Electrochemical conversion of halogenated compounds and associated systems

Patent metadata

Field	Value
Publication number	US-2021028522-A1
Application number	US-201716338947-A
Country	US
Kind code	A1
Filing date	Oct 3, 2017
Priority date	Oct 3, 2016
Publication date	Jan 28, 2021
Grant date	—

Abstract

Methods and systems for the electrochemical conversion of halogenated compounds are provided. In some embodiments, a method comprises converting a halogenated compound (e.g., fluorinated gas) to relatively non-hazardous products via oik* or more electrochemical reactions. The electrochemical reaction(s) may occur under relatively mild conditions (e.g., low temperature) and/or without the aid of a catalyst. In some embodiments, the electrochemical reaction may produce a relatively large amount of energy. In some such cases, systems, described herein, may be designed to facilitate the conversion of the halogenated compound (e.g., SF6, NF3) while harnessing (e.g.. storing, converting) the energy associated with the electrochemical reaction. System and methods described herein may be used in a wide variety of applications, including waste management (e.g.. environmental remediation, greenhouse gas mitigation), energy recovery (e.g., industrial energy recovery), and primary batteries (e.g., metal-gas batteries).

First claim

What is claimed is:

1 . A system, comprising:
an anode; a porous cathode. an electrolyte; and a halogenated compound, wherein the halogenated compound is a gas at standard temperature and pressure.

2 . A sealed electrochemical cell, comprising:
an anode comprising an alkali metal; a cathode; an electrolyte; and a halogenated compound, wherein the halogenated compound is a gas at standard temperature and pressure.

3 . A method, comprising:
in an electrochemical cell, reacting a fluorinated compound with a metal under suitable conditions to form a metal fluoride, wherein the fluorinated compound is a gas at standard temperature and pressure and the metal has a standard reduction potential of less than or equal to about −1.4 V vs. the standard hydrogen electrode.

4 . A method, comprising:
at an electrified interface, reacting a fluorinated compound with a metal under suitable conditions to form a metal fluoride, wherein the fluorinated compound is a gas at standard temperature and pressure and the metal has a standard reduction potential of less than or equal to about −1.4 V vs. the standard hydrogen electrode.

5 . The system of any preceding claim, wherein the anode comprises a metal selected from the group consisting of alkali metals and alkaline earth metals.

6 . The system of any preceding claim, wherein the anode comprises lithium or sodium.

7 . The system of any preceding claim, wherein the anode comprises a metal having a standard reduction potential of less than or equal to about −1.4 V vs. the standard hydrogen electrode.

8 . The system of any preceding claim, wherein at least a portion of the anode is coated with a passivation layer.

9 . The system of any preceding claim, wherein the cathode has a void volume of greater than or equal to about 10%.

10 . The system of any preceding claim, wherein the cathode comprises carbon, a noble metal, transition metal, metal oxide, or metal fluoride.

11 . The system of any preceding claim, wherein the cathode comprises carbon nanotubes, graphene, and/or carbon nanofibers.

12 . The system of any preceding claim, wherein the electrolyte is non-aqueous.

13 . The system of any preceding claim, wherein the electrolyte comprises an organic solvent.

14 . The system of any preceding claim, wherein the electrolyte is a liquid.

15 . The system of any preceding claim, wherein an electrochemical stability window of the electrolyte is between about −2 V and +3.5V vs. the standard hydrogen electrode.

16 . The system of any preceding claim, wherein the electrolyte comprises a metal salt.

17 . The system of any preceding claim, wherein the solubility of the halogenated compound in the electrolyte at 298K and 1 atm is greater than or equal to about 1 mM.

18 . The system of any preceding claim, wherein the halogenated compound is a fluorinated compound.

19 . The system of any preceding claim, wherein the halogenated compound is selected from the group consisting of sulfur hexafluoride, nitrogen trifluoride, and perfluorinated fluorocarbons.

20 . The system of any preceding claim, wherein a discharge capacity of the system is greater than or equal to about 500 mAh/g of carbon.

21 . The method of any preceding claim, comprising reacting the halogenated compound with a metal in the electrolyte to form a metal halide.

22 . The method of any preceding claim, wherein suitable conditions comprise a temperature of less than or equal to about 60° C.

23 . The method of any preceding claim, wherein suitable conditions comprise a pressure of greater than or equal to about 1 atm.

24 . The method of any preceding claim, wherein the electrolyte is a non-aqueous solvent.

25 . The method of any preceding claim, wherein the reacting step occurs at a cathode.

26 . The method of any preceding claim, wherein the fluorinated compound is reduced during the reacting step.

27 . The method of any preceding claim, further comprising forming a second reaction product as a result of the reacting step.

28 . The method of any preceding claim, wherein the metal selected from the group consisting of alkali metals and alkaline earth metals.

29 . The method of any preceding claim, wherein the metal is lithium or sodium.

30 . The system of any preceding claim, wherein the fluorinated gas is selected from the group consisting of sulfur hexafluoride, nitrogen trifluoride, and perfluorinated fluorocarbons.

31 . The method of any preceding claim, wherein the electrochemical cell is a galvanic cell.

Assignees

• Massachusetts Inst Technology

Inventors

• Gallant Betar
• Li Yuanda
• Khurram Aliza
• He Mingfu

Classifications

• Y02E60/10

  Energy storage using batteries · CPC title

• H01M12/04

  composed of a half-cell of the fuel-cell type and of a half-cell of the primary-cell type · CPC title

• H01M6/14 Primary

  Cells with non-aqueous electrolyte · CPC title

• H01M4/46

  Alloys based on magnesium or aluminium · CPC title

• H01M4/40

  Alloys based on alkali metals · CPC title