Self-Assembled Blossom-Shaped NiCoS Nanosheets In Situ Deposited Electrodes: Possessing High Reactivity and Selectivity for Bromine-Based Flow Batteries.

Bromine-based flow batteries (Br-FBs) are emerging rapidly due to their high energy density and wide potential window for renewable energy storage systems. Nevertheless, the sluggish kinetics of the Br/Br reaction on the electrode is considered to be the main challenge contributing to the poor performance of Br-FBs. Herein, we report self-assembled blossom-shaped NiCoS nanosheets, enabling in situ growth on graphite felt (GF) via a one-step hydrothermal method. In the prepared NiCoS-GF, the gaps formed by the nanosheets restrict bromine diffusion, the sulfuretted blossom-shaped structure provides active sites with bromine adsorption capacity, and the synergistic effect of Ni and Co accelerates the electron transfer rate, which allow the electrode to exhibit excellent electrocatalytic activity compared to commercial GF, CoS-GF, and NiS-GF. Moreover, NiCoS-GF demonstrates unique selectivity for enhancing the Br/Br redox reaction compared to the bimetallic oxide of NiCoO-GF. Consequently, the zinc-bromine flow battery (ZBFB) with NiCoS-GF achieves an energy efficiency of 80.16%, which is 16.18% higher than that of the battery with commercialized GF at a current density of 60 mA cm, as well as a maximum power density of 260.75 mW cm at 280 mA cm. The effective enhancement of the performance of ZBFB suggests that NiCoS-GF possesses great application potential in Br-FBs.