Non-aqueous secondary battery comprising a polyvalent organic lithium salt

1. A non-aqueous secondary battery comprising a positive electrode containing a lithium-containing composite oxide as an active material, a negative electrode, a separator, and a non-aqueous electrolyte,

wherein the non-aqueous electrolyte contains polyvalent organic lithium salt,

the content of the polyvalent organic lithium salt is 0.001 parts by mass or more and 1 part by mass or less with respect to 100 parts by mass of all of components of the non-aqueous electrolyte other than the polyvalent organic lithium salt, and

the polyvalent organic lithium salt includes at least one selected from the group consisting of LiSO 3 —Rf′—SO 3 Li, LiCO 2 —Rf′—CO 2 Li, LiPF 5 —Rf′—PF 5 Li, and LiBF 3 —Rf′—BF 3 Li, where Rf′ is an organic chain whose hydrogen atoms are partially or entirely replaced with fluorine atoms.

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

3. The non-aqueous secondary battery according to claim 1 , wherein the lithium-containing composite oxide can be used in the battery to be charged at a voltage of 4.4V or higher against lithium.

4. The non-aqueous secondary battery according to claim 3 , wherein the lithium-containing composite oxide is represented by the general formula LiNi x M y Mn 2-x-y O 4 , where M is at least one metal element other than Ni, Mn and Li, x satisfies 0.4≦x≦0.6, and y satisfies 0≦y≦0.1.

5. The non-aqueous secondary battery according to claim 1 , wherein the non-aqueous electrolyte contains LiPF 6 or LiBF 4 as an electrolyte salt.

6. The non-aqueous secondary battery according to claim 5 , wherein the concentration of the electrolyte salt in the non-aqueous electrolyte is 0.3 mol/L or more and 1.7 mol/L or less.