Separating electronic and ionic conductivity in mix-conducting layered lithium transition-metal oxides

Wang, Shanyu; Yan, Mengyu; Li, Yun; Vinado, Carolina; Yang, Jihui

doi:10.1016/j.jpowsour.2018.05.005

Cited by 125 publications

(118 citation statements)

References 35 publications

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“…Indeed, the measured activation energies agree well with the range of values, 0.99-1.69 eV, calculated from the formation energies and migration barrier of η + reported in [36]. The E a = 0.4 eV value reported for some LiCoO 2 samples [131,134] is In many experimental reports, the activation energy may be incorrectly derived from the slope of a ln(σ) vs. 1/T plot, instead of a ln(σT ) vs. 1/T plot as it should be for thermally activated electronic and ionic conduction [Note the pre-factor m 0 ∝ 1/T in equation (11) for the mobility]. In that case, the actual activation energy may be larger than the reported value, usually by about a few percent.…”

Section: Interpretation Of Conductivity Datasupporting

confidence: 85%

“…The valence-band top of these materials is predominantly composed of the Ni 3d states; as a result, Ni 2+ and Ni 3+ are oxidized before any other transition-metal ions (e.g., Co 3+ ) and small polarons associated with the Ni ions dominate the electronic transport in lithiated and partially delithiated compounds; see, e.g., the electronic structure and voltage profiles of NCM 1/3 and NCA 1/3 reported in [44]. Experimentally, Saadoune and Delmas [136] [134]. All these values are in good agreement with the calculated migration barrier (0.21-0.31 eV) of small polarons associated with the Ni ions in LiNiO 2 , NCM 1/3 , and NCA 1/3 ; see Table 1.…”

Section: Interpretation Of Conductivity Datamentioning

confidence: 99%

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Defect physics in complex energy materials

Hoang

Johannes

2018

J. Phys.: Condens. Matter

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Understanding the physics of structurally and chemically complex transition-metal oxide and polyanionic materials such as those used for battery electrodes is challenging, even at the level of pristine compounds. Yet these materials are also prone to and their properties and performance are strongly affected or even determined by crystallographic point defects. In this review, we highlight recent advances in the study of defects and doping in such materials using first-principles calculations. The emphasis is on describing a theoretical and computational approach that has the ability to predict defect landscapes under various synthesis conditions, provide guidelines for defect characterization and defect-controlled synthesis, uncover the mechanisms for electronic and ionic conduction and electrochemical extraction and (re-)insertion, and provide an understanding of the effects of doping. Though applied to battery materials here, the approach is general and applicable to any materials in which the defect physics plays a role or drives the properties of interest. Thus, this work is intended as an in-depth review of defect physics in particular classes of materials, but also as a methodological template for the understanding and design of complex functional materials.

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Section: Interpretation Of Conductivity Datasupporting

confidence: 85%

Section: Interpretation Of Conductivity Datamentioning

confidence: 99%

Defect physics in complex energy materials

Hoang

Johannes

2018

J. Phys.: Condens. Matter

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“…Furthermore, studies have also confirmed two pathways ( Fig. 1c2, c3) involved in the delithiation of Nirich NMC-based cathodes [40,48], including oxygen dumbbell hopping and tetrahedral site hopping, in which at the beginning of charging, Li can exit through oxygen dumbbell hopping until a certain degree of delithiation is reached and continue through tetrahedral site hopping due to increased energy barriers as caused by Li-O bonds during delithiation.…”

Section: Surface Degradation During Cell Operationmentioning

confidence: 78%

“…For example, enhanced mass-specific capacity can be achieved but at the expense of rate capability and structural stability. In addition, researchers have also reported higher electronic conductivity and reduced polarization [40] in which the varied polarization as compared with the portion of Ni is caused by the higher e g orbital of Ni over the t 2g orbital of Co [41]. Researchers have also shown that the reduced Mn content can result in faster degradation through surface reconstruction [42] and that the increased Ni content can result in increased cation mixing due to the bulk diffusion of Ni 2+ into the Li-layer and increased parasitic reactions as the valence of surface Ni increases toward highly reactive Ni 4+ .…”

Section: Ni-rich Nmc-based Cathodesmentioning

confidence: 99%

Degradation Mechanisms and Mitigation Strategies of Nickel-Rich NMC-Based Lithium-Ion Batteries

Yuan

Zhang

et al. 2019

Electrochem. Energ. Rev.

525

383

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The demand for lithium-ion batteries (LIBs) with high mass-specific capacities, high rate capabilities and long-term cyclabilities is driving the research and development of LIBs with nickel-rich NMC (LiNi x Mn y Co 1−x−y O 2 , x ⩾ 0.5 ) cathodes and graphite (Li x C 6 ) anodes. Based on this, this review will summarize recently reported and widely recognized studies of the degradation mechanisms of Ni-rich NMC cathodes and graphite anodes. And with a broad collection of proposed mechanisms on both atomic and micrometer scales, this review can supplement previous degradation studies of Ni-rich NMC batteries. In addition, this review will categorize advanced mitigation strategies for both electrodes based on different modifications in which Ni-rich NMC cathode improvement strategies involve dopants, gradient layers, surface coatings, carbon matrixes and advanced synthesis methods, whereas graphite anode improvement strategies involve surface coatings, charge/discharge protocols and electrolyte volume estimations. Electrolyte components that can facilitate the stabilization of anodic solid electrolyte interfaces are also reviewed, and trade-offs between modification techniques as well as controversies are discussed for a deeper understanding of the mitigation strategies of Ni-rich NMC/graphite LIBs. Furthermore, this review will present various physical and electrochemical diagnostic tools that are vital in the elucidation of degradation mechanisms during operation to supplement future degradation studies. Finally, this review will summarize current research focuses and propose future research directions.

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“…The XRD pattern shown in the Supporting Information (Figure S4) revealed no changes, and therefore Au was used as the blocking electrode. The electronic conductivity ( σ e ) was calculated from the electronic resistance ( R e ), which was measured in CA experiments (Figure b, c) by applying different potentials for 30 min . The ionic conductivity ( σ i ) was determined from the ionic resistance ( R i ) measured by EIS.…”

Section: Resultsmentioning

confidence: 99%