Triggering Zn²⁺ Unsaturated Hydration Structure via Hydrated Salt Electrolyte for High Voltage and Cycling Stable Rechargeable Aqueous Zn Battery

Abstract

Ocean‐like free water in conventional aqueous electrolytes limits operating voltage and induces parasitic reactions in rechargeable Zn metal batteries (AZMBs). Herein, a hydrated salt electrolyte (HSE), which suppresses the presence of free water and triggers an unsaturated hydration structure (Zn(H2O)n2+, n < 6), is proposed to circumvent the parasitic reactions occurring on the zinc anode and cathode and elevate the decomposition voltage (to ≈2.55 V vs Zn2+/Zn). In a full cell with a transition metal oxide cathode, the parasitic reactions of dissolution and diffusion of discharge products are inhibited, and high discharge capacity retention above 80% at 500 mA g‐1 and super‐stable Coulombic efficiency (average value ≈99.97%) are delivered. Moreover, when applied in a high‐voltage AZMB with zinc hexacyanoferrate cathode, the full cell yields an average output voltage above 1.8 V together with a 132.3 Wh kg‐1 energy density at 10 mA g‐1 and 1.78 V output voltage combining high energy density and power density (88.5 Wh kg‐1/106.2 W kg‐1). The exceptional electrochemical performance of HSE indicates rosy prospects for the prevention of parasitic reactions in AZMBs, a key step on the road to further commercialization of AZMBs.

Chelate‐Capped Nano‐AgZn3 Dual Interphase Remodeling the Local Environment for Reversible Dendrite‐Free Zinc Anode

“…2− ] species were inhibited by strong electrostatic interactions between the Zn 2+ cation and the anions. [35,49] On the HZC-Ag@Zn surface, the 𝝂-SO 4 2− band shifted to higher frequencies and the content of the [Zn 2+ (H 2 O) 5 •OSO 3…”

“…To a certain extent, zincophobic SEIs may impede the transport kinetics of Zn 2+ or electron migration during the zinc-plating process. [32,33] Moreover, strong solvation may hinder zinc ion diffusion at the electrode interface, [34][35][36][37] which accelerates uneven zinc deposition and induces dendrite growth. Some zincophilic metal coatings, such as Ag [38][39][40] and Sn, [41] have been used as heterogeneous seeds to achieve dendrite-free zinc deposition by inducing uniform nucleation.…”

Interphases in aqueous rechargeable zinc metal batteries

“…A series of salts with Zn 2+ as the cation including zinc bis(-triuoromethanesulfonyl)imide (Zn(TFSI) 2 ), 30,46,74 zinc tri-uoromethanesulfonate (Zn(OTf) 2 ), 31,61 zinc sulfate (ZnSO 4 ), 51,75 zinc perchlorate (Zn(ClO 4 ) 2 ), 76 and zinc acetate (Zn(Ac) 2 ) 77 have been investigated in aqueous electrolytes within their very limited solubility (<4 m). There is no signicant difference among these different anion chemistries in terms of zinc anode electrochemical performance, except for a better HER suppression in Zn(Ac) 2 -based neutral electrolyte.…”

Triggering Mixed Cationic‐Anionic Redox in Cu2‐xSe Cathodes via Tailored Charge‐Carrier for High Energy Density Aqueous Zn Batteries

“…At present, a series of "water in salt" electrolytes (WISEs) have been proposed by dissolving ultrahigh concentration of corrosive salt in water, which introduce crowded charge-carriers at the interface of host material to establish a redox process with higher reaction potential. [24][25][26][27] However, most of their charge-storage mechanisms still depend solely on cationic redox reactions, leading to unsatisfactory capacity, and even more frustrating is the use of high-viscosity and high-cost electrolytes. Therefore, tailoring a friendly and low-cost strategy with dilute neutral electrolytes to achieve viable high-voltage applications and high-capacity multi-electron transfer processes in TMCs cathode is highly desirable for the state-of-the-art AZBs but remains elusive.…”