Theoretical and Computational Chemistry

Elementary Decomposition Mechanisms of Lithium Hexafluorophosphate in Battery Electrolytes and Interphases

Authors

  • Evan Spotte-Smith Lawrence Berkeley National Laboratory & University of California Berkeley ,
  • Thea Petrocelli Lawrence Berkeley National Laboratory & University of California Berkeley & Cabrillo College ,
  • Hetal Patel Lawrence Berkeley National Laboratory & University of California Berkeley ,
  • Samuel Blau Lawrence Berkeley National Laboratory ,
  • Kristin Persson Lawrence Berkeley National Laboratory & University of California Berkeley

Abstract

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

Version notes

Small changes in response to editorial comments.

Content

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Supplementary material

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Supporting Information
Data availability statement; computational methods; discussion of additional reaction mechanisms for LiPF6 decomposition.

Supplementary weblinks

Data for "Elementary Decomposition Mechanisms of Lithium Hexafluorophosphate in Battery Electrolytes and Interphases"
Structural and thermochemical data used for this study