Glyoxales As New Electrolytes for Si/Graphite-Anodes in Lithium-Ion Batteries: Analysis of the Solid-Electrolyte Interphase

Abstract

Electrolytes play a crucial role when considering the safety aspects of a Lithium-ion battery. Most commonly, linear and cyclic carbonate-based electrolytes are used commercially. Their advantage lies in the combination of low viscosity and high dielectric constant. However, they display various safety issues such as a limited temperature stability window and high toxicity of the used Li-salt[1]. A new promising alternative are glyoxal based electrolytes using solvents such as tetraethoxy glyoxal (TEG) and tetramethoxy glyoxal (TMG)[2]. Both solvents display low viscosity, low toxicity, high flash points, and very low melting points. Previous works have shown that TEG containing electrolytes display good electrochemical performance in graphite and lithium iron phosphate half-cells as well as in NMC||graphite full-cells[2],[3],[4].With this work, we report the first use of TEG and TMG based electrolytes for silicon-graphite anodes. Our results show that in terms of capacity retention the TEG-based electrolyte outperforms TMG as well as the 2 reference electrolytes, namely LP30 (LiPF6 in EC/DMC) and L-E/D (LiTFSI-EC/DMC) (see figure). In this presentation, we focus on is the analysis of the solid electrolyte interphase (SEI) formed by these electrolytes. The interphase was studied by photoelectron spectroscopy (XPS) at specific potentials during SEI formation in the first cycle as well as after 100 cycles. We correlate SEI composition and thickness with the electrochemical performance depending on electrolyte composition, suggesting that TEG shows a thinner yet more stable SEI.