As of my last knowledge update in September 2021, flexible lithium-air (Li-Air) batteries were still in the experimental and research stages, and specific voltage ratings might not have been standardized or widely reported. Li-Air batteries are known for their potential high energy density due to the utilization of atmospheric oxygen as one of the reactants. However, they also face significant technical challenges related to stability, efficiency, and practical implementation.
For conventional lithium-ion batteries, the voltage is typically around 3.7 to 3.8 volts per cell. However, Li-Air batteries have the potential to achieve higher voltage outputs due to the oxygen reduction reaction at the cathode.
Please note that battery technology research is rapidly evolving, and new developments may have occurred since my last update. I recommend checking the latest scientific literature, research papers, and reputable sources for the most up-to-date information on flexible Li-Air battery technology and its voltage ratings.