Provided are a thermally crosslinkable binder aqueous solution for a lithium-ion battery, a thermally crosslinkable slurry for a lithium-ion battery negative electrode, a negative electrode for a lithium-ion battery, and a lithium-ion battery. The thermally crosslinkable binder aqueous solution for a lithium-ion battery contains a water-soluble poly(meth)acrylamide (A) and a divalent or higher valent metal ion. The water-soluble poly(meth)acrylamide (A) contains 2 mol % to 60 mol % of a constituent unit derived from a (meth)acrylamide group-containing compound (a), and 10 mol % to 50 mol % of a constituent unit derived from one or more unsaturated acids selected from the group consisting of unsaturated carboxylic acids and unsaturated sulfonic acids or an inorganic salt thereof (b). The divalent or higher valent metal ion is contained in an amount of 0.5 mol % to 30 mol % with respect to 100 mol % of an acid group contained in the component (b).