Solid Electrolyte Interface in Zn-Based Battery Systems

Aspartame Endowed ZnO-Based Self-Healing Solid Electrolyte Interface Film for Long-Cycling and Wide-Temperature Aqueous Zn-Ion Batteries

Metallic Zn anodes suffer from hydrogen evolution and dendritic deposition in aqueous electrolytes, resulting in low Coulombic efficiency and poor cyclic stability for aqueous Zn-ion batteries (AZIBs). Constructing stable solid electrolyte interphase (SEI) with strong affinity for Zn and exclusion of water corrosion of Zn metal anodes is a promising strategy to tackle these challenges. In this study, we develop a self-healing ZnO-based SEI film on the Zn electrode surface by employing an aspartame (APM) as a versatile electrolyte additive. The hydrophobic nature and strong Zn affinity of APM can facilitate the dynamic self-healing of ZnO-based SEI film during cyclic Zn plating/stripping process. Benefiting from the superior protection effect of self-healing ZnO-based SEI, the Zn║Cu cells possess an average coulombic efficiency more than 99.59% over 1,000 cycles even at a low current density of 1 mA cm-2 - 1 mAh cm-2. Furthermore, the Zn║NH4+-V2O5 full cells display a large specific capacity of 150 mAh g-1 and high cyclic stability with a capacity retention of 77.8% after 1,750 cycles. In addition, the Zn║Zn cell delivers high temperature adaptability at a wide-temperature range from - 5 to 40 °C even under a high DOD of 85.2%. The enhanced capability and durability originate from the self-healing SEI formation enabled by multifunctional APM additives mediating both corrosion suppression and interfacial stabilization. This work presents an inspired and straightforward approach to promote a dendrite-free and wide-temperature rechargeable AZIBs energy storage system.

From Ab Initio to Instrumentation: A Field Guide to Characterizing Multivalent Liquid Electrolytes

In this field guide, we outline empirical and theory-based approaches to characterize the fundamental properties of liquid multivalent-ion battery electrolytes, including (i) structure and chemistry, (ii) transport, and (iii) electrochemical properties. When detailed molecular-scale understanding of the multivalent electrolyte behavior is insufficient we use examples from well-studied lithium-ion electrolytes. In recognition that coupling empirical and theory-based techniques is highly effective, but often nontrivial, we also highlight recent electrolyte characterization efforts that uncover a more comprehensive and nuanced understanding of the underlying structures, processes, and reactions that drive performance and system-level behavior. We hope the insights from these discussions will guide the design of future electrolyte studies, accelerate development of next-generation multivalent-ion batteries through coupling of modeling with experiments, and help to avoid pitfalls and ensure reproducibility of modeling results.

Fundamentals, Advances and Perspectives in Designing Eutectic Electrolytes for Zinc-Ion Secondary Batteries

Zinc-ion secondary batteries have been competitive candidates since the "post-lithium-ion" era for grid-scale energy storage, owing to their plausible security, high theoretical capacity, plentiful resources, and environment friendliness. However, many encumbrances like notorious parasitic reactions and Zn dendrite growth hinder the development of zinc-ion secondary batteries remarkably. Faced with these challenges, eutectic electrolytes have aroused notable attention by virtue of feasible synthesis and high tunability. This review discusses the definition and advanced functionalities of eutectic electrolytes in detail and divides them into nonaqueous, aqueous, and solid-state eutectic electrolytes with regard to the state and component of electrolytes. In particular, the corresponding chemistry concerning solvation structure regulation, electric double layer (EDL) structure, solid-electrolyte interface (SEI) and charge/ion transport mechanism is systematically elucidated for a deeper understanding of eutectic electrolytes. Moreover, the remaining limitations and further development of eutectic electrolytes are discussed for advanced electrolyte design and extended applications.

Enabling high-performance multivalent metal-ion batteries: current advances and future prospects

The battery market is primarily dominated by lithium technology, which faces severe challenges because of the low abundance and high cost of lithium metal. In this regard, multivalent metal-ion batteries (MVIBs) enabled by multivalent metal ions (e.g. Zn2+, Mg2+, Ca2+, Al3+, etc.) have received great attention as an alternative to traditional lithium-ion batteries (Li-ion batteries) due to the high abundance and low cost of multivalent metals, high safety and higher volumetric capacities. However, the successful application of these battery chemistries requires careful control over electrode and electrolyte chemistries due to the higher charge density and slower kinetics of multivalent metal ions, structural instability of the electrode materials, and interfacial resistance, etc. This review comprehensively explores the recent advancements in electrode and electrolyte materials as well as separators for MVIBs, highlighting the potential of MVIBs to outperform Li-ion batteries regarding cost, energy density and safety. The review first summarizes the recent progress and fundamental charge storage mechanism in several MVIB chemistries, followed by a summary of major challenges. Then, a thorough account of the recently proposed methodologies is given including progress in anode/cathode design, electrolyte modifications, transition to semi-solid- and solid-state electrolytes (SSEs), modifications in separators as well as a description of advanced characterization tools towards understanding the charge storage mechanism. The review also accounts for the recent trend of using artificial intelligence in battery technology. The review concludes with a discussion on prospects, emphasizing the importance of material innovation and sustainability. Overall, this review provides a detailed overview of the current state and future directions of MVIB technology, underscoring its significance in advancing next-generation energy storage solutions.

Revealing the chemical compatibility of common solvents and electrolytes with Mo2TiC2-based MXenes and their interfaces in aluminum-ion batteries (AIBs) through first-principles molecular dynamics simulations

