Multifunctional Carbon Felt Electrode with N‐Rich Defects Enables a Long‐Cycle Zinc‐Bromine Flow Battery with Ultrahigh Power Density

Abstract

Zinc-bromine flow batteries (ZBFBs) are regarded as one of the most promising technologies for energy storage owing to high energy density and low cost. However, the sluggish reaction kinetics of Br 2 /Br − couples and zinc dendrite issue lead to low power density and poor cycle stability. Herein, a multifunctional carbon felt-based electrode (NTCF) with N-rich defects is fabricated for ZBFBs. The defects with abundant N-containing groups on carbon fibers of NTCF provide high catalytic activity on Br 2 /Br − reactions. Simultaneously, the lower energy barrier of N-rich defects to adsorb zinc atoms, and more deposition sites on NTCF induce more uniform zinc deposition. Thus, a ZBFB using NTCF as both the anode and cathode can stably operate at an unprecedentedly high current density of 180 mA cm −2 with a coulombic efficiency of 97.25%. Moreover, a long cycle life of over 140 cycles with a coulombic efficiency of 98.93% for a Zn symmetric flow battery at 80 mA cm −2 is achieved under a high areal capacity of 40 mAh cm −2 . This current density and areal capacity are by far the highest values ever reported for Zn symmetry flow batteries. Therefore, this work provides an available approach to improve the power density and cycle life of ZBFBs.

Anode for Zinc-Based Batteries: Challenges, Strategies, and Prospects

“…Water molecules were pushed out from the primary solvation shell of (Zn­(H 2 O) 6 ) 2+ , thus reducing the number of active water molecules near the anode surface and constraining corresponding adverse reactions. Second, glucose molecules tended to absorb parallel to the zinc slab (Z-GP) rather than vertical (Z-GV). ,, The adsorption of glucose thus shielded the cutting-edge electric field and increased the nucleated overpotential of zinc, leading to uniform zinc deposition. As a result, the assembled symmetric cell could run stably for more than 2000 h at 1 mA cm –2 with 1 mAh cm –2 .…”

“…Second, glucose molecules tended to absorb parallel to the zinc slab (Z-GP) rather than vertical (Z-GV). 65,93,94 The adsorption of glucose thus shielded the cutting-edge electric field and increased the nucleated overpotential of zinc, leading to uniform zinc deposition. As a result, the assembled symmetric cell could run stably for more than 2000 h at 1 mA cm −2 with 1 mAh cm −2 .…”

Towards Integration of Two-Dimensional Hexagonal Boron Nitride (2D h-BN) in Energy Conversion and Storage Devices

“…Thus far, many efforts have been devoted to obviating these shortcomings, using 2D h-BN. The incorporation of 2D h-BN into ZFBs is made through three major pathways: (1) modification of the electrolyte chemistry, (2) reinforcing membranes, and (3) changing the battery configuration [87,88].…”

Redox Flow Batteries: Materials, Design and Prospects

“…However, it was concluded that for higher current densities, electrodes covered with oxygen functional groups on the surface were preferred. W. Lu doped carbon felt electrodes with nitrogen, reaching an EE of 63.07% at 180 mA cm −2 , with a more uniform deposition of zinc on its surface [252]. Mariyappan and coworkers studied the effect of adding a low loading of platinum on graphite felt using a pulsed laser deposition.…”