Abstract: The present invention provides a secondary battery electrode binder that exhibits superior binding capacity as compared to conventional binders and that also makes it possible to reduce electrode slurry viscosity, even when there is a high concentration of active material in an electrode mixture layer composition. The present invention also provides a secondary battery electrode mixture layer composition, a secondary battery electrode, and a secondary battery that are obtained using the binder. The present invention relates to a secondary battery electrode binder that contains a carboxyl-group-containing polymer or a salt of a carboxyl-group-containing polymer. The carboxyl-group-containing polymer or salt of a carboxyl-group-containing polymer includes structural units that are derived from monomers that are represented by general formula (1) and structural units that are derived from ethylenic unsaturated carboxylic acid monomers that are different from general formula (1).

Abstract: A binder is for a secondary battery electrode and exhibits high binding properties in an electrode mixture layer and is capable of exhibiting superior cycle characteristics than before. This binder for a secondary battery electrode includes a cross-linked polymer or salt thereof, and the cross-linked polymer or salt thereof has a sol fraction of 5.0 mass % or more and 40 mass % or less. The cross-linked polymer or salt thereof may contain 50 mass % or more and 100 mass % or less of structural units derived from an ethylenic unsaturated carboxylic acid monomer.