Using the first-principles molecular dynamics simulations and CI-NEB calculations, we performed a systematic and comprehensive investigation on the chemical compatibility of various solvents (carbonate esters, aromatic solvents, ethers, carboxylic esters, water, DMSO and ionic liquids) and electrolytes (DMC-Al(OTF)3, DME-Al(OTF)3, GBL-Al(OTF)3, H2O-Al2(SO4)3, DMSO-Al(OTF)3, [EMIm]+Cl--[AlCl3] and urea-AlCl3) with Mo2TiC2-based MXenes, evaluating their possible use as solvents, additives and electrolytes in aluminum-ion batteries (AIBs). Among the investigated solvents, carbonate ester (DMC), chain ether (DME), aromatic hydrocarbons (benzene, toluene), chain carboxylic ester (GBL), DMSO, ionic liquids ([EMIm]+Cl-, [DMPI]+Cl- and [BMP]+Cl-) and urea showed very low reactivity towards both bare Mo2TiC2 and Al-terminated structures (Mo2TiC2Al2 and Mo2TiC2Al6 monolayers), indicating their excellent chemical compatibility between these solvents and the MXene cathode. Besides the Mo2TiC2 monolayer, a relatively low chemical reactivity was predicted for Al-terminated MXenes after their contact with almost all the solvents considered in this work, even with the relatively more reactive carbonate esters (PC and EC) and ethers (G2 and THF). The electrolytes DMC-Al(OTF)3 and ionic liquid ([EMIm]+Cl--AlCl3) exhibited high chemical compatibility with Mo2TiC2-based MXenes and exhibited promising electrochemical reactivity at the interface between the electrolyte and electrode. Alternatively, either the decomposition of the electrolyte components or the low electrochemical reactivity of Al3+ was observed in other electrolyte systems (DME-Al(OTF)3, GBL-Al(OTF)3, H2O-Al2(SO4)3, DMSO-Al(OTF)3 and urea-AlCl3), indicating poor reversibility and cyclic performance of AIBs.

A Gradient Solid-like Electrolyte Stabilizing Zn Anodes by In Situ Formation of a ZnSe Interphase

Rechargeable aqueous Zn-ion batteries are renowned for their safety, cost-effectiveness, environmental friendliness, and high capacity. However, critical issues, such as restricted electrode kinetics and uncontrolled dendrite growth of Zn anodes, have hindered their practical applications. Here, we propose a gradient solid-like electrolyte (GSLE) to enhance the overall performance of Zn anodes and Zn-ion batteries. It shows a high room-temperature conductivity of 13.3 mS cm-1 with an enhanced Zn2+ transference number of 0.67. With its negatively charged network, the GSLE establishes a Zn2+-rich region at the Zn|electrolyte interface, thereby boosting the interfacial charge transfer and accelerating electrode kinetics. Moreover, the GSLE in situ establishes a ZnSe-containing interphase on the surface of Zn anodes during cycling. Such an interphase effectively guides uniform Zn deposition and inhibits side reactions. As a result, symmetric cells using the GSLE demonstrate stabilized Zn plating/stripping cycling over 1400 h and tolerate a high critical current of 15 mA cm-2. Furthermore, the assembled vanadium-based full cells deliver a remarkable capacity of 125.4 mAh g-1 at 4 A g-1 and achieve a 90% capacity retention after 1000 cycles.

Regulation of Zinc Hydroxide Sulfate Growth Environment for Stable Zinc Anode/Electrolyte Interfaces

Metallic Zn is a promising anode for high-safety, low-cost, and large-scale energy storage systems. However, it is strongly hindered by unstable electrode/electrolyte interface issues, including zinc dendrite, corrosion, passivation, and hydrogen evolution reactions. In this work, an in situ interface protection strategy is established by turning the corrosion/passivation byproducts (zinc hydroxide sulfates, ZHSs) into a stable hybrid protection layer. The hydrolysis of the diglycolamine buffer layer on the zinc anode provides a homogeneous basic electrolyte environment for the generation of small-sized ZHS, thereby leading to the formation of a ZHS-based hybrid layer. Benefiting from this hybrid layer, uniform zinc ion flux and high anticorrosion ability can be achieved. As a result, the decorated symmetric cell presents a long cycling lifespan of over 1500 h at a current density of 1 mA cm-2 and an area capacity of 1 mAh cm-2. It also contributes to the appealing cycling and rate performance of Zn|NH4V4O10 full cells. This work provides insight into regulating and reusing interfacial byproducts for high-performance zinc metal batteries.

Regulating Intermolecular Hydrogen Bonds in Organic Cathode Materials to Realize Ultra-stable, Flexible and Low-temperature Aqueous Zinc-organic Batteries

Rational design of molecular structures is one of the effective strategies to obtain high-performance organic cathode materials. However, besides the optimization of single-molecule structures, the influence of the "weak" interaction forces (e.g. hydrogen bonds) in organic cathode materials on the performance of batteries should be fully considered. Herein, three organic small molecules with different numbers of hydroxyl groups (namely nitrogen heterocyclic tetraketone (DAB), monohydroxyl nitrogen heterocyclic dione (HDA), dihydroxyl nitrogen heterocyclic dione (DHT)) were selected as the cathodes of aqueous zinc ion batteries (AZIBs), and the effect of the intermolecular hydrogen bonds on their electrochemical performance was studied for the first time. Clearly, the stable hydrogen-bond networks built through the hydroxyl groups significantly enhance the cycle stability of organic small-molecule cathodes and facilitate rapid proton conduction between the hydrogen-bond networks through the Grotthuss mechanism, thereby endowing them with excellent rate performance. In addition, a larger and more dense two-dimensional hydrogen-bond network can be constructed through multiple hydroxyl groups, further enhancing the structural stability of organic small-molecule cathodes, giving them better cycle tolerance, excellent rate performance, and extreme environmental tolerance.

In-Situ Self-Respiratory Solid-to-Hydrogel Electrolyte Interface Evoked Well-Distributed Deposition on Zinc Anode for Highly Reversible Zinc-Ion Batteries

The aqueous zinc-ion batteries (AZIB) have emerged as a promising technology in the realm of electrochemical energy storage. Despite its potential advantages in terms of safety, cost-effectiveness, and inherent safety, AZIB faces significant challenges. Issues attributed to unsupported thermodynamics and non-uniform potential distribution and deposition, present formidable obstacles that necessitate resolution. To tackle these challenges, a novel strategy adapting hybrid organic-inorganic in situ derived solid-to-hydrogel electrolyte interface (StHEI) has been developed from coordination reactions and self-respiratory process, establishing uniform diffusion channels by ion bridges and accelerating ion transport. Self-respiratory pattern of StHEI realized through in situ inorganic component conversion further prolongs the protecting duration, which effectively mitigates corrosion and passivation but enhance the mechanical properties of the StHEI measured through Young's modulus. This novel StHEI promotes well-distributed potential lines within the Helmholtz regions. Zn2+ are finally induced to deposit and nucleate in a compact, fine, and uniform manner. Asymmetrical batteries assembled with the modified Zn electrode and bare Zn exhibit exceptional stability over 3000 h (1 mA cm-2-0.5 mAh cm-2). The asymmetrical Cu//Zn cell achieved an outstanding average Coulombic efficiency (CE) of 99.6 % over 1200 cycles.

