Development of high-voltage and high-energy membrane-free nonaqueous lithium-based organic redox flow batteries

• Published in: Nature communications Vol. 14; no. 1; p. 4753
• Main Authors: Gautam, Rajeev K., Wang, Xiao, Lashgari, Amir, Sinha, Soumalya, McGrath, Jack, Siwakoti, Rabin, Jiang, Jianbing “Jimmy”
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 08.08.2023; Nature Publishing Group; Nature Portfolio
• Subjects: 140/131; 639/301/299/891; 639/4077/4079/891; 639/638/161/891; Batteries; Cathodes; Current density; Electrolytes; Energy efficiency; Energy storage; Erythrocytes; Flow; Genomes; High voltages; Humanities and Social Sciences; Ions; Lithium; Malaria; Membranes; multidisciplinary; Phenothiazine; Rechargeable batteries; s-triazines; Science; Science (multidisciplinary); Solvents; Triazine; Voltage
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-023-40374-y

Lithium-based nonaqueous redox flow batteries (LRFBs) are alternative systems to conventional aqueous redox flow batteries because of their higher operating voltage and theoretical energy density. However, the use of ion-selective membranes limits the large-scale applicability of LRFBs. Here, we report high-voltage membrane-free LRFBs based on an all-organic biphasic system that uses Li metal anode and 2,4,6-tri-(1-cyclohexyloxy-4-imino-2,2,6,6-tetramethylpiperidine)-1,3,5-triazine (Tri-TEMPO), N-propyl phenothiazine (C3-PTZ), and tris(dialkylamino)cyclopropenium (CP) cathodes. Under static conditions, the Li||Tri-TEMPO, Li||C3-PTZ, and Li||CP batteries with 0.5 M redox-active material deliver capacity retentions of 98%, 98%, and 92%, respectively, for 100 cycles over ~55 days at the current density of 1 mA/cm 2 and a temperature of 27 °C. Moreover, the Li||Tri-TEMPO (0.5 M) flow battery delivers an initial average cell discharge voltage of 3.45 V and an energy density of ~33 Wh/L. This flow battery also demonstrates 81% of capacity for 100 cycles over ~45 days with average Coulombic efficiency of 96% and energy efficiency of 82% at the current density of 1.5 mA/cm 2 and at a temperature of 27 °C. Redox flow batteries are promising energy storage systems but are limited in part due to high cost and low availability of membrane separators. Here, authors develop a membrane-free, nonaqueous 3.5 V all-organic lithium-based battery and demonstrate its operation in both static and flow conditions.