Three-Electrode Redox Flow Battery Overpotential Control

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Solution Overview

Problem

Redox flow batteries face excessive overpotential at one electrode, leading to decreased efficiency and energy storage capacity.

Innovation Solution

A three-electrode redox flow battery design with an auxiliary electrode that controls the potential of the working electrode, reducing overpotential requirements without significant faradaic activity at the auxiliary electrode, and featuring a power source to establish a voltage differential between the auxiliary and working electrodes, with a surface area ratio of at least 5:1.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a conventional two-electrode redox flow battery design is used, then the structure is simple, but excessive overpotential occurs at one electrode leading to decreased efficiency and energy storage capacity

Engineering Contradiction:

Improvebattery structureVSAvoidoverpotential

Core Design Contradiction:

Device complexityVSLoss of energy

Solution Approach 1:

The battery system is segmented into three separate electrodes (working electrode, counter electrode, and auxiliary electrode) instead of the conventional two-electrode design. The auxiliary electrode is electrically isolated from the working electrode by an insulating barrier, allowing independent potential control. This segmentation enables the working electrode to operate at optimal potential while the auxiliary electrode manages overpotential, thereby resolving the contradiction between structural simplicity and energy loss.

Inventive Principle:

Principle #1Segmentation

2Loss of energy

If an auxiliary electrode is added to control working electrode potential, then overpotential is reduced and efficiency increases, but device complexity increases

Engineering Contradiction:

ImproveoverpotentialVSAvoidelectrode configuration

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

An electrically insulating barrier is introduced as an intermediary between the auxiliary electrode and the working electrode. This barrier allows the auxiliary electrode to control the working electrode potential without direct electrical contact, preventing short circuits while enabling potential management. The insulating barrier acts as a mediator that resolves the complexity issue by providing a clear spatial and electrical separation between functional elements.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Loss of energy

If the auxiliary electrode surface area is increased to improve potential control, then overpotential management improves, but the surface area ratio requirements increase device complexity

Engineering Contradiction:

Improveoverpotential controlVSAvoidsurface area ratio

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The auxiliary electrode is positioned and sized with specific local characteristics - it has a surface area at least five times larger than the working electrode and is located at a distance no greater than one-tenth of the working electrode's radius. This localized optimization of the auxiliary electrode's spatial and dimensional properties enables effective potential control without requiring excessive surface area, thereby managing the complexity of the electrode configuration.

Inventive Principle:

Principle #3Local quality

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 design increases current at the working electrode by 73:1 relative to the auxiliary electrode, enhancing efficiency and energy storage capacity.

Implementation Method 1

An auxiliary power source is configured to establish an auxiliary circuit voltage differential between the counter electrode terminal and the auxiliary electrode terminal, control an auxiliary electrode voltage such that the auxiliary electrode voltage is within an electrochemical window of the working side flowing electrolyte

Methodology Applied

Scientific EffectVoltage differential: Electric Field

Implementation Method 2

a working electrode in ionic contact with the working side of the ionically conductive separator and the working side flowing electrolyte

Methodology Applied

Scientific EffectIonic conduction: Conduction (electrical)

Implementation Method 3

Redox flow batteries tend to suffer from excessive overpotential at one of the electrodes

Methodology Applied

Scientific EffectRedox reactions: Redox Reactions

Data Source

PatentEP3853938B1Method and system to modify the performance of a redox flow battery

Publication Date: 2023.03.29 SAUDI ARABIAN OIL CO

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AI summary

A redox flow battery and a method of operating a redox flow battery. The redox flow battery includes an ionically conductive separator, a working side flowing electrolyte, a working electrode, a counter electrode, and an auxiliary electrode. The auxiliary electrode is in ionic contact with the working electrode, where an electrically insulating peripheral gap separates the auxiliary electrode from the working electrode. An auxiliary power source is configured to establish an auxiliary circuit voltage differential between a terminal in each of the counter electrode and the auxiliary electrode to control an auxiliary electrode voltage such that the auxiliary electrode voltage is within an electrochemical window of the working side flowing electrolyte, as well as to establish a voltage differential between the working electrode terminal and the auxiliary electrode terminal.