Flexible, self-healing and portable supramolecular visualization smart sensors for monitoring and quantifying structural damage

Visually monitoring micro-crack initiation and corrosion failure evolution is crucial for early diagnosis of structural health and ensuring safe operation of infrastructures. However, existing damage detecting approaches are subject to the limited-detection of heterogeneous structures, intolerance of harsh environments, and challenge of quantitative analysis, impeding applications in structural health monitoring (SHM). Herein, we present a stretchable, semi-quantitative, instrument-free, supramolecular SHM sensor by integrating a polyurea elastomer with sensitive corrosion-probes, enabling localized corrosion monitoring and quantification of failure dynamics. Initially, a correlation between visual monitoring signals and structural health status is proposed, and sensor-based image processing software that accurately quantifies structural failure indicators (crack scale, corrosion reactivity and deterioration status) is proposed. Moreover, this sensor can be fabricated as multiple derivatives: a coating or patch covered on metallic substrates and an ionic-responsive test strip, ensuring real-time detection of the initiation of pitting, degradation events of metallic components and convenient monitoring of ion concentrations in corrosive media. Furthermore, the inherent geometric plasticity and dynamic hydrogen-bonded network validates the reliability for heterogeneous components and stability under extreme environments of sensors. This portable, smart SHM strategy established the channel-transformation model from corrosion dynamics to visual signals, exhibiting prospects for structural monitoring in offshore energy-harvesting equipment.

A carrageenan-induced highly stable Zn anode by regulating interface chemistry

Zinc-ion batteries (ZIBs) are promising on account of the inherent safety, minimal toxicity, cost-effectiveness, and high theoretical capacity. However, the critical issues including the Zn dendrites and side reactions impede their commercial application. Here, we propose green, non-toxic and biological carrageenan (Carr) serving as an electrolyte additive to address the aforementioned issues. Owing to the multifunctional groups, Carr has the capacity to interact with Zn2+, thereby modulating the solvation configuration of Zn2+ and changing the ion distribution at the electrode-electrolyte interface. Moreover, it can adsorb on the Zn electrode and induce the formation of a solid electrolyte interphase (SEI) consisting of ZnO, ZnS and R-SO2 species. It contributes to uniform Zn2+ ion diffusion and even Zn deposition with the preferable (002) plane. Consequently, the Zn||Zn cells exhibit a stable cycle performance for 800 h at 5 mA cm-2 and 5 mA h cm-2. An elevated coulombic efficiency of 99.2% over 1800 cycles is obtained in the Zn||Cu cells using the electrolyte with Carr. Benefitting from the highly stable and reversible Zn anode, the Zn||VO2 full cell also delivers a high performance in comparison with the bare ZnSO4 electrolyte, favoring the practical implementation of ZIBs.

Crystallographic Reorientation Induced by Gradient Solid-Electrolyte Interphase for Highly Stable Zinc Anode

Oriented zinc (Zn) electrodeposition is critical for the long-term performance of aqueous Zn metal batteries. However, the intricate interfacial reactions between the Zn anode and electrolytes hinder a comprehensive understanding of Zn metal deposition. Here, the reaction pathways of Zn deposition and report the preferential formation of Zn single-crystalline nuclei followed by dense Zn(002) deposition is elucidated, which is induced by a gradient solid-electrolyte interphase (SEI). The gradient SEI composed of abundant B-O and C species facilitates faster Zn2+ nucleation rate and smaller nucleus size, promoting the formation of Zn single-crystalline nuclei. Additionally, the homogeneity and mechanical stability of SEI ensure the crystallographic reorientation of Zn anodes from Zn(101) to (002) planes, efficiently inhibiting dendrite growth and metal corrosion during the Zn2+ stripping/plating process. These advantages significantly enhance the stability of the Zn anode, as demonstrated by the prolonged cycling lifespan of symmetric Zn batteries and exceptional reversibility (>99.5%) over 5000 cycles in Zn//Cu asymmetric batteries. Notably, this strategy also enables the stable operation of anode-free Zn//I2 batteries with a long lifespan of 3000 cycles. This work advances the understanding of Zn electrochemical behaviors, encompassing Zn nucleation, growth, and Zn2+ stripping/plating.

In Situ Formed Robust Solid Electrolyte Interphase with Organic-Inorganic Hybrid Layer for Stable Zn Metal Anode

Stabilizing the Zn anode/electrolyte interface is critical for advancing aqueous zinc ion storage technologies. Addressing this challenge helps minimize parasitic reactions and controls the formation of Zn dendrites, which is fundamental to achieving highly reversible Zn electrochemistry. In this study, 2% by volume of dimethyl sulfoxide (DMSO) is introduced into the baseline zinc sulfate (ZS) electrolyte, which acts as an efficient regulator to form a robust solid-electrolyte interphase (SEI) on the Zn anode. This innovative approach enables uniform Zn deposition and does not substantially modify the Zn2+ solvation structure. The Zn||Zn symmetric cell exhibits an extended cycle life of nearly one calendar year (>8500 h) at a current density of 0.5 mA cm-2 and an areal capacity of 0.5 mAh cm-2. Impressive full cell performance can be achieved. Specifically, the Zn||VS2 full cell achieves an areal capacity of 1.7 mAh cm-2, with a superior negative-to-positive capacity ratio of 2.5, and an electrolyte-to-capacity ratio of 101.4 µL mAh-1, displaying remarkable stability over 1000 cycles under a high mass loading of 11.0 mg cm-2 without significant degradation. This innovative approach in electrolyte engineering provides a new perspective on in situ SEI design and furthers the understanding of Zn anode stabilization.

