NMR evidence of LiF coating rather than fluorine substitution in Li(Ni0.425Mn0.425Co0.15)O2

Ménétrier, Michel; Bains, J.; Croguennec, Laurence; Flambard, Alexandrine; Bekaert, Émilie; Jordy, Christian; Biensan, P.; Delmas, Claude

doi:10.1016/j.jssc.2008.09.002

Cited by 54 publications

(91 citation statements)

References 28 publications

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“…This is in contrast to previous studies on the fluorination of layered or disordered rocksalt-type cathodes, which either failed to incorporate fluorine in the bulk lattice of layered materials via solid-state synthesis 20, 21 , or employed mechanochemical ball milling to synthesize fluorinated disordered rocksalt phases 11 . X-ray diffraction (XRD) (Fig.…”

Section: Resultscontrasting

confidence: 73%

“…EDS mapping reveals a uniform distribution of fluorine in the LNF15 particle, along with other elements. 19 F solid-state nuclear magnetic resonance spectroscopy (ssNMR) experiments were subsequently performed to prove that the fluorine distribution observed with TEM-EDS is not due to LiF on the surface of the particles, as often found in layered oxides 20, 21 . NMR spectra were collected on both LNF15 and LiF powders (Fig.…”

Section: Resultsmentioning

confidence: 99%

“…Fluorine incorporation into the disordered Li–Ni–Ti–Mo–O rocksalt by conventional solid-state synthesis is maybe somewhat surprising as most attempts to prepare fluorinated layered-rocksalt oxides by solid-state synthesis resulted in the formation of LiF at the surface of the particles 20, 21 . The different behavior towards fluorine incorporation between the LEX-RS materials and well-ordered layered compounds may be related to the large variety of local environments that occur in cation-disordered materials as compared to the single local oxygen environment in a layered oxide.…”

Section: Discussionmentioning

confidence: 99%

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Mitigating oxygen loss to improve the cycling performance of high capacity cation-disordered cathode materials

et al. 2017

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Recent progress in the understanding of percolation theory points to cation-disordered lithium-excess transition metal oxides as high-capacity lithium-ion cathode materials. Nevertheless, the oxygen redox processes required for these materials to deliver high capacity can trigger oxygen loss, which leads to the formation of resistive surface layers on the cathode particles. We demonstrate here that, somewhat surprisingly, fluorine can be incorporated into the bulk of disordered lithium nickel titanium molybdenum oxides using a standard solid-state method to increase the nickel content, and that this compositional modification is very effective in reducing oxygen loss, improving energy density, average voltage, and rate performance. We argue that the valence reduction on the anion site, offered by fluorine incorporation, opens up significant opportunities for the design of high-capacity cation-disordered cathode materials.

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Section: Resultscontrasting

confidence: 73%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Mitigating oxygen loss to improve the cycling performance of high capacity cation-disordered cathode materials

et al. 2017

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“…However, previous studies have demonstrated that, at least in stoichiometric layered oxide cathodes, LiF may form electrochemically inactive coatings. 51,52 We rely on 19 F solid-state nuclear magnetic resonance spectroscopy (ssNMR) to confirm that, in our case, the fluorine is not segregated. The 19 F NMR spectra collected for ST-LMVF20, MR-LMVF20 and LR-LMVF20, shown in Fig.…”

Section: Electrochemical Design and Performancementioning

confidence: 60%

Design principles for high transition metal capacity in disordered rocksalt Li-ion cathodes

Kitchaev¹,

Lun

Richards³

et al. 2018

Energy Environ. Sci.

