Zinc-bromine redox flow batteries with superpower density

Unlike their cousins, vanadium redox flow batteries (RFBs), which suffer from intrinsic low energy density, zinc-bromine RFBs have high theoretical energy densities (440 Wh/kg). However, the poor kinetics and poor reversible behavior of Br₂/Br⁻ redox activity pose significant barriers to realizing that potential.

To increase the efficiency of the flow cell, researchers at the Central Electrochemical Research Institute (CECRI) in India have developed graphite felt (GF) supported platinum-nickel (PtNi) bimetallic alloy-based electrode. The 3D structure GF -based metal particles decorated electrode-based flow cells showed an impressive performance at all the tested conditions.

The Ni-rich Pt_0.5Ni₁@HT-GF-based flow cell accomplished a superpower density of about 1550 mW cm⁻², which is greater than that of a bare GF-based flow cell at 1260 mW cm⁻². The cycle life showed excellent stability up to 300 cycles with coulombic, voltage, and energy efficiency of 97%, 86%, and 83%, respectively.

According to the researchers, the improved redox kinetics parameters are due to the high electro-catalytic nature of the heat-treated Ni-rich PtNi coating deposited on the GF. In the process of testing, the sample cell was subjected to different current densities from 20 to 140 mA cm⁻².

Considering the high cost of platinum, the metal’s content was kept to a minimum and the redox reaction was augmented on the back of nickel’s catalytic activity. The bimetal catalyst was deposited on the 3D GF network electrode via a chemical reduction method.

The new research is said to offer a promising approach to developing effective electrode materials for a superpower RFB system. The scientists discuss their findings in “Nanocatalyzed PtNi Alloy Intact @3D Graphite Felt as an Effective Electrode for Super Power Redox Flow Battery,” which was recently published in Advanced Materials.