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1300mah 5s battery pole piece coating defects and influencing factors

This is an ultra-detailed introduction to 1300mah 5s battery coating defects and influencing factors. It describes the influencing factors of 1300mah 5s battery coating effect, common defects and solutions of 1300mah 5s battery pole pieces. Interested partners may wish to take a few minutes to visit with the 1300mah 5s battery manufacturer CNHL.
Partners who are not familiar with lithium batteries can click the following to understand the basic information of lithium batteries:
6200mah 6s lipo basic knowledge

Common problems in the coating process of 1300mah 5s battery pole pieces

Reducing coating defects, improving coating quality and yield, and reducing costs during the coating process of 1300mah 5s battery pole pieces are important contents that need to be studied in the 1300mah 5s battery pole piece coating process. The problems that often occur in the coating process of 1300mah 5s battery pole pieces are defects such as thick head and thin tail, thick sides on both sides, dot-shaped dark spots, rough surface, and exposed foil.
The thickness of the head and tail can be adjusted by the switching time of the 1300mah 5s battery pole piece coating valve or the intermittent valve. The thick edge problem can be improved from the properties of the slurry, the adjustment of the coating gap, the flow rate of the slurry, etc. Improve by stabilizing the foil, reducing the speed, adjusting the angle of the air knife, etc.

Factors affecting the coating effect of 1300mah 5s battery pole pieces

1 Substrate - 1300mah 5s battery slurry
The relationship between the basic physical properties of the 1300mah 5s battery slurry and the coating: in the actual process, the viscosity of the slurry has a certain influence on the coating effect. Slurry viscosity is also different.
When the slurry viscosity is too high, the coating of 1300mah 5s battery pole pieces often cannot be carried out continuously and stably, and the coating effect is also affected. The uniformity, stability, edge and surface effect of the coating solution for 1300mah 5s battery pole pieces are affected by the coating solution. The rheological properties are affected, which directly determine the quality of the coating.
Using theoretical analysis, coating experimental technology, fluid mechanics finite element technology and other research methods, the coating window can be studied.
The production of 1300mah 5s battery slurry is described in detail in the following article:
11.1v lipo battery pulping process: types and characteristics of pulping equipment

2 Substrate-1300mah 5s battery copper foil and aluminum foil
Surface tension: The surface tension of the copper-aluminum foil must be higher than the surface tension of the coated solution, otherwise the solution will be difficult to spread evenly on the 1300mah 5s battery substrate, resulting in poor 1300mah 5s battery coating quality.
1) Surface tension of the coating solution
A rule to follow is that the surface tension of the solution to be applied should be 5 dynes/cm lower than that of the substrate, although this is only rough. The surface tension of the 1300mah 5s battery solution and the substrate can be adjusted by formula adjustment or surface treatment of the substrate. Surface tension measurement of both should also be used as a quality control test item.
2) Uniform thickness
In a process similar to blade coating, the thickness of the substrate is not uniform across the profile, resulting in non-uniform coating thickness. Because in the 1300mah 5s battery coating process, the coating thickness is controlled by the gap between the blade and the substrate.
If there is a lower thickness of the substrate in the transverse direction of the substrate, then more solution will pass there and the coating thickness will be thicker, and vice versa. If the thickness fluctuation of the following substrate is seen from the thickness gauge, then the final coated film thickness fluctuation will show the same deviation. In addition, lateral thickness deviation can also lead to winding defects. Therefore, in order to avoid this defect, the thickness control of 1300mah 5s battery raw materials is very important
3) Static electricity
On the coating line, a lot of static electricity is generated on the surface of the substrate when the coating is unwinding and passing through the roll. The generated static electricity can easily absorb the air and the ash layer on the roller, resulting in coating defects. In the process of discharge, static electricity will also cause static-like appearance defects on the coated surface, and even cause fire. If the humidity is low in winter, the problem of static electricity on the coating line will be more serious. The most effective way to reduce such defects is to try to keep the ambient humidity in a relatively high state, ground the coating line, and install some antistatic devices.
4) Cleanliness
Impurities on the surface of the substrate will cause some physical defects, such as bumps, contamination and so on. Therefore, it is necessary to better control the cleanliness of raw materials in the production process of the substrate. In-line film cleaning rollers are a more effective method of removing substrate impurities. Although not all impurities on the membrane can be removed, it can effectively improve the quality of raw materials and reduce losses.

