It is well known that the electrolyte in a battery plays a crucial role in the performance of a battery and its safety. Despite the widespread use of non-aqueous electrolytes (i.e. LiPF6/EC), they are still plagued by numerous shortcomings.By replacing LiPF6 with LiTFSI salt that is more stable, and EC with PC having a much lower melting point, the electrolyte will have improved thermal stability, chemical stability and ion conduction at room temperature. However, LiTFSI has well known problems with Al corrosion and PC has gained notoriety for its inability to form a stable SEI. Despite these issues, it is known that Al corrosion can be inhibited and that PC can be successfully used as a solvent in concentrated electrolytes. In a cell with a typical dilute electrolyte, the inner Helmholtz layer is dominated by free solvent molecules, as opposed to salt anions in the case of concentrated electrolytes. The SEI formed on the electrodes of the different electrolyte concentration systems are dominated by the elemental compositions in their respective inner Helmholtz layers. For high concentration electrolyte systems, the evolution of the SEI and the changes in microstructure have not been reported via operando studies, i.e. the dynamic process. We will present the results from a novel cell used for operando SANS measurements. Figure 1 shows the SANS data as a function of the voltage for the 1M LiTFSI/PC electrolyte system. The SEI and microstructure information is extracted and discussed. XPS data are used to study detailed elemental compositions of the SEI at different points in the electrochemical profile during the first discharge.

Effects of salt concentration on microstructure and SEI formation in hard carbons: An operando SANS and XPS study

256th National Meeting (2018)

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