Molecular Synergistic Effects Mediate Efficient Interfacial Chemistry: Enabling Dendrite-Free Zinc Anode for Aqueous Zinc-Ion Batteries

The primary cause of the accelerated battery failure in aqueous zinc-ion batteries (AZIBs) is the uncontrollable evolution of the zinc metal-electrolyte interface. In the present research on the development of multiadditives to ameliorate interfaces, it is challenging to elucidate the mechanisms of the various components. Additionally, the synergy among additive molecules is frequently disregarded, resulting in the combined efficacy of multiadditives that is unlikely to surpass the sum of each component. In this study, the "molecular synergistic effect" is employed, which is generated by two nonhomologous acid ester (NAE) additives in the double electrical layer microspace. Specifically, ethyl methyl carbonate (EMC) is more inclined to induce the oriented deposition of zinc metal by means of targeted adsorption with the zinc (002) crystal plane. Methyl acetate (MA) is more likely to enter the solvated shell of Zn2+ and will be profoundly reduced to produce SEI that is dominated by organic components under the "molecular synergistic effect" of EMC. Furthermore, MA persists in a spontaneous hydrolysis reaction, which serves to mitigate the pH increase caused by the hydrogen evolution reaction (HER) and further prevents the formation of byproducts. Consequently, the 1E1M electrolyte not only extends the cycle life of the zinc anode to 3140 cycles (1 mA h cm-2 and 1 mA cm-2) but also extends the life of the Zn//MnO2 full battery, with the capacity retention rate still at 89.9% after 700 cycles.

High-Entropy Multiple-Anion Aqueous Electrolytes for Long-Life Zn-Metal Anodes

Aqueous zinc-ion batteries (AZIBs) hold great promise for large-scale energy storage applications, however, their practical use is significantly hindered by issues such as zinc dendrite growth and hydrogen evolution. To address these challenges, we propose a high-entropy (HE) electrolyte design strategy that incorporates multiple zinc salts, aimed at enhancing ion kinetics and improving the electrochemical stability of the electrolyte. The interactions between multiple anions and Zn2+ increase the complexity of the solvation structure, resulting in smaller ion clusters while maintaining weakly anion-rich solvation structures. This leads to improved ion mobility and the formation of robust interphase layers on the electrode-electrolyte interface. Moreover, the HE electrolyte effectively suppresses hydrogen evolution and corrosion side reactions while facilitating uniform and reversible Zn plating/stripping processes. Impressively, the optimized electrolyte enables dendrite-free Zn plating/stripping for over 3000 h in symmetric cells and achieves a high Coulombic efficiency of 99.5% at 10 mA cm-2 in asymmetric cells. Inspiringly, full cells paired with Ca-VO2 cathodes demonstrate excellent performance, retaining 81.5% of the initial capacity over 1800 cycles at 5 A g-1. These significant findings highlight the potential of this electrolyte design strategy to improve the performance and lifespan of Zn-metal anodes in AZIBs.

Multifunctional Self-Assembled Bio-Interfacial Layers for High-Performance Zinc Metal Anodes

Rechargeable aqueous zinc-ion (Zn-ion) batteries are widely regarded as important candidates for next-generation energy storage systems for low-cost renewable energy storage. However, the development of Zn-ion batteries is currently facing significant challenges due to uncontrollable Zn dendrite growth and severe parasitic reactions on Zn metal anodes. Herein, we report an effective strategy to improve the performance of aqueous Zn-ion batteries by leveraging the self-assembly of bovine serum albumin (BSA) into a bilayer configuration on Zn metal anodes. BSA's hydrophilic and hydrophobic fragments form unique and intelligent ion channels, which regulate the migration of Zn ions and facilitate their desolvation process, significantly diminishing parasitic reactions on Zn anodes and leading to a uniform Zn deposition along the Zn (002) plane. Notably, the Zn||Zn symmetric cell with BSA as the electrolyte additive demonstrated a stable cycling performance for up to 2400 hours at a high current density of 10 mA cm-2. This work demonstrates the pivotal role of self-assembled protein bilayer structures in improving the durability of Zn anodes in aqueous Zn-ion batteries.

Tailoring the Whole Deposition Process from Hydrated Zn2+ to Zn0 for Stable and Reversible Zn Anode

The practical application of aqueous zinc-ion batteries (ZIBs) indeed faces challenges primarily attributed to the inherent side reactions and dendrite growth associated with the Zn anode. In the present work, N-Methylmethanesulfonamide (NMS) is introduced to optimize the transfer, desolvation, and reduction of Zn2+, achieving highly stable and reversible Zn plating/stripping. The NMS molecule can substitute one H2O molecule in the solvation structure of hydrated Zn2+ and be preferentially chemisorbed on the Zn surface to protect Zn anode against corrosion and hydrogen evolution reaction (HER), thereby suppressing byproducts formation. Additionally, a robust N-rich organic and inorganic (ZnS and ZnCO3) hybrid solid electrolyte interphase is in situ generated on Zn anode due to the decomposition of NMS, resulting in enhanced Zn2+ transport kinetics and uniform Zn2+ deposition. Consequently, aqueous cells with the NMS achieve a long lifespan of 2300 h at 1 mA cm-2 and 1 mAh cm-2, high cumulative plated capacity of 3.25 Ah cm-2, and excellent reversibility with an average coulombic efficiency (CE) of 99.7 % over 800 cycles.

In-Situ Solid Electrolyte Interface via Dual Reaction Strategy for Highly Reversible Zinc Anode

In situ construction of solid electrolyte interfaces (SEI) is an effective strategy to enhance the reversibility of zinc (Zn) anodes. However, in situ SEI to afford high reversibility under high current density conditions (≥20 mA cm-2) is highly desired yet extremely challenging. Herein, we propose a dual reaction strategy of spontaneous electrostatic reaction and electrochemical decomposition for the in situ construction of SEI, which is composed of organic-rich upper layer and inorganic-rich inner layer. Particularly, in situ SEI performs as "growth binder" at small current density and "orientation regulator" at high current density, which significantly suppresses side reactions and dendrite growth. The in situ SEI affords the record-breaking reversibility of Zn anode under practical conditions, Zn//Zn symmetric cells can stably cycle for over 1300 h and 400 h at current densities of 50 mA cm-2 and 100 mA cm-2, respectively, showcasing an exceptional cumulative capacity of 67.5 Ah cm-2. Furthermore, the practicality of this in situ SEI is verified in Zn//PANI pouch cells with high mass loading of 25.48 mg cm-2. This work provides a universal strategy to design advanced SEI for practical Zn-ion batteries.

