Recent Advances in Structural Optimization and Surface Modification on Current Collectors for High-Performance Zinc Anode: Principles, Strategies, and Challenges

Exploring cyclodextrin-driven advancements in aqueous Zn-ion battery: A review

The growing demand for sustainable and efficient energy storage solutions has emphasized the value of aqueous zinc-ion batteries (AZIBs) as a safer and less expensive alternative to lithium-ion batteries. Despite their potential, AZIBs confront considerable obstacles, particularly the production of zinc dendrites and side reactions such hydrogen evolution, which limit their cycling stability and practical applicability. In this review, we explore the prospective function of cyclodextrins (CDs), a type of supramolecular carbohydrate polymer, in addressing such challenges. CDs, with their unique capacity to form inclusion complexes, provide an innovative approach for controlling zinc deposition, limiting dendrite development, and minimizing parasitic interactions. We present a detailed assessment of recent improvements in the use of CDs to change electrolytes and the electrode/electrolyte interface, resulting in improved electrochemical performance of AZIBs. This review focuses on CDs' potential as multifunctional additives for improving zinc anode stability, extending battery life, and facilitating large-scale AZIB adoption.

Current status and advances in zinc anodes for rechargeable aqueous zinc-air batteries

To promote sustainable development and reduce fossil fuel consumption, there is a growing demand for high-performance, cost-effective, safe and environmentally friendly batteries for large-scale energy storage systems. Among the emerging technologies, zinc-air batteries (ZABs) have attracted significant interest. By integrating the principles of traditional zinc-ion batteries and fuel cells, ZABs offer remarkably high theoretical energy density at lower production cost compared to the current state-of-the-art lithium-ion batteries (LIBs). However, the critical challenge remains in developing high-performance zinc anode. Herein, this review provides a comprehensive analysis of the current status and advancements in zinc anodes for rechargeable aqueous ZABs. We begin by highlighting the major challenges and underlying mechanisms associated with zinc anodes including issues such as uneven zinc deposition, dendrite growth and hydrogen evolution reaction. Then, this review discusses the recent advancements in zinc anode modifications, focusing on strategies such as alloying, surface porosity and zincophilicity. By reviewing the latest research, we also identify existing gaps and pose critical questions that need further exploration to push the field forward. The goal of this review is to inspire new research directions and promote the development of more efficient zinc anodes.

Stress Release of Zincophilic N-Doped Carbon@Sn Composite on High-Curvature Surface of Zinc Foam for Dendrite-Free 3D Zinc Anode

Commercial 3D zinc foam anodes with high deposition space and ion permeation have shown great potential in aqueous ion batteries. However, the local accumulated stress from its high-curvature surface exacerbates the Zn dendrite issue, leading to poor reversibility. Herein, we have employed zincophilic N-doped carbon@Sn composites (N-C@Sn) as nano-fillings to effectively release the local stress of high curvature surface of 3D Zn foams toward dendrite-free anode in aqueous zinc ion battery (AZIB). These electronegative and conductive N-C@Sn nano-fillings as supporters can provide a highly zincophilic channel for initial Zn nucleation and reduce local current density for regulating Zn deposition. Uniform Zn deposition further assists homogenous stress distribution on the platting surface, which gives a positive feedback loop to improve anode reversibility. As a result, zinc foam with N-C@Sn composite (ZCSn Foam) symmetric cell achieves a long cycle lifespan of 1100h at 0.5 mA cm-2, much more than that of Zn Foam (∼80 h lifespan). The full cell ZCSn Foam||MnO2 exhibits remarkable reversibility with 67% retention after 1000 cycles at 0.8 A g-1 and 76% after 1600 cycles at 2 Ag-1. This 3D-constructing strategy may offer a promising and practical pathway for metal anode application.

Recent Advances in Current Collectors for Aqueous Zinc-ion Batteries

Aqueous zinc-ion batteries (AZIBs) are promising options for large-scale electrical energy storage because of their safety, affordability, and environmental friendliness. As an indispensable component of AZIBs, a current collector plays a crucial role in supporting electrode materials and collecting the accumulated electrical energy. Recently, some progress has been made in the study of current collectors for AZIBs; however, only few comprehensive reviews on this topic are available. In this review, the systematic summary and discussion of research progress on current collectors for AZIBs is presented. Furthermore, the main challenges and key prospects for the future development of current collectors for AZIBs are discussed.

