A carbon foam formed of carbon fibers, where, at 90% or more of any 20 locations, the carbon fibers have a fiber diameter that is within ±20% of an average fiber diameter.

Provided is an anode active material for energy storage devices capable of electrochemically inserting and extracting lithium ions and production method thereof, an electrode structure including the active material and flake graphite, and an energy storage device using the electrode structure as an anode. The anode active material includes secondary particles that are aggregates of 10-300 nm primary particles containing silicon as a main component. The primary particles each include, as a surface layer, a composite metal oxide layer containing at least one or more metal elements selected from at least Al, Zr, Mg, Ca, and La and Li.

Provided is an anode active material for energy storage devices capable of electrochemically inserting and extracting lithium ions and production method thereof, an electrode structure including the active material and flake graphite, and an energy storage device using the electrode structure as an anode. The anode active material includes secondary particles that are aggregates of 10-300 nm primary particles containing silicon as a main component. The primary particles each include, as a surface layer, a composite metal oxide layer containing at least one or more metal elements selected from at least Al, Zr, Mg, Ca, and La and Li.

A supercapacitor is provided. The supercapacitor includes an elastic fiber, an internal electrode, a first electrolyte layer, and an external electrode. The internal electrode, the first electrolyte layer, and the external electrode are sequentially wrapped on an outer surface of the elastic fiber. The internal electrode includes a first carbon nanotube film and a NiO@MnO.sub.x composite structure, and the external electrode includes a second carbon nanotube film and a Fe.sub.2O.sub.3 layer.

A supercapacitor is provided. The supercapacitor includes an elastic fiber, an internal electrode, a first electrolyte layer, and an external electrode. The internal electrode, the first electrolyte layer, and the external electrode are sequentially wrapped on an outer surface of the elastic fiber. The internal electrode includes a first carbon nanotube film and a NiO@MnO.sub.x composite structure, and the external electrode includes a second carbon nanotube film and a Fe.sub.2O.sub.3 layer.

Graphene electrodes-based supercapacitors are in demand due to superior electrochemical characteristics. However, commercial applications have been limited by inferior electrode cycle life. A method to fabricate highly efficient supercapacitor electrodes using pristine graphene sheets vertically-stacked and electrically connected to the carbon fibers which results in vertically-aligned graphene-carbon fiber nanostructure is disclosed. The vertically-aligned graphene-carbon fiber electrode prepared by electrophoretic deposition possesses a mesoporous three-dimensional architecture which enabled faster and efficient electrolyte-ion diffusion with a specific capacitance of 333.3 F g.sup.−1. The electrodes have electrochemical cycling stability of more than 100,000 cycles with 100% capacitance retention. Apart from the electrochemical double layer charge storage, the oxygen-containing surface moieties and α-Ni(OH).sub.2 present on the graphene sheets enhance the charge storage by faradaic reactions. This enables the assembled device to provide a gravimetric energy density of 76 W h kg.sup.−1 with a 100% capacitance retention even after 1,000 bending cycles.

An electrical storage device includes high surface area fibers (e.g., shaped fibers and/or microfibers) coated with carbon (graphite, expanded graphite, activated carbon, carbon black, carbon nanofibers, CNT, or graphite coated CNT), electrolyte, and/or electrode active material (e.g., lead oxide) in electrodes. The electrodes are used to form electrical storage devices such as electrochemical batteries, electrochemical double layer capacitors, and asymmetrical capacitors.

An electrical storage device includes high surface area fibers (e.g., shaped fibers and/or microfibers) coated with carbon (graphite, expanded graphite, activated carbon, carbon black, carbon nanofibers, CNT, or graphite coated CNT), electrolyte, and/or electrode active material (e.g., lead oxide) in electrodes. The electrodes are used to form electrical storage devices such as electrochemical batteries, electrochemical double layer capacitors, and asymmetrical capacitors.

There is provided an electrode material for electricity storage devices, which enables suppression of heat generation in charge and discharge at large currents. The electrode material for electricity storage devices comprises a first carbon material having a graphite structure wherein graphite is partially exfoliated, and a second carbon material different from the first carbon material, wherein the ratio A/B, where A represents a weight of the first carbon material and B represents a weight of the second carbon material, is within the range of 0.01 or higher and 100 or lower.

There is provided an electrode material for electricity storage devices, which enables suppression of heat generation in charge and discharge at large currents. The electrode material for electricity storage devices comprises a first carbon material having a graphite structure wherein graphite is partially exfoliated, and a second carbon material different from the first carbon material, wherein the ratio A/B, where A represents a weight of the first carbon material and B represents a weight of the second carbon material, is within the range of 0.01 or higher and 100 or lower.