BINDER COMPOSITION FOR ELECTROCHEMICAL DEVICE ELECTRODE, COMPOSITION FOR ELECTROCHEMICAL DEVICE ELECTRODE, ELECTRODE FOR ELECTROCHEMICAL DEVICE, AND ELECTROCHEMICAL DEVICE

A binder composition contains a water-soluble polymer and water. The water-soluble polymer includes a nitrile group-containing monomer unit and an ethylenically unsaturated carboxylic acid monomer unit, and has a weight-average molecular weight of not less than 1,000 and not more than 50,000.