Surfactant-Driven Dynamic Changes in Rheology of Activated Carbon Slurry Electrodes

Area of Science:

• Electrochemistry
• Materials Science
• Colloid Science

Background:

• Carbon black slurry electrodes enhance flow battery performance by increasing surface area.
• Challenges include maintaining slurry stability and flowability, which are affected by formulation.
• Understanding rheology-property relationships is crucial for advancing flow battery technology.

Purpose of the Study:

• To investigate the impact of surfactant concentration on the rheological properties of activated carbon (AC) based slurry electrodes.
• To determine the critical surfactant concentration that affects slurry stability, flowability, and electrical conductivity.
• To elucidate the relationship between slurry formulation and all-iron flow battery performance.

Main Methods:

• Linear and nonlinear rheological measurements of AC-based slurry electrodes with varying Triton X-100 concentrations.
• Characterization of the colloidal gel-to-fluid transition point.
• Assessment of electrical conductivity changes in response to surfactant concentration.

Main Results:

• The AC slurry exhibited characteristics of a colloidal gel with stable elasticity up to a critical surfactant concentration (α < 0.65).
• At α ≥ 0.65, the slurry transitioned abruptly to a fluid state, losing measurable yield stress.
• This transition correlated with a complete loss of electrical conductivity, indicating gel collapse.

Conclusions:

• Site-specific adsorption of surfactant molecules significantly impacts slurry electrode stability and flowability.
• Additive selection during slurry formulation is critical for optimizing flow battery performance and preventing conductivity loss.
• The study highlights the importance of rheological characterization in designing effective flow battery electrode materials.