In Situ Magnetometry Study Of Electrochemical Interfacial Catalysis Energy Storage Mechanism In Lithium-ion Batteries

The crystal structure,electron atomic structure and electrical properties of transition metal materials are closely related to their magnetic properties,which provides a possibility for the characterization of electrochemical reaction processes by magnetic technology.The real-time detection of electron transport and active substance conversion process in electrochemical energy storage system has very important scientific value,so in situ magnetic technology can be a powerful tool to study the reaction mechanism of energy storage.In this paper,using in situ magnetometry,we systematically studied the the transition metal cobalt-based electrode materials（Co（OH）₂,CoCO₃）lithium-ion battery system.The electrochemical interface storage and interfacial catalytic mechanisms were discovered and discussed through in situ corresponding magnetic signals and other in situ/ex situ experimental characterization,and verified by first principles based on density functional theory（DFT）.The interconnection between the two is introduced,and the subtle changes in the electronic structure of the Co active center during the charge transfer process are explored.This work expands people’s understanding of the energy storage reaction mechanism of electrode materials and the problem of additional capacity,and provides a reference for the further development of advanced electrode materials and the design of next-generation new energy storage systems.The specific research contents are as follows:1.We develop and demonstrate a method to study the dynamic evolution of electrodes during electrochemical reactions by integrating microscopic and spectral analysis and in situ magnetometry techniques combined with density functional theory calculations.This method provides a dynamic picture of the chemical,physical,and electronic structure of the electrode,and discovers an electrochemical interfacial catalytic mechanism involving spin-polarized electron transfer.Taking Co（OH）₂ as the model material,the dynamic evolution process of Co metal center under different voltages was visually demonstrated.We found that prior to the interfacial catalytic reaction,spin-polarized surface capacitance was formed at the metallic Co nanoparticles/LiOH interface due to the injection of spin-polarized electrons.The structure of this surface capacitance predicts the final interfacial chemistry,in particular the catalytic activation of cobalt nanoparticles as catalytic activation centers that promote the decomposition activity of LiOH.The progress of this interfacial catalytic reaction is influenced by the electrode potential,and the dynamic changes in the electronic structure of metallic Co nanoparticles including spin polarized electron transfer,can be directly monitored under the precise LiOH decomposition reaction potential.This study provides a new technique for studying the dynamic evolution of interfacial catalytic processes and will help design better electrochemical interfaces and electrode materials for a wide range of energy systems.2.Transition metal oxides and related compounds exhibit high catalytic activity in various electrochemical reactions due to their interesting electronic structure.It is less well known that their unique role in storing and transferring electrons in battery electrodes allows battery electrode materials to undergo additional solid-state conversion reactions and exhibit considerable additional capacity contributions.The advanced in situ magnetometry technology can be used to monitor the electron transfer within the electrode in real time and realize the dynamic tracking of the electrochemical reaction.A dynamic image of the generation and evolution of the electrochemical interface in the presence of metal nanoparticles is described in CoCO₃/Li batteries.The lithium reaction process of the battery system as a whole was shown to be a mixture of interfacial storage and catalytic decomposition mechanisms,in which the accumulation and release of electrons in Co were responsible for the evolution of its electronic structure and thus the magnetic response was observed.The work provides a new understanding of the charge storage mechanism of the conversion electrode,and reveal the profound relationship between heterogeneous catalysis and interfacial dynamics.The deeper understanding of this work provides implications for better design of lithium batteries with better performance.