An electrochemical device including a positive electrode, a negative electrode, and an electrolytic solution. The negative electrode includes a negative current collector and a negative active material layer formed on the negative current collector. The negative active material layer contains a negative active material. A conductive material is disposed between the negative active material layer and the negative current collector. An average particle diameter of the conductive material is smaller than that of the negative active material. The negative active material layer possesses a specific weight. The electrochemical device improves high-temperature cycle expansion performance and overcharge protection performance.