BINDER COMPOSITION FOR ALL-SOLID-STATE SECONDARY BATTERY, SLURRY COMPOSITION FOR ALL-SOLID-STATE SECONDARY BATTERY, SOLID ELECTROLYTE-CONTAINING LAYER, AND ALL-SOLID-STATE SECONDARY BATTERY

Provided is a binder composition with which it is possible to produce a slurry composition having excellent dispersibility and to form a solid electrolyte-containing layer that can cause an all-solid-state secondary battery to display excellent cycle characteristics. The binder composition contains a polymer and an aromatic halide. The polymer includes a nitrile group-containing monomer unit in a proportion of 10 mass% to 35 mass% and a (meth)acrylic acid ester monomer unit in a proportion of 15 mass% to 40 mass%. The aromatic halide has a structure in which not less than 2 and not more than 4 halogen atoms are bonded directly to an aromatic ring, and the content of the aromatic halide in the binder composition is 5 mass ppm to 3,000 mass ppm relative to the content of the polymer.