MoS2 -Mediated Epitaxial Plating of Zn Metal Anodes

Organic Cations Texture Zinc Metal Anodes for Deep Cycling Aqueous Zinc Batteries

Manipulating the crystallographic orientation of zinc (Zn) metal to expose more (002) planes is promising to stabilize Zn anodes in aqueous electrolytes. However, there remain challenges involving the non-epitaxial electrodeposition of highly (002) textured Zn metal and the maintenance of (002) texture under deep cycling conditions. Herein, a novel organic imidazolium cations-assisted non-epitaxial electrodeposition strategy to texture electrodeposited Zn metals is developed. Taking the 1-butyl-3-methylimidazolium cation (Bmim+) as a paradigm additive, the as-prepared Zn film ((002)-Zn) manifests a compact structure and a highly (002) texture without containing (100) signal. Mechanistic studies reveal that Bmim+ featuring oriented adsorption on the Zn-(002) plane can reduce the growth rate of (002) plane to render the final exposure of (002) texture, and homogenize Zn nucleation and suppress H2 evolution to enable the compact electrodeposition. In addition, the formulated Bmim+-containing ZnSO4 electrolyte effectively sustains the (002) texture even under deep cycling conditions. Consequently, the combination of (002) texture and Bmim+-containing electrolyte endows the (002)-Zn electrode with superior cycling stability over 350 h under 20 mAh cm-2 with 72.6% depth-of-discharge, and assures the stable operation of full Zn batteries with both coin-type and pouch-type configurations, significantly outperforming the (002)-Zn and commercial Zn-based batteries in Bmim+-free electrolytes.

Ultra-High Proportion of Grain Boundaries in Zinc Metal Anode Spontaneously Inhibiting Dendrites Growth

Aqueous Zn-ion batteries are an attractive electrochemical energy storage solution for their budget and safe properties. However, dendrites and uncontrolled side reactions in anodes detract the cycle life and energy density of the batteries. Grain boundaries in metals are generally considered as the source of the above problems but we present a diverse result. This study introduces an ultra-high proportion of grain boundaries on zinc electrodes through femtosecond laser bombardment to enhance stability of zinc metal/electrolyte interface. The ultra-high proportion of grain boundaries promotes the homogenization of zinc growth potential, to achieve uniform nucleation and growth, thereby suppressing dendrite formation. Additionally, the abundant active sites mitigate the side reactions during the electrochemical process. Consequently, the 15 μm Fs-Zn||MnO2 pouch cell achieves an energy density of 249.4 Wh kg-1 and operates for over 60 cycles at a depth-of-discharge of 23 %. The recognition of the favorable influence exerted by UP-GBs paves a new way for other metal batteries.

Accelerated Confined Mass Transfer of MoS2 1D Nanotube in Photo-Assisted Metal-Air Batteries

Applying solar energy into energy storage battery systems is challenging in achieving green and sustainable development, however, the efficient progress of photo-assisted metal-air batteries is restricted by the rapid recombination of photogenerated electrons and holes upon the photocathode. Herein, a 1D-ordered MoS2 nanotube (MoS2-ONT) with confined mass transfer can be used to extend the lifetime of photogenerated carriers, which is capable of overcoming the challenge of rapid recombination of electron and holes. The tubular confined space cannot only promote the orderly separation and migration of charge carriers but also realize the accumulation of charge and the rapid activation of oxygen molecules. The concave surface of MoS2-ONT can improve the carrier separation ability and prolong the carrier lifetime. Meanwhile, the ordered tubular confined space can effectively realize the rapid transfer of charge, ion, and oxygen. Under light irradiation, a fast oxygen reduction reaction kinetics of 70 mW cm-2 for photo-assisted Zn-air battery is achieved, which is the highest value reported for photo-assisted Zn-air batteries. Significantly, the photo-assisted Li-O2 battery based on MoS2-ONT also shows superior rate capability and other exciting battery performance. This work shows the universality of the confined carrier separation strategy in photo-assisted metal-air batteries.

