Date: 2025-02-24 hits: 129
In the production process of lithium batteries, there are often black marks or black spots on the pole plate, especially the negative pole plate is more likely to appear black spots, which not only affects the performance of the battery, but also affects the appearance of the battery.
The following is an analysis of the causes of black marks and the development of corresponding solutions.
A、 Analysis of Process Reasons
（1） Cause analysis
1. Material problems: The quality of materials used to manufacture lithium batteries has a great impact on the performance and appearance of batteries.
If the raw materials purchased are of poor quality, or if the materials have not been adequately inspected and tested before use, problems such as black marks or black spots may occur.
2. Coating process problems: The coating process is an important part of the manufacturing of lithium batteries, if there is an anomaly in the coating process, such as the coating speed is too fast or too slow, the concentration of the coating liquid is not appropriate, and the maintenance of the coating machine is improper, it may lead to black marks or black spots.
3. Drying process problems: In the manufacturing process of lithium batteries, the drying process is also very important.
If the drying temperature is too high or too low, and the drying time is too short or too long, it may lead to black marks or black spots on the pole sheet.
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, it may also lead to black marks or black spots on the pole sheet.
5. Human operation problems: in the production process, if the operator's skill level is insufficient or the work attitude is not serious, it may also lead to black marks or black spots on the pole.
( 2 ) Solution
1. Strict control of raw material quality: strict quality inspection and control of the purchased raw materials to ensure that the quality of the purchased raw materials meets the requirements.
At the same time, regular quality checks should also be carried out on 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 coating speed, coating liquid concentration and other parameters to ensure the stability and reliability of the coating process.
At the same time, strengthen the maintenance and maintenance of the coater to prevent black marks or black spots caused by the failure of the coater.
3, optimize the drying process: through continuous testing and adjustment, find the most suitable drying temperature and drying time and other parameters to ensure the stability and reliability of the drying process.
At the same time, strengthen the maintenance and maintenance of drying equipment to prevent black marks or black spots caused by the failure of drying equipment.
4, control environmental conditions: strict control of 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 health management of the workshop to prevent black marks or black spots caused by environmental problems.
5, improve the skill level and working attitude of the operators: through training and assessment, improve the skill level and working attitude of the operators to ensure that they can operate in strict accordance with the process requirements in the production process to prevent black marks or black spots caused by human operation problems.
6, strengthen the construction of quality management system: establish a sound quality management system, strict monitoring and management of each link in the production process, to ensure that the quality of each link meets the requirements.
At the same time, strengthen the feedback and processing mechanism of quality information to find and solve quality problems in time.
B. Electrochemical Analysis and Solutions for Black Spots on Negative Electrode Plates
(1) Cause analysis
1. The negative electrode plays a crucial role in storing and releasing lithium ions in lithium-ion batteries, and its degree of graphitization and graphite interlayer spacing have a significant impact on battery performance. The low degree of graphitization or small interlayer spacing of the negative electrode will directly affect the insertion and diffusion of lithium ions in graphite. This not only affects the capacity and charge discharge performance of the battery, but may also lead to the phenomenon of graphite having no or little lithium.
2. The PC component in the electrolyte undergoes a co intercalation reaction with the active lithium consumed in the film-forming and solvent processes, which is a complex chemical process. Simply put, when the PC component in the electrolyte reacts with active lithium, it can hinder the insertion of active lithium between graphite particle layers. 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. The residual moisture in the battery is also an undeniable factor. Moisture can dissociate CMC (carboxymethyl cellulose) to form Na+complexes. This process will intensify the intercalation reaction of graphite, further affecting the insertion and diffusion of lithium ions. At the same time, residual moisture will react with the electrolyte, producing gas and causing electrolyte decomposition. The decomposition of electrolyte not only reduces the effective capacity of the battery, but also may cause graphite peeling from the negative electrode, forming a large amount of black slag like material. The combined effect of these conditions is the main reason for the formation of black slag in the negative electrode. These black residues not only affect the appearance and consistency of the battery, but may also pose a potential threat to the performance and safety of the battery.
4. In low-temperature environments, the charging and discharging performance of batteries will face greater challenges. Low temperature storage or low temperature (0 ° C and below) charging and discharging can lead to difficulties in lithium removal 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, making it more difficult for lithium ions to embed into the graphite layer. At the same time, low temperature can also increase the internal resistance of the battery, leading to a decrease in charging and discharging currents. These toxic factors work together to reduce the capacity of the battery, deteriorate its charging and discharging performance, and may even cause more serious side reactions, further worsening the internal point problem.
（2） Solution
To solve these problems, we need to start from multiple aspects and conduct in-depth research and experiments.
1. Optimizing the graphitization process of the negative electrode is key. By adjusting process parameters such as temperature and time, the degree of graphitization and graphite interlayer spacing can be improved, thereby enhancing the insertion and diffusion performance of lithium ions. This can not only improve the capacity and charge discharge performance of the battery, but also help reduce the phenomenon of graphite having no or little lithium.
2. Research and development of new electrolyte formulations is also an important research direction. Finding electrolyte components that do not undergo co embedding reactions with PC components can reduce the occurrence of side reactions and improve the embedding efficiency of active lithium between graphite particle layers. In addition, adding some electrical and electrolyte additives that can stabilize the graphite layer structure is also an effective strategy to reduce the severity of graphite intercalation reactions
3. Strictly controlling the moisture content during battery production is also crucial. Reducing the moisture content in the battery can avoid the exacerbation of graphite intercalation reaction and electrolyte decomposition caused by CMC dissociation. This requires strengthening quality control in the production process to ensure that the moisture content at each stage meets the standard requirements.
4. The management of battery performance in low-temperature environments also needs to be given attention. In low-temperature environments, appropriate charging and discharging strategies should be adopted, such as reducing current density and extending charging time, to reduce the difficulty of lithium removal and the exacerbation of side reactions. This helps to maintain the stability and safety of battery performance. In summary, the reasons for the formation of black slag in negative electrode sheets are multifaceted. This problem can be effectively solved by optimizing the graphitization process of negative electrode sheets, developing new electrolyte formulations, controlling moisture content, and managing the performance of batteries in low-temperature environments.
C. Conclusion
Based on the above analysis and proposed solutions, we can conclude that the causes of black marks on lithium electrode sheets are multifaceted, including material issues, coating process issues, drying process issues, environmental issues, and human operation issues. To solve this problem, we need to strictly control the quality of raw materials, optimize coating and drying processes Starting from multiple aspects such as controlling environmental conditions, improving the skill level and work attitude of operators, and strengthening the construction of quality management system 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.