Enabling Gradient-Structured Solid Electrolyte Interphase by a Hydrated Eutectic Electrolyte for High-Performance Zn Metal Batteries

Aqueous Zn metal batteries are attracting tremendous interest as promising energy storage systems due to their intrinsic safety and cost-effectiveness. Nevertheless, the reversibility of Zn metal anodes (ZMAs) is hindered by water-induced parasitic reactions and dendrite growth. Herein, a novel hydrated eutectic electrolyte (HEE) consisting of Zn(BF4)2·xH2O and sulfolane (SL) is developed to prevent the side reactions and achieve the outstanding cyclability of ZMAs. The strong coordination between Zn2+ and SL triggers the eutectic feature, enabling the low-temperature availability of HEEs. The restriction of BF4 - hydrolysis in the eutectic system can realize favorable compatibility between Zn(BF4)2-based electrolyte and ZMAs. Besides, the newly-established solvation structure with the participation of SL, H2O, and BF4 -, can induce in situ formation of desirable SEI with gradient structure consisting of B,O-rich species, ZnS, and ZnF2, to offer satisfactory protection toward ZMAs. Consequently, the HEE allows the Zn||Zn symmetric cell to cycle over 1650 h at 2 mA cm-2 and 1 mA h cm-2. Moreover, the Zn||NH4V4O10 full batteries can deliver a prolonged lifespan for 1000 cycles with a high capacity retention of 83.4%. This work represents a feasible approach toward the elaborate design of advanced electrolyte systems for next-generation batteries.

Robust bilayer solid electrolyte interphase for Zn electrode with high utilization and efficiency

Construction of a solid electrolyte interphase (SEI) of zinc (Zn) electrode is an effective strategy to stabilize Zn electrode/electrolyte interface. However, single-layer SEIs of Zn electrodes undergo rupture and consequent failure during repeated Zn plating/stripping. Here, we propose the construction of a robust bilayer SEI that simultaneously achieves homogeneous Zn2+ transport and durable mechanical stability for high Zn utilization rate (ZUR) and Coulombic efficiency (CE) of Zn electrode by adding 1,3-Dimethyl-2-imidazolidinone as a representative electrolyte additive. This bilayer SEI on Zn surface consists of a crystalline ZnCO3-rich outer layer and an amorphous ZnS-rich inner layer. The ordered outer layer improves the mechanical stability during cycling, and the amorphous inner layer homogenizes Zn2+ transport for homogeneous, dense Zn deposition. As a result, the bilayer SEI enables reversible Zn plating/stripping for 4800 cycles with an average CE of 99.95% (± 0.06%). Meanwhile, Zn | |Zn symmetric cells show durable lifetime for over 550 h with a high ZUR of 98% under an areal capacity of 28.4 mAh cm-2. Furthermore, the Zn full cells based on the bilayer SEI functionalized Zn negative electrodes coupled with different positive electrodes all exhibit stable cycling performance under high ZUR.

Enhancing Cycle Life of Rechargeable Zinc Hybrid Batteries in a Low-Cost, Nonfluorinated Dual-Cation Electrolyte

Rechargeable zinc batteries (RZBs) are highly attractive as energy storage solutions due to their low cost and sustainability. Nevertheless, the use of fluorine-free zinc electrolyte systems to create affordable, ecofriendly, and safe RZBs has been largely overlooked in the battery community. Previously, we showcased the utilization of a fluorine-free, nonaqueous electrolyte comprising zinc dicyanamide (Zn(dca)2) in dimethyl sulfoxide (DMSO) to enable the electrochemical cycling of zinc. Herein we present a dual-cation-based electrolyte, [1.0 M Na(dca) +1.0 M Zn(dca)2]/DMSO, in pursuit of a rechargeable zinc hybrid battery. Fourier-transform infrared spectroscopy and molecular dynamics simulation studies indicate that the presence of Na(dca) diminishes ion-pairing in Zn(dca)2 through [dca]- anion bridging between Zn2+ and Na+ ions, thereby enhancing Zn2+ ion transport in the electrolyte. Thus, the electrolyte exhibits high ionic conductivity and transference numbers (tZn2+) of 7.9 mS cm-1 and 0.83, respectively, at 50 °C, making it particularly suitable for high-temperature battery applications. Furthermore, we demonstrate, for the first time, the cycling of a full cell with a zinc anode and triphylite sodium iron phosphate cathode (NFP) in an organic electrolyte, showcasing stable performance over 100 cycles at 0.1C rate. These encouraging findings pave the way for affordable battery technologies using, fluorine-free electrolyte.

Stable Zinc Anode Facilitated by Regenerated Silk Fibroin-modified Hydrogel Protective Layer

Inherent dendrite growth and side reactions of zinc anode caused by its unstable interface in aqueous electrolytes severely limit the practical applications of zinc-ion batteries (ZIBs). To overcome these challenges, a protective layer for Zn anode inspired by cytomembrane structure is developed with PVA as framework and silk fibroin gel suspension (SFs) as modifier. This PVA/SFs gel-like layer exerts similar to the solid electrolyte interphase, optimizing the anode-electrolyte interface and Zn2+ solvation structure. Through interface improvement, controlled Zn2+ migration/diffusion, and desolvation, this buffer layer effectively inhibits dendrite growth and side reactions. The additional SFs provide functional improvement and better interaction with PVA by abundant functional groups, achieving a robust and durable Zn anode with high reversibility. Thus, the PVA/SFs@Zn symmetric cell exhibits an ultra-long lifespan of 3150 h compared to bare Zn (182 h) at 1.0 mAh cm-2-1.0 mAh cm-2, and excellent reversibility with an average Coulombic efficiency of 99.04% under a large plating capacity for 800 cycles. Moreover, the PVA/SFs@Zn||PANI/CC full cells maintain over 20 000 cycles with over 80% capacity retention under harsh conditions at 5 and 10 A g-1. This SF-modified protective layer for Zn anode suggests a promising strategy for reliable and high-performance ZIBs.

