How to Optimize Battery Electrode Slurries with Rheology
Morgan Ulrich | Julienne Regele | Hang Lau
September 12, 2023
From lightweight laptops to cross-country EV driving, countless applications require increasing lithium-ion batteries’ energy density and performance. Since battery electrodes directly contribute to these aspects of battery function, electrodes and their components are of particular interest to battery researchers seeking to advance technology to the next level. Battery slurry processing is also a key step of manufacturing, offering significant opportunities to increase efficiency while reducing cost.
Optimizing a slurry’s stability and flowability requires finding the right formulation of cathode/anode materials, binder, additives, and solvent. Rheology, the study of flow and deformation of materials, is a useful analysis method slurry research, development, and quality control.
Rheology helps battery producers measure and analyze key slurry qualities, including:
- Mixing and coating
- Structural changes and recovery
- Stability and shelf life
- Electrode homogeneity
- Quality control
What Does Rheology Measure?
Three rheological measurements are crucial for battery slurries: viscosity, thixotropic index, and yield stress.
Viscosity measures a slurry’s resistance to flow, or its internal friction. A slurry’s formulation and raw materials can greatly alter its flow behavior. Understanding a slurry’s flow is important for optimizing processing conditions for mixing and coating.
Thixotropic behavior describes the time-dependent changes in a material’s structural deformation. It provides insight into the slurry’s structure at rest, how it deforms during coating, and how quickly it will recover after coating.
Yield stress is the applied stress at which the material starts to flow. At stress values below the yield stress, the material does not flow. Yield stress is crucial for predicting a slurry’s shelf life and stability against sedimentation.
Optimizing Slurry Formulations and Processing Methods
Slurry rheology helps researchers determine the best formulation for their electrodes. For example, rheology can sensitively differentiate stability conditions between multiple different slurry formulations. A study done in Essential Battery Slurry Characterization Techniques used rheological analysis to identify superior homogeneous mixtures and better battery performance. See the experiment and results in the eBook here.
The electrode slurry matrix includes active powders that are critical for battery function and performance. Powder rheology measures cohesion, yield strength, and flow of a powder material. The shape, size and surface treatments of a powder, however, can alter the way a slurry behaves, from decreasing viscosity to ease of dispersing. Powder rheology offers insights into ideal storage conditions and processing for optimal powder flow while preventing agglomeration of powder. See how powder rheology helps reduce aggregates and achieve homogenous electrode coatings in the study on page eleven of Essential Battery Slurry Characterization Techniques eBook.
Researchers also use rheology to develop better processing conditions for their electrode slurries. Hawley and Li from Oak Ridge National Laboratory and the University of Tennessee, respectively, published their findings on slurry mixing and coating temperatures using a TA Instruments Discovery Hybrid Rheometer to investigate their slurry’s properties to optimize processing conditions. They found that increasing the processing temperature offers faster, more defect-free coating while reducing waste from processing and improving sedimentation resistance.
Electrode Slurry Rheology in Your Lab
With cutting-edge, intuitive technology, obtaining reliable slurry rheology measurements and analysis is easier than ever. TA Instruments Discovery Hybrid Rheometer sets the industry standard for performance, ease of use, and versatile rheological testing.
For a personalized look at how slurry rheology can advance your battery development, contact TA Instruments experts.
Learn more about applying slurry rheology and see real experiment examples in the complete Slurry Rheology eBook. This free resource compiles studies that demonstrate how to optimize slurry formulations and processing conditions for enhanced battery performance.Download Slurry Rheology eBook