35-Micrometer-thick zincophilic polyimide separator for energy-dense aqueous zinc-ion batteries

A 35 μm porous polyimide separator with a high tensile strength of 13.51 MPa was fabricated via vapor-induced phase separation, and plasma modification further improved wettability and Zn 2+ affinity, enabling uniform Zn deposition and dendrite suppression. • The synergistic combination of a hydrophobic polymer backbone and Zn 2+ -affinitive imide groups regulates ion transport and interfacial chemistry, yielding an impressive Zn 2+ transference number of 0.62. • Zinc-based cells equipped with the mPI separator exhibit ultralong cycling stability (1318 h at 1 mA cm -2 for symmetric cells) and significantly improved volumetric energy density (28.33 Wh L -1 for full cells). Aqueous zinc-ion batteries (AZIBs) have emerged as a promising technology for large-scale grid energy storage due to their intrinsic safety and low cost. However, their achievable energy density and cycling stability remain severely constrained by the lack of advanced separators. Herein, we report a polyimide-based separator (denoted as mPI) fabricated via vapor-induced phase separation combined with plasma surface treatment. The resulting separator features a uniform porous architecture, a thickness of only 35 μm, a high tensile strength of 13.51 MPa, a Young's modulus of 341.77 MPa, and an impressive Zn 2+ transference number of 0.62. In Zn||Zn symmetric cells, the mPI separator enables an extended cycling lifespan of 1318 h under 1 mA cm −2 and 1 mAh cm −2 . Moreover, Zn||Zn x V 2 O 5 full cells utilizing the mPI separator deliver a high specific capacity of 180.64 mAh g −1 and a capacity retention of 84.64% after 1000 cycles at 5 A g −1 . Notably, the full cells achieve a high volumetric energy density of 28.33 Wh L −1 when cycled at 0.5 A g −1 . This simple yet effective separator design offers valuable insights for the development of safe and high-performance AZIBs. A polyimide separator fabricated via vapor-induced phase separation and plasma modification enables regulated Zn 2+ transport and uniform deposition, thereby suppressing dendrites and side reactions while achieving high volumetric energy density. Download: Download high-res image (129KB) Download: Download full-size image