Lithium Storage in Bowl-like Carbon: The Effect of Surface Curvature and Space Geometry on Li Metal Deposition

Abstract

Dendrite growth severely hinders the practical use of lithium metal as an ideal battery anode. To realize controlled Li plating, tremendous efforts have been focused on modifying the lithiophilicity chemistry of the anode hosts. Instead, we attempt to address this issue from a geometry perspective. We herein adopt carbon nanobowls (CBs) as a model host to study the geometry-guided Li growth behaviors by in situ electron microscopy. The strong effect of surface curvature is clearly demonstrated: Li metal is always guided to deposit on the concave surface of an isolated CB instead of the convex surface. The fully confined hollow cavity is more favorable for Li deposition in comparison to the partially confined spaces, such as the hemispherical concavity of a CB and interstitial voids between neighboring CBs. Density functional theory calculations elucidate that the geometry-guided Li growth is driven by the energy minimization associated with the formation of low-energy Li/C interfaces.

Mechanistic Probing of Encapsulation and Confined Growth of Lithium Crystals in Carbonaceous Nanotubes

“…This is essentially in line with our recent findings on the strong effect of surface curvature: a concave lithiophilic surface is energetically more favorable for Li deposition than its convex counterpart. [38] Moreover, the driving force for Li encapsulation, i.e., the drop in Gibbs free energy associated with the Li nucleation inside a nanotube compared to its outside nucleation (|ΔG in − ΔG out |), increases remarkably with the improved N/O content (Table S4, Supporting Information), agreeing with our experiments. This is similar to the fact that water tends to be absorbed into hydrophilic pores or channels under capillary force.…”

“…[ 36 ] In the case of single Li atom adsorption, our calculations show that the Li atom was preferably adsorbed in the center of the defect pores in all models (Figure 5a–d). [ 37,38 ] The calculated E b for DG, N‐DG, O‐DG, N/O‐DG are −4.89, −4.99, −4.84, and −5.11 eV, respectively, which are more negative than that of pristine graphene (−1.12 eV). This suggests that the presence of defects can effectively promote the lithiophilicity of graphene, which can be further enhanced by co‐doping of N and O, thus reducing the Li nucleation overpotential.…”

Visualizing the failure of solid electrolyte under GPa-level interface stress induced by lithium eruption

“…As {110} planes of b.c.c. metals have the lowest surface energy, they are therefore preferentially exposed on the surface of Li crystals, consistent with previous TEM observations 26 , 27 . Besides, the low-energy Li {002} and {112} planes prevailed alternately on the lower growing facet to adapt to the uneven LLZO surface, so as to minimize the overall energy of the expanding-Li|LLZO system.…”

Ion/Electron Redistributed 3D Flexible Host for Achieving Highly Reversible Li Metal Batteries

“…Fortunately, the 3D carbon frameworks with large specific area not only decrease local current density and inhibit Li dendrite growth, but also depress huge volume expansion, contributing to achieve highly reversible Li metal anodes with high energy density. [ 17 ] Thus, all kinds of novel 3D carbon matrixes, such as carbon fibers, [ 18,19 ] 3D graphene‐based skeletons, [ 20 ] and hollow carbon sphere, [ 21 ] have been verified. Among them, benefitting from the excellent mechanical property, free‐standing, low‐cost, and easy to large‐scale production, carbon fiber cloth (CFC) displays an enormous practical potential as a high‐performance host of Li metal anode.…”