Separator for alkaline secondary battery, method for preparing the same and alkaline secondary battery

In an alkaline secondary battery provided with a positive electrode, a negative electrode, a separator to be interposed between the positive electrode and the negative electrode, and an alkaline electrolyte solution, the above-mentioned separator has double bond of carbon. Further, an average amount of double bond of carbon in the gram of separator is in the range of 10 µmol/g to 200 µmol/g, and an average amount of increased nitrogen in the gram of separator after the separator is immersed in an alkaline aqueous solution having ammonium salt dissolved therein is not less than 140 µg/g.