Redox Flow Battery Separator Pressure Control

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Solution Overview

Problem

Redox flow batteries using microporous membranes face efficiency losses due to hydrophobicity issues, leading to poor wetting and gas bubble infiltration, which increase resistivity and reduce performance, especially during charging.

Innovation Solution

Maintaining a positive electrode compartment pressure greater than the negative electrode compartment pressure and ensuring a cross-over pressure less than the membrane break-through pressure helps reduce gas bubbles and ionic resistance, thereby enhancing the battery's performance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If microporous membranes are used as separators, then cost is reduced and resistivity is lowered, but ion selectivity deteriorates and gas bubble infiltration increases

Engineering Contradiction:

Improveseparator costVSAvoidion selectivity

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent employs a hybrid separator combining microporous membrane and IEM layers. The microporous membrane provides low resistivity and cost benefits, while the IEM layer restores ion selectivity. This composite structure resolves the contradiction by integrating materials with complementary properties to achieve both low cost and high reliability.

Inventive Principle:

Principle #40Composite materials

2Loss of energy

If microporous membrane layers are used, then overall resistivity is reduced, but gas bubble infiltration increases causing substantial resistivity increases

Engineering Contradiction:

ImproveresistivityVSAvoidgas bubble infiltration

Core Design Contradiction:

Loss of energyVSObject-affected harmful factors

Solution Approach 1:

The IEM layer acts as an intermediary between the microporous membrane and the electrolyte. It prevents gas bubbles from infiltrating into the microporous membrane while allowing ionic conduction. This mediator resolves the contradiction by blocking the harmful gas bubble infiltration pathway while maintaining the low resistivity benefit of the microporous structure.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Reliability

If hybrid separators with IEM and microporous membrane layers are used, then ion selectivity is improved, but device complexity increases

Engineering Contradiction:

Improveion selectivityVSAvoidseparator structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The separator is segmented into distinct functional layers: a microporous membrane layer for low resistivity and an IEM layer for ion selectivity. This segmentation allows each layer to perform its specialized function independently, resolving the contradiction by achieving high ion selectivity through functional division rather than requiring a single complex material.

Inventive Principle:

Principle #1Segmentation

4Object-affected harmful factors

If thorough wetting of microporous membrane is achieved, then gas bubble infiltration is reduced, but manufacturing difficulty increases

Engineering Contradiction:

Improvegas bubble infiltrationVSAvoidwetting process

Core Design Contradiction:

Object-affected harmful factorsVSEase of manufacture

Solution Approach 1:

The separator is pre-assembled with microporous membrane and IEM layers in a controlled manufacturing environment. The IEM layer is already positioned to prevent gas bubble infiltration before the battery operates. This preliminary action resolves the contradiction by addressing the wetting issue during manufacturing rather than requiring complex operational wetting procedures.

Inventive Principle:

Principle #10Preliminary action

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 approach effectively lowers ionic resistance across the separator, reduces gas bubble entrapment, and prevents membrane break-through, resulting in improved efficiency and performance of the redox flow battery system.

Implementation Method 1

maintaining a positive electrode compartment pressure greater than a negative electrode compartment pressure

Methodology Applied

Scientific EffectPressure gradient: Pressure Gradient

Implementation Method 2

maintaining a cross-over pressure less than a membrane break-through pressure

Methodology Applied

Scientific EffectPressure control: Pressure Increase

Data Source

PatentUS10680263B2Methods and systems for operating a redox flow battery system

Publication Date: 2020.06.09 ESS TECH INC

AI summary

A method of operating a redox flow battery, may include maintaining a positive electrode compartment pressure greater than a negative electrode compartment pressure, and maintaining a cross-over pressure less than a membrane break-through pressure, wherein the cross-over pressure equals the negative electrode compartment pressure subtracted from the positive electrode compartment pressure. In this way, ionic resistance across the separator can be maintained at a lower level by reducing gas bubbles trapped therein while reducing separator break-through, thereby increasing performance of the redox flow battery system.