1.Coating Basics
Purpose: To uniformly coat a fluid slurry onto the surface of a metal foil, dry it, and produce a battery electrode
Principle: The coating roller rotates to carry the slurry, and the amount of slurry transferred is adjusted by adjusting the gap between the doctor blade and the roller. The relative rotation of the back roller and the coating roller is used to transfer the slurry onto the substrate. Subsequently, the solvent in the slurry is evaporated through drying and heating, causing the solid matter to adhere to the substrate.
Note: Taking transfer coating as an example
2.Blade Coating-1
3.
Blade Coating-2
4.Dip Coating
5.Rolling
Suitable for situations with very few materials, with poor coating uniformity and poor battery consistency
6.Common current collectors
There are many types of current collectors, and their selection depends on different material systems and applications.
7.Selection of Current Collectors for Supercapacitors
There are many types of current collectors, which need to be selected based on different material systems and applications.
Taking supercapacitors as an example
8.Common issues
9.Canrd Brief Introduce
Canrd use high battery R&D technology(core members are from CATL) and strong Chinese supply chain to help many foreign companies with fast R&D. We provide lab materials, electrodes, custom dry cells, material evaluation, perfomance and test, coin/pouch/cylindrical cell equipment line, and other R&D services.
Email： contact@canrd.com Phone/Wechat/WhatsApp： +86 19867737979
Canrd Official Web Canrd Company Vedio Canrd Company profile
Website : www.canrud.com
10. Q & A
In the Q&A session, everyone actively raised questions, and Dr. Ke provided detailed answers to each of them.
Jerusalem Artichoke:
"Hello, during the coating process, the lateral distribution of surface density is always lighter on the sides and heavier in the middle. After single-sided drying, the edges curl up severely. What is the reason for this? The same issue happens with slot-die coating."
Dr. Ke:
"Uneven weight distribution during coating is often related to the scraper. After long-term use and wear, the edges tend to be lighter while the center is heavier. As for the curling during single-sided drying, it is usually due to a low solid content in the slurry, leading to significant shrinkage during drying. Additionally, drying too quickly can exacerbate the issue. We’ll discuss this in detail later."
Lee:
"What is the recommended heating rate during drying? Can the coated material be left overnight without drying?"
Dr. Ke:
"In industrial settings, ovens are pre-set with a temperature profile: preheating, holding, and cooling phases. It is recommended to dry the coated material immediately and not leave it overnight. In the lab, place the coated films directly in the oven, ensuring no vacuum is applied and the temperature is not too high. For coated electrodes, avoid leaving them overnight and dry them right away. For instance, oil-based cathodes are prone to absorbing moisture and should be dried promptly."
Hunan Soft Pack Power Technology:
"Do both cathodes and anodes exhibit pinholes? I’ve only heard of pinholes on anodes."
Dr. Ke:
"In principle, pinholes can occur wherever there are foreign particles, so both cathodes and anodes can have them. However, anode coating issues are generally more common than those with cathodes."
Hunan Soft Pack Power Technology:
"Why can soft particles pass through a sieve?"
Dr. Ke:
"Soft particles are usually soft agglomerates. Under pressure, they can be squeezed through the sieve."
Could This Be Love:
"For the same material, if the particle size is reduced, how should slurry sedimentation be handled?"
Dr. Ke:
"The reason is likely that the reduced particle size increases the surface area, requiring more binder to adhere the particles together. You’ll need to increase the binder content."
Hei Hei:
"Dr. Ke, can soft particles also cause discontinuous streaks?"
Dr. Ke:
"Yes, both soft and hard particles can clog the coating nozzle, leading to streaks during coating."
Lee:
"Does thickening after grinding affect material performance?"
Dr. Ke:
"Grinding can damage the structure of active material particles, which is especially detrimental to coated materials. For coated materials, grinding for dispersion is generally not recommended. This was discussed in our first and second lectures, which you can review on the 'Korod' WeChat public account."
Lee:
"Why does slurry produced with the same ratio have different viscosities when ground versus mixed?"
Dr. Ke:
"This requires case-specific analysis. Grinding and mixing can impact active materials differently. During grinding, the slurry might have a higher solid content due to the larger evaporation area."
Hei Hei:
"Are conductive agents prone to agglomeration?"
Dr. Ke:
"In industrial production, active materials are generally easier to disperse. The main issue lies with conductive carbon or binders that haven’t dissolved effectively, leading to poor dispersion."
Jerusalem Artichoke:
"Dr. Ke, how should slurry rheology be analyzed?"
Dr. Ke:
"You can use a rheometer for testing. For companies, the simplest method is to use a slurry that is performing well in mass production as a control group. Then, compare it using a rheometer to analyze the relationship between viscosity and time, as slurry stability is always relative."
Nanjing University – Lithium Battery:
"Why do different graphite materials result in significantly different viscosities when using the same formulation?"
Dr. Ke:
"Each type of graphite requires some formula optimization to achieve its best performance. Similarly, compaction density, electrolyte compatibility, and overall processes may vary."
Jerusalem Artichoke:
"How can excessive coating stress be effectively mitigated? Should alcohol solvents be added?"
Dr. Ke:
"Adding alcohols is one possible method. For example, NMP can be added to the anode slurry."
Offline Angel:
"Does a larger surface area require a relatively higher binder content?"
Dr. Ke:
"Generally, yes. However, in industrial production, very fine active materials (e.g., micro-nano scale) are rarely used due to their high dispersion difficulty and increased side reactions with the electrolyte, which degrade material performance."
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