Electrodeposited Zinc-Based Films as Anodes for Aqueous Zinc Batteries

Ultrathin Zincophilic Interphase Regulated Electric Double Layer Enabling Highly Stable Aqueous Zinc-Ion Batteries

The practical application of aqueous zinc-ion batteries for large-grid scale systems is still hindered by uncontrolled zinc dendrite and side reactions. Regulating the electrical double layer via the electrode/electrolyte interface layer is an effective strategy to improve the stability of Zn anodes. Herein, we report an ultrathin zincophilic ZnS layer as a model regulator. At a given cycling current, the cell with Zn@ZnS electrode displays a lower potential drop over the Helmholtz layer (stern layer) and a suppressed diffuse layer, indicating the regulated charge distribution and decreased electric double layer repulsion force. Boosted zinc adsorption sites are also expected as proved by the enhanced electric double-layer capacitance. Consequently, the symmetric cell with the ZnS protection layer can stably cycle for around 3,000 h at 1 mA cm-2 with a lower overpotential of 25 mV. When coupled with an I2/AC cathode, the cell demonstrates a high rate performance of 160 mAh g-1 at 0.1 A g-1 and long cycling stability of over 10,000 cycles at 10 A g-1. The Zn||MnO2 also sustains both high capacity and long cycling stability of 130 mAh g-1 after 1,200 cycles at 0.5 A g-1.

Enhancing the Performance of Reversible Zn Deposition by Ultrathin Polyelectrolyte Coatings

Modifying the surfaces of zinc and other metallic substrates is considered an effective strategy to enhance the reversibility of the zinc deposition and stripping processes. While a variety of surface modification strategies have been explored, their ability to be practically implemented is not always trivial due to the associated high costs and complexity of the proposed techniques. In this study, we showcase a straightforward method for preparing ultrathin polyelectrolyte coatings using polydiallyldimethylammonium chloride (PDDA) and polyethylenimine (PEI). The coatings, characterized by their electrostatic charge and hydrophobicity, suppress side reactions and even out the electrodeposition process across the substrate surface. The PDDA-coated anodes demonstrate significantly reduced voltage hysteresis, uniform zinc morphology, improved self-discharge rates, and an impressive Coulombic efficiency exceeding 99% over prolonged cycling. Our findings highlight the potential that such cost-effective and straightforward surface treatments could be widely applied in Zn metal-based batteries.

Revitalizing zinc-ion batteries with advanced zinc anode design

Rechargeable aqueous zinc-ion batteries (AZIBs) have attracted significant attention in large-scale energy storage systems due to their unique merits, such as intrinsic safety, low cost, and relatively high theoretical energy density. However, the dilemma of the uncontrollable Zn dendrites, severe hydrogen evolution reaction (HER), and side reactions that occur on the Zn anodes have hindered their commercialization. Herein, a state-of-the-art review of the rational design of highly reversible Zn anodes for high-performance AZIBs is provided. Firstly, the fundamental understanding of Zn deposition, with regard to the nucleation, electro-crystallization, and growth of the Zn nucleus is systematically clarified. Subsequently, a comprehensive survey of the critical factors influencing Zn plating together with the current main challenges is presented. Accordingly, the rational strategies emphasizing structural design, interface engineering, and electrolyte optimization have been summarized and analyzed in detail. Finally, future perspectives on the remaining challenges are recommended, and this review is expected to shed light on the future development of stable Zn anodes toward high-performance AZIBs.

