In the production process of lithium-ion batteries, cathode dispersants play a crucial role. They are diverse in type, and different types, with their unique functional groups, influence the characteristics of the battery slurry and battery performance.
To improve the conductivity of lithium-ion battery cathode materials, nano-sizing and carbon coating are common methods; however, these easily lead to severe agglomeration problems, greatly interfering with slurry processing performance and the final battery performance. At this point, dispersants become a powerful tool for improving the dispersion of cathode slurry and optimizing battery performance. They can reduce interparticle attraction, improve slurry uniformity and stability, and thus enhance the battery's electrochemical performance.
From the perspective of functional groups, dispersants can be mainly classified into the following categories. Carboxylic acid dispersants are characterized by their carboxylic acid functional groups, which can form coordination bonds with metal ions, adsorb onto the surface of the cathode material, and generate electrostatic repulsion, effectively preventing particle agglomeration. Polyacrylic acid is a typical example; the carboxylic acid groups can participate in cation-related processes in the cathode. Sulfonic acid dispersants, with their strongly acidic sulfonic acid functional groups, readily dissociate in water, providing strong electrostatic repulsion and making them particularly suitable for aqueous slurry systems. Amine dispersants, with their amine functional groups, act as free radical scavengers, protecting cathode materials from free radical degradation; for example, polyethyleneimine containing -NH₂ groups can perform this function. Among nitrogen-containing heterocyclic dispersants, polyvinylpyrrolidone (PVP) commonly contains a pyrrolidone ring, achieving stable dispersion through steric hindrance and hydrogen bonding. Carboxymethyl cellulose (CMC), a water-soluble polymer, achieves dispersion by forming negatively charged colloidal particles in water through its carboxymethyl functional groups on its molecular chain.
In the preparation of lithium-ion battery cathode materials, the synergistic use of ultrasonic technology and dispersants is receiving increasing attention. Ultrasonic waves, through their cavitation and mechanical effects, can help dispersants function better, enhancing the dispersion effect on cathode materials. For example, during the preparation process, ultrasonic waves can promote more uniform adsorption of dispersants on the material surface, further reducing the possibility of particle agglomeration and improving slurry quality.
When selecting a dispersant, it is necessary to comprehensively consider factors such as the properties of the cathode material, the type of solvent, and the slurry preparation process. Different cathode materials are suitable for different dispersants. For example, lithium iron phosphate cathode slurries, due to their difficulty in dispersion, excessively high viscosity at high solids content, and poor coating effect, require specific dispersants, such as those containing polyphosphate esters, nitrogen-containing heterocyclic polyesters, and aromatic amide compounds. Polyphosphate esters anchor the incomplete carbon coating on the lithium iron phosphate surface with their phosphate groups, nitrogen-containing heterocyclic compounds anchor the carbon coating layer, and polyesters reduce interfacial energy to prevent agglomeration. In aromatic amide compounds, the amide groups act as anchors, and the aromatic groups provide steric hindrance, collectively achieving effective dispersion of lithium iron phosphate cathode materials.
Different types of cathode dispersants have their own advantages and disadvantages. In actual lithium battery production, it is necessary to carefully select a suitable dispersant based on the specific production process, slurry system, and battery performance requirements to ensure that the lithium battery possesses excellent performance and stable quality.
