Why Do Lithium-ion Battery Electrodes Crack?

Cracking of lithium-ion battery electrodes has always been a challenging problem in the industry. This article analyzes the core causes of electrode cracking from two perspectives: stress and gradient stress, focusing on slurry characteristics, coating processes, and current collector issues.

To address these problems, several feasible improvement solutions are proposed—optimizing slurry formulation, precisely controlling the drying curve, and improving current collector processing—providing practical references for improving electrode quality and stability, and making battery production more reliable.

Electrodes are a crucial component of lithium-ion batteries, directly affecting battery performance and safety. However, cracking occurs frequently during electrode preparation, posing a challenge to battery development. In-depth research into the causes and mechanisms of electrode cracking and proposing effective improvement measures is particularly important.

I. Core Mechanisms of Cracking

1. Stress Principle

Solvent Evaporation and Shrinkage Stress: During electrode preparation, the solvent content in the slurry is high. As drying progresses, the solvent gradually evaporates, causing the slurry volume to shrink and generate stress. If this shrinkage stress exceeds the adhesive force of the binder, the electrode will crack. Therefore, the binder content is crucial; electrodes lacking binder are more prone to cracking after drying.

Microscopic Particle Spacing Changes: At the microscopic level, electrodes are composed of many particles. As the solvent evaporates, the particle spacing changes, leading to uneven interaction forces. This unevenness causes localized stress concentration, thus triggering cracking.

2. Gradient Stress Influence

The surface and interior of the electrode dry at different rates; the surface dries faster, while the interior dries relatively slowly. This difference creates a stress gradient, and the interaction between the surface and interior increases the risk of cracking.

II. Three Major Causes

1. Slurry Factors

Insufficient Binder: Insufficient binder content weakens the bonding force between particles, increasing the risk of cracking.

2. Abnormal Viscosity

High Viscosity: If the slurry viscosity is too high, uneven coating and uneven shrinkage during drying can easily lead to cracking.

Low Viscosity: Too low viscosity can cause particle agglomeration, resulting in different shrinkage behaviors during drying and increasing internal stress.

Particle Distribution: Uneven particle distribution can lead to the aggregation of large particles, causing localized stress concentration and cracking.

3. Coating Process

Coating Speed: Excessive speed can result in insufficient solvent evaporation, increased internal pressure, and increased susceptibility to cracking.

Temperature Control: Improper drying temperature and significant differences in evaporation rates between the surface and interior increase the risk of cracking.

Thickness Fluctuation: Uneven coating thickness causes varying degrees of shrinkage in different areas, increasing stress concentration.

4. Current Collector Issues

Surface Roughness:

Excessively Smooth: An overly smooth surface lacks adhesion and is prone to peeling and cracking.

Excessively Rough: An excessively rough surface leads to uneven coating and increases the risk of cracking.

Cleanliness: Impurities can interfere with slurry adhesion, causing stress concentration and cracking.

III. Improvement Directions

1. Optimize Slurry Formulation

Binder Control: Precisely control the binder content to ensure electrode structure stability and reduce the risk of cracking.

Viscosity Adjustment: Appropriately adjust the slurry viscosity to achieve optimal flowability and uniformity.

2. Precise Control of the Drying Process

Temperature Gradient: Appropriately setting the temperature gradient slows down the surface solvent evaporation rate and reduces stress gradient.

Rate Control: Dynamically adjusting the drying rate ensures uniform solvent evaporation both internally and on the surface.

3. Improved Current Collector Processing

Surface Treatment: Improving the surface roughness of the current collector enhances slurry adhesion and prevents cracking.

Cleanliness Standards: Establishing strict cleanliness standards ensures the current collector surface is free of impurities, reducing the risk of cracking.

IV. Conclusion

The cracking problem of lithium-ion battery electrodes is influenced by various factors, including slurry formulation, coating process, and current collector characteristics.

ACEY-HFC250 film coating machine is widely employed in the study of various high‑temperature coating films, including ceramic films, crystalline layers, battery material coatings, and specialized nano‑films. They are designed to align with future technological advances in high‑temperature film formation.

By optimizing the slurry, precisely controlling the drying process, and improving the current collector processing technology, we can effectively improve the quality and stability of electrodes, promoting the development of lithium-ion battery technology. We hope these studies and suggestions will provide assistance to the production and application in related industries!