Highly Strengthened and Toughened Zn-Li-Mn Alloys as Long-Cycling Life and Dendrite-Free Zn Anode for Aqueous Zinc-Ion Batteries

Achieving stable Zn metal anode via a hydrophobic and Zn2+-conductive amorphous carbon interface

High security and low cost enable aqueous zinc ion batteries (AZIBs) with huge application potential in large-scale energy storage. Nevertheless, the loathsome dendrite and side reactions of Zn anode are harmful to the cycling lifespan of AZIBs. Here, a new type of thin amorphous carbon (AC) interface layer (∼100 nm in thickness) is in-situ constructed on the Zn foil (Zn@AC) via a facile low-temperature chemical vapor deposition (LTCVD) method, which owns a hydrophobic peculiarity and a high Zn2+ transference rate. Moreover, this AC coating can homogenize the surface electric field and Zn2+ flux to realize the uniform deposition of Zn. Consequently, dendrite growth and side reactions are concurrently mitigated. Symmetrical cell achieves a dendrite-free Zn plating/stripping over 500 h with a low overpotential of 31 mV at 1 mA cm-2/1 mAh cm-2. Of note, the full cell with a MnO2/CNT cathode harvests a capacity retention of 70.0 % after 550 cycles at 1 A/g. In addition, the assembled flexible quasi-solid-state AZIBs display a stable electrochemical performance under deformation conditions and maintain a capacity of 76.5 mAh/g at 5 A/g after 300 cycles. This innovative amorphous carbon layer is expected to provide a new insight into stabilizing Zn anode.

Fundamental Understanding of Hydrogen Evolution Reaction on Zinc Anode Surface: A First-Principles Study

Hydrogen evolution reaction (HER) has become a key factor affecting the cycling stability of aqueous Zn-ion batteries, while the corresponding fundamental issues involving HER are still unclear. Herein, the reaction mechanisms of HER on various crystalline surfaces have been investigated by first-principle calculations based on density functional theory. It is found that the Volmer step is the rate-limiting step of HER on the Zn (002) and (100) surfaces, while, the reaction rates of HER on the Zn (101), (102) and (103) surfaces are determined by the Tafel step. Moreover, the correlation between HER activity and the generalized coordination number ([Formula: see text]) of Zn at the surfaces has been revealed. The relatively weaker HER activity on Zn (002) surface can be attributed to the higher [Formula: see text] of surface Zn atom. The atomically uneven Zn (002) surface shows significantly higher HER activity than the flat Zn (002) surface as the [Formula: see text] of the surface Zn atom is lowered. The [Formula: see text] of surface Zn atom is proposed as a key descriptor of HER activity. Tuning the [Formula: see text] of surface Zn atom would be a vital strategy to inhibit HER on the Zn anode surface based on the presented theoretical studies. Furthermore, this work provides a theoretical basis for the in-depth understanding of HER on the Zn surface.

Challenges and Strategies in the Development of Zinc-Ion Batteries

Although promising, the practical use of zinc-ion batteries (ZIBs) remains plagued with uncontrollable dendrite growth, parasitic side reactions, and the high intercalation energy of divalent Zn²⁺ ions. Hence, much work has been conducted to alleviate these issues to maximize the energy density and cyclic life of the cell. In this holistic review, the mechanisms and rationale for the stated challenges shall be summarized, followed by the corresponding strategies employed to mitigate them. Thereafter, a perspective on present research and the outlook of ZIBs would be put forth in hopes to enhance their electrochemical properties in a multipronged approach.

Progress and Prospect of Zn Anode Modification in Aqueous Zinc-Ion Batteries: Experimental and Theoretical Aspects

Aqueous zinc-ion batteries (AZIBs), the favorite of next-generation energy storage devices, are popular among researchers owing to their environmental friendliness, low cost, and safety. However, AZIBs still face problems of low cathode capacity, fast attenuation, slow ion migration rate, and irregular dendrite growth on anodes. In recent years, many researchers have focused on Zn anode modification to restrain dendrite growth. This review introduces the energy storage mechanism and current challenges of AZIBs, and then some modifying strategies for zinc anodes are elucidated from the perspectives of experiments and theoretical calculations. From the experimental point of view, the modification strategy is mainly to construct a dense artificial interface layer or porous framework on the anode surface, with some research teams directly using zinc alloys as anodes. On the other hand, theoretical research is mainly based on adsorption energy, differential charge density, and molecular dynamics. Finally, this paper summarizes the research progress on AZIBs and puts forward some prospects.

