Binder composition for negative electrode, slurry for negative electrode, negative electrode, and lithium ion secondary battery

A slurry for negative electrode comprising:

• a binder composition for negative electrode comprising a graft copolymer obtained by graft copolymerizing, with polyvinyl alcohol, a monomer containing (meth)acrylonitrile as a main component;
• a negative electrode active material;
• and
• a conductive assistant, wherein:
• the polyvinyl alcohol has an average degree of polymerization of 300 to 3000;
• the polyvinyl alcohol has a saponification degree of 70 to 100 mol %;
• the graft copolymer has a polyvinyl alcohol amount of 10 to 90 mass %;
• the graft copolymer has a poly(meth)acrylonitrile amount of 90 to 10 mass %;
• and
• a homopolymer of poly(meth)acrylonitrile generated during the graft copolymerization has a mass average molecular weight of 30000 to 250000.