A material for slurry composition-use for example is a paste composition including a negative electrode active material that contains a silicon-based negative electrode active material in an amount of at least 30 mass % and a water-soluble polymer in an amount of at least 3 parts by mass and less than 500 parts by mass per 100 parts by mass of the silicon-based negative electrode active material. The water-soluble polymer includes at least 20.0 mass % and no greater than 79.5 mass % of structural units derived from an ethylenically unsaturated carboxylic acid compound (A) and at least 20.0 mass % and no greater than 79.5 mass % of structural units derived from a copolymerizable compound (B) that has an ethylenically unsaturated bond and a water solubility of at least 7 g/100 g at 20° C., and the water-soluble polymer has a degree of swelling in electrolysis solution of less than 120%.