Transforming Undesired Corrosion Products into a Nanoflake-Array Functional Layer: A Gelatin-Assistant Modification Strategy for High Performance Zn Battery Anodes

As corrosion products of Zn anodes in ZnSO4 electrolytes, Zn4SO4 (OH)6·xH2O with loose structure cannot suppress persistent side reactions but can increase the electrode polarization and induce dendrite growth, hindering the practical applications of Zn metal batteries. In this work, a functional layer is built on the Zn anode by a gelatin-assistant corrosion and low-temperature pyrolysis method. With the assistant of gelatin, undesired corrosion products are converted into a uniform nanoflake array comprising ZnO coated by gelatin-derived carbon on Zn foil (denoted Zn@ZnO@GC). It is revealed that the gelatin-derived carbons not only enhance the electron conductivity, facilitate Zn2+ desolvation, and boost transport/deposition kinetics, but also inhibit the occurrence of hydrogen evolution and corrosion reactions on the zincophilic Zn@ZnO@GC anode. Moreover, the 3D nanoflake array effectively homogenizes the current density and Zn2+ concentration, thus inhibiting the formation of dendrites. The symmetric cells using the Zn@ZnO@GC anodes exhibit superior cycling performance (over 7000 h at 1 mA cm-2/1 mAh cm-2) and without short-circuiting even up to 25 mAh cm-2. The Zn@ZnO@GC||NaV3O8 full cell works stably for 5000 cycles even with a limited N/P ratio of ≈5.5, showing good application prospects.

Crown Ether Electrolyte Additive Enables High-Rate and Stable Polyviologen Cathode Material for Chloride Ion Batteries

A variety of inorganic and inorganic cathode materials for chloride ion storage are reported. However, their application in chloride ion batteries (CIB) is hindered by poor rate capability and cycling stability. Herein, an organic poly(butyl viologen dichloride) (PBVCl2) cathode material with significantly enhanced rate and cycling performance in the CIB is achieved using a crown ether (18-Crown-6) additive in the tributylmethylammonium chloride-based electrolyte. The as-prepared PBVCl2 cathodes exhibit impressive capacity increases from 149.4 to 179.1 mAh g-1 at 0.1 C and from 57.8 to 111.9 mAh g-1 at 10 C, demonstrating the best rate performance with the highest energy density among those of various reported cathodes for CIBs. This impressive performance improvement is a result of the great boosts in charge transfer, ion transport, and interface stability of the battery by the use of 18-Crown-6, which also contributes to a more than twofold increase in capacity retention after 120 cycles. The electrode reaction mechanism of the CIB based on highly reversible chloride ion transfer is revealed by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy.

Low-Cost Aqueous Electrolyte with MBA Additives for Uniform and Stable Zinc Deposition

Aqueous zinc ion batteries (AZIBs) are attracting increasing research interest due to their intrinsic safety, low cost, and scalability. However, the issues including hydrogen evolution, interface corrosion, and zinc dendrites at anodes have seriously limited the development of aqueous zinc ion batteries. Here, N,N-methylenebis(acrylamide) (MBA) additives with -CONH- groups are introduced to form hydrogen bonds with water and suppress H2O activity, inhibiting the occurrence of hydrogen evolution and corrosion reactions at the interface. In situ optical microscopy demonstrates that the MBA additive promotes the uniform deposition of Zn2+ and then suppresses the dendrite growth on the zinc anode. Therefore, Zn//Ti asymmetric batteries demonstrate a high plating/stripping efficiency of 99.5%, while Zn//Zn symmetric batteries display an excellent cycle stability for more than 1000 h. The Zn//MnO2 full cells exhibit remarkable cycling stability for 700 cycles in aqueous electrolytes with MBA additives. The additive engineering via MBA achieved the dendrite-free Zn anodes and stable full batteries, which is favorable for advanced AZIBs in practical applications.

Electrolyte Strategies Facilitating Anion-Derived Solid-Electrolyte Interphases for Aqueous Zinc-Metal Batteries

Rechargeable aqueous zinc-metal batteries (AZBs) are a promising complimentary technology to the existing lithium-ion batteries and the re-emerging lithium-metal batteries to satisfy the increasing demands on energy storage. Despite considerable progress achieved in the past years, the fundamental understanding of the solid-electrolyte interphase (SEI) formation and how its composition influences the SEI properties are limited. This review highlights the functionalities of anion-tuned SEI on the reversibility of zinc-metal anode, with a specific emphasis on new structural insights obtained through advanced characterizations and computational techniques. Recent efforts in terms of key variables that govern the interfacial behaviors to improve the long-term stability of zinc anode, i.e., Coulombic efficiency, plating morphology, dendrite formation, and side-reactions, are comprehensively reviewed. Lastly, the remaining challenges and future perspectives are presented, providing insights into the rational design of practical high-performance AZBs.

Gel polymer electrolytes for rechargeable batteries toward wide-temperature applications

Rechargeable batteries, typically represented by lithium-ion batteries, have taken a huge leap in energy density over the last two decades. However, they still face material/chemical challenges in ensuring safety and long service life at temperatures beyond the optimum range, primarily due to the chemical/electrochemical instabilities of conventional liquid electrolytes against aggressive electrode reactions and temperature variation. In this regard, a gel polymer electrolyte (GPE) with its liquid components immobilized and stabilized by a solid matrix, capable of retaining almost all the advantageous natures of the liquid electrolytes and circumventing the interfacial issues that exist in the all-solid-state electrolytes, is of great significance to realize rechargeable batteries with extended working temperature range. We begin this review with the main challenges faced in the development of GPEs, based on extensive literature research and our practical experience. Then, a significant section is dedicated to the requirements and design principles of GPEs for wide-temperature applications, with special attention paid to the feasibility, cost, and environmental impact. Next, the research progress of GPEs is thoroughly reviewed according to the strategies applied. In the end, we outline some prospects of GPEs related to innovations in material sciences, advanced characterizations, artificial intelligence, and environmental impact analysis, hoping to spark new research activities that ultimately bring us a step closer to realizing wide-temperature rechargeable batteries.

Rescuing zinc anode-electrolyte interface: mechanisms, theoretical simulations and in situ characterizations

The research interest in aqueous zinc-ion batteries (AZIBs) has been surging due to the advantages of safety, abundance, and high electrochemical performance. However, some technique issues, such as dendrites, hydrogen evolution reaction, and corrosion, severely prohibit the development of AZIBs in practical utilizations. The underlying mechanisms regarding electrochemical performance deterioration and structure degradation are too complex to understand, especially when it comes to zinc metal anode-electrolyte interface. Recently, theoretical simulations and in situ characterizations have played a crucial role in AZIBs and are exploited to guide the research on electrolyte engineering and solid electrolyte interphase. Herein, we present a comprehensive review of the current state of the fundamental mechanisms involved in the zinc plating/stripping process and underscore the importance of theoretical simulations and in situ characterizations in mechanism research. Finally, we summarize the challenges and opportunities for AZIBs in practical applications, especially as a stationary energy storage and conversion device in a smart grid.

