Neutral-pH Iron-Complex Electrolyte for Stable Redox Flow Batteries
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Solution Overview
Problem
Existing redox flow batteries face challenges in achieving high capacity and stability at neutral pH, with existing electrolytes being toxic, unstable, or prone to precipitation, and requiring alkaline conditions that lead to environmental risks and inefficiencies.
Innovation Solution
A redox flow battery design using an aqueous solution of iron complexes with ethylenediamine-based ligands of formula I, which are stable at neutral pH and exhibit a highly negative redox potential, separated by an ion exchange membrane, and paired with a suitable electrolyte solution in the second half-cell.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If existing redox flow batteries use conventional electrolytes (vanadium-based or alkaline iron complexes), then high capacity can be achieved, but toxicity and environmental risks increase
Solution Approach 1:
The patent changes the chemical parameters of the electrolyte by using iron complexes with ethylenediamine-based ligands at neutral pH (pH 5-10) instead of conventional vanadium-based electrolytes or highly alkaline iron complexes. This parameter change maintains high capacity while eliminating toxicity and environmental risks associated with vanadium and highly alkaline conditions.
2Stability of the object's composition
If highly alkaline conditions are used to stabilize iron complexes, then complex stability improves, but corrosion risks and environmental concerns increase
Solution Approach 1:
The patent changes the pH parameter from highly alkaline conditions (pH > 12) to neutral conditions (pH 5-10). The ethylenediamine-based ligands form stable iron complexes at this neutral pH range, eliminating corrosion risks and environmental concerns associated with highly alkaline electrolytes while maintaining complex stability.
3Object-affected harmful factors
If existing electrolytes are used at neutral pH, then environmental safety improves, but stability and precipitation resistance deteriorate
Solution Approach 1:
The patent uses composite ligand structures containing ethylenediamine-based moieties combined with additional functional groups (such as hydroxyl, carboxyl, or phosphate groups). This composite ligand design creates stable iron complexes at neutral pH that resist precipitation, achieving both environmental safety and compositional stability.
4Power
If the redox couple provides highly negative potential, then cell voltage and energy density improve, but electrolyte stability and resistance to precipitation worsen
Solution Approach 1:
The patent optimizes the ligand structure parameters (such as denticity, chelate ring size, and functional groups) to achieve the right balance between redox potential and stability. The ethylenediamine-based ligands provide highly negative redox potentials for high energy density while maintaining electrolyte stability and preventing precipitation through strong chelation.
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 solution provides a stable, non-toxic, and efficient redox flow battery operation in the pH range of 5-10, achieving a large potential difference and high capacity without environmental risks, suitable for large-scale energy storage applications.
Implementation Method 1
said first and second half-cells are separated from each other by an ion exchange membrane
Implementation Method 2
said first electrolyte storage comprises an aqueous solution comprising an iron complex of compound of formula I
Data Source
AI summary
A redox flow battery, comprising a first electrolyte storage (1), a second electrolyte storage (2), an electrochemical cell connected to said first and second electrolyte storages (1, 2), wherein said electrochemical cell comprises a first half-cell and a second half-cell, wherein said first half-cell comprises a cathode (7), wherein said second half-cell comprises an anode (8), wherein said first and second half-cells are separated from each other by an ion exchange membrane (9), wherein said first electrolyte storage comprises an aqueous solution comprising an iron complex of a compound of formula Iand stereoisomers of compound of formula I.