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BIT’s New Achievement in the Research on Heterogeneous Catalysis of Lithium-sulfur (Li-S) Batteries

release date :2020-04-01 02:22:00  |   [ close window ]ViewCount:

  Beijing Institute of Technology, April 1st, 2020: Recently, Angewandte Chemie International Edition, a top international in chemistry and materials, reported the new achievements of research group led by Huang Jiaqi of Advanced Research Institute of Multidisciplinary Science of BIT in heterogeneous catalysis of Lithium-sulfur(Li-S) batteries, and relevant research achievements have been published online with the title of Electrochemical Phase Evolution of Metal-Based Pre-Catalysts for High-Rate Polysulfide Conversion. The first author of this work is Zhao Meng, a doctoral candidate of the Advanced Research Institute of Multidisciplinary Science of Beijing Institute of Technology, the co-first author is Dr. Peng Hongjie, and the corresponding author is Professor Huang Jiaqi of Beijing Institute of Technology.
 
     Under working conditions, the phase/structure evolution of the catalyst plays an important role in its catalytic activity and reaction kinetics. At present, understanding and exploration of in-situ phase evolution of catalyst is limited to proton hydrogen/oxygen (water) electrochemistry, while research in the field of aprotic electrochemistry is scarce, which is the cornerstone of alkaline metal (Li/Na/K) -chalcogen (S/O2) batteries with high energy density. Because of the multi electron transfer reaction, these battery systems often require highly efficient electrocatalysts to improve the slow kinetics of electrochemical reactions. However, at present, how these catalysts evolve in aprotic environments or actual influences of evolutionary behaviors on the catalytic performance are not yet known. Exploring the role of large-radius alkali metal cations and intermediates in the evolution of catalysts in an aprotic environment is of great significance to understand the role of electrocatalysts and determine their true active catalytic phases/sites, which is also a prerequisite for reasonably designing new catalysts and batteries with a better performance.

  The research team studied the in-situ phase evolution process of metal-based pre-catalysts in Li-S batteries under working conditions. And they revealed the in-situ transition from single crystal Co4N to polycrystalline CoSx rich in active sites induced by electrochemical cycling. The evolution product is highly adaptable to the aprotic environment rich in polysulfides, and has shown high catalytic activities to the reaction kinetics of sulfur-containing substances in model experiments. The team applied density functional theory to calculate the formation energies of different vacancies on the surface and bulk phase of Co4N particles under the action of polysulfide etching, and they verified the phase evolution mechanism caused by polysulfide etching. Further calculation based on a wide range of cobalt-based compounds and other metal elements have proven the wide applicability of electrochemically induced vulcanization, in which it is predicted that compounds containing zero-valent metal atoms will be fully or partially sulfurized in most metal catalysts and their metal-rich compound catalysts used in Li-S batteries.

 
Fig 1. Illustration and corresponding electron microscopy image of in-situ electrochemical phase evolution of precatalyst. Process illustration of the of in-situ "mosaic" phase evolution of a metal-rich compound as a precatalyst (taking Co4N as an example) in a working battery.

  When Co4N precatalyst is introduced into Li-S battery, the high activity catalyst from in-situ evolution can still show a good performance under severe kinetics (for example, 10 C rate and E/S ratio as low as 4.7 mL mgS1). Their job will have a wide influence on electrochemistry other than Li-S batteries and catalytic materials other than Co4N, including studies on the catalytically active phase of in-situ generated sulfides, and design of new electrocatalysts through electrochemical evolution, as well as new understanding and application of research transition from hydroelectrochemistry to aprotic electrochemistry.

 

Paper details:
Meng Zhao, Hong-Jie Peng, Bo-Quan Li, Xiao Chen, Jin Xie, Xinyan Liu, Qiang Zhang, Jia-Qi Huang*. Electrochemical Phase Evolution of Metal-Based Pre-Catalysts for High-Rate Polysulfide Conversion, Angewandte Chemie International Edtion, doi: 10.1002/anie.202003136.

Paper link:
https://onlinelibrary.wiley.com/doi/abs/10.1002/anie.202003136

  
About the author:
      Huang Jiaqi, Professor and PhD supervisor of Advanced Research Institute of Multidisciplinary Science, Beijing Institute of Technology, and member of Jiu San Society. He focuses on study in energy interface chemistry. And he has published more than 100 research papers in Angew Chem Int Ed, J Am Chem Soc, Adv Mater, Adv Funct Mater, Sci Bull and other journals, h factor is 68, of which more than 40 are ESI highly cited papers. He was selected into the first Young Talents Supporting Program of the Chinese Association of Science and Technology and was awarded the Hou Debang Chemical Technology Youth Award by the Chinese Chemical Society, China Granulation Society Youth Granulation Award, Young Top Talent of National High-level Talent Special Support Plan, and he was a highly cited researcher of 2018 and 2019 by Clarivate Analytics.

 

Translator: News Agency of BIT

Editor: News Agency of BIT

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