Insight into the Atomic Structure of Cycled Lithium-Rich Layered Oxide Li1.20Mn0.54Co0.13Ni0.13O2 Using HAADF STEM and Electron Nanodiffraction

Genevois, Cécile; Koga, Hideyuki; Croguennec, Laurence; Ménétrier, Michel; Delmas, Claude; Weill, François

doi:10.1021/jp509388j

Cited by 126 publications

(128 citation statements)

References 36 publications

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“…25,[27][28][29] However, using a material with a very high lithium content, like the 0.50 Li 2 MnO 3 material in this study, a partial bulk transformation can be observed, amounting to ≈20 mol% of the material being converted into a spinel-like phase (calculated from the oxygen evolution, shown in Model II from Table IV). While the TEM data are statistically not sufficient to provide exact quantitative surface layer thickness values for averaged over the entire material, they fit well to the quantification from the OEMS results.…”

Section: Discussionmentioning

confidence: 72%

“…25 Both observations suggested that the observed oxygen release cannot be ascribed to a loss of oxygen from the bulk of the material, but that the oxygen is only being released from the near-surface Thus, more recent studies propose that bulk and surface of these overlithiated materials show distinctly different properties, rationalized by a bulk-shell model. 25,[27][28][29] It has been suggested that oxygen release takes places in near-surface region, leading to a chemical layered-to-spinel transformation and a concomitant impedance buildup by the formed resistive surface layer. This phenomenon has also been shown to be one of the main fading mechanisms for traditional NCM materials.…”

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confidence: 99%

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Oxygen Release and Surface Degradation of Li- and Mn-Rich Layered Oxides in Variation of the Li₂MnO₃Content

Teufl

Strehle

Müller³

et al. 2018

J. Electrochem. Soc.

157

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In this study, we will show how the oxygen release depends on the Li 2 MnO 3 content of the material and how it affects the actual voltage fading of the material. Thus, we compared overlithiated NCMs (x Li 2 MnO 3 • (1-x) LiMeO 2 ; Me = Ni, Co, Mn) with x = 0.33, 0.42 and 0.50, focusing on oxygen release and electrochemical performance. We could show that the oxygen release differs vastly for the materials, while voltage fading is similar, which leads to the conclusion that the oxygen release is a chemical material degradation, occurring at the surface, while voltage fading is a bulk issue of these materials. We could prove this hypothesis by HRTEM, showing a surface layer, which is dependent on the amount of oxygen released in the first cycles and leads to an increase of the charge-transfer resistance of these materials. Furthermore, we could quantitatively deconvolute capacity contributions from bulk and surface regions by dQ/dV analysis and correlate them to the oxygen loss. As a last step, we compared the gassing to the base NCM (LiMeO 2 , Me = Ni, Co, Mn), showing that surface degradation follows a similar reaction pathway and can be easily To face future issues, as global warming, air pollution, as well as the consumption of fossil fuels, an alternative is required to cover the future demand of energy and mobility in an environmentally friendly and sustainable way. In this context, lithium-ion batteries are viable options for large scale energy storage and for electric vehicles, as they have been used to power consumer electronics for many years. 1,2Since graphite is an excellent anode material at potentials of ≈0.1 V vs. Li + /Li with a roughly 2-fold higher specific capacity of about 360 mAh/g compared to currently used cathode active materials (CAMs), many efforts have been undertaken to increase the specific capacity and energy density of CAMs. As first practical cathode active material Lithium-Cobalt-Oxide (LCO) was investigated by Goodenough et al. in the 1980s, exhibiting a specific capacity of about 140 mAh/g and having a layered structure composed of lithium and transition metal layers.3 As these layered structures showed good structural stability during lithium extraction and insertion, and therefore good capacity retention, many attempts have been undertaken to further develop alternative layered structures which would offer higher capacity. One promising attempt that led to the currently used Lithium-NickelCobalt-Manganese-Oxides (NCMs) is to change the occupancy of the transition metal layer by not using exclusively cobalt, but also introducing nickel and manganese into the transition metal layer; hereby it was found that nickel shows a high redox activity, while manganese helps to stabilize the structure during lithium extraction.4-6 By using different transition metals and metal compositions, a playground has been created that allows to tune the properties of the material: while initially a Ni:Co:Mn ratio of 1:1:1 was used (also referred to as NCM-111), trends nowadays favor the so-called Ni...

