Localized Hydrophobicity in Aqueous Zinc Electrolytes Improves Zinc Metal Reversibility

Abstract

The rechargeability of aqueous zinc metal batteries is plagued by parasitic reactions of the zinc metal anode and detrimental morphologies such as dendritic or dead zinc. To improve the zinc metal reversibility, hereby we report a new solution structure of aqueous electrolyte with hydroxyl-ion scavengers and hydrophobicity localized in solvent clusters. We show that although hydrophobicity sounds counterintuitive for an aqueous system, hydrophilic pockets may be encapsulated inside a hydrophobic outer layer, and a hydrophobic anode–electrolyte interface can be generated through the addition of a cation-philic, strongly anion-phobic, and OH–-reactive diluent. The localized hydrophobicity enables less active water and less absorbed water on the Zn anode surface, which suppresses the parasitic water reduction; while the hydroxyl-ion-scavenging functionality further minimizes undesired passivation layer formation, thus leading to superior reversibility (an average Zn plating/stripping efficiency of 99.72% for 1000 cycles) and lifetime (80.6% capacity retention after 5000 cycles) of zinc batteries.

Optimal Interfacial Model between the Alloy Surface and Electrolyte Solvation Structure for a Stable Lithium Metal Electrode

“…As shown by the H-bond ratio with different strengths (Figure S20c), a higher population of strong H-bond exists in the HCE than LCE, owing to more contact ion pairs (CIPs) and ionic aggregates (AGGs) with less solvent molecules in the HCE. It is noteworthy that the HCE (3 mol ZnSO 4 in 1 L of H 2 O) used herein only possesses a relatively high concentration compared with the LCE (1 mol ZnSO 4 in 1 L of H 2 O) due to the limited solubility of ZnSO 4 in H 2 O and the available free solvents in the HCE might still affect the functionality of the alloy/HCE interface. Thus, further improvement in cycling stability of the Zn anode on CuZnAg can be expected by using an advanced Zn HCE with a sharply reduced free solvent amount.…”

“…2− pair stronger in the HCE than LCE but also the H-bond exhibits different features in these two electrolytes. As shown by the H-bond ratio with different strengths (Figure S20c 39 and the available free solvents in the HCE might still affect the functionality of the alloy/HCE interface. Thus, further improvement in cycling stability of the Zn anode on CuZnAg can be expected by using an advanced Zn HCE with a sharply reduced free solvent amount.…”

Quantitative Chemistry in Electrolyte Solvation Design for Aqueous Batteries

“…Besides the strategies of WiSEs and eutectic electrolytes, aqueous electrolytes can be also modified by functional additives (DX, , sulfolane, ,− , MU, DMSO, ,, tetraethylene glycol dimethyl ether (TEGDME), N,N -dimethyl­formamide (DMF), − EMImCl, acrylamide, formamide (FA), trimethyl phosphate (TMP), etc.) to inhibit the HER, expand the ESW, and even improve the low-temperature performance properties, such as a high ionic conductivity, low viscosity, and low freezing point.…”

Superhydrophobic and Conductive Wire Membrane for Enhanced CO2 Electroreduction to Multicarbon Products

“…Recently, hydrophobicity has attracted intense attention for its significant promoting effects in various fields, such as batteries, [26, 27] separation, [28, 29] and catalysis [4, 8, 21, 25, 30–40] . For electrochemical CO 2 reduction in aqueous media, the introduction of hydrophobicity can create gas‐liquid‐solid triple‐phase interfaces (TPI) near the catalysts, which increases the local concentration of CO 2 and reduces the accessibility of water to the catalysts, [4, 8, 21, 33] thus improving the selectivity towards carbon‐based products.…”