Study of fast charging/discharging mechanism at room temperature in multivalent ion batteries using carbon nanocomposite

2023 Fiscal Year Final Research Report

• Project/Area Number: 21K14711
• Research Category: Grant-in-Aid for Early-Career Scientists
• Allocation Type: Multi-year Fund
• Review Section: Basic Section 36020:Energy-related chemistry
• Research Institution: Tokyo University of Agriculture and Technology
• Principal Investigator: Okita Naohisa 東京農工大学, 工学(系)研究科(研究院), 助教 (70846625)
• Project Period (FY): 2021-04-01 – 2024-03-31
• Keywords: 多価イオン電池 / 正極材料 / カーボン複合体 / 室温動作 / 高速充放電 / ナノ材料 / 固溶体反応 / Dual-salt電解液

Outline of Final Research Achievements

Encapsulated iron phosphate/carbon and vanadium phosphate/carbon composites have been successfully synthesized as positive electrodes for magnesium-ion batteries. These batteries can charge and discharge reversibly at room temperature and under ultrafast charge-discharge conditions, with a charge-discharge time of 6 minutes. The research has identified several key factors that enable ultrafast positive electrode reactions for magnesium-ion batteries. These include the nanocrystals, which are highly dispersed and directly embedded in conductive carbon, and a solvation structure that facilitates the approach of magnesium ions to the positive electrode, as seen in a dual-salt electrolyte. The study also revealed that magnesium-ion insertion/extraction of the positive electrodes proceeds reversibly through a solid-solution reaction, unlike lithium-ion insertion/extraction via a two-phase reaction, which is believed to be the reason behind the achievement of ultrafast charge-discharge.

Free Research Field

電気化学

Academic Significance and Societal Importance of the Research Achievements

マグネシウムイオン電池において、困難であった室温動作および高速充放電を達成したカーボン複合体材料をモデルに、その要因を明らかにすることで、高速充放電化のための材料設計・電解液/電極界面設計の指針を得ることが可能となる。本指針はマグネシウムイオン電池やリチウムイオン電池に限らず、カルシウム、亜鉛、アルミニウムなどの様々な多価イオン電池にも展開が可能であり、それらの超高速正極の設計指針や反応挙動の知見を提供するものとして、波及効果は大きいと考えられる。