A TiN Nanorod Array 3D Hierarchical Composite Electrode for Ultrahigh‐Power‐Density Bromine‐Based Flow Batteries

Abstract

batteries, adopting bromine as cathode, have attracted wide attention due to their advantages of an abundant resource, low cost, and high energy density. [4] Apart from zinc-bromine flow batteries (ZBFBs), which are at the commercial demonstration stage, some new brominebased flow batteries such as quinonebromine flow batteries, [5] lithium-bromine flow batteries, [6] viologen-bromine flow batteries, [7] as well as other types of flow batteries [8] have been widely investigated. However, some common challenges exist for such bromine-based flow batteries. In particular, the high electrochemical polarization caused by the mismatch of the positive and negative redox couple kinetics leads to a low operating current density (40 mA cm −2 for zinc-bromine and viologen-bromine batteries) and lower power density, which seriously hampers the development of bromine-based flow batteries. [9] Thus, the development of high activity electrode materials for Br 2 / Br − is necessary to reduce electrochemical polarization and improve power density, which is truly significant for realizing the commercialization of bromine-based flow batteries.As one of the most commonly used electrode materials for a bromine-based flow battery, carbon materials possess high electronic conductivity, good chemical and electrochemical stability in harsh environments, low cost and controllable morphology and surface states. [10] Because of their unique cell structure, self-supporting 3D bulk carbon materials with good flexibility, large porosity and high electronic conductivity are the most commonly used electrodes for flow batteries, e.g., carbon felt (CF) and graphite felt. [11,12] Wherein, carbon fibers with a diameter of tens of micrometers and length of several centimeters interweave into 3D self-supporting frameworks, which can be arbitrarily tailored and squeezed. Moreover, by adopting such self-supporting 3D bulk carbon electrodes upon which electrochemical reaction occurs, the electrolyte can go through the cell in the way of "flow through". [13] Compared to a "flow by" electrode, the "flow through" electrode will create a larger contact area for electrode and electrolyte and enhance the electrode utilization. [11] However, the poor kinetics for the pristine carbon and the smooth and flat surface of the carbon fibers resulting in relatively less reaction sites lead to a low electrochemical activity and restricted application of the single 3D bulk carbon electrodes. Moreover, the pristine carbon is normally Bromine-based flow batteries are well suited for stationary energy storage due to attractive features of high energy density and low cost. However, the bromine-based flow battery suffers from low power density and large materials consumption due to the relatively high polarization of the Br 2 /Br − couple on the electrodes. Herein, a self-supporting 3D hierarchical composite electrode based on a TiN nanorod array is designed to improve the activity of the Br 2 /Br − couple and increase the power density of the bromine-based flow battery. ...

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

“…Worth noting is that when using a CFbased material as the electrode, the electrolyte goes through the cell body in the way of "flow-through." [15] In this way, the sufficient contact between the electrode and the electrolyte is very important. As a result, it is hard for CF-based materials with such negative natures to demonstrate good performance in ZBFBs.…”

“…This current density is the highest current density for ZBFBs ever reported (Figure 10c). [ 5,6,11,15,21 ] Moreover, the excellent electrochemical activity of NTCF on Br 2 /Br − reactions, and its ability to regulate zinc deposition process contribute to higher areal capacity of ZBFBs. As shown in Figure 10d and Figure S17 (Supporting Information), the battery with NTCF as both cathode and anode shows a high charge areal capacity of 66.6 mAh cm −2 , with a high EE of 75.91% at 80 mA cm −2 .…”

“…All values derive from refs. [ 3,4,9,13,20 ] ); [ 5,6,11,15,21 ] d) charge areal capacity and energy of the ZBFB using NTCF as both anode and cathode at 80 mA cm −2 .…”

Progress and Perspective of the Cathode Materials towards Bromine-Based Flow Batteries

“…However, except for some precious metals and oxides, most metals and metal oxides are unstable in the presence of highly corrosive bromine. So far, metal-based cathode materials currently available for Br-FBs are Pt, TiN, ZrO x , TiO x , WO x , AlO x , etc., which show high activity on Br 2 /Brredox reactions and improve the reversibility of Br 2 /Brredox reactions [38,40,41]. Among them, Pt exhibits good adsorption characteristics towards Br 2 , Brions, and Br 3 ions, which significantly affects the electrochemical reactions of Br 2 /Brcouple on Pt cathode [42,43].…”

Rechargeable Aqueous Zinc‐Ion Batteries with Mild Electrolytes: A Comprehensive Review

“…[183] 2) Surface structures or high zincophilicity of some current collectors help the uniform and dense heterogeneous nucleation of Zn metals, which then further guide the subsequent Zn plating. [179] For ZIBs, the proposed current collectors include Cu, [253] Ti, [119,150,160,254] Ni, [255] stainless steel, [21,256] and a variety of carbon materials (carbon cloth/felt, [257,258] carbon fiber, [182,259] graphite paper [260,261] and graphene foam [67,192] etc).…”