First-Principles Study of Lithium and Sodium Atoms Intercalation in Fluorinated Graphite

Rao, Fengya; Wang, Zhiqiang; Xu, Bo; Chen, Liquan; Ouyang, Chuying

doi:10.15302/j-eng-2015039

Cited by 19 publications

(27 citation statements)

References 9 publications

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“…Research focuses on the performance of uorinated graphene materials in lithium batteries. 45,46 Rao et al 47 have studied adsorption energy of Li atom on CF x surface by rst-principles calculations.…”

Section: Introductionmentioning

confidence: 99%

First-principles study of the adsorption behaviors of Li atoms and LiF on the CF_x (x = 1.0, 0.9, 0.8, 0.5, ∼0.0) surface

Fan

Yang

et al. 2020

RSC Adv.

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Section: Introductionmentioning

confidence: 99%

First-principles study of the adsorption behaviors of Li atoms and LiF on the CF_x (x = 1.0, 0.9, 0.8, 0.5, ∼0.0) surface

Fan

Yang

et al. 2020

RSC Adv.

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“…Remarkably, the peak position shift left due to the transformation from chair con guration to a at graphite-like structure during Li intercalation, which is in accordance with in-situ experiments and as reported in previous studies. 13,35 As mentioned above, the electrochemical solid-state reaction of CF x with alkali metal ions is expected to behave according to the following equation: This reaction formula is similar to that of liquid-state batteries, the only difference being that crystalline LiF is produced in the liquid-state mode. Upon K/Na/Li ion insertion, the resulting carbon monolayer maintains its amorphous features.…”

Section: Resultsmentioning

confidence: 97%

“…40,41 Herein, one Li/Na/K atom was initially adsorbed in the hollow site of the 3 × 3 × 1 CF supercell (including 36 C and 36 F atoms), based on previous work. 35 Next, the Li/Na/K atom diffused to the adjacent hollow site with the…”

Section: Methodsmentioning

confidence: 99%

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Reaction mechanism and structural evolution of fluorographite cathodes in Li/Na/K batteries

Ding

Yang

Jiang

et al. 2020

Preprint

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Fluorographites (CFx) are potential cathode materials for alkaline metal primary batteries with ultrahigh energy densities. To elucidate the reaction mechanism and structural evolution of CFx cathodes, we combine in situ transmission electron microscopy and ab initio calculations and discover a two-phase mechanism upon Li/Na/K ion insertion. Amorphous LiF (crystalline NaF and KF nanoparticles) are generated uniformly within the amorphous carbon matrix, which retains an unchanged volume during the discharge process. The diffusivity for K/Na/Li ion migration within the CFx is approximately 232.9 nm2/s, 479.7 nm2/s, and 2133.0 nm2/s, respectively, which is comparable to the diffusivity of Li/Na/K ions in liquid-state cells. During charging, amorphous LiF and crystal NaF decompose into alkali metal and F2. Our results reveal no substantial volume change and good ion diffusion kinetics, demonstrating the applicability of all-solid-state M/CFx (M = Li/Na/K) primary batteries. This new understanding may promote the design and development of better CFx-based batteries.While lithium ion batteries (LIBs) are widely applied in portable electronics and electric vehicles, cheaper, more advanced battery systems with higher energy and power densities, and improved safety performance remain in demand.1-5 Among the materials employed in cathode systems, conversion-type materials, such as halides, chalcogenides, and oxides, demonstrate high specific capacities, offering lithium-metal batteries with high energy densities.4,6,7 For example, fluorinated graphite (CFx, x = 1) cathodes exhibit a high theoretical energy density and power density of 3725 Wh kg-1 and 9313 Wh L-1, respectively 6, which can be used in Li primary cells. 8 The practical energy density in Li/CF1.0 cells reaches 2600 Wh kg-1, which is much higher than that in Li/I2, Li/SOCl2, Li/MnO2, Li/Ag2CrO4, and Li/CuS systems.9,10 CFx also delivers a discharge specific capacity of 1061 mAh/g (1439 Wh kg-1) with a discharge plateau of 2.4 V11,12 in a Na/CFx system, and 749 mAh g-1 (1869 Wh kg-1) with a discharge voltage plateau of 3.0 V in a K/CFx system13, which makes CFx applicable for multiple alkali ion batteries. Moreover, the irreversible conversion of CFx into LiF and carbon during discharge, due to the high dissociation energy of LiF (6.1 eV), means the decomposition of LiF by charging alone is not possible.9,10,12 Yazami et al. first demonstrated the reversible electrochemical reaction of CFx with lithium in F ion batteries with a reversible capacity of ~120 mAh g-1.14 Later, Liu et al. reported a reversible Na/CFx battery with a specific capacity of 786 mAh g-1.11 However, these batteries suffer from poor rate performance at low temperatures15, initial voltage delay during the discharge process8 and large heat generation at high discharge rates, which limit their application in harsh environments.9,16 Therefore, a detailed study of the reaction mechanisms is urgently required for the further optimization. Various studies have been conducted to understand these battery systems using different techniques.8,16-20 For example, in situ XRD results suggested a simultaneous formation of a CF(x-y)-Li+ intermediate phase and crystal LiF15,18, while other studies reported a formation of amorphous LiF followed by recrystallization to crystalline LiF.17,19 The crystalline LiF is generated in an orientation that relates to the absorption energy of the solvents on the LiF surface.16 The reversibility and reaction mechanism of CFx in Na/CFx batteries was studied using softX-ray absorption spectroscopy (SXAS) and nuclear magnetic resonance (NMR) techniques, which revealed reversible conversions between CFx and NaF.12 The liquid electrolyte was reported to act as an ion conductor and solution medium to dissolve and aggregate alkali fluoride crystals in a M–CFx (M = Li, Na, and K) system, resulting in large crystalline alkali fluorides.13 Despite intensive efforts focusing on the reaction mechanism, the structural evolution and reaction pathway of CFx in Li/Na/K batteries remains unclear. In this study, we use in situ transmission electron microscopy (TEM) with high spatial/temporal resolution to probe the phase transformation, intermediate phase, and volume change in real time (Figure 1a).21,22 We find that a two-phase reaction occurs during alkali ion intercalation, and the diffusivity of K/Na/Li ion intercalation in CFx is approximately 232.9 nm2/s, 479.7 nm2/s, and 2133.0 nm2/s, respectively. In situ electron diffraction patterns show the formation and even distribution of crystalline KF and NaF nanoparticles and amorphous LiF in the amorphous carbon matrix, leading to no volume change. Upon the insertion of K with a large ionic radius, the interlayer spacing of CF increases, and while only subtle changes are observed during Na/Li ion insertion, both are confirmed through density functional theory (DFT) calculations. Moreover, we find both amorphous LiF and crystalline NaF decompose into alkali metal and F2 during the charging process under vacuum. The results show no volume change and good ion diffusion kinetics during ion intercalation, suggesting that the all-solid-state M/CFx (M = Li/Na/K) primary batteries have broad applicability.

