News Source: Advanced Research Institute of Multidisciplinary Science (ARIMS)

Editor: News Agency of BIT Review: Tang Shuiyuan

Recently, top international journals in the field of materials, Advanced Materials (Impact factor 27.3), reported the research progress of Huang Jiaqi's group at Advanced Research Institute of Multidisciplinary Science(ARIMS) of Beijing Institute of Technology(BIT) on the kinetic regulation of the positive electrode of lithium-sulfur (Li-S) batteries. Related research results were published online as "An organodiselenide comediator to facilitate sulfur redox kinetics in lithium-sulfur batteries". The first author of this work is Zhao Meng, PhD student of ARIMS of BIT, and the corresponding author is Professor Huang Jiaqi.

Due to the theoretical energy density up to 2600 Wh kg−1, lithium sulfur (Li-S) batteries have attracted wide attention as one of the options for the next generation of energy storage devices. As an endogenous redox mediator, soluble lithium sulfide has a direct influence in the electrochemical process of sulfur cathode during the cycle of Li-S battery. Among them, lithium polysulfide mediators mediate the electrochemical reaction of sulfur cathode through chemical disproportionation or comproportionation, which affects the deposition/dissolution process and reaction rate of the final discharge/charge product, thus affecting the capacity and rate performance of the battery. However, the poor mediating capacity of the lithium polysulfide mediator results in a slow redox kinetics of the sulfur cathode, which further results in limited rate performance, reduced discharge capacity and rapid decay of the battery. Therefore, there is an urgent need to develop new strategies and chemical methods to fundamentally regulate and improve the mediation ability of endogenous lithium polysulfide, so as to accelerate the redox kinetics of sulfur cathode and achieve stable circulation of high specific energy Li-S batteries.

Based on the principle of the redox assisting mediation strategy, the team proposed a diphenyldiselenoether (DPDSe) based on organic selenide as a redox coagent to accelerate the redox kinetics of sulfur and construct a high-performance Li-S battery(Fig. 1). Among them, DPDSe spontaneously reacts with lithium polysulfide to form phenylselenium-polysulfide lithium (LiphSePSs) with higher mediation ability. The new species achieves faster redox kinetics by enhancing the redox mediated process and improves discharge capacity by adjusting the deposition size of lithium sulfide during liquid-solid conversion.

Fig. 1. Schematic diagram of conventional (left) and organic diselenide mediated (right) reaction pathways in Li-S batteries

The DPDSe auxiliary mediator reduces the energy barrier for multiphase and multi-electron conversion of the positive sulfur electrode, guarantees faster diffusion kinetics, and alters the deposition mode of lithium sulfide, thus achieving higher deposition capacity. Therefore, the DPDSe assisted mediation strategy is able to endow the battery with higher rate performance and higher discharge specific capacity, so that the Li-S battery can still provide a specific capacity of 817 mAh g−1 at a rate of 2 C, and maintain stable cycle ability even when matched with the ultra-thin lithium anode. In addition, the team assembled a DPDSe-assisted Li-S soft-pack battery and achieved an initial energy density of 301 Wh kg−1 and a stable cycle of 30 turns. This work demonstrates a redox assisted mediation strategy, proposes an effective DPDSe auxiliary mediator, which can improve the performance of Li-S batteries in practical conditions, and stimulates further exploration of dynamically-mediated strategies for practical and high energy density Li-S cells.

Attached introduction to the author:

Huang Jiaqi, professor at the Advanced Research Institute of Multidisciplinary Science from BIT, doctoral supervisor and a member of Jiusan Society. He is mainly engaged in energy interface chemistry research and has published more than 100 papers in journals such as Angew Chem Int Ed, J Am Chem Soc, Adv Mater, Adv Funct Mater and SCI Bull, with an H factor of 80 and more than 60 highly cited ESI papers. He was selected into the first China Association for Science and Technology Young Talent Promotion Program in 2015, and was awarded the Hou DeBang Chemical Science and Technology Youth Award of China Chemical Industry Society, the Young Granule Science Award of China Granule Society, the Top Young Talents of the National Ten Thousand People Program in 2018, and the Clarivate High Cited Scientist in 2018-2020, etc.

paper details:

Meng Zhao, Xiang Chen, Xi-Yao Li, Bo-Quan Li, Jia-Qi Huang*. An organodiselenide comediator to facilitate sulfur redox kinetics in lithium–sulfur batteries, Advanced Materials 2021, 10.1002/adma.202007298.

Paperlink: https://onlinelibrary.wiley.com/doi/full/10.1002/adma.202007298