A solid polymer electrolyte comprising: (i) a lithium salt; and (ii) a polymer including a first repeating unit represented by the following Chemical Formula 1 and at least one of a second repeating unit represented by the following Chemical Formula 2a and a third repeating unit represented by the following Chemical Formula 2b: wherein, in Chemical Formula 1, R is hydrogen or an alkyl group having 1 to 3 carbon atoms; and a is an integer in the range of 1 to 800; in Chemical Formula 2a, R 1 is hydrogen or an alkyl group having 1 to 3 carbon atoms; R 2 and R 3 are each independently an alkylene group having 1 to 3 carbon atoms; b is an integer in the range of 1 to 800; and o is an integer in the range of 10 to 100; [Chemical Formula 2b] in Chemical Formula 2b, R 4 is hydrogen or an alkyl group having 1 to 3 carbon atoms; R 5 to R 9 are each independently an alkylene group having 1 to 3 carbon atoms; c is an integer in the range of 1 to 800; and o 1 to o 4 are each independently an integer in the range of 1 to 120. (i) a lithium salt; and (ii) a polymer including a first repeating unit represented by the following Chemical Formula 1 and at least one of a second repeating unit represented by the following Chemical Formula 2a and a third repeating unit represented by the following Chemical Formula 2b: wherein, in Chemical Formula 1, R is hydrogen or an alkyl group having 1 to 3 carbon atoms; and a is an integer in the range of 1 to 800; in Chemical Formula 2a, R 1 is hydrogen or an alkyl group having 1 to 3 carbon atoms; R 2 and R 3 are each independently an alkylene group having 1 to 3 carbon atoms; b is an integer in the range of 1 to 800; and o is an integer in the range of 10 to 100; [Chemical Formula 2b] in Chemical Formula 2b, R 4 is hydrogen or an alkyl group having 1 to 3 carbon atoms; R 5 to R 9 are each independently an alkylene group having 1 to 3 carbon atoms; c is an integer in the range of 1 to 800; and o 1 to o 4 are each independently an integer in the range of 1 to 120. R is hydrogen or an alkyl group having 1 to 3 carbon atoms; and a is an integer in the range of 1 to 800; in Chemical Formula 2a, R 1 is hydrogen or an alkyl group having 1 to 3 carbon atoms; R 2 and R 3 are each independently an alkylene group having 1 to 3 carbon atoms; b is an integer in the range of 1 to 800; and o is an integer in the range of 10 to 100; [Chemical Formula 2b] in Chemical Formula 2b, R 4 is hydrogen or an alkyl group having 1 to 3 carbon atoms; R 5 to R 9 are each independently an alkylene group having 1 to 3 carbon atoms; c is an integer in the range of 1 to 800; and o 1 to o 4 are each independently an integer in the range of 1 to 120. R 1 is hydrogen or an alkyl group having 1 to 3 carbon atoms; R 2 and R 3 are each independently an alkylene group having 1 to 3 carbon atoms; b is an integer in the range of 1 to 800; and o is an integer in the range of 10 to 100; [Chemical Formula 2b] in Chemical Formula 2b, R 4 is hydrogen or an alkyl group having 1 to 3 carbon atoms; R 5 to R 9 are each independently an alkylene group having 1 to 3 carbon atoms; c is an integer in the range of 1 to 800; and o 1 to o 4 are each independently an integer in the range of 1 to 120. R 4 is hydrogen or an alkyl group having 1 to 3 carbon atoms; R 5 to R 9 are each independently an alkylene group having 1 to 3 carbon atoms; c is an integer in the range of 1 to 800; and o 1 to o 4 are each independently an integer in the range of 1 to 120. <EOS>