There is provided an LDH separator including a porous substrate and a layered double hydroxide (LDH)-like compound that fills up pores of the porous substrate. The LDH-like compound is a hydroxide and/or an oxide with a layered crystal structure, containing (i) Ti, Y, and optionally Al and/or Mg, and (ii) at least one additive element M selected from the group consisting of In, Bi, Ca, Sr, and Ba.

There is provided an LDH separator including a porous substrate and a layered double hydroxide (LDH)-like compound that fills up pores of the porous substrate. The LDH-like compound is a hydroxide and/or an oxide with a layered crystal structure, containing (i) Ti, Y, and optionally Al and/or Mg, and (ii) at least one additive element M selected from the group consisting of In, Bi, Ca, Sr, and Ba.

According to one embodiment, a separator is provided. The separator includes a composite membrane. The composite membrane includes a substrate layer, a first composite layer, and a second composite layer. The first composite layer is located on one surface of the substrate layer. The second composite layer is located on the other surface of the substrate layer. The composite membrane has a coefficient of air permeability of 1×10.sup.−14 m.sup.2 or less. The first composite layer has a first surface and a second surface. The first surface is in contact with the substrate layer. The second surface is located on an opposite side to the first surface. Denseness of a portion including the first surface is lower than denseness of a portion including the second surface in the first composite layer.

According to one embodiment, a separator is provided. The separator includes a composite membrane. The composite membrane includes a substrate layer, a first composite layer, and a second composite layer. The first composite layer is located on one surface of the substrate layer. The second composite layer is located on the other surface of the substrate layer. The composite membrane has a coefficient of air permeability of 1×10.sup.−14 m.sup.2 or less. The first composite layer has a first surface and a second surface. The first surface is in contact with the substrate layer. The second surface is located on an opposite side to the first surface. Denseness of a portion including the first surface is lower than denseness of a portion including the second surface in the first composite layer.

A negative electrode for an alkaline battery cell which includes zinc-based particles, wherein less than 20% of the zinc-based particles, by weight relative to the total zinc in the electrode, have a particle size of greater than about 150 micrometers, is provided. An alkaline electrochemical cell that includes the negative electrode and a method for reducing the gassing of the electrochemical cell is also provided.

A negative electrode for an alkaline battery cell which includes zinc-based particles, wherein less than 20% of the zinc-based particles, by weight relative to the total zinc in the electrode, have a particle size of greater than about 150 micrometers, is provided. An alkaline electrochemical cell that includes the negative electrode and a method for reducing the gassing of the electrochemical cell is also provided.

An aqueous secondary battery including: a positive electrode; a negative electrode; a separator; and an aqueous electrolytic solution including water and a metal salt represented by Chemical Formula 1 A.sub.xD.sub.y and having molality of about 5 M to about 40 M wherein in Chemical Formula 1, A is at least one metal ion selected from a sodium ion, a potassium ion, a magnesium ion, a calcium ion, a strontium ion, a zinc ion, or a barium ion, D is at least one type of atomic group ion selected from Cl.sup.−, SO.sub.4.sup.2−, NO.sub.3.sup.−, ClO.sub.4.sup.−, SCN.sup.−, CF.sub.3SO.sub.3.sup.−, C.sub.4F.sub.3SO.sub.3.sup.−, (CF.sub.3SO.sub.2).sub.2N.sup.−, AlO.sub.2.sup.−, AlCl.sub.4.sup.−, AsF.sub.6.sup.−, SbF.sub.6.sup.−, BR.sub.4.sup.−, and PO.sub.2F.sub.2.sup.−, and 0<x≤2, and 0<y≤2.

In an aspect, provided is an alkaline rechargeable battery comprising: i) a battery container sealed against the release of gas up to at least a threshold gas pressure, ii) a volume of an aqueous alkaline electrolyte at least partially filling the container to an electrolyte level; iii) a positive electrode containing positive active material and at least partially submerged in the electrolyte; iv) an iron negative electrode at least partially submerged in the electrolyte, the iron negative electrode comprising iron active material; v) a separator at least partially submerged in the electrolyte provided between the positive electrode and the negative electrode; vi) an auxiliary oxygen gas recombination electrode electrically connected to the iron negative electrode by a first electronic component, ionically connected to the electrolyte by a first ionic pathway, and exposed to a gas headspace above the electrolyte level by a first gas pathway.

In an aspect, provided is an alkaline rechargeable battery comprising: i) a battery container sealed against the release of gas up to at least a threshold gas pressure, ii) a volume of an aqueous alkaline electrolyte at least partially filling the container to an electrolyte level; iii) a positive electrode containing positive active material and at least partially submerged in the electrolyte; iv) an iron negative electrode at least partially submerged in the electrolyte, the iron negative electrode comprising iron active material; v) a separator at least partially submerged in the electrolyte provided between the positive electrode and the negative electrode; vi) an auxiliary oxygen gas recombination electrode electrically connected to the iron negative electrode by a first electronic component, ionically connected to the electrolyte by a first ionic pathway, and exposed to a gas headspace above the electrolyte level by a first gas pathway.

Alkaline electrochemical cells are provided, wherein an organic additive is included in at least one component of the cell in order to increase electron discharge of the cathode, so as to improve the specific capacity of the cell. Methods for preparing such cells are also provided.