Synergistically Stabilizing Zinc Anodes by Molybdenum Dioxide Coating and Tween 80 Electrolyte Additive for High-Performance Aqueous Zinc-Ion Batteries

Overcoming the Challenges in Aqueous Zinc Metal Batteries: Underlying Issues and Mitigation Strategies

The increasing demand for green and clean energy harvesting and their judicious storage call for pursuing new energy storage technologies. Building better batteries has drawn significant attention to fulfilling the energy demand by delivering the stored electrical energy at the anticipated time and minimal cost. Li-ion batteries play a crucial role in transitioning to a sustainable energy landscape. However, their safety and environmental issues are of concern. Zn-based batteries provide more sustainable solutions due to their low cost, enhanced safety, and environmental benignity. Still, poor thermodynamic reversibility and stability of Zn anode in the aqueous electrolytes prevent its practical application. Significant efforts such as Zn anode surface engineering and electrolyte and/or interface modification alleviate these issues. However, in-depth studies of the root causes associated with the reversibility and stability issues of Zn electrodes are still deficient. Hence, this review focuses on the underlying causes of the major issues (dendrite, hydrogen evolution, corrosion, and passivation) associated with Zn anodes. Furthermore, we have summarized the technological advances that have been made to address these issues. Finally, some promising future directions and perspectives are provided for a further in-depth understanding of thermodynamic irreversibility and to improve the overall performance of the Zn anode.

Multiple Regulation of Electrolyte with Trace Amounts of Sodium Dehydroacetate Additives Enables High-Performance Aqueous Zinc-Ion Batteries

Rechargeable aqueous zinc-ion batteries (AZIBs) draw much attention for low cost and high safety. However, hydrogen evolution reaction (HER) and uneven Zn2+ deposition shorten lifespan, hampering commercial use. In this study, sodium dehydroacetate (SD) containing carbonyl and keto-carbonyl is introduced as multifunctional electrolyte additives, which effectively modifies the solvent shell structure, achieving a Zn2+ transference number of up to 0.72. Acting as a hydrogen bond acceptor, SD disrupts the water network structure, thereby increasing the HER overpotential by 22 mV and the corrosion potential by 9 mV. The polar functional groups in SD can reversibly capture H⁺ ions and dynamically neutralize OH⁻ ions, maintaining interfacial pH balance on the zinc anode and suppressing HER. Notably, SD not only alters the electrolyte's kinetic but also induces uniform Zn2+ deposition along the (002) plane, inhibiting dendrite growth and minimizing side reactions. This phenomenon is demonstrated in both symmetric and full-cell configurations. The Zn//Zn symmetric cell achieves an ultra-long cycling lifespan of 2800 hours at 5 mA cm⁻2, and the Zn//VO2 full battery maintains a capacity retention rate of 73.09% after 2000 cycles with a high average coulombic efficiency of 99.98%, underscoring the effectiveness of this electrolyte additive in enhancing battery performance.

Porphyrinic N4 channels of zinc ions for the electrochemical reversibility of zinc plating/stripping

A Zn2+-coordinated porphyrinic artificial solid-electrolyte interphase (αSEI) layer, named [Zn]PP-4COO-(Zn), was developed to improve the reversibility of zinc metal plating/stripping in aqueous zinc-ion batteries (ZIBs). Inspired by nitrogen-terminating sites of biological molecules coordinating and transporting zinc in zinc metabolic processes, the αSEI layer was designed with zinc ions connecting porphyrinic building blocks to form two-dimensional clathrate sheets and stacking xy-plane sheets along the z-axis to allow N4 cages to align and form porphyrinic N4 channels for zinc transport. The [Zn]PP-4COO-(Zn) αSEI layer was Zn2+-conductive and structurally durable during repeated stripping/plating. Zinc ions traveled through the porphyrinic αSEI layer along the N4 channels via (1) desolvation, (2) coordination to two nitrogens of the first clathrate sheet, (3) passing through distorted N4 cages, (4) moving to inter-plane N4 (two nitrogens from the first sheet and two nitrogens from the second sheet), (5) consecutive transport to next inter-plane N4, and (6) metal nucleation on zinc metal foil during plating. Zinc ions coming from electrolytes along the N4 channels were plated preferentially along the (002) plane, ensuring the non-dendritic growth of zinc metal for supporting plating/stripping reversibility to guarantee cycling durability. The porphyrinic N4 zinc-ion channels kept the zinc symmetric cells healthy even after 1500 times repeated plating/stripping during 3000 h operation.

Ferroelectric Interfaces for Dendrite Prevention in Zinc-Ion Batteries

Aqueous rechargeable zinc-ion batteries (ZIBs) are increasingly recognized as promising energy storage systems for mini-grid and mini-off-grid applications due to their advantageous characteristics such as high safety, affordability, and considerable theoretical capacity. However, the long-term cycling performance of ZIBs is hampered by challenges including the uncontrolled dendrite formation, the passivation, and the occurrence of the hydrogen evolution reaction (HER) on the Zn anode. In this study, enhancing ZIB performance by implementing oxide material coatings on Zn metal, serving as a physical barrier at the electrode-electrolyte interfaces to mitigate dendrite growth and suppress the HER is concentrated. Specifically, the mechanisms through which the n-type semiconductor TiO2 coated Zn anode establishes ohmic contact with Zn, and the high-dielectric BaTiO3 (BTO) coated Zn anode fosters Maxwell-Wagner polarization with ferroelectric properties, significantly inhibiting dendrite growth and side reactions, thereby resulting in a highly stable Zn anode for efficient aqueous ZIBs is explored. This advanced BTO/Zn electrode demonstrates an extended lifespan of over 700 h compared to bare Zn and TiO2/Zn anodes. Additionally, full-cell aqueous ZIBs incorporating BTO/Zn//VO2 (B) batteries exhibit superior rate capabilities, high capacity, and sustained cycle life.

Rational Design of Ni-Doped V2O5@3D Ni Core/Shell Composites for High-Voltage and High-Rate Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (ZIBs) have significant potential for large energy storage systems because of their high energy density, cost-effectiveness and environmental friendliness. However, the limited voltage window, poor reaction kinetics and structural instability of cathode materials are current bottlenecks which contain the further development of ZIBs. In this work, we rationally design a Ni-doped V2O5@3D Ni core/shell composite on a carbon cloth electrode (Ni-V2O5@3D Ni@CC) by growing Ni-V2O5 on free-standing 3D Ni metal nanonets for high-voltage and high-capacity ZIBs. Impressively, embedded Ni doping increases the interlayer spacing of V2O5, extending the working voltage and improving the zinc-ion (Zn302+) reaction kinetics of the cathode materials; at the same time, the 3D structure, with its high specific surface area and superior electronic conductivity, aids in fast Zn302+ transport. Consequently, the as-designed Ni-V2O5@3D Ni@CC cathodes can operate within a wide voltage window from 0.3 to 1.8 V vs. Zn30/Zn302+ and deliver a high capacity of 270 mAh g-1 (~1050 mAh cm-3) at a high current density of 0.8 A g-1. In addition, reversible Zn2+ (de)incorporation reaction mechanisms in the Ni-V2O5@3D Ni@CC cathodes are investigated through multiple characterization methods (SEM, TEM, XRD, XPS, etc.). As a result, we achieved significant progress toward practical applications of ZIBs.