From nanoparticles to macroscopic surfaces: The complete characterisation portfolio for particle size, shape, and zeta potential

From nanometre-sized particles to larger surfaces, the physical and electrostatic properties of materials are key to understanding how they behave in real-world situations.  Among these properties, the size, shape, and zeta potential of particles are especially important. These factors affect how well particles work, how stable they are, and how they interact with each other and their environment. For example, the size and shape of a particle can determine its surface area and reactivity. Zeta potential, which reflects the surface charge, helps explain the forces that keep particles apart or bring them together. A high absolute zeta potential value usually means particles repel each other strongly, which helps prevent them from clumping together and keeps the system stable. Together, these characteristics are essential to understanding and controlling particle performance in fields such as nanotechnology, pharmaceuticals, and materials science.

Different characterisation techniques for a broad range of samples

Dynamic image analysis: Understanding particle size and shape
Dynamic image analysis is an advanced technique to measure particle size and shape simultaneously. Particles are dispersed and recorded in motion using a high-speed camera. Specialised software then analyses these images to extract precise measurements of size and shape. By evaluating thousands of particles, this method provides detailed statistics about their physical features, making it ideal for applications where particle shape matters as much as size, like quality control or material development.
The Litesizer DIA series uses dynamic image analysis to measure particles as small as 0.5 µm and as large as 16,000 µm, covering everything from fine powders to coarse granules. Its standout feature is its three interchangeable dispersion units:
• Liquid Flow: For analysing particles suspended in fluids.
• Dry Jet: For free-flowing powders.
• Free Fall: For fragile or sticky materials.
This flexibility ensures optimal sample dispersion for both wet and dry samples.
Figure 1: Litesizer DIA series with its three dispersion units (Liquid Flow, Dry Jet, and Free Fall).
Laser diffraction: Fast and reliable particle size measurement
Laser diffraction is a popular and reliable method for measuring the size distribution of particles in a sample. With this technique, a laser beam shines through the sample, and the particles scatter the light at different angles depending on their size. Larger particles scatter light at smaller angles, while smaller particles scatter at wider angles. By analysing the pattern and intensity of this scattered light, the particle size distribution can be accurately determined.
The Litesizer DIF 500 can measure a wide range of particle sizes, from as small as 
10 nanometres up to 3.5 millimetres. It uses advanced optics with powerful 10 mW and 25 mW lasers, and can detect scattered light over an exceptionally wide range of angles – from 0.01 ° to 170 °. This allows for precise measurements across many different types of samples. To ensure stable and accurate results, the system includes shock-absorbing parts that reduce the impact of vibrations from the environment. The sensitive optical components are also protected inside strong metal housing, which keeps out dust and shields the system from direct bumps or shakes. These design features help maintain the accuracy of measurements and extend the life of the instrument.
Figure 2: Litesizer DIF 500 with the Liquid Flow Dispersion Unit.
DLS and ELS for nanoparticle analysis and colloidal stability
Dynamic light scattering (DLS) and electrophoretic light scattering (ELS) are well-established techniques for characterising particles in suspension. DLS measures particle size by tracking fluctuations in the intensity of scattered light, which occur as particles move randomly (Brownian motion). ELS, on the other hand, measures the frequency shifts of scattered light from particles in an electric field to calculate zeta potential, a key indicator of colloidal stability.
The Litesizer DLS series combines DLS for particle size, advanced cmPALS-based ELS for zeta potential, and static light scattering (SLS) for molecular mass determination. Additional measurement modes, such as transmittance, multi-angle particle sizing, refractive index, and particle concentration measurements further extend its capabilities. The Litesizer DLS supports a wide range of applications in pharmaceuticals, nanotechnology, polymer science, and environmental research.
Figure 3: Litesizer DLS particle analyser with automatic angle selection.
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 flat films, fibres, membranes, rigid flat 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
Polytetrafluoroethylene (PTFE), which is used for dry coating of electrodes, undergoes fibrillation, a mechanical transformation in which the polymer particles are stretched into fibrous networks under shear and compressive forces. Initially present as compact, spherical particles, PTFE forms elongated fibrils that entangle with graphite and carbon black, enhancing interparticle binding. This transformation significantly 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, fibrous structures and the aggregation of conductive additives. These effects are more pronounced at higher PTFE concentrations due to more extensive fibril 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 flakes, which are irregular and plate-like, spheronized graphite consists of rounded, compact particles with a lower surface area and enhanced flowability. 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 classification 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.
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 influences 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 efficient conductive networks and improving dispersion uniformity. However, overly fine 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 quantifies the electrical potential at the interface between a particle or a surface and the surrounding fluid. 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.
Carbon-based cathodic additives, such as carbon black and graphite, exhibit consistently negative zeta potentials across the entire pH range investigated. In contrast, lithium cobalt oxide (LCO) particles display a positive zeta potential at pH values below 4. At pH levels between 6 and 7, all components acquire sufficiently negative zeta potentials, promoting electrostatic repulsion and thereby minimising the likelihood of particle aggregation within the electrode slurry.

Wettability of separator membranes
Separator membranes in lithium-ion batteries must electrically insulate the electrodes while allowing lithium-ion transport. Commercial separators are typically made from microporous polyolefins like polyethylene (PE) and polypropylene (PP), which provide chemical stability and electrolyte uptake but suffer from limited thermal stability and poor wettability. To address these issues, ceramic-coated separators were developed by applying thin layers of inorganic oxides (e.g., Al₂O₃ or SiO₂) onto polyolefin substrates. These coatings enhance mechanical strength, thermal resistance, and electrolyte wettability – critical for high-power applications such as electric vehicles. Ceramic coatings also modify surface chemistry, introducing hydrophilic and often-charged groups that improve electrolyte interaction and ionic mobility. Zeta potential measurements using the SurPASS 3 instrument reveal that ceramic-coated separators exhibit lower zeta potential magnitude (less negative surface charge) across a wide pH range, indicating improved wettability and lower interfacial resistance compared to uncoated PP. These results underscore the role of surface charge characterisation in optimising separator performance.
Summary
The characterisation of particle size, shape, and zeta potential is especially crucial when dealing with dry electrode materials. In the absence of solvents, which typically aid in particle dispersion and processing, the physical and electrochemical properties of the particles themselves must be tightly regulated. For dry-coated electrodes, parameters such as particle morphology, size distribution, and surface charge become fundamental in influencing key performance factors, including mechanical stability, electrical conductivity, and overall electrode packing density.
In the broader context of battery manufacturing, these characterisation techniques highlight the value of employing different characterisation methods. Each method contributes unique insights, which, when combined, enable a more thorough understanding of critical steps throughout the production process. Together, these techniques form a comprehensive and complementary toolkit, essential for ensuring quality and performance in advanced electrode manufacturing:
•    Dynamic image analysis (DIA) provides detailed information on particle size and particle shape.
•     Laser diffraction (LD) enables robust bulk particle size measurement for quality control.
•     Dynamic light scattering (DLS) measures particle size and stability of suspension in the  nanometre and micrometre range.
•     Zeta potential assesses the colloidal stability of particle suspensions and evaluates the  charge characteristics of membranes and solid surfaces.
When applied in combination, these methods support more precise material design and process optimisation. This integrated approach is especially valuable in dry electrode manufacturing, where tightly controlled material parameters are essential for producing safer, higher-performance, and longer-lasting energy storage systems.