Provided herein are energy storage devices comprising a first electrode comprising a layered double hydroxide, a conductive scaffold, and a first current collector; a second electrode comprising a hydroxide and a second current collector; a separator; and an electrolyte. In some embodiments, the specific combination of device chemistry, active materials, and electrolytes described herein form storage devices that operate at high voltage and exhibit the capacity of a battery and the power performance of supercapacitors in one device.

Described are solid-state electrochemical energy storage devices and methods of making solid-state electrochemical energy storage devices in which components of the batteries are truly solid-state and do not comprise a gel. Nor do they rely on lithium-containing electrolytes. Electrolytes useful with the solid-state electrochemical energy storage described herein include, for example, ceramic electrolytes exhibiting a crystal structure including voids or crystallographic defects that permit conduction or migration of oxygen ions across a layer of the ceramic electrolyte. Disclosed methods of making solid-state electrochemical energy storage devices include multi-stage deposition processes, in which an electrode is deposited in a first stage and an electrolyte is deposited in a second stage.

Provided is a process for preparing an electrode comprising an iron active material. The process comprises first fabricating an electrode comprising an iron active material, and then treating the surface of the electrode with an oxidant solution to thereby create an oxidized surface. The resulting iron electrode is thereby preconditioned prior to any charge-discharge cycle to have the assessable surface of the iron active material in the same oxidation state as in discharged iron negative electrodes active material.

A positive electrode for an alkaline secondary battery includes a positive electrode substrate and a positive electrode composite material that is provided on at least one surface of the positive electrode substrate. The positive electrode substrate contains a Ni foil or a Ni-plated steel foil. The positive electrode composite material contains a positive electrode active material. The positive electrode active material contains nickel hydroxide coated with cobalt oxyhydroxide. A weight per unit area of the positive electrode composite material with respect to the one surface of the positive electrode substrate is 0.02 g/cm.sup.2 to 0.035 g/cm.sup.2.

In an embodiment, an active material-based nanocomposite is synthesized by infiltrating an active material precursor into pores of a nanoporous carbon, metal or metal oxide material, and then annealing to decompose the active material precursor into a first gaseous material and an active material and/or another active material precursor infiltrated inside the pores. The nanocomposite is then exposed to a gaseous material or a liquid material to at least partially convert the active material and/or the second active material precursor into active material particles that are infiltrated inside the pores and/or to infiltrate a secondary material into the pores. The nanocomposite is again annealed to remove volatile residues, to enhance electrical contact within the active material-based nanocomposite composite and/or to enhance one or more structural properties of the nanocomposite. In a further embodiment, the pores may be further infiltrated with a filler material and/or may be at least partially sealed.

Described are solid-state electrochemical energy storage devices and methods of making solid-state electrochemical energy storage devices in which components of the batteries are truly solid-state and do not comprise a gel. Nor do they rely on lithium-containing electrolytes. Electrolytes useful with the solid-state electrochemical energy storage described herein include, for example, ceramic electrolytes exhibiting a crystal structure including voids or crystallographic defects that permit conduction or migration of oxygen ions across a layer of the ceramic electrolyte. Disclosed methods of making solid-state electrochemical energy storage devices include multi-stage deposition processes, in which an electrode is deposited in a first stage and an electrolyte is deposited in a second stage.

Provided herein are energy storage devices comprising a first electrode comprising a layered double hydroxide, a conductive scaffold, and a first current collector; a second electrode comprising a hydroxide and a second current collector; a separator; and an electrolyte. In some embodiments, the specific combination of device chemistry, active materials, and electrolytes described herein form storage devices that operate at high voltage and exhibit the capacity of a battery and the power performance of supercapacitors in one device.

Provided is a process for preparing an electrode comprising an iron active material. The process comprises first fabricating an electrode comprising an iron active material, and then treating the surface of the electrode with an oxidant solution to thereby create an oxidized surface. The resulting iron electrode is thereby preconditioned prior to any charge-discharge cycle to have the assessable surface of the iron active material in the same oxidation state as in discharged iron negative electrodes active material.

Energy storage devices comprising carbon-based electrodes comprising energy-dense faradaic materials and oxidation-reduction (redox) electrolytes are disclosed. In some embodiments, the carbon-based electrodes comprise energy-dense magnetite nanoparticles. In some embodiments, the redox electrolytes comprise ferricyanide/ferrocyanide redox couple. Also described are processes, methods, protocols, and the like for manufacturing carbon-based electrodes comprising magnetite nanoparticles for use in high energy storage devices such as supercapacitors and for manufacturing high energy storage devices comprising redox electrolytes.

The present invention relates to a method for preparing a lithium iron phosphate nanopowder coated with carbon, including the steps of (a) preparing a mixture solution by adding a lithium precursor, an iron precursor and a phosphorus precursor in a glycol-based solvent, (b) putting the mixture solution into a reactor, heating and concentrating to prepare a metal glycolate slurry, (c) drying the metal glycolate slurry to form a solid content, and (d) firing the solid content to prepare the lithium iron phosphate nanopowder coated with carbon, and a lithium iron phosphate nanopowder coated with carbon prepared by the method.