New Electrolyte Composition for High-Voltage Lithium-Ion Cathodes – Enhancing the Cycling Stability in Half- and Full-Cells

Abstract

The steadily rising utilization of lithium-ion batteries for large-scale applications, in particular, electric vehicles requires the development of cell chemistries that offer increased energy and power densities.1,2 Essentially, there are two options to enhance the energy density: Increasing the capacity of the employed active materials and/or elevating the full-cell voltage by switching to high-voltage cathode materials. The latter, however, face the great challenge to identify a suitable electrolyte composition, as commonly used organic carbonate-based electrolyte are not sufficiently stable towards oxidation. To avoid the resulting detrimental side reactions, the use of electrolyte additives is easily implementable into common cell manufacturing technologies and, thus, very cost-efficient.3,4 For such reason, a plethora of electrolyte additives has been reported in recent years, but frequently these additives have been proven only to enhance the performance for selected cathode materials, while particularly the evaluation with graphite-based anodes has been commonly overlooked. Herein, we report on a new electrolyte composition, incorporating functional electrolyte additives for high-voltage cathode materials like LiNi0.5Mn1.5O4 or 5V-olivines, which moreover reveal a beneficial impact also for graphite-based anodes and, consequently, also in lithium-ion full-cells. As a result, lithium-ion half- and full-cells with a cell voltage of >4.5 V show a greatly enhanced cycling stability, increased capacities, and improved efficiencies. References B. Scrosati, J. Hassoun, and Y.-K. Sun, Energy Environ. Sci., 4, 3287 (2011).D. Bresser et al., J. Power Sources, accepted manuscript (2018).S. S. Zhang, J. Power Sources, 162, 1379–1394 (2006).J. Kalhoff, G. G. Eshetu, D. Bresser, and S. Passerini, ChemSusChem, 8, 2154–2175 (2015).