Theoretical Study of Li Migration in Lithium–Graphite Intercalation Compounds with Dispersion-Corrected DFT Methods

Abstract

Structural, energetic, electronic, and defect properties of lithium−graphite intercalated compounds (LiC 6n (n = 1, 2)) are investigated theoretically with periodic quantum-chemical methods. Calculated properties obtained with a gradient-corrected density functional theory (DFT) method and a dispersion-corrected DFT method (DFT-D3-BJ) are compared. The DFT-D3-BJ method gives better agreement with experiment for the structural parameters and Li intercalation energy compared to the uncorrected DFT approach, showing that interlayer interactions due to the van der Waals forces play an effective role in graphite and LiC 6n compounds. In agreement with the literature, the calculated density of states (DOS) show that graphite is metallic with a low DOS at the Fermi level, whereas LiC 6n compounds have a high DOS at the Fermi level. Between the considered point defects, V Li and Li i , the energy needed to form Li point defects is smaller if solid Li is used as reference. A moderate relaxation is observed for the atoms surrounding the Li defect. Competing pathways for Li diffusion in LiC 6n compounds are investigated using the climbing-image nudged elastic band approach. Two different mechanisms for Li diffusion are observed, the vacancy mechanism and the Frenkel mechanism. For both cases, Li migration pathways along the ab plane and along the c crystallographic axis are investigated. A large activation barrier along the c crystallographic direction indicates that Li does not diffuse in the c direction. The calculated activation barriers for Li diffusion in the ab plane are consistent with previous experimental investigations.

Diffusion of alkali metals in the first stage graphite intercalation compounds by vdW-DFT calculations

“…The migration along the crystallographic c-axis through a hexagonal carbon ring is prohibited due to the high energy barrier. 29,30 The diffusion process in AMGICs can thus be characterised as 2D diffusion or in-plane diffusion. 27,46 As illustrated in Figure 2b, there are two possible inplane migration paths in the MC 6 structure: a straight path going over the top of carbon atoms and a curved path travelling over carbon bridges and the hollow of a carbon ring.…”

1‐Aza‐15‐Crown‐5 Functionalized Graphene Oxide for 2D Graphene‐Based Li+‐ion Conductor

“…Thus, aza-crown-functionalized graphene selectively captures Li + ions in its cage. This Li + -ion bound aza-crown functionalized graphene upon heating at 113 °C generated free Li + ions due to breakdown of aza-crown and formed LiC 6 -type moiety as a result of cation-π interaction of Li + and six carbon atoms of the hexagon in the graphene lattice. Migration of these Li + ions on graphene surface is investigated.…”

Computational studies of solid-state alkali conduction in rechargeable alkali-ion batteries

“…A number of recent studies of Li/Na diffusion in graphitic materials have included the vdW interactions using vdW functionals [137][138][139] or dispersion corrections. 140 The use of vdW functionals significantly improves the agreement with experimental results for alkali (Li, Na, K) diffusion in graphite.…”