Redox Flow Battery Electrode with Anisotropic Permeability
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Solution Overview
Problem
Redox flow batteries using carbon nanotubes as electrode materials experience high pressure drops due to poor electrolyte solution passage properties, leading to uneven flow distribution and reduced reactive species substitution efficiency, which affects battery performance.
Innovation Solution
Incorporating a conductive sheet with carbon nanotubes of 1 µm or less average fiber diameter, along with a liquid inflow member and a liquid outflow member, where the Darcy permeability in the in-plane direction is significantly higher than in the normal direction, to enhance electrolyte solution flow and reduce pressure drops.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If carbon nanotubes with average fiber diameter of 1 µm or less are used as electrode material, then electrical capacity and reactivity are improved, but pressure drop increases due to poor electrolyte solution passage properties
Solution Approach 1:
The patent employs a porous conductive sheet as the electrode structure, which provides interconnected void spaces that allow electrolyte solution to penetrate and flow through the carbon nanotube-containing material. The porous structure increases the effective surface area for electrochemical reactions while maintaining adequate fluid passage, thus improving both battery reactivity and reducing pressure drop compared to dense carbon nanotube structures.
2Productivity
If carbon nanotubes are used to improve battery properties, then electrical capacity increases, but flow distribution becomes uneven due to extremely fine structure
Solution Approach 1:
The patent applies local quality by creating regions with different structural characteristics within the electrode. The conductive sheet provides a macroscopic framework with adequate porosity for uniform flow distribution, while carbon nanotubes are distributed within this framework to provide localized high reactivity zones. This hierarchical structure ensures that no single region dominates the flow path, promoting uniform electrolyte distribution across the entire electrode surface.
3Stress or pressure
If felt containing carbon fibers is used as electrode material, then pressure drop is reduced, but battery reactivity and electrical capacity are insufficient
Solution Approach 1:
The patent creates a composite electrode material by combining carbon nanotubes with a conductive sheet matrix. The conductive sheet provides the macroscopic structural framework with adequate porosity for fluid flow (reducing pressure drop), while the carbon nanotubes dispersed within the sheet provide enhanced electrical conductivity and electrochemical reactivity. This composite structure achieves both low pressure drop and high battery reactivity, overcoming the limitations of using either material alone.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration effectively suppresses pressure drops and improves battery properties by ensuring efficient electrolyte solution flow and reactive species interchange during charging and discharging.
Implementation Method 1
the Darcy permeability, in an in-plane direction, inside the liquid outflow member, is at least 50 times the Darcy permeability, in a normal direction, through the conductive sheet
Implementation Method 2
The battery can be charged and discharged by making an oxidation reaction and a reduction reaction progress simultaneously on the electrode materials
Implementation Method 3
The battery can be charged and discharged by making an oxidation reaction and a reduction reaction progress simultaneously on the electrode materials
Data Source
Figure 1~2
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AI summary
An electrode material including a conductive sheet containing carbon nanotubes having an average fiber diameter of 1 µm or less; a liquid inflow member that is formed on a first surface of the conductive sheet such that an electrolyte solution that is passed therethrough flows into the conductive sheet; and a liquid outflow member that is formed on a second surface of the conductive sheet and out of which flows the electrolyte solution that has passed through the conductive sheet; wherein, when using a sheet surface of the conductive sheet as a reference plane, the Darcy permeability, in an in-plane direction, inside the liquid inflow member, is at least 100 times the Darcy permeability, in a normal direction, through the conductive sheet.