Common faults and solutions in coating.Lithium - Ion Battery Equipment

In the production process of lithium batteries, the coating stage is crucial. However, various faults often occur during the coating process, affecting production efficiency and product quality. Today, let's take an in-depth look at 25 common faults and solutions in lithium battery coating.(Lithium - Ion Battery Equipment)

I. Relevant factors for fault generation
There are many factors affecting coating quality, mainly including people, machines, materials, methods, and environment. The basic factors are directly related to the coating process and cover coating substrates, adhesives, coating steel rollers/rubber rollers, and laminating machines.

1. Coating substrate: Material, surface characteristics, thickness and its uniformity will all affect coating quality. How should a suitable coating substrate be selected?
   
2. First of all, in terms of material, it needs to be selected according to the specific application requirements of lithium batteries. Common coating substrates include copper foil and aluminum foil. Copper foil has good conductivity and ductility and is suitable as a negative current collector; aluminum foil has better oxidation resistance and is often used as a positive current collector.
   Secondly, for the selection of thickness, factors such as the energy density and safety of the battery generally need to be considered. A thinner substrate can increase energy density but may reduce the safety and stability of the battery; a thicker substrate is the opposite. At the same time, the uniformity of thickness is also crucial. Uneven thickness may lead to uneven coating and affect battery performance.
3. Adhesive: Working viscosity, affinity and adhesion to the substrate surface are very important.
4. 
5. Coating steel roller: As the carrier of adhesive and the support reference for coating substrate and rubber roller, its geometrical tolerance, rigidity, dynamic and static balance quality, surface quality, temperature uniformity and thermal deformation condition all affect coating uniformity.
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7. Coating rubber roller: Material, hardness, geometrical tolerance, rigidity, dynamic and static balance quality, surface quality, thermal deformation condition, etc. are also important variables affecting coating uniformity.
8. Laminating machine: In addition to the precision and sensitivity of the combined pressure mechanism of coating steel roller and rubber roller, the designed maximum operating speed and the overall stability of the machine cannot be ignored.

