Oxygen loss and surface degradation during electrochemical cycling of lithium-ion battery cathode material LiMn<sub>2</sub>O<sub>4</sub>

Gao, Xiang; Ikuhara, Yumi H.; Fisher, Craig A. J.; Huang, Rong; Kuwabara, Akihide; Moriwake, Hiroki; Kohama, Keiichi; Ikuhara, Y.

doi:10.1039/c8ta08083f

Cited by 75 publications

(80 citation statements)

References 67 publications

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“…Such a surface structure, as presented in the atomic models (Fig. 6e ), could be considered as a cation-mixed Mn 3 O 4 -type structure 59 – 62 , which is likely due to S-deposition-induced Li leaching and subsequent TM ion migration, as predicted by our DFT calculations. The lowered delithiation voltage (by 1.6 V as compared with the bulk 15 ) in the S-deposited surface suggests that Li ions are easily leached out from the surface during the heat treatment.…”

Section: Resultsmentioning

confidence: 58%

Highly reversible oxygen redox in layered compounds enabled by surface polyanions

et al. 2020

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Oxygen-anion redox in lithium-rich layered oxides can boost the capacity of lithium-ion battery cathodes. However, the over-oxidation of oxygen at highly charged states aggravates irreversible structure changes and deteriorates cycle performance. Here, we investigate the mechanism of surface degradation caused by oxygen oxidation and the kinetics of surface reconstruction. Considering Li 2 MnO 3 , we show through density functional theory calculations that a high energy orbital (lO 2p') at under-coordinated surface oxygen prefers over-oxidation over bulk oxygen, and that surface oxygen release is then kinetically favored during charging. We use a simple strategy of turning under-coordinated surface oxygen into polyanionic (SO 4) 2− , and show that these groups stabilize the surface of Li 2 MnO 3 by depressing gas release and side reactions with the electrolyte. Experimental validation on Li 1.2 Ni 0.2 Mn 0.6 O 2 shows that sulfur deposition enhances stability of the cathode with 99.0% capacity remaining (194 mA h g −1) after 100 cycles at 1 C. Our work reveals a promising surface treatment to address the instability of highly charged layered cathode materials.

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Section: Resultsmentioning

confidence: 58%

Highly reversible oxygen redox in layered compounds enabled by surface polyanions

et al. 2020

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“…In the O K ‐edge spectra, prepeak (peak a) is ascribed to the hybridization between Mn 3d and O 2p levels. The intensity of this peak can reflect the O content in Mn coordination shell; [ 37,62,63 ] the weaker intensity means the more lacking of O (more oxygen vacancies). [ 37,62 ] In the Mn L 2,3 ‐edge spectra, peaks L 2 and L 3 can be attributed to the transitions from 2p 1/2 and 2p 3/2 core states to 3d unoccupied states localized on the exited Mn n + .…”

Section: Resultsmentioning

confidence: 99%

Investigation into the Phase–Activity Relationship of MnO₂ Nanomaterials toward Ozone‐Assisted Catalytic Oxidation of Toluene

Yang

Guo

Cai

et al. 2021

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Manganese dioxide (MnO2), with naturally abundant crystal phases, is one of the most active candidates for toluene degradation. However, it remains ambiguous and controversial of the phase–activity relationship and the origin of the catalytic activity of these multiphase MnO2. In this study, six types of MnO2 with crystal phases corresponding to α‐, β‐, γ‐, ε‐, λ‐, and δ‐MnO2 are prepared, and their catalytic activity toward ozone‐assisted catalytic oxidation of toluene at room temperature are studied, which follow the order of δ‐MnO2 > α‐MnO2 > ε‐MnO2 > γ‐MnO2 > λ‐MnO2 > β‐MnO2. Further investigation of the specific oxygen species with the toluene oxidation activity indicates that high catalytic activity of MnO2 is originated from the rich oxygen vacancy and the strong mobility of oxygen species. This work illustrates the important role of crystal phase in determining the oxygen vacancies’ density and the mobility of oxygen species, thus influencing the catalytic activity of MnO2 catalysts, which sheds light on strategies of rational design and synthesis of multiphase MnO2 catalysts for volatile organic pollutants’ (VOCs) degradation.

