| abstract |
The present invention provides: a nonaqueous electrolyte solution for lithium secondary batteries or the like, which is able to be reduced in decrease of the discharge capacity over time; a positive electrode for lithium secondary batteries; a method for producing a positive electrode for lithium secondary batteries; and an electricity storage device such as a lithium secondary battery. Into this nonaqueous electrolyte solution, POF 2 n - or a salt thereof and PO 2 F 2 n - or a salt thereof or PO 3 F 2- or a salt thereof are added, or alternatively, a reaction product of a boroxine compound and lithium hexafluorophosphate is added. With respect to this positive electrode for lithium secondary batteries, the average oxidation numbers, in a non-charged state, of transition metals present in the surface layer of a composite oxide, namely the average oxidation number of Mn is higher than 4, the average oxidation number of Co is higher than 3, and the average oxidation number of Ni is higher than 2; and a boron-containing compound is present in the surface of the composite oxide. A lithium secondary battery (1) is provided with this nonaqueous electrolyte solution or this positive electrode for lithium secondary batteries. |