Structural Changes in Li<sub>2</sub>MnO<sub>3</sub> Cathode Material for Li‐Ion Batteries

Rana, Jatinkumar; Stan, Marian Cristian; Kloepsch, Richard; Li, Jie; Schumacher, G.; Welter, Edmund; Zizak, Ivo; Banhart, John; Winter, Martin

doi:10.1002/aenm.201300998

Cited by 204 publications

(213 citation statements)

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“…[ 12 ] We note that in the Li x Mn 4/3 O 4 environments, Mn remains fully coordinated by O, in agreement with the work in ref. [ 7 ] ; however, O is under-coordinated, surrounded on average by 2, instead of 3 Mn.…”

Section: Discussionsupporting

confidence: 84%

“…[ 34 ] These structural transformations are sometimes attributed to the insertion of protons, arising from electrolyte decomposition, into cycled Li 2 MnO 3 . [ 11,12,15 ] However, a recent study combining solid state nuclear magnetic resonance and X-ray absorption spectroscopies with fi rst principles calculations has indicated that proton insertion is not a signifi cant contributor. [ 16 ] An alternative mechanism invokes the loss of oxygen from the oxide as the dominant process governing structural transformations.…”

Section: Discussionmentioning

confidence: 97%

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On the Localized Nature of the Structural Transformations of Li₂MnO₃ Following Electrochemical Cycling

Phillips

Bareño

et al. 2015

Advanced Energy Materials

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an end member of the x LiMO 2 •(1 − x ) Li 2 MnO 3 family of compounds, which is being investigated extensively for application as positive electrodes in high-energy batteries. [3][4][5] Pure Li 2 MnO 3 adopts a layered Li[Li 1/3 Mn 2/3 ]O 2 structure in which the Li + and Mn 4+ ions occupy the octahedral interstices of a cubic close-packed oxygen lattice. [ 6 ] Although rich in Li + , lithium extraction from this compound is difficult and typical experimental capacities are markedly lower than the theoretical value. [7][8][9] In addition, the oxide's performance degrades signifi cantly and irreversibly on electrochemical cycling. Several studies have discussed possible reasons for the oxide's behavior and performance degradation. These reasons include the simultaneous extraction of Li + and oxygen, oxidation of Mn 4+ to a higher valence, exchange of Li + /H + -especially during high-temperature cycling, reversible oxidation of the oxygen ions, oxygen vacancy creation followed by rearrangement of transition metal (TM) atoms, and the development of a lithium-depleted surface layer with reduced Mn ions. [10][11][12][13][14][15][16] In this article, we supplement previous spectroscopy and microscopy studies with data from scanning transmission electron microscopy (STEM)-based characterization of pristine, electrochemically cycled, and electron-irradiated Li 2 MnO 3 . Specifi cally, we use a combination of annular bight fi eld (ABF), low angle annular dark fi eld (LAADF), and high angle annular dark fi eld (HAADF) imaging to examine crystal structural changes, and electron energy loss spectroscopy (EELS) to determine Mn-ion valence changes. The microscopy data are complemented by synchrotron-based X-ray diffraction (XRD) data obtained at Argonne's Advanced Photon Source (APS). A viable model is presented which describes the structural/electronic transformations both on the oxide surface and in the bulk.Our data indicate that, upon electrochemical cycling, Li 2 MnO 3 undergoes structural and electronic transitions both in the near-surface regions and in the bulk of the oxide particles. Although complex and nonhomogeneous, the observed nanostructures can be primarily characterized by Mn atoms occupying formerly Li positions leading to spinel and/or disordered rock-salt crystal structures. The EELS data indicate severe oxygen loss and reduced Mn valence, especially at areas near the particle surfaces. The observations on the cycled samples Although the Li-excess layered-oxide Li 2 MnO 3 has a high theoretical capacity, structural transformations within the oxide during electrochemical cycling lead to relatively low experimental capacities, hindering its use in practical applications. Here, aberration-corrected scanning transmission electron microscopy/electron energy loss spectroscopy and high-resolution X-ray diffraction are used to characterize the oxide following electrochemical cycling. Microscopy reveals the coexistence of regions with local monoclinic, spinel, and rock-salt symmetries, indicating localized and inh...

