Outstanding Rechargeable Aqueous Lithium–Air Battery With Water-Stable Lithium Conducting Polymer Electrolyte Separator

Next-generation energy storage, aqueous lithium–air batteries emerge as a strong candidate, particularly for electric vehicle applications, due to their inherently high energy and power characteristics and their ability to function without stringent environmental control. A key component enabling this system is the separator, which must effectively isolate the anolyte from the catholyte while ensuring stable operation and safety. In this work, an ultrathin (< 10 μm), water-blocking polymer membrane capable of conducting lithium ions was fabricated, exhibiting an ionic conductivity in the range of 2 × 10−6 to 3 × 10−6 S cm−1 at 25°C. The experimental cell consisted of a lithium metal electrode, a 4.5 M LiFSI solution in 1,2-diethoxyethane as the anolyte, the fabricated polymer separator, a 1 M LiOH–10 M LiCl catholyte, and a carbon-based air electrode. The assembled battery produced an open-circuit voltage of about 3 V, which is in good agreement with predicted thermodynamic values and with earlier studies on aqueous Li–air cells employing ceramic membranes. Depending on the separator type, the measured cell resistance at 25°C was within 300 to 1500 Ω·cm2. Under a current density of 0.5 mA·cm−2 and a capacity limit of 0.5 mAh·cm−2, the cell was capable of operating stably for more than 200 cycles at room temperature.