Metal-Air Batteries (MABs), which use oxygen from ambient air as recourses to store and convert energy, have received considerable attention for their potential use in electric vehicles (EVs) owing to their large storage capacity, lightweight, and affordability.

Researchers at Ulsan National Institute of Science and Technology (UNIST) in S. Korea have developed a new catalyst that could boost the charge-discharge performance of metal-air batteries.

The new catalyst is formed by a very thin layer of metal oxide film deposited on a surface of perovskite catalysts; the interface naturally formed between the two catalysts enhances the overall performance and stability of the new catalyst. A paper on their work is published in Nano Energy.

Metal-air batteries (MABs), in which oxygen from the atmosphere reacts with metals to generate electricity, are one of the lightest and most compact types of batteries. They are equipped with anodes made up of pure metals (i.e. lithium, zinc, magnesium, and aluminum) and an air cathode that is connected to an inexhaustible source of air.

Due to their high theoretical energy density, MABs have been considered a strong cadidate for the next-generation electric vehicles. The currently existing MABs use rare and expensive metal catalysts for their air electrodes, such as platinum (Pt). This has hindered its further commercialization into the marketplace. As an alternative, perovskite catalysts that exhibit excellent catalyic performance has been proposed, yet there exists low activation barriers.

Schematic illustration of the self-reconstructed interlayer in LSM-20-Co derived by in-situ Mn diffusion via repeated atomic layer deposition cycles.

Professor Guntae Kim in the School of Energy and Chemical Engineering at UNIST has addressed this issue with a new composite catalyst combining two types of catalysts, each of which showed excellent performance in charge and discharge reactions.

The metal catalyst (cobalt oxide, Co₃O₄), which performs well in charging, is deposited on a very thin layer on top of the manganese-based perovskite catalyst (La_0.5Sr_0.5MnO₃, LSM), which performs well in discharge. As a result, the synergistic effect of the two catalysts became optimal when the deposition process was repeated 20 times.

During the repeated deposition and oxidation cycles of atomic layer deposition (ALD) process, the Mn cations diffuse into Co₃O₄ from LSM, and therefore, the LSM-20-Co catalyst is composed of LSM encapsulated with the self-reconstructed spinel interlayer (Co₃O₄/MnCo₃₂O₄/LSM). And this has enhanced the catalytic activity of the hybrid catalyst, LSM-20-Co, leading to superior bifunctional electrochemical performances for the ORR and the OER in alkaline solutions.

—Arim Seong (Combined M.S/Ph.D. of Energy and Chemical Engineering, UNIST), first author

The researches said that, To the best of their knowledge, this is the first study to investigate the self-reconstructed interlayer induced by the in-situ cation diffusion during ALD process for designing an efficient and stable bifunctional catalyst for alkaline zinc-air batteries.

Our findings provide the rational design strategy of self-reconstructed interlayer for efficient electro-catalyst. Therefore, this work can provide insight into the rational design strategy of metal oxide with perovskite materials.

—Professor Kim

This research has been carried out in collaboration with Professor Raymond J. Gorte (University of Pennsylvania), Professor John M. Vohs (University of Pennsylvania), and Professor Hu Young Jeong (UNIST).

This work has been supported by Global Ph.D. Fellowship Program of NRF Grant funded by the Korean Ministry of Science and ICT (MSIT). Also, it has been supported by the Korea Institute of Energy Technology Evaluation and Planning (KETEP) and the Korean Ministry of Trade, Industry & Energy (MOTIE).

Resources

• Arim Seong, Jeongwon Kim, Ohhun Kwon, Hu Young Jeong, Raymond J. Gorte, John M. Vohs, Guntae Kim (2020) “Self-reconstructed interlayer derived by in-situ Mn diffusion from La_0.5Sr_0.5MnO₃ via atomic layer deposition for an efficient bi-functional electrocatalyst,” Nano Energy, Volume 71, doi: 10.1016/j.nanoen.2020.104564