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Section: Discussionsupporting

confidence: 84%

Section: Discussionmentioning

confidence: 97%

On the Localized Nature of the Structural Transformations of Li₂MnO₃ Following Electrochemical Cycling

Phillips

Bareño

et al. 2015

Advanced Energy Materials

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“…[ 18,21 ] This MnO 2 component can intercalate Li + in the following discharge. According to Rana et al, [ 19,20 ] this MnO 2 -type structure changes to an Li 2 MnO 3 -type structure when Li + are inserted into it during discharge. Moreover, it is reported that the Mn ions remain in its tetravalent oxidation state throughout the whole cycle.…”

Section: Introductionmentioning

confidence: 97%

Synthesis and Characterization of High‐Energy, High‐Power Spinel‐Layered Composite Cathode Materials for Lithium‐Ion Batteries

Bhaskar

Krueger²,

Siozios³

et al. 2014

Advanced Energy Materials

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the LiNi 0.5 Mn 1.5 O 4 material is intensively investigated due to its high-voltage electrochemical activity, excellent rate capability as well as cycling stability. [2][3][4][5][6][7] LiNi 0.5 Mn 1.5 O 4 exists mainly in two crystallographic structures according to the oxygen stoichiometry in the material. [ 2,[8][9][10] The cation-ordered spinel (space group P 4 3 32) which is oxygen-stoichiometric, contains all the Mn ions in their tetravalent form. [ 11 ] At the same time in the cation-disordered structure (space group Fd 3 m) , in addition to the tetravalent Mn species, some of the Mn ions exist in the trivalent form as a result of oxygen deficiency from the crystal lattice. [ 12 ] This is mainly associated with the synthesis temperature. According to Pasero et al. [ 10 ] when the synthesis temperature exceeds ≈650 °C, the structure of LiNi 0.5 Mn 1.5 O 4 transforms gradually from the cationordered to cation-disordered. In the cation-ordered structure, the only electrochemically active species is Ni 2+ . The electrochemical reaction takes place at ≈4.7 V with two plateaus corresponding to Ni 2+ / Ni 3+ and Ni 3+ /Ni 4+ reactions, respectively. [ 2,12 ] Meanwhile, in the cation-disordered structure, a slight electrochemical activity is observed around 4.0 V versus Li/Li + as a result of Mn 3+ /Mn 4+ electrochemical reaction. [ 12 ] However, this material offers only a theoretical capacity of ≈148 mAh g −1 in the usual cycling voltage range 3.5-5.1 V. [ 13 ] It is possible to intercalate a second Li + into the material at voltage <3.0 V which in turn increases the capacity delivered. [ 1,14 ] For this purpose a Li excess electrode must be used as the counter electrode during cycling. Moreover, this process is believed to induce Jahn-Teller distortion of the structure due to the existence of excessive amount of Mn 3+ which in turn results in an average oxidation state of Mn less than +3.5. [ 1,14,15 ] The layered lithium-rich (Li-rich) materials with a general composition x Li 2 MnO 3 · (1 -x ) LiMO 2 (M = Mn, Co, Ni) are known to deliver capacities >250 mAh g −1 when cycled within the voltage range 2.0-4.8 V. [ 16 ] This material has a complex structure which is reported either as composites with nanodomains of Li 2 MnO 3 -and LiMO 2 -like features or as their solid solutions. [17][18][19][20] The powder diffraction patterns of this material

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“…This secondary mechanism becomes more significant at higher temperature. [12][13][14] Despite the promise of lithium rich TM oxides to deliver very high capacities, one significant limitation remains the large voltage and capacity fade observed upon extended electrochemical cycling. 15,16 A number of studies have attempted to link structural changes in lithium-rich TM oxides with electrochemical stability and cycling behavior.…”

