Non-aqueous electrolyte solution and non-aqueous secondary battery

1. A non-aqueous secondary battery comprising a non-aqueous electrolyte solution, the non-aqueous electrolyte solution comprising acetonitrile, LiPF 6 as an inorganic lithium salt, and an organic lithium salt, wherein an anion of the organic lithium salt has a LUMO (lowest unoccupied molecular orbital) energy in a range of −2.00 to 4.35 eV, and a HOMO (highest occupied molecular orbital) energy in a range of −5.35 to −2.90 eV,

wherein the non-aqueous secondary battery comprises the non-aqueous electrolyte solution, a positive electrode, and a negative electrode, wherein the negative electrode comprises materials capable of doping lithium ions at a potential lower than 0.4 V vs. Li/Li + L

wherein the organic lithium salt and the inorganic lithium salt satisfy the condition represented by the following formula (1):

0.05≦X≦1  (1)

wherein X represents a molar ratio of the inorganic lithium salt to the organic lithium salt

and wherein the organic lithium salt is at least one selected from LiN(SO 2 CF 3 ) 2 , LiN(SO 2 C 2 F5) 2 , LiPF 5 (CF 3 ), LiBF 3 (CF 3 ), LiB(C 2 O 4 ) 2 , LiBF 2 (C 2 O 4 ), LiB(C 3 O 4 H 2 ) 2 and LiPF 4 (C 2 O4), and wherein the acetonitrile is present in an amount of 70 to 100 vol % based on the total amount of ingredients contained in the non-aqueous electrolyte solution, other than the organic lithium salt or inorganic lithium salt.

2. The non-aqueous secondary battery according to claim 1 , wherein the LUMO of the anion of the organic lithium salt is in a range of −1.00 to 2.70 eV, and the HOMO is in a range of −4.50 to −3.00 eV.

3. The non-aqueous secondary battery according to claim 1 , wherein the organic lithium salt is present in an amount of 0.1 to 30 mass % based on the total amount of the non-aqueous electrolyte solution.

4. The non-aqueous secondary battery according to claim 1 , wherein the acetonitrile is present in an amount of 70 to 100 vol % based on the total amount of ingredients contained in the non-aqueous electrolyte solution, other than the organic lithium salt.

5. The non-aqueous secondary battery according to claim 1 , wherein the inorganic lithium salt is present in an amount of 0.1 to 40 mass % based on the total amount of the non-aqueous electrolyte solution.

6. The non-aqueous electrolyte solution according to claim 1 , which further comprises a non-nitrile additive having a LUMO (lowest unoccupied molecular orbital) energy in the range of −3.00 to 0.90 eV.

7. The non-aqueous electrolyte solution according to claim 6 , wherein the non-nitrile additive having a LUMO (lowest unoccupied molecular orbital) energy in the range of −3.00 to 0.90 eV has a HOMO (highest occupied molecular orbital) energy in the range of −9.55 to −6.00 eV.

8. The non-aqueous electrolyte solution according to claim 6 , wherein the non-nitrile additive having a LUMO (lowest unoccupied molecular orbital) energy in the range of −3.00 to 0.90 eV has a HOMO (highest occupied molecular orbital) energy in the range of −8.50 to −7.25 eV.

9. The non-aqueous electrolyte solution according to claim 6 , wherein the content of the non-nitrile additive is 0.1 to 30 mass % based on the total amount of the non-aqueous electrolyte solution.

10. The non-aqueous electrolyte solution according to claim 6 , wherein the content of the non-nitrile additive is 0.1 to 10 mass % based on the total amount of the non-aqueous electrolyte solution.

11. The non-aqueous electrolyte solution according to claim 6 , which comprises two or more of the non-nitrile additives.

12. The non-aqueous electrolyte solution according to claim 6 , wherein the non-nitrile additives comprise one or more compounds selected from the group consisting of carbonates.

13. The non-aqueous electrolyte solution according to claim 12 , wherein the carbonates are cyclic carbonates.

14. The non-aqueous electrolyte solution according to claim 12 , wherein the carbonates are compounds having a carbon-carbon double bond.

15. The non-aqueous electrolyte solution according to claim 6 , wherein the non-nitrile additives comprise one or more compounds selected from the group consisting of compounds represented by the following general formula (2):

R 1 -A-R 2   (2)

wherein R 1 and R 2 each independently represent an alkyl group optionally substituted with an aryl group or a halogen atom or an aryl group optionally substituted with an alkyl group or a halogen atom, or R 1 and R 2 bind to each other, together with A, form a cyclic structure optionally having an unsaturated bond; and A represents a divalent group having a structure represented by any one of the following formulae (3) to (7):

16. The non-aqueous electrolyte solution according to claim 15 , wherein, in the formula (2), R 1 and R 2 each independently represent an alkyl group comprising 1 to 4 carbon atoms that is optionally substituted with a phenyl group or a halogen atom or a phenyl group optionally substituted with a halogen atom, or R 1 and R 2 bind to each other, together with A, to form a cyclic structure optionally having an unsaturated bond.

17. The non-aqueous electrolyte solution according to claim 15 , wherein the compounds represented by the formula (2) comprise one or more compounds selected from the group consisting of ethylene sulfite, propylene sulfite, butylene sulfite, pentene sulfite, sulfolane, 3-methyl sulfolane, 3-sulfolene, 1,3-propanesultone, 1,4-butanesultone, 1,3-propanediol sulfate, and tetramethylene sulfoxide.

18. The non-aqueous secondary battery according to claim 1 , wherein the organic lithium salt contains a boron atom.

19. The non-aqueous secondary battery according to claim 1 , wherein the organic lithium salt contains an organic ligand.

20. The non-aqueous secondary battery according to claim 1 , wherein the organic lithium salt is one or more selected from the group consisting of lithium bis(oxalato)borate and lithium difluoro(oxalato)borate.

21. The non-aqueous secondary battery according to claim 1 , which further comprises a dinitrile compound.

22. The non-aqueous secondary battery according to claim 21 , wherein the dinitrile compound comprises one or more compounds selected from the group consisting of compounds represented by the following general formula (8):

NC—(CR 3 R 4 ) 2a —CN  (8)

wherein R 3 and R 4 each independently represents a hydrogen atom or an alkyl group, and a represents an integer from 1 to 6.

23. The non-aqueous electrolyte solution according to claim 1 , which further comprises an ionic compound.

24. The non-aqueous electrolyte solution according to claim 23 , wherein the cation having a nitrogen atom is a pyridinium cation.

25. The non-aqueous electrolyte solution according to claim 23 , wherein an anion of the ionic compound is PF 6 − .

26. A method for producing the non-aqueous secondary battery according to claim 1 comprising initially charging up to a charge of 0.001 to 0.3 C to the battery.

27. The method for producing the non-aqueous secondary battery according to claim 26 , wherein the initial charge is carried out via a constant-voltage charge.

28. The non-aqueous secondary battery according to claim 1 , which further comprises a non-nitrile additive having a LUMO (lowest unoccupied molecular orbital) energy in a range of −3.00 to 0.90 eV.

29. The non-aqueous secondary battery according to claim 28 , wherein the non-nitrile additive has a HOMO (highest occupied molecular orbital) energy in a range of −8.50 to −7.25 eV.