The mystery of SBR floating blue in 5s lipo battery xt60 slurry

Today, CNHL, a Chinese lipo battery production company, will talk about the blue SBR in the 5s lipo battery xt60 slurry from the perspective of SBR and lithium battery slurry. Interested partners may wish to spend a few minutes to find out.

1 Two optical concepts: Rayleigh scattering, Mie scattering

Light scattering refers to the phenomenon that a part of light passing through an inhomogeneous medium deviates from the original propagation direction. Light that deviates from the original direction is called scattered light. The wavelength (λ) of scattered light does not change is elastic scattering. Common elastic scattering includes Rayleigh scattering and Mie scattering.

2 Why does the 5s lipo battery xt60 paste float blue instead of other colors?

5s lipo battery xt60 SBR itself is not a homogeneous solution, it is a suspension formed by a huge number of small particles suspended in water (we usually call EmulsionPolymer). The particle size of 5s lipo battery xt60 SBR is usually 100-200nm, which is just in the elastic scattering range of visible light.
The shorter the wavelength of light, the stronger the scattering intensity. According to the wavelength distribution of visible light, blue and violet light scatters the most intensely. But violet light is absorbed by the atmosphere, and the human eye is not sensitive to violet light, so what we see with the naked eye is mainly blue light.
In addition, the 5s lipo battery xt60 graphite paste is black, which absorbs visible light and forms a good contrasting background color. So everyone will see that the blue light on the surface of the 5s lipo battery xt60 paste is obvious, while the blue light of a single SBR emulsion is not obvious.

3 It turns out that the blue floating of the 5s lipo battery xt60 is caused by the floating of the SBR, so why is the SBR floating?

In the 5s lipo battery xt60 slurry system, the surface of the graphite particles is hydrophobic, and the CMC molecule has both a hydrophobic part (main chain not modified by carboxyl groups) and a hydrophilic part (modified by carboxyl groups). The unmodified main chain of carboxyl groups is adsorbed on the surface of graphite particles, on the other hand, the hydrophilic carboxyl groups can make the graphite adsorbed with CMC suspended in water. The two properties of CMC combine to disperse graphite in water.

The carboxyl group modification on the surface of 5s lipo battery xt60 SBR particles makes SBR hydrophilic, so that it can be stably suspended in water. Due to its hydrophilic properties, 5s lipo battery xt60 SBR has poor adsorption to graphite, so SBR cannot effectively disperse graphite. In addition, the carboxyl groups on the surface of 5s lipo battery xt60 SBR are negatively charged, which repel each other with the carboxyl groups on the surface of CMC, which makes 5s lipo battery xt60 SBR and CMC dispersed graphite slurry poor compatibility, resulting in a small amount of SBR in the slurry static Float when set.

The compatibility between SBR and CMC-dispersed slurry system is poor, resulting in a small amount of SBR floating; SBR particles scatter visible light, in which the blue light with shorter wavelength has a large scattering intensity and is seen by the naked eye, so the slurry appears blue. The phenomenon.

4 What will cause the blue SBR caused by floating up? How to reduce floating?

Since the 5s lipo battery xt60 SBR floats up and causes blue, then this part of the SBR floating on the surface of the 5s lipo battery xt60 slurry may cause:
1. 5s lipo battery xt60 SBR uneven distribution in graphite coating
2. SBR on the surface of 5s lipo battery xt60 may cause sticky roll

5 So how to reduce the floating blue of 5s lipo battery xt60?

1. Minimize the standing time of the 5s lipo battery xt60 slurry, you can use low-speed stirring instead of standing.
2. Carry out the matching experiment between CMC and SBR and Graphite-CMC-SBR, and choose the appropriate combination of 5s lipo battery xt60 dispersion (CMC) and adhesive (SBR).
3. Through special modification of SBR, the functional groups on the surface of 5s lipo battery xt60 SBR can form a certain interaction with CMC, so that SBR can be anchored on CMC and reduce the floating of SBR.
The above is the whole content of SBR floating blue in lithium battery slurry brought by CNHL. I hope the above content will be helpful to you, so that you can have a further understanding of lithium battery. For more information about lithium battery, please refer to the following :
1200mah lipo battry 6s negative electrode material carding
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