Construct Robust Epitaxial Growth of (101) Textured Zinc Metal Anode for Long Life and High Capacity in Mild Aqueous Zinc-Ion Batteries

Aqueous zinc-metal batteries are considered to have the potential for energy storage due to their high safety and low cost. However, the practical applications of zinc batteries are limited by dendrite growth and side reactions. Epitaxial growth is considered an effective method for stabilizing Zn anode, especially for manipulating the (002) plane of deposited zinc. However, (002) texture zinc is difficult to achieve stable cycle at high capacity due to its large lattice distortion and uneven electric field distribution. Here, a novel zinc anode with highly (101) texture (denoted as (101)-Zn) is constructed. Due to unique directional guidance and strong bonding effect, (101)-Zn can achieve dense vertical electroepitaxy in near-neutral electrolytes. In addition, the low grain boundary area inhibits the occurrence of side reactions. The resultant (101)-Zn symmetric cells exhibit excellent stability over 5300 h (4 mA cm-2 for 2 mAh cm-2 ) and 330 h (15 mA cm-2 for 10 mAh cm-2 ). Meanwhile, the cycle life of Zn//MnO2 full cell is meaningfully improved over 1000 cycles.

An extended substrate screening strategy enabling a low lattice mismatch for highly reversible zinc anodes

Aqueous zinc batteries possess intrinsic safety and cost-effectiveness, but dendrite growth and side reactions of zinc anodes hinder their practical application. Here, we propose the extended substrate screening strategy for stabilizing zinc anodes and verify its availability (dsubstrate: dZn(002) = 1: 1→dsubstrate: dZn(002)=n:1, n = 1, 2). From a series of calculated phyllosilicates satisfying dsubstrate ≈ 2dZn(002), we select vermiculite, which has the lowest lattice mismatch (0.38%) reported so far, as the model to confirm the effectiveness of "2dZn(002)" substrates for zinc anodes protection. Then, we develop a monolayer porous vermiculite through a large-scale and green preparation as a functional coating for zinc electrodes. Unique "planting Zn(002) seeds" mechanism for "2dZn(002)" substrates is revealed to induce the oriented growth of zinc deposits. Additionally, the coating effectively inhibits side reactions and promotes zinc ion transport. Consequently, the modified symmetric cells operate stably for over 300 h at a high current density of 50 mA cm-2. This work extends the substrate screening strategy and advances the understanding of zinc nucleation mechanism, paving the way for realizing high-rate and stable zinc-metal batteries.

Peptide Gel Electrolytes for Stabilized Zn Metal Anodes

The rechargeable aqueous Zn ion battery (AZIB) is considered a promising candidate for future energy storage applications due to its intrinsic safety features and low cost. However, Zn dendrites and side reactions (e.g., corrosion, hydrogen evolution reaction, and inactive side product (Zn hydroxide sulfate) formation) at the Zn metal anode have been serious obstacles to realizing a satisfactory AZIB performance. The application of gel electrolytes is a common strategy for suppressing these problems, but the normally used highly cross-linked polymer matrix (e.g., polyacrylamide (PAM)) brings additional difficulties for battery assembly and recycling. Herein, we have developed a gel electrolyte for Zn metal anode stabilization, where a peptide matrix, a highly biocompatible material, is used for gel construction. Various experiments and simulations elucidate the sulfate anion-assisted self-assembly gel formation and its effect in stabilizing Zn metal anodes. Unlike polymer gel electrolytes, the peptide gel electrolyte can reversibly transform between gel and liquid states, thus facilitating the gel-involved battery assembly and recycling. Furthermore, the peptide gel electrolyte provides fast Zn ion diffusion (comparable to conventional liquid electrolyte) while suppressing side reactions and dendrite growth, thus achieving highly stable Zn metal anodes as validated in various cell configurations. We believe that our concept of gel electrolyte design will inspire more future directions for Zn metal anode protection based on gel electrolyte design.

