MMAE Seminar by M. Helena Braga: Towards an Energy Harvesting and Storage Structural Cell with Na+-based Ferroelectric Electrolyte



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Armour College of Engineering’s Department of Mechanical, Materials, and Aerospace Engineering will welcome M. Helena Braga, an associate professor at the engineering physics department at the University of Porto, to present a lecture, titled “Towards an Energy Harvesting and Storage Structural Cell with Na+-based Ferroelectric Electrolyte.”

The virtual seminar will take place on Wednesday, November 3, from 3:30–4:30 p.m. Contact Elena Magnus at for the seminar details and a link to join.


Improved storage of electric power will be required in the upcoming era of the Internet of Things (IoT). Wireless sensor networks that monitor, detect, and gather data will be vital for advancements in human health, public safety, industrial automation, and energy management. Presently, rechargeable batteries are used to power the wireless network. However, the limitations of today’s Li-ion batteries make this power source unfeasible, from a cost and environmental perspective. A high priority is to convert wasted heat coming to Earth daily from sunlight and industry or combustion engines. Traditional devices converting heat into electrical energy base their working principles on the Seebeck effect, need a temperature gradient to work, and rely on expensive materials. Here, we show an energy storage cell based on a Na+-ferroelectric glass-electrolyte (Na2.99Ba0.005OCl) that spontaneously reduces its internal resistance while increasing its dielectric constant from -30ºC to 75ºC. This cell forms a negative capacitance capacitor at the interface with the negative electrode while discharging with a load and self-charges for months even while withstanding a load. The latter cell architecture is suitable for structural applications as it withstands 1.75 kN in the three-point bending mechanical flexural tests while performing electrochemically. The beam-like power cell reached an energy density of 989−1 for the positive electrode only (Cu) and an energy density of 78.1−1 and specific energy of 86.0 Wh.L−1 for the active electrolyte (Na2.99Ba0.005OCl), that drops to 38.0−1 and 56.2 Wh.L−1 for the whole cell (Al/Na+-electrolyte/Cu) including the carbon fiber reinforced plastic (CFRP) structural element. These cells may pave the way to safe and inexpensive structural energy harvest and storage as they rely on the capacity of the Na+-based solid electrolyte. Self-charging of a structural coaxial cell while set to discharge with a resistor of 26.6 kΩ. The cell is constituted by two coaxial collector-electrodes that fix the electrical potential difference and a ferroelectric Na+-based electrolyte that is accountable for the capacity of the cell.


Maria Helena Braga is an associate professor at the engineering physics department at the University of Porto; she was head of the department from 2019–2021. From 2016–2019 she was a senior research fellow at the University of Texas at Austin collaborating with Professor John B. Goodenough, who received the Nobel Prize of Chemistry in 2019. Throughout her career, Helena Braga was a long-term visiting staff member at Los Alamos National Laboratory (2008–2011) in New Mexico, working on hydrides and solid-state electrolytes. She has contributed research in light alloys, lead-free solders, and hydrogen storage materials, and she is credited with creating ferroelectric-glass electrolytes and novel energy harvesting and storage devices. In 2020 she was awarded the Exame Informatica (Exam Informatics) personality award for her work on energy storage.


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