Development of all-solid-state thin-film secondary batteries and high energy density cathode materials for all-solid-state lithium secondary batteries

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K05226
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 36010:Inorganic compounds and inorganic materials chemistry-related
• Research Institution: Mie University
• Principal Investigator: Taminato Sou 三重大学, 工学研究科, 助教 (60771201)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 全固体リチウム二次電池 / 正極材料 / 薄膜電池 / LiCoO2 / 高電圧動作 / リチウム脱挿入反応 / パルスレーザー堆積法 / RFマグネトロンスパッタ法

Outline of Final Research Achievements

Thin-film all-solid-state batteries were prepared using a ca. 30 nm thick LiCoO2 thin-film electrode with a layered rock salt structure and an amorphous Li3PO4 solid electrolyte. The LiCoO2 thin-film electrode was tested for high-voltage operation in the all-solid-state battery configuration. The same electrode was also tested in a liquid electrolyte system. In the all-solid- state configuration operating in the range of 3-4.6 V, no significant change in discharge capacity even after 50 cycles of charge-discharge measurements. Furthermore, Li/Li3PO4/LiCoO2/SrRuO3/SrTiO3(100) cell provide high-energy reaction with small degradation in the range of 3-4.8 V by introduction of the solid electrolyte layer between LiCoO2/Li3PO4 interface. Our experimental study suggests the potential of a stable high energy density battery reaction in the all-solid-state battery configuration.

Free Research Field

無機固体化学

Academic Significance and Societal Importance of the Research Achievements

LiCoO2およびLi5FeO4は高電圧，高容量電極反応過程において，いずれも充電時のLi+脱離以外に反応性の高い有機電解液との副反応で不可逆な酸素脱離が進行して正極自身が分解する．その結果，放電時に容量が取り出せずサイクル安定性も低く，液系電池では材料（反応）の使用が見送られてきた．本検討では，特にLiCoO2について，電位窓の広いリン酸塩固体電解質と組み合わせて固体電池として動作させることで高電圧動作条件においても，高容量反応の可逆特性が向上することを見出した．得られた知見は正極材料の高エネルギー密度化に向けた材料探索や反応制御に貢献すると考えられる．