Acrylic Acid-Sodium Styrene Sulfonate Copolymer as a Separator for Alkaline Electrochemical Systems

摘要

A new polymeric separator membrane has been developed for primary and secondary alkaline electrochemical systems. The objective of this research is to minimize the separator volume in the cell through the use of an easily processed polymeric membrane. Such a membrane must provide adequate ionic conductivity while preventing the diffusion of reaction products and other undesirable soluble species between electrodes. A water-soluble copolymer of acrylic acid and sodium styrene sulfonate monomers (PAASS) has been developed as an alkaline separator membrane. The monomer ratio is varied to manipulate electrolyte absorption and ionic resistivity of the copolymer. Processes have been developed to coat PAASS onto conventional non-woven separator papers to produce composite membranes. The monomer ratio and the coating weight can be adjusted to balance ionic resistivity and shorting protection to provide adequate overall performance. PAASS coated separators demonstrate good barrier properties to soluble zincate and silver species. The combination of good ionic conductivity, chemical stability, and barrier properties appears to be unique to PAASS separator materials. Preliminary use of PAASS separator materials in a rechargeable Zn/air system shows a significant improvement in shorting protection over microporous materials such as Celgard® 3401. Through improved cycle life and shelf life, the PAASS separator should enable improved performance in primary or secondary alkaline systems.