Material for Forming All-Solid-State Lithium Ion Secondary Battery Negative Electrode, and All-Solid-State Lithium Ion Secondary Battery

A negative electrode forming material for an all-solid-state lithium ion secondary battery includes: on a negative electrode current collector, a negative electrode active material layer, which is made of a negative electrode forming composition for an all-solid-state lithium ion secondary battery containing a silicon crystal having an average particle diameter of 0.5 μm to 5.0 μm, which includes island-shaped convex portions formed in a pattern shape at an interval, and in which a connection layer made of the negative electrode forming composition for an all-solid-state lithium ion secondary battery is formed continuously with the island-shaped convex portions on a bottom surface of a groove portion formed between the island-shaped convex portions. In a negative electrode obtained by using the negative electrode forming material, active materials fuse together after charge and discharge to form dense and uniformly shaped blocks.