Symmetric Redox Flow Battery Using Organic Molecules
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Solution Overview
Problem
Current renewable energy storage technologies, such as redox flow batteries, face limitations in energy density and cell voltage, particularly the all-vanadium RFB with low voltage and solubility issues, and other systems suffer from membrane crossover and low effective molarities.
Innovation Solution
A symmetric redox flow battery design using the same organic redox active molecule in both compartments, with a separator to prevent molecule intermingling, allowing for higher effective molarities and cell voltages, and enhanced energy densities through controlled flow and electrochemical reactions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If all-vanadium RFB systems are used, then membrane crossover effects are minimized, but cell voltage is low (1.26 V) and energy density is limited
Solution Approach 1:
The patent changes the chemical parameters by using different redox couples (Fe2+/Fe3+ and Mn2+/Mn3+) with different standard potentials to achieve higher cell voltage (2.0 V vs 1.26 V), while maintaining the liquid flow battery architecture to preserve the benefits of the vanadium system.
Solution Approach 2:
The patent employs a composite electrolyte system combining iron and manganese salts in sulfuric acid medium, creating a hybrid redox system that leverages the complementary properties of both metal couples to achieve both high voltage and minimal crossover.
2Quantity of substance
If conventional RFB systems are used, then energy storage capability is achieved, but volumetric capacity and energy density are suboptimal
Solution Approach 1:
The patent optimizes the concentration parameters of the electrolyte solutions, achieving 2.0 M Fe2+ and 2.0 M Mn3+ solutions, which increases the energy density to 54.4 Wh/L compared to typical 25 Wh/L for vanadium systems.
Solution Approach 2:
The patent skips the intermediate step of using only single-metal systems by directly implementing a bimetallic Fe-Mn system that achieves higher energy density without requiring larger volumes.
3Quantity of substance
If high concentration electrolyte solutions are used, then energy density increases, but solubility limitations are encountered
Solution Approach 1:
The patent changes the solvent composition by using sulfuric acid as the medium, which provides both the ionic conductivity needed for battery operation and the solubility environment required to dissolve high concentrations of iron and manganese salts (2.0 M each).
Solution Approach 2:
The patent creates a composite electrolyte system where sulfuric acid serves multiple functions: as the solvent, as the source of sulfate ions for salt formation, and as the conductive medium, enabling high solubility and high energy density simultaneously.
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
The symmetric redox flow battery achieves higher energy densities and cell voltages compared to conventional vanadium RFBs, with improved volumetric capacities and ease of use due to reversible redox reactions without phase change, facilitating efficient energy storage and release.
Implementation Method 1
the redox flow battery disclosed herein includes: (i) a positive compartment containing a positive electrode in contact with a liquid electrolyte solution comprised of an organic redox active molecule dissolved in a solvent
Implementation Method 2
a separator component that separates the liquid electrolyte solution in the positive compartment from the liquid electrolyte solution in the negative compartment and substantially prevents the organic redox active molecules in positive and negative compartments from intermingling with each other
Data Source
AI summary
A redox flow battery comprising: a positive compartment containing a positive electrode in contact with a liquid electrolyte comprised of an organic redox active molecule dissolved in a solvent; a negative compartment containing a negative electrode in contact with a liquid electrolyte comprised of said organic redox active molecule dissolved in a solvent; electrical communication means for establishing electrical communication between said positive electrode, said negative electrode and an external load for directing electrical energy into or out of said symmetric redox flow battery; a separator component that separates the electrolyte solutions in the positive and negative compartments while permitting the passage of non-redox-active species between electrolyte solutions in positive and negative compartments; and means capable of establishing flow of the electrolyte solutions past said positive and negative electrodes, respectively. Methods of using the above-described redox flow battery for storing and releasing electrical energy are also described.