The challenges and strategies towards high-performance anode-free post-lithium metal batteries

With the merits of high theoretical energy density and ease of manufacture, anode-free post-lithium metal batteries have drawn extensive attention and have been rapidly emerging in recent years. However, the poor reversibility of metal anodes has severely hindered the realization of high-performance anode-free batteries. In this review, the critical challenges and strategies for achieving high-performance anode-free metal batteries are first elucidated. Then, the significant research studies devoted to promoting the reversibility of metal anodes for anode-free post-lithium (including sodium-, potassium- and zinc-) metal batteries are exclusively discussed to extract the principles for their practical implementation. Additionally, remedial solutions of supplying metal to the anode for improving the cyclability of anode-free batteries are also introduced. Finally, we summarize the advancements in anode-free post-lithium metal batteries, and propose some promising directions in this area. This review aims to provide a more comprehensive understanding towards the strategies for achieving highly reversible anode-free post-lithium metal batteries and a timely overview of the latest developments in this emerging field.

Planar Deposition via In Situ Conversion Engineering for Dendrite-Free Zinc Batteries

Owing to the considerable capacity, high safety, and abundant zinc resources, zinc-ion batteries (ZIBs) have been garnering much attention. Nonetheless, the unsatisfactory cyclic lifespan and poor reversibility originate from side reactions and dendrite obstacles to their practical applications. In addition to inhibiting the corrosion of aqueous electrolytes, regulating planar deposition is a key strategy to enhance their long-term stability. Herein, an in situ conversion strategy is reported to construct a protective "dual-layer" structure (VZSe/V@Zn) on zinc metal, consisting of the VSe2-ZnSe outer layer with low lattice mismatch to Zn (002) plane, and corrosion-resistant nanometallic V inner layer. Such design integrates superior interfacial ionic/electronic transfer, corrosion resistance, and unique planar deposition regulation capability. The as-prepared VZSe/V@Zn demonstrates remarkable durability of 238 h at 50 mA cm-2 with a high depth of discharge (68.3% DOD) in the Zn||Zn symmetric cell. Even in the anode-free system, the as-prepared protective layer can extend the cycle life up to 2000 cycles, with an outstanding capacity retention of 93.1% and ultra-high average coulombic efficiency of 99.998%. This work delineates an effective strategy for fabricating lattice-matching protective layers, with profound implications for elucidating zinc deposition mechanisms and paving the way for the development of high-performance zinc batteries.

Rapid and sensitive determination of legacy and emerging per- and poly-fluoroalkyl substances with solid-phase microextraction probe coupled with mass spectrometry

This study was designed to develop a rapid and sensitive method for quantifying legacy and emerging per- and polyfluoroalkyl substances (PFASs) in environmental samples with solid-phase microextraction (SPME) coupled with mass spectrometry (MS). An innovative SPME probe was fabricated via in situ polymerization, and the probe coating was optimized with response surface methodology to maximize the fluorine-fluorine interactions and electrostatic properties and ensure high selectivity for the target PFASs with enrichment factors of 48-491. The coupled SPME and MS provided a rapid and sensitive method for analyses of PFASs, with excellent linearity (r ≥ 0.9962) over the concentration range 0.001-1 μg/L and remarkably low detection limits of 0.1-13.0 ng/L. This method was used to analyze trace PFASs in tap water, river water, and wastewater samples and proved to be a simple and efficient analytical method for selective enrichment and detection of contaminants in the environment.

A bio-based functional separator enables dendrite-free anodes in aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) have garnered considerable interest as potential solutions for large-scale energy storage systems, owing to their cost-effectiveness and high safety. Nonetheless, the development of AZIBs is hindered by significant challenges associated with dendrite growth and side reactions on Zn anodes. Here, a bio-based separator derived from cellulose was developed for the dendrite-free anode in AZIBs. In addition, the separator is notable for its ultra-low cost and biodegradability in contrast to the commonly used commercial glass fiber (GF) separators. The mechanical strength of the separator is enhanced by the cross-linking of hydrogen bonds, effectively inhibiting dendrite growth. The zinc-philic groups facilitate better binding to Zn2+, resulting in uniform nucleation and deposition. The hydrophilic groups aid in trapping water molecules, thereby preventing side reactions of the electrolyte. The Zn||Zn symmetric cell with this separator can sustain a long cycle life for over 800 h, indicating stable Zn2 + plating and stripping with suppressed dendrite growth. Concurrently, the assembled Zn||VO2 full batteries exhibited a capacity retention rate of 61.87% after 1,000 cycles at 1 A g-1 with an initial capacity of 140 mAh g-1. This work highlights a stable, economical, and eco-friendly approach to the design of bio-based separators in AZIBs for sustainable energy storage systems.

