The Research Result of the Team of Academician Chen Jianfeng Selected as One of " China's Top 10 Science Advances in 2023"

On February 29, the National Natural Science Foundation of China released the country's top 10 science advances in 2023, and the research result of the team of academician Chen Jianfeng of Beijing University of Chemical Technology The Discovery of a New Mechanism for Interfacial Charge Storage and Aggregation Reaction of Lithium-sulfur Batteries was selected. This is the first time that our university has been shortlisted for this list.

It is understood that lithium-sulfur batteries have extremely high energy density (2600 Wh kg-1) and low cost, however, the wide application of lithium-sulfur batteries has not yet been realized, because its battery performance will decline rapidly during charging and discharging, and each battery is like a mysterious black box. Due to the low spatiotemporal resolution of traditional in-situ microscopy techniques and the instability of lithium-sulfur systems, the chemical reaction process that occurs inside it is still unclear, and it is impossible to solve the problem in a targeted manner, which seriously hinders its application. Honggang Liao, Shigang Sun from Xiamen University, and Jianfeng Chen from Beijing University of Chemical Technology have developed high-resolution electrochemical in-situ transmission electron microscopy technology to realize real-time observation and research on atomic-scale dynamics of interface reactions of lithium-sulfur batteries by coupling the real electrolyte environment and the applied electric field. It is found that the molecules on the surface of the battery active material are aggregated into molecular clusters for reaction, and the charge transfer can be stored in the aggregated molecular clusters first, and the molecular clusters get electrons but do not undergo conversion until they obtain enough electrons for transient crystallization transformation. The surface of the inactive material follows the classical single-molecule reaction pathway, where the lithium polysulfide molecule gradually obtains electrons, converts them step by step, and finally converts them into Li2S. Simulation calculations show that the electrostatic interaction between the active center and lithium polysulfide promotes the aggregation of Li+ and polysulfide molecules, and confirms that the charge in the molecular aggregates can be transferred freely. In the past 100 years, electrochemical interfacial reactions have generally been understood to occur through only two single-molecule pathways: inner-sphere reactions and outer-sphere reactions. This study revealed the existence of a third mechanism of charge storage aggregation reaction in electrochemical interface reactions, deepened the understanding of the evolution of polysulfides and their influence on the kinetics of battery surface interface reactions, and provided guidance for the design of next-generation lithium-sulfur batteries.

Since its launch in 2005, this annual selection event has been successfully held for 19 sessions. In 2023, experts in related disciplines selected 30 achievements from more than 600 scientific research achievements, and on this basis, 10 major scientific research achievements were selected, mainly in life science and medicine, artificial intelligence, quantum, astronomy, chemical energy and other scientific fields.