Improvement of hydrogen ab/desorption properties of complex hydride on the basis of lithium ion conduction mechanism

2020 Fiscal Year Final Research Report

• Project/Area Number: 19K15304
• 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: Hokkaido University
• Principal Investigator: Nakagawa Yuki 北海道大学, 工学研究院, 助教 (00787153)
• Project Period (FY): 2019-04-01 – 2021-03-31
• Keywords: 錯体水素化物 / リチウムアラネート / 窒化ホウ素 / リチウムイオン伝導 / 超イオン伝導 / 水素貯蔵 / メカニカルミリング / 固体核磁気共鳴

Outline of Final Research Achievements

In this work, lithium ion conductivity of lithium alanate (LiAlH4) was evaluated by alternating-current impedance analyzer. The effect of ball-milling treatment on LiAlH4 powder was analyzed. Also, the effects of boron nitride (BN) additives with different structures (hexagonal(h-BN), turbostratic(t-BN), and cubic(c-BN)) was investigated. The milling treatment can increase the vacancy concentration at the Li-ion site of inner LiAlH4 grains, which results in the enhancement of the conductivity. The t-BN composite showed a superionic conduction at 80 degree Celsius. The formation of lithium borohydride (LiBH4) species by t-BN addition was observed, which would correlate with the improvement of the conductivity.
In addition, the hydrogen desorption kinetics of LiAlH4 was improved by t-BN addition.

Free Research Field

水素化物エネルギー変換材料

Academic Significance and Societal Importance of the Research Achievements

錯体水素化物の1種であるリチウムアラネート(LiAlH4)に対して、ミリング粉砕処理や異なる構造の窒化ホウ素(BN)添加物により、リチウムイオン伝導度を大幅に向上できることを明らかにした。リチウムイオン伝導体としての錯体水素化物の研究の歴史はまだ浅く、水素化物系のリチウムイオン伝導体の伝導度向上機構についての学術的に重要な知見を得ることができた。また、BN添加物を加えることにより超イオン伝導特性を達成することができたため、更なる改良を行うことで、実社会への応用展開も期待される。