How to Measure Surface Tension for High-Performance Battery Manufacturing

Surface tension measurement in batteries refers to analysing how liquids such as electrode slurries and electrolytes interact with solid surfaces like electrodes, separators, and casings. It’s a critical factor in manufacturing and R&D because it governs wetting, coating uniformity, adhesion, and material compatibility.

In this guide, we will share the essential methods for measuring surface tension and delve into its crucial role in advancing battery manufacturing and performance.

This guide will help you:

• Understand why surface tension is important for battery manufacturing and research
  
• Learn the main methods for measuring surface tension in liquids and solids
  
• Match each method to the right KRÜSS instrument for your application
  
• See how surface tension measurement fits into battery R&D and quality control workflows

By the end, you’ll know which technique to use, when to use it, and how it supports consistent, reliable battery production.

What is Surface Tension?

Surface tension, interfacial tension, and surface free energy (SFE) are closely related properties in surface and colloid science. Surface tension is the cohesive energy at a liquid’s interface, while interfacial tension describes the same phenomenon between two immiscible liquids or a liquid and a solid.

SFE refers to the energy stored at a solid’s surface from disrupted molecular bonds, high-SFE materials like metals, glass, and ceramics wet easily, whereas low-SFE materials such as PTFE or polypropylene resist wetting and are harder to coat or bond.

The Critical Role of Surface Tension in Battery Manufacturing & Research

Surface tension plays a critical role in battery manufacturing as it has a direct impact on the quality of the coating and material wetting which affect the overall cell performance.

Electrode Slurry and Coating: Slurries of active materials, binders, and solvents must wet copper or aluminium foils evenly. If surface tension is too high or too low, coatings can bead or form uneven layers, leading to defects and performance loss.

Electrolyte Wetting: Electrolytes must fully penetrate porous electrodes and separators for efficient ion transport. Poor wetting from a surface tension mismatch can cause dry spots, reduced capacity, and safety risks. Lower surface tension generally speeds wetting.

Performance and Safety: Surface tension impacts slurry dispersion stability, affecting how well nanoparticles and additives are distributed. Good control improves energy density, safety, and reliability.

Aqueous Processing: Moving to water-based slurries instead of toxic solvents like NMP makes surface tension control even more critical.

In short, surface tension is fundamental for achieving reliable wetting, uniform coatings, strong adhesion, and consistent material distribution, essential for high-performance, long-lasting batteries.

Key Methods for Surface Tension Measurement

Surface tension is typically measured by observing how a liquid behaves at its interface (usually with air) using methods based on mechanical force or optical analysis.

Force Tensiometry

• Du Noüy Ring Method: A platinum ring is submerged in the liquid and slowly pulled upward. The force needed to detach the ring is proportional to the surface tension.
• Wilhelmy Plate Method: A thin, flat plate (usually platinum) is partially immersed, and the force acting on the plate is used to calculate surface tension.

Example instrument: The KRÜSS Tensiio Force Tensiometer provides automated, precise, and reproducible measurements for liquids and solids. With an optional high-resolution camera, it can record the contact area at the liquid surface, enabling simultaneous optical drop analysis and adhesion measurement.

Optical Tensiometry:

• Pendant Drop: A liquid drop is suspended from a needle and its curvature is analysed via the Young–Laplace equation.

• Sessile Drop / Contact Angle: Measures the angle where a liquid, solid, and gas meet, providing insight into wettability, adhesion, and surface free energy (SFE). This is commonly performed using a Goniometer/tensiometer method, which allows precise measurement of contact angles and droplet shapes for both research and quality control applications.

Example instrument: The KRÜSS DSA100 Drop Shape Analyser measures contact angle, surface tension, and interfacial tension with high-speed cameras and advanced software. It’s ideal for optimising electrode and separator wetting, checking electrolyte compatibility, ensuring slurry coating homogeneity, and supporting QC.

Learn more about the Goniometer/tensiometer method.

Bubble Pressure Tensiometry:

A bubble forms at the end of a submerged capillary, and the pressure needed to form it reflects the surface tension at that moment. This method measures dynamic surface tension over milliseconds to seconds, valuable for electrolytes or slurries containing surfactants, dispersants, or binders.

Example instrument: The KRÜSS BPT Mobile Bubble Pressure Tensiometer captures surface tension changes in real time for rapidly changing formulations. The pressure needed to form each bubble reflects the surface tension at that exact moment. This is especially useful for formulations that change over milliseconds to seconds, such as those containing surfactants, dispersants, or binders.

Spinning Drop Tensiometer

The Spinning Drop Tensiometer is specialised for ultra-low interfacial tension, commonly used in emulsion studies. It is increasingly relevant to advanced battery systems with ionic liquids, complex liquid–liquid interfaces, and multiphase electrolytes.

Dynamic Foam Analyser

Measures foam formation, stability, and drainage—important in slurry preparation, coating, and electrolyte mixing, where unwanted foaming can cause defects.

Example instrument: The KRÜSS DFA100 evaluates foaming behaviour and anti-foaming strategies for more consistent manufacturing.

Portable contact angle instrument

Hand-held devices like the KRÜSS Mobile Surface Analyser (MSA) provide fast, on-site wettability and cleanliness checks—ideal for QC, surface preparation, and coating processes in battery production.

Matching Measurement Methods to Specific Instruments

Choosing the right analytical technology depends on the type of surface or interfacial measurement you need. Whether you’re studying wetting behaviour, optimising formulations, or characterising material interfaces, KRÜSS offers a range of precise instruments tailored to specific applications.

The table below matches measurement methods to the most appropriate KRÜSS tensiometers, helping you select the best system for your needs.

Integrating Surface Tension Measurement into Battery R&D and QC

From lithium-ion to solid-state and sodium-ion, battery technology is advancing rapidly, but one principle applies to them all: consistent interaction between materials drives performance. Achieving optimal wettability of electrodes and separators by the electrolyte boosts capacity, safety, and lifespan.

By integrating surface tension measurement into both R&D and QC, manufacturers can prevent costly defects and ensure product consistency from the lab to the production line. Learn more about integrating analytical techniques into battery recycling.

• Holistic approach: Combine force tensiometry for electrolyte behaviour with contact angle measurements for electrode surfaces to gain a complete interfacial profile.
• From lab to line: Apply these measurements to verify slurry stability, electrolyte compatibility, and coating quality at every stage.
• Future-ready automation: ATA Scientific supplies KRÜSS instruments with modular accessories and high-throughput features such as Liquid Needle and Multi-Dosing Systems—ideal for streamlined, standardised testing in modern battery production.

Measuring surface tension doesn’t have to be complicated

Measuring surface tension is simpler than you might think, especially with the right tools. In battery research and manufacturing, mastering surface tension is not just a technical detail; it’s a performance driver. The way liquids wet, coat, and interact at interfaces directly shapes battery efficiency, safety, and lifespan.

With KRÜSS instruments from ATA Scientific, you can measure surface tension, contact angles, and surface free energy with precision and repeatability. Whether you need a portable device for quick QC checks or a fully automated analyser for advanced R&D, our modular systems are built for accuracy, consistency, and high-throughput workflows.

When you integrate these capabilities into your process, you’re not just collecting data—you’re accelerating innovation, optimising material compatibility, and boosting overall battery performance.

Bottom line: Accurate surface tension measurement is essential for building high-performance, reliable, and safe batteries.

Talk to ATA Scientific today for expert guidance and a hands-on demo—see how KRÜSS technology can optimise your battery R&D and production.