An electrolyte which is for a lithium secondary battery, and comprises: a polymer; and one or more selected from the group consisting of an inorganic solid electrolyte particle and a ferrodielectric, wherein the polymer includes one or more selected from the group consisting of a polymer represented by Formula 1 below and a polymer including a repeating unit represented by Formula 2 below, wherein the weight average molecular weight of the polymer including a repeating unit represented by Formula 2 is 100,000 g/mol to 1,000,000 g/mol, wherein the weight average molecular weight is measured according to the description and wherein the repeating unit represented by Formula 2 is at least one selected from the group consisting of repeating units represented by Formulae 2a-1, 2a-2, 2a-3, 2b-1, 2b-2 and 2b-3 below: in Formula 1 above, R 1 , R 2 , and R 3 are each independently hydrogen or -CH 2 -CH=CH 2 , wherein at least one of the R 1 , R 2 , and R 3 is -CH 2 -CH=CH 2 and a, b, and c are each independently an integer of 1 to 10,000; in Formula 2 above, R a to R d are each independently an element selected from the group consisting of H, F, Cl, Br, and I, R e to R h are each independently one selected from the group consisting of H, F, Cl, Br, and *-OR 0 SO 3 - M + , and R 0 is an alkylene group having 1 to 5 carbon atoms in which at least one hydrogen is substituted with a halogen element, wherein the M + is one selected from the group consisting of H + , Li + , Na + , and K + , and at least one of the R e to R h is *-OR 0 SO 3 - M +- Li + , and m and n are each independently an integer of 1 to 10,000; in Formulae 2a-1, 2a-2 and 2a-3 above, m11 to m13 and n11 to n13 are each independently an integer of 1 to 10,000; in Formulae 2b-1, 2b-2 and 2b-3 above, m21 to m23 and n21 to n23 are each independently an integer of 1 to 10,000. a polymer; and one or more selected from the group consisting of an inorganic solid electrolyte particle and a ferrodielectric, wherein the polymer includes one or more selected from the group consisting of a polymer represented by Formula 1 below and a polymer including a repeating unit represented by Formula 2 below, wherein the weight average molecular weight of the polymer including a repeating unit represented by Formula 2 is 100,000 g/mol to 1,000,000 g/mol, wherein the weight average molecular weight is measured according to the description and wherein the repeating unit represented by Formula 2 is at least one selected from the group consisting of repeating units represented by Formulae 2a-1, 2a-2, 2a-3, 2b-1, 2b-2 and 2b-3 below: in Formula 1 above, R 1 , R 2 , and R 3 are each independently hydrogen or -CH 2 -CH=CH 2 , wherein at least one of the R 1 , R 2 , and R 3 is -CH 2 -CH=CH 2 and a, b, and c are each independently an integer of 1 to 10,000; in Formula 2 above, R a to R d are each independently an element selected from the group consisting of H, F, Cl, Br, and I, R e to R h are each independently one selected from the group consisting of H, F, Cl, Br, and *-OR 0 SO 3 - M + , and R 0 is an alkylene group having 1 to 5 carbon atoms in which at least one hydrogen is substituted with a halogen element, wherein the M + is one selected from the group consisting of H + , Li + , Na + , and K + , and at least one of the R e to R h is *-OR 0 SO 3 - M +- Li + , and m and n are each independently an integer of 1 to 10,000; in Formulae 2a-1, 2a-2 and 2a-3 above, m11 to m13 and n11 to n13 are each independently an integer of 1 to 10,000; in Formulae 2b-1, 2b-2 and 2b-3 above, m21 to m23 and n21 to n23 are each independently an integer of 1 to 10,000. <EOS>