MoSe2 hollow nanospheres with expanded selenide interlayers for high-performance aqueous zinc-ion batteries

Transition metal dichalcogenides (TMDs) as materials for aqueous zinc-ion batteries (ZIBs) have received a lot of interest because of their large theoretical capacity and unique layered structure. However, the sluggish kinetics and inferior cyclic stability limit the usefulness of ZIBs. In the present investigation, the interlayer spacing enlarged MoSe2 hollow nanospheres comprised of nanosheets with ultrathin shells have been successfully synthesized through a combined strategy of template assistance and anion-exchange reaction. The hierarchical ultrathin nanosheets and hollow structure effectively suppress the agglomeration of pure nanosheets and ameliorate volume fluctuations induced by ion migration during (dis)charging/charging. The interlayer expansion provides good channels for the transport of Zn2+ ions and speeds up the insertion/extraction of Zn2+. In addition, in-situ carbon modification can significantly improve electronic conductivity. Therefore, the electrode prepared from MoSe2 hollow nanospheres with enlarged interlayer spacing not only exhibits outstanding cycle stability (capacity retention of 94.5% after 1600 cycles) but also exhibits high-rate capability (266.1 mA h g-1 at 0.1 A g-1 and 203.6 mA h g-1 at 3 A g-1). This work could provide new insights into the design of cathode using TMDs of hollow structure for Zn2+ storage.

Two-dimensional materials for high density, safe and robust metal anodes batteries

With a high specific capacity and low electrochemical potentials, metal anode batteries that use lithium, sodium and zinc metal anodes, have gained great research interest in recent years, as a potential candidate for high-energy-density storage systems. However, the uncontainable dendrite growth during the repeated charging process, deteriorates the battery performance, reduces the battery life and more importantly, raises safety concerns. With their unique properties, two-dimensional (2D) materials, can be used to modify various components in metal batteries, eventually mitigating the dendrite growth, enhancing the cycling stability and rate capability, thus leading to safe and robust metal anodes. In this paper, we review the recent advances of 2D materials and summarize current research progress of using 2D materials in the applications of (i) anode design, (ii) separator engineering, and (iii) electrolyte modifications by guiding metal ion nucleation, increasing ion conductivity, homogenizing the electric field and ion flux, and enhancing the mechanical strength for safe metal anodes. The 2D material modifications provide the ultimate solution for obtaining dendrite-free metal anodes, realizes the high energy storage application, and indicates the importance of 2D materials development. Finally, in-depth understandings of subsequent metal growth are lacking due to research limitations, while more advanced characterizations are welcome for investigating the metal deposition mechanism. The more facile and simplified preparation of 2D materials possess great prospects in high energy density metal anode batteries, and thus fulfils the development of EVs.

Rationalized Electroepitaxy toward Scalable Single-Crystal Zn Anodes

Electroepitaxy is recognized as an effective approach to prepare metal electrodes with nearly complete reversibility. Nevertheless, large-scale manipulation is still not attainable owing to complicated interfacial chemistry. Here, the feasibility of extending Zn electroepitaxy toward the bulk phase over a mass-produced mono-oriented Cu(111) foil is demonstrated. Interfacial Cu-Zn alloy and turbulent electroosmosis are circumvented by adopting a potentiostatic electrodeposition protocol. The as-prepared Zn single-crystalline anode enables stable cycling of symmetric cells at a stringent current density of 50.0 mA cm^-2 . The assembled full cell further sustaines a capacity retention of 95.7% at 5.0 A g^-1 for 1500 cycles, accompanied by a controllably low N/P ratio of 7.5. In addition to Zn, Ni electroepitaxy can be realized by using the same approach. This study may inspire rational exploration of the design of high-end metal electrodes.

2D Materials Boost Advanced Zn Anodes: Principles, Advances, and Challenges

Aqueous zinc-ion battery (ZIB) featuring with high safety, low cost, environmentally friendly, and high energy density is one of the most promising systems for large-scale energy storage application. Despite extensive research progress made in developing high-performance cathodes, the Zn anode issues, such as Zn dendrites, corrosion, and hydrogen evolution, have been observed to shorten ZIB's lifespan seriously, thus restricting their practical application. Engineering advanced Zn anodes based on two-dimensional (2D) materials are widely investigated to address these issues. With atomic thickness, 2D materials possess ultrahigh specific surface area, much exposed active sites, superior mechanical strength and flexibility, and unique electrical properties, which confirm to be a promising alternative anode material for ZIBs. This review aims to boost rational design strategies of 2D materials for practical application of ZIB by combining the fundamental principle and research progress. Firstly, the fundamental principles of 2D materials against the drawbacks of Zn anode are introduced. Then, the designed strategies of several typical 2D materials for stable Zn anodes are comprehensively summarized. Finally, perspectives on the future development of advanced Zn anodes by taking advantage of these unique properties of 2D materials are proposed.