In situ distributed diagnostics of flowable electrode systems: resolving spatial and temporal limitations
C R Dennison1, Y Gogotsi, E C Kumbur
1Electrochemical Energy Systems Laboratory, Department of Mechanical Engineering and Mechanics, Drexel University, 3141 Chestnut Street, Philadelphia, Pennsylvania 19104, USA. eck32@drexel.edu.
Physical Chemistry Chemical Physics : PCCP
|July 25, 2014
Summary
This study introduces an in situ tool for analyzing flowable electrode systems. It reveals that flowing conditions significantly reduce volumetric capacitance in electrochemical flow capacitors due to poor conductivity and short residence times.
Area of Science:
- Electrochemistry
- Materials Science
- Chemical Engineering
Background:
- Electrochemical systems with flowable electrodes are crucial for energy storage.
- Understanding spatial and temporal effects in these systems is key to improving performance.
- Current diagnostic tools often lack the resolution to capture dynamic behavior in situ.
Purpose of the Study:
- To develop and validate an in situ distributed diagnostics tool for flowable electrode systems.
- To investigate the impact of flowing conditions on electrochemical flow capacitor performance.
- To identify the underlying causes of performance limitations in suspension electrodes.
Main Methods:
- Development of an experimental approach for in situ, real-time, spatially-resolved voltage measurements.
- Creation of an equivalent circuit model with a novel 'flow capacitor' element to interpret distributed data.
- Application of the developed diagnostics tool to study suspension electrodes in an electrochemical flow capacitor under static and flowing conditions.
Main Results:
- Volumetric capacitance dramatically decreased from 15.6 F ml⁻¹ to 1.1 F ml⁻¹ under flowing conditions.
- Charging predominantly occurred within 750 μm of current collectors in flowing suspension electrodes.
- Significant state-of-charge gradients and active material underutilization were observed during flow.
Conclusions:
- High slurry electrical resistance, stratified charging, and insufficient residence time limit performance in flowing suspension electrodes.
- There is a critical need for more conductive slurries in electrochemical flow capacitors.
- Cell designs should prioritize reduced charge transport lengths to enhance active material utilization.
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