A recovery method for a positive electrode active material includes: separating and recovering, from a positive electrode plate of a battery in which a positive electrode mixture containing a positive electrode active material is laminated on a positive electrode foil, the positive electrode mixture; supplying at least one of ozone and hydrogen peroxide to a slurry containing the positive electrode mixture to oxidize the positive electrode mixture; and separating and recovering the positive electrode active material from the slurry.

Provided are a sodium ion-conductive crystal-containing solid electrolyte sheet capable of giving excellent battery characteristics even when reduced in thickness, and an all-solid-state battery using the same. The solid electrolyte sheet contains at least one type of sodium ion-conductive crystal selected from β″-alumina and NASICON crystal and has a thickness of 500 μm or less and a flatness of 200 μm or less.

A method for producing an electrode material for a lithium-ion secondary battery. The method includes the following steps: (a) mixing components of a basic ingredient or active substance of electrode material and a conductive carbon material to obtain a conductive carbon material-composited material; (b) mixing the conductive carbon material-composited material and a surface layer-forming material; an (c) burning the mixture obtained at step (b) to obtain the electrode material. Also, a lithium-ion secondary battery including an electrode which comprises the material.

A method for producing an electrode material for a lithium-ion secondary battery. The method includes the following steps: (a) mixing components of a basic ingredient or active substance of electrode material and a conductive carbon material to obtain a conductive carbon material-composited material; (b) mixing the conductive carbon material-composited material and a surface layer-forming material; an (c) burning the mixture obtained at step (b) to obtain the electrode material. Also, a lithium-ion secondary battery including an electrode which comprises the material.

The present invention relates to a ceramic solid electrolyte, which is a key component of an all-solid-state lithium secondary battery, for improving safety, and a method for synthesizing the same. The present invention relates to an oxide-based conductive ceramic of a new NASICON structure of the chemical formula Li.sub.1+xAl.sub.xX.sub.2−xP.sub.3O.sub.12 (X is Zr, Si, Sn, or Y, 0<x<2) or Li.sub.1+xZr.sub.2X.sub.xP.sub.3−xO.sub.12 (X=Si, Sn, Ge, or Y, 1.5≤x≤2.3). The present invention relates to a method for manufacturing an oxide-based conductive ceramic having the above novel NASICON structure.

The present invention relates to a ceramic solid electrolyte, which is a key component of an all-solid-state lithium secondary battery, for improving safety, and a method for synthesizing the same. The present invention relates to an oxide-based conductive ceramic of a new NASICON structure of the chemical formula Li.sub.1+xAl.sub.xX.sub.2−xP.sub.3O.sub.12 (X is Zr, Si, Sn, or Y, 0<x<2) or Li.sub.1+xZr.sub.2X.sub.xP.sub.3−xO.sub.12 (X=Si, Sn, Ge, or Y, 1.5≤x≤2.3). The present invention relates to a method for manufacturing an oxide-based conductive ceramic having the above novel NASICON structure.

A positive electrode active material includes a lithium-transition metal composite phosphate including a first crystalline phase having a composition represented by Formula 1 and having an olivine structure, and a second crystalline phase having a composition represented by Formula 2 and having a pyrophosphate-containing structure, wherein the second crystalline phase is in an amount of greater than 0 mole percent and not greater than 50 mole percent with respect to a total number of moles of the first crystalline phase and the second crystalline phase, a positive electrode, a secondary battery:

Li.sub.xM1.sub.yPO.sub.4   Formula 1

Li.sub.aM2.sub.b(P.sub.2O.sub.7).sub.4   Formula 2 In Formulas 1 and 2, 0.9≤x≤1.1, 0.9≤y≤1.1, 5.5≤a≤6.5, and 4.8≤b≤5.2, and M1 and M2 are each independently an element from Groups 3 to 11 in the 4th period of the Periodic Table of the Elements, or a combination thereof.

A composite material includes vanadium lithium phosphate, and a conductive carbon. an amount of the conductive carbon is 2.5 mass % or more and 7.5 mass % or less.

A composite material includes vanadium lithium phosphate, and a conductive carbon. an amount of the conductive carbon is 2.5 mass % or more and 7.5 mass % or less.

The present invention provides a novel positive electrode active material for a sodium-ion secondary battery having a high voltage and a high capacity. The positive electrode active material for a sodium-ion secondary battery contains, in terms of % by mole of oxide, 8 to 55% Na.sub.2O, 10 to 70% CoO, 0 to 60% CrO+FeO+MnO+NiO, and 15 to 70% P.sub.2O.sub.5+SiO.sub.2+B.sub.2O.sub.3 and also contains an amorphous phase.