Achievement of Efficient and Stable Nonflow Zinc-Bromine Batteries Assisted by Rational Decoration upon the Two Electrodes

Aqueous zinc-bromine batteries (ZBBs) are highly promising because of the advantages of safety and cost. Compared with flow ZBBs, static ones without the assistance of pumping and tank components possess decreased cost and increased energy density and efficiency. Yet, the issues of Zn dendrites and shuttle effect of polybromide ions (Brn-) are more serious in nonflow ZBBs. Meanwhile, the hydrogen evolution reaction (HER) and the sluggish kinetics of the Br2/Br- couple are also in-negligible. Herein, a compressive approach, the cation-exchange membrane (CEM) coating on Zn anodes and N-defect decoration toward carbon felt cathodes, is developed. The CEM with cation-only function can inhibit the formation of Zn dendrites via tuning the Zn2+ flow at the interface, block the noncationic substances, and hence prevent the shuttle of Br2/Brn- and the water decomposition-concerned HER. The optimized nonflow ZBBs can deliver high Coulombic, voltage, and energy efficiencies of 94.1, 92.8, and 87.4%, respectively, which can be well remained in 1000 cycles. Meanwhile, the output voltage is as high as 1.7 V at 10 mA cm-2 with a high areal capacity of 2 mA h cm-2, and a LED with a rated voltage of 1.6 V can be powered successfully, exhibiting high application value.

Design Principles and Mechanistic Understandings of Non-Noble-Metal Bifunctional Electrocatalysts for Zinc-Air Batteries

Zinc-air batteries (ZABs) are promising energy storage systems because of high theoretical energy density, safety, low cost, and abundance of zinc. However, the slow multi-step reaction of oxygen and heavy reliance on noble-metal catalysts hinder the practical applications of ZABs. Therefore, feasible and advanced non-noble-metal electrocatalysts for air cathodes need to be identified to promote the oxygen catalytic reaction. In this review, we initially introduced the advancement of ZABs in the past two decades and provided an overview of key developments in this field. Then, we discussed the working mechanism and the design of bifunctional electrocatalysts from the perspective of morphology design, crystal structure tuning, interface strategy, and atomic engineering. We also included theoretical studies, machine learning, and advanced characterization technologies to provide a comprehensive understanding of the structure-performance relationship of electrocatalysts and the reaction pathways of the oxygen redox reactions. Finally, we discussed the challenges and prospects related to designing advanced non-noble-metal bifunctional electrocatalysts for ZABs.

Surface Patterning of Metal Zinc Electrode with an In-Region Zincophilic Interface for High-Rate and Long-Cycle-Life Zinc Metal Anode

The undesirable dendrite growth induced by non-planar zinc (Zn) deposition and low Coulombic efficiency resulting from severe side reactions have been long-standing challenges for metallic Zn anodes and substantially impede the practical application of rechargeable aqueous Zn metal batteries (ZMBs). Herein, we present a strategy for achieving a high-rate and long-cycle-life Zn metal anode by patterning Zn foil surfaces and endowing a Zn-Indium (Zn-In) interface in the microchannels. The accumulation of electrons in the microchannel and the zincophilicity of the Zn-In interface promote preferential heteroepitaxial Zn deposition in the microchannel region and enhance the tolerance of the electrode at high current densities. Meanwhile, electron aggregation accelerates the dissolution of non-(002) plane Zn atoms on the array surface, thereby directing the subsequent homoepitaxial Zn deposition on the array surface. Consequently, the planar dendrite-free Zn deposition and long-term cycling stability are achieved (5,050 h at 10.0 mA cm-2 and 27,000 cycles at 20.0 mA cm-2). Furthermore, a Zn/I2 full cell assembled by pairing with such an anode can maintain good stability for 3,500 cycles at 5.0 C, demonstrating the application potential of the as-prepared ZnIn anode for high-performance aqueous ZMBs.

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.

A Sustainable Dual Cross-Linked Cellulose Hydrogel Electrolyte for High-Performance Zinc-Metal Batteries

Aqueous rechargeable Zn-metal batteries (ARZBs) are considered one of the most promising candidates for grid-scale energy storage. However, their widespread commercial application is largely plagued by three major challenges: The uncontrollable Zn dendrites, notorious parasitic side reactions, and sluggish Zn2+ ion transfer. To address these issues, we design a sustainable dual cross-linked cellulose hydrogel electrolyte, which has excellent mechanical strength to inhibit dendrite formation, high Zn2+ ions binding capacity to suppress side reaction, and abundant porous structure to facilitate Zn2+ ions migration. Consequently, the Zn||Zn cell with the hydrogel electrolyte can cycle stably for more than 400 h under a high current density of 10 mA cm-2. Moreover, the hydrogel electrolyte also enables the Zn||polyaniline cell to achieve high-rate and long-term cycling performance (> 2000 cycles at 2000 mA g-1). Remarkably, the hydrogel electrolyte is easily accessible and biodegradable, making the ARZBs attractive in terms of scalability and sustainability.