A non-aqueous electrolyte solution for a lithium secondary battery, the non-aqueous electrolyte solution comprising: an organic solvent, a first lithium salt that is LiPF 6, a second lithium salt excluding LiPF 6, a first additive that is an oligomer represented by Formula 1, and a second additive that is a mixed additive of lithium difluorophosphate (LiDFP), fluorobenzene, and tetravinylsilane: wherein, in Formula 1, R 1 is an alkylene group having 1 to 5 carbon atoms which is unsubstituted or substituted with fluorine, or -R 1 '-O-, wherein R 1 ' is an alkylene group having 1 to 5 carbon atoms which is unsubstituted or substituted with fluorine, R 2 is an alkylene group having 1 to 3 carbon atoms which is unsubstituted or substituted with fluorine, or -R 2 '-O-, wherein R 2 ' is an alkylene group having 1 to 3 carbon atoms which is unsubstituted or substituted with fluorine, R 3 is an alkylene group having 1 to 5 carbon atoms which is unsubstituted or substituted with fluorine, R 4 is an aliphatic hydrocarbon group or an aromatic hydrocarbon group, R a and R b are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms, o, p, q, and r are numbers of repeating units, o is an integer of 1 to 5, p is an integer of 1 to 10, r is an integer of 1 to 5, q is an integer of 1 to 15, and b and c are each independently an integer of 1 to 3. an organic solvent, a first lithium salt that is LiPF 6, a second lithium salt excluding LiPF 6, a first additive that is an oligomer represented by Formula 1, and a second additive that is a mixed additive of lithium difluorophosphate (LiDFP), fluorobenzene, and tetravinylsilane: wherein, in Formula 1, R 1 is an alkylene group having 1 to 5 carbon atoms which is unsubstituted or substituted with fluorine, or -R 1 '-O-, wherein R 1 ' is an alkylene group having 1 to 5 carbon atoms which is unsubstituted or substituted with fluorine, R 2 is an alkylene group having 1 to 3 carbon atoms which is unsubstituted or substituted with fluorine, or -R 2 '-O-, wherein R 2 ' is an alkylene group having 1 to 3 carbon atoms which is unsubstituted or substituted with fluorine, R 3 is an alkylene group having 1 to 5 carbon atoms which is unsubstituted or substituted with fluorine, R 4 is an aliphatic hydrocarbon group or an aromatic hydrocarbon group, R a and R b are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms, o, p, q, and r are numbers of repeating units, o is an integer of 1 to 5, p is an integer of 1 to 10, r is an integer of 1 to 5, q is an integer of 1 to 15, and b and c are each independently an integer of 1 to 3. R 1 is an alkylene group having 1 to 5 carbon atoms which is unsubstituted or substituted with fluorine, or -R 1 '-O-, wherein R 1 ' is an alkylene group having 1 to 5 carbon atoms which is unsubstituted or substituted with fluorine, R 2 is an alkylene group having 1 to 3 carbon atoms which is unsubstituted or substituted with fluorine, or -R 2 '-O-, wherein R 2 ' is an alkylene group having 1 to 3 carbon atoms which is unsubstituted or substituted with fluorine, R 3 is an alkylene group having 1 to 5 carbon atoms which is unsubstituted or substituted with fluorine, R 4 is an aliphatic hydrocarbon group or an aromatic hydrocarbon group, R a and R b are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms, o, p, q, and r are numbers of repeating units, o is an integer of 1 to 5, p is an integer of 1 to 10, r is an integer of 1 to 5, q is an integer of 1 to 15, and b and c are each independently an integer of 1 to 3.