Secondary battery electrolyte and secondary battery

Patent metadata

Field	Value
Publication number	US-10263286-B2
Application number	US-201414889718-A
Country	US
Kind code	B2
Filing date	May 9, 2014
Priority date	May 10, 2013
Publication date	Apr 16, 2019
Grant date	Apr 16, 2019

Abstract

The present invention relates to a secondary battery electrolyte, which contains a first fluorine-containing ether compound, a second fluorine-containing ether compound, and at least one selected from fluorine-containing phosphate ester compounds and sulfone compounds, wherein the fluorine substitution rate of the first fluorine-containing ether compound is lower than that of the second fluorine-containing ether compound, and the content of the first fluorine-containing ether compound is higher than that of the second fluorine-containing ether compound. According to the present invention, with respect to batteries operating at a high voltage, and batteries supposed to be used at a high temperature for a long period, there can be provided a lithium secondary battery suppressed in the decomposition reaction of the electrolyte and improved in the life characteristics.

First claim

The invention claimed is:

1. A secondary battery electrolyte, comprising:
a first fluorine-containing ether compound represented by formula (1);
a second fluorine-containing ether compound represented by formula (1); and
at least one fluorine-containing phosphate ester compound represented by formula (2)
wherein a fluorine substitution rate of the first fluorine-containing ether compound is lower than a fluorine substitution rate of the second fluorine-containing ether compound;
the fluorine substitution rate of the second fluorine-containing ether compound is higher than 80% and 95% or lower;
a content of the first fluorine-containing ether compound is higher than a content of the second fluorine-containing ether compound;
the content of the first fluorine-containing ether compound is 0.1 vol % or higher and 80 vol % or lower of the electrolyte; and
the content of the second fluorine-containing ether compound is 0.1 vol % or higher and 40 vol % or lower of the electrolyte, where
R 1 —O—R 2   (1)

wherein R 1 and R 2 are each independently alkyl group or fluorine-containing alkyl group, and at least one of R 1 and R 2 is fluorine-containing alkyl group; and
O═P(—O—R 1 ′)(—O—R 2 ′)(—O—R 3 ′)  (2)

wherein R 1 ′, R 2 ′ and R 3 ′ are each independently alkyl group or fluorine-containing alkyl group, and at least one of R 1 ′, R 2 ′ and R 3 ′ is fluorine-containing alkyl group.

2. The secondary battery electrolyte according to claim 1 , wherein sum totals of the numbers of carbon atoms of the fluorine-containing ether compounds represented by formula (1) are each 4 or more and 10 or less.

3. The secondary battery electrolyte according to claim 1 , wherein the first fluorine-containing ether compound has a fluorine substitution rate of 40% or higher and 80% or lower.

4. The secondary battery electrolyte according to claim 1 , wherein the fluorine-containing phosphate ester compound is at least one selected from tris(2,2,2-trifluoroethyl) phosphate, tris(2,2,3,3,3 pentafluoropropyl) phosphate and tris(1H,1H-heptafluorobutyl) phosphate.

5. The secondary battery electrolyte according to claim 1 , further comprising a cyclic carbonate in a range of 1 vol % or more and 50 vol % or less of the electrolyte.

6. The secondary battery electrolyte according to claim 1 , comprising a sulfone compound represented by formula (3):
R 1 ″—SO 2 —R 2 ″  (3)

wherein R 1 ″ and R 2 ″ are each independently substituted or unsubstituted alkyl group, and this compound may be a cyclic compound in which carbon atoms of R 1 ″ and R 2 ″ are bonded through a single bond or a double bond.

7. The secondary battery electrolyte according to claim 6 , wherein the total of contents of the fluorine-containing phosphate ester compound and the sulfone compound is 0.1 vol % or higher and 70 vol % or lower of the electrolyte.

8. The secondary battery electrolyte according to claim 6 , wherein the sulfone compound is at least one selected from sulfolane, dimethyl sulfone, ethyl methyl sulfone and diethyl sulfone.

9. A secondary battery comprising a positive electrode, a negative electrode, and an electrolyte comprising a supporting salt and a nonaqueous electrolytic solvent, wherein the electrolyte is a secondary battery electrolyte according to claim 1 .

