Resource World Magazine

66 www.resourceworld.com O C T O B E R / N O V E M B E R 2 0 1 9 Green Technologies by Jane Foutz DEVELOPING LITHIUM-TELLURIUM BATTERIES Researchers at the University of British Columbia (UBC), Okanagan are collabo- rating with Fenix Advanced Materials of Trail, British Columbia, to design and develop lithium-tellurium batteries using a tellurium-based cathode. Tellurium, a rare metal byproduct of copper and lead-zinc smelting which sometimes accompanies high-grade gold deposits, provides high energy density and a high safety rating for all-solid-state lithium-tellurium battery devices. Rapidly expanding portable electronics use and the evolution of electric vehicles is driving global demand for smaller but more powerful battery technology, explains Jian Liu, an assistant profes- sor in the School of Engineering at UBC Okanagan. "Due to the limited space and high reliability requirements in new devices, researchers are exploring technol- ogies that possess high energy density and more stable configurations. Due to its high density, tellurium provides a much higher volumetric capacity than other cathode materials, such as sulfur and selenium," explains Liu. "With the advantages of high volumetric energy density and excellent safety, all-solid-state lithium-tellurium batteries have the potential to power high-end electronic applications where a smaller size, but higher energy output is required." The project and future spin-off proj- ects aim to integrate the raw material supply with developing and manufactur- ing next-generation lithium-tellurium batteries in the BC Interior. Additional collaboration between UBC, Fenix and other research institutions, including the National Cheng Kung University in Taiwan and the Flemish Institute for Technological Research in Belgium are under discussion. The research is possible through a Mitacs Accelerate Grant with partnership from Fenix Advanced Materials and Metal Tech Alley, also of Trail, British Columbia. Other BC companies involved include Teck Metals, Retriev Technologies, Eagle Graphite and Deer Horn Capital. GENERATING ELECTRICITY FROM RUST FILM AND SALTWATER New research conducted by scientists at the California Institute of Technology in Pasadena, California (CalTech) and Northwestern University, Evanston Illinois, shows that thin rust films (iron oxide), when saltwater flows over them, can generate electricity. These rust films represent a new way of generating elec- tricity and could lead to new forms of sustainable power production. Interactions between metal compounds and saltwater often generate electricity, but this is usually the result of a chemical reaction in which one or more compounds are converted to new compounds. Reactions like these are at work inside batteries. In contrast, the phenomenon discovered by Tom Miller, CalTech profes- sor of chemistry, and Franz Geiger, Dow Professor of Chemistry at Northwestern, does not involve chemical reactions, but rather converts the kinetic energy of flow- ing saltwater into electricity. The phenomenon, the electrokinetic effect, has been observed before in thin films of graphene, sheets of carbon atoms arranged in a hexagonal lattice. The effect is around 30% efficient at converting kinetic energy into electricity. For refer- ence, the best solar panels are only about 20% efficient. "A similar effect has been seen in some other materials. You can take a drop of saltwater and drag it across gra- phene and see some electricity generated," Miller says. However, it is difficult to fabricate gra- phene films and scale them up to usable sizes. The iron oxide films discovered by Miller and Geiger are relatively easy to produce and scalable to larger sizes, Miller says. "It's basically just rust on iron, so it's pretty easy to make in large areas," Miller says. "This is a more robust implementa- tion of the thing seen in graphene." Though rust will form on iron alloys on its own, the team wanted to ensure it formed in a consistently thin layer. To do that, they used a process called physi- cal vapor deposition (PVD), which turns normally solid materials, in this case iron oxide, into a vapor that condenses on a desired surface. PVD allowed them to create an iron oxide layer 10 nanometers thick, about 10,000 times thinner than a human hair. "For perspective, plates having an area of 10 square metres each would generate a few kilowatts per hour – enough for a stan - dard US home," Miller says. "Of course, less demanding applications, including low-power devices in remote locations, are more promising in the near term." The mechanism behind the electricity genera- tion is complex, involving ion adsorption and desorption, but it essentially works like this: The ions present in saltwater attract electrons in the iron beneath the layer of rust. As the saltwater flows, so do those ions, and through that attractive force, they drag the electrons in the iron along with them, generating an electrical current. Miller says this effect could be useful in specific scenarios with moving saline solutions, like in the ocean or the human body. "For example, tidal energy, or things bobbing in the ocean, like buoys, could be used for passive electrical energy con- version," he says. "You have saltwater flowing in your veins in periodic pulses. That could be used to generate electric- ity for powering implants." The paper

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