Lithium intercalation edge effects and doping implications for graphite anodes

Peng, Chao; Mercer, Michael; Skylaris, Chris‐Kriton; Kramer, Denis

doi:10.1039/c9ta13862e

“…The present model lacks the dependence of the diffusion coefficient and

k^{0}

on the state of charge, and this information may be obtained from kinetic Monte Carlo simulations (kMC), as illustrated in the middle of the figure. The energy barriers for diffusion and (de)intercalation of Li + (from)into the electrode required for the kMC simulation, could be estimated with DFT and/or empirical data [48,49] (left of the figure). This information would be fed into the kMC model, to study the changes of

D

with

x

in a canonical ensemble (C‐kMC) and the variations of

k^{0}

with the state of charge in a Grand Canonical ensemble (GC‐kMC).…”

Section: Resultsmentioning

confidence: 99%

Voltammetric Behaviour of LMO at the Nanoscale: A Map of Reversibility and Diffusional Limitations

Gavilán-Arriazu

¹

,

Mercer

²

,

Barraco

³

et al. 2021

Self Cite

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Understanding and optimizing single particle rate behaviour is normally challenging in composite commercial lithium‐ion electrode materials. In this regard, recent experimental research has addressed the electrochemical Li‐ion intercalation in individual nanosized particles. Here, we present a thorough theoretical analysis of the Li+ intercalation voltammetric behaviour in single nano/micro‐scale LiMn2O4 (LMO) particles, incorporating realistic interactions between inserted ions. A transparent 2‐dimensional zone diagram representation of kinetic‐diffusional behaviour is provided that allows rapid diagnosis of the reversibility and diffusion length of the system depending on the particle geometry. We provide an Excel file where the boundary lines of the zone diagram can be rapidly recalculated by setting input values of the rate constant, k0 and diffusion coefficient,D . The model framework elucidates the heterogeneous behaviour of nanosized particles with similar sizes but different shapes. Hence, we present here an outlook for realistic multiscale modelling of real materials.

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“…Although we also introduced H-terminated surfaces into all of the oxygenated surface group systems that we considered, we do not expect these H-terminations to affect our results, as fully H-terminated surface has been proven both experimentally and computationally to be inactive towards interfacial reactions in LIBs. [21,[35][36][37] To determine the relative free energy for each species in a chemical reaction, this value needs to be established against a reference cell, which is the standard hydrogen electrode (SHE). At standard conditions of pH = 0 and p(H2) = 1 bar, the SHE reaction:…”

Section: Methodsmentioning

confidence: 99%

“…[5] Furthermore, in addition to the lowest surface energy argument, the (112 " 0) armchair facet was chosen to represent the edge surface as the armchair facets are found to be more suitable for LIB applications than the zigzag facets, which promotes lithium dendrite formation and have detrimental impact on charge/discharge rates. [21] The graphite surfaces were modeled in a box of 13.54 x 12.70 Å 2 for (112 " 0) edge and 9.78 x 12.70 Å 2 for basal plane with a vacuum gap of at least 10 Å in the z-direction. [33] Surfaces were functionalized with (C-OH/C-H), (C=O/2C-H), (O=C-OH/CH3), and (O=C-H/C-H) pairs to represent hydroxyl, ketonic, carboxyl, and carbonyl oxygen functional groups as produced from a complete water dissociation, in accordance to the following reactions:…”

Section: Methodsmentioning

confidence: 99%

“…[12] Despite this difficulty, a complete understanding of the interfacial structure, including the composition of surface functionalization, is of paramount importance in improving the performance of LIBs, as it plays a crucial role in the lithium intercalation rate, the charge/discharge performance, and dendrite formation. [21] Furthermore, it also has a significant impact on the structures, morphologies and properties of the SEI, [22,23] which in turn affects the quality and lifetime of the LIBs.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

The Composition of Oxygen Functionals Groups at the Surface of Carbon-Based Graphitic Anode

Intan

¹

,

Pfaendtner

²

2021

Preprint

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In lithium-ion batteries (LIBs), the quality of a solid electrolyte interphase (SEI) that forms at the electrode/electrolyte interface substantially affects the stability and lifetime of the devices. One of the major determinants of the morphology and properties of SEI is the surface structure and composition of the graphitic anode used. The presence of oxygenated surface groups at the graphitic anode facilitates the formation of SEI at the interface that stabilizes LIBs. A series of DFT calculations reveal that at typical operating conditions (temperature, pH) of LIBs, the (1120) edge facet of graphite anode will be fully oxygenated, while the basal sites remain unsaturated. The oxygen functional groups at the edge sites are comprised of mostly hydroxyl and ketonic groups, with carboxyl and carbonyl groups are present in small amounts. Furthermore, we observe transformation of carbonyl group into ketonic group in the presence of empty surface carbon sites, which further stabilize the graphite surface. Meanwhile, carboxyl groups are more stable when all surface sites within a carboxyl layer are all populated. On the contrary to the edge plane, a small amount of oxygen functional groups may be forced to adsorb on the basal surface upon application of an external potential.

show abstract

“…[5] Furthermore, in addition to the lowest surface energy argument, the (112 " 0) armchair facet was chosen to represent the edge surface as the armchair facets are found to be more suitable for LIB applications than the zigzag facets, which promotes lithium dendrite formation and have detrimental impact on charge/discharge rates. [21] The graphite surfaces were modeled in a box of 13.54 x 12.70 Å 2 for (112 " 0) edge and 9.78 x 12.70 Å 2 for basal plane with a vacuum gap of at least 10 Å in the z-direction.…”

Section: Methodsmentioning

confidence: 99%

The Composition of Oxygen Functionals Groups at the Surface of Carbon-Based Graphitic Anode

Intan

¹

,

Pfaendtner

²

2021

Preprint

2

0

View full text Add to dashboard Cite

In lithium-ion batteries (LIBs), the quality of a solid electrolyte interphase (SEI) that forms at the electrode/electrolyte interface substantially affects the stability and lifetime of the devices. One of the major determinants of the morphology and properties of SEI is the surface structure and composition of the graphitic anode used. The presence of oxygenated surface groups at the graphitic anode facilitates the formation of SEI at the interface that stabilizes LIBs. A series of DFT calculations reveal that at typical operating conditions (temperature, pH) of LIBs, the (1120) edge facet of graphite anode will be fully oxygenated, while the basal sites remain unsaturated. The oxygen functional groups at the edge sites are comprised of mostly hydroxyl and ketonic groups, with carboxyl and carbonyl groups are present in small amounts. Furthermore, we observe transformation of carbonyl group into ketonic group in the presence of empty surface carbon sites, which further stabilize the graphite surface. Meanwhile, carboxyl groups are more stable when all surface sites within a carboxyl layer are all populated. On the contrary to the edge plane, a small amount of oxygen functional groups may be forced to adsorb on the basal surface upon application of an external potential.

show abstract

Lithium intercalation edge effects and doping implications for graphite anodes

Abstract: The interface between the electrolyte and graphite anodes plays an important role for lithium (Li) intercalation and has significant impact on the charging/discharging performance of Lithium-Ion Batteries (LIBs).

Cited by 35 publications

References 87 publications

Voltammetric Behaviour of LMO at the Nanoscale: A Map of Reversibility and Diffusional Limitations

Voltammetric Behaviour of LMO at the Nanoscale: A Map of Reversibility and Diffusional Limitations

The Composition of Oxygen Functionals Groups at the Surface of Carbon-Based Graphitic Anode

The Composition of Oxygen Functionals Groups at the Surface of Carbon-Based Graphitic Anode

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