Nonaqueous electrolyte for secondary battery and nonaqueous-electrolyte secondary battery employing the same

Abstract

An object is to provide a nonaqueous electrolyte and a nonaqueous-electrolyte secondary battery which have excellent discharge load characteristics and are excellent in high-temperature storability, cycle characteristics, high capacity, continuous-charge characteristics, storability, gas evolution inhibition during continuous charge, high-current-density charge/discharge characteristics, discharge load characteristics, etc. The object has been accomplished with a nonaqueous electrolyte which comprises: an acyclic carbonate having a halogen atom, a monofluorophosphate and/or a difluorophosphate; and further a compound having a specific chemical structure or specific properties.

1 . (canceled) 
     
     
         2 . A nonaqueous-electrolyte secondary battery comprising:
 a negative electrode and a positive electrode, which are capable of occluding/releasing ions; and   a nonaqueous electrolyte solution, comprising:   an electrolyte;   a nonaqueous solvent including an acyclic carbonate having a halogen atom; and   at least one compound selected from the group consisting of a monofluorophosphate and a difluorophosphate.   
     
     
         3 . The non-aqueous-electrolyte secondary battery of  claim 2  wherein a content of the acyclic carbonate having a halogen atom is from 0.001% to 100% by mass of the nonaqueous solvent. 
     
     
         4 . The non-aqueous-electrolyte secondary battery of  claim 2  wherein a content of the acyclic carbonate having a halogen atom is from 0.001% to 10% by mass of the nonaqueous solvent. 
     
     
         5 . The non-aqueous-electrolyte secondary battery of  claim 2  wherein a content of the at least one compound selected from the group consisting of a monofluorophosphate and a difluorophosphate is from 0.001 to 5% by mass of the nonaqueous electrolyte solution. 
     
     
         6 . The non-aqueous-electrolyte secondary battery of  claim 2  wherein a content of the at least one compound selected from the group consisting of a monofluorophosphate and a difluorophosphate is from 0.01 to 5% by mass of the nonaqueous electrolyte solution. 
     
     
         7 . The non-aqueous-electrolyte secondary battery of  claim 2  wherein the acyclic carbonate having a halogen atom comprises 2 hydrocarbon groups which each independently contains from 1 to 10 carbon atoms. 
     
     
         8 . The non-aqueous-electrolyte secondary battery of  claim 2  wherein the halogen atom of the acyclic carbonate having a halogen atom is selected from the group consisting of fluorine, chlorine, bromine, and iodine atoms. 
     
     
         9 . The non-aqueous-electrolyte secondary battery of  claim 2  wherein the molecular weight of the acyclic carbonate having a halogen atom is from 50 to 250. 
     
     
         10 . The non-aqueous-electrolyte secondary battery of  claim 2  wherein the acyclic carbonate having a halogen atom is at least one selected from the group consisting of fluoromethyl methyl carbonate, bis(fluoromethyl) carbonate, difluoromethyl methyl carbonate, 2,2-difluoroethyl methyl carbonate, ethyl 2,2-difluoroethyl carbonate, bis(2,2-difluoroethyl) carbonate, 2,2,2-trifluoroethyl methyl carbonate, ethyl 2,2,2-trifluoroethyl carbonate, and bis(2,2,2-trifluoroethyl) carbonate. 
     
     
         11 . The non-aqueous-electrolyte secondary battery of  claim 2  wherein the nonaqueous solvent further comprises a cyclic carbonate having a halogen atom, a cyclic carbonate not having a halogen atom or a cyclic carboxylic acid ester. 
     
     
         12 . The nonaqueous electrolyte secondary battery of  claim 2 , wherein the monofluorophosphate is present and is at least one selected from the group consisting of Li 2 PO 3 F, Na 2 PO 3 F, MgPO 3 F, CaPO 3 F, Al 2 (PO 3 F) 3 , Ga 2 (PO 3 F) 3 . 
     
     
         13 . The nonaqueous electrolyte secondary battery according to  claim 2 , wherein the monofluorophosphate is present and is Li 2 PO 3 F. 
     
     
         14 . The nonaqueous electrolyte secondary battery according to  claim 2 , wherein the difluorophosphate is present and is at least one selected from the group consisting of LiPO 2 F 2 , NaPO 2 F 7 , Mg(PO 2 F 2 ) 2 , Ca(PO 2 F 2 ) 2 , Al(PO 2 F 2 ) 3 , and Ga(PO 2 F 2 ) 3 . 
     
     
         15 . The nonaqueous electrolyte secondary battery according to  claim 2 , wherein the difluorophosphate is present and is at least one selected from the group consisting of LiPO 2 F 2 , NaPO 2 F 2 , and Mg(PO 2 F 2 ) 2 . 
     
     
         16 . The nonaqueous electrolyte secondary battery according to  claim 2 , wherein the nonaqueous electrolyte solution further comprises a carbonate having an unsaturated bond. 
     
     
         17 . The nonaqueous electrolyte secondary battery according to  claim 16 , wherein the carbonate having an unsaturated bond is selected from the group consisting of vinylene carbonate, ethylene carbonate derivatives substituted with one or more aromatic rings or with one or more substituents having a carbon-carbon unsaturated bond, phenyl carbonates, vinyl carbonates, and allyl carbonates. 
     
