NOVELTY - A power storage device (135) comprises positive electrode (117) including positive-electrode current collector (111), first projections on positive collector, and first insulator on end of first projections of positive-electrode active material (112); a negative electrode (127) including negative-electrode current collector, second projections on negative collector, and second insulator on end of second projections of negative-electrode active material; a separator between positive and negative electrodes; and an electrolyte provided in space between positive and negative electrodes.    USE - As a power storage device (claimed) such as lithium-ion secondary batteries.    ADVANTAGE - The surface of each of the positive-electrode active material and the negative-electrode active material is provided with the several projections, where the surface area is increased and a thin, small-sized power storage device with high capacity is obtained. As an insulator is provided on each of several projections, even when pressure is applied between the positive electrode and the negative electrode, the insulator absorbs or disperses the pressure so as to prevent breaking of the separator. Accordingly, a highly reliable power storage device is obtained.    DETAILED DESCRIPTION - A power storage device comprises a positive electrode including a positive-electrode current collector, a several first projections on the positive-electrode current collector, where the several first projections comprises a positive-electrode active material, and a first insulator on an end of each of the several first projections of the positive-electrode active material; a negative electrode including a negative-electrode current collector, a several second projections on the negative-electrode current collector, where the several second projections comprises a negative-electrode active material, and a second insulator on an end of each of the several second projections of the negative-electrode active material; a separator between the positive electrode and the negative electrode, where the several first projections and the several second projections facing each other with the separator interposed between them; and an electrolyte provided in a space between the positive electrode and the negative electrode, where the electrolyte contains carrier ions. An INDEPENDENT CLAIM is included for manufacturing a power storage device involving forming a plate-like positive-electrode active material on a positive-electrode current collector; forming several first insulators on the plate-like positive-electrode active material; etching the plate-like positive-electrode active material using several first insulators as masks, thereby forming a positive electrode having a positive-electrode active material with several first projections, where each of the several first insulators is provided on an end of each of the several first projections; forming a plate-like negative-electrode active material on a negative-electrode current collector; forming several second insulators on the plate-like negative-electrode active material; etching the plate-like negative-electrode active material using the several second insulators as masks, thereby forming a negative electrode having a negative-electrode active material with several second projections, where each of the several second insulators is provided on an end of each of the several second projections; providing a separator between the positive electrode and the negative electrode; and providing an electrolyte in a space between the positive electrode and the negative electrode, where the electrolyte contains carrier ions.    DESCRIPTION OF DRAWING(S) - The figure shows a cross-sectional view of a power storage device.    Positive-electrode current collector (111)    Positive-electrode active material (112)    Insulators (113,123)    Positive electrode (117)    Negative-electrode current collector (121)    Negative-electrode active material (122)    Negative electrode (127)    Separator (131)    Electrolyte (132)    Power storage device (135)