Bioinspired ion transport membranes have been extensively researched for energy storage applications. Sulfur, due to its natural abundance, low toxicity, high theoretical specific energy density (2600 Wh/kg), and high specific capacity (1675 mA/g), is attracting significant attention as an alternative battery system to replace traditional lithium-ion batteries that have limitations in terms of safety, capacity, and energy density in various applications. However, polysulfide dissolution and shuttling pose challenges that prevent the mass commercialization of metal sulfur batteries. We have developed a practical and comprehensive approach for developing high-performance metal sulfur batteries inspired by biological ion transport mechanisms. We used aramid nanofiber (ANF)-based composite ion transport membranes that prevent dendrite formation and confine polysulfides on the cathode side. ANF composite battery separators provide diverse and opposing properties, including high mechanical properties, high ionic conductivity, and high thermal/chemical stability. These biomimetic separators have highly selective ion-sieving properties that make the batteries safe and high-performing. It is crucial to fabricate such biocompatible, affordable, flexible, and high-energy-density batteries to power next-generation electronics such as portable, wearable, and implantable biomedical devices.