A positive electrode active material for a non-aqueous electrolyte secondary battery, according to an example of this embodiment, includes a lithium transition metal composite oxide which has a layered structure and contains at least Ni, Al, and Ca. The lithium transition metal composite oxide has a Ni content of 85-95 mol %, an Al content of at most 8 mol %, and a Ca content of at most 2 mol % with respect to the total amount of metal elements other than Li. In addition, the proportion of metal elements other than Li present in a Li layer is 0.6-2.0 mol % with respect to the total amount of metal elements other than Li contained in the composite oxide.

An electrochemical half-cell includes an electrical terminal lead in contact with a solid electrolyte, wherein the solid electrolyte includes a doped high-entropy oxide. The electrochemical half-cell can be used as either a reference half-cell or a measuring half-cell. Methods of manufacturing the solid electrolyte and the electrochemical half-cell are further disclosed.

A method for manufacturing a cathode electrode includes forming a composite cathode active material by providing a first cathode active material. The first cathode active material comprises a lithium- and manganese-rich (LMR) cathode active material. The method includes forming an outer layer including a second cathode active material on the first cathode active material to form a composite cathode active material. The second cathode active material comprises an NMX cathode active material including lithium, and nickel and manganese with a molar ratio in a range from 3/7 to 8/2.

To provide a method of forming a positive electrode active material with high productivity. To provide a manufacturing apparatus capable of forming a positive electrode active material with high productivity. Provided is a method of forming a positive electrode active material including lithium, a transition metal, oxygen, and fluorine. An adhesion preventing step is performed during heating of an object. Examples of the adhesion preventing step include stirring by rotating a furnace during the heating, stirring by vibrating a container containing an object during the heating, and crushing performed between the plurality of heating steps. By these manufacturing methods, a positive electrode active material having favorable distribution of an additive at the surface portion can be formed.

To provide a method of forming a positive electrode active material with high productivity. To provide a manufacturing apparatus capable of forming a positive electrode active material with high productivity. Provided is a method of forming a positive electrode active material including lithium, a transition metal, oxygen, and fluorine. An adhesion preventing step is performed during heating of an object. Examples of the adhesion preventing step include stirring by rotating a furnace during the heating, stirring by vibrating a container containing an object during the heating, and crushing performed between the plurality of heating steps. By these manufacturing methods, a positive electrode active material having favorable distribution of an additive at the surface portion can be formed.

A lithium ion battery having excellent charge performance and discharge performance even in a low-temperature environment is provided. A lithium ion battery includes a positive electrode active material containing cobalt, oxygen, magnesium, aluminum, and nickel. The median diameter of the positive electrode active material is greater than or equal to 1 m and less than or equal to 12 m. Magnesium and aluminum are included in a surface portion. The surface portion is a region within 50 nm in depth from the surface of the positive electrode active material. The positive electrode active material includes a region where magnesium is distributed closer to the surface side of the positive electrode active material than aluminum is.

A lithium ion battery having excellent charge performance and discharge performance even in a low-temperature environment is provided. A lithium ion battery includes a positive electrode active material containing cobalt, oxygen, magnesium, aluminum, and nickel. The median diameter of the positive electrode active material is greater than or equal to 1 m and less than or equal to 12 m. Magnesium and aluminum are included in a surface portion. The surface portion is a region within 50 nm in depth from the surface of the positive electrode active material. The positive electrode active material includes a region where magnesium is distributed closer to the surface side of the positive electrode active material than aluminum is.

A cathode active material for a lithium secondary battery according to embodiments of the present invention has a high-nickel composition and includes a lithium-nickel composite metal oxide particle in which lithium, nickel and a metal having an oxidation number of +2 are combined in a predetermined range. A cation disorder caused when a nickel ion is present at a lithium-ion site is reduced to improve structural stability of the cathode active material. An initial capacity and a battery efficiency of a lithium secondary battery can be improved using the cathode active material.

A cathode active material for a lithium secondary battery according to embodiments of the present invention has a high-nickel composition and includes a lithium-nickel composite metal oxide particle in which lithium, nickel and a metal having an oxidation number of +2 are combined in a predetermined range. A cation disorder caused when a nickel ion is present at a lithium-ion site is reduced to improve structural stability of the cathode active material. An initial capacity and a battery efficiency of a lithium secondary battery can be improved using the cathode active material.

The present invention is related to a process for making an electrode active material wherein said process comprises the following steps: (a) Providing a hydroxide TM(OH).sub.2 or at least one oxide TMO or at least one oxyhydroxide of TM or a combination of at least two of the foregoing wherein TM is one or more metals and contains at least 97 mol-% Ni and, optionally, in total up to 3 mol-% of at least one metal selected from Al, Ti, Zr, V, Co, Zn, Ba, and Mn; (b) mixing said hydroxide TM(OH).sub.2 or oxide TMO or oxyhydroxide of TM or combination with a source of lithium and a source of Mg wherein the molar amount of (Li+Mg) corresponds to 75 to 95 mol-% of TM; (c) treating the mixture obtained from step (b) thermally at a temperature in the range of from 450 to 650 C., thereby obtaining an intermediate; (d) mixing the intermediate from step (c) with a source of Li and with at least one compound of a metal M.sup.1 selected from Al, Zr, Co, Mn, Nb, Ta, Mo, and W; (e) treating the mixture obtained from step (d) thermally at a temperature in the range of from 500 to 850 C.