A composite particle for an electrochemical device contains an electrode active material, a conductive material, a binder, and 0.1 parts by mass or more and 5 parts by mass or less of a thermally decomposable foaming agent per 100 parts by mass of the composite particle. When a cross section of the composite particle perpendicular to the long axis of the composite particle, and including the midpoint of the long axis is subjected to a map analysis using an electron beam microanalyzer, the value of the ratio of the integrated values of the detection intensities of carbon atoms contained outside and inside the range of the circle the center of which is coincides with the midpoint of the long axis and the diameter of which is one half of the length of the long axis is 4 or more and 15 or less.

Formation process for a potassium-ion hybrid supercapacitor, the process comprising: a) supplying the potassium-ion hybrid supercapacitor comprising: a negative electrode comprising graphite, a positive electrode comprising activated carbon, an electrolyte comprising a potassium salt, b) charging the supercapacitor at constant current in a protocol of between C.sub.x/50 and C.sub.x/2, to a charge cutoff voltage of between 3.0 V and 3.3 V, c) holding the supercapacitor at the charge cutoff voltage until the leakage current is between C.sub.x/2000 and C.sub.x/500, d) discharging the supercapacitor at constant current in a protocol of between C.sub.x/50 and C.sub.x, to a discharge cutoff voltage of between 0 V and 2 V,
where the process further comprises degassing the supercapacitor after one of steps b) to d).

A method for treating a carbonaceous biochar electrode with an applied electric potential and resulting electric current, while submerged in an electrolyte, is disclosed in order to increase the biochar electrode's pore surface area and pore hierarchy, to affect a cleaning of unwanted materials and compounds from within the electrode and to optionally plate materials onto the surface pores of the electrode, such as graphene or metals, thus increasing the energy storage capacity of the biochar electrode when used in an energy storage device. Exemplary applications include electrodes for ultra-capacitors, pseudo-capacitors, batteries, fuel cells and other absorbing and desorbing applications.

A method for treating a carbonaceous biochar electrode with an applied electric potential and resulting electric current, while submerged in an electrolyte, is disclosed in order to increase the biochar electrode's pore surface area and pore hierarchy, to affect a cleaning of unwanted materials and compounds from within the electrode and to optionally plate materials onto the surface pores of the electrode, such as graphene or metals, thus increasing the energy storage capacity of the biochar electrode when used in an energy storage device. Exemplary applications include electrodes for ultra-capacitors, pseudo-capacitors, batteries, fuel cells and other absorbing and desorbing applications.

A power storage material is made by using a fiber material of cellulose molecules obtained from wood, plant fibers (pulp), and the like, and capable of storing electric power of direct current and alternating current, and an ultra power storage body has the power storage material. A power storage material includes a fiber mainly including a fiber derived from at least any one of wood, plant fibers (pulp), animals, algae, microorganisms, and microbial products, and having a large number of recesses and protrusions on a surface. The fiber is preferably crystallized/amorphous fibers, is preferably an amorphous fiber having an atomic vacancy, and preferably has a specific surface area of 10 m.sup.2/g or more. Preferably, the large number of recesses and protrusions have a diameter of 1 nm to 500 nm. Preferably, the electric resistance is 100 MΩ or more, and the electric capacity is 5 mF/cm.sup.2 or more

Provided is a conductive carbon mixture which is to be used together with an electrode active material in manufacturing an electrode of an electricity storage device and enables the manufacture of the electricity storage device having a good cycle life. The conductive carbon mixture for manufacturing an electrode of an electricity storage device comprises an oxidized carbon having electrical conductivity and a different conductive carbon which is different from the oxidized carbon, wherein the oxidized carbon covers the surface of the different conductive carbon. The conductive carbon mixture is characterized in that the ratio of the peak intensity of the 2D band to the peak intensity of the D band in a Raman spectrum of the conductive carbon mixture is 55% or less relative to the ratio of the peak intensity of the 2D band to the peak intensity of the D band in a Raman spectrum of the different conductive carbon. This conductive carbon mixture covers the surface of the electrode active material in a particularly good manner and thus prolongs the cycle life of the electricity storage device.

Provided is a conductive carbon mixture which is to be used together with an electrode active material in manufacturing an electrode of an electricity storage device and enables the manufacture of the electricity storage device having a good cycle life. The conductive carbon mixture for manufacturing an electrode of an electricity storage device comprises an oxidized carbon having electrical conductivity and a different conductive carbon which is different from the oxidized carbon, wherein the oxidized carbon covers the surface of the different conductive carbon. The conductive carbon mixture is characterized in that the ratio of the peak intensity of the 2D band to the peak intensity of the D band in a Raman spectrum of the conductive carbon mixture is 55% or less relative to the ratio of the peak intensity of the 2D band to the peak intensity of the D band in a Raman spectrum of the different conductive carbon. This conductive carbon mixture covers the surface of the electrode active material in a particularly good manner and thus prolongs the cycle life of the electricity storage device.

A method, including irradiating graphene oxide (GO) with a beam of light or radiation to form reduced graphene oxide (RGO) in a three-dimensional (3D) pattern, wherein the RGO is porous RGO with pores having sizes tuned by controlling the beam of light or radiation.

A method, including irradiating graphene oxide (GO) with a beam of light or radiation to form reduced graphene oxide (RGO) in a three-dimensional (3D) pattern, wherein the RGO is porous RGO with pores having sizes tuned by controlling the beam of light or radiation.

A poly(vinylphosphonic acid) (PVPA) - (NH.sub.4).sub.2MoO.sub.4), gel polymer electrolyte can be prepared by incorporating redox-mediated Mo, or similar metal, into a PVPA, or similar polymer, matrix. Gel polymer electrolytes including PVPA/MoX, x representing the percent fraction Mo in PVPA, can be used to make supercapacitors including active carbon electrodes. The electrolytes can be in gel form, bendable and stretchable in a device. Devices including this gel electrolyte can have a specific capacitance (Cs) of 1276 F/g, i.e., a more than 50-fold increase relative to a PVPA system without Mo. A PVPA / Mo10 supercapacitor can have an energy density of 180.2 Wh/kg at power density of 500 W/kg, and devices with this hydrogel structure may maintain 85+% of their initial capacitance performance after 2300 charge-discharge cycles.