Additives for lithium batteries and methods

Patent metadata

Field	Value
Publication number	US-10847840-B2
Application number	US-201816175497-A
Country	US
Kind code	B2
Filing date	Oct 30, 2018
Priority date	Oct 30, 2018
Publication date	Nov 24, 2020
Grant date	Nov 24, 2020

Abstract

Lithium tetrafluoro(malonato)phosphate compounds are useful as additives in lithium ion battery applications. The compounds are represented by Formula (I): MPF 4 [—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 —CR 2 —(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 LiPF 6 -containing electrolyte solution.

First claim

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A salt of Formula (I): MPF 4 [—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: —CR 2 —(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; wherein at least one of X′ and X″ is F.

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 alkyl.

4. The salt of claim 1 , wherein at least one of X′ and X″ is C 1 to C 4 alkyl.

5. The salt of claim 1 , wherein X′ is F and X″ is methyl.

6. 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): MPF 4 [—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: —CR 2 —(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; wherein at least one of X′ and X″ is F.

7. The electrolyte of claim 6 , wherein the lithium electrolyte salt comprises 1 to 2 M LiPF 6 .

8. The electrolyte of claim 6 , wherein the non-aqueous solvent comprises at least one organic carbonate solvent.

9. The electrolyte of claim 6 , wherein at least one of X′ and X″ is C 1 to C 4 alkyl.

10. The electrolyte of claim 6 , wherein X is F and X″ is methyl.

11. The electrolyte of claim 6 , 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 %.

12. The electrolyte of claim 6 , further comprising a silyl fluoride of formula FSiZ 3 wherein each Z independently is alkyl.

13. A lithium electrochemical cell comprising a cathode, an anode, a lithium-porous separator between the cathode and the anode, and an electrolyte of claim 6 contacting the cathode and the anode.

14. The electrochemical cell of claim 13 , wherein the cathode comprises a lithium nickel-manganese-cobalt oxide compound.

15. The electrochemical cell of claim 13 , wherein the anode comprises graphite.

16. The electrochemical cell of claim 13 , 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 LiPF 6 .

17. A battery comprising a plurality of the electrochemical cell of claim 13 electrically connected together.

18. A method of preparing the electrolyte of claim 6 in which the lithium salt is LiPF 6 , comprising the steps of adding a bis-silyl ester compound to an electrolyte comprising the LiPF 6 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): Z 3 Si—O(C═O)—(CX′X″)—(C═O)O—SiZ 3 ; 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: —CR 2 —(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.

19. The method of claim 18 , wherein byproduct FSiZ 3 that is formed by the reaction of the LiPF 6 with the compound of Formula (II) is retained in the electrolyte.

Assignees

• Uchicago Argonne Llc

Inventors

• Liao Chen
• Shkrob Ilya A
• Abraham Daniel
• Zhang Zhengcheng

Classifications

• H01M4/525

  of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy · CPC title

• H01M2300/0037

  Mixture of solvents · CPC title

• H01M4/505

  of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy · CPC title

• Y02E60/10

  Energy storage using batteries · CPC title

• H01M10/0567 Primary

  characterised by the additives · CPC title