Fabrication of atomically controlled interfaces with extremely low interfacial resistance in all-solid-state Li batteries

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K05256
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 36020:Energy-related chemistry
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: Nishio Kazunori 東京工業大学, 物質理工学院, 特任准教授 (60805117)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 超低抵抗界面 / 全固体Li電池 / 硫化物固体電解質－正極界面 / 清浄界面 / 薄膜型電池 / エピタキシャル薄膜

Outline of Final Research Achievements

In this study, an ideal model interface with a clean and atomically well-defined interface structure was formed and quantitatively studied to elucidate the origin of the interface resistance between the sulfide solid electrolyte and the positive electrode in all-solid-state Li batteries.
The quantitative evaluation of the interface resistance between Li3PS4 and various cathode materials, including LiCoO2 and LiNi0.8Co0.15Al0.05O2, revealed a crucial finding. We confirmed that the formation of the interface with Li3PS4 leads to a chemical reaction layer with S diffusion to the positive electrode side. This layer, in turn, results in an extremely high interfacial resistance, rendering the battery inoperable. These results underscore the importance of understanding the chemical reaction layer as the origin of the interface resistance, which could pave the way for improving the performance of all-solid-state Li batteries.

Free Research Field

固体物理、固体化学、全固体電池

Academic Significance and Societal Importance of the Research Achievements

これまでに硫化物固体電解質と正極間の界面抵抗の起源として空間電荷層、化学もしくは電気化学的に生成される反応層などが提唱されコンセンサスが得られていなかった。しかし、本研究によって理想的な清浄な界面を形成した場合に、界面抵抗の起源が化学反応層の生成に由来することを明らかにできた。起源を明らかにすることで、抵抗起源となる反応層生成を抑制するための界面設計を能動的に行うことが可能となる。さらに、反応層を抑制して低抵抗な界面を構築できることも実証できたことから、高速充放電できる全固体Li電池の向けて重要な知見が得られた。