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 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 lithium-replenishing additive is provided. The lithium-replenishing additive includes a lithium-rich-material core and a shell layer disposed at the lithium-rich-material core. The lithium-rich-material core is made of a lithium-rich material with an average chemical formula of aNi.sub.xM.sub.yO.sub.2 .Math.bLi.sub.2O, where 0.95≤x≤1, 0.01≤y≤0.05, 1≤z≤1.15, 0.8≤a≤1.1, 0.8≤b≤1.1, and the M includes one or more of copper (Cu), cobalt (Co), aluminum (Al), titanium (Ti), vanadium (V), zirconium (Zr), or iron (Fe). The shell layer includes a polymer layer. A preparing method of a lithium-replenishing additive and a lithium secondary battery are further provided.

A lithium-replenishing additive is provided. The lithium-replenishing additive includes a lithium-rich-material core and a shell layer disposed at the lithium-rich-material core. The lithium-rich-material core is made of a lithium-rich material with an average chemical formula of aNi.sub.xM.sub.yO.sub.2 .Math.bLi.sub.2O, where 0.95≤x≤1, 0.01≤y≤0.05, 1≤z≤1.15, 0.8≤a≤1.1, 0.8≤b≤1.1, and the M includes one or more of copper (Cu), cobalt (Co), aluminum (Al), titanium (Ti), vanadium (V), zirconium (Zr), or iron (Fe). The shell layer includes a polymer layer. A preparing method of a lithium-replenishing additive and a lithium secondary battery are further provided.

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 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.

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.

What is claimed is a positive electrode active material for an all-solid-state lithium-ion battery composed of particles containing crystals of a lithium metal composite oxide,

wherein the lithium metal composite oxide has a layered structure and contains at least Li and a transition metal, and wherein, in the particles, in pore physical properties obtained from nitrogen adsorption isotherm measurement and nitrogen desorption isotherm measurement at a liquid nitrogen temperature, the total pore volume obtained from a nitrogen adsorption amount when the relative pressure (p/p.sub.0) of an adsorption isotherm is 0.99 is less than 0.0035 cm.sup.3/g.