ADDITIVES FOR LITHIUM BATTERIES AND METHODS

• US 20200136182A1
• Filed: 10/30/2018
• Published: 04/30/2020
• Est. Priority Date: 10/30/2018
• Status: Active Application

• Current Assignee: UChicago Argonne LLC
• Original Assignee: UChicago Argonne LLC
• Inventors: LIAO, Chen, SHKROB, Ilya A., ABRAHAM, Daniel, ZHANG, Zhengcheng
• Granted Patent: US 10,847,840 B2
• Time in Patent Office: Days
• CPC Class Codes: H01M 10/0525 Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• CPC Class Codes: H01M 10/0567 characterised by the additives
• CPC Class Codes: H01M 10/0568 characterised by the solutes
• CPC Class Codes: H01M 10/0569 characterised by the solvents
• CPC Class Codes: H01M 2300/0037 Mixture of solvents
• CPC Class Codes: H01M 4/505 of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
• CPC Class Codes: H01M 4/525 of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
• CPC Class Codes: H01M 4/587 for inserting or intercalating light metals
• CPC Class Codes: Y02E 60/10 Energy storage using batteries

Abstract

Lithium tetrafluoro(malonato)phosphate compounds are useful as additives in lithium ion battery applications. The compounds are represented by Formula (I): MPF₄[—O(C═O)—(CX′X″)—(C═O)O—]; wherein M is Li or Na; each X′ and X″ independently is selected from the group consisting of H, alkyl, fluoro-substituted alkyl, and F; or wherein the X′ and X″ together are —CR₂—(CR′₂)_m—CR″₂—; each R, R′ and R″ independently is selected from the group consisting of H, methyl, trifluoromethyl, and F; and m is 0 or 1. These compounds can be prepared in high purity and a high yield by reaction of a metal hexafluorophosphate with a bis-silyl malonate compound. A similar oxalato compound, lithium tetrafluoro(oxalato)phosphate), can be made in the same manner, but using a bis-silyl oxalate in place of the bis-silyl malonate. Advantageously, the compounds can be formed, in situ, in a LiPF₆-containing electrolyte solution.

Claims

1. A salt of Formula (I):

MPF₄[—

O(C═

O)—

(CX′

X″

)—

(C═

O)O—

];

wherein M is Li or Na;

each X′ and

X″

independently is selected from the group consisting of H, alkyl, fluoro-substituted alkyl, and F;

or wherein the X′ and

X″

together are an alkylene group of formula;

—

CR₂—

(CR′

₂)_m—

CR″

₂—

;

each R, R′ and

R″

independently is selected from the group consisting of H, methyl, trifluoromethyl, and F; and

m is 0 or 1.

2. The salt of claim 1, wherein M is Li.

3. The salt of claim 1, wherein at least one of X′

and X″

is F.

4. The salt of claim 1, wherein at least one of X′

and X″

is alkyl.

5. The salt of claim 1, wherein at least one of X′

and X″

is C₁ to C₄ alkyl.

6. The salt of claim 1, wherein X′

is F and X″

is methyl.

7. An electrolyte for a lithium ion electrochemical cell, the electrolyte comprising a non-aqueous organic solvent containing a lithium electrolyte salt at a concentration of about 0.5 to about 3 M, and an additive at a concentration of about 0.25 to about 5 percent by weight (wt %);

wherein the additive comprises a compound of Formula (I);

MPF₄[—

O(C═

O)—

(CX′

X′

″

)—

(C═

O)O—

];

wherein M is Li;

each X′ and

X″

independently is selected from the group consisting of H, alkyl, fluoro-substituted alkyl, and F;

or wherein the X′ and

X″

together are an alkylene group of formula;

—

CR₂—

(CR′

₂)_m—

CR″

₂—

;

each R, R′ and

R″

independently is selected from the group consisting of H, methyl, trifluoromethyl, and F; and

m is 0 or 1.

8. The electrolyte of claim 7, wherein the lithium electrolyte salt comprises 1 to 2 M LiPF₆.

9. The electrolyte of claim 7, wherein the non-aqueous solvent comprises at least one organic carbonate solvent.

10. The electrolyte of claim 7, wherein at least one of X′

and X″

is F.

11. The electrolyte of claim 7, wherein at least one of X′

and X″

is C₁ to C₄ alkyl.

12. The electrolyte of claim 7, wherein X′

is F and X″

is methyl.

13. The electrolyte of claim 7, wherein the compound of Formula (I) is present in the electrolyte at a concentration in the range of about 0.5 to about 2 wt %.

14. The electrolyte of claim 7, further comprising a silyl fluoride of formula FSiZ₃ wherein each Z independently is alkyl.

15. A lithium electrochemical cell comprising a cathode, an anode, a lithium-porous separator between the cathode and the anode, and an electrolyte of claim 7 contacting the cathode and the anode.

16. The electrochemical cell of claim 15, wherein the cathode comprises a lithium nickel-manganese-cobalt oxide compound.

17. The electrochemical cell of claim 15, wherein the anode comprises graphite.

18. The electrochemical cell of claim 15, wherein the compound of Formula (I) is present in the electrolyte at a concentration in the range of about 0.5 to about 2 wt %, and wherein the electrolyte salt is LiPF₆.

19. A battery comprising a plurality of the electrochemical cell of claim 15 electrically connected together.

20. A method of preparing the electrolyte of claim 7 in which the lithium salt is LiPF₆, comprising the steps of adding a bis-silyl ester compound to an electrolyte comprising the LiPF₆ in the non-aqueous organic solvent, and stirring the resulting mixture at ambient temperature for at least about 24 hours to form the salt of Formula (I), in situ;

wherein the bis-silyl ester is a compound of Formula (II);

Z₃Si—

O(C═

O)—

(CX′

X″

)—

(C═

O)O—

SiZ₃;

each X′ and

X″

independently is selected from the group consisting of H, alkyl, fluoro-substituted alkyl, and F;

or wherein the X′ and

X″

together are an alkylene group of formula;

—

CR₂—

(CR′

₂)_m—

CR″

₂—

;

each R, R′ and

R″

independently is selected from the group consisting of H, methyl, trifluoromethyl, and F;

m is 0 or 1; and

each Z independently is alkyl.

21. The method of claim 20, wherein byproduct FSiZ₃ that is formed by the reaction of the LiPF₆ with the compound of Formula (II) is retained in the electrolyte.

22. A method of preparing an electrolyte comprising a solution of LiPF₆ in a non-aqueous organic solvent and an additive comprising a compound of Formula (V):

23. The method of claim 22, wherein byproduct FSiZ₃ that is formed by the reaction of the LiPF₆ with the compound of Formula (VI) is retained in the electrolyte.

24. The method of claim 22, wherein byproduct FSiZ₃ that is formed by the reaction of the LiPF₆ with the compound of Formula (VI) is removed from the electrolyte by volatilizing the FSiZ₃.