Electrode entrainment
The UK Battery Industrialisation Centre (UKBIC) has released a new white paper detailing pioneering work to tackle one of the most persistent manufacturing challenges in lithium-ion battery production, the air entrainment in electrode slurries during wet slurry casting
UKBIC is the UK’s national manufacturing development facility, providing scale-up, laboratory expertise, module and pack assembly, and helps to develop skills to support the sector. In addition to providing equipment, technical expertise and training to support manufacturers, UKBIC also supplies its own benchmark products for component testing and delivers specialist training to develop the skills required for a battery-powered future.
AIR ENTRAINMENT CHALLENGES
Air bubbles introduced during slurry mixing and delivery can create defects in coated electrodes, ultimately compromising battery performance, reliability, and safety. In response, UKBIC has delivered a programme of research and engineering development to understand, mitigate, and prevent air entrainment at every stage of the manufacturing process.
The new paper outlines the methodologies, models, and equipment improvements implemented by UKBIC’s in house technical teams to address this issue. The work spans process optimisation, formulation refinement, and equipment redesign, thereby demonstrating that defect prevention requires an integrated approach across technology teams.
A SYSTEMS-LEVEL APPROACH
UKBIC’s research combines physics-based modelling with experimental validation to better understand the mechanisms of degassing and bubble behaviour. Led by senior process simulation engineer Dr Helen Walker, the team developed advanced models to predict degassing performance under different viscosity, density and vessel geometry conditions.
The team also implemented targeted design improvements to slurry delivery systems to reduce air ingress points and minimise opportunities for air entrainment. Alongside this, they refined coating parameters to ensure bead stability during slot die coating via CFD and analytical modelling which helped to define robust operating windows.
“The findings demonstrate UKBIC’s commitment to strengthening the UK’s battery manufacturing competitiveness through process insight, practical engineering solutions, and collaborative R&D,” says Walker. “The centre’s work provides manufacturers with clearer tools, models, and best practices to reduce defects, improve yields and produce higher performance electrodes at scale.”
The paper highlights several important insights for battery manufacturers. The first: air entrainment is a critical manufacturing challenge, strongly influencing coating quality, electrochemical performance, and long-term cell reliability. As a direct result, understanding degassing behaviour is essential: while vacuum degassing accelerates bubble removal, its effectiveness depends on material properties and vessel design.
MIXING PROCESSES
The first step in electrode manufacturing is to combine active materials, binders, conductive additives, and solvents to form a homogeneous slurry. This mixing process is highly turbulent, and most of the air in the slurry is entrained at this point. Poor mixing can lead to particle agglomeration and non-uniform dispersion, resulting in uneven electrode thickness, inconsistent porosity, and weak adhesion to the current collector—all of which degrade battery performance and reduce manufacturing yield. Optimising solids content, additives and mixing processes can significantly reduce viscosity and shorten degass times.
AGITATOR DESIGN
Additionally, agitator geometry and slurry delivery system complexity have a strong impact on air ingress and degassing efficiency. During degassing, slurries are agitated to prevent separation and sedimentation. Agitator design significantly influences degas efficiency. While most agitators generate strong circumferential flow, only some designs effectively induce vertical circulation. Vertical currents help transport bubbles upward, allowing them to burst at the surface. Streamlined delivery systems minimise opportunities for re-entrainment.
COATING CONSIDERATIONS
Air bubbles introduced during slurry mixing or pumping can persist into the coating stage, where they burst during coating or drying, leaving voids or fisheyes in the electrode layer that may penetrate the entire electrode layer. These defects disrupt the uniformity of the active material layer, leading to discontinuities in the conductive network and uneven current distribution across the electrode surface. The result is localised overpotential and thermal hotspots that accelerate side reactions and mechanical degradation, while portions of active material remain underutilised, reducing energy density. Coating stability acts as a final safeguard. Slot-die coating requires precise control of bead stability, governed by viscous, capillary, and inertial forces. CFD and analytical models help define the operating window to prevent air entrainment at the coating stage. Meanwhile, effective defect mitigation improves product yield and reliability, reducing defects and enabling more uniform coatings, a higher energy density and longer cycle life.
FUTURE DEVELOPMENT
According to UKBIC’s whitepaper, a key area for future work is minimising air entrainment during slurry preparation. Without costly expenditure on new equipment which enables mixing in a vacuum, this could perhaps be achieved through optimised mixing strategies such as reducing mixing speeds, controlling the rate of material addition, and refining the order of addition. Transitioning from batch degassing to inline deaeration would represent a major process improvement, reducing overall processing time and eliminating unnecessary transfers between multiple vessels.
Read the full whitepaper at: White paper – Optimising Electrode Quality: Controllng Air in Battery Slurries for Superior Coating Performance
