Lithium-ion double-layer coating technology is a technology different from the conventional single-layer coating process. It optimizes electrode performance by coating slurries with different characteristics in layers.
The core of double-layer coating is to design the coating slurry formula in layers, and improve the performance of the battery cell by adjusting the formula ratio and material ratio. The current double-layer coating technology sets the upper and lower layers with the same density to achieve normal capacity.
1.If you want to enhance the adhesion of the bottom layer, you can increase the content of the adhesive in the lower layer and reduce the content of the adhesive in the upper layer to reduce polarization.
2.In order to increase conductivity and improve fast charging performance, double-layer coating technology can also be used for optimization. Active materials of different particle sizes are layered and coated. The large particle size active material layer can form a relatively large ion transmission channel, which is convenient for the rapid diffusion of lithium ions; the small particle size active material layer can increase the contact area with the current collector, improve the electron conduction efficiency, thereby reducing the lithium ion diffusion resistance and speeding up the charging speed.
At the same time, the conductive agent layered structure is reasonably designed, and more conductive agents are placed in the lower layer close to the current collector. In this way, more conductive paths can be formed, which reduces the transmission resistance of electrons in the electrode. Electrons can be transmitted more quickly between the battery electrode material and the current collector, providing a better electron supply for the insertion and extraction of lithium ions, thereby improving the fast charging performance of the battery.
3.In order to improve the energy density, the upper layer can be coated with high porosity, and high compaction material can be used next time. High porosity is conducive to the rapid penetration of electrolyte, and high compaction is conducive to improving energy density.
What equipment and methods are used to achieve double-layer coating technology?
There are two main ways to implement double-layer coating technology for lithium batteries.
- Use a double-layer die coating device;
- use “comma” roller transfer coating or slit extrusion coating combined with a dual feeding system.
For example, double-layer die coating:
Double-layer die coating includes a first die, a first gasket, a second die and a second gasket. The first gasket and the second gasket are installed in the first die and the second die respectively, which play a role in controlling the coating area and shape.
Coating process:
The second die head stops coating, the first feeding device is driven by the servo motor to open the first feeding valve, and the slurry is sent to the first die head through the feeding cylinder assembly. The first die head coats the electrode, and the coating flows out from the first gasket coating area of the first gasket, and a complete coating area is obtained on the electrode. The first die head stops coating, and the second feeding device is driven by the servo motor to open the second feeding valve and send the slurry to the second die head. The second die head coats the pole piece. Under the action of the extrusion die head, the coating flows out from the second gasket coating area containing multiple second gasket blank areas, and alternating pole ear coating areas and pole ear blank areas are obtained on the electrode.