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.

Fast Reaction Kinetics and Commendable Low-Temperature Adaptability of Zinc Batteries Enabled by Aprotic Water-Acetamide Symbiotic Solvation Sheath

Although rechargeable aqueous zinc batteries are cost effectiveness, intrinsicly safe, and high activity, they are also known for bringing rampant hydrogen evolution reaction and corrosion. While eutectic electrolytes can effectively eliminate these issues, its high viscosity severely reduces the mobility of Zn2+ ions and exhibits poor temperature adaptability. Here, we infuse acetamide molecules with Lewis base and hydrogen bond donors into a solvated shell of Zn[(H2 O)6 ]2+ to create Zn(H2 O)3 (ace)(BF4 )2 . The viscosity of 1ace-1H2 O is 0.032 Pa s, significantly lower than that of 1ace-0H2 O (995.6 Pa s), which improves ionic conductivity (9.56 mS cm-1 ) and shows lower freezing point of -45 °C, as opposed to 1ace-0H2 O of 4.04 mS cm-1 and 12 °C, respectively. The acidity of 1ace-1H2 O is ≈2.8, higher than 0ace-1H2 O at ≈0.76, making side reactions less likely. Furthermore, benefiting from the ZnCO3 /ZnF2 -rich organic/inorganic solid electrolyte interface, the Zn || Zn cells cycle more than 1300 hours at 1 mA cm-2 , and the Zn || Cu operated over 1800 cycles with an average Coulomb efficiency of ≈99.8 %. The Zn || PANI cell cycled over 8500 cycles, with a specific capacity of 99.8 mAh g-1 at 5 A g-1 at room temperature, and operated at -40 °C with a capacity of 66.8 mAh g-1 .

Recent advances in battery characterization using in situ XAFS, SAXS, XRD, and their combining techniques: From single scale to multiscale structure detection

Revealing and clarifying the chemical reaction processes and mechanisms inside the batteries will bring a great help to the controllable preparation and performance modulation of batteries. Advanced characterization techniques based on synchrotron radiation (SR) have accelerated the development of various batteries over the past decade. In situ SR techniques have been widely used in the study of electrochemical reactions and mechanisms due to their excellent characteristics. Herein, the three most wide and important synchrotron radiation techniques used in battery research were systematically reviewed, namely X-ray absorption fine structure (XAFS) spectroscopy, small-angle X-ray scattering (SAXS), and X-ray diffraction (XRD). Special attention is paid to how these characterization techniques are used to understand the reaction mechanism of batteries and improve the practical characteristics of batteries. Moreover, the in situ combining techniques advance the acquisition of single scale structure information to the simultaneous characterization of multiscale structures, which will bring a new perspective to the research of batteries. Finally, the challenges and future opportunities of SR techniques for battery research are featured based on their current development.

Electrolyte Additives for Stable Zn Anodes

Zn-ion batteries are regarded as the most promising batteries for next-generation, large-scale energy storage because of their low cost, high safety, and eco-friendly nature. The use of aqueous electrolytes results in poor reversibility and leads to many challenges related to the Zn anode. Electrolyte additives can effectively address many such challenges, including dendrite growth and corrosion. This review provides a comprehensive introduction to the major challenges in and current strategies used for Zn anode protection. In particular, an in-depth and fundamental understanding is provided of the various functions of electrolyte additives, including electrostatic shielding, adsorption, in situ solid electrolyte interphase formation, enhancing water stability, and surface texture regulation. Potential future research directions for electrolyte additives used in aqueous Zn-ion batteries are also discussed.

Smart Aqueous Zinc Ion Battery: Operation Principles and Design Strategy

The zinc ion battery (ZIB) as a promising energy storage device has attracted great attention due to its high safety, low cost, high capacity, and the integrated smart functions. Herein, the working principles of smart responses, smart self-charging, smart electrochromic as well as smart integration of the battery are summarized. Thus, this review enables to inspire researchers to design the novel functional battery devices for extending their application prospects. In addition, the critical factors associated with the performance of the smart ZIBs are comprehensively collected and discussed from the viewpoint of the intellectualized design. A profound understanding for correlating the design philosophy in cathode materials and electrolytes with the electrode interface is provided. To address the current challenging issues and the development of smart ZIB systems, a wide variety of emerging strategies regarding the integrated battery system is finally prospected.

Asymmetric Electrolytes Design for Aqueous Multivalent Metal Ion Batteries

With the rapid development of portable electronics and electric road vehicles, high-energy-density batteries have been becoming front-burner issues. Traditionally, homogeneous electrolyte cannot simultaneously meet diametrically opposed demands of high-potential cathode and low-potential anode, which are essential for high-voltage batteries. Meanwhile, homogeneous electrolyte is difficult to achieve bi- or multi-functions to meet different requirements of electrodes. In comparison, the asymmetric electrolyte with bi- or multi-layer disparate components can satisfy distinct requirements by playing different roles of each electrolyte layer and meanwhile compensates weakness of individual electrolyte. Consequently, the asymmetric electrolyte can not only suppress by-product sedimentation and continuous electrolyte decomposition at the anode while preserving active substances at the cathode for high-voltage batteries with long cyclic lifespan. In this review, we comprehensively divide asymmetric electrolytes into three categories: decoupled liquid-state electrolytes, bi-phase solid/liquid electrolytes and decoupled asymmetric solid-state electrolytes. The design principles, reaction mechanism and mutual compatibility are also studied, respectively. Finally, we provide a comprehensive vision for the simplification of structure to reduce costs and increase device energy density, and the optimization of solvation structure at anolyte/catholyte interface to realize fast ion transport kinetics.

