A Reversible Anodizing Strategy in a Hybrid Electrolyte Zn-Ion Battery through Structural Modification of a Vanadium Sulfide Cathode

Abstract

Rechargeable aqueous Zn-ion batteries (ZiBs) have received significant attention owing to their low cost and environmental friendliness. The charge storage mechanism of ZiBs generally depends on the cationic redox conversion. The anodic redox conversion is still rare due to the lack of suitable cathode materials and electrolytes, which may impede the ZiB performance. The present investigation focuses on enhancing the ZiB performance through in situ involvement of disulfide redox chemistry from a patronite Mn-doped VS4 crystal in a 1 M Zn­(OTf)2 water/acetonitrile (ACN) hybrid electrolyte. Simultaneous involvement of cationic and anionic redox conversion during the charging/discharging process enhances the specific capacity as high as ∼547 mA h g–1 at 0.2 A g–1 current density. The water/ACN hybrid solvent effectively improves the working voltage and suppresses Zn dendrite formation, resulting in superior cycling performance. The conversion of the VS4 crystal phase and intercalation of H+/Zn2+ in the cathode have been investigated through ex situ X-ray diffraction, field emission scanning electron microscopy, X-ray photoelectron spectroscopy, and Raman studies.

Acid–Alkaline Electrolyte for the Development of High-Energy Density Zn-Ion Batteries through Structural Modification of MoS2 by MnO2

“…However, their practical application is constrained in terms of safety issues and high costs. − Recently, rechargeable zinc-ion batteries (ZiBs) have shown broad prospects for large-scale stationary applications, owing to the low cost, high ionic conductivity, low reduction potential (−0.76 V vs SHE), and environmental friendliness. − However, the aqueous ZiB exhibits a low working potential window due to the narrow water decomposition potential (1.23 V) at constant pH. There are several approaches available to improve the electrochemical stability window (ESW) of aqueous ZiBs, such as the use of “water-in-salt” electrolyte, polymer electrolyte, organic/aqueous electrolyte, and so forth. − …”

“…Recently, Frackowiak et al have introduced a dual pH aqueous electrolyte system (acidic and alkaline solution) considering the Nernst equation and Pourbaix diagram to overcome the thermodynamic limit of water decomposition potential. , According to the Nernst equation and Pourbaix diagram, the overpotentials of the hydrogen evolution reaction and oxygen evolution reaction (HER and OER) vary with the pH of the electrolyte. − In order to improve the ESW, the alkaline electrolyte is used in an anode compartment and the acid electrolyte in a cathode compartment. − On the contrary, the usage of organic co-solvents to aqueous electrolytes expands ESW for aqueous batteries and supercapacitors. Among the various available organic solvents, acetonitrile (ACN) is mostly used as an additive solvent owing to its wide ESW, low viscosity, high dielectric constant, and so forth. ,− A Zn­(ACN) 2 complex is formed in a Zn salt based on the ACN/water electrolyte, which promotes faster Zn 2+ ionic mobility by reducing the cation–anion interactions. ,− In addition, the Zn­(ACN) 2 complex formed a solid electrolyte interphase on the anode surface, which effectively prevents the water decomposition. ,− …”

“…The layered transition-meal chalcogenides like MoS 2 , VS 2 , VS 4 , TiS 2 , MnO 2 , and so forth are considered as promising cathode materials for ZiBs owing to their 2D ion diffusion channels. − ,,, Among the layered chalcogenides, MoS 2 is a promising material for Zn 2+ host cathode material. Generally, the storage capacity of the layered cathode depends on Zn 2+ ion insertion/extraction on the edge site.…”

Core–Shell-Structured Carbon Nanotube@VS4 Nanonecklaces as a High-Performance Cathode Material for Magnesium-Ion Batteries

“…Vanadium tetrasulfide (VS 4 ) has been proposed as a potential electrode material as a result of the large interlamellar spacing (5.83 Å) and weak coulombic attraction with guest Mg 2+ to enhance the ion diffusion. , Unfortunately, unoptimized VS 4 cannot display excellent electrochemical properties as a result of poor conductivity and serious polarization . To overcome these intrinsic problems of VS 4 , various strategies have been adopted, such as designing special nanoscale morphologies, doping metal ions, and combining with conductive materials . Among them, synthesizing VS 4 /carbonaceous materials is recognized as one of the most promising strategies on account of the favorable stability and electrochemical properties. , …”

Molecular Crowded ″Water-in-Salt″ Polymer Gel Electrolyte for an Ultra-stable Zn-Ion Battery

“…The ex situ Raman analysis of the Zn anode demonstrated the characteristic peaks located at 258, 440, 522,566, 766, and 1035 cm –1 (Figure S13a). The peaks at 258 and 522, 440 and 566, and 766 and 1035 cm –1 were attributed to the ZnF2, ZnO, and V–O and V–O–V modes, respectively. − The formation of ZnF 2 suggested a solid electrolyte interface on the anode surface by the reduction of (OTf) − anions under an applied potential. , The higher peak intensity of the ZnF 2 compared to the ZnO suggested that the solid electrolyte interface prevented the formation of Zn dendrites (Figure S13a). However, the peak intensity at 522 cm –1 for the Zn anode of the coin cell device was lesser compared to the solid-state device, confirming that the solid electrolyte interface formation was inhibited in the presence of free water molecules…”