Diminishing Space-Charge Layer Effect of Zinc Anodes by an Anion-Immobilized Electrolyte Membrane

Abstract

The Zn dendrite issue, which is closely related to the creation of the space-charge region upon local anion depletion during cycling, has plagued the practical applications of aqueous Zn metal batteries (ZMBs). Herein, we propose a Kevlar-derived hydrogel (KevlarH) electrolyte with immobilized anions to diminish the space-charge layer effect. SO 4 2− anions are strongly tethered to amide groups of polymer chains, which mitigates the concentration polarization of interfacial Zn 2+ ions by preventing the anion depletion. Furthermore, the relatively weak interaction between Zn 2+ cations and carbonyl groups can redistribute Zn 2+ -ion flux without sacrificing the ion diffusion rate. The synergistic "zincophilic" and "anionphilic" building blocks enable dendrite-free Zn deposition behavior and suppressed side reactions, thereby extending the lifespan of a Zn metal anode up to 3500 h with an ultrahigh Coulombic efficiency of 99.87%. Importantly, the KevlarH electrolyte can be directly used to assemble high-voltage bipolar ZMBs and break the 2 V barrier in aqueous ZMBs.

Crowding Effect-Induced Zinc-Enriched/Water-Lean Polymer Interfacial Layer Toward Practical Zn-Iodine Batteries

“…This kinetic result indicated that the Zn-CCS polymer crowding layer exhibited the function of repelling anions (I 3 – and SO 4 2– ) and accelerating the desolvation of [Zn­(H 2 O) 6 ] 2+ . In addition, the normalized density of Zn 2+ was significantly higher at the Zn interface, which was consistent with the properties of the Zn-CCS interface layer (Figure h) . Finally, the charging and discharging process of Zn-CCS||I 2 /AC was observed by in situ Raman which could detect the distribution of iodide on the surface of the zinc anode in real time.…”

“…In addition, the normalized density of Zn 2+ was significantly higher at the Zn interface, which was consistent with the properties of the Zn-CCS interface layer (Figure 5h). 65 Finally, the charging and discharging process of Zn-CCS||I 2 /AC was observed by in situ Raman which could detect the distribution of iodide on the surface of the zinc anode in real time. Only the weak signal of I 3…”

Dilemma of Low-Cost Filter Paper as Separator: Toughen Its Wet Strength for Robust Aqueous Zinc-Ion Batteries

“…The coupling of anions to cations reduces the free ion concentration and lowers the conductivity, and the movement of the anions themselves also reduces the proportion of Zn 2+ -ion migration in the total conductance (Zn 2+ -ion transfer number). − Thus, it is the attraction of the wet strength agent to SO 4 2– that allows the SO 4 2– anion to be linked to the polymer and immobilized in the WSFP separator. This not only mitigates the concentration polarization of the Zn 2+ ions at the interface by preventing anion depletion but also increases the Zn 2+ -ion transference number . The schematic diagram demonstrates the influence of WSFP and the FP separator on the transport and diffusion of Zn 2+ and SO 4 2– , as displayed in Figure f.…”

“…It is clear that the cell with WSFP has a lower resistance at all tested temperatures, indicating faster ion transport in the AZIBs (Figure S4a–c). Besides, the curve fitted according to the Arrhenius equation ( ) in Figure b shows that the cell with WSFP delivers a lower desolvation barrier (42.07 kJ mol –1 ) than the battery with GF (44.1 kJ mol –1 ) and FP separator (46 kJ mol –1 ), indicating an improved capability of desolvation of the (Zn­(H 2 O) 6 ) 2+ . , Moreover, the Zn 2+ transference number with different separators were measured by using a chronoamperometry (CA) method at a constant polarization potential of 10 mV (Figure S5a,b). Compared with the Zn 2+ -ion transference number of 0.322 for the cell with the GF separator, the Zn 2+ -ion number of the battery with the WSFP separator is higher, reaching 0.79, as shown in Figure c.…”

Highly Reversible Zinc Metal Anodes Enabled by Solvation Structure and Interface Chemistry Modulation

“…Highly concentrated electrolytes have been substantiated to weaken the solvation interaction between Zn 2+ and H 2 O in the electrolyte by breaking the hydrogen bond (H-bond) network in spite of the high cost, which inspires the widespread exploitation of various inorganic and organic additives. [20][21][22][23][24][25][26][27][28][29][30][31][32][33] The introduction of these additives can usually tailor the Zn 2+ solvation sheath, accelerate the de-solvation process and readily construct an electrode/electrolyte interface owing to the strong attraction with Zn meal. [34][35][36][37][38][39][40][41][42] Therefore, the Zn 2+ flux can be efficiently regulated to a certain extent, thus leading to a dendrite-free and non-corrosive Zn deposition.…”