Development of operando soft X-ray XAFS analysis technique for secondary batteries during charge/discharge operation

2023 Fiscal Year Final Research Report

• Project/Area Number: 19K05550
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 34020:Analytical chemistry-related
• Research Institution: University of Hyogo
• Principal Investigator: Nakanishi Koji 兵庫県立大学, 高度産業科学技術研究所, 准教授 (70572957)
• Project Period (FY): 2019-04-01 – 2024-03-31
• Keywords: リチウムイオン電池 / 放射光科学 / 三元系正極 / 電荷補償機構 / 軟X線吸収分光

Outline of Final Research Achievements

We attempted to analyze the charge compensation mechanism of LiNixCoyMnzO2 (NCM), a cathode active material for lithium-ion batteries, using not only hard X-ray 3d transition metals but also soft X-ray Ni, Co, and Mn L absorption edges as well as O K absorption edge XAS measurements to obtain a detailed all-element measurement. NCM electrodes with different composition ratios were used as samples. The results showed that Ni exhibited divalent to tetravalent oxidation/reduction reactions, while Co showed negligible change, Mn did not react at all, and oxygen, which is not a metal, also exhibited oxidization/reduction (redox) reactions. The charge compensation is mainly carried out by Ni regardless of the composition ratio of Ni, Co, and Mn, while oxygen also contributes to the charge compensation.

Free Research Field

放射光科学、分析化学

Academic Significance and Societal Importance of the Research Achievements

LIB NCM系電極は現在の電気自動車においても採用されているが、高性能化を実現可能とする新規蓄電池材料を開発には既存材料の充放電反応機構を詳細に理解し、新規材料設計へとフィードバックする必要がある。軟X線分析を用いた本研究成果から、3d遷移金属だけではなく、アニオンである酸素の寄与を明らかにすることができ、これによりアニオンの改質を念頭に入れた新規材料設計を提案できたことは大きな意義である。