Electrode protection in electrochemical cells, and more specifically, electrode protection in both aqueous and non-aqueous electrochemical cells, including rechargeable lithium batteries, are presented. Advantageously, electrochemical cells described herein are not only compatible with environments that are typically unsuitable for lithium, but the cells may be also capable of displaying long cycle life, high lithium cycling efficiency, and high energy density.

A hydrogen storing alloy containing only a few impurities leading to a short circuit where the yield can be maintained even when the alloy is subjected to magnetic separation treatment. A hydrogen storing alloy includes a matrix phase having an AB5 type crystal structure, the alloy having a misch metal (referred to as “Mm”) in an A-site in an ABx composition and having any one or at least one of Ni, Al, Mn, and Co in a B-site in the ABx composition, wherein the ratio (referred to as “ABx”) of the total number of moles of elements comprising the B site to the total number of moles of elements comprising the A site is 5.00<ABx≦5.40; the content of Co is more than 0.0 mol % and less than 0.7 mol %; and residual magnetization is more than 0 emu/g and 0.020 emu/g or less.

A hydrogen storage alloy suitable for a negative electrode of an on-board alkaline storage battery, an alkaline storage battery using this hydrogen storage alloy, and a vehicle; wherein a fine-grained hydrogen storage alloy is used for an alkaline storage battery that has a crystal structure of an A.sub.2B.sub.7-type structure as a main phase and is represented by a general formula: (La.sub.1-aSm.sub.a).sub.1-bMg.sub.bNi.sub.cAl.sub.dCr.sub.e (where suffixes a, b, c, d, and e meet the following conditions: 0≤a≤0.35, 0.15≤b≤0.30, 0.02≤d≤0.10, 0≤e≤0.10, 3.20≤c+d+e≤3.50, and 0<a+e), and an alkaline storage battery using this hydrogen storage alloy for a negative electrode. A vehicle also includes this alkaline storage battery as an electricity supply source for a motor.

Provided is a core/shell composite that includes a core portion containing a heat resistant material selected from an inorganic oxide, a ceramic, a mineral and the like and having rigidity, and at least one layer of shell portion containing a hydrogen absorbing/desorbing metal covering the entire or a part of the core portion. The heat resistant material contained in the core portion has a melting point higher than the highest melting point among the hydrogen absorbing/desorbing metal contained in the shell portion. In a method for producing the core/shell composite, the core portion is covered with the shell portion by deposition in the absence of oxygen.

The present invention relates to a hydrogen storage alloy, an electrode for a Ni-MH battery, a secondary battery, and a method for preparing the hydrogen storage alloy. The chemical composition of the hydrogen storage alloy is expressed by the general formula La.sub.(3.0˜3.2)xCe.sub.xZr.sub.ySm.sub.(1−(4.11˜4.2)x−y)Ni.sub.zCo.sub.uMn.sub.vAl.sub.w, where x, y, z, u, v, w are molar ratios, and 0.14≤x≤0.17, 0.02≤y≤0.03, 4.60≤z+u+v+w≤5.33, 0.10≤u≤0.20, 0.25≤v≤0.30, and 0.30≤w≤0.40. The atomic ratio of the metal lanthanum (La) to the metal cerium (Ce) is fixed at 3.0 to 3.2, which satisfies the requirements of the overcharge performance of the electrode material. A side elements are largely substituted by samarium (Sin) element, that is, the atomic ratio of Sin on the A side is 25.6% to 42%, so as to solve the problem of shortened cycle life caused by the small amount of cobalt (Co) atoms. The equilibrium pressure is adjusted by the change in the ratio of Sin to La and Ce to satisfy the requirements of the charge and discharge dynamic performance of the electrode material. The nucleation rate of the solidification process is improved by the addition of zirconium (Zr) to the A side at an atomic ratio of 2% to 3%. The Ni-MH battery negative-electrode material obtained from the hydrogen storage alloy has high overcharge resistance, and good high-rate discharge performance and cycle stability.

A composition of general formula (1): Na.sub.x[Mn.sub.aNi.sub.bCr.sub.c]O.sub.2+y (1), wherein: 0.6≤x≤0.8; −0.1≤y≤0.1; 0.55≤a≤0.7; 0.25≤b≤0.3; c≤0.05; and a+b+c≤1.0, an intermediate product for preparing a composition of general formula (1) and a process of synthesis, wherein the mixed sodium-transition metal oxide of general formula (1) may generally show an essentially or solely P2 structure, and may be used as a positive electrode material for a sodium ion secondary battery.

A hydride secondary battery includes: a pressure vessel; a positive electrode disposed in the pressure vessel; a negative electrode disposed in the pressure vessel; and hydrogen gas with which the pressure vessel is filled. The negative electrode contains a hydrogen-absorbing alloy. In a pressure-composition-temperature diagram, a desorption curve at 25 C. of the hydrogen-absorbing alloy has a plateau pressure of 0.15 MPa or more and 10 MPa or less. The hydrogen gas has a pressure equal to or higher than the plateau pressure at 25 C. of the hydrogen-absorbing alloy.

A nickel hydrogen secondary battery accommodates an electrode group including a positive electrode and a negative electrode which are stacked one on top of another through a separator, together with an alkaline electrolyte. The battery contains Li, with a total amount of Li in the battery 2 of 15 to 50 mg/Ah, as determined as the mass in terms of LiOH per Ah of the positive electrode capacity. The negative electrode includes particles of rare earth-MgNi-based hydrogen storage alloy which contains a rare earth element, Mg and Ni. The hydrogen storage alloy particles 44 includes, on the surface thereof, a rare earth hydroxide which is the hydroxide of a rare earth element and has a specific surface area of 0.1 to 0.5 m.sup.2/g.

A nickel-metal hydride battery is provided with a positive electrode and a negative electrode including hydrogen absorbing alloys. The hydrogen absorbing alloys of the negative electrode include a first hydrogen absorbing alloy and a second hydrogen absorbing alloy having a higher hydrogen equilibrium dissociation pressure than the first hydrogen absorbing alloy. Each hydrogen absorbing alloy includes an element A having high affinity for hydrogen and an element B having low affinity for hydrogen. The ratio of a substance amount of the element B to a substance amount of the element A is greater in the second hydrogen absorbing alloy than the first hydrogen absorbing alloy.

An alkaline secondary battery includes at least a case, a positive electrode, a negative electrode, and an electrolyte solution. The case accommodates the positive electrode, the negative electrode, and the electrolyte solution. The positive electrode includes manganese dioxide and nickel hydroxide. The negative electrode includes a hydrogen storage alloy.