Abstract: A method of the present invention for manufacturing a lithium-ion cell comprises the step of impregnating a porous positive-electrode active material layer or a porous negative-electrode active material layer with an ionic liquid electrolyte. The ionic liquid electrolyte includes: an ionic liquid comprising an anion and a cation; and a lithium salt dissolved in the ionic liquid. The anion is bis(fluorosulfonyl)imide ion. The lithium salt is lithium bis(fluorosulfonyl)imide or lithium bis(trifluoromethansulfonyl)imide. The ionic liquid electrolyte contains the lithium salt at a concentration of 1.6 mol/L to 3.2 mol/L inclusive. The step of impregnation with the ionic liquid electrolyte is the step of impregnating the positive-electrode active material layer or the negative-electrode active material layer with the ionic liquid electrolyte at a temperature of 50° C. to 100° C. inclusive.