Electrical device

An electrical device which comprises a power generating element containing one or more unit cell layers,

• at least one of the one or more unit cell layers containing:
• a positive electrode in which a positive electrode active material layer containing a positive electrode active material is formed on a 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 a surface of a negative electrode current collector;
• and
• a separator,
• wherein in the at least one of the one or more unit cell layers, the electrical device satisfies formula (1):
• 0.91≤C/A<0.99 where the area of the negative electrode active material layer is A [m2] and the area of the positive electrode active material layer is C [m2],
• wherein the at least one unit cell layer has a unit cell layer satisfying the formula (1), and in the unit cell layer, the electrical device satisfies IC/IA≥0.40 where the irreversible capacity per unit area of the negative electrode active material layer of the unit cell layer is IA and the irreversible capacity per unit area of the positive electrode active material layer of the unit cell layer is IC,
• wherein the positive electrode active material contains a solid solution positive electrode active material that has as a basic structure a composition represented by the following formula (3):
• [Mathematical formula 2]
• Li1.5[NiaMnbCoc[Li]d]O2 (3),
• In the formula, z represents the number of oxygen atoms satisfying a valence, a+b+c+d=1.5, 0.1≤d≤0.4, and 1.1≤[a+b+c]≤1.4, and
• wherein the negative electrode active material layer contains a negative electrode active material represented by the following formula (4):
• [Mathematical formula (3)]
• α (Si material)+β (carbon material) (4),
• In the formula, the Si material is formed of one or more kinds selected from the group consisting of Si-containing alloys, α and β each represent % by weight of each component in the negative electrode active material layer, and 80≤α+β≤98, 3≤α≤40, and 40≤β≤95.