NOVELTY - The device has a negative electrode (206b) including a set of protrusions (202b) protruding from a common portion (202a) of an active material (202), and an outer shell (203) contacting with and attached to a set of surfaces of the common portion and the protrusions. A graphene material (204) e.g. single-layer graphene material, is in contact with and attached to a surface of the outer shell, where a set of axes of the protrusions is oriented in a same direction. The common portion, the protrusions and the outer shell are made of silicon.    USE - Power storage device e.g. lithium-ion secondary battery such as coin-type lithium-ion secondary battery, for use as a main power supply, an uninterruptible power supply and an auxiliary power supply, of an electric device e.g. display device such as LCD device, light-emitting device, electrophoresis display device, digital micro-mirror device (DMD), plasma display panel (PDP) and field emission display (FED), for TV broadcast reception, installation lighting device such as ceiling installation lighting device, air conditioner, electric refrigerator-freezer and portable information terminal such as foldable tablet terminal. Can also be used for sealing-type lithium-ion secondary battery, cylindrical lithium-ion secondary battery and a square-type lithium-ion secondary battery, lithium-ion capacitor and air cell, for information display device for a personal computer e.g. desktop personal computer or laptop personal computer, advertisement display, wall installation lighting device, floor installation lighting device and window installation lighting device and tabletop lighting device, and for high-frequency heating apparatus e.g. microwave apparatus, electric rice cooker and electric washing machine, image reproduction device, mobile phone, portable game machine, electronic-book (e-book) reader, camera e.g. video camera and digital still camera, air-conditioning system e.g. electric refrigerator, electric freezer, freezer for preserving DNA and dialysis device, moving object e.g. electric vehicle, hybrid vehicle and motorized or motor-assisted bicycle.    ADVANTAGE - The axes of the protrusions are oriented in the same direction and the protrusions protrude in a direction perpendicular to the common portion, so that density of the protrusions in the electrode and a surface area of the active material can be efficiently increased. The graphene material covers the active material to suppress contact among the protrusions even when the active material expands in a charge reaction. The graphene material prevents the active material from being broken even when the active material is pulverized due to repeating of a charge/discharge reaction. The device multiple better output and cycle characteristics can be manufactured by using the electrode. The device has high charge capacity and discharge capacity and reduced deterioration in the battery characteristics caused by the charge/discharge reaction.    DETAILED DESCRIPTION - The protrusions have a shape selected from a group of columnar, conical or pyramidal, plate-like and pipe-like shapes.    DESCRIPTION OF DRAWING(S) - The drawing shows a cross-sectional view of a negative electrode.    Active material (202)    Common portion (202a)    Protrusions (202b)    Outer shell (203)    Graphene material (204)    Negative electrode (206b)