point
・α is originally stable only at high temperatures-Li₃PS₄We have clarified the reason why it can be preserved by synthesis and rapid cooling due to rapid temperature rise.
・The α phase has an extremely low surface energy and is thermodynamically stable in the medium temperature range in the nano-sized region.
・Time that integrates theory and experiment-temperature-Metamorphosis (TTT(Fig.) and presented guidelines for the theoretical creation of metastable phases.
overview
Professor Akira Miura, Assistant Professor Yuta Fujii, and Professor Seiji Tadanaga of the Hokkaido University Graduate School of Engineering; Mr. Baek Woo-hyun of the University of Michigan's Department of Materials Science and Engineering; Assistant Professor Sunwen Hao of the University's Department of Materials Science and Engineering; Professor Shigeo Mori of the Osaka Public University Graduate School of Engineering; Associate Professor Atsushi Sakuta; Specially Appointed Researcher Ding Hei; Hayashi of the Osaka Public University Graduate School of Engineering and the Tohoku University Institute for Materials Research A research group consisting of Professor Terutoshi, Professor Keiichi Mizuguchi of the Graduate School of Science, Tokyo Metropolitan University, Professor Chikako Moriyoshi of the Graduate School of Advanced Science and Engineering, Hiroshima University, and Principal Researcher Shogo Kawaguchi of the High Brightness Photon Science Research Center (JASRI) is developing next-generation all-solid-state batteries.*1solid electrolyte*2We have solved the mystery of why the high-temperature phase (α-Li₃PS₄) with the highest lithium ion conductivity in the material "Li₃PS₄" can be synthesized through a rapid temperature increase process.
Li₃PS₄αThe phase is480℃It is thermodynamically stable only at high temperatures above and has low ionic conductivity when cooled to room temperature.γIt will undergo a phase transition. However, in recent years, by rapidly heating (rapidly raising the temperature) the glass precursor,αA phase is formed, and then it is kept rapidly cooled to room temperature (quenched).*3) has been reported to be possible.
The research group uses first-principles calculations*4and a large synchrotron radiation facilitySPring-8*5のビームラインBL13XUを用いた高時間分解能のin-situCombined with line diffraction experiments, nano-sizedαPreferential nucleation of phases*6is caused in the intermediate temperature range, and the crystal growth can be suppressed by a short holding time, resulting in a metastableαWe discovered that this is the reason why phases can be selectively synthesized and retained. This result provides rational material design guidelines for the synthesis of metastable materials.
Diagram: Li₃PS₄ polymorphism*7Time to draw the body's synthesis pathway-temperature-transformation(TTT)
Glossary
*1all solid state battery…A secondary battery that uses a solid electrolyte instead of the traditional liquid electrolyte. Highly safe with no risk of flammable liquid leakage.
＊2solid electrolyte…A solid that has ionic conductivity but no electronic conductivity. especiallyLi₃PS₄is one of the most famous solid electrolytes that play a role in transporting lithium ions.
*3quench…A method of rapidly cooling a substance from a high-temperature state to maintain its high-temperature structure and state at room temperature.
*4first principles calculation…A method of accurately predicting and calculating the electronic state and energy of materials on a computer by calculating the wave function of quantum mechanics without relying on experimental data or empirical rules.
*5 SPring-8…This is a large synchrotron radiation facility that produces the world's highest performance synchrotron radiation, located in Harima Science Park City in Hyogo Prefecture and owned by RIKEN. User support is provided by the High Brightness Photon Science Research Center (JASRI) is being carried out.SPring-8(Spring Eight)'s name isSuperPhotonring-8GeVOriginated from.SPring-8A wide range of research is being conducted using synchrotron radiation, including nanotechnology, biotechnology, and industrial applications.
*6nucleation…The initial process in which a new crystalline phase is born from a precursor (such as an amorphous).
＊7polymorphism…Crystals have the same chemical composition but different atomic arrangement (crystal structure).Li₃PS₄forαphase (high temperature phase),βphase (medium temperature phase),γ相（低温相）が存在する。
掲載誌情報
【発表雑誌】Nature Communications（英国の総合科学誌）
[Paper title]Time-Temperature-Transformation Diagrams to Navigate the Nucleation and Quenchability of Metastable α-Li₃PS₄(Time-temperature-transformation diagram to explore nucleation and quenching properties of metastable α-Li₃PS₄)
[Author] Akira Miura1, Woohyeon Baek2、藤井雄太1、忠永清治1, Rana Hossain1, Aichi Yamashita3, Keiichi Mizuguchi3, Chikako Moriyoshi4, Shintaro Kobayashi5, Shogo Kawaguchi5, Ding Hee6, Shigeo Mori6, Atsushi Sakuta6, Akitoshi Hayashi6、7, Wenhao Sun2（1北海道大学大学院工学研究院、2ミシガン大学材料科学工学科、3Graduate School of Science, Tokyo Metropolitan University,4広島大学大学院先進理工系科学研究科、5高輝度光科学研究センター、6大阪公立大学大学院工学研究科、7東北大学金属材料研究所）
[Publication URL]https://doi.org/10.1038/s41467-026-76661-7
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