Progress in the preparation of Prussian blue-based nanomaterials for biomedical applications

Prussian blue (PB) is composed of the coordination network of Fe²⁺-CN-Fe³⁺ mixed valence state as a classic metal complex, which includes a C atom and Fe²⁺ (low spin), N atom and Fe³⁺ (high spin). PB and its analogues (PBA) have excellent biosafety, good magnetic properties, outstanding photothermal properties and the ability to mimic enzymatic behaviors due to their stable structure, tunable size, controllable morphology, abundant modification methods and excellent physicochemical properties. They have received increasing research interest and have shown promising applications in the biomedical field. Here, progress in the preparation of PB-based nanomaterials for biomedical applications is summarized and discussed. The preparation strategies, traditional synthesis and emerging preparation methods of PB are summarized systematically in this review. The design and preparation of PBA, PB(PBA)-based hollow structures and PB(PBA)-based composites are also included. While introducing the preparation status, some PB-based nanomaterials that have performed well in specific biomedical fields are emphasized. More importantly, the key factors and future development of PB for the clinical translation as multifunctional nanomaterials are also discussed. This review provides a reference for the design and biomedical application of PB-based nanomaterials.

In situ Self-Catalyzed Growth of Manganese-Embedded 3D Flakes-Coated Carbon Rod as an Efficient Oxygen-Reduction Reaction Catalyst of Zinc-Air Batteries

The in situ self-catalyzed growth of manganese-embedded 3D flakes-coated carbon rods (GFC) as an efficient oxygen-reduction reaction (ORR) catalyst of Zinc-air batteries is described for the first time. By optimizing the amount of Mn in the precursor, a series of 3D graphene-like flakes-coated carbon rods were synthesized. GFC with a doping amount of Mn of 10 % (GFC-10) exhibits excellent ORR performance with an onset potential of 0.94 V (vs. reversible hydrogen electrode). The Zinc-air battery is constructed with GFC-10 as the cathode catalyst, and it exhibits a peak power density of 128.9 mW cm-2 and a cycling stability of 75 h at a current density of 10 mA cm-2 , which are superior to the commercial 20 wt% Pt/C-based Zinc-air battery. Interestingly, the introduction of Mn facilitates the self-catalyzed growth of carbon rods, and the change of Mn amount can effectively regulate the morphology of materials. The improved ORR performance of the catalyst is ascribed to the synergistic effect of unique hierarchical porous structure, high-charge transport capacity, abundant carbon defects/edges and Mn-Nx sites. This research provides a new avenue to fabricating highly active Mn-based electrocatalysts for renewable energy systems.

Dendrite-Free Engineering toward Efficient Zinc Storage: Recent Progress and Future Perspectives

Zinc-based energy storage has lately gained popularity due to natural abundance, operational safety, high energy density. Unfortunately, dendrite growth is a common and intractable issue faced in existing zinc-ion batteries to shorten cycle lifespan/stability. This review summarizes recent progress in assembly component (e. g., anode, electrolyte, separator) engineering for dendrite-free zinc-ion batteries. First, diversiform strategies of Zn surface modification and Zn host design are presented to shield the fundamental adverse effect aroused by uneven zinc deposition on the anode. Then, subtle deployments of electrolyte constituents are illustrated to optimize the Zn²⁺ solvation structure for ultimate dendrite control and Coulombic efficiency elevation in aqueous systems and beyond (e. g., eutectic electrolytes). Furthermore, rational manipulation of advanced separators and the upgrade of zinc metal-free Zn²⁺ -storage devices are briefly discussed to explore the dendrite-free and high-level Zn²⁺ -storage. Finally, challenges and perspectives are proposed to offer research inspirations toward safe, high-efficiency and long-lifespan zinc storage.