Thermodynamics of Lithium Intercalation in Randomly Oriented High Graphene Carbon

Kadam, Rahul S.; Gadkaree, K. P.

doi:10.1155/2017/5391794

Cited by 4 publications

(7 citation statements)

References 14 publications

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“…The crystal structure of pure graphite exhibits a layered structure with a hexagonal lattice (P6 3 / mmc ) and lattice parameters of a = b = 2.464 Å and c = 6.711 Å . Upon lithium intercalation into graphite, binary Li‐GICs of different stage are formed . The stage of the LiC x compound represents the occupation of graphite interlayers by lithium, for example, in stage‐II compound each second graphite interlayer contains an intercalated lithium ion.…”

Section: Computational Details and Modelsmentioning

confidence: 99%

Comparative study of density functionals for the description of lithium‐graphite intercalation compounds

2019

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The lack of description of van der Waals interactions in layered materials such as graphite and binary graphite intercalation compounds remains a main drawback of conventional density functional theory. Two fundamentally different approaches to overcome this issue are the employment of semiempirical dispersion correction scheme such as Grimme dispersion correction or nonlocal density functionals. We carefully compare these two approaches for the description of the geometric structure and the thermodynamic stability of pure graphite and Li-GICs at different lithium concentrations and stages. Based on the computed formation energies, we also evaluate the lithium-graphite intercalation potential. We find that PBE-D3(BJ) accurately reproduces the lattice parameters and the interlayer binding energy of graphite, although it underestimates the thermodynamic stability of stage-II Li-GICs mainly due to overbinding of carbon atoms in pure graphite. The nonlocal van der Waals functionals optB88-vdW, optB86b-vdW, and revPBE-vdW show a good agreement with experiments concerning stability of Li-GICs of different stages, although they overestimate the van der Waals interactions in graphite. The experimentally determined decreasing step-function behavior of Li-graphite intercalation potential can be qualitatively reproduced only by employing the revPBE van der Waals functional, whereas the other density functionals fail in the description.

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Section: Computational Details and Modelsmentioning

confidence: 99%

Comparative study of density functionals for the description of lithium‐graphite intercalation compounds

2019

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“…We had earlier published the structure of ROHG carbon and predicted the mechanism of intercalation and deintercalation of lithium ion in ROHG carbon based on the thermodynamic study and Monte Carlo simulations. Figure 8 shows the predicted structure of ROHG carbon and Figure 9 shows the intercalation model [17]. Based on the Monte Carlo simulation, we have established that the ROHG carbon consists of cluster of convoluted and randomly oriented graphene platelets at high concentration as opposed to organized parallel graphene platelets in graphite ( Figure 10).…”

Section: Discussionmentioning

confidence: 99%

“…At 100% lithiation, graphite has a "x" value of 0.823, whereas ROHG carbon shows a "x" value of 0.764. However, ROHG carbon, due to its unique structure, is more suitable for high rate applications [17] and its performance in a full working lithium ion capacitor is discussed in detail in the following sections.…”

Section: Intercalation Curves From Half Cellmentioning

confidence: 99%

“…To this effect, we have earlier reported in detail the systematic investigation of the thermodynamics (entropy and enthalpy) of intercalation associated with lithium ion in a structurally novel carbon, called Randomly Oriented High Graphene (ROHG) carbon, and compared it to graphite [17]. The study clearly shows that a lower amount of energy is required for the lithium ion intercalation into the ROHG structure compared to graphite structure.…”

Section: Introductionmentioning

confidence: 99%

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Performance of Novel Randomly Oriented High Graphene Carbon in Lithium Ion Capacitors

Kadam

Gadkaree

2018

International Journal of Electrochemistry

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The structure of carbon material comprising the anode is the key to the performance of a lithium ion capacitor. In addition to determining the capacity, the structure of the carbon material also determines the diffusion rate of the lithium ion into the anode which in turn controls power density which is vital in high rate applications. This paper covers details of systematic investigation of the performance of a structurally novel carbon, called Randomly Oriented High Graphene (ROHG) carbon, and graphite in a high rate application device, that is, lithium ion capacitor. Electrochemical impedance spectroscopy shows that ROHG is less resistive and has faster lithium ion diffusion rates (393.7 × 10−3 S·s(1/2)) compared to graphite (338.1 × 10−3 S·s(1/2)). The impedance spectroscopy data is supported by the cell data showing that the ROHG carbon based device has energy density of 22.8 Wh/l with a power density of 4349.3 W/l, whereas baseline graphite based device has energy density of 5 Wh/l and power density of 4243.3 W/l. This data clearly shows advantage of the randomly oriented graphene platelet structure of ROHG in lithium ion capacitor performance.

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“…The difference between graphite and disordered (or randomly oriented) carbon has also been investigated. 18,19 Furthermore, entropy anomalies (or entropy jumps) have been found in the transition from stage 2 to stage 1 for x = 0.5, and, probably, from dilute-stage 1 to stage 4 for x ≈ 0.04 in Li x C 6 . 20 Recent studies have proposed the structure transition during Li intercalation based on the XRD profiles and the hysteretic behavior of the opencircuit voltage and entropy changes.…”

Section: Introductionmentioning

confidence: 96%

Thermodynamic Analysis of Li-Intercalated Graphite by First-Principles Calculations with Vibrational and Configurational Contributions

et al. 2021

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Li-ion batteries require quantitative analysis of the crystal structure change in the graphite electrode during charge/discharge reactions to improve their performance. Herein, we investigated the thermodynamically stable phases of Li x C6 and their structure transitions by first-principles free-energy calculations including the vibrational free energy and configurational entropy. We considered the in-plane configurations of six structures with different Li concentrations in the Li layer and the interlayer configurations of AA, AB, and mixed stacks for eight stages. The contributions of the vibrational free energy and configurational entropy were estimated to be less than −20 meV/Li x C6 for 0 ≤ x ≤ 1/3. The formation free energy predicts that the AA-Li/9C-s2 structure with x = 1/3 (LiC18) and AB-stack phase with 0 ≤ x ≤ 0.05 (C–LiC120) are stable. The formation free energy also suggests the stable phase of the mixed-stack structures for intermediate Li compositions of 0.05 < x < 1/3 (LiC120–LiC18). The AB-stack–mixed-stack transition at x ≈ 0.05 obtained herein is consistent with recent X-ray diffraction observations. We also discuss the relation between the computational entropy change in Li x C6 and the results of electrochemical measurements, which are in quantitative agreement, especially with the entropy jump at x ≈ 0.05.

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Thermodynamics of Lithium Intercalation in Randomly Oriented High Graphene Carbon

Cited by 4 publications

References 14 publications

Comparative study of density functionals for the description of lithium‐graphite intercalation compounds

Comparative study of density functionals for the description of lithium‐graphite intercalation compounds

Performance of Novel Randomly Oriented High Graphene Carbon in Lithium Ion Capacitors

Thermodynamic Analysis of Li-Intercalated Graphite by First-Principles Calculations with Vibrational and Configurational Contributions

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