NONAQUEOUS ELECTROLYTE AND NONAQUEOUS ELECTROLYTE SECONDARY BATTERY USING SAME

1 . A non-aqueous electrolyte comprising a non-aqueous solvent, a solute dissolved in the non-aqueous solvent, and an additive,

the non-aqueous solvent including ethylene carbonate and propylene carbonate,

a content W EC of the ethylene carbonate in the non-aqueous solvent being 5 to 20 mass %,

a content W PC of the propylene carbonate in the non-aqueous solvent being 40 to 60 mass %, and

the additive comprising a sultone compound which includes a fluorine atom.

2 . The non-aqueous electrolyte in accordance with claim 1 , wherein the sultone compound is a compound represented by the following formula (A):

where R 1a to R 6a are independently a fluorine atom, a hydrogen atom, or a hydrocarbon group that may have a fluorine atom; R 2a and R 3a may be taken together to form a double bond; n is a number of repetitions for a methylene group having R 5a and R 6a , and is an integer of 1 to 3; when n is 2 or 3, R 5a and R 6a in the methylene groups may be the same respectively or be different from each other; and at least one of R 1a to R 6a is a fluorine atom, or a hydrocarbon group having at least one fluorine atom.

3 . The non-aqueous electrolyte in accordance with claim 1 , wherein the sultone compound is at least one selected from the group consisting of:

a compound represented by the following formula (1):

where R 1 to R 6 are independently a fluorine atom, a hydrogen atom, or a hydrocarbon group that may have a fluorine atom; and at least one of R 1 to R 6 is a fluorine atom or a hydrocarbon group having at least one fluorine atom;

a compound represented by the following formula (2):

where R 7 to R 14 are independently a fluorine atom, a hydrogen atom, or a hydrocarbon group that may have a fluorine atom; and at least one of R 7 to R 14 is a fluorine atom or a hydrocarbon group having at least one fluorine atom; and

a compound represented by the following formula (3):

where R 15 to R 24 are independently a fluorine atom, a hydrogen atom, or a hydrocarbon group that may have a fluorine atom; and at least one of R 15 to R 24 is a fluorine atom or a hydrocarbon group having at least one fluorine atom.

4 . The non-aqueous electrolyte in accordance with claim 1 , wherein the sultone compound is represented by the following formula (1a):

5 . The non-aqueous electrolyte in accordance with claim 1 , wherein the sultone compound is at least one selected from the group consisting of:

a compound represented by the following formula (4):

where R 25 to R 28 are independently a fluorine atom, a hydrogen atom, or a hydrocarbon group that may have a fluorine atom; and at least one of R 25 to R 28 is a fluorine atom or a hydrocarbon group having at least one fluorine atom;

a compound represented by the following formula (5):

where R 29 to R 34 are independently a fluorine atom, a hydrogen atom, or a hydrocarbon group that may have a fluorine atom; and at least one of R 29 to R 34 is a fluorine atom or a hydrocarbon group having at least one fluorine atom; and

a compound represented by the following formula (6):

where R 35 to R 42 are independently a fluorine atom, a hydrogen atom, or a hydrocarbon group that may have a fluorine atom; and at least one of R 35 to R 42 is a fluorine atom or a hydrocarbon group having at least one fluorine atom.

6 . The non-aqueous electrolyte in accordance with claim 1 , wherein the sultone compound is a compound represented by the following formula (4a):

7 . The non-aqueous electrolyte in accordance with claim 1 , wherein a content W s of the sultone compound in the non-aqueous electrolyte is 0.1 to 5 mass %.

8 . A non-aqueous electrolyte secondary battery comprising:

a positive electrode including a positive electrode current collector, and a positive electrode mixture layer formed on a surface of the positive electrode current collector and including a positive electrode active material;

a negative electrode including a negative electrode current collector, and a negative electrode active material layer formed on a surface of the negative electrode current collector and including a negative electrode active material;

a separator interposed between the positive electrode and the negative electrode; and

the non-aqueous electrolyte in accordance with claim 1 .

9 . The non-aqueous electrolyte secondary battery in accordance with claim 8 , wherein the negative electrode active material includes graphite particles.

10 . The non-aqueous electrolyte secondary battery in accordance with claim 9 , wherein a weight of the graphite particles included in 1 cm 3 of the negative electrode active material layer is 1.3 to 1.8 g.

11 . The non-aqueous electrolyte secondary battery in accordance with claim 9 , wherein the graphite particles are coated with at least one selected from the group consisting of a cellulose derivative and polyacrylic acid.

12 . The non-aqueous electrolyte secondary battery in accordance with claim 8 , wherein a film derived from the sultone compound is formed on a surface of the negative electrode active material layer.

13 . The non-aqueous electrolyte secondary battery in accordance with claim 8 , wherein the positive electrode active material includes a lithium-nickel-containing composite oxide represented by Li x Ni y M z Me 1−(y+z) O 2+d , where M is at least one element selected from the group consisting of Co and Mn; Me is at least one element selected from the group consisting of Al, Cr, Fe, Mg, and Zn;

0.98 ≦x≦ 1.1; 0.3 ≦y≦ 1; 0 ≦z≦ 0.7; 0.9 ≦y+z≦ 1; and

−0.01 ≦d≦ 0.01.