mentioning

confidence: 99%

Raman Microscopy of Lithium-Manganese-Rich Transition Metal Oxide Cathodes

Ruther

Callender

Zhou

et al. 2014

J. Electrochem. Soc.

125

101

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Lithium-rich and manganese-rich (LMR) layered transition metal (TM) oxide composites with general formula xLi 2 MnO 3 · (1-x)LiMO 2 (M = Ni, Co, Mn) are promising cathode candidates for high energy density lithium ion batteries. Lithium-manganese-rich TM oxides crystallize as a nanocomposite layered phase whose structure further evolves with electrochemical cycling. Raman spectroscopy is a powerful tool to monitor the crystal chemistry and correlate phase changes with electrochemical behavior. While several groups have reported Raman spectra of lithium rich TM oxides, the data show considerable variability in terms of both the vibrational features observed and their interpretation. In this study, Raman microscopy is used to investigate lithium-rich and manganese-rich TM cathodes as a function of voltage and electrochemical cycling at various temperatures. No growth of a spinel phase is observed within the cycling conditions. However, analysis of the Raman spectra does indicate the structure of LMR-NMC deviates significantly from an ideal layered phase. The results also highlight the importance of using low laser power and large sample sizes to obtain consistent data sets. Lithium-manganese-rich TM oxides form as the integrated structure of two layered phases: xLi 2 MnO 3 with C2/m space group symmetry and (1-x)LiMO 2 (M = Co, Mn, Ni, Fe, Cr) with R3m space group symmetry. While the exact structure of lithium-rich TM oxides has been the subject of much debate, a number of recent studies conclude that the material forms as the composite of these two distinct phases with nanoscale domains of Li 2 MnO 3 and LiMO 2 character. 1-6The intense interest in lithium excess cathodes stems from the potential to deliver very large reversible capacities (>200 mAh g −1 ) when charged beyond 4.5 V vs. Li 0 /Li + . 7 Part of the capacity derives from electrochemical activation of the Li 2 MnO 3 component at voltages beyond 4.4 V. Two mechanisms have been proposed for this activation. The dominant mechanism appears to be the simultaneous removal of lithium and oxygen to form a composition similar to MnO 2 . [8][9][10][11] Protons from electrolyte decomposition may also exchange for lithium. This secondary mechanism becomes more significant at higher temperature.12-14 Despite the promise of lithium rich TM oxides to deliver very high capacities, one significant limitation remains the large voltage and capacity fade observed upon extended electrochemical cycling. 15,16 A number of studies have attempted to link structural changes in lithium-rich TM oxides with electrochemical stability and cycling behavior.9,17-25 In particular, several groups have applied Raman microscopy to understand the structure and structural evolution of lithium-rich, manganese-rich TM oxides of nickel, manganese, and cobalt (hereafter LMR-NMC). 18,19,24,[26][27][28][29][30][31] Raman microscopy offers high spatial resolution (< 1μm 3 ), large field of view, and chemical specificity, making it an ideal tool to investigate both the pristine material and comp...

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Structural Changes in Li₂MnO₃ Cathode Material for Li‐Ion Batteries

Cited by 204 publications

References 56 publications

On the Localized Nature of the Structural Transformations of Li₂MnO₃ Following Electrochemical Cycling

On the Localized Nature of the Structural Transformations of Li₂MnO₃ Following Electrochemical Cycling

Synthesis and Characterization of High‐Energy, High‐Power Spinel‐Layered Composite Cathode Materials for Lithium‐Ion Batteries

Raman Microscopy of Lithium-Manganese-Rich Transition Metal Oxide Cathodes

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Structural Changes in Li2MnO3 Cathode Material for Li‐Ion Batteries

Cited by 204 publications

References 56 publications

On the Localized Nature of the Structural Transformations of Li2MnO3 Following Electrochemical Cycling

On the Localized Nature of the Structural Transformations of Li2MnO3 Following Electrochemical Cycling

Synthesis and Characterization of High‐Energy, High‐Power Spinel‐Layered Composite Cathode Materials for Lithium‐Ion Batteries

Raman Microscopy of Lithium-Manganese-Rich Transition Metal Oxide Cathodes

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Product

Resources

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Structural Changes in Li₂MnO₃ Cathode Material for Li‐Ion Batteries

On the Localized Nature of the Structural Transformations of Li₂MnO₃ Following Electrochemical Cycling

On the Localized Nature of the Structural Transformations of Li₂MnO₃ Following Electrochemical Cycling