Regulating Dendrite-Free Zn Deposition by a Self-Assembled OH-Terminated SiO2 Nanosphere Layer toward a Zn Metal Anode

Zn dendrite growth during repeated plating and stripping of a Zn metal anode often causes short-circuiting by puncturing the separator. Herein, we propose a separator modification strategy to regulate the Zn-ion flux and achieve uniform Zn deposition through the OH-terminated SiO₂ nanosphere coating. The interspaces between the uniform SiO₂ nanospheres construct a network of Zn-ion transport channels, and the negatively charged hydroxyl groups on the surface of SiO₂ nanospheres can electrostatically attract the Zn ions to direct the ion migration. The negative charges on SiO₂ nanospheres are retained at a higher pH, which enables the SiO₂ coating to consistently regulate the Zn-ion flux in the operating pH range of the Zn stripping/plating process. With a uniform Zn deposition guided by the SiO₂ coating, the dendrite formation is suppressed and the side reactions are alleviated. As a result, the Zn||Zn symmetric cell achieves a cyclic life of 1000 h at both 3 and 5 mA cm^-2. Meanwhile, the Zn||Cu asymmetric cell is able to maintain a Coulombic efficiency of 99.62% at 1 mA cm^-2 for 2000 cycles, which outperforms many previously reported strategies.

Tailoring the metal electrode morphology via electrochemical protocol optimization for long-lasting aqueous zinc batteries

Aqueous zinc metal batteries are a viable candidate for cost-effective energy storage. However, the cycle life of the cell is adversely affected by the morphological evolution of the metal electrode surface upon prolonged cycling. Here, we investigate different electrochemical protocols to favour the formation of stable zinc metal electrode surface morphologies. By coupling electrochemical and optical microscopy measurements, we demonstrate that an initial zinc deposition on the metal electrode allows homogeneous stripping and plating processes during prolonged cycling in symmetric Zn||Zn cell. Interestingly, when an initially plated zinc metal electrode is tested in combination with a manganese dioxide-based positive electrode and a two molar zinc sulfate aqueous electrolyte solution in coin cell configuration, a specific discharge capacity of about 90 mAh g⁻¹ can be delivered after 2000 cycles at around 5.6 mA cm⁻² and 25 °C.

Long-lasting zinc metal electrodes are crucial in developing commercial zinc-based batteries. Here, the authors investigate the different morphology evolution between the stripping and plating process and propose electrochemical protocols to prolong the lifespan of zinc anodes.

Boosted H+ Intercalation Enables Ultrahigh Rate Performance of the δ-MnO2 Cathode for Aqueous Zinc Batteries

H+ intercalation, as a critical battery chemistry, enables electrodes' high rate performance due to the fast diffusion kinetics of H+. In this work, more water molecules are introduced into δ-MnO2 by the protonation of δ-MnO2 with abundant oxygen vacancies. Benefiting from the structure with a close arrangement of water molecules in interlayers, the Grotthuss transport of proton is achieved in the energy storage of the δ-MnO2 cathode. As a result, the δ-MnO2 cathode exhibits an ultrahigh rate performance with a capacity of 368.1 mAh g-1 at 0.5 A g-1 and 83.4 mAh g-1 at 50 A g-1, which has a capacity retention of 73% after 1100 cycles at 10 A g-1. The study of the storage mechanism reveals that the Grotthuss intercalation of proton predominates the storage process, which empowers the cathode with high rate performance.

Zinc Anode for Mild Aqueous Zinc-Ion Batteries: Challenges, Strategies, and Perspectives

The rapid advance of mild aqueous zinc-ion batteries (ZIBs) is driving the development of the energy storage system market. But the thorny issues of Zn anodes, mainly including dendrite growth, hydrogen evolution, and corrosion, severely reduce the performance of ZIBs. To commercialize ZIBs, researchers must overcome formidable challenges. Research about mild aqueous ZIBs is still developing. Various technical and scientific obstacles to designing Zn anodes with high stripping efficiency and long cycling life have not been resolved. Moreover, the performance of Zn anodes is a complex scientific issue determined by various parameters, most of which are often ignored, failing to achieve the maximum performance of the cell. This review proposes a comprehensive overview of existing Zn anode issues and the corresponding strategies, frontiers, and development trends to deeply comprehend the essence and inner connection of degradation mechanism and performance. First, the formation mechanism of dendrite growth, hydrogen evolution, corrosion, and their influence on the anode are analyzed. Furthermore, various strategies for constructing stable Zn anodes are summarized and discussed in detail from multiple perspectives. These strategies are mainly divided into interface modification, structural anode, alloying anode, intercalation anode, liquid electrolyte, non-liquid electrolyte, separator design, and other strategies. Finally, research directions and prospects are put forward for Zn anodes. This contribution highlights the latest developments and provides new insights into the advanced Zn anode for future research.

