Direct Detection and Visualization of the H⁺ Reaction Process in a VO₂ Cathode for Aqueous Zinc-Ion Batteries

Abstract

Because they are safer and less costly than state-of-the-art Li-ion batteries, aqueous zinc-ion batteries (AZIBs) have been attracting more attention in stationary energy storage and industrial energy storage. However, the electrochemical reaction of H+ in all of the cathode materials of AZIBs has been puzzling until now. Herein, highly oriented VO2 monocrystals grown on a Ti current collector (VO2–Ti) were rationally designed as the research model, and such a well-aligned VO2 cathode also displayed excellent zinc-ion storage capability (e.g., a reversible capacity of 148.4 mAh/g at a current density of 2 A/g). To visualize the H+ reaction process, we used time-of-flight secondary-ion mass spectrometry. With the benefit of such a binder-free and conductor-free electrode design, a clear and intuitive reaction of H+ in a VO2 cathode is obtained, which is quite significant for unraveling the accurate reaction mechanism of VO2 in AZIBs.

Understanding H2 Evolution Electrochemistry to Minimize Solvated Water Impact on Zinc‐Anode Performance

“…[8,9] Obstacles to the practical use of zincmetal anodes originate from a relatively negative reduction potential for Zn of −0.762 V versus standard hydrogen electrode (SHE), leading to H 2 evolution and changing the local pH to strong alkaline. [10][11][12] The alkaline environment corrodes the Zn anode via side reactions, leading to poor electrochemical performance including, low Coulombic efficiency (CE) and rapid capacity decay. Additionally, an obstacle is the formation of Zn dendrite and the resulting cell short-circuit.…”

Current Challenges and Advanced Design Strategy of Vanadium Dioxide Cathode for Low‐Cost Aqueous Zinc Metal Battery

“…However, the proton also has been found to be inserted into the VO 2 -based cathode material. [14] In this case, the H þ ions with a smaller radius and one positive charge than the hydrated zinc ions would greatly enhance ion migration kinetics and maintain structural stability well by reducing the electrostatic force with the host material (Figure 2b). Li et al demonstrated one new reaction mechanism that proton originating from the H 2 O molecules can insert into VO 2 and the Zn 2þ ion reacted with electrolyte to deposit the Zn 4 (OH) 6 SO 4 •5H 2 O at the VO 2 surface to store Zn 2þ ion during the discharge process (Equation ( 4)-( 8)) under the combination of theoretical calculation simulations and in/ex situ characterization (such as XRD, X-ray photoelectron spectroscopy (XPS), and neutron activation analysis (NAA)).…”

KOH-Induced Oxygen-Deficient VO2 for High-Rate Aqueous Zn-Ion Batteries

“…1−3 Aqueous Zn-ion batteries (AZIBs) have gradually received increasing worldwide attention due to straightforward processing, high safety, and environmental friendliness. 4 At present, a number of cathode materials for AZIBs have been developed, including manganese-based compounds, vanadiumbased compounds, Prussian blue analogous, and some other materials. 5 Among various cathode materials, vanadium-based materials have multivalence nature and superior stability of layered structure, presenting a great potential as cathode materials for developing high-performance AZIBs.…”

“…In recent years, electronic products have been integrated into most people’s everyday lives, so the development of renewable and sustainable energy storage systems is necessary. − Aqueous Zn-ion batteries (AZIBs) have gradually received increasing worldwide attention due to straightforward processing, high safety, and environmental friendliness . At present, a number of cathode materials for AZIBs have been developed, including manganese-based compounds, vanadium-based compounds, Prussian blue analogous, and some other materials .…”