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Journal Articles

Reversible structural changes and high-rate capability of Li$$_{3}$$PO$$_{4}$$-modified Li$$_{2}$$RuO$$_{3}$$ for lithium-rich layered rocksalt oxide cathodes

Taminato, So*; Hirayama, Masaaki*; Suzuki, Kota*; Kim, K.-S.*; Tamura, Kazuhisa; Kanno, Ryoji*

Journal of Physical Chemistry C, 122(29), p.16607 - 16612, 2018/07

 Times Cited Count:5 Percentile:55.06(Chemistry, Physical)

Lithium-rich layered rocksalt oxides are promising cathode materials for lithium-ion batteries. We investigate the effects of surface modification by amorphous Li$$_{3}$$PO$$_{4}$$ on the structures and electrochemical reactions in the surface region of an epitaxial Li$$_{2}$$RuO$$_{3}$$(010) film electrode. Structural characterization using SXRD, HAXPES, and NR shows that surface modification by Li$$_{3}$$PO$$_{4}$$ resulted in the partial substitution of P for Li in the surface region of Li$$_{2}$$RuO$$_{3}$$. The modified (010) surface exhibits better rate capability at 20 C compared to the unmodified surface. ${it In situ}$ surface XRD confirmed that highly reversible structural changes occurred at the modified surface during lithium (de)intercalation. These results demonstrate that this surface modification stabilizes the crystal structure in the surface region, and it can improve the rate capability of lithium-rich layered rocksalt oxide cathodes.

Journal Articles

Study on the deterioration mechanism of layered rock-salt electrodes using epitaxial thin films; Li(Ni, Co, Mn)O$$_{2}$$ and their Zr-O surface modified electrodes

Abe, Machiko*; Iba, Hideki*; Suzuki, Kota*; Minamishima, Hiroaki*; Hirayama, Masaaki*; Tamura, Kazuhisa; Mizuki, Junichiro*; Saito, Tomohiro*; Ikuhara, Yuichi*; Kanno, Ryoji*

Journal of Power Sources, 345, p.108 - 119, 2017/03

 Times Cited Count:8 Percentile:50.02(Chemistry, Physical)

The surface structure of the Li(Ni, Co, Mn)O$$_{2}$$ electrode was studied during charge/discharge process using electrochemical methods and X-ray/Neutron scattering techniques. It was found that during charge/discharge process the coverage of spinel structure increased. The spinel structure has low electrochemical activity and is not involved in Li insertion/extraction. After the surface modification, it was found that the coverage of the spinel structure did not increase. Further, it was also found out that the Li concentration at the electrode/electrolyte interface increased.

Journal Articles

Lithium intercalation and structural changes at the LiCoO$$_{2}$$ surface under high voltage battery operation

Taminato, So*; Hirayama, Masaaki*; Suzuki, Kota*; Tamura, Kazuhisa; Minato, Taketoshi*; Arai, Hajime*; Uchimoto, Yoshiharu*; Ogumi, Zempachi*; Kanno, Ryoji*

Journal of Power Sources, 307, p.599 - 603, 2016/03

 Times Cited Count:21 Percentile:25.56(Chemistry, Physical)

An epitaxial-film model electrode of LiCoO$$_{2}$$(104) was fabricated on SrRuO$$_{3}$$(100)/Nb:SrTiO$$_{3}$$(100) using pulsed laser deposition. The 50 nm thick LiCoO$$_{2}$$(104) film exhibited lithium (de-)intercalation activity with a first discharge capacity of 119 mAh g$$^{-1}$$ between 3.0 and 4.4 V, followed by a gradual capacity fading with subsequent charge-discharge cycles. In contrast, a 3.2 nm thick Li$$_{3}$$PO$$_{4}$$-coated film exhibited a higher intercalation capacity of 148 mAh g$$^{-1}$$ with superior cycle retention than the uncoated film. In situ surface X-ray diffraction measurements revealed a small lattice change at the coated surface during the (de-)intercalation processes compared to the uncoated surface. The surface modification of LiCoO$$_{2}$$ by the Li$$_{3}$$PO$$_{4}$$ coating could lead to improvement of the structural stability at the surface region during lithium (de-)intercalation at high voltage.

