ELECTRICAL DEVICE

To provide a means for further improving cycle durability in an electrical device such as a lithium ion secondary battery including a negative electrode containing a silicon-containing negative electrode active material. An electrical device has a power generating element including a unit cell layer containing a positive electrode in which a positive electrode active material layer containing a positive electrode active material is formed on the surface of a positive electrode current collector, a negative electrode in which a negative electrode active material layer containing a silicon-containing negative electrode active material is formed on the surface of a negative electrode current collector, and a separator. The electrical device is configured such that the one or more unit cell layers constituting the power generating element satisfy formula (1) : 0.91 ¤ C/A < 1 when the area of the negative electrode active material layer is A [m 2 ] and the area of the positive electrode active material layer is C [m 2 ].