Due to the close relationship between the electrochemical performance of the electrochemical power source and the electrode / electrolyte interface process and the steps of charge transfer, ion transport, phase formation and conversion, understanding the interface process at the nanoscale is of great significance for device design and material optimization However, the operating environment of the energy system is very complex, involving the anhydrous anoxic environment, the organic / ionic liquid electrolyte system, the multiphase interface, the multi-electron reaction process and so on. Therefore, the targeted development of electrochemical interface high resolution in situ imaging Method to achieve real-time tracking and in-situ analysis of the electrochemical reaction process is also one of the challenges and difficulties of electroanalytical chemistry.
Wen Rui, Key Laboratory of Molecular Nanostructures and Nanotechnology, Institute of Chemistry, Chinese Academy of Sciences, is devoted to in-situ research and progress in the electrochemical process of lithium battery interface. In the previous work, they used the in situ Atomic force microscopy (AFM) captures the initial nucleation of the solid state electrolyte interface membrane (SEI) on a highly oriented pyrolytic graphite (HOPG) surface of nanoscale Li-ion batteries in an ionic liquid such as' BMP '+' FSI'- , The gradual growth and the evolution of film formation, and revealed the interfacial properties of SEI films in different ionic liquids and their correlation with cell performance. Relevant results have been published on ACS Applied Materials & Interfaces.
Further, the researchers conducted a series of studies on the electrochemical reaction at the interfaces of lithium-sulfur batteries with high theoretical energy density (2600 Wh / kg). Electrochemical AFM and spectroscopic analysis were used to characterize the reduction products during lithium sulfur charging and discharging The in-situ morphologies of the interface and growth / dissolution of lithium sulfide and lithium persulfate are monitored (Figure 1). It is also suggested that the interfacial aggregation caused by irreversible reaction of lithium persulfate during cycling leads to electrode passivation and cell degradation One of the reasons is that in-situ imaging under constant current control shows that the current density affects the morphology of the interface and the type of sediment, revealing the structural-property correlation intuitively. The relevant results were published on the Angewandte Chemie International Edition.
Recently, researchers used electrochemical AFM to further explore the interface behavior and reaction mechanism of lithium-sulfur batteries in LiFSI-based electrolyte at high temperature (Figure 2) .Studies found that at a high temperature 60 ℃, the cathode / electrolyte interface discharge In the process, a functional interface film composed of LiF nano-particles is formed in situ and the long-chain lithium polysulfide in the electrolyte is captured by the physical size effect and chemisorption. This process is beneficial to inhibit the polysulfide shuttling effect and Side reactions and enhance the reversibility of the electrochemical reaction at the interface.The in situ characterization and analysis provide a direct interface mechanism explanation for high temperature electrochemical behavior at the nanoscale and also provide electrolyte design and performance for lithium-sulfur batteries Ascension provides guidance and ideas. Relevant results are published on the Angewandte Chemie International Edition.
Research has been supported by the Ministry of Science and Technology, the National Natural Science Foundation of China and the Chinese Academy of Sciences.
