An electrical device comprising a power generating element 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 negative electrode active material is formed on a surface of a negative electrode current collector; and a separator impregnated with an electrolytic solution, wherein the negative electrode active material layer contains a negative electrode active material represented by the following formula : [Numerical formula 1] α Si material + β carbon material in the formula, the Si material is formed of one or more kinds selected from the group consisting of SiO x which is a mixture of amorphous SiO 2 particles and Si particles (x represents the number of oxygen atoms satisfying a valence of Si) and a Si-containing alloy, α and β each represent % by weight of each component in the negative electrode active material layer, 80 ≤ α + β ≤ 98, 3 ≤ α ≤ 40, and 40 ≤ β ≤ 95, the positive electrode active material layer contains a positive electrode active material represented by the following formula : [Numerical formula 2] e solid solution positive electrode active material in the formula, e represents % by weight of each component in the positive electrode active material layer, and 80 ≤ e ≤ 98, wherein the solid solution positive electrode active material has a composition represented by the following formula : [Numerical formula 3] Li 1.5 [Ni 0.45 Mn 0.85 [Li] 0.20 ]O 3 , and the electrolytic solution contains 1,5,2,4-dioxadithiane-2,2,4,4-tetraoxide and lithium difluorophosphate, wherein the concentration of 1,5,2,4-dioxadithiane-2,2,4,4-tetraoxide is from 0.5 to 2.5% by weight, and the concentration of lithium difluorophosphate is from 1.8 to 3.0% by weight in the electrolytic solution. 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 negative electrode active material is formed on a surface of a negative electrode current collector; and a separator impregnated with an electrolytic solution, wherein the negative electrode active material layer contains a negative electrode active material represented by the following formula : [Numerical formula 1] α Si material + β carbon material in the formula, the Si material is formed of one or more kinds selected from the group consisting of SiO x which is a mixture of amorphous SiO 2 particles and Si particles (x represents the number of oxygen atoms satisfying a valence of Si) and a Si-containing alloy, α and β each represent % by weight of each component in the negative electrode active material layer, 80 ≤ α + β ≤ 98, 3 ≤ α ≤ 40, and 40 ≤ β ≤ 95, the positive electrode active material layer contains a positive electrode active material represented by the following formula : [Numerical formula 2] e solid solution positive electrode active material in the formula, e represents % by weight of each component in the positive electrode active material layer, and 80 ≤ e ≤ 98, wherein the solid solution positive electrode active material has a composition represented by the following formula : [Numerical formula 3] Li 1.5 [Ni 0.45 Mn 0.85 [Li] 0.20 ]O 3 , and the electrolytic solution contains 1,5,2,4-dioxadithiane-2,2,4,4-tetraoxide and lithium difluorophosphate, wherein the concentration of 1,5,2,4-dioxadithiane-2,2,4,4-tetraoxide is from 0.5 to 2.5% by weight, and the concentration of lithium difluorophosphate is from 1.8 to 3.0% by weight in the electrolytic solution. <EOS>