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Section: Discussionmentioning

confidence: 72%

mentioning

confidence: 99%

Oxygen Release and Surface Degradation of Li- and Mn-Rich Layered Oxides in Variation of the Li₂MnO₃Content

Teufl

Strehle

Müller³

et al. 2018

J. Electrochem. Soc.

157

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“…Delmas et al, successfully investigate the structural rearrangement of 1 st cycled Li-excess 3dTM material along [100] mono zone axis 36 . In order to analyze the structural characteristic of Li-excess material correctly, Atomic arrangement along [100] mono direction where we can observe Li 2 MnO 3 phase is additionally needed to increase the structural analysis accuracy.…”

Section: Resultsmentioning

confidence: 99%

Understanding voltage decay in lithium-excess layered cathode materials through oxygen-centred structural arrangement

et al. 2018

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Lithium-excess 3d-transition-metal layered oxides (Li1+xNiyCozMn1−x−y−zO2, >250 mAh g−1) suffer from severe voltage decay upon cycling, which decreases energy density and hinders further research and development. Nevertheless, the lack of understanding on chemical and structural uniqueness of the material prevents the interpretation of internal degradation chemistry. Here, we discover a fundamental reason of the voltage decay phenomenon by comparing ordered and cation-disordered materials with a combination of X-ray absorption spectroscopy and transmission electron microscopy studies. The cation arrangement determines the transition metal-oxygen covalency and structural reversibility related to voltage decay. The identification of structural arrangement with de-lithiated oxygen-centred octahedron and interactions between octahedrons affecting the oxygen stability and transition metal mobility of layered oxide provides the insight into the degradation chemistry of cathode materials and a way to develop high-energy density electrodes.

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“…From the amount of evolved gases, we estimated the thickness of such a spinel-like surface layer on the HE-NCM particles to be on the order of ≈2-3 nm, in excellent agreement with previously observed (S)TEM data. [28][29][30] …”

Section: Discussionmentioning

confidence: 99%

“…Nevertheless, the estimated thickness of ≈2-3 nm for the spinel-like phase is in excellent agreement with recent (S)TEM results, which propose also a 2-3 nm thick surface layer formed during the first cycle. [28][29][30] As already mentioned in the discussion of Figure 2, it is not possible to determine whether the transformation of the near-surface region stops at the spinel structure (as described in Eq. 2) and to what extent it may proceed all the way to the rock-salt structure (as described in Eq.…”

Section: Ammentioning

confidence: 99%

The Role of Oxygen Release from Li- and Mn-Rich Layered Oxides during the First Cycles Investigated by On-Line Electrochemical Mass Spectrometry

