title: High-capacity electrode materials for rechargeable lithium batteries: Li3NbO4-based system with cation-disordered rocksalt structure.
abstract: Rechargeable lithium batteries have rapidly risen to prominence as fundamental devices for green and sustainable energy development. Lithium batteries are now used as power sources for electric vehicles. However, materials innovations are still needed to satisfy the growing demand for increasing energy density of lithium batteries. In the past decade, lithium-excess compounds, Li2MeO3 (Me = Mn(4+), Ru(4+), etc.), have been extensively studied as high-capacity positive electrode materials. Although the origin as the high reversible capacity has been a debatable subject for a long time, recently it has been confirmed that charge compensation is partly achieved by solid-state redox of nonmetal anions (i.e., oxide ions), coupled with solid-state redox of transition metals, which is the basic theory used for classic lithium insertion materials, such as LiMeO2 (Me = Co(3+), Ni(3+), etc.). Herein, as a compound with further excess lithium contents, a cation-ordered rocksalt phase with lithium and pentavalent niobium ions, Li3NbO4, is first examined as the host structure of a new series of high-capacity positive electrode materials for rechargeable lithium batteries. Approximately 300 mAh ⋅ g(-1) of high-reversible capacity at 50 °C is experimentally observed, which partly originates from charge compensation by solid-state redox of oxide ions. It is proposed that such a charge compensation process by oxide ions is effectively stabilized by the presence of electrochemically inactive niobium ions. These results will contribute to the development of a new class of high-capacity electrode materials, potentially with further lithium enrichment (and fewer transition metals) in the close-packed framework structure with oxide ions.
authors.affiliation: Department of Green and Sustainable Chemistry, Tokyo Denki University, Adachi, Tokyo 120-8551, Japan; yabuuchi@mail.dendai.ac.jp komaba@rs.kagu.tus.ac.jp.
authors.forename: Naoaki
authors.identifier: http://orcid.org/0000-0002-9404-5693
authors.initials: N
authors.lastname: Yabuuchi
authors.affiliation: Department of Applied Chemistry, Tokyo University of Science, Shinjuku, Tokyo 162-8601, Japan;
authors.forename: Mitsue
authors.initials: M
authors.lastname: Takeuchi
authors.affiliation: Department of Materials Science and Engineering, Nagoya Institute of Technology, Nagoya, Aichi 466-8555, Japan; Precursory Research for Embryonic Science and Technology, Japan Science and Technology Agency, 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan;
authors.forename: Masanobu
authors.initials: M
authors.lastname: Nakayama
authors.affiliation: Department of Materials Science and Engineering, Nagoya Institute of Technology, Nagoya, Aichi 466-8555, Japan;
authors.forename: Hiromasa
authors.initials: H
authors.lastname: Shiiba
authors.affiliation: Synchrotron Radiation Center, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan;
authors.forename: Masahiro
authors.initials: M
authors.lastname: Ogawa
authors.affiliation: Synchrotron Radiation Center, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan;
authors.forename: Keisuke
authors.initials: K
authors.lastname: Nakayama
authors.affiliation: Synchrotron Radiation Center, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan;
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Ohta
authors.affiliation: R&D Center, GS Yuasa International Ltd., Minami-ku, Kyoto 601-8520, Japan.
authors.forename: Daisuke
authors.initials: D
authors.lastname: Endo
authors.affiliation: R&D Center, GS Yuasa International Ltd., Minami-ku, Kyoto 601-8520, Japan.
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Ozaki
authors.affiliation: R&D Center, GS Yuasa International Ltd., Minami-ku, Kyoto 601-8520, Japan.
authors.forename: Tokuo
authors.initials: T
authors.lastname: Inamasu
authors.affiliation: Department of Green and Sustainable Chemistry, Tokyo Denki University, Adachi, Tokyo 120-8551, Japan;
authors.forename: Kei
authors.initials: K
authors.lastname: Sato
authors.affiliation: Department of Applied Chemistry, Tokyo University of Science, Shinjuku, Tokyo 162-8601, Japan; yabuuchi@mail.dendai.ac.jp komaba@rs.kagu.tus.ac.jp.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Komaba
keywords: anion redox; battery; lithium; positive electrode