Nonaqueous redox flow battery electrolyte comprising an ionic liquid with a metal cation coordinated to redox-active ligands

Patent metadata

Field	Value
Publication number	US-10305133-B2
Application number	US-201715597474-A
Country	US
Kind code	B2
Filing date	May 17, 2017
Priority date	May 17, 2017
Publication date	May 28, 2019
Grant date	May 28, 2019

Abstract

Nonaqueous redox flow batteries (RFB) hold the potential for high energy density grid scale storage, though are often limited by the solubility of the redox-active species in their electrolytes. A systematic approach enables an increase the concentration of redox-active species in electrolytes for nonaqueous RFB, starting from a metal-coordination-cation-based ionic liquid. As an example, starting with an ionic liquid consisting of a metal coordination cation (MetIL), ferrocene-containing ligands and iodide anions can be substituted into the original MetIL structure, enabling a nearly 4× increase in capacity compared to original MetIL structure. Application of this strategy to other chemistries, optimizing electrolyte melting point and conductivity could yield >10 M redox-active electrons.

First claim

We claim:

1. A nonaqueous redox flow battery electrolyte, comprising a redox-active ionic liquid comprising a metal coordination cation coordinated to a number of redox-active ligands and an anion having an oxidation state, wherein the metal coordination cation comprises a transition metal ion and at least one of the redox-active ligands comprises an aminoalcohol, or a dialcoholamine, wherein the ionic liquid comprises Fe(EA) 6-x (FcEA) x (OTf) 2-y I y , wherein iron is the transition metal ion having a coordination number of 6, wherein the aminoalcohol is ethanolamine, 6-x is the number of ethanolamine ligands, and x is the number of {[(2-hydroxyethyl)amino]carbonyl}ferrocene redox-active ligands substituted for ethanolamine ligands, and wherein the anion is iodide, 2 is the oxidation state, and y is the number of iodide anions substituted for triflate anions.

2. The electrolyte of claim 1 , wherein x is 6 or less.

3. The electrolyte of claim 2 , wherein x is 1 or 2.

4. The electrolyte of claim 1 , wherein y is 2 or less.

5. The electrolyte of claim 4 , wherein y is 0 or 1.

6. The electrolyte of claim 1 , wherein the Fe(EA) 6-x (FcEA) x (OTf) 2-y I y comprises greater than 1.79 M and less than 4.2 M redox-active electrons in the ionic liquid.

Assignees

• Nat Tech & Eng Solutions Sandia Llc

Inventors

• Small Leo J
• Anderson Travis Mark
• Pratt Harry

Classifications

• H01M8/188 Primary

  by recharging of redox couples containing fluids; Redox flow type batteries · CPC title

• H01M8/1016

  characterised by the electrolyte material (H01M8/12 takes precedence) · CPC title

• H01M2300/0022

  Room temperature molten salts · CPC title

• Y02E60/50

  Fuel cells · CPC title