A cathode composition for a lithium-ion cell or battery of the general formula: Li.sub.1+xMn.sub.1−xO.sub.2, wherein the composition is in the form of a single phase having a rock salt crystal structure such that an x-ray diffraction pattern of the composition has an absence of peaks below a 20 value of 35; and the value of x is greater than 0, and equal to or less than 0.3. The compound is also formulated into a positive electrode, or cathode, for use in an electrochemical cell.

A lithium ion conductive solid electrolyte contains a lithium ion conductive powder having a garnet-type crystal structure including at least Li, La, Zr, and O, and a lithium ion conductive polymer. The lithium ion conductive solid electrolyte can maintain its shape without use of an additional polymer different from the lithium ion conductive polymer. The lithium ion conductive solid electrolyte exhibits an activation energy of 30 kJ/mol or less at 20° C. to 80° C.

A cathode active material for a lithium secondary battery includes a core portion comprising a lithium metal oxide particle, and a coating layer at least partially covering a surface of the core portion and including a lithium boron composite oxide. The lithium boron composite oxide is included in an amount from 100 ppm to 1,500 ppm based on a total weight of the cathode active material. A lithium secondary battery having improved structural stability and electrical property is provided using the cathode active material.

A membrane electrode assembly of an electrochemical device includes a proton conductive solid electrolyte membrane and an electrode including Ni and an electrolyte material which contains as a primary component, at least one of a first compound having a composition represented by BaZr.sub.1-x1M.sup.1.sub.x1O.sub.3 (M.sup.1 represents at least one element selected from trivalent elements each having an ion radius of more than 0.720 A° to less than 0.880 A°, and 0<x.sub.1<1 holds) and a second compound having a composition represented by BaZr.sub.1-x2Tm.sub.x2O.sub.3 (0<x.sub.2<0.3 holds).

A nickel-based hydroxide powder is provided which has an average crystallite size, as determined by Scherrer fitting of the (00I) reflections of an XRD powder diffraction pattern of the nickel-based hydroxide powder, of at most 10 nm, together with a process for producing nickel-based hydroxide powders. The nickel-based hydroxide powders find utility as precursors for the formation of lithium transition metal oxide active electrode materials.

Disclosed are novel precursor particles for preparing a cathode active material including transition metal precursor particles containing one or more transition metals, and one or more of an alkali metal and an alkaline earth metal, wherein the alkali metal and the alkaline earth metal are contained in one or more of inner and outer parts of the transition metal precursor particles, and a novel precursor powder including the novel precursor particles.

A method for relithiating cathode material from spent lithium-based batteries, the method comprising: (i) mixing delithiated cathode material and a lithium salt with an ionic liquid in which the lithium salt is at least partially soluble to form an initial mixture; (ii) heating the initial mixture to a temperature of 100° C. to 300° C. to result in relithiation of the delithiated cathode material; and (iii) separating the ionic liquid from the relithiated cathode material; wherein, in embodiments, the cathode material is a lithium metal oxide, wherein the metal is selected from the group consisting of Ni, Co, Fe, Mn, Al, Zr, Ti, Nb, and combinations thereof, or wherein the cathode material has the formula LiNi.sub.xMn.sub.yCo.sub.zO.sub.2, wherein x>0, y>0, z>0, and x+y+z=1; wherein, in some embodiments, the ionic liquid has a nitrogen-containing cationic portion, such as an imidazolium ionic liquid.

Cathode active material in particulate form with a mean particle diameter in the range from 2 to 16 .Math.m (D50), wherein the cathode active material has the composition Li.sub.1+xTM.sub.1-xO.sub.2 wherein x is in the range of from 0.1 to 0.2 and TM is a combination of elements according to general formula (I), (Ni.sub.aCo.sub.bMn.sub.c).sub.1-d-eM.sup.1.sub.dM.sup.2.sub.e where the variables are each defined as follows: a is in the range from 0.20 to 0.40, b is in the range of from zero to 0.15, c is in the range of from 0.50 to 0.75, d is in the range of from zero to 0.015, and e is in the range of from zero to 0.02, M.sup.1 is selected from Al, Ti, Zr, Mo, W, Fe, Nb, and Mg, M.sup.2 is selected from B and K, with a + b + c = 1.0 wherein said composite oxide has a specific surface (BET) in the range from 0.5 m.sup.2/gto 10 m.sup.2/gand a pressed density of at least 2.9 g/cm.sup.3, and wherein said cathode active material has an average primary particle diameter in the range of from 200 to 3,000 nm.

A positive electrode active material with little deterioration is provided. Positive electrode active material particles with little deterioration are provided. A power storage device with little deterioration is provided. A highly safe power storage device is provided. A novel power storage device is provided. A secondary battery includes a positive electrode and a negative electrode. In the secondary battery, the positive electrode includes a positive electrode active material; the positive electrode active material includes a crystal exhibiting a layered rock-salt crystal structure; the crystal is represented by the space group R-3m; the positive electrode active material is a particle containing lithium, cobalt, titanium, magnesium, and oxygen; the concentration of the magnesium in a surface portion of the particle is higher than the concentration of the magnesium in an inner portion of the particle; and in the positive electrode active material, the concentration of the titanium in the surface portion of the particle is higher than the concentration of the titanium in the inner portion of the particle.

A cathode composition for a lithium-ion cell or battery of the general formula: Li.sub.1+xMn.sub.1−xO.sub.2, wherein the composition is in the form of a single phase having a rock salt crystal structure; and the value of x is greater than 0, and equal to or less than 0.3. The compound is also formulated into a positive electrode, or cathode, for use in an electrochemical cell.