10. The secondary battery according to claim 9 , wherein the positive electrode comprises a positive electrode active material intercalating and deintercalating Li at a potential of 4.5 V or higher with respect to lithium.

11. The secondary battery according to claim 10 , wherein the positive electrode active material comprises one or more lithium metal complex oxides represented by any of the following formulae (4), (5), (6) and (7):
Li a (M x Mn 2-x-y Y y )(O 4-w Z w )  (4)

wherein 0.4≤x≤1.2, 0≤y, x+y<2, 0≤a≤1.2, and 0≤w≤1; M is a transition metal element, and includes at least one selected from the group consisting of Co, Ni, Fe, Cr and Cu; Y is a metal element, and includes at least one selected from the group consisting of Li, B, Na, Al, Mg, Ti, Si, K and Ca; and Z is a halogen element, and includes at least one selected from the group consisting of F and Cl;
LiMPO 4   (5)

wherein M is a transition metal element, and includes at least one selected from Co and Ni;
Li(M 1-z Mn z )O 2   (6)

wherein 0.33≥z≥0.7; and M is a metal element, and includes at least one selected from Li, Co and Ni; and
Li(Li x M 1-x-z Mn z )O 2   (7)

wherein 0.1≤x<0.3, 0.33≥z≥0.7; and M is a metal element, and includes at least one selected from Co and Ni.

12. A method for manufacturing a secondary battery electrolyte, comprising a step of mixing, in an electrolyte,
a first fluorine-containing ether compound represented by formula (1);
a second fluorine-containing ether compound represented by formula (1); and
at least one selected from fluorine-containing phosphate ester compounds represented by formula (2)
wherein a fluorine substitution rate of the first fluorine-containing ether compound is lower than a fluorine substitution rate of the second fluorine-containing ether compound;
the fluorine substitution rate of the second fluorine-containing ether compound is higher than 80% and 95% or lower;
a content of the first fluorine-containing ether compound is higher than a content of the second fluorine-containing ether compound;
the content of the first fluorine-containing ether compound is 0.1 vol % or higher and 80 vol % or lower of the electrolyte; and
the content of the second fluorine-containing ether compound is 0.1 vol % or higher and 40 vol % or lower of the electrolyte.

13. The method for manufacturing a secondary battery electrolyte according to claim 12 , wherein the at least one fluorine-containing phosphate ester compounds comprises a sulfone compounds represented by a formula (3),
R 1 ″—SO 2 —R 2 ″  (3)

wherein R 1 ″ and R 2 ″ are each independently substituted or unsubstituted alkyl group, and this compound may be a cyclic compound in which carbon atoms of R 1 ″ and R 2 ″ are bonded through a single bond or a double bond.

14. The method for manufacturing a secondary battery electrolyte according to claim 13 , wherein the total of contents of the fluorine-containing phosphate ester compound and the sulfone compound is 0.1 vol % or higher and 70 vol % or lower of the electrolyte.

15. The method for manufacturing a secondary battery electrolyte according to claim 13 , wherein the sulfone compound is at least one selected from sulfolane, dimethyl sulfone, ethyl methyl sulfone and diethyl sulfone.

16. A method for manufacturing a secondary battery having a positive electrode, a negative electrode, an electrolyte and an outer package,
the method comprising a step of arranging the positive electrode and the negative electrode facing to each other, and sealing the arrangement together with the electrolyte in the outer package,
wherein the electrolyte is a secondary battery electrolyte manufactured by a manufacture method according to claim 12 .

Assignees

• Nec Corp

Inventors

• Noguchi Takehiro
• Katou Yuukou
• Sasaki Hideaki
• Takahashi Makiko
• Fujii Emiko

Classifications

• H01M10/058

  Construction or manufacture · CPC title

• H01M10/052

  Li-accumulators · CPC title

• H01M4/505

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

• H01M4/485

  of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy (H01M4/505, H01M4/525 take precedence) · CPC title

• H01M10/0569 Primary

  characterised by the solvents · CPC title