Journal Articles

Structural analysis of electrode-electrolyte interface in lithium batteries

Kanno, Ryoji*; Hirayama, Masaaki*; Suzuki, Kota*; Tamura, Kazuhisa

Hyomen Kagaku, 37(2), p.52 - 59, 2016/02

Batteries are a key technology in today's society. Since the lithium-ion configuration has been widely accepted, significant efforts have been devoted to attain high energy and power densities to produce an excellent energy storage system without any safety issue. To improve the reliability and power characteristics of batteries, deep insights into the reactions at the electrode/electrolyte interface are necessary. The model systems with epitaxial thin-film electrodes might be suitable for understanding these reactions. The in situ techniques for directly observing surface structural changes of the electrodes have been developed for surface X-ray scattering and neutron reflectivity techniques. These techniques are reviewed and future studies on the interfacial reaction in batteries will be discussed.

Journal Articles

Interfacial analysis of surface-coated LiMn$$_{2}$$O$$_{4}$$ epitaxial thin film electrode for lithium batteries

Suzuki, Kota*; Hirayama, Masaaki*; Kim, K.-S.*; Taminato, So*; Tamura, Kazuhisa; Son, J.-Y.*; Mizuki, Junichiro; Kanno, Ryoji*

Journal of the Electrochemical Society, 162(13), p.A7083 - A7090, 2015/08

 Times Cited Count:8 Percentile:65.9(Electrochemistry)

The effects of surface coatings on LiMn$$_{2}$$O$$_{4}$$ were investigated using LiMn$$_{2}$$O$$_{4}$$ epitaxial thin films with a thickness of 30 nm. Bare and surface-coated LiMn$$_{2}$$O$$_{4}$$ epitaxial thin films were synthesized on SrTiO$$_{3}$$(111) substrates using a pulsed laser deposition method. The surface coating, which was formed using the solid electrolyte Li$$_{3}$$PO$$_{4}$$ and had a thickness of 3 nm, improved the reversibility of the electrochemical reactions undergone by the LiMn$$_{2}$$O$$_{4}$$ epitaxial thin films. The changes induced in the surface structure were maintained during battery operation; in contrast, the bare LiMn$$_{2}$$O$$_{4}$$ thin film exhibited structural degradation and Mn dissolution. The structural changes induced in the coated electrode and the increase in its surface stability were intrinsic effects of the Li$$_{3}$$PO$$_{4}$$ coating and improved the electrochemical performance of the LiMn$$_{2}$$O$$_{4}$$ thin-film electrode.

Journal Articles

Mechanistic studies on lithium intercalation in a lithium-rich layered material using Li$$_{2}$$RuO$$_{3}$$ epitaxial film electrodes and ${{it in situ}}$ surface X-ray analysis

Taminato, So*; Hirayama, Masaaki*; Suzuki, Kota*; Kim, K.-S.*; Zheng, Y.*; Tamura, Kazuhisa; Mizuki, Junichiro; Kanno, Ryoji*

Journal of Materials Chemistry A, 2(34), p.17875 - 17882, 2014/11

 Times Cited Count:18 Percentile:38.29(Chemistry, Physical)

The surface structure of a lithium-rich layered material and its relation to intercalation properties were investigated by synchrotron X-ray surface structural analyses using Li$$_{2}$$RuO$$_{3}$$ epitaxial-film model electrodes with different lattice planes of (010) and (001). Electrochemical charge-discharge measurements confirmed reversible lithium intercalation activity through both planes, corresponding to three-dimensional lithium diffusion within the Li$$_{2}$$RuO$$_{3}$$. The (001) plane exhibited higher discharge capacities compared to the (010) plane under high rate operation (over 5 C). Direct observations of surface structural changes by ${{it in situ}}$ surface X-ray diffraction (XRD) and surface X-ray absorption near edge structure (XANES) established that an irreversible phase change occurs at the (010) surface during the first (de)intercalation process, whereas reversible structural changes take place at the (001) surface.

