BINDER FOR A SECONDARY BATTERY ELECTRODE AND USE THEREOF

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.