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Journal Articles

Structural changes in surface and bulk LiNi$$_{0.5}$$Mn$$_{0.5}$$O$$_{2}$$ during electrochemical reaction on epitaxial thin-film electrodes characterized by ${it in situ}$ X-ray scattering

Sakamoto, Kazuyuki*; Hirayama, Masaaki*; Konishi, Hiroaki*; Sonoyama, Noriyuki*; Dupr$'e$, N.*; Guyomard, D.*; Tamura, Kazuhisa; Mizuki, Junichiro; Kanno, Ryoji*

Physical Chemistry Chemical Physics, 12(15), p.3815 - 3823, 2010/04

 Times Cited Count:30 Percentile:74.87(Chemistry, Physical)

Surface and bulk structural changes of LiNi$$_{0.5}$$Mn$$_{0.5}$$O$$_{2}$$ were investigated during electrochemical reaction using synchrotron X-ray scattering and a restricted reaction plane consisting of two dimensional epitaxial-film electrodes. The changes in bulk structure confirmed lithium diffusion through the (110) surface, which was perpendicular to the two-dimensional (2D) edges of the layered structure. No (de)intercalation reaction was observed through the (003) surface at voltages of 3.0-5.0 V. However, intercalation did proceed through the (003) plane below 3.0 V, indicating unusual three-dimensional (3D) lithium diffusion in the over-lithiated 2D structure. During the electrochemical process, the surface of the electrode showed different structure changes from those of the bulk structure. The reaction echanism of the intercalation electrodes for lithium batteries is discussed on the basis of surface and bulk structural changes.

Journal Articles

Surface structure of LiNi$$_{0.8}$$Co$$_{0.2}$$O$$_{2}$$; A New experimental technique using in situ X-ray diffraction and two-dimensional epitaxial film electrodes

Sakamoto, Kazuyuki*; Hirayama, Masaaki*; Sonoyama, Noriyuki*; Mori, Daisuke*; Yamada, Atsuo*; Tamura, Kazuhisa; Mizuki, Junichiro; Kanno, Ryoji*

Chemistry of Materials, 21(13), p.2632 - 2640, 2009/05

 Times Cited Count:35 Percentile:72.9(Chemistry, Physical)

Surface and bulk structural changes in LiNi$$_{0.8}$$Co$$_{0.2}$$O$$_{2}$$ were observed during electrochemical reactions using synchrotron X-ray scattering and a restricted reaction plane of two-dimensional (2D) epitaxial-film electrodes. The bulk structural changes confirmed lithium diffusion through the (110) surface, which is perpendicular to the 2D edges of the layered structure. No (de)intercalation reaction was observed through the (003) surface in the voltage range of 3.0-5.0 V. However, intercalation proceeded below 3.0 V, which indicates unusual three-dimensional lithium diffusion in the 2D structure in the overlithiated state. Structural changes at the electrode surface were different from those in the bulk.

Journal Articles

Characterization of electrode/electrolyte interface using ${it in situ}$ X-ray reflectometry and LiNi$$_{0.8}$$Co$$_{0.2}$$O$$_{2}$$ epitaxial film electrode synthesized by pulsed laser deposition method

Hirayama, Masaaki*; Sakamoto, Kazuyuki*; Hiraide, Tetsuya*; Mori, Daisuke*; Yamada, Atsuo*; Kanno, Ryoji*; Sonoyama, Noriyuki*; Tamura, Kazuhisa; Mizuki, Junichiro

Electrochimica Acta, 53(2), p.871 - 881, 2007/12

 Times Cited Count:38 Percentile:65(Electrochemistry)

An ${it in situ}$ experimental technique was developed for detecting structure changes at the electrode/electrolyte interface of lithium cell using synchrotron X-ray reflectometry and two-dimensional model electrodes with a restricted lattice plane. The electrode was constructed with an epitaxial film of LiNi$$_{0.8}$$Co$$_{0.2}$$O$$_{2}$$ synthesized by the pulsed laser deposition method. These films provided an ideal reaction field suitable for detecting structure changes at the electrode/electrolyte interface during the electrochemical reaction. The X-ray reflectometry indicated a formation of a thin-film layer at the LiNi$$_{0.8}$$Co$$_{0.2}$$O$$_{2}$$ (1 1 0)/electrolyte interface during the first charge-discharge cycle, while the LiNi$$_{0.8}$$Co$$_{0.2}$$O$$_{2}$$ (0 0 3) surface showed an increase in the surface roughness without forming the surface thin-film layer.