Common defects of 1300mah 5s battery pole pieces

【1】Bubble defects in the negative electrode coating of lithium batteries
The negative electrode sheet with bubbles on the left, and the scanning electron microscope on the right at 200 times magnification. In the process of mixing, transporting and coating, foreign matter such as dust or long fluff is mixed into the coating solution or falls on the surface of the wet coating, where the surface tension of the coating is affected by external forces, resulting in intermolecular forces Changed, the slurry was slightly transferred, and after drying, a circular trace was formed, and the middle was thin.
【2】Pinhole
One is the generation of bubbles (stirring process, transportation process, coating process); pinhole defects caused by bubbles are relatively easy to understand. The bubbles in the wet film migrate from the inner layer to the surface of the film, and rupture on the surface of the film to form pinhole defects. The bubbles mainly come from the stirring of lithium batteries, the transportation of coating liquid, and the poor fluidity of the coating during the coating process, poor leveling, and poor release of bubbles from the coating.
【3】Scratches:
Possible reasons: foreign objects or large particles are stuck in the slit gap or on the 1300mah 5s battery coating gap, the quality of the substrate is poor, causing foreign objects to block the coating gap between the coating roller and the back roller, and the die lip is damaged
【4】Thick edge:
The reason for the thick edge is driven by the surface tension of the 1300mah 5s battery slurry, which makes the slurry migrate to the uncoated edge of the pole piece, and the thick edge is formed after drying.
【5】Aggregate particles on the surface of negative electrode of 1300mah 5s battery
Formula: spherical graphite + SUPER C65 + CMC + distilled water
Macroscopic morphology of the pole piece with two different stirring processes: smooth surface (left) and a large number of small particles on the surface (right)
Formula: spherical graphite+SUPER C65+CMC/SBR+distilled water
Magnified morphologies of small particles on the pole piece surface (a and b): agglomerates of conductive agent, not fully dispersed
Enlarged morphology of the pole piece with smooth surface: the conductive agent is fully dispersed and evenly distributed
【6】Aggregate particles on the surface of positive electrode of 1300mah 5s battery
Formula: NCA+Acetylene Black+PVDF+NMP
During the stirring process, the ambient humidity was too high, resulting in the jelly state of the 1300mah 5s battery slurry, the conductive agent was not completely dispersed, and there were a large number of particles on the surface of the pole piece after rolling.
【7】Aqueous pole piece crack
Formulation: NMC532/carbon black/binder= 90/5/5 wt%, water/isopropyl alcohol (IPA) solvent
Optical photos of cracks on the surface of the 1300mah 5s battery pole piece, with coating surface densities of (a) 15 mg/cm2, (b) 17.5 mg/cm2, (c) 20 mg/cm2 and (d) 25 mg/cm2, respectively, thick pole piece More prone to cracks.
【8】1300mah 5s battery pole piece surface shrinkage
Formula: flake graphite+SP+CMC/SBR+distilled water
The presence of contaminant particles on the surface of the foil, the wet film on the surface of the particle has a low surface tension area, and the liquid film of the 1300mah 5s battery migrates around the particle in a radiating manner, forming shrinkage hole point defects.
【9】Scratches on the surface of the 1300mah 5s battery pole piece
Formula: NMC532+SP+PVdF+NMP
Slit extrusion coating, the presence of large particles on the cutting edge causes leakage foil scratches on the surface of the 1300mah 5s battery pole piece
【10】1300mah 5s battery coating vertical strip
Formula: NCA+SP+PVdF+NMP
In the later stage of coating the transfer 1300mah 5s battery, the water-absorbing viscosity of the slurry increases, and the coating is close to the upper limit of the coating window, the leveling of the slurry is poor, and vertical stripes are formed.
【11】Rolling cracks in the non-dry area of ​​the 1300mah 5s battery pole piece
Formula: flake graphite+SP+CMC/SBR+distilled water
During coating, the middle area of ​​the 1300mah 5s battery pole piece was not completely dry, and the coating migrated during rolling, forming stripe cracks.
【12】Pole piece rolling edge wrinkles
Coating forms thick edge phenomenon, rolling type, the edge of 1300mah 5s battery coating is wrinkled
【13】 1300mah 5s battery anode slitting coating and foil separation
Formula: natural graphite + acetylene black + CMC/SBR + distilled water, the proportion of active substances is 96%,
When the pole disc is cut, the 1300mah 5s battery coating is detached from the foil.
【14】1300mah 5s battery pole piece cutting burr
When the 1300mah 5s battery positive electrode disc is cut, the secondary cutting causes foil burrs due to unstable tension control
【15】1300mah 5s battery pole piece cutting wavy edge
When the 1300mah 5s battery negative pole piece disc is cut, due to the inappropriate overlap and pressure of the cutter, the wavy edge and the cut coating are peeled off.
【16】Other common 1300mah 5s battery coating defects are: air infiltration, transverse wave, vertical flow, Rivulet, expansion, water drop, etc.

Battery defect solution

1300mah 5s battery defects can occur in any processing segment: coating formulation, substrate fabrication, substrate handling coating areas, drying areas, cutting, slitting, rolling processes, etc. What is the general logical method to solve the defects of lithium batteries?
1. In the process from pilot plant to production, it is necessary to optimize the product formula, the process of coating and drying battery defects, and find a better or wide process window.
2. Through some quality control methods, statistical tools (SPC) to control the quality of products. Through online monitoring to control the stable coating thickness, or visual appearance inspection system (Visual System) to check whether the coating surface of battery defects is defective.
3. When product defects occur, adjust the process in time to avoid repeated battery defects.
Well, the above is the whole content of the factors affecting the coating effect of 1300mah 5s battery pole pieces and the causes and solutions of defects brought by CNHL today. I hope it will help you. For more information on lithium batteries, please click below to get: How big is the 6s lipo battery recycling market?

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