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Elementary Decomposition Mechanisms of Lithium Hexafluorophosphate in Battery Electrolytes and Interphases
journal contribution
posted on 2022-12-05, 20:14 authored by Evan Walter
Clark Spotte-Smith, Thea Bee Petrocelli, Hetal D. Patel, Samuel M. Blau, Kristin A. PerssonElectrolyte 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.
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rapid chemical reactionsirreversible capacity lossinorganic carbonate specieshighly anionic oxygenscommon lib solvents6 sub3 sub2 subelementary decomposition mechanismssei formation conditionsresults suggestresults providereactivity mayproposed autocatalysispreferentially reactsoutstanding challengemoderate temperaturesmajor strideslithium hexafluorophosphatekinetically limitedion batteriesinterphase designidentify selectivitybattery ’battery electrolytes
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