As of my last knowledge update in September 2021, flexible lithium-air (Li-Air) batteries were still largely in the research and development phase, and there wasn't a standardized voltage rating for them. However, I can provide you with some general information about Li-Air batteries.
Lithium-air batteries are known for their theoretical high energy density, which could potentially offer much higher energy storage capabilities compared to traditional lithium-ion batteries. They work by using lithium metal as one electrode and ambient air as the other electrode. Oxygen from the air reacts with lithium ions to generate electrical energy.
The voltage of a lithium-air battery would depend on various factors, including the specific materials used, the design of the battery, and the operating conditions. In general, the voltage of a Li-Air battery would likely be in a similar range to other lithium-based batteries, such as lithium-ion batteries, which typically operate at voltages of around 3.7 to 4.2 volts per cell.
Please note that the field of battery technology is rapidly evolving, and there may have been developments in flexible Li-Air batteries since my last update. I recommend checking more recent sources or research papers for the most up-to-date information on the voltage ratings of flexible Li-Air batteries.