A positive electrode active material has a small difference in a crystal structure between the charged state and the discharged state. For example, the crystal structure and volume of the positive electrode active material, which has a layered rock-salt crystal structure in the discharged state and a pseudo-spinel crystal structure in the charged state at a high voltage of approximately 4.6 V, are less likely to be changed by charging and discharging as compared with those of a known positive electrode active material. In order to form the positive electrode active material having the pseudo-spinel crystal structure in the charged state, it is preferable that a halogen source such as a fluorine and a magnesium source be mixed with particles of a composite oxide containing lithium, a transition metal, and oxygen, which is synthesized in advance, and then the mixture be heated at an appropriate temperature for an appropriate time.

A positive electrode active material has a small difference in a crystal structure between the charged state and the discharged state. For example, the crystal structure and volume of the positive electrode active material, which has a layered rock-salt crystal structure in the discharged state and a pseudo-spinel crystal structure in the charged state at a high voltage of approximately 4.6 V, are less likely to be changed by charging and discharging as compared with those of a known positive electrode active material. In order to form the positive electrode active material having the pseudo-spinel crystal structure in the charged state, it is preferable that a halogen source such as a fluorine and a magnesium source be mixed with particles of a composite oxide containing lithium, a transition metal, and oxygen, which is synthesized in advance, and then the mixture be heated at an appropriate temperature for an appropriate time.

Provided is a cathode active material for a non-aqueous electrolyte secondary battery capable of obtaining high initial discharge capacity and good output characteristics at low temperature. In order to achieve this, a cathode active material that is a lithium nickel composite oxide composed of secondary particles that are an aggregate of primary particles is expressed by the general expression: Li.sub.w(Ni.sub.1-x-yCo.sub.xAl.sub.y).sub.1-zM.sub.zO.sub.2 (where 0.98w1.10, 0.05x0.3, 0.01y0.1, 0z0.05, and M is at least one metal element selected from a group consisting of Mg, Fe, Cu, Zn and Ga), and where the crystallite diameter at (003) plane of that lithium nickel composite oxide that is found by X-ray diffraction and the Scherrer equation is within the range of 1200 to 1600 is used as the cathode material.

Methods of making high-energy cathode active materials for primary alkaline batteries are described. The primary batteries include a cathode having an alkali-deficient nickel(IV)-containing oxide including one or more metals such as Co, Mg, Al, Ca, Y, Mn, and/or non-metals such as B, Si, Ge or a combination of metal and/or non-metal atoms as dopants partially substituted for Ni and/or Li in the crystal lattice; an anode; a separator between the cathode and the anode; and an alkaline electrolyte solution.

A lithium metal oxide powder for a cathode material in a rechargeable battery comprises a core and a surface layer. The surface layer is delimited by an outer and an inner interface. The inner interface is in contact with the core. The cathode material has a layered crystal structure comprising the elements Li, M, and oxygen. M has the formula M=(Ni.sub.z(Ni.sub.1/2 Mn.sub.1/2).sub.y Co.sub.x).sub.1-k A.sub.k, with 0.15x0.30, 0.20z0.55, x+y+z=1 and 0<k0.1. The Li content is stoichiometrically controlled with a molar ratio 0.95Li:M1.10. A is at least one dopant and comprises Al. The core at the inner interface has an Al content of 0.3-3 mol %. The surface layer comprises an intimate mixture of Ni, Co, Mn, LiF and Al.sub.2O.sub.3 determined by XPS. The surface layer has a Mn content that decreases from the Mn content at the inner interface to less than 50% of the Mn content at the outer interface.

A lithium metal oxide powder for a cathode material in a rechargeable battery comprises a core and a surface layer. The surface layer is delimited by an outer and an inner interface. The inner interface is in contact with the core. The cathode material has a layered crystal structure comprising the elements Li, M, and oxygen. M has the formula M=(Ni.sub.z(Ni.sub.1/2 Mn.sub.1/2).sub.y Co.sub.x).sub.1-k A.sub.k, with 0.15x0.30, 0.20z0.55, x+y+z=1 and 0<k0.1. The Li content is stoichiometrically controlled with a molar ratio 0.95Li:M1.10. A is at least one dopant and comprises Al. The core at the inner interface has an Al content of 0.3-3 mol %. The surface layer comprises an intimate mixture of Ni, Co, Mn, LiF and Al.sub.2O.sub.3 determined by XPS. The surface layer has a Mn content that decreases from the Mn content at the inner interface to less than 50% of the Mn content at the outer interface.

A method of preparing cathode active material precursors includes feeding a first reaction liquid into a first Couette-Taylor reactor and performing a co-precipitation reaction to continuously form and output a first product liquid stream containing a plurality of core particles; feeding the first product liquid stream into a second Couette-Taylor reactor that is connected in series after the first Couette-Taylor reactor; and feeding a second reaction liquid into the second Couette-Taylor reactor to react with the core particles, so as to form the cathode active material precursors. The first reaction liquid is a multi-element metal solution, the second reaction liquid is a transition metal aqueous solution, and each of the cathode active material precursors has a core-shell structure.

The invention relates to O3/P2 mixed-phase sodium-containing doped layered oxide materials which comprise a mixture of a first phase with an O3-type structure and a second phase with a P2-type structure; wherein the O3:P2 mixed-phase sodium-containing doped layered oxide material has the general formula: Na.sub.aA.sub.bM.sup.1.sub.c M.sup.2 M.sup.3.sub.eM.sup.4.sub.f M.sup.5 O.sub.2. The invention also provides a process for making such O3/P2 mixed-phase sodium-containing doped layered oxide materials, and use applications therefor.

The invention relates to O3/P2 mixed-phase sodium-containing doped layered oxide materials which comprise a mixture of a first phase with an O3-type structure and a second phase with a P2-type structure; wherein the O3:P2 mixed-phase sodium-containing doped layered oxide material has the general formula: Na.sub.aA.sub.bM.sup.1.sub.c M.sup.2 M.sup.3.sub.eM.sup.4.sub.f M.sup.5 O.sub.2. The invention also provides a process for making such O3/P2 mixed-phase sodium-containing doped layered oxide materials, and use applications therefor.

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.