Advancing our Understanding of Battery production

26 Jun, 2024 | Newsletters
Advancing our Understanding of Battery production

This is an exciting time for battery R&D and manufacturing in Australia. In the recent Federal budget, the Australian government unveiled its National Battery Strategy, aimed to position Australia as a competitive battery producer. The additional funding proposed is aimed to encourage battery production, spread over seven years and administered by the Australian Renewable Energy Agency (ARENA).

The scheme, known as “Battery Breakthrough,” will commence soon as the government works with industry stakeholders and focuses projects on raw minerals, energy storage, industrial batteries, and standards development. Australia is envisioned to become a “renewable energy superpower” by moving beyond a traditional “dig and ship” economy. Despite supplying half of the global lithium, Australia currently produces less than one percent of the world’s processed battery components. The National Battery Strategy aims to change this by creating well-paid, secure jobs in the battery technology sector.

ATA Scientific together with their innovative manufacturers like KRUSS Scientific provide a wide range of technology that can help advance understanding of batteries and battery systems, and to engage in the current and next generation of devices and applications.

Here we introduce some of the current major challenges associated with battery production and discuss the latest technologies available for ensuring high quality battery manufacturing.

The life expectancy of lithium-ion batteries is closely linked to the coating adhesion strength of lithium-ion battery electrodes. Testing the adhesion strength allows us to predict the mechanical bond created is suitable before it is actually used, saving time and money.

In cell production there are many coating and bonding steps that occur. Understanding the surface science of each step is crucial for achieving high quality batteries. Typically the process starts with active binder material and the conductive agent together with solvent mixed together in specific mass ratios to create a slurry. This electrode slurry is then applied to a current collector foil and dried to remove excess solvent. The calendaring step compresses the porous electrode to the desired thickness by passing them through two rotating barrels. Calendering decreases the electrode’s porosity, which leads to an increase in energy density due to a smaller volume, as well as improvements in adhesion and coating uniformity. The electrodes are then cut into the desired shapes, stacked with separators in between and electrolyte is injected and filled to form a battery cell. Ensuring that the liquid fully permeates and wets the pores is an important step to ensure optimum mass and charge transport.

What are typical challenges in electrode production?

The slurry ingredients and preparation plays an important role in final coating which affects the performance of the battery produced. The uniform dispersion of active material and binder is important because it influences the electrochemical properties which can affect battery capacity, voltage, stability and lifecycle. The drying step can introduce thermal and mechanical stresses affecting the adhesion of the fluid with the active surface. The cutting and calendaring can also cause defects in the coating which has a strong impact on pore size affecting the wetting behaviour and therefore the electrode functionality. In addition, complete wetting of battery electrode pores during the electrolyte filling process can be a major bottle neck. How long this takes depends on the entire process from chemical composition of the raw materials, the layer thickness and density, to the wetting properties of the electrolyte.

Cell production process – coating and bonding

Coating and bonding steps are also present during the assembly of individual cells into packs or modules. Individual cells typically wrapped in an aluminium housing have a functional coating. A heat shield is added in between cells to contain thermal conditions and prevent overheating. These are then stacked with adhesive to form a module together with side covers and cooling plates. Several modules are joined together on a base plate and finally sealed with a cover. The adhesive used needs to able to withstand expansion and contraction during the charging and discharging cycles and be applied evenly without air pockets to prevent overheating that can compromise performance or in the worst case can be a severe safety issue.

Surface science can help solve these challenges to advance battery production

For Li-ion battery production, contact angle measurements and interfacial testing can be used to optimise key properties such as the adhesion of housing seals, which results in improved battery durability and enhanced safety. Interfacial testing can help differentiate and optimise batteries with key benefits including longer battery life and quicker charges. For example, reducing electrolyte surface tension to improve saturation of electrode and separator membrane helps increase overall battery performance. Interfacial testing equips researchers to not only properly wet the electrodes, but also speed up the historically time-consuming process.

Optimising wetting and adhesion applied to battery production

Interfacial tension measurements assess the physical and chemical phenomena that occur at the interface of two phases (i.e., solid-liquid, solid-gas, liquid–gas). Despite being a core part of advanced materials design, interfacial testing is vastly underutilised in Li-ion battery development and production. The interfaces between the electrolyte solution, separator membrane, electrodes, and current collectors have significant influence.