Journal Articles

Characterization of nano-sized epitaxial Li$$_{4}$$Ti$$_{5}$$O$$_{12}$$(110) film electrode for lithium batteries

Kim, K.-S.*; Tojigamori, Takeshi*; Suzuki, Kota*; Taminato, So*; Tamura, Kazuhisa; Mizuki, Junichiro; Hirayama, Masaaki*; Kanno, Ryoji*

Denki Kagaku Oyobi Kogyo Butsuri Kagaku, 80(10), p.800 - 803, 2012/10

 Times Cited Count:11 Percentile:65.85(Electrochemistry)

Electrochemical properties and structure changes of nano-sized Li$$_{4}$$Ti$$_{5}$$O$$_{12}$$ during lithium (de)intercalation wereinvestigated using a two-dimensional thin film electrode. Li$$_{4}$$Ti$$_{5}$$O$$_{12}$$ thin films were deposited on a Nb:SrTiO$$_{3}$$(110)substrate by a pulsed laser deposition technique. In situ X-ray diffraction measurements clarified the drastic structural changes of the Li$$_{4}$$Ti$$_{5}$$O$$_{12}$$film upon soaking in the electrolyte and during the first intercalation and deintercalation processes. The surfaceregion of Li$$_{4}$$Ti$$_{5}$$O$$_{12}$$ had a different structure from the bulk during electrochemical cycling and could cause the nanosizedLi$$_{4}$$Ti$$_{5}$$O$$_{12}$$ electrodes to have high capacities and poor stabilities.

Journal Articles

Dynamic structural changes at LiMn$$_{2}$$2O$$_{4}$$/electrolyte interface during lithium battery reaction

Hirayama, Masaaki*; Ido, Hidekazu*; Kim, K.-S.*; Cho, W.*; Tamura, Kazuhisa; Mizuki, Junichiro; Kanno, Ryoji*

Journal of the American Chemical Society, 132(43), p.15268 - 15276, 2010/11

 Times Cited Count:249 Percentile:2.18(Chemistry, Multidisciplinary)

Epitaxial LiMn$$_{2}$$O$$_{4}$$ thin films with restricted lattice planes (111) and (110) are grown on SrTiO$$_{3}$$ substrates by pulsed laser deposition. In situ SXRD studies have revealed dynamic structural changes that reduce the atomic symmetry at the electrode surface during the initial electrochemical reaction. The surface structural changes commence with the formation of an electric double layer, which is followed by surface reconstruction when a voltage is applied in the first charge process. Transmission electron microscopy images after 10 cycles confirm the formation of a solid electrolyte interface (SEI) layer on both the (111) and (110) surfaces and Mn dissolution from the (110) surface. The (111) surface is more stable than the (110) surface. The electrode stability of LiMn$$_{2}$$O$$_{4}$$ depends on the reaction rate of SEI formation and the stability of the reconstructed surface structure.

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:28 Percentile:25.57(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:32 Percentile:27.86(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:36 Percentile:35.43(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:18 Percentile:45.08(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:75 Percentile:9.91(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:76 Percentile:5.57(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$$_{4}$$.

Journal Articles

Spin gap in Tl$$_2$$Ru$$_2$$O$$_7$$ and the possible formation of Haldane chains in three-dimensional crystals

Lee, S.*; Park, J.-G.*; Adroja, D. T.*; Khomskii, D.*; Streltsov, S.*; McEwen, K. A.*; Sakai, Hironori; Yoshimura, Kazuyoshi*; Anisimov, V. I.*; Mori, Daisuke*; et al.

Nature Materials, 5(6), p.471 - 476, 2006/06

 Times Cited Count:94 Percentile:5.53(Chemistry, Physical)

Here we show that the three-dimensional cubic system of Tl$$_2$$Ru$$_2$$O$$_7$$ most probably evolves into a one-dimensional spin-one Haldane system with a spin gap below 120 K, accompanied by anomalies in the structure, resistivity, and susceptibility. We argue that these anomalies are due to an orbital ordering of Ru $$4d$$ electrons, with a strong coupling among three degrees of freedom: orbital, spin, and lattice. Our work provides a unique example of the spontaneous formation of Haldane system with an insight into the intriguing interplay of different degrees of freedom.

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