What role does an ultrasonic defoamer play in degassing battery slurry?

What role does an ultrasonic defoamer play in degassing battery slurry?

During the degassing process, an ultrasonic defoamer uses the physical action of high-frequency ultrasound to efficiently remove tiny bubbles trapped in the slurry. This is crucial for battery performance and production stability. Its specific mechanism of action and core value are as follows:

1. Core Mechanism for Degassing Bubbles
Battery slurries (such as the positive and negative electrode slurries of lithium-ion batteries) are composed of a mixture of active materials, conductive agents, binders, and solvents. Air can easily enter during mixing and conveying, forming bubbles ranging from micrometers to millimeters in size. Ultrasonic defoamers degas bubbles by the following means:

Cavitation Effect: Bubble Destruction
When ultrasonic waves (typically with a frequency of 20kHz to 100kHz) propagate through the slurry, they induce high-frequency vibrations in the medium, generating periodic pressure fluctuations around the bubbles. During the negative pressure phase of the sound wave, the bubbles are stretched and expanded. During the positive pressure phase, the bubbles are severely compressed and instantly rupture (cavitation effect), releasing the gas trapped within the bubbles to the slurry surface and ultimately escaping the system.

For tiny bubbles (especially those with a diameter of less than 50μm, which are difficult to remove with traditional vacuum degassing), the high-frequency vibrations of ultrasound can directly break the surface tension of the bubbles, causing them to coalesce into larger bubbles that are easier to float up and expel.

Vibration Promotes Bubble Migration
The mechanical vibrations of ultrasound create microscopic convection throughout the slurry, driving bubbles to the surface and accelerating their upward movement, preventing them from becoming trapped in the slurry or trapped between solid particles.

II. Critical Role in Battery Slurry

Improving Electrode Coating Quality
Residual bubbles in the slurry can cause pinholes, pits, and uneven coating on the electrode surface during the coating process, affecting electrode consistency. Ultrasonic degassing results in a more uniform and dense coating, reducing the risk of capacity fade or thermal runaway caused by localized current concentration during charge and discharge.

Ensuring Electrode Mechanical Properties
Bubbles can weaken the bond between the electrode material and the current collector (such as copper or aluminum foil), leading to powder loss and cracking during rolling and slitting. After degassing, the binder in the slurry is more evenly distributed, enhancing the adhesion between the active material and the current collector and improving the mechanical strength of the electrode.

Optimizing Battery Electrochemical Performance

Bubbles can obstruct the migration of lithium ions in the electrode, increasing the battery's internal resistance and reducing charge and discharge efficiency.

Residual bubbles can damage the electrode structure due to volume changes during cycling, shortening the battery's cycle life. Ultrasonic degassing can reduce this risk and improve the battery's capacity stability and rate performance.

Adapting to the Degassing Needs of High-Viscosity Slurries
Battery slurries (especially high-nickel cathode slurries and silicon-based anode slurries) typically have high viscosities, making traditional vacuum degassing inefficient (bubbles struggle to break through the viscous medium and float upward). The cavitation effect of ultrasound can directly act within the slurry, effectively breaking bubbles even in high-viscosity systems and compensating for the shortcomings of vacuum degassing.

III. Synergistic Advantages with Traditional Degassing Methods
In battery slurry production, ultrasonic degassing machines are often used in conjunction with vacuum degassing, mechanical agitation degassing, and other methods to form a "combined degassing process":

The vacuum environment reduces the pressure differential between the inside and outside of the bubbles, promoting their expansion;
The ultrasonic wave specifically destroys tiny bubbles and those encapsulated by particles. Together, these two methods can reduce the gas content in the slurry to below 0.1%, meeting the production requirements of high-precision batteries (such as power batteries and solid-state batteries).

Summary
Ultrasonic degassing machines use high-frequency vibration and cavitation effects to precisely break down tiny bubbles in battery slurry. Their core role is to improve slurry uniformity, ensure electrode quality, and optimize battery electrochemical performance. They are key equipment for ensuring product consistency and reliability in battery production, and are particularly suitable for degassing high-viscosity, demanding new battery slurries.