Bidirectional Interface Protection of a Concentrated Electrolyte, Enabling High-Voltage and Long-Life Aqueous Zn Hybrid-Ion Batteries

Abstract

Prussian blue analogues (PBAs) as a promising high-voltage cathode material for aqueous zinc-ion batteries (ZIBs) are usually subjected to an ephemeral lifespan and low Coulombic efficiency due to the irreversible phase change and high Zn2+ insertion potential. Besides, Zn dendrites, H2 evolution reaction, and corrosion derived from a Zn anode interface remain huge challenges. Given this, a highly stable zinc hexacyanoferrate (KZnHCF) cathode together with a mixed concentrated electrolyte is prepared to realize a high-voltage and long-life aqueous ZIB, in which the mixed concentrated electrolyte consisting of 30 m KFSI + 1 m Zn­(CF3SO3)2 possesses a unique Zn2+ solvation sheath (Zn­(CF3SO3)0.3(FSI)3.1(H2O)2.6) that can not only stabilize the cathode interface and improve the Coulombic efficiency but also fundamentally solve the Zn anode interface issues. As a result, the aqueous KZnHCF/Zn battery achieves an ultralong life over 3000 cycles without any capacity decay even under a high discharge voltage of 1.78 V (vs Zn2+/Zn). Such extraordinary performance represents significant progress in aqueous PBA-based ZIBs. This work shares guidance to improve the performance of aqueous ZIBs through optimizing the electrolyte in tuning the stable operation of the cathode and the zinc anode.

Fabrication of an Energy-Dense, Binder-Free Zn//V5O12·6H2O Solid-State In-Plane Flexible Battery via a Rapid and Scalable Approach

“…The capacity loss at low current may be attributed to the partially irreversible (de)­intercalation of the Zn­(H 2 O) 6 2+ , whereas a structural dissolution of vanadium oxide at the cathode/electrolyte interface may also cause a fast capacity loss. The coordinated water molecules [Zn­(H 2 O) 6 2+ ] accelerate the vanadium dissolution due to the increase in the localized coordinated water concentration or release of electrochemically active water molecules from Zn­(H 2 O) 6+ during the desolvation process. , The structural breakdown of vanadium oxide is also accelerated by the weakening V–O bond due to the hydrogen-bonding ability of the coordinated water molecules with the lattice O 2– . To further understand the vanadium oxide dissolution, the electrolyte was collected from a cycled cell (10 cycles at 0.1 A/g current), which showed a faint green brown color, and was analyzed by UV–visible spectroscopy (Figure S5).…”

Constructing Acrylic-Bonded Stationary Phase as an Artificial SEI for Highly Stable Zn Metal Anodes

“…Aqueous zinc-ion batteries (AZIBs) have long been considered as a promising alternative to flammable lithium-ion batteries due to their unique properties such as high theoretical capacity (820 mAh g –1 ), high safety, low cost, and environmental benignity. − However, the commercialization of AZIBs still faces many challenges, including detrimental Zn dendrites, hydrogen evolution issues, corrosion, and interfacial side reactions due to the use of metallic Zn anodes, which severely restricts the large-scale application of AZIBs. − Therefore, multiple strategies have been explored to settle the challenges mentioned above. Those attempts could be cataloged by two types: (1) indirect electrolyte modification strategy, such as introducing organic/inorganic additives (DMSO, ZnF 2 , and glucose additives), adopting gel electrolytes (PAM, , PVA, and gelatin gel electrolytes), and developing superconcentrated electrolytes − to functionalize and substitute existing aqueous electrolytes and (2) direct design or modification of the Zn anodes, for example, some researchers focus their attention on the geometry and structure of Zn electrodes, which is another pivotal factor that affects homogeneous zinc-ion deposition. As newly reported, a flexible ultrathin and ultralight Zn micromesh with regularly aligned microholes is certified to induce spatial-selection deposition of a Zn micromesh .…”

A Near 0 V and Low-Strain Intercalative Anode for Aqueous Zinc-Ion Batteries

“…Although the excess Zn can compensate for zinc loss resulting from zinc dendrites, corrosion, dissolution, and byproducts, it also greatly reduces the energy density of the AZIB system. As is well-known, Zn foil will inevitably react slowly with the electrolyte, even if it is just immersed in the solution, , leading to irreversible zinc loss and the production of parasitic gases. The extremely low utility ratio of Zn, the water of cell loss, and undesirable cell swelling bring great challenges to the commercialization of AZIBs.…”

“…To further evaluate the electrochemical properties of the TOP anode, we fabricated a “rocking-chair” type full AZIB with zinc hexacyanoferrate (KZnHCF) as the positive electrode, TOP as the negative electrode, and 3 M Zn­(CF 3 SO 3 ) 2 PAM gel as the electrolyte, as illustrated in Figure a. The KZnHCF cathode possesses a robust framework with large ion channels to accommodate large-sized Zn 2+ , and its synthesis and physical and electrochemical characteristics were elaborated in our previous work . Additionally provided are the XRD results, SEM images, and electrochemical performance of the as-synthesized KZnHCF electrodes (Figure S16).…”

“…The KZnHCF cathode possesses a robust framework with large ion channels to accommodate largesized Zn 2+ , and its synthesis and physical and electrochemical characteristics were elaborated in our previous work. 30 Additionally provided are the XRD results, SEM images, and electrochemical performance of the as-synthesized KZnHCF electrodes (Figure S16). The KZnHCF cathode exhibits a high working voltage of 1.75 V and a discharge capacity of 68 mAh g −1 .…”