Abstract
The batteries that power untethered underwater vehicles (UUVs) serve a single purpose: to provide energy to electronics and motors; the more energy required, the bigger the robot must be to accommodate space for more energy storage. By choosing batteries composed primarily of liquid media [e.g., redox flow batteries (RFBs)], the increased weight can be better distributed for improved capacity with reduced inertial moment. Here, we formed an RFB into the shape of a jellyfish, using two redox chemistries and architectures: (i) a secondary ZnBr(2) battery and (ii) a hybrid primary/secondary ZnI(2) battery. A UUV was able to be powered solely by RFBs with increased volumetric (Q ~ 11 ampere-hours per liter) and areal (108 milliampere-hours per square centimeter) energy density, resulting in a long operational lifetime (T ~ 1.5 hours) for UUVs composed of primarily electrochemically energy-dense liquid (~90% of the robot's weight).