Balanced chemical reaction: 2LiI(s) → 2Li(s) + I₂(g).
This reaction is decomposition. Lithium iodide (LiI) is broken down into simpler substances (lithium and iodine).
In lithium iodide, lithium has oxidation number +1 (lost one electron) and iodine has oxidation number -1 (gain one electron from lithium).