15 Particle Characterisation SurPASS 3: Advanced surface zeta potential measurement


The SurPASS 3 is an advanced electrokinetic analyser designed for measuring the surface zeta potential and investigating the adsorption kinetics of adsorbates on solid materials using the streaming potential method. It provides detailed insight into the electrochemical properties of solid-liquid interfaces, enabling the determination of the isoelectric point (IEP) and surface charge behaviour as a function of pH, ionic strength, and sample chemical composition. The instrument supports a variety of sample types, including fl at fi lms, fi bres, membranes, rigid fl at surfaces, and pressed powders, making it a versatile tool for optimising material interfaces in electrochemical systems, membrane development, and biomolecular interaction studies.


Figure 4: SurPASS 3: Surface charge & zeta potential electrokinetic analyser for solid surface analysis.


Complementary techniques for advanced battery material design


The development of advanced batteries, such as lithium-ion and solid-state types, relies heavily on precisely engineering powders and slurries used in electrodes, separators, and electrolytes. Understanding the size, shape, and distribution of particles in these materials is crucial for optimising performance parameters such as energy density, charge rate, and cycle life. Four main analytical techniques – dynamic image analysis, laser diffraction, dynamic/ electrophoretic light scattering, and streaming potential – play a key role in this process, each offering unique and complementary insights.


Dry mix of lithium-ion battery electrode materials


Polytetrafl uoroethylene (PTFE), which is used for dry coating of electrodes, undergoes fi brillation, a mechanical transformation in which the polymer particles are stretched into fi brous networks under shear and compressive forces. Initially present as compact, spherical particles, PTFE forms elongated fi brils that entangle with graphite and carbon black, enhancing interparticle binding. This transformation signifi cantly alters particle morphology and increases apparent particle size. The Litesizer DIA measurements clearly capture this effect: pre-mix samples at 1%, 3%, and 5% PTFE show narrow, monomodal particle size distributions, characteristic of unprocessed powders. After 10 minutes of mixing, the size distribution broadens and becomes multimodal, indicating the formation of irregular, fi brous structures and the aggregation of conductive additives. These effects are more pronounced at higher PTFE concentrations due to more extensive fi bril formation. Monitoring these changes is critical for ensuring the mechanical integrity and performance of dry-processed electrodes, and dynamic image analysis provides a valuable tool for real-time process control and quality assurance.


Graphite spheronization


Unlike conventional graphite fl akes, which are irregular and plate-like, spheronized graphite consists of rounded, compact particles with a lower surface area and enhanced fl owability. This transformation increases tap density, improves electrical contact, and promotes uniform solid electrolyte interface formation, resulting in higher capacity, better performance, and a longer cycle life. The process typically involves high-energy milling and classifi cation to achieve a narrow particle size distribution. Dynamic image analysis with the Litesizer DIA enables precise comparison of particle size and shape between conventional and spheronized graphite.


Quality control of electrode powders


Laser diffraction (LD) is widely used in process control to measure particle size distribution in materials such as electrode powders and solid-state electrolytes. Its ability to handle broad and multimodal size ranges makes it ideal for ensuring uniform sintering and ionic conductivity. LD is used as well for quality control in battery manufacturing because it provides rapid, accurate, and repeatable measurement of particle size distribution, which is critical for the performance and consistency of battery materials.


The particle size distribution of three LiCoO₂ (LCO) cathode samples was measured using laser diffraction with the Litesizer DIF. This technique provides detailed insight into particle size parameters, which are critical for high-performance battery applications. Tight control over distribution width ensures a high degree of homogeneity, supporting optimal electrochemical performance, improved packing density, and enhanced battery safety.


Figure 5: Projected area equivalent diameter (xA) before and after mixing for different PTFE contents.


Carbon black size and stability


Dynamic light scattering (DLS) measures submicron particle sizes and zeta potential in suspensions. It is essential for analysing nanomaterial-based electrolytes and coatings, where nanoscale control infl uences ion mobility and system stability in advanced batteries.


Carbon black particle size is critical to battery electrode performance. Smaller particles enhance electronic conductivity by forming effi cient conductive networks and improving dispersion uniformity. However, overly fi ne particles can increase slurry viscosity, hinder ion transport, and promote side reactions due to a high surface area. Optimising particle size is essential to balancing conductivity, ionic access, and processability in battery systems. The Litesizer DLS series enables effective characterisation of carbon black suspensions, providing valuable insights for formulation optimisation. Figure 8 shows the particle size distribution of three different carbon black powders measured with the Litesizer DLS.


Zeta potential quantifi es the electrical potential at the interface between a particle or a surface and the surrounding fl uid. In battery systems, zeta potential helps assess the stability of suspensions and slurries. A higher absolute zeta potential typically indicates stronger repulsive forces, reducing the risk of agglomeration and sedimentation – critical for consistent coating quality and reliable performance in electrodes and electrolytes.


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