Controllable Ion-Release Separator: In-Situ Engineering of Zincophilic/Hydrophobic Interface and Solvation Regulation for Durable Zn Metal Anode

Aqueous zinc-ion batteries (AZIBs) are popular for their safety, affordability, and environmental friendliness. However, irreversible electrochemical processes at the zinc anode limit their longevity, especially in mildly acidic electrolytes. Traditional approaches including protective artificial interfaces and electrolyte engineering with functional additives, face limitations due to rapid electrolyte consumption and regulatory effectiveness diminishment over time. To overcome these challenges, we have developed a thin copper acetate/polyacrylonitrile composite (CPAN) fibrous film (37 µm) inspired by diffusion-controlled drug release systems. This innovative separator ensures the continuous and controllable release of copper ions (Cu 2+ ) and acetate ions (Ac -). The Cu 2+ promotes the formation of a zincophilic-hydrophobic Cu/Zn alloy interface on the zinc anode, effectively suppressing dendrite growth and hydrogen evolution. Ac -, in conjunction with the cyano groups in PAN, regulates the solvation structure of Zn 2+ and accelerates its desolvation. As a result, the CPAN separator significantly enhances the reversibility of zinc stripping and plating, allowing for stable cycling over 1500 hours. The assembled MnO 2 ||Zn pouch cell exhibits a high capacity of 45 mAh and stable cycling for over 300 cycles even under a lean electrolyte condition (E/C ratio=25.88 μL mAh -1 ) and a limited Zn supply (N/P ratio=3).