▎ 摘　　要

NOVELTY - The electrode comprises an active material comprising sodium, and graphene including layers. The active material has a band gap of greater than or equal to 3.0 eV. In the graphene, a ratio of oxygen measured by X-ray photoelectron spectroscopy (XPS) is greater than or equal to 3 atomic% and less than or equal to 15 atomic%. A particle diameter of the active material is greater than or equal to 50 nm and less than or equal to 500 nm. USE - The electrode is useful in a sodium-ion secondary battery of an electrical device (all claimed) that includes smartphones, display devices such as televisions and monitors, lighting devices, desktop personal computers and laptop personal computers, word processors, image reproduction devices, which reproduce still images and moving images stored in recording media such as DVDs, portable compact disc players, radio receivers, tape recorders, headphone stereos, stereos, table clocks, wall clocks, cordless phone handsets, transceivers, mobile phones, car phones, portable game machines, calculators, portable information terminals, electronic notebooks, electronic-book readers, electronic translators, audio input devices, video cameras, digital still cameras, toys, electric shavers, high-frequency heating appliances such as microwave ovens, electric rice cookers, electric washing machines, electric vacuum cleaners, water heaters, electric fans, hair dryers, air-conditioning systems such as air conditioners, humidifiers and dehumidifiers, dishwashers, dish dryers, clothes dryers, futon dryers, electric refrigerators, electric freezers, electric refrigerator freezers, freezers for preserving DNA, flashlights, electrical tools such as chain saws, smoke detectors, medical equipment such as dialyzers, industrial equipment such as guide lights, traffic lights, belt conveyors, elevators, escalators, industrial robots, power storage systems and power storage devices for leveling the amount of power supply and smart grid, and moving objects driven by electric motors using electric power from a power storage device, where the moving objects are electric vehicles (EV), hybrid electric vehicles (HEV), which include both an internal-combustion engine and a motor, plug-in hybrid electric vehicles (PHEV), tracked vehicles in which endless tracks are substituted for wheels of the vehicles, motorized bicycles including motor-assisted bicycles, motorcycles, electric wheelchairs, golf carts, boats, ships, submarines, helicopters, aircrafts, rockets, artificial satellites, space probes, planetary probes and spacecrafts. ADVANTAGE - The electrode improves capacity, energy density, cycle performance and charge-discharge characteristics of the battery, and has improved electric conductivity. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a sodium-ion secondary battery. DESCRIPTION OF DRAWING(S) - The diagram shows a schematic view of an electrode for a storage battery. Active material layer (102) Particulate active material (104) Graphene flake (105) Binder. (106)