Energy+Materials+Lab
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A KAIST Research Team Develops an Ultra-High Performing “Universal Electrode” for Next-Generation Fuel Cells
Fuel cells are devices that generate electricity with high efficiency using hydrogen, a clean energy source, and are expected to play an important part in the upcoming hydrogen society. The recent development of an excellent universal electrode material that is applicable to all next-generation fuel cells and can withstand 700 hours of operation has therefore garnered a great deal of attention.
On August 9, a joint research team led by Prof. WooChul Jung from the KAIST Department of Materials Science and Engineering, Prof. Kang Taek Lee from the KAIST Department of Mechanical Engineering, and Prof. Jun Hyuk Kim from the Department of Chemical Engineering at Hongik University announced the development of an electrode material that is applicable to both oxygen- and proton-conducting solid oxide cells.
Depending on the type of ion conducted by the electrolyte, ceramic fuel cells are categorized into either solid oxide fuel cells (SOFC) or protonic ceramic fuel cells (PCFC). As they can both convert between electricity and hydrogen production, fuel cells can be categorized into a total of four device types. These devices are applicable in hydrogen fuel cell vehicles, hydrogen charging stations, and power generation systems, and are henceforth emerging as core next-generation technologies for a carbon-neutral society.
However, these devices have a chronic problem where the speed of their slowest reaction would decrease with a drop of driving temperature, which greatly reduces device efficiency. Various studies have been conducted to solve this, but most reported that electrode materials have low catalytic activity and their applications are limited to specific devices, which limits them from being used as SOFCs that require reversible power conversion and hydrogen production.
< Figure 1. Schematic diagram of high-performance oxygen ion conductive solid oxide fuel cell (SOFC) and proton conductive ceramic fuel cell (PCFC) operates with the new universal electrodes >
To solve this issue, the research team doped a perovskite oxide material with Ta5+, a high valence ion that did not receive much attention in the field. Through this, the team successfully stabilized what is usually a highly unstable crystal structure, and confirmed that catalytic activity improved by 100 times.
The electrode material developed by the team was applied to all four of the mentioned device types. Furthermore, their efficiencies were greater than any of the devices reported thus far, and showed excellent performance by stably running for much longer (700 hours) compared to existing materials that deteriorated within the first 100 hours of operation.
< Figure 2. (a) Power conversion and hydrogen production performance chart for the protonic ceramic fuel cell (PCFC) with the new universal electrodes (b) and performance comparison with other reported devices >
This research, in which KAIST’s Ph.D. candidates Dongyeon Kim and Sejong Ahn, and Professor Jun Hyuk Kim from Hongik University contributed as co-first authors, was published in the internationally renowned Energy & Environmental Science under the title, "Oxygen-Electrode for Reversible Solid Oxide Electrochemical Cells at Reduced Temperatures".
Prof. WooChul Jung said, “We broke free from the idea that we must develop a completely new material to solve an existing problem, and instead suggested a way to control the crystal structure of a lesser-known material to develop a high-efficiency fuel cell, and that’s what makes these results more significant.”
Prof. Kang Taek Lee added, “Unlike previously reported materials that could only be applied to one device type at a time, our material has the flexibility of being applicable to all four. We therefore look forward to its contribution in the commercialization of eco-friendly energy technology including fuel cells and water-splitting equipment for hydrogen production.”
This research was supported by a National Research Foundation of Korea (NRF) grant funded by the Korean Ministry of Science and ICT.
2023.08.22 View 4469 -
A Study Shows Reactive Electrolyte Additives Improve Lithium Metal Battery Performance
Stable electrode-electrolyte interfaces constructed by fluorine- and nitrogen-donating ionic additives provide an opportunity to improve high-performance lithium metal batteries
A research team showed that electrolyte additives increase the lifetime of lithium metal batteries and remarkably improve the performance of fast charging and discharging. Professor Nam-Soon Choi’s team from the Department of Chemical and Biomolecular Engineering at KAIST hierarchized the solid electrolyte interphase to make a dual-layer structure and showed groundbreaking run times for lithium metal batteries.
The team applied two electrolyte additives that have different reduction and adsorption properties to improve the functionality of the dual-layer solid electrolyte interphase. In addition, the team has confirmed that the structural stability of the nickel-rich cathode was achieved through the formation of a thin protective layer on the cathode. This study was reported in Energy Storage Materials.
