As of my last knowledge update in September 2021, flexible lithium-titanate (Li4Ti5O12) batteries were not as commonly known or available as other types of lithium-ion batteries. Lithium-titanate batteries are known for their fast charging capabilities, long cycle life, and safety features. However, flexible versions of these batteries might have different specifications depending on the manufacturer and advancements in battery technology.
Typically, the voltage rating of a lithium-titanate battery is around 2.4 to 2.8 volts per cell. This is lower than the voltage of traditional lithium-ion batteries, which usually operate around 3.6 to 3.7 volts per cell. It's important to note that battery technology is constantly evolving, and new developments may have occurred since my last update. I recommend checking with battery manufacturers or reliable sources for the most up-to-date information on the voltage rating of flexible lithium-titanate batteries.