Understanding electrochemically induced surface evolution and transport at metal-hydrogel interfaces for metal-air scavenger power sources
Abstract
The goal of this research is to enable an entirely new way to harvest energy by improving our understanding of the electrochemical kinetics, water transport, and morphological changes at metal-hydrogel interfaces. This project is motivated by the need for new ways to power microelectronic devices that provide critical information for logistical decisions and are disconnected from the grid. To meet this need, we have developed a metal-air scavenger (MAS) that powers microelectronic devices by harvesting energy from metal surfaces that are prolific in urban and industrial environments. Our initial results show a thin MAS with an air cathode and hydrogel electrolyte can extract 337 mWh per square centimeter energy at up to 80 mWper square centimeterpower from aluminum and zinc surfaces. The MAS areal energy density is 300X greater than commercial thin film microbatteries. A MAS provides advantages over previous harvesting and storage strategies. First, a MAS provides a large amount of total energy, like a harvester, because it extracts energy from metal that has orders of magnitude larger volume than the powered microelectronic devices. Second, a MAS can be moved along a metal surface to increase its total energy output. If a MAS were to operate on a 30-inch aluminum stop sign, the total energy available would be 1,600 Wh, about 24X greater than a laptop battery and enough to power a 1 mW sensor for 182 years. Third, MAS devices can provide a constant power output and peak power output comparable to batteries. Fourth, MAS devices allow access to energy in areas not compatible with current harvesting technologies.To advance MAS performance, we will measure the oxidation kinetics of metal surfaces found in our industrial environment, improve our understanding of the chemical and morphological changes that occur at a metal-hydrogel interfaces when the metal is oxidized, and overcome electrolyte dry-out and air cathode flooding (which are problems in metal-air battery research). We will provide insight into these fundamental challenges by using electrochemical measurements, micrometer scale computed tomography, and materials characterization tools. First, we will use MAS devices to measure the electrochemical properties of carbon steel, stainless steel, copper, zinc, and aluminum metal surfaces exposed to hydrogel electrolytes. Our proof-ofprinciple MAS devices surprisingly extracted energy from the first three hundred microns of an aluminum surface. What will use microscale computed tomography to observe the 3-D kinetics at the metal-hydrogel interface that allow energy to be extracted deep into the metal surface, and use this information to improve energy extraction on different metals with electrolyte additives. We will also develop models to understand how the oxidized metal transports through the hydrogel electrolyte and how the electrolyte responds to anisotropic dehydration at the air cathode. Finally, we will study electrolyte composites and synthesize new solid electrolytes that harvest water from low humidity environments at high rates.The results of this research will provide fundamental insights that can be applied to improve MAS performance and resolve challenges in metal-air and aqueous battery research. In addition to enabling a new power source for microelectronics, this research will impact DOD capabilities by providing emergency power sources that increase the self-sufficiency, maneuverability, and operational endurance of a war fighter; enable autonomous maintenance inspection of metal surfaces; and advance the capabilities of vanishing or parasitic electronics.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- May 23, 2019
- Source ID
- N000141912353
Entities
People
- James H Pikul
Organizations
- Office of Naval Research
- United States Navy
- University of Pennsylvania