Securing high-energy-density lithium metal batteries with a long lifespan and fast charging performance is vital for realizing their ubiquitous use as superior power sources for electric vehicles. Lithium metal batteries comprise a lithium metal anode that delivers 10 times higher capacity than the graphite anodes in lithium-ion batteries. Therefore, lithium metal is an indispensable anode material for realizing high-energy rechargeable batteries. However, undesirable reactions among the electrolytes with lithium metal anodes can reduce the power and this remains an impediment to achieving a longer battery lifespan. Previous studies only focused on the formation of the solid electrolyte interphase on the surface of the lithium metal anode.
The team designed a way to create a dual-layer solid electrolyte interphase to resolve the instability of the lithium metal anode by using electrolyte additives, depending on their electron accepting ability and adsorption tendencies. This hierarchical structure of the solid electrolyte interphase on the lithium metal anode has the potential to be further applied to lithium-alloy anodes, lithium storage structures, and anode-free technology to meet market expectations for electrolyte technology.
The batteries with lithium metal anodes and nickel-rich cathodes represented 80.9% of the initial capacity after 600 cycles and achieved a high Coulombic efficiency of 99.94%. These remarkable results contributed to the development of protective dual-layer solid electrolyte interphase technology for lithium metal anodes.
Professor Choi said that the research suggests a new direction for the development of electrolyte additives to regulate the unstable lithium metal anode-electrolyte interface, the biggest hurdle in research on lithium metal batteries.
She added that anode-free secondary battery technology is expected to be a game changer in the secondary battery market and electrolyte additive technology will contribute to the enhancement of anode-free secondary batteries through the stabilization of lithium metal anodes.
This research was funded by the Technology Development Program to Solve Climate Change of the National Research Foundation in Korea funded by the Ministry of Science, ICT & Future Planning and the Technology Innovation Program funded by the Ministry of Trade, Industry & Energy, and Hyundai Motor Company.
- PublicationSaehun Kim, Sung O Park, Min-Young Lee, Jeong-A Lee, Imanuel Kristanto, Tae Kyung Lee, Daeyeon Hwang, Juyoung Kim, Tae-Ung Wi, Hyun-Wook Lee, Sang Kyu Kwak, and NamSoon Choi, “Stable electrode-electrolyte interfaces constructed by fluorine- and nitrogen-donating ionic additives for high-performance lithium metal batteries,” Energy Storage Materials,45, 1-13 (2022), (doi: https://doi.org/10.1016/j.ensm.2021.10.031)
- ProfileProfessor Nam-Soon ChoiEnergy Materials LaboratoryDepartment of Chemical and Biomolecular EngineeringKAIST
2021.12.16 View 7387 -
Highly Efficient and Stable Double Layer Solar Cell Developed
Solar cells convert light into energy, but they can be inefficient and vulnerable to the environment, degrading with, ironically, too much light or other factors, including moisture and low temperature. An international research team has developed a new type of solar cell that can both withstand environmental hazards and is 26.7% efficient in power conversion.
They published their results on March 26 in Science.
The researchers, led by Byungha Shin, a professor from the Department of Materials Science and Engineering at KAIST, focused on developing a new class of light-absorbing material, called a wide bandgap perovskite. The material has a highly effective crystal structure that can process the power needs, but it can become problematic when exposed to environmental hazards, such as moisture. Researchers have made some progress increasing the efficiency of solar cells based on perovskite, but the material has greater potential than what was previously achieved.
To achieve better performance, Shin and his team built a double layer solar cell, called tandem, in which two or more light absorbers are stacked together to better utilize solar energy. To use perovskite in these tandem devices, the scientists modified the material’s optical property, which allows it to absorb a wider range of solar energy. Without the adjustment, the material is not as useful in achieving high performing tandem solar cells. The modification of the optical property of perovskite, however, comes with a penalty — the material becomes hugely vulnerable to the environment, in particular, to light.
To counteract the wide bandgap perovskite’s delicate nature, the researchers engineered combinations of molecules composing a two-dimensional layer in the perovskite, stabilizing the solar cells.
“We developed a high-quality wide bandgap perovskite material and, in combination with silicon solar cells, achieved world-class perovskite-silicon tandem cells,” Shin said.
