BINDER FOR SECONDARY BATTERIES

The present invention provides a binder for a secondary battery having excellent binding force. A binder for a secondary battery comprising a polymer compound, wherein the polymer compound contains repeating units represented by formulae (1), (2), and (3):in formula (1), R1 is a hydrogen atom or a methyl group, and M is a hydrogen atom or an alkali metal atom; and in formula (3), R2 is a hydrogen atom or a methyl group; andwhen a total ratio of repeating units constituting the polymer compound is taken as 100 mol%, a total ratio of the repeating unit represented by formula (3) is 2 mol% or more and 20 mol% or less.