Drop shape analysers help analyse wetting of electrodes, determine the saturation of the separator membrane and can help optimise the coating of current collector with the slurry. Tensiometers can provide further benefits by measuring the dispersibility of electrode materials in the slurry, they can optimise the wetting rate for multiple battery components and monitor the electrolyte surface tension for a flawless ion transfer.

When considering basic principles for wetting, surface tension and adhesion, achieving optimum wettability of the solid components by the electrolyte solution yields optimum battery performance.

Interfacial testing can provide 5 important opportunities for improvement.

1. Wetting the separator membrane

Lithium ions travel through the electrolyte to penetrate the membrane; a poorly wetted membrane inhibits electrolyte saturation. Separator issues carry a high safety risk and can lead to fires. Using an optical tensiometer, Sessile drop or Wilhelmy method measurements can be applied to determine the electrolyte contact angle on the separator membrane. Results can enable faster, more thorough saturation of separator which results in improved battery performance, quicker ROI, and increased safety.

2. Wetting the electrodes

Complete wetting of porous electrode material by the electrolyte is crucial for capacity and high current charging. The electrolyte wetting process is a major bottleneck, as it can take hours or even days. Contact angle of the electrolyte on porous electrode material with the Washburn method or optical high-speed recordings (sessile drop) can be applied to achieve faster, more complete wetting of the electrode can reduce processing time ensuring a high-capacity, high-current charging battery.

3. Wetting the current collector by electrode slurry

An optimum charge transfer requires complete and even distribution of the electrode slurry onto the current collector. Improper contact or uneven layering of the electrode slurry on the collector foil causes irreparable loss of battery performance. Contact angle of the electrode slurry on collector foil by sessile drop or Wilhelmy method can help achieve an even spread of electrode to optimise charge transfer to improve process efficiency and reduces risk of irreparable performance degradation.

4. Surface tension of the electrolyte solution

The higher the surface tension of the electrolyte, the lower the wettability of the electrode material and separator membrane. Tensiometry with ring-/plate-method or pendant drop and dynamic analysis measured via bubble pressure can help users to reduce surface tension to improve saturation and optimise the compatibility of the electrode and separator membrane to increase battery performance.

5. Adhesion of the housing seal

Battery housing seals need to be very durable and reliable. Adhesion failures can lead to damage and safety risks. Adhesion analysis via contact angle testing (i.e. sessile drop) and tensiometry can help improve battery durability and enhanced safety.

KRUSS provides a wide variety of advanced interfacial testing technologies all controlled using a single powerful collaborative software platform.

KRUSS Tensiio is a high performance automated tensiometer designed to measure surface and interfacial tensions with high precision and efficiency. Its advanced features make it particularly useful for various aspects of battery research and development including electroyte formulation and electrode material optimisation. The ability to perform dynamic surface and interfacial tension measurements allows researchers to study how these properties change over time and under different conditions, such as temperature variations and the presence of impurities. This provides deeper insights into the stability and performance of battery components under real-world conditions.

KRUSS DSA100 Drop shape analyser measures contact angle, surface tension, and interfacial tension to understand wetting and adhesion behaviour. The device typically uses high-speed cameras and advanced software to analyse the shape of a liquid droplet on a solid surface, providing precise data about surface properties. It can be used to optimise wetting of electrodes and separators, Electrolyte compatibility, Homogeneity of slurry coatings and quality control during manufacturing.

The contact angle measurement provided by the KRUSS DSA100 helps to determine how well a liquid (like an electrolyte) spreads on a solid surface (like an electrode). Lower contact angles indicate better wettability, which is desirable for uniform coating and efficient electrode performance. By analysing how different surface treatments affect wettability, electrode surfaces can be optimised to enhance performance and longevity.

KRUSS Ayriis offers a mobile, stand-alone, 3D contact angle instrument with easy-to-exchange rechargeable batteries and prefilled cartridges. The Ayríís is ideal to quickly determine the wettability of solid materials before coating or bonding.

KRUSS MSA One click SFE provides portable contact angle and surface energy measurement, directly on production lines or field locations. Simple to setup and operate for quick assessments the MSA is ideal for quality control without damaging samples.

If you are eager to explore the capabilities of the KRUSS surface science technologies, we are delighted to offer you a personal demonstration. Request a guided demo using your own samples with a product specialist.

Contact us today!