Impact of A and B Side Coating Misalignment on Lithium Battery Performance

In lithium battery manufacturing, the often-overlooked A/B-side coating misalignment issue during the coating process significantly affects battery capacity, safety, and cycle life. Misalignment refers to inconsistencies in the positional alignment or thickness distribution of coatings on the front and back sides of electrodes, which can lead to risks such as localized lithium plating and mechanical damage to the electrodes.

This article analyzes the root causes of misalignment from perspectives including equipment precision, process parameter settings, and material properties, while proposing targeted optimization strategies to help enterprises enhance product consistency and stability.

Ⅰ. Causes of A/B-Side Misalignment

1. Equipment Factors

Insufficient roll system assembly accuracy: Horizontal or coaxial deviations during the installation of backing rolls and coating rolls may cause positional shifts.

Coating head positioning errors: Low-resolution encoders/grating rulers or sensor feedback drift result in deviations between actual and preset coating positions.

Tension fluctuations: Unstable unwinding/winding tension causes substrate stretching or wrinkling, reducing coating precision.

2. Substrate (Foil) Issues

Non-uniform ductility: Inconsistent foil plasticity complicates gap control during coating.

Poor surface quality: Residual oxide layers weaken slurry adhesion, leading to partial coating or misalignment.

3. Slurry Properties

High viscosity impairing leveling: Poor slurry flowability causes uneven accumulation.

Large surface tension differences: Uneven edge shrinkage due to tension disparities between front/back coatings.

4. Process Settings

Inconsistent coating speeds: Speed differences between sides disrupt slurry spreading.

Drying condition variations: Temperature differences induce uneven thermal shrinkage, causing misalignment.

Ⅱ. Proposed Solutions

1. Equipment Precision Optimization

Regularly inspect roll coaxiality/flatness to control installation errors.

Upgrade coating head positioning components (e.g., high-resolution encoders) to limit deviations within ±0.1 mm.

Implement closed-loop tension control (e.g., PID adjustment) to maintain tension fluctuations below ±3%.

2. Substrate Consistency Control

Select high-uniformity copper/aluminum foils with stable elongation properties.

Adopt advanced surface treatments (e.g., low-temperature plasma cleaning) to enhance slurry adhesion uniformity.

3. Slurry Performance Adjustment

Optimize viscosity (anode: 10–12 Pa·s; cathode: 4–5 Pa·s) for better leveling.

Add surfactants (e.g., PVP, SDS) to balance surface tension between sides.

4. Process Parameter Refinement

Maintain identical coating speeds for both sides (error <0.5 m/min).

Apply segmented temperature control: Low-temperature pre-drying for stress relief and high-temperature curing, with overall temperature differences <5°C.

Ⅲ. Diagnosis and Monitoring Mechanisms

1. Equipment Diagnosis

Use laser interferometers to verify roll parallelism (error <0.02 mm/m).

Inspect motor/sensor signal stability to prevent drift exceeding 0.5% of the range.

2. Substrate Evaluation

Test elongation at break (deviation <±5%).

Analyze surface microstructure/oxide layers via SEM (thickness <50 nm).

3. Slurry Testing

Measure viscosity and thixotropy via rheometers (thixotropic area difference <5%).

Ensure surface tension difference <2 mN/m using tensiometers.

4. On-Line Process Control

Monitor coating thickness with laser sensors (CV <1%).

Post-drying X-ray inspection for coating density uniformity (lateral deviation <2%).

Conclusion

Through precise equipment calibration, material screening, slurry optimization, and systematic process management, A/B-side misalignment can be controlled within ≤0.5 mm. This effectively enhances battery consistency, safety, and cycle life.

At TOB NEW ENERGY, we are committed to being your strategic partner in advancing energy storage technologies. We empower next-generation lithium battery production through precision battery coating systems, intelligent battery production lines, and high-performance materials.  Our offerings extend to cutting-edge battery manufacturing equipment and battery tester, ensuring seamless integration across every stage of battery production. With a focus on quality, sustainability, and collaborative innovation, we deliver solutions that adapt to evolving industry demands. Whether you’re optimizing existing designs or pioneering next-generation batteries, our team is here to support your goals with technical expertise and responsive service.