Nonaqueous electrolytic solution and energy storage device using same

1. A nonaqueous electrolytic solution, comprising:

an electrolyte salt; and

a nonaqueous solvent,

wherein the nonaqueous electrolytic solution is prepared by dissolving the electrolyte salt in the nonaqueous solvent,

the nonaqueous solvent comprises 0.01 to 40% by volume of an ester having two alkyl groups at an α-position carbon of a carbonyl group, and

the ester is methyl 2-ethyl-3-methyl butyrate, ethyl 2-ethyl-3-methyl butyrate, 2-propenyl 2-ethyl-3-methyl butyrate, methyl 2-ethyl valerate, ethyl 2-ethyl valerate, propyl 2-ethyl valerate, butyl 2-ethyl valerate, 2-propynyl 2-ethyl valerate, methyl 2-propyl valerate, ethyl 2-propyl valerate, 2-propynyl 2-propyl valerate, methyl 2-ethyl hexanoate, ethyl 2-ethyl hexanoate, propyl 2-ethyl hexanoate, butyl 2-ethyl hexanoate, 2-propynyl 2-ethyl hexanoate, methyl di-iso-propyl acetate, ethyl di-iso-propyl acetate, or 2-propynyl di-iso-propyl acetate.

2. A nonaqueous electrolytic solution, comprising:

an electrolyte salt; and

a nonaqueous solvent,

wherein the nonaqueous electrolytic solution is prepared by dissolving the electrolyte salt in the nonaqueous solvent,

the nonaqueous solvent comprises 0.01 to 40% by volume of an ester having two alkyl groups at an α-position carbon of a carbonyl group, and

the ester is represented by formula (I):

wherein R 1 is a C 1 to C 6 alkyl group, a C 2 to C 6 alkenyl group, or a C 2 to C 6 alkynyl group in which at least one of hydrogen atoms is optionally substituted with a halogen atom,

R 2 and R 3 are a C 1 to C 6 alkyl group in which at least one of hydrogen atoms is optionally substituted with a halogen atom, and R 2 and R 3 are optionally linked to each other to form a ring, and

when R 2 and R 3 do not form a ring, R 3 is a C 2 to C 6 alkyl group in which at least one hydrogen atom is optionally substituted with a halogen atom,

wherein the nonaqueous solvent further comprises a tertiary carboxylic acid ester and a chain carbonate, and

a content of the tertiary carboxylic acid ester is greater than a content of the chain carbonate.

3. An energy storage device, comprising:

a positive electrode;

a negative electrode; and

the nonaqueous electrolytic solution of claim 1 .

4. A nonaqueous electrolytic solution, comprising:

an electrolyte salt; and

a nonaqueous solvent,

wherein the nonaqueous electrolytic solution is prepared by dissolving the electrolyte salt in the nonaqueous solvent,

the nonaqueous solvent comprises 0.01 to 40% by volume of an ester having two alkyl groups at an α-position carbon of a carbonyl group, and

the ester is represented by formula (I):

wherein R 1 is a C 1 to C 6 alkyl group, a C 2 to C 6 alkenyl group, or a C 2 to C 6 alkynyl group in which at least one of hydrogen atoms is optionally substituted with a halogen atom,

R 2 and R 3 are a C 1 to C 6 alkyl group in which at least one of hydrogen atoms is optionally substituted with a halogen atom, and R 2 and R 3 are optionally linked to each other to form a ring,

when R 2 and R 3 do not form a ring, R 3 is a C 2 to C 6 alkyl group in which at least one hydrogen atom is optionally substituted with a halogen atom, and

wherein the ring is a 3- to 9-membered ring when R 2 and R 3 form the ring, and

a total carbon number of R 2 and R 3 is 4 to 8 when R 2 and R 3 do not form the ring,

wherein the nonaqueous solvent further comprises a tertiary carboxylic acid ester and a chain carbonate, and

a content of the tertiary carboxylic acid ester is greater than a content of the chain carbonate.

5. The energy storage device of claim 3 ,

wherein the positive electrode comprises a complex metal oxide with lithium, which comprises at least one selected from the group consisting of cobalt, manganese, and nickel, as a positive electrode-active material.

6. The energy storage device of claim 3 ,

wherein the negative electrode comprises at least one selected from the group consisting of a lithium metal, a lithium alloy, a carbon material which is capable of absorbing and releasing lithium, tin, a tin compound, silicon, a silicon compound, and a lithium titanate compound as a negative electrode-active material.

7. The nonaqueous electrolytic solution of claim 1 , wherein the nonaqueous solvent further comprises a pivalic acid ester.

8. The nonaqueous electrolytic solution of claim 2 , wherein a volume ratio of the cyclic carbonate to the chain ester is 10:90 to 45:55.

9. The nonaqueous electrolytic solution of claim 2 , wherein a volume ratio of the cyclic carbonate to the chain ester is 20:80 to 35:65.

10. The nonaqueous electrolytic solution of claim 9 , wherein the tertiary carboxylic acid ester is a pivalic acid ester.

11. The nonaqueous electrolytic solution of claim 10 , wherein the chain carbonate is dimethyl carbonate or diethyl carbonate.

12. The nonaqueous electrolytic solution of claim 4 , wherein the tertiary carboxylic acid ester is a pivalic acid ester.

13. The nonaqueous electrolytic solution of claim 12 , wherein the ester comprises the pivalic acid ester at a volume ratio of from 51% by volume to 95% by volume.

14. The nonaqueous electrolytic solution of claim 12 , wherein the ester comprises the pivalic acid ester at a volume ratio of from 55% by volume to 85% by volume.

15. The nonaqueous electrolytic solution of claim 12 , wherein the chain carbonate is dimethyl carbonate or diethyl carbonate.