Mixture, sheet, electrochemical element, and power storage device

A mixture containing an oxide and an electrolytic solution, wherein

• the electrolytic solution is formed of an electrolytic salt dissolved in a sulfone compound represented by a chemical formula (1),
• in the chemical formular (1), each of R1 and R2 independently represents a C1-C4 alkyl group, a C1-C4 alkenyl group, or a C1-C4 halogenated alkyl group, or two of the alkyl group, alkenyl group, and halogenated alkyl group are bonded to each other to form a ring structure,
• wherein the self-diffusion coefficient of at least one component contained in the electrolytic solution in contact with the oxide, as measured through pulsed field gradient nuclear magnetic resonance spectroscopy, is equal to or greater than 6 times the self-diffusion coefficient of the component contained in the electrolytic solution which is not in contact with the oxide, measured by the pulsed field gradient nuclear magnetic resonance spectroscopy at the same temperature as that in measurement of the former self-diffusion coefficient, and
• wherein a ratio of a volume of the oxide to a sum of the volume of the oxide and a volume of the electrolytic solution is 61% or greater and equal to or less than 93%.