A lithium-sulfur secondary battery comprising: a positive electrode; a negative electrode; a separator; and an electrolyte liquid, wherein the positive electrode includes catalytic site-introduced sulfur; and the positive electrode has an SC factor value represented by the following Mathematical Formula 1 of 0.45 or greater: SC factor = α × L P in Mathematical Formula 1, P is porosity (%) of a positive electrode active material layer in the positive electrode; L is a mass of sulfur per unit area (mg/cm 2) of the positive electrode active material layer in the positive electrode; and α is 10; wherein the electrolyte liquid comprises a solvent and a lithium salt; and the solvent comprises a first solvent having a DV 2 factor value represented by the following Mathematical Formula 2 of 1.75 or less and a second solvent that is a fluorinated ether-based solvent: DV 2 factor = γ × μ DV in Mathematical Formula 2, DV is a dipole moment per unit volume (D·mol/L); μ is viscosity of the solvent (cP, 25°C); and γ is 100; wherein the second solvent is present in the solvent in an amount of 50% by weight to 99% by weight based on a total weight of the solvent; wherein the porosity of the positive electrode active material layer is calculated based on the measurements of electrode weight and electrode thickness using a TESA-μHITE device; wherein the viscosity of the solvent is measured using a LVDV2T-CP viscometer. a positive electrode; a negative electrode; a separator; and an electrolyte liquid, wherein the positive electrode includes catalytic site-introduced sulfur; and the positive electrode has an SC factor value represented by the following Mathematical Formula 1 of 0.45 or greater: SC factor = α × L P in Mathematical Formula 1, P is porosity (%) of a positive electrode active material layer in the positive electrode; L is a mass of sulfur per unit area (mg/cm 2) of the positive electrode active material layer in the positive electrode; and α is 10; wherein the electrolyte liquid comprises a solvent and a lithium salt; and the solvent comprises a first solvent having a DV 2 factor value represented by the following Mathematical Formula 2 of 1.75 or less and a second solvent that is a fluorinated ether-based solvent: DV 2 factor = γ × μ DV in Mathematical Formula 2, DV is a dipole moment per unit volume (D·mol/L); μ is viscosity of the solvent (cP, 25°C); and γ is 100; wherein the second solvent is present in the solvent in an amount of 50% by weight to 99% by weight based on a total weight of the solvent; wherein the porosity of the positive electrode active material layer is calculated based on the measurements of electrode weight and electrode thickness using a TESA-μHITE device; wherein the viscosity of the solvent is measured using a LVDV2T-CP viscometer. P is porosity (%) of a positive electrode active material layer in the positive electrode; L is a mass of sulfur per unit area (mg/cm 2) of the positive electrode active material layer in the positive electrode; and α is 10; wherein the electrolyte liquid comprises a solvent and a lithium salt; and the solvent comprises a first solvent having a DV 2 factor value represented by the following Mathematical Formula 2 of 1.75 or less and a second solvent that is a fluorinated ether-based solvent: DV 2 factor = γ × μ DV in Mathematical Formula 2, DV is a dipole moment per unit volume (D·mol/L); μ is viscosity of the solvent (cP, 25°C); and γ is 100; wherein the second solvent is present in the solvent in an amount of 50% by weight to 99% by weight based on a total weight of the solvent; wherein the porosity of the positive electrode active material layer is calculated based on the measurements of electrode weight and electrode thickness using a TESA-μHITE device; wherein the viscosity of the solvent is measured using a LVDV2T-CP viscometer. DV is a dipole moment per unit volume (D·mol/L); μ is viscosity of the solvent (cP, 25°C); and γ is 100; wherein the second solvent is present in the solvent in an amount of 50% by weight to 99% by weight based on a total weight of the solvent; wherein the porosity of the positive electrode active material layer is calculated based on the measurements of electrode weight and electrode thickness using a TESA-μHITE device; wherein the viscosity of the solvent is measured using a LVDV2T-CP viscometer.