The development was only possible due to the engineering method, in which the mixing ratio of the molecules building the two-dimensional layer are carefully controlled. In this case, the perovskite material not only improved efficiency of the resulting solar cell but also gained durability, retaining 80% of its initial power conversion capability even after 1,000 hours of continuous illumination. This is the first time such a high efficiency has been achieved with a wide bandgap perovskite single layer alone, according to Shin.
“Such high-efficiency wide bandgap perovskite is an essential technology for achieving ultra-high efficiency of perovskite-silicon tandem (double layer) solar cells,” Shin said. “The results also show the importance of bandgap matching of upper and lower cells in these tandem solar cells.”
The researchers, having stabilized the wide bandgap perovskite material, are now focused on developing even more efficient tandem solar cells that are expected to have more than 30% of power conversion efficiency, something that no one has achieved yet,
“Our ultimate goal is to develop ultra-high-efficiency tandem solar cells that contribute to the increase of shared solar energy among all energy sources,” Shin said. “We want to contribute to making the planet healthier.”
This work was supported by the National Research Foundation of Korea, the Korea Institute of Energy Technology Evaluation and Planning, the Ministry of Trade Industry and Energy of Korea, and the U.S. Department of Energy.
Other contributors include Daehan Kim, Jekyung Kim, Passarut Boonmongkolras, Seong Ryul Pae and Minkyu Kim, all of whom affiliated with the Department of Materials Science and Engineering at KAIST. Other authors include Byron W. Larson, Sean P. Dunfield, Chuanxiao Xiao, Jinhui Tong, Fei Zhang, Joseph J. Berry, Kai Zhu and Dong Hoe Kim, all of who are affiliated with the National Renewable Energy Laboratory in Colorado. Dunfield is also affiliated with the Materials Science and Engineering Program at the University of Colorado; Berry is also affiliated with the Department of Physics and the Renewable and Sustainable Energy Institute at the University of Colorado Boulder; and Kim is also affiliated with the Department of Nanotechnology and Advanced Materials Engineering at Sejong University. Hee Joon Jung and Vinayak Dravid of the Department of Materials Science and Engineering at Northwestern University; Ik Jae Park, Su Geun Ji and Jin Young Kim of the Department of Materials Science and Engineering at Seoul National University; and Seok Beom Kang of the Department of Nanotechnology and Advanced Materials Engineering of Sejong University also contributed.
Image credit: Professor Byungha Shin, KAIST
Image usage restrictions: News organizations may use or redistribute this image, with proper attribution, as part of news coverage of this paper only.
Publication: Kim et al. (2020) “Efficient, stable silicon tandem cells enabled by anion-engineered wide band gap perovskites”. Science. Available online at https://doi.org/10.1126/science.aba3433
Profile:
Byungha Shin
Professor
byungha@kaist.ac.kr
http://energymatlab.kaist.ac.kr/
Department of Materials Science and Engineering
KAIST
Profile:
Daehan Kim
Ph.D. Candidate
zxzx4592@kaist.ac.kr
http://energymatlab.kaist.ac.kr/
Department of Materials Science and Engineering
KAIST
(END)
2020.03.27 View 17491 -
Biomimetic Carbon Nanotube Fiber Synthesis Technology Developed
The byssus of the mussel allows it to live in harsh conditions where it is constantly battered by crashing waves by allowing the mussel to latch onto the seaside rocks. This particular characteristic of the mussel is due to the unique structure and high adhesiveness of the mussel’s byssus.
KAIST’s Professor Hong Soon Hyung (Department of Material Science and Engineering) and Professor Lee Hae Shin (Department of Chemistry) and the late Professor Park Tae Kwan (Department of Bio Engineering) were able to reproduce the mussel’s byssus using carbon nanotubes.
The carbon nanotube, since its discovery in 1991, was regarded as the next generation material due to its electrical, thermal, and mechanical properties. However due to its short length of several nanometers, its industrial use was limited.
The KAIST research team referred to the structure of the byssus of the mussel to solve this problem.
The byssus is composed of collagen fibers and Mefp-1 protein which are in a cross-linking structure. The Mefp-1 protein has catecholamine that allows it to bind strongly with the collagen fiber.
In the artificial structure, the carbon nanotube took on the role of the collagen fibers and the macromolecular adhesive took on the role of the catecholamine. The result was a fiber that was ultra-light and ultra-strong.
The results of the experiment were published in the Advanced Materials magazine and is patent registered both domestically and internationally.
2011.06.20 View 11762