lithium+ion+batteries
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Researchers Report Longest-lived Aqueous Flow Batteries
New technology to overcome the life limit of next-generation water-cell batteries
A research team led by Professor Hee-Tak Kim from the Department of Chemical and Biomolecular Engineering has developed water-based zinc/bromine redox flow batteries (ZBBs) with the best life expectancy among all the redox flow batteries reported by identifying and solving the deterioration issue with zinc electrodes.
Professor Kim, head of the Advanced Battery Center at KAIST's Nano-fusion Research Institute, said, "We presented a new technology to overcome the life limit of next-generation water-cell batteries. Not only is it cheaper than conventional lithium-ion batteries, but it can contribute to the expansion of renewable energy and the safe supply of energy storage systems that can run with more than 80 percent energy efficiency."
ZBBs were found to have stable life spans of more than 5,000 cycles, even at a high current density of 100 mA/cm2. It was also confirmed that it represented the highest output and life expectancy compared to Redox flow batteries (RFBs) reported worldwide, which use other redox couples such as zinc-bromine, zinc-iodine, zinc-iron, and vanadium.
Recently, more attention has been focused on energy storage system (ESS) that can improve energy utilization efficiency by storing new and late-night power in large quantities and supplying it to the grid if necessary to supplement the intermittent nature of renewable energy and meet peak power demand.
However, lithium-ion batteries (LIBs), which are currently the core technology of ESSs, have been criticized for not being suitable for ESSs, which store large amounts of electricity due to their inherent risk of ignition and fire. In fact, a total of 33 cases of ESSs using LIBs in Korea had fire accidents, and 35% of all ESS facilities were shut down. This is estimated to have resulted in more than 700 billion won in losses.
As a result, water-based RFBs have drawn great attention. In particular, ZBBs that use ultra-low-cost bromide (ZnBr2) as an active material have been developed for ESSs since the 1970s, with their advantages of high cell voltage, high energy density, and low price compared to other RFBs. Until now, however, the commercialization of ZBBs has been delayed due to the short life span caused by the zinc electrodes. In particular, the uneven "dendrite" growth behavior of zinc metals during the charging and discharging process leads to internal short circuits in the battery which shorten its life.
The research team noted that self-aggregation occurs through the surface diffusion of zinc nuclei on the carbon electrode surface with low surface energy, and determined that self-aggregation was the main cause of zinc dendrite formation through quantum mechanics-based computer simulations and transmission electron microscopy. Furthermore, it was found that the surface diffusion of the zinc nuclei was inhibited in certain carbon fault structures so that dendrites were not produced.
Single vacancy defect, where one carbon atom is removed, exchanges zinc nuclei and electrons, and is strongly coupled, thus inhibiting surface diffusion and enabling uniform nuclear production/growth. The research team applied carbon electrodes with high density fault structure to ZBBs, achieving life characteristics of more than 5,000 cycles at a high charge current density (100 mA/cm2), which is 30 times that of LIBs.
This ESS technology, which can supply eco-friendly electric energy such as renewable energy to the private sector through technology that can drive safe and cheap redox flow batteries for long life, is expected to draw attention once again.
Publication:
Ju-Hyuk Lee, Riyul Kim, Soohyun Kim, Jiyun Heo, Hyeokjin Kwon, Jung Hoon Yang, and Hee-Tak Kim. 2020. Dendrite-free Zn electrodeposition triggered by interatomic orbital hybridization of Zn and single vacancy carbon defects for aqueous Zn-based flow batteries. Energy and Environmental Science, 2020, 13, 2839-2848.
Link to download the full-text paper:http://xlink.rsc.org/?DOI=D0EE00723D
Profile: Prof. Hee-Tak Kimheetak.kim@kaist.ac.krhttp://eed.kaist.ac.krAssociate ProfessorDepartment of Chemical & Biomolecular EngineeringKAIST
2020.12.16 View 11029 -
KAIST Develops a Credit-Card-Thick Flexible Lithium Ion Battery
Since the battery can be charged wirelessly, useful applications are expected including medical patches and smart cards.
Professor Jang Wook Choi at KAIST’s Graduate School of Energy, Environment, Water, and Sustainability (EEWS) and Dr. Jae Yong Song at the Korea Research Institute of Standards and Science jointly led research to invent a flexible lithium ion battery that is thinner than a credit card and can be charged wirelessly.
Their research findings were published online in Nano Letters on March 6, 2015. Lithium ion batteries are widely used today in various electronics including mobile devices and electronic cars. Researchers said that their work could help accelerate the development of flexible and wearable electronics.
Conventional lithium ion batteries are manufactured based on a layering technology, stacking up anodes, separating films, and cathodes like a sandwich, which makes it difficult to reduce their thickness. In addition, friction arises between layers, making the batteries impossible to bend. The coating films of electrodes easily come off, which contributes to the batteries’ poor performance.
The research team abandoned the existing production technology. Instead, they removed the separating films, layered the cathodes and anodes collinearly on a plane, and created a partition between electrodes to eliminate potential problems, such as short circuits and voltage dips, commonly present in lithium ion batteries.
After more than five thousand consecutive flexing experiments, the research team confirmed the possibility of a more flexible electrode structure while maintaining the battery performance comparable to the level of current lithium ion batteries.
Flexible batteries can be applied to integrated smart cards, cosmetic and medical patches, and skin adhesive sensors that can control a computer with voice commands or gesture as seen in the movie “Iron Man.”
Moreover, the team has successfully developed wireless-charging technology using electromagnetic induction and solar batteries.
They are currently developing a mass production process to combine this planar battery technology and printing, to ultimately create a new paradigm to print semiconductors and batteries using 3D printers.
Professor Choi said, “This new technology will contribute to diversifying patch functions as it is applicable to power various adhesive medical patches.”
Picture 1: Medical patch (left) and flexible secondary battery (right)
Picture 2: Diagram of flexible battery
Picture 3: Smart card embedding flexible battery
2015.03.24 View 10714