Lespes Nicolas, Filhol Jean-Sébastien
Institut Charles Gerhardt-CNRS 5253 and Université de Montpellier, Place Eugène Bataillon, 34 095 Montpellier Cédex 5, France.
Réseau sur le Stockage Electrochimique de l'Energie (RS2E), CNRS FR3459, 80039 Amiens Cedex, France.
J Chem Theory Comput. 2015 Jul 14;11(7):3375-82. doi: 10.1021/acs.jctc.5b00170.
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.
本文聚焦于在电化学密度泛函理论（DFT）计算中隐式溶剂的使用。我们研究了隐式溶剂可极化连续介质模型（PCM）的必要性和局限性。为了恢复表面的适当电化学行为，特别是合适的电势标度，溶剂模型被确定为必不可少的：在高介电常数的极限情况下，表面电容变得与模型中使用的板间空间无关，因此，电化学性质成为界面结构的固有特性。我们表明，计算得到的表面电容不仅取决于隐式溶剂的介电常数，还取决于应精确调整的溶剂腔参数。然后将该模型应用于锂/电解质界面，以检验其计算热力学平衡性质的能力。与真空方法相比，使用纯隐式溶剂方法能够恢复Li(+)/Li氧化还原对更合理的平衡电势，但该电势仍偏离1.5 V。然后，加入明确的溶剂分子改善了对第一溶剂化层中溶剂-Li(+)化学键的描述，并能在100 mV范围内恢复实验值。最后，我们表明氧化还原活性中心涉及Li(+)的第一溶剂化层，这表明了锂离子电池中观察到的溶剂解离的特定途径。
