Using Implicit Solvent in Ab Initio Electrochemical Modeling: Investigating Li⁺/Li Electrochemistry at a Li/Solvent Interface

Abstract

This paper focuses on the use of implicit solvent in electrochemical density functional theory (DFT) calculations. We investigate both the necessity and limits of an implicit solvent polarizable continuum model (PCM). In order to recover the proper electrochemical behavior of the surface and, in particular, a proper potential scale, the solvent model is determined to be mandatory: in the limit of a high dielectric constant, the surface capacitance becomes independent of the interslab space used in the model and, therefore, the electrochemical properties become intrinsic of the interface structure. We show that the computed surface capacitance is not only dependent on the implicit solvent dielectric constant, but also on the solvent cavity parameter that should be precisely tuned. This model is then applied to the Li/electrolyte interface in order to check its ability to compute thermodynamic equilibrium properties. The use of a purely implicit solvent approach allows the recovery of a more reasonable equilibrium potential for the Li(+)/Li redox pair, compared to vacuum approaches, but a potential that it is still off by 1.5 V. Then, the inclusion of explicit solvent molecules improves the description of the solvent-Li(+) chemical bond in the first solvation shell and allows recovery of the experimental value within 100 mV. Finally, we show that the redox active center involves the first solvation shell of Li(+), suggesting a particular pathway for the observed solvent dissociation in Li-ion batteries.

Continuum embeddings in condensed‐matter simulations

“…Applications of condensed-matter continuum approaches in electro-chemistry and electro-catalysis in wet environments are among the main purposes that have driven these recent developments. [29,34,105,[107][108][109][110][113][114][115][116][117][118][119][120][121][122] There are different simulation strategies of increasing complexity that can be attempted and that could take substantial advantage from the use of continuum embedding techniques.…”

Approaching the self-consistency challenge of electrocatalysis with theory and computation

“…Theoretical electrocatalysis is closely interwoven with the quintessential theories of electrified interfaces [27] and charge transfer [28,29,30] and it draws upon inventories of condensed matter physics, surface science, heterogeneous catalysis, and chemical kinetics. Modern developments in this multidisciplinary field circulate under the label first-principles electrochemistry (FPEC) [31,32] or alike [33].…”

Evaluating Solvent Effects at the Aqueous/Pt(111) Interface

“…Implicit models require careful evaluation of their accuracy and limitations. Implicit solvation models have also been recently used in modeling electrochemical interfaces and reactions …”