Correlation of lithium ion distribution and X-ray absorption near-edge structure in O3- and O2-lithium cobalt oxides from first-principle calculation

Okumura, Toyoki; Yamaguchi, Yoichi; Shikano, Masahiro; Kobayashi, Hironori

doi:10.1039/c2jm32024j

Cited by 43 publications

(42 citation statements)

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“…The Mn L-edge NEXAFS spectrum of this material also supports this oxidation state ( Figure S1). The main energy of the Co ions occurs at 7.721 ± 1 eV, as estimated by the XANES spectrum that coincides with the spectrum of materials with a 3+ oxidation state [30,31]. The Co L-edge NEXAFS spectrum further favors this ( Figure S2).…”

Section: Resultssupporting

confidence: 62%

Soft X-ray Absorption Spectroscopic Investigation of Li(Ni0.8Co0.1Mn0.1)O2 Cathode Materials

et al. 2020

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Herein, we report the soft X-ray absorption spectroscopic investigation for Li(Ni 0.8 Co 0.1 Mn 0.1 ) O 2 cathode material during charging and discharging. These measurements were carried out at the Mn L-, Co L-, and Ni L-edges during various stages of charging and discharging. Both the Mn and Co L-edge spectroscopic measurements reflect the invariance in the oxidation states of Mn and Co ions. The Ni L-edge measurements show the modification of the oxidation state of Ni ions during the charging and discharging process. These studies show that e g states are affected dominantly in the case of Ni ions during the charging and discharging process. The O K-edge measurements reflect modulation of metal-oxygen hybridization as envisaged from the area-ratio variation of spectral features corresponding to t 2g and e g states.Nanomaterials 2020, 10, 759 2 of 11 soft XAS measurements can give a complete account of underlying phenomena due to the orbital symmetry states in the oxide cathode material during charging and discharging. To depict these phenomena, the Ni-rich cathode material, Li(Ni 0.8 Co 0.1 Mn 0.1 )O 2 , is selected for the present investigation and denoted as NCM811. NCM811 is a well-known layered oxide cathode material and preferred for Li rechargeable batteries due to its high capacity [19,20]. Thus, this work investigates NCM811 cathode materials during charging and discharging using soft XAS. Experimental DetailsX-ray diffraction (XRD) experiments prior to electrochemical testing of cathode material were performed with the 9B high-resolution powder diffraction (HRPD) beamline of the Pohang accelerator laboratory (PAL) [21]. Pristine cathode material was also investigated using X-ray absorption near-edge spectroscopy (XANES) imaging measurements to reveal the local electronic structure. These measurements at the Mn K-, Co K-, and Ni K-edge were performed with the 7C X-ray nano imaging (XNI) beamline of the PAL. This beamline utilizes zone plate-based transmission X-ray nanoscopy, which is a kind of transmission X-ray microscopy (TXM), for image formation. A zone plate of diameter 150 µm and 40 nm outermost zone width was used for measurements. This arrangement gave a spatial resolution of 40 nm and a field of view (FOV) of around 50 µm. The X-ray absorption images based on TXM were captured at various energies within a 1 eV interval in the range −20 to 80 eV from the main edge energies of each respective element. The XANES spectrum was extracted from these X-ray absorption images [22].Soft XAS measurements of this cathode material at various charging and discharging states were performed with the 10D XAS-KIST beamline of the same laboratory in total electron yield (TEY) mode. The grating with 1100 grooves/mm was used to measure spectra at the Mn L-, Co L-, Ni L-, and O K-edges. The obtained spectra were background-subtracted and normalized with respect to the post-edge height [23]. Results and Discussion

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Section: Resultssupporting

confidence: 62%

Soft X-ray Absorption Spectroscopic Investigation of Li(Ni0.8Co0.1Mn0.1)O2 Cathode Materials

et al. 2020

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“…The B and C peaks represent the dipole-allowed 1s to 4p transition with and without a shakedown process that originate from a ligand to metal charge transfer. 36,37 The difference in the position of peak C between these products is negligible, which indicates that there is no difference in cobalt oxidation state, and cobalt is located in octahedral sites. 38 Fourier transforms (FTs) of Co K-edge k 3 -weighted EXAFS spectra of l-LCO and h-LCO are demonstrated in Fig.…”

Section: Resultsmentioning

confidence: 96%

Sol–gel synthesis and electrochemical properties of c-axis oriented LiCoO₂for lithium-ion batteries

Gao

Wei

et al. 2015

RSC Adv.