II. Common faults and solutions

1. Unwinding deviation limit
   (1) Reason: The unwinding mechanism is threaded without centering.
   (2) Solution: Adjust the sensor position or adjust the reel position in the centered position.
2. Outlet floating roller upper and lower limits
   (1) Reason: The outlet pressure roller is not pressed tightly or the take-up tension is not turned on, and the potentiometer is abnormal.
   (2) Solution: Press the outlet pressure roller tightly or turn on the take-up tension switch and recalibrate the potentiometer.
3. Traveling deviation limit
   (1) Reason: The traveling deviation is not centered or the probe is abnormal.
   (2) Solution: Reset to the center setting and check the probe position and whether the probe is damaged.
4. Take-up deviation limit
   (1) Reason: The take-up mechanism is threaded without centering.
   (2) Solution: Adjust the sensor position or adjust the reel position in the centered position.
5. No opening and closing action of the back roller
   (1) Reason: The back roller has not completed origin calibration or the calibration sensor status is abnormal.
   (2) Solution: Recalibrate the origin or check the status and signal of the origin sensor for abnormalities.
6. Back roller servo failure
   (1) Reason: Abnormal communication or loose wiring.
   (2) Solution: Press the reset button to reset the fault or power on again. Check the alarm code and consult the manual.
7. Second side non-intermittent coating
   (1) Reason: Fiber optic failure.
   (2) Solution: Check whether the coating parameters or fiber optic signals are abnormal.
8. Scraper servo failure
   (1) Reason: Alarm of the scraper servo driver or abnormal sensor status, equipment emergency stop.
   (2) Solution: Check the emergency stop button or press the reset button to eliminate the alarm, recalibrate the origin of the scraper roller and check whether the sensor status is abnormal.
9. Scratch
   (1) Reason: Caused by slurry particles or there is a notch in the scraper.
   (2) Solution: Use a feeler gauge to clear particles and check the scraper.
10. Powder shedding
    (1) Reason:
    a. Powder shedding caused by over-drying;
    b. High humidity in the workshop and water absorption of the pole piece;
    c. Poor adhesion of the slurry;
    d. The slurry has not been stirred for a long time.
    (2) Solution: Contact on-site quality technology.
11. Insufficient surface density
    (1) Reason:
    a. Large height difference of liquid level;
    b. Running speed;
    c. Knife edge.
    (2) Solution: Check the speed and knife edge parameters and maintain a certain liquid level height.
12. More particles
    (1) Reason:
    a. Carried by the slurry itself or precipitated;
    b. Caused by the roller shaft during single-sided coating;
    c. The slurry has not been stirred for a long time (in a static state).
    (2) Solution: Wipe the passing rollers clean before coating. If the slurry has not been used for a long time, consult quality technology to see if it needs to be stirred.
13. Tailing
    (1) Reason: Slurry tailing, non-parallel gap between back roller or coating roller, and back roller opening speed.
    (2) Solution: Adjust the coating gap parameters and increase the back roller opening speed.
14. Front misalignment
    (1) Reason: The alignment parameters are not corrected when there is an alignment error.
    (2) Solution: Check whether the foil is slipping, clean the back roller, press down the reference roller pressure roller, and correct the alignment parameters.
15. Parallel tailing on the reverse side during intermittent coating
    (1) Reason: The distance between the coating back roller is too small, or the back roller opening distance is too small.
    (2) Solution: Adjust the distance between the coating back roller and increase the back roller opening distance.
16. Thick at the head and thin at the tail
    (1) Reason: The head-tail thinning parameters are not adjusted properly.
    (2) Solution: Adjust the head-tail speed ratio and the head-tail starting distance.
17. Changes in coating length and intermittent process
    (1) Reason: There is slurry on the surface of the back roller, the traction rubber roller is not pressed, and the gap between the back roller and the coating roller is too small and too tight.
    (2) Solution: Clean the surface of the back roller, adjust the intermittent coating parameters, and press on the traction and rubber rollers.
18. Obvious cracks on the pole piece
    (1) Reason: Too fast drying speed, too high oven temperature, and too long baking time.
    (2) Solution: Check whether the relevant coating parameters meet the process requirements.
19. Wrinkling of the pole piece during operation
    (1) Reason:
    a. Parallelism between passing rollers;
    b. There is serious slurry or water on the surface of the back roller and passing rollers;
    c. Poor foil joint leading to unbalanced tension on both sides;
    d. Abnormal correction system or correction not turned on;
    e. Excessive or too small tension;
    f. The gap of the back roller pulling stroke is inconsistent;
    g. The rubber surface of the back roller undergoes periodic elastic deformation after a long period of use.
    (2) Solution:
    a. Adjust the parallelism of the passing rollers;
    b. Deal with foreign matters between the back roller and passing rollers in time;
    c. First adjust the tension adjusting roller at the machine head. After the foil is stable, adjust it back to the original state;
    d. Turn on and check the correction system;
    e. Check the tension setting value and whether the rotating of each transmission roller and take-up and pay-off roller is flexible, and deal with the inflexible roller in time;
    f. Expand the gap appropriately and then gradually narrow it to the appropriate position;
    g. When the elastic deformation is serious, replace the new rubber roller.
20. Bulging at the edge
    (1) Reason: Caused by the foam blocking of the baffle.
    (2) Solution: When installing the baffle, it can be in an outward splayed shape or when moving the baffle, it can be moved from outside to inside.
21. Material leakage
    (1) Reason: The foam of the baffle or the scraper is not installed tightly.
    (2) Solution: The gap of the scraper is slightly 10 - 20 microns larger than the thickness of the coating layer. Press the foam of the baffle tightly.
22. Uneven take-up
    (1) Reason: The take-up shaft is not installed properly, not inflated, the correction is not turned on or the take-up tension is not turned on.
    (2) Solution: Install and fix the take-up shaft, inflate the air expansion shaft, turn on the correction function and take-up tension, etc.
23. Uneven blank margins on both sides
    (1) Reason: Installation position of the baffle and the unwinding correction is not turned on.
    (2) Solution: Move the baffle and check the take-up correction.
24. Unable to track intermittent coating on the reverse side
    (1) Reason: No induction input from the fiber optic or no intermittent coating on the front side.
    (2) Solution: Check the detection distance of the fiber optic head, fiber optic parameters, and front coating effect.
25. Correction does not act
    (1) Reason: Incorrect fiber optic parameters, correction switch not turned on.
    (2) Solution: Check whether the fiber optic parameters are reasonable (whether the correction indicator flashes left and right), and whether the correction switch is turned on.

III. Innovative thinking and suggestions
In order to better deal with faults in the lithium battery coating process, we can innovate from the following aspects:

1. Introduce an intelligent monitoring system to monitor various parameters in the coating process in real time and give early warning of possible faults.
2. Develop new coating materials and equipment to improve the uniformity and stability of coating.
3. Strengthen the training of operators to improve their ability to judge and handle faults.
4. Establish a perfect quality control system to conduct comprehensive quality control of the coating process.

In short, understanding common faults and solutions in lithium battery coating is crucial for improving production efficiency and product quality. At the same time, we must also continuously innovate and explore more advanced technologies and methods to make greater contributions to the development of the lithium battery industry.