The present application provides a lithium ion battery and a negative electrode thereof. The negative electrode comprises: a negative electrode active material layer and an additive comprising a metal sulfide, wherein the additive is distributed in the negative electrode active material layer, distributed on the surface of the negative electrode active material layer, or both in the negative electrode active material layer and on the surface of the negative electrode active material layer. The negative electrode of the present application may effectively improve the performance of the lithium ion battery, and greatly improve the capacity and cycle performance of the lithium ion battery.