Sulfone Redox Molecules for High-Voltage Symmetric Flow Batteries
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Solution Overview
Problem
Existing redox flow batteries face challenges with redox crossover, leading to capacity loss due to concentration gradients of redox-active species across ion-transport membranes, and are limited by solvent decomposition at high cell potentials, especially in aqueous systems.
Innovation Solution
The use of oxidized sulfur-containing heterocyclic molecules, specifically sulfones, as electroactive bipolar redox molecules in a symmetric redox flow battery system, where the anolyte and catholyte are separated by a non-conjugating insulating linker, allowing for high cell potentials up to 3.0 V and suppressing solvent decomposition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If dissimilar redox species are used at anode and cathode electrolytes, then the battery can operate with different redox potentials, but concentration gradients cause redox crossover and capacity loss
Solution Approach 1:
The patent employs identical redox-active species (sulfur-containing heterocycles) in both anolyte and catholyte, creating a symmetric redox flow battery. This homogeneity eliminates concentration gradients across the membrane, preventing redox crossover and capacity loss while maintaining operational power through controlled electrochemical reactions at each electrode
2Quantity of substance
If high cell potentials are used to increase energy density, then more energy can be stored per volume, but solvent decomposition occurs especially in aqueous systems
Solution Approach 1:
The patent transitions from aqueous solvents to non-aqueous solvents (acetonitrile, dimethyl carbonate, ethyl methyl carbonate), fundamentally changing the solvent parameter to enable operation at high cell potentials (≥3.0 V) without decomposition. The sulfur-containing heterocycle redox species are specifically selected to be electrochemically stable in these non-aqueous environments, allowing high energy density while preventing harmful solvent breakdown
3Ease of manufacture
If aqueous solvents are used, then the system is simple and safe, but the maximum cell potential is limited by water electrolysis
Solution Approach 1:
The patent changes the solvent parameter from aqueous to non-aqueous (acetonitrile-based electrolytes with lithium salts), which eliminates the water electrolysis limitation and enables cell potentials of 3.0 V or higher. This parameter change maintains ease of manufacture through straightforward electrolyte preparation while dramatically increasing the achievable power output and energy density
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 achieves stable, high-voltage operation with reduced capacity decay by using the same electroactive molecule on both sides of the membrane, enhancing energy density and cycle life, and eliminates the need for mined materials.
Implementation Method 1
oxidizing sulfur-containing heterocycles to produce valuable redox-active co-product
Implementation Method 2
The chemical reactions involve changes in the valence of dissolved electroactive species: a catholyte and an anolyte
Implementation Method 3
an ion-transporting membrane
Implementation Method 4
This diffusive redox-active species flux is referred to as redox crossover
Data Source
AI summary
Disclosed herein are a variety of systems, compositions, and methods for reversibly storing electrical energy in a redox flow battery with a unit cell potential equal to or greater than 3.0 volts (V). The system may include an electroactive redox molecule, a positive section, and a negative section. The electroactive redox molecule may comprise an anolyte moiety comprising a multi-ring conjugated system comprising at least one sulfone group, wherein an anolyte reaction occurs at a cell potential less than −1.50 V. The positive section may comprise a first metal electrode in contact with the electroactive bipolar redox molecule and a supporting electrolyte dissolved in a solvent. The negative section may comprise a second metal electrode in contact with the electroactive bipolar redox molecule and additional electrolyte dissolved in additional solvent.