Date: 2025-07-23 hits: 107
A. Introduction
During the production process of lithium batteries, black marks (spots) often appear on the pole pieces, especially the negative pole pieces are more prone to black spots, which not only affects the performance of the battery
but also affects the appearance of the battery. Now let's discuss with you the reasons for the black marks on the lithium electrode pieces and formulate corresponding solutions.
B. Process cause analysis
(I) Cause analysis
1. Material problem: The quality of the materials used to manufacture lithium batteries has a great impact on the performance and appearance of the battery. If the purchased raw materials are of poor quality, or the materials are not fully inspected and tested before use, black marks or black spots may appear.
2. Coating process problem: The coating process is an important link in the manufacture of lithium batteries. If there are abnormalities in the coating process, such as too fast or too slow coating speed, inappropriate concentration of coating liquid, improper maintenance of coating machine, etc., it may cause black marks or black spots on the pole pieces.
3. Drying process problem: In the manufacturing process of lithium batteries, the drying link is also very important. If the drying temperature is too high or too low, the drying time is too short or too long, it may cause black marks or black spots on the pole pieces.
4. Environmental issues: The environment of the production workshop will also affect the manufacturing quality of lithium batteries. If the air humidity, temperature and other conditions in the workshop are not properly controlled, black marks or black spots may appear on the pole pieces.
5. Human operation issues: During the production process, if the operator's skill level is insufficient or his work attitude is not serious, black marks or black spots may also appear on the pole pieces.
(II) Solution
1. Strictly control the quality of raw materials: Carry out strict quality inspection and control on the purchased raw materials to ensure that the quality of the purchased raw materials meets the requirements. At the same time, regular quality inspections should be carried out on the raw materials during the production process to prevent black marks or black spots caused by raw material problems.
2. Optimize the coating process: Through continuous testing and adjustment, find the most suitable parameters such as coating speed and coating liquid concentration to ensure the stability and reliability of the coating process. At the same time, strengthen the maintenance and maintenance of the coating machine to prevent black marks or black spots caused by coating machine failure.
3. Optimize the drying process: Through continuous testing and adjustment, find the most suitable parameters such as drying temperature and drying time to ensure the stability and reliability of the drying process. At the same time, strengthen the maintenance and maintenance of the drying equipment to prevent black marks or black spots caused by drying equipment failure.
4. Control environmental conditions: Strictly control the environment of the production workshop, including air humidity, temperature, etc., to ensure that the production environment meets the requirements. At the same time, strengthen the cleaning and sanitation management of the workshop to prevent black marks or black spots caused by environmental problems.
5. Improve the skills and work attitude of operators; through training and assessment, improve the skills and work attitude of operators to ensure that they can strictly follow the process requirements during the production process to prevent black marks or black spots caused by human operation problems.
6. Strengthen the construction of the quality management system: Establish a sound quality management system, strictly monitor and manage each link in the production process, and ensure that the quality of each link meets the requirements. At the same time, strengthen the feedback and processing mechanism of quality information to promptly discover and solve quality problems.
C. Electrochemical Causes and Solutions for Black Spots on Negative Electrode Sheets
(I) Cause Analysis
1. Negative electrodes play a key role in storing and releasing lithium ions in lithium-ion batteries, and their graphitization degree and graphite interlayer spacing have an important impact on battery performance. Low graphitization degree or small graphite interlayer spacing of negative electrodes will directly affect the embedding and diffusion of lithium ions in graphite. This not only affects the capacity and charge and discharge performance of the battery, but may also lead to the phenomenon of graphite without lithium or less lithium.
2. The PC component in the electrolyte undergoes a co-intercalation reaction with the active lithium consumed in the film formation and solvent, which is a complex chemical process. Simply put, when the PC component in the electrolyte reacts with the active lithium, the embedding of the active lithium between the graphite particle layers is hindered. This not only reduces the effective capacity of the battery, but may also trigger a series of side reactions, affecting the safety and stability of the battery.
3. Residual moisture in the battery is also a factor that cannot be ignored. Moisture can dissociate CMC (carboxymethyl cellulose) to form a Na+ complex. This process will lead to the intensification of the intercalation reaction of graphite, further affecting the embedding and diffusion of lithium ions. At the same time, the residual moisture will also react with the electrolyte to produce gas and cause the electrolyte to decompose. The decomposition of the electrolyte not only reduces the effective capacity of the battery, but also may cause the graphite of the negative electrode sheet to peel off and form a large amount of black slag-like substances.
The combined effect of these conditions is the main reason for the formation of black slag in the negative electrode sheet. These black slags not only affect the appearance and consistency of the battery, but also may pose a potential threat to the performance and safety of the battery.
4. In low temperature environments, the charging and discharging performance of the battery will be more challenged. Low temperature storage or low temperature (0°C and below) charging and discharging will lead to difficulties in delithiation and intensified side reactions. This is because at low temperatures, the fluidity of the electrolyte deteriorates and the diffusion rate of lithium ions slows down, which makes it more difficult for lithium ions to embed into the graphite layer. At the same time, low temperature will also increase the internal resistance of the battery, resulting in a decrease in charging and discharging current. These factors work together to reduce the capacity of the battery, deteriorate the charging and discharging performance, and may even trigger more serious side reactions, further exacerbating the black spot problem.
(II) Solutions
In order to solve these problems, we need to start from multiple aspects and conduct in-depth research and experiments.
Optimizing the graphitization process of the negative electrode is the key. By adjusting process parameters such as temperature and time, the degree of graphitization and the distance between graphite layers can be improved, thereby improving the embedding and diffusion performance of lithium ions. This can not only improve the capacity and charge and discharge performance of the battery, but also help reduce the phenomenon of graphite without lithium or less lithium. Research and development of new electrolyte formulas is also an important research direction. Finding electrolyte components that do not undergo co-intercalation reactions with PC components can reduce the occurrence of side reactions and the embedding efficiency of highly active lithium between the graphite particle layers. In addition, adding some electrolyte additives that can stabilize the graphite layer structure is also an effective strategy to help reduce the intensity of the graphite intercalation reaction.
Strictly controlling the moisture content during the battery production process is also crucial. Reducing the moisture content in the battery can avoid problems such as aggravated graphite intercalation reactions and electrolyte decomposition caused by CMC dissociation. This requires strengthening quality control during the production process to ensure that the moisture content of each link meets the standard requirements. The management of battery performance in low temperature environments also needs to be taken seriously. In low temperature environment, appropriate charging and discharging strategies should be adopted, such as reducing current density, extending charging time and other measures, to reduce the difficulty of lithium removal and the intensification of side reactions. This helps to maintain the performance stability and safety of the battery.
In summary, there are many reasons for the formation of black slag in the negative electrode sheet, which can be effectively solved by optimizing the graphitization process of the negative electrode sheet, developing new electrolyte formulas, controlling moisture content and managing the performance of the battery in low temperature environment.
D. Conclusion
Through the above analysis and the proposal of solutions, we can draw the following conclusions: There are many reasons for the black marks on lithium electrode sheets, including material problems, coating process problems, drying process problems, environmental problems and human operation problems. In order to solve this problem, we need to start from multiple aspects including strict control of raw material quality, optimization of coating and drying processes, control of environmental conditions, improvement of operator skills and work attitudes, and strengthening of quality management system construction and electrochemical research. Only in this way can we effectively reduce the problem of black marks on lithium electrode sheets and improve the manufacturing quality performance and appearance quality of lithium batteries.
