Enhanced electrochemical activity of rechargeable carbon fluorides–sodium battery with catalysts

Li, Wen; Shadike, Zulipiya; Liu, Zhichao; Liu, Wenyuan; Xie, Jun; Fu, Zheng‐Wen

doi:10.1016/j.carbon.2015.05.092

Cited by 19 publications

(32 citation statements)

References 16 publications

(29 reference statements)

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“…The small discharge products would facilitate the decomposition during charge process. After charge process, the vast majority of NaF decomposed, as shown in Figure S5, which exhibits much intact and smooth . Further evidence will be provided by XPS below.…”

Section: Resultsmentioning

confidence: 87%

“…Figure (b–d) shows F 1 s spectral lines for CGP electrodes in pristine, the first discharge and charge state, respectively. After the first discharge process, the peak at 688.8 eV (C−F bond in CF x ) disappeared with the appearance of 685.3 eV (Na−F bond in NaF) in F 1 s spectrum, evidencing the formation of discharge products NaF . However, it is apparent that another peak at 684.3 eV emerged in the F 1 s spectrum after the first discharge process.…”

Section: Resultsmentioning

confidence: 94%

“…As shown in Figure (b), the CGP electrode still retains a reversible capacity of about 322.00 mAh g −1 after 27 cycles, with capacity retention of 63.5%. Na/CGF cells exhibit a better cycle life comparing to the state‐of‐the‐art Na/ CF x cells, Na/commercial CF x cell for example (Figure S3). It is apparent that GO and PAN in the “sandwich” configuration can enhance the adherence of active fluorine to the electrode, and hence reduce the loss of active material during the cycles and improve the cyclic life.…”

Section: Resultsmentioning

confidence: 99%

“…In our previous work, graphene sheets (GNS) were employed in a CF x /GNS/FeF 3 (where CF x =carbon fluoride) composite for sodium secondary batteries, which improved the electronic conductivity of the electrode, provided more active sites and reduced the dissolution of fluorine into the electrolyte, leading to a lower voltage polarization and better cyclic performance . In this work, GO, rich of negative charges and defects, together with polyacrylonitrile (PAN) were introduced into a novel CF x electrode for sodium batteries by a facile route.…”

Section: Introductionmentioning

confidence: 99%

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Sandwich–like Structure of Carbon Fluoride/Graphene Oxide/Polyacrylonitrile Cathode for Lithium and Sodium Batteries

Li¹,

Zhan²,

Shi³

et al. 2017

ChemElectroChem

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Carbon fluoride/graphene oxide/polyacrylonitrile (CFx/GO/PAN, denoted as CGP) electrodes are prepared for lithium primary and sodium secondary batteries. The introduction of GO sheets and PAN built a sandwich‐like structure. The rate performances of Li/CGP batteries verify that PAN and GO materials have negligible effects on the electrochemical properties of lithium primary batteries. In Na/CGP batteries, GO sheets have more defects to facilitate sodium ions transfer and offer more active sites for NaF deposition and decomposition. Meanwhile, the GO network coating of the CFx particles confines active fluorine during the cycles. Cubic and nanoscale discharge products of NaF form both on the surface of CFx particles and the GO sheets, respectively. Na/CGF batteries achieve an initial discharge capacity of 507.0 mAh g−1 and a voltage polarization of 0.75 V, except in the first cycle. These results demonstrate that CGP electrodes with a sandwich‐like structure have favorable electrochemical properties, resulting in the synergetic effect of GO sheets and PAN.

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Section: Resultsmentioning

confidence: 87%

Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Sandwich–like Structure of Carbon Fluoride/Graphene Oxide/Polyacrylonitrile Cathode for Lithium and Sodium Batteries

Li¹,

Zhan²,

Shi³

et al. 2017

ChemElectroChem

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“…Observing the TEM and HAADF-STEM images, we conclude that the volume of CF x remains unchanged after sodiation (Figure 2e), and the SAED pattern ( Figure 3e) shows a two-phase reaction representing the transformation of CF x to NaF and C, which is in agreement with previous studies. 29,30 After Na intercalation, 6-7 nm NaF nanoparticles are evenly distributed in the amorphous carbon matrix (Figure 3f). A two-phase boundary is observed in the elemental mapping of C, F, and Na ( Figure S6m-o), and the Na ion diffusivity is ~479.7 nm 2 /s, as calculated using the projected reaction area (Movie S2, Figure 2e).…”

Section: Resultsmentioning

confidence: 99%

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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Conversion‐Based Cathode Materials for Rechargeable Sodium Batteries

Kim

Kang

2018

Advanced Energy Materials

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Conversion‐based electrode materials for rechargeable sodium batteries (RSBs) have received considerable attention because of their potentially higher energy densities than those of conventional intercalation‐based electrode materials. This would overcome generally lower energy densities of RSBs than those of lithium‐ion batteries. However, they often suffer from large volume changes, sluggish Na‐ion kinetics, and large overpotential in their reaction. Intensive research has thus focused on improving the electrochemical performance through a number of approaches, including analyses of the reaction mechanisms during charge/discharge, engineering the electrode materials in terms of their nanostructuring or compositing, and searching for new candidate materials. This review presents an overview of the approaches used to explore conversion electrode materials for RSBs, in particular focusing on those with relative high redox potential that could be possibly used as cathodes, followed by a discussion of the challenges and perspectives involving future research directions for these materials.

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Enhanced electrochemical activity of rechargeable carbon fluorides–sodium battery with catalysts

Cited by 19 publications

References 16 publications

Sandwich–like Structure of Carbon Fluoride/Graphene Oxide/Polyacrylonitrile Cathode for Lithium and Sodium Batteries

Sandwich–like Structure of Carbon Fluoride/Graphene Oxide/Polyacrylonitrile Cathode for Lithium and Sodium Batteries

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

Conversion‐Based Cathode Materials for Rechargeable Sodium Batteries

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