Fig. 1

Summary of ZBFBs research progress in recent years"

Fig. 2

(a) Quaternized polysulfone (QNPSU) reaction formation principle[19]; (b) porous polyolefin/polyethylene glycol (PEG) composite membrane working principle diagram[20]; (c) DFT analysis diagram[20]; (d) Zn2+ concentration distribution and electric field distribution simulation diagram[20]; (e) analysis of PEG-passivated zinc ions calculated by DFT[20]; (f) thermal conductivity analysis of PES-BNNs coated composite diaphragm[21]; (g) electrode zinc dendrite growth diagram after the application of PES-BNNs coated composite diaphragm[21]; (h) glass fiber paper composite diaphragm[22]; (i) typical and novel electroactive titanium mesh anode structure[23]"

Fig. 3

(a) Nafion filled porous membrane preparation flow chart[24]; (b) Nafion filled porous membrane amplification diagram[24]; (c) membrane water cluster amplification diagram[25]; (d) ion conductivity curve of membrane after prehydration treatment[25]; (e) bromine adsorption curve of membrane after prehydration treatment[25]; (f) schematic diagram of the interaction between Nafion and Am-SiO2 in Nafion/Am-SiO2 membranes[26]; (g) UV spectra of solutions filtered by different membranes[26]; (h) changes of Br2 diffusers of different membranes over time[26]"

Fig. 4

Cyclic stability test Mechanical stability analysis after (a) original SPEEK, (b) loading 0.5% SP-p-CT350, (c) loading 1% SP-p-CT350; (d) loading 1.5% SP-p-CT350[27]; (e) stress-strain curves for the Nafion/PP membrane before and after the Br2 storage[24]"

Fig. 5

(a) Schematic diagram of composite membranes[28]; (b) ultraviolet spectra of bromine solutions containing different membranes[28]; (c) surface and cross-sectional images of Daramic membrane[29]; (d) surface and cross-sectional images of MWCNT/PAN-Daramic membrane[29]; (e) the bromine permeability of the prepared membranes[29]; (f) schematic diagram of mechanisms of ion transport and Br2 capture by the U-AS modified membraneduring the ZBFLBs operation[30]"

Fig. 6

(a) Schematic diagram of 3D honeycomb lattice as a ZBFBs cell structure[31], (b) schematic diagram of A1C n channel configuration, where n increases from 1 to 4[31], (c) 4-channel (2×2), 8-channel (2×4), and 16-channel (4×4) cell diagram of HC-ZBFBs[31], (d) schematic illustration of the function of the MesoTi3C2-wrapped PP separator in eliminating Zn0 dendrites and the underlying mechanisms[32], (e) the spontaneous redox process between Zn0 and the Ti-Oe functional group on MesoTi3C2[32]"

Fig. 7

Overview of electrolyte optimization solution[34-38]"

Fig. 8

(a) The influence of 2 mol/L ZnBr2 and NH4Cl concentration on the energy efficiency of ZBFBs[41]; (b) the polarization curve of ZBFBs when 4 mol/L NH4Cl is added in the absence of other supporting electrolytes[41]"

Fig. 9

(a) Zinc dendrite image with 1 mol/L MSA inserted into the edge of graphite felt[43]; (b) local carbon fiber image with 1 mol/L MSA inserted into the edge of graphite felt[43]; (c) zinc dendrite image without MSA inserted into the edge of graphite felt[43]; (d) local carbon fiber image without MSA inserted into the edge of graphite felt[43]"

Fig. 10

(a) Charging curve of zinc-bromine flow battery in 2 mol/L ZnBr electrolyte at 100% utilization; (b) cross section of zinc deposition; (c) schematic diagram of zinc deposition at decreasing concentration[44]"

Fig. 11

(a) After 25 charge and discharge cycles, SEM image of carbon slipper (original, supported zinc chloride, supported zinc perchlorate) of a 9 cm2 microbattery[45]; (b) schematic diagram of the migration process of Cl atoms at the Zn site calculated by DFT[47]; (c) enlarged view of zinc deposition under an optical microscope with a PEG electrode[49]; (d) schematic diagram of step-by-step zinc reduction and deposition process under negative potential bias of zinc electrode and PEG-200 electrolyte[35]; (e)schematic diagram of electrostatic shielding effect[50]; (f) schematic diagram of Cr3+ additive explaining Cr3+ ion shielding of zinc seed[36]"

Fig. 12

Time series of BCA material research in recent years[11, 37-38, 56-62]"

Fig. 13

(a) Comparison of the variation trend of final circulating voltage of different BCA electrolytes;(b) cyclic performance of 7 electrolytes under different BCA effects[62]"

Fig. 14

Magnification of negative zinc deposition during charging at 50 mL/min (a) and 100 ml/min (b) flow rates[63]"

Fig. 15

(a) At a current density of 20 mA/cm2, The distribution of bromine concentration; (b) in the positive electrode at the end of battery discharge at different flow rates of positive electrolyte is 20 mA/cm2 and 40 Current, Coulomb, and energy efficiency of batteries with different positive electrolyte flow rates at mA/cm2; (c) energy efficiency of batteries with different electrolyte flow rates and different electrode thicknesses; (d) energy efficiency of batteries with different electrolyte flow rates and different electrode porosity[65]"