Journal Articles

Mechanistic study on lithium intercalation using a restricted reaction field in LiNi$$_{0.5}$$Mn$$_{0.5}$$O$$_{2}$$

Sakamoto, Kazuyuki*; Konishi, Hiroaki*; Sonoyama, Noriyuki*; Yamada, Atsuo*; Tamura, Kazuhisa; Mizuki, Junichiro; Kanno, Ryoji*

Journal of Power Sources, 174(2), p.678 - 682, 2007/12

 Times Cited Count:21 Percentile:58.03(Chemistry, Physical)

Structure changes of LiNi$$_{0.5}$$Mn$$_{0.5}$$O$$_{2}$$ were detected at the electrode/electrolyte interface of lithium cell using synchrotron X-ray scattering and two-dimensional model electrodes. The electrodes were constructed by an epitaxial film of LiNi$$_{0.5}$$Mn$$_{0.5}$$O$$_{2}$$ synthesized by pulsed laser deposition (PLD) method. The orientation of the film depends on the substrate plane; the 2D layer of LiNi$$_{0.5}$$Mn$$_{0.5}$$O$$_{2}$$ is parallel to the SrTiO$$_{3}$$(1 1 0) substrate ((1 1 0) LiNi$$_{0.5}$$Mn$$_{0.5}$$O$$_{2}$$//(1 1 0) SrTiO$$_{3}$$), while the 2D layer is perpendicular to the SrTiO$$_{3}$$(1 1 1) substrate ((0 0 3) LiNi$$_{0.5}$$Mn$$_{0.5}$$O$$_{2}$$//(1 1 1) SrTiO$$_{3}$$). The ${it in situ}$ X-ray diffraction of LiNi$$_{0.5}$$Mn$$_{0.5}$$O$$_{2}$$(0 0 3) confirmed three-dimensional lithium diffusion through the two-dimensional transition meal layers. The intercalation reaction of LiNi$$_{0.5}$$Mn$$_{0.5}$$O$$_{2}$$ will be discussed.

Journal Articles

Characterization of electrode/electrolyte interface for lithium batteries using ${it in situ}$ synchrotron X-ray reflectometry; A New experimental technique for LiCoO$$_{2}$$ model electrode

Hirayama, Masaaki*; Sonoyama, Noriyuki*; Abe, Takashi*; Minoura, Machiko*; Ito, Masumi*; Mori, Daisuke*; Yamada, Atsuo*; Kanno, Ryoji*; Terashima, Takahito*; Takano, Mikio*; et al.

Journal of Power Sources, 168(2), p.493 - 500, 2007/06

 Times Cited Count:80 Percentile:90.21(Chemistry, Physical)

A new experimental technique was developed for detecting structure changes at electrode/electrolyte interface of lithium cell using X-ray reflectometry and two-dimensional model electrodes with a restricted lattice-plane. The electrodes were constructed with an epitaxial film of LiCoO$$_{2}$$ synthesized by pulsed laser deposition method. The anisotropic properties were confirmed by electrochemical measurements. ${it Ex situ}$ X-ray reflectivity measurements indicated that the impurity layer existed on the as-grown LiCoO$$_{2}$$ was dissolved and a new SEI layer with lower density was formed after soaking into the electrolyte. ${it In situ}$ X-ray reflectivity measurements indicated that the surface roughness of the intercalation (1 1 0) plane increased with applying voltages, while no significant changes in surface morphology were observed for the intercalation non-active (0 0 3) plane during the pristine stage of the charge-discharge process.

Journal Articles

Characterization of electrode/electrolyte interface with X-ray reflectometry and epitaxial-film LiMn$$_{2}$$O$$_{4}$$ electrode

Hirayama, Masaaki*; Sonoyama, Noriyuki*; Ito, Masumi*; Minoura, Machiko*; Mori, Daisuke*; Yamada, Atsuo*; Tamura, Kazuhisa; Mizuki, Junichiro; Kanno, Ryoji*

Journal of the Electrochemical Society, 154(11), p.A1065 - A1072, 2007/00

 Times Cited Count:80 Percentile:94.59(Electrochemistry)

Structural changes at electrode/electrolyte interface of a lithium cell were studied by X-ray reflectometry and two-dimensional model electrodes with a restricted lattice plane of LiMn$$_{2}$$O$$_{4}$$. The ex situ reflectometry indicated that a thin impurity layer covered the lattice plane of the as-grown film. The impurity layer was dissolved and a solid-electrolyte-interface-like phase appeared after the electrode was soaked into the electrolyte. The in situ observation clarified that the surface reactivity depended on the lattice planes of the spinel; the defect layer at the (111) plane was stable during the electrochemical reaction, whereas a slight decrease in the film thickness was observed for the (110) plane. Our surface characterization of the intercalation electrode indicated that the surface structure changes during the pristine stage of the change-discharge processes and these changes are dependent on the lattice orientation of LiMn$$_{2}$$O$$_{4}$$.

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