Lithium secondary battery

A lithium secondary battery comprising:

• a positive electrode;
• a negative electrode;
• and
• a sulfide solid electrolyte disposed between the positive electrode and the negative electrode,
• wherein the sulfide solid electrolyte comprises lithium sulfide and phosphorus pentasulfide,
• wherein the positive electrode comprises a positive active material particle and a coating film on a surface of the positive active material particle,
• wherein the coating film comprises a composite having a structure represented by Formula 1,
• aLi2O—ZrO2 Formula 1
• wherein 0.1≤a≤2.0,
• wherein an amount of the composite is in a range of 0.1 to 2.0 mole percent, based on a total amount of the positive active material particle and the composite,
• wherein the positive active material particle has a layered rock salt structure,
• wherein the positive active material particle has a D50 particle diameter of 10 micrometers or less, and
• wherein the positive active material particle is
• LiNixCoyAlzO2, wherein 0<x<1, 0<y<1, 0<z≤0.33, and x+y+z=1
• LiNixCoyMnzO2 wherein 0<x<1, 0<y<1, 0<z≤0.33, and x+y+z=1, or
• a combination thereof.