Provided is a power storage device having excellent withstand voltage performance and enabling high-voltage driving. This power storage device includes: an electrode formed of an electrode material containing a carbon material and essentially free of a binder; and an electrolytic solution including an ionic liquid including, as components, a cation and an anion.

Provided is a power storage device having excellent withstand voltage performance and enabling high-voltage driving. This power storage device includes: an electrode formed of an electrode material containing a carbon material and essentially free of a binder; and an electrolytic solution including an ionic liquid including, as components, a cation and an anion.

A battery having a plurality of electrodes immersed in a water-in-salt electrolytic solution is disclosed. The water-in-salt electrolytic solution includes a sufficient amount of a lithium salt disposed in an aqueous solvent, at least 14 moles of lithium salt per kg of aqueous solvent, such that a dissociated lithium ion is solvated by less than 4 water molecules. The plurality of electrodes includes a first type electrode, a second type electrode, and a third type electrode selectively assembled in a predetermined order of arrangement into an electrode stack assembly. The first type electrode includes an activated carbon, the second type electrodes include one of a lithium manganese oxide (LMO) and titanium dioxide (TiO.sub.2), and the third type electrodes include the other of the LMO and TiO.sub.2. The first type electrode may be that of a cathode and/or anode.

A solid state polymer electrolyte is disclosed for use in an ultracapacitor. The electrolyte includes an ionic liquid and a polymer and may include other additives, wherein an ultracapacitor that utilizes the solid state electrolyte is configured to output electrical energy at temperatures between about −40° C. and about 250° C. or more.

Some embodiments include an integrated assembly having a supercapacitor supported by a semiconductor substrate. The supercapacitor includes first and second electrode bases. The first electrode base includes first laterally-projecting regions, and the second electrode base includes second laterally-projecting regions which are interdigitated with the first laterally-projecting regions. A distance between the first and second laterally-projecting regions is less than or equal to about 500 nm. Carbon nanotubes extend upwardly from the first and second electrode bases. The carbon nanotubes are configured as a first membrane structure associated with the first electrode base and as a second membrane structure associated with the second electrode base. Pseudocapacitive material is dispersed throughout the first and second membrane structures. Electrolyte material is within and between the first and second membrane structures. Some embodiments include methods of forming integrated assemblies.

An electric double-layer ultracapacitor configured to maintain desired operation at an operating voltage of three volts, where the capacitor includes a housing component, a first and a second current collector, a positive and a negative electrode electrically coupled to one of the first and second current collectors, and a separator positioned between the positive and the negative electrode. At least one of the positive electrode and the negative electrode can include a treated carbon material, where the treated carbon material includes a reduction in a number of hydrogen-containing functional groups, nitrogen-containing functional groups and/or oxygen-containing functional groups.

An electric double-layer ultracapacitor configured to maintain desired operation at an operating voltage of three volts, where the capacitor includes a housing component, a first and a second current collector, a positive and a negative electrode electrically coupled to one of the first and second current collectors, and a separator positioned between the positive and the negative electrode. At least one of the positive electrode and the negative electrode can include a treated carbon material, where the treated carbon material includes a reduction in a number of hydrogen-containing functional groups, nitrogen-containing functional groups and/or oxygen-containing functional groups.

An energy-storage device is provided. It includes a charge-storing supercapacitor cell comprised of electrodes at least one of which includes a nano-carbon component, a ion-permeable membrane and an electrolyte characterised in that the cell is embedded or encapsulated in a flexible or rigid matrix.

An energy-storage device is provided. It includes a charge-storing supercapacitor cell comprised of electrodes at least one of which includes a nano-carbon component, a ion-permeable membrane and an electrolyte characterised in that the cell is embedded or encapsulated in a flexible or rigid matrix.

In some embodiments, an electrode can include a current collector, a composite material in electrical communication with the current collector, and at least one phase configured to adhere the composite material to the current collector. The current collector can include one or more layers of metal, and the composite material can include electrochemically active material. The at least one phase can include a compound of the metal and the electrochemically active material. In some embodiments, a composite material can include electrochemically active material. The composite material can also include at least one phase configured to bind electrochemically active particles of the electrochemically active material together. The at least one phase can include a compound of metal and the electrochemically active material.