Investigation of interface between complex hydride solid electrolyte and sulfur/carbon composite electrode

2021 Fiscal Year Final Research Report

• Project/Area Number: 19K15305
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 26040:Structural materials and functional materials-related
• Research Institution: Tohoku University
• Principal Investigator: Kisu Kazuaki 東北大学, 金属材料研究所, 助教 (80755645)
• Project Period (FY): 2019-04-01 – 2022-03-31
• Keywords: イオン伝導 / 錯体水素化物 / 二次電池 / 全固体電池 / リチウム硫黄電池

Outline of Final Research Achievements

Complex hydride materials have been widely investigated as potential solid electrolytes because they have good compatibility with the lithium metal anodes used in all-solid-state batteries. However, the de- velopment of all-solid-state batteries utilizing complex hydrides has been difficult as these cells tend to have short cycle lives. This study investigated the capacity fading mechanism of all-solid-state lithium-sulfur (Li-S) batteries using Li4(BH4)3I solid electrolytes by analyzing the cathode microstructure. Cross- sectional scanning electron microscopy observations after 100 discharge-charge cycles revealed crack formation in the Li4(BH4)3 I electrolyte and an increased cathode thickness. Raman spectroscopy indicated that decomposition of the Li4(BH4)3 I solid electrolyte occurred at a constant rate during the cycling tests. To combat these effects, the cycle life of Li-S batteries was improved by increasing the amount of solid electrolyte in the cathode.

Free Research Field

電気化学

Academic Significance and Societal Importance of the Research Achievements

本研究は、錯体水素化物を全固体電池用途としての固体電解質として捉え、電池材料としての安定性評価を本格的に行うという研究であった。研究対象とする錯体水素化物は最もシンプルな構造でかつ代表的な水素化物であるLiBH4を用いて評価を行うことで、水素化物としての共通的な界面安定性を明らかにした。近年、申請者のグループでは、LiBH4を超える高いイオン伝導特性を有する多種多様な錯体水素化物を生み出しており、本研究で得られた基盤的な知見を活かすことで、今後幅広い錯体水素化物固体電解質へと展開が可能となった。