A hydrogen absorbing alloy negative electrode is provided. The hydrogen absorbing alloy negative electrode has a hydrogen absorbing alloy, and an additive including yttrium fluoride. A mass of the yttrium fluoride is 0.1 parts by mass or more and 0.2 parts by mass or less based on a hydrogen absorbing alloy powder of 100 parts by mass.

This invention provides a system and a method for safe production of electrolyte at required concentration on site on demand where occasionally only water is needed to be filled up. The system includes two main units: a saturated electrolyte unit and a diluted electrolyte unit.

A redox flow battery includes a redox flow cell and a supply and storage system external of the redox flow cell. The supply and storage system includes first and second electrolytes for circulation through the redox flow cell. The first electrolyte is a liquid electrolyte having electrochemically active manganese species with multiple, reversible oxidation states in the redox flow cell. The electrochemically active manganese species may undergo reactions that cause precipitation of manganese oxide solids. The first electrolyte includes an inhibitor that limits the self-discharge reactions. The inhibitor includes an oxoanion compound.

Aqueous electrolytes comprising fluorenone/fluorenol derivatives are disclosed. The electrolyte may be an anolyte for an aqueous redox flow battery. In some embodiments, the compound, or salt thereof, has a structure according to any one of formulas I-III ##STR00001##
where Q.sup.1-Q.sup.4 independently are CH, C(R.sup.1) or N, wherein 0, 1, or 2 of Q.sup.1-Q.sup.4 are N; Q.sup.5-Q.sup.8 independently are CH, C(R.sup.2), or N, wherein 0, 1, or 2 of Q.sup.5-Q.sup.8 are N; Y is C═O or C(H)OH; R.sup.1 and R.sup.2 independently are an electron withdrawing group; n is an integer >1; and x and y independently are 0, 1, 2, 3, or 4, where at least one of x and y is not 0.

An electrochemical cell comprises a can comprising a cylindrical side wall extending from a closed end wall. The closed end wall comprises a protrusion. The protrusion has a protrusion cavity therein. A pre-formed pellet of a first electrode material is disposed in the protrusion cavity. The electrochemical cell may further comprise a separator defining an inner cavity and separating the inner cavity from an outer cavity. The outer cavity is defined by the can and the separator. The electrochemical cell may further comprise a first electrode material disposed in the outer cavity; and a second electrode material disposed in the inner cavity.

Alkaline electrochemical cells are provided, wherein a conductive carbon is included in the cell's cathode in order to decrease resistivity of the cathode, so as to improve the discharge of the cell, particularly in high drain applications. The conductive carbon may comprise carbon nanotubes and/or graphene. Methods for preparing such cells are also provided.

The present technology provides a battery that includes an air cathode, an anode, an aqueous electrolyte that includes an amphoteric surfactant, and a housing that includes one or more air access ports defining a total area of void space (“vent area”), where (1) the battery is a size 13 metal-air battery and the total vent area defined by all of the air access ports is from about 0.050 mm.sup.2 to about 0.115 mm.sup.2; or (2) the battery is a size 312 metal-air battery and the total vent area defined by all of the air access ports is from about 0.03 mm.sup.2 to about 0.08 mm.sup.2.

A battery includes: an electrode group including an air electrode and a negative electrode that are stacked with a separator interposed therebetween; and a container housing the electrode group together with an alkaline electrolyte liquid. The air electrode includes a catalyst for an air electrode. This catalyst for an air electrode is a catalyst for an air electrode including an oxide containing at least bismuth (Bi), ruthenium (Ru), sodium (Na), and oxygen, and Na/(Ru+Bi+Na) representing an atomic ratio of the sodium to a sum of the bismuth, the ruthenium, and the sodium is 0.126 or more and 0.145 or less.

Disclosed is an aqueous electrolyte for redox flow battery, including a compound of formula (I)

##STR00001##

and/or an ion of compound (I), and/or a salt of compound (I), and/or a reduced form of the anthraquinone member of compound (I), wherein: X.sup.1, X.sup.2, X.sup.4, X.sup.5, X.sup.6, X.sup.7 and X.sup.8 are independently selected from the group consisting of a hydrogen atom, a linear, cyclic or branched, saturated or unsaturated, optionally substituted, hydrocarbon group including from 1 to 10 carbon atoms, a OH group and a —O-A-R.sup.1 group, A representing a linear, cyclic or branched, saturated or unsaturated, optionally substituted, hydrocarbon group including from 1 to 10 carbon atoms; R.sup.1 representing COOH or SO.sub.3H; wherein one and only one of X.sup.1, X.sup.2, X.sup.4, X.sup.5, X.sup.6, X.sup.7 and X.sup.8 is OH, and wherein one and only one of X.sup.1, X.sup.2, X.sup.4, X.sup.5, X.sup.6, X.sup.7 and X.sup.8 is —O-A-R.sup.1.

A battery includes an air cathode, an anode, an aqueous electrolyte, and a housing, wherein, the housing includes one or more air access ports defining a total vent area, the battery exhibit a current density, a ratio of current density to total vent area is greater than about 100 mA/mm.sup.2, and the aqueous electrolyte comprises an amphoteric fluorosurfactant.