A nonaqueous electrolyte secondary battery of the invention has a positive electrode having a positive electrode active material, a negative electrode, and a nonaqueous electrolyte having electrolyte salt in a nonaqueous solvent. The electric potential of the positive electrode active material is 4.4 to 4.6 V relative to lithium, and the nonaqueous electrolyte contains a compound expressed by structural formula (I) below. The quantity of compound added is preferably 0.1% to 2% by mass. Also, the positive electrode active material preferably comprises a mixture of a lithium-cobalt composite oxide which is LiCoO2 containing at least both zirconium and magnesium and a lithium-manganese-nickel composite oxide that has a layer structure and contains at least both manganese and nickel. Thanks to such structure, a nonaqueous electrolyte secondary battery can be provided that is charged to charging termination potential of 4.4 to 4.6 V relative to lithium and that has enhanced overcharging safety.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of a background art square nonaqueous electrolyte secondary battery, cut in the longitudinal direction.
Claims
1. A nonaqueous electrolyte secondary battery comprising:
a positive electrode that has a positive electrode active material;a negative electrode; anda nonaqueous electrolyte that has electrolyte salt in a nonaqueous solvent;the electric potential of said positive electrode active material being 4.4 to 4.6 V relative to lithium, andsaid nonaqueous electrolyte containing a compound given by structural formula (I) below.
2. The nonaqueous electrolyte secondary battery according to claim 1, wherein the content of said compound given by said structural formula (I) is 0.1% to 2% by mass of said nonaqueous electrolyte.
3. The nonaqueous electrolyte secondary battery according to claim 1, wherein said positive electrode active material comprises a mixture of a lithium-cobalt composite oxide which is LiCoO2 containing at least both zirconium and magnesium and a lithium-manganese-nickel composite oxide that has a layer structure and contains at least both manganese and nickel.
4. The nonaqueous electrolyte secondary battery according to claim 1, wherein said nonaqueous electrolyte further contains vinylene carbonate.
5. A method for charging a nonaqueous electrolyte secondary battery including:
a positive electrode having a positive electrode active material;a negative electrode; anda nonaqueous electrolyte with electrolyte salt contained in a nonaqueous solvent;said nonaqueous electrolyte containing as an additive a compound given by structural formula (I) below,said method comprising:
charging so that the electric potential of said positive electrode active material is 4.4 to 4.6 V relative to lithium.
6. The method for charging a nonaqueous electrolyte secondary battery according to claim 5, wherein the content of said compound given by said structural formula (I) is 0.1% to 2% by mass of said nonaqueous electrolyte.
7. The method for charging a nonaqueous electrolyte secondary battery according to claim 5, wherein said positive electrode active material comprises a mixture of a lithium-cobalt composite oxide which is LiCoO2 containing at least both zirconium and magnesium and a lithium-manganese-nickel composite oxide that has a layer structure and contains at least both manganese and nickel.
8. A nonaqueous electrolyte used in a nonaqueous electrolyte secondary battery, said nonaqueous electrolyte secondary battery including:
a positive electrode that has a positive electrode active material,a negative electrode, andsaid nonaqueous electrolyte that has electrolyte salt in a nonaqueous solvent,the electric potential of said positive electrode active material being 4.4 to 4.6 V relative to lithium:said nonaqueous electrolyte comprising:a compound given by structural formula (I) below.
9. The nonaqueous electrolyte according to claim 8, wherein the content of said compound given by said structural formula (I) is 0.1% to 2% by mass of said nonaqueous electrolyte.
10. The nonaqueous electrolyte according to claim 8, wherein said positive electrode active material comprises a mixture of a lithium-cobalt composite oxide which is LiCoO2 containing at least both zirconium and magnesium and a lithium-manganese-nickel composite oxide that has a layer structure and contains at least both manganese and nickel.
Patent Application
20070172730
