Method for manufacturing positive electrode active material, and secondary battery

A method for manufacturing a positive electrode active material for a lithium-ion battery, the method comprising steps of:

• forming a first mixture by mixing lithium fluoride (LiF) and magnesium fluoride (MgF2);
• pulverizing the first mixture to reduce a particle size of the first mixture, thereby yielding a pulverized first mixture;
• forming a second mixture by mixing a composite oxide containing lithium, a transition metal, and oxygen with the pulverized first mixture;
• and
• heating the second mixture at higher than or equal to 900° C. and for longer than or equal to 2 hours,
• wherein a molar ratio of the lithium fluoride (LiF) and the magnesium fluoride (MgF2) in the first mixture is LiF:MgF2=x:1 (0.1≤x≤0.5),
• wherein in the composite oxide, concentrations of elements other than the lithium, the transition metal, and the oxygen are less than or equal to 5,000 ppm wt when analysis is performed by a glow discharge mass spectroscopy, and
• wherein an atomic ratio of the transition metal (TM) in the composite oxide included in the second mixture to magnesium (MgMix1) included in the first mixture is TM:MgMix1=1:y (0.0005≤y≤0.03).

A method for manufacturing a positive electrode active material for a lithium-ion battery, the method comprising steps of:

• forming a first mixture by mixing lithium fluoride (LiF) and magnesium fluoride (MgF2);
• pulverizing the first mixture to reduce a particle size of the first mixture, thereby yielding a pulverized first mixture;
• forming a second mixture by mixing a composite oxide containing lithium, cobalt, nickel, manganese, aluminum, and oxygen with the pulverized first mixture;
• and
• heating the second mixture,
• wherein the heating is performed at any one of a first condition and a second condition,
• wherein the first condition is higher than or equal to 600° C. and lower than or equal to 950° C. and for longer than or equal to 3 hours,
• wherein the second condition is higher than or equal to 900° C. and for longer than or equal to 2 hours,
• wherein a molar ratio of the lithium fluoride (LiF) and the magnesium fluoride (MgF2) in the first mixture is LiF:MgF2=x:1 (0.1≤x≤0.5),
• wherein in the composite oxide, concentrations of elements other than the lithium, the cobalt, the nickel, the manganese, the aluminum, and the oxygen are less than or equal to 5,000 ppm wt when analysis is performed by a glow discharge mass spectroscopy, and
• wherein an atomic ratio of a transition metal (TM) in the composite oxide included in the second mixture to magnesium (MgMix1) included in the first mixture is TM:MgMix1=1:y (0.0005≤y≤0.03).