Kavli Affiliate: Kristin A. Persson
| First 5 Authors: Peichen Zhong, Peichen Zhong, , ,
| Summary:
Despite decades of study, the identity of the dominant ceLi+-conducting
phase within the inorganic SEI of Li-ion batteries remains unresolved. While
the mosaic model describes LiF/ceLi2O/ceLi2CO3 nanocrystallites within a
disordered matrix, these crystalline phases inherently offer limited ionic
conductivity. Growing evidence suggests that interfaces, grain boundaries, and
amorphous phases may instead host the primary fast-ion pathways. Motivated by
mixed-anion electrolyte decomposition products, we combine diffusion-based
generative structure prediction with machine-learning interatomic potentials
(MLIPs) to interrogate lithium difluorophosphate (ceLiPO2F2), a key
decomposition product of phosphorus- and fluorine-containing electrolytes. We
identify a stable crystalline polymorph and, through MLIP-accelerated molecular
dynamics, show that the amorphous counterpart is more conductive, with
projected room-temperature $sigma$ $approx$ 0.18 mS cm$^-1$ and
$E_mathrma$ $approx$ 0.40 eV. This enhancement is attributed to structural
disorder, which flattens the Li site-energy landscape, and to a low formation
energy for Li-interstitial defects, which supplies additional mobile carriers.
We present mixed-anion, amorphous Li–P–O–F phases as promising candidates
for the ceLi+-conducting medium of the inorganic SEI, offering a path
forward for engineering improved battery interfaces.
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