Affiliation:
1. Molecular Electrochemistry for Energy Laboratory School of Energy Science and Engineering Vidyasirimedhi Institute of Science and Technology (VISTEC) Rayong 21210 Thailand
2. Institute for Advanced Study and College of Food and Biological Engineering Chengdu University Chengdu 610106 China
3. ICGM Université de Montpellier CNRS Montpellier 34293 France
4. Max Planck Institute of Colloids and Interfaces Am Mühlenberg 1 14476 Potsdam Germany
Abstract
AbstractA water‐in‐salt electrolyte is a highly concentrated aqueous solution (i.e., 21 mol LiTFSI in 1 kg H2O) that reduces the number of water molecules surrounding salt ions, thereby decreasing the water activity responsible for decomposition. This electrolyte widens the electrochemical stability window via the formation of a solid electrolyte interphase (SEI) at the electrode surface. However, using high concentration electrolytes in Li‐ion battery technology to enhance energy density and increase cycling stability remains challenging. A parasitic reaction, called the hydrogen evolution reaction, occurs when the reaction operates at a lower voltage. It is demonstrated here that a micrometric white layer is indeed a component of the SEI layer, not just on the nanoscale, through the utilization of an operando high‐resolution optical microscope. The results indicate that LiTFSI precipitation is the primary species present in the SEI layer. Furthermore, the passivation layer is found to be dynamic since it dissolves back into the electrolyte during open circuit voltage.
Funder
National Research Council of Thailand
H2020 Marie Skłodowska-Curie Actions
Subject
Biomaterials,Biotechnology,General Materials Science,General Chemistry