Nonaqueous electrolyte secondary battery and method for producing same

A method for producing a nonaqueous electrolyte secondary battery, the method comprising:

• encapsulating a positive electrode comprising a positive electrode active material, a negative electrode comprising a negative electrode active material, and a nonaqueous electrolyte with an inclusion body such that at least a part of the positive electrode active material and at least a part of the negative electrode active material are immersed in the nonaqueous electrolyte,
• wherein the positive electrode active material has an average operating potential of from 3.0 V (vs. Li/Li+) to 4.5 V (vs. Li/Li+), inclusive, for deintercalation and intercalation of lithium ions, and comprises a spinel type lithium manganese oxide represented by Li1+xMyMn2−x−yO4, where 0≤x≤0.2, 0<y≤0.6, and M represents at least one element other than Mn selected from the group consisting of elements belonging to Groups 2 to 13 and Periods 3 and 4, or an olivine type manganese lithium phosphate represented by Li1+aMbMn1−a−bPO4, where 0≤a≤0.1, 0≤b≤0.3, and M represents at least one element other than Mn selected from the group consisting of elements belonging to Groups 2 to 13 and Periods 3 and 4,
• the positive electrode further comprises a compound having a cobalt content of 30% by weight or more such that
• a weight A of the compound having the cobalt content of 30% by weight or more and the total weight B of the positive electrode active material satisfy 0.01≤A/(A+B)≤0.15,
• the negative electrode active material has an average operating potential of 0.5 V (vs. Li/Li+) or more and less than 2.0 V (vs. Li/Li+) for deintercalation and intercalation of lithium ions, and
• the nonaqueous electrolyte comprises nonaqueous solvents consisting of propylene carbonate and diethyl carbonate such that a volume ratio of the propylene carbonate to the diethyl carbonate is from 1:1 to 1:19.