Improved electro-kinetics of new electrolyte composition for realizing high-performance zinc-bromine redox flow battery
Yogapriya Vetriselvam,
Gnana Sangeetha Ramachandran,
Raghupandiyan Naresh,
Karuppusamy Mariyappan,
Ragupathy Pitchai,
Mani Ulaganathan
Affiliations
Yogapriya Vetriselvam
CSIR-Central Electrochemical Research Institute, Karaikudi 630003, India
Gnana Sangeetha Ramachandran
CSIR-Central Electrochemical Research Institute, Karaikudi 630003, India
Raghupandiyan Naresh
CSIR-Central Electrochemical Research Institute, Karaikudi 630003, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
Karuppusamy Mariyappan
CSIR-Central Electrochemical Research Institute, Karaikudi 630003, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
Ragupathy Pitchai
CSIR-Central Electrochemical Research Institute, Karaikudi 630003, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India; Corresponding author at: CSIR-Central Electrochemical Research Institute, Karaikudi 630003, India.
Mani Ulaganathan
Department of Physics, Amrita School of Physical Sciences, Amrita Vishwa Vidyapeetham, Coimbatore 641 112, India; Functional Materials Laboratory, Amrita School of Engineering, Amrita Vishwa Vidyapeetham, Coimbatore 641 112, India; Corresponding author at: Department of Physics, Amrita School of Physical Sciences, Amrita Vishwa Vidyapeetham, Coimbatore 641 112, India.
Aqueous Redox Flow Batteries (ARFB) are the most prominent technology for large-scale energy storage applications. The energy density of the ARFBs is mainly determined by the electrolyte components, which highly influence the flow battery performance. In the present work, we acutely investigated the various electrolyte compositions and optimized the best electrolyte for realizing the high performance of Zn-Br2 ARFBs. The electrode kinetics, such as rate constant, exchange current density, conductivity, and diffusion coefficient, were analyzed using electrochemical techniques, cyclic voltammetry, and electrochemical impedance analysis. It was observed that zinc bromide (ZnBr2) + perchloric acid (HClO4) + 1-Ethyl-1-methylmorpholinium bromide (MEM) + N-ethyl-N-methylpyrrolidinium bromide (MEP) and ZnBr2 + zinc chloride (ZnCl2) + MEM + MEP electrolytes showed improved performance, where the redox kinetics of 2Br-/Br2 redox couple is greatly enhanced. The presence of perchloric acid unlocks the capacity of full electro-oxidation of bromide (Br-) to bromine (Br2) as it involves 1e- per Br-, which would be highly beneficial to attain high energy density. Further, Zn-Br2 RFB adopted with optimized electrolyte formulation ZnBr2 + HClO4 + MEM+ MEP shows a better round-trip efficiency and displays a stable long cycling performance over 200 cycles with an energy (EE) and coulombic efficiency (CE) of > 68% and > 92%, respectively.
