A lithium secondary battery comprising: a positive electrode comprising a positive electrode active material layer; a negative electrode; a separator; and an electrolyte liquid; wherein the positive electrode active material layer comprises a sulfur-carbon composite comprising a carbon material surface-modified by heat treatment, wherein the content of carbon in the surface-modified carbon material is 98% by weight or greater, and the surface-modified carbon material has a specific surface area of 280 m 2 /g to 4500 m 2 /g and a pore volume of 2.3 cm 3 /g to 5 cm 3 /g, as determined by a BET method; 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 the porosity (%) of the positive electrode active material layer, wherein the porosity is measured according to the method of the description, L is the mass of sulfur per unit area (mg/cm 2) of the positive electrode active material layer in the positive electrode, and α is 10; and the electrolyte liquid comprises a solvent and a lithium salt, wherein 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 the dipole moment per unit volume (D·mol/L), μ is the viscosity of the solvent (cP, 25°C), and γ is 100, wherein the viscosity is measured according to the method of the description. a positive electrode comprising a positive electrode active material layer; a negative electrode; a separator; and an electrolyte liquid; wherein the positive electrode active material layer comprises a sulfur-carbon composite comprising a carbon material surface-modified by heat treatment, wherein the content of carbon in the surface-modified carbon material is 98% by weight or greater, and the surface-modified carbon material has a specific surface area of 280 m 2 /g to 4500 m 2 /g and a pore volume of 2.3 cm 3 /g to 5 cm 3 /g, as determined by a BET method; 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 the porosity (%) of the positive electrode active material layer, wherein the porosity is measured according to the method of the description, L is the mass of sulfur per unit area (mg/cm 2) of the positive electrode active material layer in the positive electrode, and α is 10; and the electrolyte liquid comprises a solvent and a lithium salt, wherein 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 the dipole moment per unit volume (D·mol/L), μ is the viscosity of the solvent (cP, 25°C), and γ is 100, wherein the viscosity is measured according to the method of the description. P is the porosity (%) of the positive electrode active material layer, wherein the porosity is measured according to the method of the description, L is the mass of sulfur per unit area (mg/cm 2) of the positive electrode active material layer in the positive electrode, and α is 10; and the electrolyte liquid comprises a solvent and a lithium salt, wherein 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 the dipole moment per unit volume (D·mol/L), μ is the viscosity of the solvent (cP, 25°C), and γ is 100, wherein the viscosity is measured according to the method of the description. DV is the dipole moment per unit volume (D·mol/L), μ is the viscosity of the solvent (cP, 25°C), and γ is 100, wherein the viscosity is measured according to the method of the description.