Borohydride solvo-ionic liquid family for magnesium battery

Patent metadata

Field	Value
Publication number	US-9362594-B2
Application number	US-201514805471-A
Country	US
Kind code	B2
Filing date	Jul 22, 2015
Priority date	Dec 19, 2012
Publication date	Jun 7, 2016
Grant date	Jun 7, 2016

Abstract

A method for forming a solvo-ionic liquid suitable for use as an electrolyte in an electrochemical cell is provided. The solvo-ionic liquid, a mixture including a multidentate ethereal solvent and magnesium borohydride, can be a liquid, a gel or a solid at room temperature and generally has high thermal stability including virtually no volatility at a typical cell operating temperature. An electrochemical cell having a solvo-ionic liquid as electrolyte is also disclosed. The electrochemical cell will typically be a rechargeable magnesium battery, having an anode suitable to accommodate magnesium oxidation during battery discharge.

First claim

What is claimed is:

1. A method for forming an electrolyte composition including a solvo-ionic liquid, the method comprising:
combining a multidentate ethereal solvent with a salt mixture to produce a solvate, the salt mixture containing Mg(BH 4 ) 2 , and the solvate having a molar ratio of multidentate ethereal solvent to Mg(BH 4 ) 2 within a range of 0.1:1 to 10:1, inclusive, wherein, due to the relative concentrations of the combined solvent and salt mixture, the solvate becomes the solvo-ionic liquid.

2. The method as recited in claim 1 , wherein the salt mixture further includes a second salt, the second salt being LiBH 4 , NaBH 4 or a combination thereof; and the second salt being present at a molar ratio relative to Mg(BH 4 ) 2 not greater than 10:1.

3. The method as recited in claim 1 , wherein the salt mixture further includes a third salt, the third salt having:
at least one of a lithium cation and a magnesium cation; and
a fluorinated anion;

wherein the third salt is present at a molar ratio relative to Mg(BH 4 ) 2 not greater than 10:1.

4. The method as recited in claim 3 , wherein the third salt is Mg(TFSI) 2 (bis trifluoromethano sulfonyl imide), Mg(FSI) 2 (bis fluorosulfonyl imide), Mg(BF 4 ) 2 , LiTFSI, LiFSI, LiBF 4 , or a combination thereof.

5. The method as recited in claim 1 , further comprising a step of ball-milling the salt mixture prior to combining the multidentate ethereal solvent with the salt mixture.

6. The method as recited in claim 1 , further comprising a step of mixing the solvate.

7. The method as recited in claim 6 , wherein the mixing step is performed by stirring for a duration of at least 24 hours.

8. The method as recited in claim 6 , wherein the step of mixing the solvate comprises ball-milling the solvate.

9. The method as recited in claim 1 , wherein the multidentate ethereal solvent comprises glyme, diglyme, triglyme, tetraglyme, polyethylene glycol or polyethylene oxide.

10. The method as recited in claim 1 , wherein the solvo-ionic liquid has a lowest decomposition temperature, the lowest decomposition temperature being equal to or greater than at least one of the following temperatures:
200° C.; and
a temperature within 20° C. of the boiling point of the multidentate ethereal solvent.

11. An electrochemical cell having:
an anode comprising elemental magnesium;
a cathode; and
an electrolyte composition comprising a solvo-ionic liquid that includes Mg(BH 4 ) 2 and a multidentate ethereal solvent, the Mg(BH 4 ) 2 and multidentate ethereal solvent present at a molar ratio within a range of 0.1:1 to 10:1, inclusive.

12. The electrochemical cell as recited in claim 11 , wherein the solvo-ionic liquid further includes a second salt which is LiBH 4 , NaBH 4 or a combination thereof, the second salt being present at a molar ratio not to exceed 10:1 relative to Mg(BH 4 ) 2 .

13. The electrochemical cell as recited in claim 11 , wherein the solvo-ionic liquid further includes a third salt, the third salt having:
at least one of a lithium cation and a magnesium cation; and
a fluorinated anion

wherein the third salt is present at a molar ratio relative to Mg(BH 4 ) 2 not greater than 10:1.

14. The electrochemical cell as recited in claim 13 , wherein the third salt is Mg(TFSI) 2 (bis trifluoromethano sulfonyl imide), Mg(FSI) 2 (bis fluorosulfonyl imide), Mg(BF 4 ) 2 , LiTFSI, LiFSI, LiBF 4 , or a combination thereof.

15. The electrochemical cell as recited in claim 11 , wherein the solvo-ionic liquid has a lowest decomposition temperature, the lowest decomposition temperature being equal to or greater than at least one of the following temperatures:
200° C.; and
a temperature within 20° C. of the boiling point of the multidentate ethereal solvent.

16. An electrolyte composition comprising a solvo-ionic liquid that includes Mg(BH 4 ) 2 and a multidentate ethereal solvent, the Mg(BH 4 ) 2 and ethereal solvent present at a molar ratio within a range of 0.1:1 to 10:1, inclusive.

17. The electrolyte composition as recited in claim 16 , wherein the solvo-ionic liquid further includes a second salt, the second salt being LiBH 4 , NaBH 4 or a combination thereof; and the second salt being present at a molar ratio relative to Mg(BH 4 ) 2 not greater than 10:1.

18. The electrolyte composition as recited in claim 16 , wherein the solvo-ionic liquid further includes a third salt, the third salt having:
at least one of a lithium cation and a magnesium cation; and
a fluorinated anion;
wherein the third salt is present at a molar ratio relative to Mg(BH 4 ) 2 not greater than 10:1.

19. The electrolyte composition as recited in claim 16 , wherein the solvo-ionic liquid has a lowest decomposition temperature, the lowest decomposition temperature being equal to or greater than at least one of the following temperatures:
200° C.; and
a temperature within 20° C. of the boiling point of the multidentate ethereal solvent.

Assignees

• Toyota Eng & Mfg North America

Inventors

• Mohtadi Rana

Classifications

• H01M10/0569

  characterised by the solvents · CPC title

• H01M10/054 Primary

  Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium · CPC title

• H01M2004/027

  Negative electrodes · CPC title

• H01M2300/0025

  Organic electrolyte · CPC title

• H01M10/0566

  Liquid materials · CPC title