Hydroxide-ion-conductive dense membrane and composite material

Abstract

Provided is a hydroxide-ion-conductive dense membrane having a He permeability per unit area of 10 cm/min·atm or less. The present invention provides a highly-densified hydroxide-ion-conductive membrane that can significantly reduce permeation of substances other than hydroxide ions (in particular, Zn, which may cause growth of dendritic zinc in a zinc secondary battery) and that is particularly suitable for use in, for example, a separator for a battery (in particular, a zinc secondary battery, which may cause growth of dendritic zinc).

What is claimed is: 
     
         1 . A separator for a zinc secondary battery comprising a composite material including a porous substrate and a hydroxide-ion-conductive dense membrane disposed on at least one surface of the porous substrate, the hydroxide-ion-conductive dense membrane consisting of a layered double hydroxide dense membrane and having a He permeability per unit area of 10 cm/min-atm or less,
 wherein the layered double hydroxide dense membrane is formed from a stock solution containing at least two cations that are different from one another.   
     
     
         2 . The separator for a zinc secondary battery according to  claim 1 , wherein the hydroxide-ion-conductive dense membrane has a He permeability is 1.0 cm/min·atm or less. 
     
     
         3 . The separator for a zinc secondary battery according to  claim 1 , wherein the hydroxide-ion-conductive dense membrane has a Zn permeability per unit area of 10 m −2 ·h −1  or less as determined by the contact of the membrane with water. 
     
     
         4 . The separator for a zinc secondary battery according to  claim 3 , wherein the hydroxide-ion-conductive dense membrane has a Zn permeability is 1.0 m −2 ·h −1  or less. 
     
     
         5 . The separator for a zinc secondary battery according to  claim 1 , wherein the layered double hydroxide is represented by the formula: M 2+   1-x M 3+   x (OH) 2 A n−   x,n .mH 2 O where M 2+  represents a divalent cation, M 3+  represents a trivalent cation, A n−  represents an n-valent anion, n represents an integer of 1 or more, x is 0.1 to 0.4, and m is 0 or more. 
     
     
         6 . The separator for a zinc secondary battery according to  claim 5 , wherein, in the formula, M 2+  comprises Mg 2+ , M 3+  comprises Al 3+ , and A n−  comprises OH −  and/or CO 3   2− . 
     
     
         7 . The separator for a zinc secondary battery according to  claim 1 , wherein the layered double hydroxide comprises an agglomeration of platy particles, and the platy particles are oriented such that the tabular faces of the platy particles are substantially perpendicular to or oblique to the surface of the dense membrane. 
     
     
         9 . The separator for a zinc secondary battery according to  claim 1 , wherein the hydroxide-ion-conductive dense membrane has a thickness of 100 μm or less. 
     
     
         10 . The separator for a zinc secondary battery according to  claim 1 , wherein the porous substrate comprises at least one material selected from the group consisting of ceramic materials, metal materials, and polymer materials. 
     
     
         11 . The separator for a zinc secondary battery according to  claim 10 , wherein the porous substrate is composed of a ceramic material, wherein the ceramic material is at least one selected from the group consisting of alumina, zirconia, titania, magnesia, spinel, calcia, cordierite, zeolite, mullite, ferrite, zinc oxide, and silicon carbide. 
     
     
         12 . The separator for a zinc secondary battery according to  claim 1 , wherein the porous substrate has an average pore size of 0.001 to 1.5 μm. 
     
     
         13 . The separator for a zinc secondary battery according to  claim 1 , wherein the surface of the porous substrate has a porosity of 10 to 60%. 
     
     
         14 . A zinc secondary battery including the separator comprising the composite material according to  claim 1 .