Nickel electrodes for alkaline secondary battery and alkaline secondary batteries

Abstract

A nickel electrode for alkaline secondary battery including a porous sintered nickel substrate loaded with a nickel hydroxide-based active material, the nickel electrode has a configuration wherein a surface portion of the active material loaded into the sintered nickel substrate is provided with a combination of a first coating layer of a suitable compound and a second coating layer of a suitable compound, or a coating layer of a compound of two or more suitable elements, or wherein the coating layer of two or more suitable elements is formed between the sintered nickel substrate and the active material.

What is claimed is:  
     
         1 . A nickel electrode for alkaline secondary battery including a porous sintered nickel substrate loaded with a nickel hydroxide-based active material, the nickel electrode comprising a first coating layer of cobalt compound laid on a surface portion of the active material loaded into the sintered nickel substrate; and a second coating layer laid on the first coating layer and based on a compound of at least one element selected from the group consisting of nickel, magnesium, calcium, barium, strontium, scandium, yttrium, lanthanide and bismuth.  
     
     
         2 . The nickel electrode for alkaline secondary battery as claimed in  claim 1 , wherein the lanthanide in said second coating layer is comprised of at least one element selected from the group consisting of lanthanum, cerium, praseodymium, neodymium, samarium, europium and ytterbium.  
     
     
         3 . The nickel electrode for alkaline secondary battery as claimed in  claim 1 , wherein the compound in said second coating layer is comprised of a hydroxide, an oxide, or a mixture of these.  
     
     
         4 . The nickel electrode for alkaline secondary battery as claimed in  claim 1 , wherein the compound in the second coating layer contains said element in concentrations of 0.05 to 5 wt % based on the total weight of said active material, and first and second coating layers.  
     
     
         5 . The nickel electrode for alkaline secondary battery as claimed in  claim 1 , wherein the cobalt compound in the first coating layer contains cobalt in concentrations of 0.05 to 5 wt % based on the total weight of said active material, and first and second coating layers.  
     
     
         6 . An alkaline secondary battery employing the nickel electrode for alkaline secondary battery of  claim 1  as its positive electrode.  
     
     
         7 . A nickel electrode for alkaline secondary battery including a porous sintered nickel substrate loaded with a nickel hydroxide-based active material, the nickel electrode comprising a first coating layer of cobalt compound laid on a surface portion of the active material loaded into the sintered nickel substrate; and a second coating layer laid on the first coating layer and based on a complex compound of cobalt and at least one element selected from the group consisting of nickel, magnesium, calcium, barium, strontium, scandium, yttrium, lanthanide and bismuth.  
     
     
         8 . The nickel electrode for alkaline secondary battery as claimed in  claim 7 , wherein the lanthanide in said second coating layer is comprised of at least one element selected from the group consisting of lanthanum, cerium, praseodymium, neodymium, samarium, europium and ytterbium.  
     
     
         9 . The nickel electrode for alkaline secondary battery as claimed in  claim 7 , wherein the complex compound in said second coating layer is comprised of a hydroxide, an oxide or a mixture of these.  
     
     
         10 . The nickel electrode for alkaline secondary battery as claimed in  claim 7 , wherein the complex compound in the second coating layer contains the above elements (including cobalt) in concentrations of 0.05 to 5 wt % based on the total weight of said active material, and first and second coating layers.  
     
     
         11 . The nickel electrode for alkaline secondary battery as claimed in  claim 7 , wherein the cobalt compound in the first coating layer contains, cobalt in concentrations of 0.05 to 5 wt % based on the total weight of said active material, and first and second coating layers.  
     
     
         12 . An alkaline secondary battery employing the nickel electrode for alkaline secondary battery of  claim 7  as its positive electrode.