Metal-Air Power Sources With Hydrogel Electrolytes For Long Endurance Robots

To power electronics for long durations, batteries need to be recharged because they store only a small amount of total energy, which is limited by the mass of energy storage materials in the battery electrodes. Harvesters can provide longer continuous energy, but their limited power and need for precise operating conditions severely restricts their application in off-grid robots, microelectronics, and internet connected devices. In this dissertation, we designed a new strategy for powering robots and electronics by electrochemically scavenging energy from metal surfaces, which breaks energy storage scaling laws by allowing robots and electronics to extract energy from large volumes of energy dense material without having to carry the material on-board. When moving across a metal surface, metal scavenging exceeds the energy densities of lithium ion and metal-air batteries by 13x and 2x. We also showed how the same technology can power a vehicle and make computer-free decisions about how to navigate the vehicle’s environment by responding to chemical features through electro-chemotaxis. To minimize the mass loading and cost of catalysts in the air cathode and improve their stability, we synthesized nanoporous gold catalysts with increased (100) surface facets using electrochemical dealloying in sodium citrate surfactant electrolytes. These modified nanoporous gold catalysts achieved a 7.7% higher operating voltage and 30.2% greater power density in aluminum-air batteries over traditionally prepared nanoporous gold, and their performance was superior to commercial platinum nanoparticle electrodes at a 10 times lower mass loading. We investigated morphology changes and material distribution through the anode using microscale X-ray computed tomography (micro-CT) and Focused Ion Beam Scanning Electron Microscopy (FIB-SEM). In addition, we also synthesized poly (vinyl alcohol (PVA)/SiO2 and PVA/Agarose hydrogel to increase water retention to extend the lifetime of the hydrogel, which can significantly contribute to the long duration application of metal-air batteries.