Zinc metal based aqueous batteries are actively explored as promising alternatives to lithium rechargeable batteries owing to their benefits in cost, safety, nontoxicity, and abundance. Zinc dendrite growth and resultant short lifespan are, however, major issue to overcome. Here, we propose a strategy to suppress the zinc dendrite growth by designing an ionic transport regulating membrane separator. The membrane is synthesized by reacting a low cost polyacrylonitrile with lithium polysulfide followed by hydrolysis. The reaction with lithium polysulfide leads to both cross-linking and functionalization of the polymer by sulfur containing groups. Hydrolysis results in a membrane with preferred cation transport and uniform ionic flux distribution. The membrane is mechanically robust and can be cast as 30 micron-meter-thick films. The membrane separator enables effective dendrite suppression and long cyclability of Zn/Zn symmetric cells.