Cornell Energy Systems Institute
The Rotating Disk Electrode System allows researchers to compare the performance of different electrochemical recipes in a battery. Spinning an electrode in an electrochemical cell establishes stable mass transfer at the electrode’s surface. Researchers can then determine the number of electrons in the reaction, infer the mechanism of an electrochemical reaction, and calculate parameters such as the diffusion coefficient. The Rotating Disk Electrode System is a versatile tool for catalysis, characterizing nanomaterials, and developing metal-air batteries.
To store energy from renewable sources such as wind and solar, CESI researchers are working on more efficient, stable, long-lasting battery systems that can be charged and discharged without loss of performance. The Lynden Archer group has creatively repurposed the Rotating Disk Electrode System to develop better rechargeable batteries. By revealing details of the electrochemical reaction on the electrode surface, the tests are guiding the design of novel electrodes.
The BET applies the Brunauer–Emmett–Teller (BET) theory to analyze a material’s surface area and porosity. To generate its readings, the BET lowers the testing sample to -77 degrees Celsius with liquid nitrogen and then measures how much gaseous nitrogen the sample absorbs at various atmospheric pressures.
Surface area and porosity are crucial measures of a material’s performance as an absorbent. The Emmanuel Giannelis group uses the BET to develop nanoparticles that selectively absorb petroleum, not water, from an oil-water mixture. Such a material has the potential to increase efficiency and reduce waste of energy-extraction processes.
A laser-based instrument, the Zetasizer uses dynamic light scattering to generate detailed information about the distribution of particle size and molecular weight of a sample. It also measures the sample’s zeta or surface potential—a measure of how well a molecule or particle will disperse in a solvent. The Emmanuel Giannelis group uses the Zetasizer, like the BET, to develop nanoparticles that selectively absorb petroleum but not water. After water is injected into an oil well, the nanoparticles could absorb petroleum from the mixture, a process that increases the efficiency of energy extraction.
The rheometer measures the deformation and flow of a soft material at different temperatures in response to mechanical force. CESI researchers often use the rheometer to test polymers for their potential to improve battery performance.
Why use polymers? Lithium-ion batteries are among the most common batteries today, but electrochemical reactions that use lithium metal as an anode could be more efficient and cost-effective. The problem is byproducts that lithium anodes generate, forming root-like dendrites that eventually destroy the battery from within. The Lynden Archer group develops polymer-based electrolytes, including viscoelastic liquids and solid-state polymers, to suppress the dendritic growth above the diffusion limit. The research is a significant step toward safe lithium metal batteries with high energy density.
The SAXS performs structural analysis of materials at a resolution of one nanometer or better, providing data that might otherwise require a particle accelerator to generate. Imagine a synchrotron that fits on a pool table. The SAXS characterizes physical properties by using small-angle x-ray scattering (SAXS). A tube at one end of the machine emits x-rays that pass through a solid or liquid sample. The sample scatters the x-rays at small angles that the SAXS detects and analyzes. The SAXS can characterize catalysts, proteins, colloids, liquid crystals, polymers, and other soft materials.
The Yong Joo group uses the SAXS to study how graphene structures change when introduced into different media. The results are contributing to material innovations in anodes for lithium-ion batteries.
The AFM can image point defects, characterize nanomaterials, and generate three-dimensional topographies of thin films and crystal lattices at high resolutions. A micrometer-scale silicon tip at the end of a tiny oscillating cantilever moves over the surface of a sample. Researchers choose between contact or non-contact mode depending on the nature of the sample and the target data. As the surface of the sample applies force to the tip—either through direct contact or van der Waals, electrostatic, or other forces—a laser measures deviations in the position of the cantilever.
Huili Grace Xing’s group uses the AFM in non-contact mode to determine the morphology, roughness, conductive path, and donor-acceptor structure of thin-film semiconductors. Taking advantage of gallium nitride and other wide bandgap semiconductors, the Xing group is creating electronic devices capable of improving solar panels and reducing inefficiencies in the power grid.
Among the AFM’s operating modes are force curves, force mapping mode, Kelvin probe force microscopy (KPFM), magnetic force microscopy (MFM), and piezoresponse force microscopy (PFM). Samples can be tested in inert gasses or a vacuum at different temperatures. This is especially important to battery researchers, who use the AFM in situ to analyze metal deposition on the surface of an electrode during an electrochemical reaction.
The dielectric spectrometer generates a highly accurate profile of a material’s or system’s electrical properties—including dielectric polarization, conductivity, and electrochemical impedance—making it an essential tool for battery research. By measuring the dielectric properties of a battery at frequencies from three microhertz to 10 gigahertz and temperatures ranging from -160 to 400 degrees Celsius, the dielectric spectrometer creates a step-by-step picture of the battery’s electrochemical reaction. Researchers can identify ion and electron transport in an electrolyte, characterize electrolyte-metal interfaces, and evaluate the resistance of battery components.
The Lynden Archer group uses the dielectric spectrometer to measure the conductivity, impedance, and the diffusion coefficient of various polymers. Evaluating the polymers in different conditions is important for optimizing the design of polymer-based electrolytes.
The Cornell Energy Systems Institute (CESI) works rigorously toward its goal to reduce humanity’s carbon footprint through innovations in materials, technology, and systems design. CESI gathers resources and expertise from across Cornell University, more than 50 faculty experts, to address the grand-challenge technical questions. The center supports energy innovation totally—from developing new materials to translating discoveries into marketable energy solutions.
CESI identified four goals to maximize its social and environmental impact: making electric transportation a norm; enabling smart, data-driven manufacturing and power generation technologies; creating reliable, cost-effective means of generating energy with a low carbon footprint; and making carbon dioxide capture and conversion cost-effective and commonplace in construction and process systems. Lynden A. Archer, Chemical and Biomolecular Engineering/David Croll Director of CESI, says, “CESI must build upon Cornell’s reputation as a place to pursue leading-edge research to create the infrastructure, programs, and expertise needed to translate frontier research into impactful products.”
CESI leverages research facilities across Cornell’s Ithaca campus. With the Living Laboratory model, Cornell has made its entire campus a laboratory for energy innovation, piloting new technologies and initiatives with the goal of achieving carbon neutrality on campus by 2035.
CESI’s research facility in Kimball Hall, the CESI Soft Matter Laboratory (CESI-L), boasts a complete inventory of research tools and unique state-of-the-art instrumentation for soft materials research. As a multi-user, fee-per-use facility, CESI-L is a hub for collaboration and creative problem-solving for research groups and private-sector innovators, united by a common mission.
In addition to its ambitious research agenda, CESI sponsors post-doctoral fellowships and a weekly Energy Seminar.