Strehle

Kleiner

Jung

et al. 2017

J. Electrochem. Soc.

198

279

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In the present work, the extent and the role of oxygen release during the first charge of lithium-and manganese-rich Li 1.17 [Ni 0.22 Co 0.12 Mn 0.66 ] 0.83 O 2 (also referred to as HE-NCM) was investigated with on-line electrochemical mass spectrometry (OEMS). HE-NCM shows a unique voltage plateau at around 4.5 V in the first charge, which is often attributed to a decomposition reaction of the Li-rich component Li 2 MnO 3 . For this so-called "activation", it has been hypothesized that the electrochemically inactive Li 2 MnO 3 would convert into MnO 2 while lattice oxide ions are oxidized and released as O 2 (or even CO 2 ) from the host structure. However, qualitative and quantitative examination of the O 2 and CO 2 evolution during the first charge shows that the onset of both reactions is above the 4.5 V voltage plateau and that the amount of released oxygen is an order of magnitude too low to be consistent with the commonly assumed Li 2 MnO 3 activation. Instead, the amount of released oxygen can be correlated to a structural rearrangement of the active material which occurs at the end of the first charge. In this process, oxygen depletion from the HE-NCM host structure leads to the formation of a spinel-like phase. This phase transformation is restricted to the near-surface region of the HE-NCM particles due to the poor mobility of oxide ions within the bulk. From the evolved amount of O 2 and CO 2 , the thickness of the spinel-like surface layer was estimated to be on the order of ≈2-3 nm, in excellent agreement with previously reported (S)TEM data. Since the discovery of the positive electrode material LiCoO 2 and its commercialization in the Li-ion technology by Sony in 1991, 1 analogous layered oxides (LiMeO 2 , Me = Ni, Co, Mn, Al, etc.) were studied, aiming at higher intrinsic specific capacity, energy, stability, and lower costs.2-7 Among others, Li[Ni 1/3 Co 1/3 Mn 1/3 ]O 2 (NCM-111) showed very interesting performances in terms of specific capacity and stability. 8,9 Recently, materials characterized by an increase of exploitable Li + charge drew a lot of attention. 10,11 These so-called Lirich compounds result from the substitution of part of the transition metal ions by Li + , in a structural arrangement closely related to the layered structure. 11-14Li 2 MnO 3 (or Li[Li 1/3 Mn 2/3 ]O 2 ) is the simplest structure in this category and crystallizes in the monoclinic system (space group C2/m), while the common LiMeO 2 -based layered structures crystallize in the hexagonal system (space group R-3m). 11,13,14 The two structures are very close to each other despite this difference in symmetry, related simply to the Li + ordering in the transition metal sites. This similarity is evident in the structure of the Li-rich NCM Li 1+x Me 1-x O 2 (Me = Ni, Co, Mn), also referred to as high-energy NCM (HE-NCM), where the hexagonal symmetry of the layered structure is broken by the superstructure of Li + in the transition metal sites, shown by the superlattice reflections in the diffractograms. 15,16 This s...

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Insight into the Atomic Structure of Cycled Lithium-Rich Layered Oxide Li_1.20Mn_0.54Co_0.13Ni_0.13O₂ Using HAADF STEM and Electron Nanodiffraction

Abstract: Insight in the Atomic Structure of Cycled Lithium-rich Layered Oxide Li1.20Mn0.54Co0.13Ni0.13O2 using HAADF STEM and Electron Nano Diffraction

Cited by 126 publications

References 36 publications

Oxygen Release and Surface Degradation of Li- and Mn-Rich Layered Oxides in Variation of the Li₂MnO₃Content

Oxygen Release and Surface Degradation of Li- and Mn-Rich Layered Oxides in Variation of the Li₂MnO₃Content

Understanding voltage decay in lithium-excess layered cathode materials through oxygen-centred structural arrangement

The Role of Oxygen Release from Li- and Mn-Rich Layered Oxides during the First Cycles Investigated by On-Line Electrochemical Mass Spectrometry

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Insight into the Atomic Structure of Cycled Lithium-Rich Layered Oxide Li1.20Mn0.54Co0.13Ni0.13O2 Using HAADF STEM and Electron Nanodiffraction

Abstract: Insight in the Atomic Structure of Cycled Lithium-rich Layered Oxide Li1.20Mn0.54Co0.13Ni0.13O2 using HAADF STEM and Electron Nano Diffraction

Cited by 126 publications

References 36 publications

Oxygen Release and Surface Degradation of Li- and Mn-Rich Layered Oxides in Variation of the Li2MnO3Content

Oxygen Release and Surface Degradation of Li- and Mn-Rich Layered Oxides in Variation of the Li2MnO3Content

Understanding voltage decay in lithium-excess layered cathode materials through oxygen-centred structural arrangement

The Role of Oxygen Release from Li- and Mn-Rich Layered Oxides during the First Cycles Investigated by On-Line Electrochemical Mass Spectrometry

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Insight into the Atomic Structure of Cycled Lithium-Rich Layered Oxide Li_1.20Mn_0.54Co_0.13Ni_0.13O₂ Using HAADF STEM and Electron Nanodiffraction

Oxygen Release and Surface Degradation of Li- and Mn-Rich Layered Oxides in Variation of the Li₂MnO₃Content

Oxygen Release and Surface Degradation of Li- and Mn-Rich Layered Oxides in Variation of the Li₂MnO₃Content