Thermodynamics of lithium intercalation into graphite studied using density functional theory calculations incorporating van der Waals correlation and uncertainty estimation
Year: 2016
Type: preprint
Abstract: Graphite is the most widely used and among the most widely-studied anode materials for lithium-ion batteries. Lithium intercalation into graphite has been extensively studied theoretically using density functional theory (DFT) calculations, complemented by experimental studies through X-ray diffraction, spectroscopy, optical imaging and other techniques. However, previous theoretical studies have not directly included van der Waals (vdW) interactions in their density functional theory calculations and vdW interactions play a crucial role in determining the stable phases. In this work, we present a first principles based model using DFT calculations, employing Bayesian Error Estimation Functional with van der Waals (BEEF-vdW) as the exchange correlation functional, and statistical thermodynamics to determine the phase transformations and subsequently, the thermodynamic intercalation potential diagram. We explore the entire configurational phase space by determining the important interactions and applying cluster expansion technique using these interactions. We show that in order to accurately determine the interactions, it is important to employ an exchange correlational functional that is capable of capturing vdW interactions. Using our model, we identify stable phases of Li$_x$C$_6$ at x = 0.047, 0.167, 0.333, 0.5, 0.667, 0.75 and 1. We find stages 1-4 during initial lithiation followed by phase transition to mixture of stages 1-3 followed by stages 1-2 and finally stage 1. We report a methodological framework for determining the uncertainty associated with DFT calculated intercalation potentials. Given the subtle differences in energy between lithium intercalation into graphite and lithium plating (0.1 eV), we believe such an error estimation framework is crucial to know the reliability of DFT predictions.
Source: arXiv (Cornell University)
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2498596174