An energy bank is provided that includes a plurality of integrated energy storage devices comprising a plurality of supercapacitors, a plurality of batteries and a plurality of metal shells. Each of the integrated energy storage devices comprises a supercapacitor, a battery surrounding the supercapacitor and a metal shell surrounding the battery. The battery forms a shell around an exterior surface of the supercapacitor. The battery includes a first anode, a first cathode, and an electrolyte disposed between the first anode and the first cathode. The supercapacitor includes a second anode, a second cathode, and a separator disposed between the second anode and the second cathode.

A mixed conductor represented by Formula 1:
A.sub.4±xTi.sub.5−yG.sub.zO.sub.12−δ  Formula 1 wherein, in Formula 1, A is a monovalent cation, G is at least one of a monovalent cation, a divalent cation, a trivalent cation, a tetravalent cation, a pentavalent cation, or a hexavalent cation, with the proviso that G is not Ti or Cr, wherein 0<x<2, 0.3<y<5, 0<z<5, and 0<δ≤3.

A mixed conductor represented by Formula 1:
A.sub.4±xTi.sub.5−yG.sub.zO.sub.12−δ  Formula 1 wherein, in Formula 1, A is a monovalent cation, G is at least one of a monovalent cation, a divalent cation, a trivalent cation, a tetravalent cation, a pentavalent cation, or a hexavalent cation, with the proviso that G is not Ti or Cr, wherein 0<x<2, 0.3<y<5, 0<z<5, and 0<δ≤3.

Described herein is an aqueous aluminum ion battery featuring an aluminum or aluminum alloy/composite anode, an aqueous electrolyte, and a manganese oxide, aluminosilicate or polymer-based cathode. The battery operates via an electrochemical reaction that entails an actual transport of aluminum ions between the anode and cathode. The compositions and structures described herein allow the aqueous aluminum ion battery described herein to achieve: (1) improved charge storage capacity; (2) improved gravimetric and/or volumetric energy density; (3) increased rate capability and power density (ability to charge and discharge in shorter times); (4) increased cycle life; (5) increased mechanical strength of the electrode; (6) improved electrochemical stability of the electrodes; (7) increased electrical conductivity of the electrodes, and (8) improved ion diffusion kinetics in the electrodes as well as the electrolyte.

A method to a fabricate high surface area, high performance supercapacitor includes include applying a metal layer to at least a portion of a nanostructure; after applying the metal layer, oxidizing the metal layer; applying a plurality of additional metal layers onto a previously oxidized metal layer; and after applying each additional metal layer, oxidizing the additional metal layer prior to applying a successive additional metal layer. The metal layers may include a composition comprising at least one metal, the at least one metal selected from the group consisting of ruthenium, titanium, manganese, vanadium, iron, tin, cobalt and nickel. Optionally, each of the additional metal layers may be applied using atomic layering deposition (ALD).

A method to a fabricate high surface area, high performance supercapacitor includes include applying a metal layer to at least a portion of a nanostructure; after applying the metal layer, oxidizing the metal layer; applying a plurality of additional metal layers onto a previously oxidized metal layer; and after applying each additional metal layer, oxidizing the additional metal layer prior to applying a successive additional metal layer. The metal layers may include a composition comprising at least one metal, the at least one metal selected from the group consisting of ruthenium, titanium, manganese, vanadium, iron, tin, cobalt and nickel. Optionally, each of the additional metal layers may be applied using atomic layering deposition (ALD).

The present invention relates to an elastic fiber electrode including a hybrid fiber prepared by coating a carbon nanotube sheet on a polymer fiber, in which the hybrid fiber is in a yarn form having a coiled structure, and the carbon nanotube sheet makes a wrinkled surface, and a coil- or spring-type elastic fiber electrode manufactured by coiling a hybrid nanofiber prepared by coating a carbon nanotube sheet on a polymer fiber has excellent mechanical and electrical properties. In particular, the elastic fiber electrode has increased porosity by depositing manganese dioxide on a surface thereof, thereby enhancing electrochemical performance. Thus, a micro-supercapacitor using the elastic fiber electrode has high current density and excellent capacitance retention, may maintain the electrochemical characteristics even after being subjected to various deformations, such as bending, coiling, or weaving, and has high elasticity and reversible behaviors, thus providing stable capacitance.

In one aspect, the present disclosure relates to an improved method of preparing concentrated MnO.sub.2 ink with increased efficiency and cost effectiveness. The method involves mixing KMnO.sub.4 solution with highly crystalline carbon particles (HCCPs) with average diameters less than 800 nm at 30-60° C. for at least 8 hours. The present disclosure further relates to a symmetric supercapacitor device comprising MnO.sub.2 coated electrodes and a solid state ionic liquid as electrolyte, as well as an interdigital transparent SC (IT-SC) device comprising aqueous MnO.sub.2 ink.

In one aspect, the present disclosure relates to an improved method of preparing concentrated MnO.sub.2 ink with increased efficiency and cost effectiveness. The method involves mixing KMnO.sub.4 solution with highly crystalline carbon particles (HCCPs) with average diameters less than 800 nm at 30-60° C. for at least 8 hours. The present disclosure further relates to a symmetric supercapacitor device comprising MnO.sub.2 coated electrodes and a solid state ionic liquid as electrolyte, as well as an interdigital transparent SC (IT-SC) device comprising aqueous MnO.sub.2 ink.

As an electrode for a power storage device, an electrode including a current collector, a first active material layer over the current collector, and a second active material layer that is over the first active material layer and includes a particle containing niobium oxide and a granular active material is used, whereby the charge-discharge cycle characteristics and rate characteristics of the power storage device can be improved. Moreover, contact between the granular active material and the particle containing niobium oxide makes the granular active material physically fixed; accordingly, deterioration due to expansion and contraction of the active material which occur along with charge and discharge of the power storage device, such as powdering of the active material or its separation from the current collector, can be suppressed.