     
         18 . The nonaqueous electrolyte secondary battery according to  claim 16 , wherein a content of the carbonate having an unsaturated bond is from 0.01% by mass to 70% by mass of the nonaqueous electrolyte solution. 
     
     
         19 . The nonaqueous-electrolyte secondary battery according to  claim 2 , wherein the ion occluded and released is a lithium ion. 
     
     
         20 . The nonaqueous-electrolyte secondary battery according to claim wherein the negative electrode includes a carbonaceous material. 
     
     
         21 . The nonaqueous-electrolyte secondary battery according to  claim 2 , wherein the negative electrode includes a negative-electrode active material having at least one kind of atom selected from the group consisting of a silicon atom, a tin atom, and a lead atom. 
     
     
         22 . A nonaqueous-electrolyte, comprising:
 an electrolyte;   a nonaqueous solvent including an acyclic carbonate having a halogen atom; and   at least one compound selected from the group consisting of a monofluorophosphate and a difluorophosphate.   
     
     
         23 . The non-aqueous-electrolyte of  claim 22  wherein a content of the acyclic carbonate having a halogen atom is from 0.001% to 100% by mass of the nonaqueous solvent. 
     
     
         24 . The non-aqueous-electrolyte of  claim 22  wherein a content of the acyclic carbonate having a halogen atom is from 0.001% to 10% by mass of the nonaqueous solvent. 
     
     
         25 . The non-aqueous-electrolyte of  claim 22  wherein a content of the at least one compound selected from the group consisting of a monofluorophosphate and a difluorophosphate is from 0.001 to 5% by mass of the nonaqueous electrolyte solution. 
     
     
         26 . The non-aqueous-electrolyte of  claim 22  wherein a content of the at least one compound selected from the group consisting of a monofluorophosphate and a difluorophosphate is from 0.01 to 5% by mass of the nonaqueous electrolyte solution. 
     
     
         27 . The non-aqueous-electrolyte of  claim 22  wherein the acyclic carbonate having a halogen atom comprises 2 hydrocarbon groups which each independently contains from 1 to 10 carbon atoms. 
     
     
         28 . The non-aqueous-electrolyte of  claim 22  wherein the halogen atom of the acyclic carbonate having a halogen atom is selected from the group consisting of fluorine, chlorine, bromine, and iodine atoms. 
     
     
         29 . The non-aqueous-electrolyte of  claim 22  wherein the molecular weight of the acyclic carbonate having a halogen atom is from 50 to 250. 
     
     
         30 . The non-aqueous-electrolyte of  claim 22  wherein the acyclic carbonate having a halogen atom is at least one selected from the group consisting of fluoromethyl methyl carbonate, bis(fluoromethyl) carbonate, difluoromethyl methyl carbonate, 2,2-difluoroethyl methyl carbonate, ethyl 2,2-difluoroethyl carbonate, bis(2,2-difluoroethyl) carbonate, 2,2,2-trifluoroethyl methyl carbonate, ethyl 2,2,2-trifluoroethyl carbonate, and bis(2,2,2-trifluoroethyl) carbonate. 
     
     
         31 . The non-aqueous-electrolyte of  claim 22  wherein the nonaqueous solvent further comprises a cyclic carbonate having a halogen atom, a cyclic carbonate not having a halogen atom or a cyclic carboxylic acid ester. 
     
     
         32 . The nonaqueous electrolyte of  claim 22 , wherein the monofluorophosphate is present and is at least one selected from the group consisting of Li 2 PO 3 F, Na 2 PO 3 F, MgPO 3 F, CaPO 3 F, Al 2 (PO 3 O 3 F) 3 , Ga 2 (PO 3 F) 3 . 
     
     
         33 . The nonaqueous electrolyte of  claim 22 , wherein the monofluorophosphate is present and is Li 2 PO 3 F. 
     
     
         34 . The nonaqueous electrolyte of  claim 22 , wherein the difluorophosphate is present and is at least one selected from the group consisting of LiPO 2 F 2 , NaPO 2 F 2 , Mg(PO 2 F 2 ) 2 , Ca(PO 2 F 2 ) 2 , Al(PO 2 F 2 ) 3 , and Ga(PO 2 F 2 ) 3 . 
     
     
         35 . The nonaqueous electrolyte of  claim 22 , wherein the difluorophosphate is present and is at least one selected from the group consisting of LiPO 2 F 2 , NaPO 2 F 2 , and Mg(PO 2 F 2 ) 2 . 
     
     
         36 . The nonaqueous electrolyte of  claim 22 , wherein the nonaqueous electrolyte solution further comprises a carbonate having an unsaturated bond. 
     
     
         37 . The nonaqueous electrolyte of  claim 36 , wherein the carbonate having an unsaturated bond is selected from the group consisting of vinylene carbonate, ethylene carbonate derivatives substituted with one or more aromatic rings or with one or more substituents having a carbon-carbon unsaturated bond, phenyl carbonates, vinyl carbonates, and allyl carbonates. 
     
     
         38 . The nonaqueous electrolyte of  claim 36 , wherein a content of the carbonate having an unsaturated bond is from 0.01% by mass to 70% by mass of the nonaqueous electrolyte solution.