Monosulfonated Catecholate Ligands for Flow Battery Solubility
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Solution Overview
Problem
Flow batteries face sub-optimal energy storage performance and limited cycle life due to the poor solubility of coordination complexes, particularly those containing organic ligands, which can lead to precipitation issues and damage within the battery system.
Innovation Solution
The synthesis of coordination complexes with a mixture of unsubstituted catecholate and monosulfonated catecholate ligands, such as 3,4-dihydroxybenzenesulfonic acid, is developed, enhancing solubility and stability, allowing for the formation of high-solubility coordination complexes that can be used in flow batteries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If coordination complexes containing organic ligands are used as active materials in flow batteries, then electrochemical performance can be achieved, but solubility is poor leading to precipitation and system damage
Solution Approach 1:
The patent modifies the chemical parameters of the ligand by introducing sulfonate groups (-SO3-) to the catecholate structure. This parameter change fundamentally alters the solubility characteristics of the coordination complex, transforming it from hydrophobic to hydrophilic, thereby enabling high solubility in aqueous electrolyte solutions while maintaining electrochemical activity
Solution Approach 2:
The patent creates a composite ligand structure combining catecholate (for electrochemical function) and sulfonate groups (for solubility enhancement). This composite approach integrates two functional moieties into a single ligand molecule, allowing the coordination complex to simultaneously achieve both electrochemical performance and high solubility
2Power
If concentration of active material is increased to achieve good electrochemical performance, then energy density improves, but precipitation risk increases damaging the system
Solution Approach 1:
By changing the chemical parameter of the ligand (adding sulfonate groups), the patent fundamentally alters the solubility product of the coordination complex. This allows the system to operate at much higher concentrations without reaching the precipitation threshold, thereby enabling high energy density while avoiding precipitation damage
3Quantity of substance
If a mixture of catechol and monosulfonated catechol is used to form coordination complexes, then solubility is enhanced, but ligand composition complexity increases
Solution Approach 1:
The patent employs a controlled parameter change approach where the ratio of catechol to monosulfonated catechol is optimized to achieve the desired solubility. By carefully adjusting this compositional parameter, high solubility is attained while keeping the ligand mixture relatively simple and manageable
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 approach improves the solubility and electrochemical performance of coordination complexes, reducing precipitation risks and maintaining desirable electrochemical properties, thereby enhancing the energy storage capabilities and operational stability of flow batteries.
Implementation Method 1
heating the neat mixture to form a reaction product containing a mixture of catechol and a monosulfonated catechol
Implementation Method 2
The flow battery is charged or discharged through electrochemical reactions of the active materials that occur inside the two half-cells
Implementation Method 3
The metal center can cycle between an oxidized form and a reduced form in an electrolyte solution, where the oxidized and reduced forms of the metal center represent states of full charge or full discharge
Data Source
AI summary
Coordination complexes can have a metal center with at least one unsubstituted catecholate ligand and at least one monosulfonated catecholate ligand or a salt thereof bound thereto. Some coordination complexes can have a formula of DgTi(L1)x(L2)y, in which D is a counterion selected from NH4+, Li+, Na+, K+, or any combination thereof; g ranges between 2 and 6; L1 is an unsubstituted catecholate ligand; L2 is a monosulfonated catecholate ligand; and x and y are non-zero numbers such that x+y=3. Methods for synthesizing such coordination complexes can include providing a neat mixture of catechol and a sub-stoichiometric amount of sulfuric acid, heating the neat mixture to form a reaction product containing catechol and a monosulfonated catechol or a salt thereof, and forming a coordination complex from the reaction product without separating the catechol and the monosulfonated catechol or the salt thereof from one another.