. Causes of leakage
1. Material factors
(1) Poor quality of diaphragm; diaphragm is an important component of lithium battery, and its main function is to isolate the positive and negative electrodes and allow lithium ions to pass through. If the mechanical strength of the diaphragm is insufficient, the porosity is inappropriate, or there are tiny defects such as pinholes or cracks, it may be penetrated by lithium dendrites during the battery charging and discharging process, resulting in a short circuit between the positive and negative electrodes and leakage.
(2) Shell material defects: Lithium battery shells are usually made of aluminum or steel, and their quality directly affects the sealing of the battery. If the shell material has problems such as sand holes, cracks or uneven thickness, leakage will occur during the use of the battery.
2. Process factors
(1) Improper welding process: In the process of battery cell assembly, the welding process is crucial. If the welding current is too large or the welding time is too long, it will cause the shell to deform or the weld to crack, causing leakage. In addition, inaccurate welding position or loose welding will also cause the battery sealing to decrease, increasing the risk of leakage.
(2) Inaccurate control of injection volume: During the process of injecting liquid into the battery cell, if the injection volume is too much or too little, it will have an adverse effect on the battery performance. Too much injection may cause the internal pressure of the battery to increase and destroy the sealing of the battery; too little injection will affect the performance and life of the battery.
3. Equipment factors
(1) Insufficient precision of injection equipment: The precision of injection equipment directly affects the accuracy of injection volume. If the precision of injection equipment is not high, it may cause large fluctuations in injection volume and cause leakage.
(2) Aging of assembly equipment: Aging of assembly equipment may lead to decreased assembly precision and affect the sealing of the battery. Wear or inaccurate positioning of assembly equipment molds may cause excessive assembly gap between battery shell and pole piece and cause leakage.
D. Impact of leakage on battery performance
1. Safety issues
Leakage will cause the electrolyte inside the battery to come into contact with moisture and oxygen in the air, causing chemical reactions and generating heat and gas. These heat and gases may cause the internal pressure of the battery to rise sharply, causing battery expansion and posing serious safety hazards.
2. Performance degradation
Leakage will cause the loss of electrolyte and affect the electrochemical performance of the battery. The loss of electrolyte will reduce the capacity and cycle life of the battery, and will also increase the internal resistance of the battery, affecting the charging and discharging efficiency of the battery.
3. Shortened life
Leakage will cause changes in the chemical environment inside the battery and accelerate the aging process of the battery. For example, leakage will cause an increase in moisture inside the battery, promoting the hydrolysis reaction of lithium ions to produce substances such as hydrogen and lithium hydroxide. These substances will further corrode the battery's electrode materials, resulting in a shortened battery life.
E. Measures to solve the leakage problem
1. Optimize material selection
Select high-quality diaphragm materials: Select diaphragm materials with high mechanical strength, high chemical stability and appropriate porosity, which can effectively prevent diaphragm perforation and short circuit.
Strictly control the quality of shell materials: Select high-quality shell materials and strictly control their production process to ensure that the shell materials are free of defects such as sand holes and cracks.
2. Improve process flow
Optimize welding process: By optimizing welding parameters such as welding current, welding time and welding position, the welding quality and the sealing of the battery can be effectively improved.
Precisely control the injection volume: Use high-precision injection equipment and strictly control the parameters during the injection process, such as injection speed and injection pressure, which can effectively ensure the accuracy of the injection volume.
3. Strengthen equipment maintenance
Regularly maintain the injection equipment: Regularly maintain and calibrate the injection equipment to ensure its accuracy and stability.
Timely update assembly equipment: Timely update aging or insufficiently accurate assembly equipment to improve assembly accuracy and battery sealing.
F. Conclusion
The leakage problem in the manufacturing process of lithium battery cells is a complex systemic problem involving multiple aspects such as materials, processes and equipment. By optimizing material selection, improving process flow and strengthening equipment maintenance, the probability of leakage problems can be effectively reduced and the safety, reliability and service life of lithium batteries can be improved.
