Electrolyte decomposition controls the life and death of Li-ion batteries (LIB), contributing to LIB protection through the formation of solid electrolyte interphase (SEI) layers as well as irreversible capacity loss over a battery's life. Though major strides have been made to understand the decomposition of common LIB solvents, salt decomposition mechanisms remain elusive. In this work, we use density functional theory to explore the reactivity of lithium hexafluorophosphate (LiPF6) salt under SEI formation conditions. Our calculations suggest that LiPF6 forms POF3 primarily through rapid chemical reactions with Li2CO3, while hydrolysis should be kinetically limited at moderate temperatures. We further find that the proposed autocatalysis of POF3 is selective, as POF3 prefers to react with highly charged oxyanions (e.g. oxygen in Li2CO3) compared with less charged alternatives (e.g. oxygen in LiHCO3, H2CO3). These results indicate a means of interphase design in LIBs, suggesting that LiPF6 reactivity should be controlled by varying the abundance of carbonate species during battery charging.

Revealing the decomposition mechanisms of lithium hexafluorophosphate in battery electrolytes and interphases by first-principles simulations

Where thousands of chemistry professionals meet to share ideas and advance scientific and technical knowledge. Spring 2023 abstracts, posters, and presentations will launch at the end of March.

ACS Spring 2023

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.