The development of portable smart devices and long-life electric vehicles has put forward higher requirements for the energy density of rechargeable secondary batteries. When the lithium negative electrode is matched with the sulfur positive electrode, the capacity of the lithium-sulfur battery is as high as 2600 Wh kg-1, which will be suitable for electric vehicles with high energy density requirements in the future. In the early sulfur cathode research, starting from the structure design and surface functionalization of nanomaterials (Journal of Power Sources, 2016, 321, 193; Nano Energy, 2017, 40, 390), different active nano-catalyst composite materials were prepared ( ACS Applied Materials & Interfaces, 2020, 12, 12727; Energy Storage Materials, 2020, 28, 375; ChemSusChem, 2020, 13, 3404), and use in-situ spectroscopy to explore its related mechanism (Energy Storage Materials, 2019, 18 , 246; Energy & Environmental Materials, 2020, DOI: 10.1002/eem2.12152). Among many negative electrodes, the metal lithium negative electrode has a high theoretical specific capacity and a low electrode potential. However, short life and poor stability have hindered its commercialization process. The lithium metal negative electrode faces challenges: the brittleness and porosity of the solid electrolyte interphase (SEI) formed by electrochemistry causes the uneven deposition and dissolution of lithium metal, and finally the formation of dendrites; the deformation and powdering of the electrode structure caused by volume expansion. These issues are not independent of each other, but are inherently related. In response to the above problems, Zhang Yuegang, a professor at the Suzhou Institute of Nanotechnology and Nanobionics, Chinese Academy of Sciences, and researcher Lin Hongzhen’s team, from the perspective of surface functionalization, prepared an ordered structure of organic/inorganic SEI layer on the surface of lithium metal, and selected in-situ and frequency Vibrational spectroscopy means to study its related mechanism. Different from the conventional disordered structure or single-component SEI anode (Figure 1), the study uses the highly reactive Pyr13FSI ionic liquid to self-assemble on the lithium metal surface to form an ordered structure of organic/inorganic SEI layer, through the interface selectivity and frequency Vibrational spectroscopy (SFG), X-ray spectroscopy (XPS) and atomic force spectroscopy (AFM) characterize the existence of organic and inorganic layers in the ordered structure (Figure 2). In the electrochemical test process, the LiFSI-based ether electrolyte system reported by the previous research group (ACS Applied Materials & Interfaces, 2019, 11, 30500) was selected, and the pre-treated lithium metal electrode was under the condition of up to 10 mA cm-2 It exhibits excellent reversibility and stability, and maintains high coulombic efficiency even at a large deposition dissolution capacity of 3 mA h cm-2. These electrochemical results are better than most reported literature. The SEM image after the cycle shows that the surface of the pre-treated lithium metal is smooth and flat, while the original lithium sheet has many cracks and powders. Furthermore, the team selected the in-situ electrochemical and frequency vibration spectroscopy technology independently designed and developed. The in-situ SFG test results showed that the ordered organic/inorganic hybrid SEI layer hindered the adsorption of solvent molecules on the surface of lithium metal, and inhibited the inhibition of lithium branches. Crystal formation has advantages. Related research results were published on Advanced Functional Materials with the title of In-situ self-assembly of ordered organic/inorganic dual-layered interphase for achieving long-life dendrite-free Li metal anodes in LiFSI-based electrolyte, Dr. Wang from Suzhou Institute of Nanotechnology Jian is the first author of the paper. The research work is supported by the National Key Research and Development Program, the National Natural Science Foundation of China and the Alexander von Humboldt Foundation of Germany. Guangzhou Jointair Co., Ltd. , https://www.jointairaccessories.com
Figure 1. Schematic diagram of the structure of the SEI layer on the surface of lithium metal 
Figure 2. The self-assembly evolution process of ordered structure SAHL-Li and the characterization of the interface organic and inorganic layers
Figure 3. Electrochemical stability of ordered double-layer SAHL SEI layer modified lithium metal electrode
Figure 4. Study on the mechanism of in situ SFG on SEI
Suzhou Nano Institute has made progress in the research of high-performance lithium metal batteries