The present invention relates to a binder for electricity storage devices containing a salt of a polymer containing structural units derived from (i) an ethylenically unsaturated carboxylic acid monomer and (ii) an ethylenically unsaturated monomer having at least one group selected from a hydroxy group, a dialkylamino group, an acetyl group, a sulfo group, a phosphate group, or a cyano group and neutralized with a monoamine, a polyvalent amine having an amine value of less than 21, and/or an onium hydroxide; a slurry composition and an electrode, each of which uses this binder; an electricity storage device which is provided with this electrode; and the like.