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“…[ 40 ] The observed Mn dissolution under highly charged states indicates the surface instability of highly delithiated LiMn 2 O 4 and LiNi 0.5 Mn 1.5 O 4 , which could result in anion‐redox‐induced global oxygen mobility, [ 32 ] oxygen loss, TM reduction, and side reactions with the organic electrolytes. For example, with combined XPS, electron energy loss spectroscopy (EELS), scanning transmission electron microscopy (STEM), and density functional theory (DFT) calculations, Tang et al [ 48 ] reported the reduction of surface Mn upon charging and oxidation of surface Mn upon discharging, which is contrary to what are expected in the bulk; Gao et al [ 49 ] used atomic‐level STEM to directly characterize and visualize oxygen loss, Mn reduction, and surface reconstruction upon charging; using epitaxial LiMn 2 O 4 thin films, Hirayama et al [ 50 ] showed that surface instability/reconstruction and Mn dissolution are surface dependent and more pronounced at (110) than at (111) surface. These observations have shed light on the fundamental mechanism of high‐voltage instability of spinel cathodes, especially at the surface.…”

Section: Degradation Mechanisms Of Spinel Cathodesmentioning

confidence: 99%

Lithium Manganese Spinel Cathodes for Lithium‐Ion Batteries

Huang

Dong

et al. 2020

Advanced Energy Materials

228

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Spinel LiMn2O4, whose electrochemical activity was first reported by Prof. John B. Goodenough's group at Oxford in 1983, is an important cathode material for lithium‐ion batteries that has attracted continuous academic and industrial interest. It is cheap and environmentally friendly, and has excellent rate performance with 3D Li+ diffusion channels. However, it suffers from severe degradation, especially under extreme voltages and during high‐temperature operation. Here, the current understanding and future trends of the spinel cathode and its derivatives with cubic lattice symmetry (LiNi0.5Mn1.5O4 that shows high‐voltage stability, and Li‐rich spinels that show reversible hybrid anion‐ and cation‐redox activities) are discussed. Special attention is given to the degradation mechanisms and further development of spinel cathodes, as well as concepts of utilizing the cubic spinel structure to stabilize high‐capacity layered cathodes and as robust framework for high‐rate electrodes. “Good spinel” surface phases like LiNi0.5Mn1.5O4 are distinguished from “bad spinel” surface phases like Mn3O4.

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Oxygen loss and surface degradation during electrochemical cycling of lithium-ion battery cathode material LiMn₂O₄

Abstract: Atomic-resolution STEM and EELS analysis provide insights into microscopic mechanisms behind oxygen loss and capacity fade in spinel-structured lithium-ion battery cathode material LiMn2O4.

Cited by 75 publications

References 67 publications

Highly reversible oxygen redox in layered compounds enabled by surface polyanions

Highly reversible oxygen redox in layered compounds enabled by surface polyanions

Investigation into the Phase–Activity Relationship of MnO₂ Nanomaterials toward Ozone‐Assisted Catalytic Oxidation of Toluene

Lithium Manganese Spinel Cathodes for Lithium‐Ion Batteries

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Oxygen loss and surface degradation during electrochemical cycling of lithium-ion battery cathode material LiMn2O4

Abstract: Atomic-resolution STEM and EELS analysis provide insights into microscopic mechanisms behind oxygen loss and capacity fade in spinel-structured lithium-ion battery cathode material LiMn2O4.

Cited by 75 publications

References 67 publications

Highly reversible oxygen redox in layered compounds enabled by surface polyanions

Highly reversible oxygen redox in layered compounds enabled by surface polyanions

Investigation into the Phase–Activity Relationship of MnO2 Nanomaterials toward Ozone‐Assisted Catalytic Oxidation of Toluene

Lithium Manganese Spinel Cathodes for Lithium‐Ion Batteries

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Oxygen loss and surface degradation during electrochemical cycling of lithium-ion battery cathode material LiMn₂O₄

Investigation into the Phase–Activity Relationship of MnO₂ Nanomaterials toward Ozone‐Assisted Catalytic Oxidation of Toluene