As of my last knowledge update in September 2021, the specific voltage rating of a flexible lithium-sulfur (Li-S) battery can vary depending on the design and configuration of the battery. However, Li-S batteries typically have a nominal voltage of around 2.1 to 2.3 volts per cell. This is lower than the typical 3.6 to 3.7 volts per cell for lithium-ion batteries, which are more commonly used in consumer electronics.
Please note that battery technology is rapidly evolving, and there may have been developments since my last update. I recommend checking with current and reliable sources or manufacturers for the most up-to-date information on the voltage rating of flexible Li-S batteries.