Black spot problem of lithium battery.Lithium - Ion Battery Equipment

As one of the key components of lithium-ion batteries, copper foil for lithium-ion batteries directly affects battery performance. At present, copper foil for lithium-ion batteries is mostly produced by integrated machines, and anti-oxidation treatment is directly carried out after copper foil production. There are differences in anti-oxidation processes among various manufacturers. The following is an in-depth analysis of the problems of black spots and yellow spots caused by insufficient anti-oxidation ability of copper foil for lithium-ion batteries, and an innovative solution is proposed.（Lithium - Ion Battery Equipment）

I. Problem manifestation


When the anti-oxidation ability is insufficient, there will be black spots and yellow spots in two situations. One is the appearance of oxidized black spots during the low-temperature stress release process; the other is the appearance of oxidized black spots after being stored at room temperature for a period of time.
II. Main reasons

1. Copper ion contamination of anti-oxidation solution:
   • Low current transmission may lead to the accumulation of copper ions in the anti-oxidation solution. The copper ion content in the anti-oxidation solution should be detected daily and generally controlled within 3 ppm. When the copper ion content is higher than 3 ppm, the anti-oxidation current needs to be increased, and 3 - 6A is more appropriate.
   • The increase in copper ions is closely related to incomplete washing of copper foil. Therefore, the pickling and washing links after the copper foil is out of the tank must be done well to ensure the effective removal of copper ions.
2. Unsuitable process formula of anti-oxidation solution:
   • Excessive sugar content will cause adhesion of the subsequent slitting rubber rollers. After accumulating to a certain amount, yellow crystals will appear, seriously affecting the appearance quality of the final product.
   • Excessive chromium content will lead to an increase in chromium residue on the copper foil surface, resulting in problems such as color difference and yellow spots. Therefore, the anti-oxidation process formula needs to be strictly optimized to ensure the appropriate proportion of each component.
3. Insufficient detection means for copper foil anti-oxidation:
   • The quality guarantee period of lithium-ion battery copper foil is three months, but currently the detection methods of various manufacturers are different. Generally, only the performance at 150°C for 10 - 15 minutes is detected, lacking the detection of room temperature storage capacity.
   • In order to accurately evaluate the room temperature storage performance, a constant temperature and humidity chamber should be used for the double 85 experiment verification. Generally, lithium battery copper foil needs to meet the double 85 test for more than 12 hours, and it is best to reach 24 hours to ensure the stability of the product in actual use.
4. Improper maintenance and use of anti-oxidation solution:
   • At present, many manufacturers have the problem of regularly discharging the anti-oxidation solution, which not only increases the pressure on sewage treatment but also increases the production cost.
   • The maintenance of the anti-oxidation solution needs to be improved, including doing well in the links of dissolution and filtration, so as to achieve no need to discharge the solution for several months, reduce costs and reduce the environmental burden.

III. Innovative solutions

1. Establish an intelligent monitoring system: Real-time monitoring of copper ion content, proportion of various components, and parameters such as temperature and current in the anti-oxidation solution. Through data analysis, adjust the process in time to ensure stable anti-oxidation effect.
2. Optimize process formula research and development: Adopt advanced experimental design methods, such as response surface methodology, to systematically optimize the process formula of the anti-oxidation solution to find the best combination of component proportions and reduce the occurrence of problems such as yellow spots and black spots.
3. Strengthen detection standards and methods: Formulate unified detection standards for copper foil anti-oxidation. In addition to traditional high-temperature detection, increase the detection of room temperature storage capacity, introduce more advanced detection equipment and technologies, and improve detection accuracy and efficiency.
4. Develop environmentally friendly anti-oxidation solution: Research new environmentally friendly materials to replace some components in traditional anti-oxidation solutions, reduce environmental impacts, and at the same time improve anti-oxidation performance.
5. Strengthen employee training and management: Improve the understanding and mastery of anti-oxidation processes by operators, strictly implement operating procedures, and ensure the stability and consistency of the production process.

Through the above innovative measures, the anti-oxidation ability of copper foil for lithium-ion batteries can be effectively improved, the occurrence of problems such as black spots and yellow spots can be reduced, and product quality and market competitiveness can be enhanced.