What Is The Role of Ultrasonic Homogenization in Battery Slurry?

During battery manufacturing, the quality of the slurry directly impacts battery performance, consistency, and safety. Ultrasonic homogenization, as a highly efficient dispersion and refinement technology, plays a key role in battery slurry processing. Its core approach is to disperse, refine, and mix the solid particles in the slurry through the cavitation, shear, and vibration effects generated by high-frequency ultrasonic vibrations (typically above 20kHz).

1. Efficiently Disperse Solid Particles and Prevent Agglomeration

Battery slurries typically consist of active materials (such as lithium iron phosphate and ternary materials for the positive electrode, and graphite and silicon-based materials for the negative electrode), conductive agents (carbon black, carbon nanotubes, and graphene), binders (PVDF and SBR), and solvents (NMP and deionized water). These solid particles, especially nanoscale conductive agents and active materials with high specific surface area, are prone to agglomeration due to van der Waals forces and electrostatic interactions, forming either "hard" or "soft" aggregates.

Ultrasonic homogenization utilizes cavitation (microbubbles in a liquid vibrate and implode under ultrasonic waves, generating localized high temperatures, high pressures, and microjets) and shear forces (fluid shear forces generated by high-frequency vibrations) to effectively break down interparticle bonds, dispersing aggregates into smaller single particles or small aggregates, ensuring uniform suspension of solid particles in the solvent.

•Benefit: Prevents uneven slurry density caused by agglomeration, reduces "particle accumulation" or "voids" on the electrode surface during subsequent coating, and ensures uniform electrode thickness and consistent electrochemical performance.

2. Refining Particle Size and Improving Reactivity

For active material particles, ultrasonic homogenization can further refine the particle size through high-frequency mechanical action, reducing the average particle size and particle size distribution. For example, in silicon-based anode slurries, silicon particles are prone to pulverization due to volume expansion. Refining silicon particles can reduce expansion stress and increase the contact area with the electrolyte.

•Mechanism of Action: The localized impact and shear forces generated by cavitation can "micro-crush" the particles, which, combined with fluid dynamics, achieves a more uniform particle size.

•Benefit: Particle refinement increases the specific surface area of the active material, enhancing the lithium ion diffusion rate and electrode reaction kinetics, improving the battery's rate charge and discharge capability and cycle life.

3. Enhance Component Compatibility and Optimize Slurry Stability

The compatibility of the components (active material, conductive agent, binder) in battery slurry directly affects slurry stability (e.g., sedimentation and delamination). Ultrasonic homogenization promotes interfacial contact and interaction between different components. For example:

•Uniformly coats the conductive agent (e.g., carbon black) on the active material surface, forming a continuous conductive network and reducing the phenomenon of "conductive islands";

•Promotes the adsorption and diffusion of binder molecules on the particle surface, strengthening interparticle adhesion and preventing slurry sedimentation during storage or coating.

•Benefit: The optimized slurry has improved stability, extending storage time and reducing secondary stirring costs before coating, while maintaining the conductive pathway and structural integrity of the electrode.