Dual Porous 3D Zinc Anodes toward Dendrite-Free and Long Cycle Life Zinc-Ion Batteries

Rechargeable aqueous zinc-ion batteries (ZIBs) have been proven to be an alternative energy storage system because of their high safety, low cost, and eco-friendliness. However, the poor stability of metallic Zn anodes suffering from uncontrolled dendrite formation and electrochemical corrosion has brought troublesome hindrances for their practical application. In this work, we report a dual porous Zn-3D@600 anode prepared by coating a Zn@C protective layer on a 3D zinc skeleton. The Zn-3D@600 anode exhibits a highly stable and low polarization voltage during the Zn plating/stripping process and possesses a smooth and dendrite-free interface after long-term cycling. Moreover, the assembled Zn-3D@600 cell shows excellent cycle stability and superlative rate performance, delivering a discharge capacity of 198.8 mAh g^-1 after 1000 cycles at 1 A g^-1. Such excellent electrochemical performance can be credited to the Zn@C protective layer regulating uniform Zn nucleation and the 3D zinc skeleton accommodating Zn deposition at a high current density.

Nanofiber Composite for Improved Water Retention and Dendrites Suppression in Flexible Zinc-Air Batteries

Water loss of the gel polymer electrolytes (GPEs) and dendrites growth on Zn anode are overriding obstacles to applying flexible zinc-air batteries (ZABs) for wearable electronic devices. Nearly all previous efforts aim at developing novel GPEs with enhanced water retention and therefore elongate their lifespan. Herein, a facile interface engineering strategy is proposed to retard the water loss of GPE from the half-open structured air cathode. In detail, the poly(ethylene vinyl acetate)/carbon powder (PEVA-C) nanofiber composite interface layer with features of hydrophobicity, high conductivity, air permeability, and flexibility are prepared on the carbon cloth and set up between the GPE and electrode. The as-assembled ZAB with simple alkaline PVA GPE exhibits an impressive cycle life of 230 h, which outperforms ZAB without the PEVA-C nanofibers interface layer by 14 times. Additionally, the growth of Zn dendrites can be suppressed due to the tardy water loss of GPE.

Ultrasound Supported Galvanostatic Deposition of Zn Coatings Reinforced with Nano-, Submicro-, and Micro-SiC Particles-Weak Acidic Chloride Baths

In this paper, we present results concerning the electrochemical deposition of Zn-SiC composite coatings reinforced with nano-, submicro-, and microparticles. The influence of current density, particle size, and ultrasound on functional parameters which are especially important from a practical point of view (i.e., concentration of particles in coatings, current efficiency, morphology, reflectivity, roughness, hardness, and corrosion resistance) are investigated and discussed. Coatings were deposited from commercial, chloride-based electrolytes dedicated for the deposition of Zn coatings in a weakly acidic environment. Electrodeposited composites contained up to 1.58, 4.08, and 1.15 wt. % of SiC for coatings reinforced with nano, submicro, and micrometric particles, respectively. The process proceeded with relatively high efficiency, exceeding 80% in almost all cases. The results indicate that ultrasounds strongly increase Faradaic efficiency and affect the kinetics of electrode processes and the properties of synthesized coatings. Moreover, the obtained results show that it is possible to synthesize composite coatings with slightly higher mechanical properties while retaining corrosion resistance compared to metallic Zn coatings.