Negative electrode material sticking is a significant issue in lithium battery manufacturing. It can lead to wasted time, reduced efficiency, and even unusable electrodes, resulting in substantial economic losses. To address this problem, researchers have identified several key factors contributing to sticking:
1. Roller Surface Contamination:
- Protective coatings on roller press surfaces, if not thoroughly cleaned, can contaminate the negative electrode sheet during rolling, causing sticking.
- Cross-contamination between positive and negative electrodes can occur if they share equipment, such as roller presses or coating machines.
2. Insufficient Drying of Negative Electrodes:
- Incomplete drying during the coating process can leave moisture in the negative electrode sheet, weakening the binder’s bonding ability and increasing the risk of sticking.
- A common method to assess drying is by weighing the electrode before and after a drying period in an oven.
3. High Oven Temperature:
- Excessive baking temperatures can cause the solvent to evaporate too quickly, leading to adhesive concentration gradients and increased adhesion to the electrode surface.
- This can result in the electrode sticking to the roller during rolling.
4. Incorrect Binder Ratio:
- Using too little binder can lead to uneven dispersion of graphite and carbon black, affecting bonding between particles and the foil.
- This can increase the likelihood of sticking during rolling.
5. SBR Flocculation:
- If SBR (styrene butadiene rubber) floats blue during the pulping process, it can cause uneven distribution in the coated electrode, reducing adhesion and increasing sticking.
6. Negative Electrode Material Type:
- Artificial graphite particles, compared to natural graphite, have a rougher surface and are more likely to form agglomerates.
- These agglomerates can lead to uneven pressure distribution during rolling, causing point-like sticking.
7. Batching Process:
- Long-term high-speed stirring during the wet pulping process can break the CMC (carboxymethyl cellulose) molecular chain, hindering dispersion and increasing the risk of sticking.
8. CMC Quality:
- The quality of CMC can affect the pole piece microstructure and contribute to sticking. Insoluble matter in CMC can form agglomerates, causing blockages, scratches, and sticking.
Addressing negative electrode sticking requires a comprehensive approach that considers these various factors. By implementing appropriate measures to prevent contamination, ensure proper drying, optimize binder ratios, and address the challenges associated with negative electrode materials and the manufacturing process, manufacturers can significantly reduce sticking issues and improve overall lithium battery production efficiency.