Electrolyte Study for High-Nickel LiNi 0.9 Mn 0.05 Co 0.05 O 2 Cathodes

Abstract

With an increasing demand for intermittent renewable energy and electric vehicles, it is imperative to develop lithium-ion batteries with Earth-abundant cathode materials. Cobalt (Co) is preferred to be kept at a minimum because of its high cost and limited mining options, yet it has played an essential role in the high-performance transition metal oxides (TMOs). Herein, we report work from Argonne National Laboratory, conducted under the U.S. DoE’s Vehicle Technologies Office, Deep Dive consortium on Next-Generation Cathodes, to optimize electrolytes for LiNi 0.9 Mn 0.05 Co 0.05 O 2 . LiNi 0.9 Mn 0.05 Co 0.05 O 2 is a high-Ni TMO benchmark as it outperforms most other TMOs under standard cycling conditions. In this study, we use the figure-of-merit approach to optimize electrolytes for this novel cathode material. Dual-salt carbonate electrolytes containing lithium difluorooxyphosphate and hexafluorophosphates were found to be the best for capacity retention and slowing the impedance rise. Transition metal dissolution and lithium inventory losses in the solid electrolyte interface were found to be the major causes for capacity fade.