Proposal of Carbon air secondary battery system charging and discharging using electrochemical reaction and high-temperature thermochemical equilibrium

2021 Fiscal Year Final Research Report

• Project/Area Number: 20K20364
• Project/Area Number (Other): 18H05349 (2018-2019)
• Research Category: Grant-in-Aid for Challenging Research (Pioneering)
• Allocation Type: Multi-year Fund (2020); Single-year Grants (2018-2019)
• Review Section: Medium-sized Section 31:Nuclear engineering, earth resources engineering, energy engineering, and related fields
• Research Institution: Tokyo Institute of Technology
• Principal Investigator: IHARA MANABU 東京工業大学, 物質理工学院, 教授 (90270884)
• Co-Investigator(Kenkyū-buntansha): 長谷川 馨 東京工業大学, 物質理工学院, 助教 (50644944)
• Project Period (FY): 2018-06-29 – 2022-03-31
• Keywords: 固体酸化物燃料電池 / 蓄電デバイス / CO2電解

Outline of Final Research Achievements

Power-to-gas-to-power systems that produce H2 by water electrolysis and generate electricity from this H2 are promising long-term electric energy storage systems for extensive installation of renewable energies. However, such systems require complex thermal management, and must be sufficiently large to enable the use of waste heat for higher efficiency. Here we propose the “carbon/air secondary battery” (CASB) system that uses a C/CO2 reaction with potentially higher volumetric energy density and efficiency than that of the H2/H2O reaction. This system produces C by CO2 electrolysis for energy storage and generates electricity from the C via solid oxide electrolysis cells/fuel cells. Repetitive power generation (10 charge-discharge cycles) of the CASB system with Boudouard equilibrium was firstly demonstrated at 800°C without degradation. The system achieved a maximum Coulombic efficiency of 84%, charge-discharge efficiency of 38%, and power density of 80 mW cm-2.

Free Research Field

原子力工学、地球資源工学、エネルギー学およびその関連分野

Academic Significance and Societal Importance of the Research Achievements

炭素は多くの金属を上回るエネルギー密度を持ち、常に文明活動の主要なエネルギー源であった。近年ではCO2排出制限により低炭素化が必須となっているが、CO2を排出しない方法での炭素の高エネルギー密度、汎用性の積極利用は有用である。本提案ではCO2を二次電池構成物質として繰り返し利用するため、実質のCO2排出はゼロとなる。本提案では、金属、水素に加えて第3の蓄エネルギー媒体としてCO2/Cを利用する挑戦的な提案である。原材料の高い汎用性により、低コスト、大規模な実装が可能になると期待される。