Lithium ion battery and preparation method thereof

The invention provides a lithium ion battery and a preparation method thereof, and relates to the technical field of lithium ion batteries. Specifically, the lithium ion battery mainly comprises a positive electrode, a negative electrode, electrolyte and a diaphragm, wherein the negative electrode comprises graphite, a silica material and a binder, and the binder comprises an acrylate compound; the electrolyte comprises a cyano compound. According to the invention, the short-circuit safety problem of the silicon-containing negative electrode is solved by adding the olefine acid ester binder, and the olefine acid ester binder has strong binding force on the expansion of the negative electrode, and can well inhibit the thickness increase of the negative electrode piece in the circulation process, thereby reducing the safety risk caused by the expansion of the negative electrode piece; meanwhile, a cyano additive is used in the electrolyte, so that the negative effect caused by an acrylate binder is solved, and