Application Note

Rheological Evaluation of Battery Slurries with Different Graphite Particle Size and Shape

Keywords: Rheology, Battery, Battery slurry, particle size, particle shape, viscosity, viscoelasticity, thixotropy, yield, Discovery Hybrid Rheometer (DHR)

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Battery slurry processing is one of the key steps in battery manufacturing that can significantly influence battery performance. The slurry suspension includes multiple components such as active cathode/anode materials, binder and additives etc. mixed in solvent. Differences in slurry formulation can have a big impact on a slurry’s stability and flowability. This application note discusses how to use rheology to evaluate the influence of graphite particle size and particle shape on the rheological behavior of a battery slurry. A TA Instruments rotational rheometer was used for the rheological analysis. The measurement results provide quantitative differentiation between two slurry samples with different types of graphite on their viscoelasticity, yield stress, and thixotropic behaviors. The difference in flow viscosities over a wide range of shear rates is also discussed in detail.

Application Benefits

  • A slurry’s rheological properties are critically important when studying stability and processability for electrode manufacturing.
  • A TA Instruments Discovery HR-30 rheometer provides guidance in slurry processing during battery electrode manufacturing by delivering a sensitive evaluation of the viscosity and viscoelasticity of battery electrode slurries.
  • Rheology can sensitively differentiate the difference between natural and synthetic graphite formulations, which contain different particle sizes and shapes.
  • The dynamic frequency sweep test measures sample moduli (G’, G”) and complex viscosity, and helps to compare sample viscoelasticity and network structure.
  • Thixotropy analysis measures the shear thinning properties of the slurries and also quantifies the sample structure recovery.
  • The flow test can measure samples’ yield stress. It also provides the viscosity information of the slurry over a wide range of shear rates.

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