New Energy

Lithium batteries are developing rapidly, and their applications have expanded from mobile phones and laptops to electric vehicles, energy storage systems and other fields. Lithium batteries have become an indispensable part of today’s mobile network world.

The technical difficulties in lithium-ion research and development are:

1) Uniform dispersion of electrode materials and conductive material particles; storage stability of slurry;
2) Wetting problems during high-speed and uniform coating of low surface energy substrates (such as PE, PP);
3) Foam control during production and construction.

In the production process of lithium batteries, in order to control the interface properties and provide a perfect current collector coating, good dispersion of particles is crucial to battery performance. In conductive slurries or electrode slurries, additives can improve the dispersion and stability of conductive carbon materials or active materials, and can evenly disperse the active particles in the electrode materials to prevent them from agglomerating during the preparation process, thereby achieving a more uniform production and preparation of electrode coatings. For example, wetting dispersants for stabilizing ceramic particles, and additive products that further improve the wettability of substrates.

1. Aqueous electrode slurry dispersant

Lithium-ion battery slurry mainly has two systems: aqueous and oily. The current mainstream slurry system is the positive electrode slurry PVDF/NMP oily system, accounting for up to 90%, and the remaining 10% is a water-soluble binder; the negative electrode slurry is a graphite/CMC/SBR aqueous system.
The ideal electrode slurry should have excellent rheological properties so that it can be stably and evenly coated on the surface of the current collector, while ensuring that the solid particles are evenly and stably dispersed, without spontaneous sedimentation and agglomeration, and can form an interconnected electrode microstructure.
Due to the existence of van der Waals forces or electrostatic attraction and gravity, the particles in the slurry are likely to agglomerate or settle. This greatly affects the dispersion uniformity of the slurry components and the overall anti-sedimentation stability of the slurry. Relatively strong hydrogen bonds and electrostatic forces are more likely to exist in aqueous slurries, which provides a strong condition for the agglomeration of particles.
Therefore, water-based slurries usually require the addition of wetting and dispersing agents, which can prevent particles from reaggregating through electrostatic repulsion and/or steric hindrance principles, making the conductive agent and active material more evenly dispersed, thereby ensuring the long-term stability of the slurry.

2. Additives for diaphragm coating slurry

The key to diaphragm coating is the development of ceramic slurry formula.
Ceramic slurry generally uses inorganic ultrafine powders (such as alumina and boehmite) to improve the safety and mechanical properties of the battery. However, there are a large number of unsaturated bonds on the surface of these inorganic powders, which have large surface energy and are prone to flocculation in the slurry, seriously affecting the placement stability of the ceramic slurry.
In order to prepare a ceramic coated diaphragm with good performance by coating ceramic on the diaphragm, it is generally necessary to add binders, dispersants, wetting agents, thickeners, leveling agents, defoamers, etc. to the slurry.

1) Wetting and dispersing agent

Reduces the viscosity of the slurry and increases the solid content; it can promote the uniform dispersion of ceramic particles in the medium to form a stable suspension.

2) Defoaming agent

The dispersion process of ceramic particles is often accompanied by the formation and stabilization of foam. Therefore, it is necessary to defoam the ceramic dispersion before coating to ensure that the coating is defect-free and pinholes will not be formed due to internal bubbles.

3) Substrate wetting agent

Improve the wettability of water-based ceramic slurry on hydrophobic substrates and the leveling of thin coatings, and can adjust the surface energy of the coating to improve the wettability of the electrolyte. It can increase the coating speed and optimize the adhesion of the coating.

4) Thickener

It is used to increase the viscosity of the slurry, change the physical properties of the slurry, prevent sagging during the coating process, and stabilize the slurry to improve the storage performance of the slurry.