139

189

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The discovery of facile Li transport in disordered, Li-excess rocksalt materials has opened a vast new chemical space for the development of high energy density, low cost Li-ion cathodes. We develop a strategy for obtaining optimized compositions within this class of materials, exhibiting high capacity and energy density as well as good reversibility, by using a combination of low-valence transition metal redox and a high-valence redox active charge compensator, as well as fluorine substitution for oxygen.Furthermore, we identify a new constraint on high-performance compositions by demonstrating the necessity of excess Li capacity as a means of counteracting high-voltage tetrahedral Li formation, Li-binding by fluorine and the associated irreversibility. Specifically, we demonstrate that 10-12% of Li capacity is lost due to tetrahedral Li formation, and 0.4-0.8 Li per F dopant is made inaccessible at moderate voltages due to Li-F binding. We demonstrate the success of this strategy by realizing a series of high-performance disordered oxyfluoride cathode materials based on Mn 2+/4+ and V 4+/5+ redox. Broader contextElectrochemical energy storage is a key component of modern energy systems, providing portable power to devices ranging from personal electronics to electric vehicles, and enabling grid-scale mitigation of the fluctuating availability of renewable energy sources. The central role of energy storage systems motivates the search for, and optimization of, low-cost, environmentally-benign materials which can reversibly provide high energy density. Cathode materials, which are presently the performance-limiting components in state-of-the-art Li-ion batteries, have been traditionally limited to Ni and Co-based layered oxides. The recent discovery of Li-percolation in disordered rocksalts has expanded the structural space of materials which may serve as a Li-ion electrode, while the demonstration of Mn 2+/4+ cathode electrochemistry and disordered rocksalt fluorination has opened to door to the use of cheap, environmentally-friendly chemistries. Here, we build on these demonstrations to derive optimization rules for designing disordered rocksalt oxyfluoride cathodes and provide an example of an optimized series of cathode materials.

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“…The sharp 7 Li NMR (~0 ppm) and 19 F (-204.8 ppm) signals arises from residual diamagnetic LiF precursor (not found from diffraction data). [26] Two broad 19 F resonance lines were observed, indicating that F exists in two distinct environments arising from (i) non-uniform distribution of F at surface and in the bulk as evidenced from X-ray photoelectron spectroscopy (XPS) and EDS analysis (Table S2), and…”

mentioning

confidence: 99%

Disordered Lithium‐Rich Oxyfluoride as a Stable Host for Enhanced Li⁺ Intercalation Storage

Chen

Ren

Knapp

et al. 2015

Advanced Energy Materials

191

294

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Keywords: Li-ion batteries, intercalation cathodes, disordered rock salt, Li 2 VO 2 F Advanced cathode materials with superior energy storage capability are highly demanded for mobile and stationary applications. The inherent structural feature of Li + hosts is critical for the battery performance. High-capacity conversion cathode materials often encounter large voltage hysteresis (low energy efficiency) accompanied with the structural reconstruction.[1]The current commercial cathode materials are still dominated by intercalation materials with intrinsic structural integrity for accommodating Li + .[2] However, the known intercalation materials have limited theoretical capacity (< 300 mAh g -1 ). [3] In addition, structural transition/degradation have often been observed for the common intercalation hosts with ordered Li + / transition metal (TM) lattice sites. Antisite disorder (Li + sites/layers occupied by TM ions) in olivines can block the one-dimensional Li + diffusion path.[4] The activation barrier for Li + diffusion in layered oxides is sensitive to the Li-content, the spacing of the

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NMR evidence of LiF coating rather than fluorine substitution in Li(Ni0.425Mn0.425Co0.15)O2

Cited by 54 publications

References 28 publications

Mitigating oxygen loss to improve the cycling performance of high capacity cation-disordered cathode materials

Mitigating oxygen loss to improve the cycling performance of high capacity cation-disordered cathode materials

Design principles for high transition metal capacity in disordered rocksalt Li-ion cathodes

Disordered Lithium‐Rich Oxyfluoride as a Stable Host for Enhanced Li⁺ Intercalation Storage

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NMR evidence of LiF coating rather than fluorine substitution in Li(Ni0.425Mn0.425Co0.15)O2

Cited by 54 publications

References 28 publications

Mitigating oxygen loss to improve the cycling performance of high capacity cation-disordered cathode materials

Mitigating oxygen loss to improve the cycling performance of high capacity cation-disordered cathode materials

Design principles for high transition metal capacity in disordered rocksalt Li-ion cathodes

Disordered Lithium‐Rich Oxyfluoride as a Stable Host for Enhanced Li+ Intercalation Storage

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Disordered Lithium‐Rich Oxyfluoride as a Stable Host for Enhanced Li⁺ Intercalation Storage