The function of adhesives
- Provide viscosity to ensure that particles in the slurry do not easily settle and maintain slurry stability
- Provide viscosity for good fluidity
- Provide viscosity to facilitate effective dispersion of materials
- Good adhesion to metal foils and will not peel off the metal foils due to the use of electrolyte, charging, and discharging.
- Good electrochemical stability within a wide voltage range.
- High melting point and a low swelling rate. Even under high temperatures, the combined structure of the adhesive and the active material needs to remain stable. Adhesives usually undergo swelling, and if the swelling exceeds a certain degree, it will affect the conductivity between the active material and the current collector, leading to capacity fade of the battery. Therefore, it is necessary to control its swelling rate.
- Excellent ion transport properties and electronic conductivity.
- Provide adhesive force to ensure good contact between active materials, conductive carbon, and current collectors.
- Provide adhesive force to ensure good contact between particles.
- The rolling process is resistant to deformation and breakage.
Common classifications of adhesives
(1)Commonly Used adhesives:
PVDF— Commercially Used Cathode adhesive
CMC,SBR—Commercially Used Anode adhesive
PTFE—Adhesive for Supercapacitors
(2) New adhesives
PAA—High-Strength Silicon Anode adhesive
PAN—Improved Rate Capability and Low-Temperature Performance
PMMA—Experimental Type PAI—Experimental Type
PI—Experimental Type
PVA(Polyvinyl Alcohol) —Experimental Type
Sodium Alginate – Experimental Type
PVDF
PVDF is a polymer material with a high dielectric constant. It exhibits excellent chemical stability, temperature characteristics, mechanical properties, and processability, which positively contribute to enhancing bonding performance. PVDF is widely used in lithium-ion batteries as an adhesive for both positive and negative electrodes. The PVDF monomer consists of two hydrogen atoms and two fluorine atoms (—CH2—CF2). The electrons of the hydrogen atoms tend to be biased towards other atoms, making them donors. The covalent bond electron cloud is biased towards the fluorine atoms, thus fluorine atoms are referred to as acceptors. Among the crystalline forms of PVDF, the α-form is the most stable, while the remaining part is amorphous. The amorphous region serves as a good matrix for polar molecules, allowing lithium ions to penetrate through the swollen thin layer of PVDF.
CMC
CMC can effectively increase the viscosity of the slurry,improve its fluidity, and enhance the coating appearance.
SBR
SBR plays a binding role in the electrod
SBR is insoluble in water, it exists in the form of an emulsion
Physical Properties Parameters
Testing methods (industry standard)
The above four methods are the most commonly used adhesive testing methods in the industry
The swelling of the adhesive can be tested by making the adhesive into a sheet and then soaking it in electrolyte
The ionic conductivity of the adhesive can be analyzed by making it into a battery and conducting EIS testing
Development directions
Functionalization
1. Improvement in rate performance and low-temperature performance
2. Enhanced adhesive strength
3. High energy density (low usage)
4. Suppression of expansion (surface coating – such as silicon anode, lithium-sulfur)
Low cost
1. Low cost or reduced usage
Easier processing
1. Better solubility
2. Flexible electrode for easy rolling
Common issues in slurry coating
Company introduction
Welcome to Canrd Company (Canrd stands for “Creating Avenues for New Research Development”，website: www.canrd.com ). We specialized in:
- Electrochemical experiment consumables, including coin cell cases, cathodes, anodes, electrodes, electrolytes, and various other materials.
- Battery cell research and development outsourcing, offering Custom-made electrodes, dry cells, finished battery cells, and battery cell testing.
- Test line equipment, such as coin cell equipment lines, pouch cell test lines, cylindrical cell test lines, and more.
We have strong research and development capabilities.If you are interested, please feel free to contact us at any time.
Phone：+86 19867737979
Email：contact@canrd.com
Wechat：contactcanrd
Leave a Reply