Provided is a heterofullerene where n number (where n is a positive even number) of carbon atoms constituting a fullerene are substituted by n number of boron atoms or n number of nitrogen atoms.

A positive electrode active material for a non-aqueous electrolyte secondary battery that includes a lithium transition metal composite oxide having a spinel structure and containing nickel and manganese is provided. The positive electrode active material includes a first surface region having a chemical composition with a molar ratio of nickel to manganese of 0.1 or less on the surface of the lithium transition metal composite oxide.

An advantage is to provide a non-aqueous electrolyte secondary battery with improved heat resistance. A positive electrode active material contains a lithium-transition metal composite oxide containing 80 mol % or more of Ni and 0.1 mol % to 1.5 mol % of B on the basis of the total number of moles of metal elements excluding Li, and B and at least one element (M1) selected from Groups 4 to 6 are present on at least the surfaces of particles of the composite oxide. When particles having a volume-based particle size larger than 70% particle size (D70) are first particles, and particles having a volume-based particle size smaller than 30% particle size (D30) are second particles, the molar fraction of M1 on the basis of the total number of moles of metallic elements excluding Li on the surfaces of the second particles is greater than that of the first particles.

An ionic conductor includes an inorganic oxychloride compound with a chemical composition of (Fe.sub.1-xM.sub.x)O.sub.1-y(OH).sub.yCl.sub.1-x where M is selected from at least one of Mg and Ca, and x is greater than 0 and less than or equal to 0.25, y is greater than or equal to 0 and less than or equal to 0.25. The inorganic oxychloride compound has a thermal decomposition start temperature of about 410° C. and x-ray diffraction peaks (2θ) between about 20.79° and about 22.79°, between about 30.03° and about 32.03°, between about 39.47° and about 41.47°, and between about 76.44° and about 78.44°.

A positive electrode active material is constituted by lithium transition metal-containing composite oxide particles having a layered rock salt type crystal structure and are composed of secondary particles each formed of an aggregation of primary particles. The secondary particles have a d50 of 3.0 to 7.0 μm, a BET specific surface area of 1.8 to 5.5 m.sup.2/g, a pore peak diameter of 0.01 to 0.30 μm, and a log differential pore volume [dV/d(log D)] of 0.2 to 0.6 ml/g within a range of the pore peak diameter. In each of a plurality of primary particles having a primary particle size of 0.1 to 1.0 μm, a coefficient of variation of the concentration of an additive element M is 1.5 or less.

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.

A positive active material includes a nickel-based composite metal oxide having the form of secondary particles in which a plurality of primary particles are agglomerated, where each secondary particle includes a core and a shell, the primary particles of the shell are coated with a manganese-containing nickel-based composite metal oxide, and the manganese-containing nickel-based composite metal oxide has a layered structure.

A zirconia powder in which when a stabilizer is Y.sub.2O.sub.3, a content thereof is 1.4 mol % or more and less than 2.0 mol %; when the stabilizer is Er.sub.2O.sub.3, a content thereof is 1.4 mol % or more and 1.8 mol % or less; when the stabilizer is Yb.sub.2O.sub.3, a content thereof is 1.4 mol % or more and 1.8 mol % or less; and when the stabilizer is CaO, a content thereof is 3.5 mol % or more and 4.5 mol % or less; and in a range of 10 nm or more and 200 nm or less in a pore distribution, a peak top diameter of a pore volume distribution is 20 nm or more and 120 nm or less, a pore volume is 0.2 ml/g or more and less than 0.5 ml/g, and a pore distribution width is 30 nm or more and 170 nm or less.

A zirconia powder containing a stabilizer, and having a specific surface area of 20 m.sup.2/g or more and 60 m.sup.2/g or less and a particle diameter D.sub.50 of 0.1 μm or more and 0.7 μm or less, in which in a range of 10 nm or more and 200 nm or less in a pore distribution based on a mercury intrusion method, a peak top diameter in a pore volume distribution is 20 nm or more and 85 nm or less, a pore volume is 0.2 ml/g or more and less than 0.5 ml/g, and a pore distribution width is 40 nm or more and 105 nm or less.

Passivated Li.sub.7La.sub.3Zr.sub.2O.sub.12 (LLZO) particles, tape casting powders and slip compositions including the particles, methods of forming the particles, methods of tape casting using the particles, green tapes including the particles, cast LLZO films formed from the particles, and lithium batteries including the cast LLZO film. A passivated LLZO particle includes an LLZO core, wherein the LLZO is optionally doped with one or more elements. The passivated LLZO particle also includes a shell including H-LLZO, H.sub.3O.sup.+-LLZO, and/or Li.sub.2CO.sub.3.