Investigation of the Lithiation and Delithiation Conversion Mechanisms of Bismuth Fluoride Nanocomposites

Bervas, M.; Mansour, A. N.; Yoon, Won‐Sub; Al‐Sharab, Jafar F.; Badway, F.; Cosandey, F.; Klein, Lisa C.; Amatucci, Glenn G.

doi:10.1149/1.2167951

Cited by 82 publications

(88 citation statements)

References 19 publications

(31 reference statements)

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“…One of the promising classes of electrode materials that could meet these requirements is lithium conversion compounds, which have the advantage of accommodating more than one lithium per transition metal, boasting high theoretical capacities [2][3][4] , and in some cases, exhibit excellent capacity retention. A recent study of lithium conversion in the FeF 2 cathode offered the first experimental evidence of the formation of a conductive iron network, 5 which may provide the pathway for electron transport necessary for reversible lithium cycling 2,4,6,7 . However, these electrodes are typically plagued by poor cycling rate and a large cycling hysteresis 8,9 .…”

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confidence: 99%

Tracking lithium transport and electrochemical reactions in nanoparticles

et al. 2012

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Expectations for the next generation of lithium batteries include greater energy and power densities along with a substantial increase in both calendar and cycle life. Developing new materials to meet these goals requires a better understanding of how electrodes function by tracking physical and chemical changes of active components in a working electrode. Here we develop a new, simple in-situ electrochemical cell for the transmission electron microscope and use it to track lithium transport and conversion in FeF 2 nanoparticles by nanoscale imaging, diffraction and spectroscopy. In this system, lithium conversion is initiated at the surface, sweeping rapidly across the FeF 2 particles, followed by a gradual phase transformation in the bulk, resulting in 1-3 nm iron crystallites mixed with amorphous LiF. The real-time imaging reveals a surprisingly fast conversion process in individual particles (complete in a few minutes), with a morphological evolution resembling spinodal decomposition. This work provides new insights into the inter-and intra-particle lithium transport and kinetics of lithium conversion reactions, and may help to pave the way to develop highenergy conversion electrodes for lithium-ion batteries.

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Tracking lithium transport and electrochemical reactions in nanoparticles

et al. 2012

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“…Higher capacities can be achieved in a conversion reaction, which does not preserve the initial structure type. 1 So far, the electrochemical conversion reactions have been observed in various compounds such as oxysalts, 2 fluorides, 3 and nitrides. 4 Some of them provide high capacities from hundreds of mAh/g for the cathodes to several thousands of mAh/g for anodes.…”

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Study of the Conversion Reaction Mechanism for Copper Borate as Electrode Material in Lithium-Ion Batteries

Parzych

Mikhailova

Oswald

et al. 2011

J. Electrochem. Soc.

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A conversion reaction mechanism of Cu 3 B 2 O 6 during the electrochemical reduction in a Li-ion battery test cell was revealed. Different experimental techniques were used: X-ray diffraction (XRD), in situ synchrotron diffraction, quasi in situ X-ray photoelectron and Auger-electron spectroscopy (XPS and AES), and ex situ scanning electron microscopy (SEM). The reduction process changes the initial oxidation state of copper from Cu(II) to Cu(0). After the subsequent oxidation, only the Cu(I) state was recovered. However, a very high amount of carbon in the cathode mixture (65% w/w) enables the reversion of the Cu(II) state due to improved electronic conductivity. Synchrotron in situ diffraction did not indicate any significant change in the lattice parameters of Cu 3 B 2 O 6 during any stage of reduction, which excludes a Li-intercalation mechanism. The present rechargeable lithium-ion batteries operate based on intercalation processes. These processes require electrode materials with open crystallographic structures, into which lithium ions can be inserted without reconstructive phase transitions. The change of the metal oxidation state is therefore limited by the available vacant sites for Li-ions in the underlying crystal structures. Higher capacities can be achieved in a conversion reaction, which does not preserve the initial structure type.

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“…In fact, LiF has been noted as being absent by XRD of macro electrode converted materials, yet present by TEM analysis. 16 Similar to FeF 2 , chemical lithiation of thicker cast electrode resulted in LiF and Bi 0 . However it should be noted that Li 3 Bi was also found to be present in the thicker electrodes well.…”

Section: Fef 2 -mentioning

confidence: 99%

Electronic Transport in Lithiated Iron and Bismuth Fluoride

Halajko

Parkinson

et al. 2014

J. Electrochem. Soc.

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Metal networks are formed during the lithiation of metal fluorides. Previous reports indicate that these networks are bi-continuous with the possibility to support electronic transport, though no quantitative analysis has been performed. In this study, thin films of FeF 2 and BiF 3 were chemically lithiated using n-butyllithium to form these metal networks. Direct current (DC) polarization and electrochemical impedance spectroscopy (EIS) were utilized to find electronic conductivity and results were compared to their pure metals. Results indicate films to have higher than expected conductivity value which indicates that these metal networks support electronic transport during lithiation. © The Author(s) 2014. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives 4.0 License (CC BY-NC-ND, http://creativecommons.org/licenses/by-nc-nd/4.0/), which permits non-commercial reuse, distribution, and reproduction in any medium, provided the original work is not changed in any way and is properly cited. For permission for commercial reuse, please email: oa@electrochem.org. [DOI: 10.1149/2.0621501jes] All rights reserved. Lithium-ion batteries are the ubiquitous energy storage device for portable electronics. Historically, there has been a continuous quest for higher energy density chemistries in order to reduce the weight or volume in new innovative devices. Lithium conversion compounds are one of the promising alternatives for battery positive electrodes.1 The advantage is their ability to accommodate more than one lithium/electron per transition metal to achieve higher capacities than traditional intercalation compounds. Transition metal fluoride conversion materials have been a research focus because their highly ionic bonds allow reduction potentials approximately 1 V higher than the chalcogenides.2-5 As such, high capacity, low cost metal fluorides such as FeF 2 , FeF 3 and CuF 2 are of interest. FeF 2 has been extensively investigated as a potential electrode material due to its potential low cost and rutile structure which is common among the first row metal fluorides.6-8 The latter aspect makes it an excellent model material for fundamental studies. FeF 2 exhibits a single three phase reaction, FeF 2 + 2Li + + 2e − → Fe + 2 LiF, exhibiting a theoretical capacity of 571 mAh/g. During lithiation, most conversion materials of fluoride and dichacodenide chemistries form a bi-continuous network of nano metal and lithium salt (i.e. LiF, Li 2 O, etc.). This has been shown in a number of high resolution transmission electron microscopy studies and supported in part by molecular dynamic modeling.9,10 Although such networks visually appear to be electronic percolating (Figure 1) and may be the pathway for electron transport to the reaction front, there has been no data to suggest what order of magnitude the conductivity of this percolated network is. The goal of the effort presented herein is to establish quantitatively the electronic c...

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Investigation of the Lithiation and Delithiation Conversion Mechanisms of Bismuth Fluoride Nanocomposites

Cited by 82 publications

References 19 publications

Tracking lithium transport and electrochemical reactions in nanoparticles

Tracking lithium transport and electrochemical reactions in nanoparticles

Study of the Conversion Reaction Mechanism for Copper Borate as Electrode Material in Lithium-Ion Batteries

Electronic Transport in Lithiated Iron and Bismuth Fluoride

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