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“…The reversible capacity has been reported to be as high as approximately 300 mAh g −1 , and the mechanisms of metal insertion for both sodium and lithium are quite similar: a sloping potential profile corresponding to insertion of the metal between the graphite layers and low‐potential plateaus close to 0 V that can be attributed to the insertion of the metal into the nanopores. Later on, various in situ and ex situ measurements and theoretical calculations, such as in situ small‐angle X‐ray diffraction, Raman spectroscopy, nuclear magnetic resonance (NMR) spectroscopy, and density functional theory (DFT) calculations, have been employed to understand the sodium storage mechanisms. Although there is some dispute among the results, we can conclude that Na adsorption on the defect sites of the graphene sheets mainly results in a sloping potential profile above 0.1 V, and the low‐potential plateaus close to 0 V are due to insertion into the graphite layers and nanopores.…”

Section: Introductionmentioning

confidence: 99%

Carbon and Carbon Hybrid Materials as Anodes for Sodium‐Ion Batteries

Zhong

Zeng

et al. 2018

Chemistry An Asian Journal

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Sodium-ion batteries (SIBs) have attracted much attention for application in large-scale grid energy storage owing to the abundance and low cost of sodium sources. However, low energy density and poor cycling life hinder practical application of SIBs. Recently, substantial efforts have been made to develop electrode materials to push forward large-scale practical applications. Carbon materials can be directly used as anode materials, and they show excellent sodium storage performance. Additionally, designing and constructing carbon hybrid materials is an effective strategy to obtain high-performance anodes for SIBs. In this review, we summarize recent research progress on carbon and carbon hybrid materials as anodes for SIBs. Nanostructural design to enhance the sodium storage performance of anode materials is discussed, and we offer some insight into the potential directions of and future high-performance anode materials for SIBs.

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First-Principles Study of Lithium and Sodium Atoms Intercalation in Fluorinated Graphite

Cited by 19 publications

References 9 publications

First-principles study of the adsorption behaviors of Li atoms and LiF on the CF_x (x = 1.0, 0.9, 0.8, 0.5, ∼0.0) surface

First-principles study of the adsorption behaviors of Li atoms and LiF on the CF_x (x = 1.0, 0.9, 0.8, 0.5, ∼0.0) surface

Reaction mechanism and structural evolution of fluorographite cathodes in Li/Na/K batteries

Carbon and Carbon Hybrid Materials as Anodes for Sodium‐Ion Batteries

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First-Principles Study of Lithium and Sodium Atoms Intercalation in Fluorinated Graphite

Cited by 19 publications

References 9 publications

First-principles study of the adsorption behaviors of Li atoms and LiF on the CFx (x = 1.0, 0.9, 0.8, 0.5, ∼0.0) surface

First-principles study of the adsorption behaviors of Li atoms and LiF on the CFx (x = 1.0, 0.9, 0.8, 0.5, ∼0.0) surface

Reaction mechanism and structural evolution of fluorographite cathodes in Li/Na/K batteries

Carbon and Carbon Hybrid Materials as Anodes for Sodium‐Ion Batteries

Contact Info

Product

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First-principles study of the adsorption behaviors of Li atoms and LiF on the CF_x (x = 1.0, 0.9, 0.8, 0.5, ∼0.0) surface

First-principles study of the adsorption behaviors of Li atoms and LiF on the CF_x (x = 1.0, 0.9, 0.8, 0.5, ∼0.0) surface