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For better performance of LiCoO2 as cathode for lithium-ion batteries, electrochemical properties of c-axis oriented LiCoO2 were studied. LiCoO2 with controllable intensity ratios of peak (003) to peak (104) were synthesized via a resorcinolformaldehyde sol-gel method, followed by an air-controlled high temperature treatment. Electrochemical measurements shown that LiCoO2 with low degree of c-axis orientation exhibited a better performance than LiCoO2 with high degree of caxis orientation. X-ray absorption spectroscopy was used to reveal the texture-property relationship between different products. The variances could be attributed to different electrochemical active sites created and diffusion lengths for lithium ions related to c-axis orientation.

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“…LiCoO 2 is a wide-band gap semiconductor. As found in previous calculations, 18,36,80,[82][83][84][85] 80 and 5 eV. 51,55,80,83,89 The electronic structure of Mg-doped LiCoO 2 was studied by calculating the electronic band structure and density of states (DOS) with GGA and GGA+U.…”

Section: Electronic Structurementioning

confidence: 82%

Successes and failures of Hubbard-corrected density functional theory: The case of Mg doped LiCoO2

Santana

Kim

Kent

et al. 2014

The Journal of Chemical Physics

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We have evaluated the successes and failures of the Hubbard-corrected density functional theory (DFT+U) approach to study Mg doping of LiCoO 2 . We computed the effect of the U parameter on the energetic, geometric and electronic properties of two possible doping mechanisms: (1) substitution of Mg onto a Co (or Li) site with an associated impurity state and, (2) formation of impurity-state-free complexes of substitutional Mg and point defects in LiCoO 2 . We find that formation of impurity states results in changes on the valency of Co in LiCoO 2 . Variation of the Co U shifts the energy of the impurity state, resulting in energetic, geometric and electronic properties that depend significantly on the specific value of U. In contrast, the properties of the impurity-state-free complexes are insensitive to U. These results identify reasons for the strong dependence on the doping properties on the chosen value of U and for the overall difficulty of achieving agreement with the experimentally known energetic and electronic properties of doped transition metal oxides such as LiCoO 2 .

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Correlation of lithium ion distribution and X-ray absorption near-edge structure in O3- and O2-lithium cobalt oxides from first-principle calculation

Cited by 43 publications

References 50 publications

Soft X-ray Absorption Spectroscopic Investigation of Li(Ni0.8Co0.1Mn0.1)O2 Cathode Materials

Soft X-ray Absorption Spectroscopic Investigation of Li(Ni0.8Co0.1Mn0.1)O2 Cathode Materials

Sol–gel synthesis and electrochemical properties of c-axis oriented LiCoO₂for lithium-ion batteries

Successes and failures of Hubbard-corrected density functional theory: The case of Mg doped LiCoO2

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Correlation of lithium ion distribution and X-ray absorption near-edge structure in O3- and O2-lithium cobalt oxides from first-principle calculation

Cited by 43 publications

References 50 publications

Soft X-ray Absorption Spectroscopic Investigation of Li(Ni0.8Co0.1Mn0.1)O2 Cathode Materials

Soft X-ray Absorption Spectroscopic Investigation of Li(Ni0.8Co0.1Mn0.1)O2 Cathode Materials

Sol–gel synthesis and electrochemical properties of c-axis oriented LiCoO2for lithium-ion batteries

Successes and failures of Hubbard-corrected density functional theory: The case of Mg doped LiCoO2

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Sol–gel synthesis and electrochemical properties of c-axis oriented LiCoO₂for lithium-ion batteries