A positive electrode active material particle with little deterioration is provided. A power storage device with little deterioration is provided. A highly safe power storage device is provided. The positive electrode active material particle includes a first crystal grain, a second crystal grain, and a crystal grain boundary positioned between the crystal grain and the second crystal grain; the first crystal grain and the second crystal grain include lithium, a transition metal, and oxygen; the crystal grain boundary includes magnesium and oxygen; and the positive electrode active material particle includes a region where the ratio of the atomic concentration of magnesium in the crystal grain boundary to the atomic concentration of the transition metal in first crystal grain and the second crystal grain is greater than or equal to 0.010 and less than or equal to 0.50.

A cobalt-free layered positive electrode material, a preparation method thereof, and a lithium-ion battery are provided. The method includes: preparing a layered lithium nickel manganese oxide matrix material; mixing the layered lithium nickel manganese oxide matrix material with a coating agent to obtain a first mixed material; and forming a coating layer on a surface of the layered lithium nickel manganese oxide matrix material by performing a first sintering treatment on the first mixed material to obtain the cobalt-free layered positive electrode material. The coating agent includes a first coating agent including ceramic oxide, and a second coating agent including at least one of phosphate and silicate.

A mixed powder for an all-solid-state lithium-ion battery, which is composed of a positive electrode active material for a lithium-ion battery and a solid electrolyte, wherein the positive electrode active material for a lithium-ion battery is composed of particles containing crystals of a lithium metal composite oxide, and the lithium metal composite oxide has a layered structure and contains at least Li and a transition metal, wherein the positive electrode active material for a lithium-ion battery has a particle diameter distribution that satisfies the following Formula (1), and wherein the solid electrolyte has a particle diameter distribution that satisfies the following Formula (2):

[00001]$\left(\text{D90-D10}\right)/\text{D50}\le \text{1}\text{.5}$

[00002]$\left(\text{D90-D10}\right)/\text{D50}\le 2.0$

A positive electrode material and a preparation method therefor, a lithium-ion battery, and an electric vehicle. The positive electrode material comprises: matrix particles, materials forming the matrix particles comprising at least one of a lithium-rich manganese-based material, lithium nickel cobalt manganese oxide, lithium nickel cobalt aluminum oxide, lithium iron phosphate, lithium manganate, lithium nickel cobalt manganese aluminate, and lithium nickel manganate; and a housing, the housing covering at least a portion of the outer surfaces of the matrix particles.

Secondary batteries using lithium cobalt oxide as positive electrode active materials have a problem of a decrease in battery capacity due to repeated charging/discharging, for example. A positive electrode active material particle which hardly deteriorates is provided. In a first step, a container in which a lithium oxide and a fluoride are set is placed in a heating furnace, and in a second step, the inside of the heating furnace is heated in an atmosphere containing oxygen. The heating temperature of the second step is from 750° C. to 950° C., inclusive. By the manufacturing method, fluorine can be contained in the positive electrode active material particle to increase the wettability of the surface of the positive electrode active material so that the surface of the positive electrode active material is homogenized and planarized. The crystal structure of the thus manufactured positive electrode active material is unlikely to be broken in repeated high-voltage charging/discharging. Thus, secondary batteries using the positive electrode active material having such a feature have greatly improved cycle characteristics.

The present invention pertains to a positive electrode active material for a lithium secondary battery, the positive electrode active material having a layered structure and containing lithium, transition metals, fluorine (F), and oxygen, wherein the layered structure includes a lithium layer consisting solely of lithium and a transition metal layer consisting solely of transition metals including nickel, the nickel includes Ni.sup.3+ and Ni.sup.2+ in terms of oxidation number, and the ratio (Ni.sup.2+/Ni.sup.3+) of Ni.sup.2+ to Ni.sup.3+ increases as the fluorine content increases.

A positive electrode active material having a crystal structure that is unlikely to be broken by repeated charging and discharging is provided. A positive electrode active material with high charge and discharge capacity is provided. One embodiment of the present invention is a positive electrode active material containing lithium, cobalt, nickel, and oxygen; in which a molar ratio of lithium, cobalt, and nickel is lithium: cobalt: nickel=1:1−x: x (0.3<x<0.75); in which the average of a bond distance between cobalt and oxygen and a bond distance between nickel and oxygen is longer than or equal to 1.94×10.sup.−10 m and shorter than or equal to 2.1×10.sup.−10 m in a crystal structure of the positive electrode active material; and in which the average of an angle formed between a line connecting cobalt to an adjacent oxygen and a line connecting cobalt to another adjacent oxygen and an angle formed between a line connecting nickel to an adjacent oxygen and a line connecting nickel to another adjacent oxygen is greater than or equal to 86.5° and less than 90°.

A secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode includes a positive electrode active material layer. The positive electrode active material layer includes a lithium-nickel composite oxide of a layered rock-salt type.

A secondary battery includes a positive electrode, a negative electrode, and an electrolytic solution. The positive electrode includes a positive electrode active material layer. The positive electrode active material layer includes a lithium-nickel composite oxide of a layered rock-salt type.

There is provided a method for collecting and reusing an active material from positive electrode scrap. The method of reusing a positive electrode active material of the present disclosure includes (a-1) immersing a positive electrode scrap comprising an active material layer on a current collector into a basic solution to separate the active material layer from the current collector, (a-2) thermally treating the active material layer in air for thermal decomposition of a binder and a conductive material in the active material layer, and collecting an active material in the active material layer, (b) washing the active material collected from the step (a-2) with a lithium compound solution which is basic in an aqueous solution and drying, and (c) annealing the active material washed from the step (b) with a lithium precursor to obtain a reusable active material.