Insight on the Double‐Edged Sword Role of Water Molecules in the Anode of Aqueous Zinc‐Ion Batteries

Abstract

As promising candidates for aqueous metal batteries, aqueous zinc‐ion batteries (ZIBs) have attracted more attention due to their superior safety, low cost, and environmentally benign characteristics. Solvent water plays a double‐edged sword role that cannot be ignored in the electrochemical performance and long cycling stability of the batteries. The hydrated zinc ions of the solvated structure can boost the diffusion kinetics of zinc ions, whereas the released active water molecules during desolvation can lead to notorious hydrogen evolution reactions, dendrites growth, and surface passivation at the unstable interface between the electrolyte and the anode. Unlike previous reports that summarize recent research progress, this review focuses on the double‐edged sword role of water molecules in the anode during electrochemical processes in ZIBs. The influencing mechanism of water molecules on the stability of zinc anode during the energy storage process is systematically discussed, including the basic theory, water regulation strategies, and recent reports. The two‐faced identity of the water molecules in aqueous electrolyte is profoundly revealed herein, and some revelatory insights and possible strategies are provided for the future design on stable and durable zinc anodes of high‐performance ZIBs.

Trade-off between Zincophilicity and Zincophobicity: Toward Stable Zn-Based Aqueous Batteries

“…The hydrated [Zn­(H 2 O) x ] 2+ ion complex, free water outside the Zn 2+ -solvated sheath, and/or desolvated water molecules can lead to Zn chemical instability, along with aggravation of nonuniform Zn deposition in the aqueous environment. , In addition to constructing a dehydrated environment at the interface between the electrolyte and Zn anode, recently, from the perspective of regulating the solvation structure of Zn 2+ , well-ordered nanoporous structural materials, including metal–organic frameworks (MOFs), − covalent organic frameworks, − and zeolite molecular, have been employed to alleviate the concentration gradient at the interface via ion sieving effect for highly reversible Zn-metal anodes (Figure ). Generally, the supersaturated electrolyte layer is capable of inhibiting dendrites formation and parasitic reactions via weakening Zn 2+ solvation effect and promoting desolvation kinetics. , For instance, ZIF-7 with narrow channels (2.94 Å in size window) was employed as a host to reduce the reactivity of water molecules and confine the association of solvated Zn 2+ -H 2 O ions for a homogeneous Zn deposition .…”

Reversible adsorption with oriented arrangement of a zwitterionic additive stabilizes electrodes for ultralong-life Zn-ion batteries

“…(3) Some organic additives are insoluble in water, calling for expensive organic Zn salts such as Zn(CF 3 SO 3 ) 2 to improve the solubility, which seriously increases the cost of the electrolyte system. 11 Therefore, an additive with low cost and a good ability to stabilize both AEI and CEI just only by trace addition is an ideal choice for the preparation of high performance AZIBs.…”

Robust Artificial Interlayer with High Ionic Conductivity and Mechanical Strength toward Long‐Life Na‐Metal Batteries

“…[1][2][3][4][5][6][7] However, the limited resource of lithium impedes their large-scale application. [8][9][10][11][12][13] Therefore, it is urgent to seek a cost-effective and more gainable energy-storage systems. Compared to lithium batteries, sodium (Na) batteries present a lot of advantages, including the costeffective and plenty of the raw materials.…”