Organic Multiple Redox Semi‐Solid‐Liquid Suspension for Li‐Based Hybrid Flow Battery
Xuefeng Zhang, Peiyao Zhang, Hongning Chen
Abstract
Abstract Li‐based hybrid flow batteries are very promising in the energy storage market for their high cell voltage and scale‐up flexibility. However, the low volumetric capacity of catholyte has limited their practical application. A novel concept of organic multiple redox semi‐solid‐liquid (MRSSL) suspension was proposed and demonstrated by taking advantage of active materials in both liquid and solid phases in the suspension. In this study, high solubility of 2,2,6,6‐tetramethylpiperidine‐1‐oxyl (TEMPO) in the liquid phase and high reversibility of 10‐methylphenothiazine (MPT) composite in the solid phase were employed to develop a high‐performance and low‐cost organic MRSSL Li‐based hybrid flow battery. It achieved a small voltage gap (<0.1 V) between liquid and solid phase, high cell voltage (≈3.4 V) and high energy density (260 Wh L −1 ). Due to the synergistic interactions between the liquid‐phase TEMPO and the solid‐phase MPT, the viscosity of the MRSSL suspension was significantly reduced. An intermittent‐flow‐mode test of TEMPO‐MPT MRSSL suspension was conducted, which proved that the suspension had an applicable cycling performance with high volumetric capacity (50 Ah L −1 ). The organic MRSSL suspension concept offers a new approach to increase the volumetric capacity and energy density of Li‐based hybrid flow batteries by combining various low‐cost solid and liquid organic active materials.