Tracking Degradation of Sulfolane-Based Electrolytes in 5 V LNMO Cells

Abstract

Lithium-ion batteries (LIBs) are today the most used energy storage for portable electronics and electric vehicles – but are laden with concerns of materials scarcity and availability, alongside performance and cost. The development of high-voltage cobalt-free cathode active materials, such as LiNi0.5Mn1.5O4 (LNMO), represents one promising route for next-generation LIBs, due to a combination of high capacity and low cost. Combining LNMO with conventional LIB electrolytes, based on carbonate solvents, however, typically leads to severe capacity fading due to a range of different degradation mechanisms1, not the least due to the high electrochemical potential reached during charge, up to 5 V vs. Li+/Li°.Here we use a range of sulfolane-based electrolytes to improve the stability2 and track the degradation by intermittent current interruption (ICI), which is a rather new protocol to determine the internal resistance of battery cells during cycling3. The ICI data is presented in the form of heat maps, in order to better visualize the variation of internal resistance as function of the cell voltage. Furthermore, Raman spectroscopy is used to identify the decomposition products resulting from the degradation and the data is correlated with the ICI data. Overall this allows us to shine further light on the prospects of sulfolane-based electrolytes for 5 V cells as compared to conventional LIB electrolytes such as e.g. LP40.References Guo, K. et al. High‐Voltage Electrolyte Chemistry for Lithium Batteries. Small Science 2, 2100107 (2022).Xu, J. Critical Review on cathode–electrolyte Interphase Toward High-Voltage Cathodes for Li-Ion Batteries. Nano-Micro Letters vol. 14 (2022).Yin, L. et al. Implementing intermittent current interruption into Li-ion cell modelling for improved battery diagnostics. Electrochim Acta 427, (2022).