Paul Kent Publications

Solid electrolyte interphase formation and electrolyte reduction at Li-ion battery graphite anodes: a first-principles molecular dynamics study

Journal of Physical Chemistry C 116 24476 (2012)

Understanding the nature and formation of the solid-electrolyte interphase (SEI) formed in electrochemical storage devices, such as Li-ion batteries, is most important for improving functionality. Few experiments exist which adequately probe the SEI, particularly in-situ. We perform predictive ab initio molecular dynamics simulations of the anode-electrolyte interface for several electrolytes and interface functionalizations. These show strongly differing effects on the reducibility of the electrolyte. Electrolyte reduction occurs rapidly, on a picosecond timescale. Orientational ordering of electrolyte near the interface precedes reduction. The reduced species depend strongly on surface functionalization and presence of LiPF6 salt. While LiPF6 salt in ethylene-carbonate is more stable at a hydrogen-terminated anode, oxygen/hydroxyl termination causes spontaneous dissociation to form LiF and other fluorophosphates. LiF migrates to the interface creating chain-like structures, consistent with experimental observations of LiF agglomeration. Inorganic products such as LiF and Li2CO3 migrate closer to the anode than purely organic components, consistent with their more ionic character. Significantly, we conclude that while the electrolyte reduction occurs at the m

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