Elementary Decomposition Mechanisms of Lithium Hexafluorophosphate in Battery Electrolytes and Interphases

Electrolyte decomposition constitutes an outstanding challenge to long-life Li-ion batteries (LIBs) as well emergent energy storage technologies, contributing protection via solid electrolyte interphase (SEI) formation and irreversible capacity loss over a battery’s life. Major strides have been made understand the breakdown of common LIB solvents; however, salt mechanisms remain elusive. In this work, we use density functional theory explain lithium hexafluorophosphate (LiPF6) under SEI conditions. Our results suggest that LiPF6 forms POF3 primarily through rapid chemical reactions with Li2CO3, while hydrolysis should be kinetically limited at moderate temperatures. We further identify selectivity in proposed autocatalysis POF3, finding preferentially reacts highly anionic oxygens. These provide means design LIBs, indicating reactivity may controlled by varying abundance or distribution inorganic carbonate species limiting transport PF6– SEI.