Constructing Solid Electrolyte Interphase for Aqueous Zinc Batteries

Problems of zinc anode including dendrite and hydrogen evolution seriously degrade the performance of zinc batteries. Solid electrolyte interphase (SEI), which plays a key role in achieving high reversibility of lithium anode in aprotic organic solvent, is also beneficial to performance improvement of zinc anode in aqueous electrolyte. However, various studies about interphase for zinc electrode is quite fragmented, and lack of deep understanding on root causes or general design rules for SEI construction. And water molecules with high reactivity brings serious challenge to the effective SEI construction. Here, we reviewed the brief development history of zinc batteries firstly, then summarized the approaches to construct SEI in aqueous electrolyte. Furthermore, the formation mechanisms behind approaches are systematically analyzed, together with discussion on the SEI components and evaluation on electrochemical performance of zinc anode with various types of SEI. Meanwhile, the challenge between lab and industrialization are also discussed.

An Electrochemical Perspective of Aqueous Zinc Metal Anode

Based on the attributes of nonflammability, environmental benignity, and cost-effectiveness of aqueous electrolytes, as well as the favorable compatibility of zinc metal with them, aqueous zinc ions batteries (AZIBs) become the leading energy storage candidate to meet the requirements of safety and low cost. Yet, aqueous electrolytes, acting as a double-edged sword, also play a negative role by directly or indirectly causing various parasitic reactions at the zinc anode side. These reactions include hydrogen evolution reaction, passivation, and dendrites, resulting in poor Coulombic efficiency and short lifespan of AZIBs. A comprehensive review of aqueous electrolytes chemistry, zinc chemistry, mechanism and chemistry of parasitic reactions, and their relationship is lacking. Moreover, the understanding of strategies for suppressing parasitic reactions from an electrochemical perspective is not profound enough. In this review, firstly, the chemistry of electrolytes, zinc anodes, and parasitic reactions and their relationship in AZIBs are deeply disclosed. Subsequently, the strategies for suppressing parasitic reactions from the perspective of enhancing the inherent thermodynamic stability of electrolytes and anodes, and lowering the dynamics of parasitic reactions at Zn/electrolyte interfaces are reviewed. Lastly, the perspectives on the future development direction of aqueous electrolytes, zinc anodes, and Zn/electrolyte interfaces are presented.

Amino-Functionalized Interfacial Layer Enables an Ultra-Uniform Amorphous Solid Electrolyte Interphase for High-Performance Aqueous Zinc-Based Batteries

Aqueous rechargeable zinc-based batteries (ZBBs) are emerging as desirable energy storage systems because of their high capacity, low cost, and inherent safety. However, the further application of ZBBs still faces many challenges, such as the issues of uncontrolled dendrite growth and severe parasitic reactions occurring at the Zn anode. Herein, an amino-grafted bacterial cellulose (NBC) film is prepared as artificial solid electrolyte interphase (SEI) for the Zn metal anodes, which can significantly reduce zinc nucleation overpotential and lead to the dendrite-free deposition of Zn metal along the (002) crystal plane more easily without any external stimulus. More importantly, the chelation between the modified amino groups and zinc ions can promote the formation of an ultra-even amorphous SEI upon cycling, reducing the activity of hydrate ions, and inhibiting the water-induced side reactions. As a result, the Zn||Zn symmetric cell with NBC film exhibits lower overpotential and higher cyclic stability. When coupled with the V2 O5 cathode, the practical pouch cell achieves superior electrochemical performance over 1000 cycles.

Hydrogel Electrolyte Enabled High-Performance Flexible Aqueous Zinc Ion Energy Storage Systems toward Wearable Electronics

To cater to the swift advance of flexible wearable electronics, there is growing demand for flexible energy storage system (ESS). Aqueous zinc ion energy storage systems (AZIESSs), characterizing safety and low cost, are competitive candidates for flexible energy storage. Hydrogels, as quasi-solid substances, are the appropriate and burgeoning electrolytes that enable high-performance flexible AZIESSs. However, challenges still remain in designing suitable and comprehensive hydrogel electrolyte, which provides flexible AZIESSs with high reversibility and versatility. Hence, the application of hydrogel electrolyte-based AZIESSs in wearable electronics is restricted. A thorough review is required for hydrogel electrolyte design to pave the way for high-performance flexible AZIESSs. This review delves into the engineering of desirable hydrogel electrolytes for flexible AZIESSs from the perspective of electrolyte designers. Detailed descriptions of hydrogel electrolytes in basic characteristics, Zn anode, and cathode stabilization effects as well as their functional properties are provided. Moreover, the application of hydrogel electrolyte-based flexible AZIESSs in wearable electronics is discussed, expecting to accelerate their strides toward lives. Finally, the corresponding challenges and future development trends are also presented, with the hope of inspiring readers.

Strategies for Optimizing the Zn Anode/Electrolyte Interfaces Toward Stable Zn-Based Batteries

Aqueous rechargeable Zn-ion batteries (ARZIBs) have attracted extensive attention because of the advantages of high energy density, high safety, and low cost. However, the commercialization of ARZIBs is still challenging, mainly because of the low efficiency of Zn anodes. Several undesirable reactions (e.g., Zn dendrite and byproduct formation) always occur at the Zn anode/electrolyte interfaces, resulting in low Coulombic efficiency and rapid decay of ARZIBs. Motivated by the great interest in addressing these issues, various optimization strategies and related mechanisms have been proposed to stabilize the Zn anode-electrolyte interfaces and enlengthen the cycling lifespan of ARZIBs. Therefore, considering the rapid development of this field, updating the optimization strategies in a timely manner and understanding their protection mechanisms are highly necessary. This review provides a brief overview of the Zn anode/electrolyte interfaces from the fundamentals and challenges of Zn anode chemistry to related optimization strategies and perspectives. Specifically, these strategies are systematically summarized and classified, while several representative works are presented to illustrate the effect and corresponding mechanism in detail. Finally, future challenges and research directions for the Zn anode/electrolyte interfaces are comprehensively clarified, providing guidelines for accurate evaluation of the interfaces and further fostering the development of ARZIBs.

Recent Research Progress into Zinc Ion Battery Solid-Electrolyte Interfaces

Aqueous zinc ion batteries (ZIBs) are prospective next-generation energy storage device candidates owing to resource abundance, affordability, eco-friendliness, and safety. The solid-electrolyte interface (SEI) produced in a ZIB by electrolyte/electrode interactions significantly impacts battery performance. The SEI is known to promote dendrite growth, determine the electrochemical stability window, passivate zinc-metal-anodic corrosion, and mutate the electrolyte. Accordingly, the SEI is closely related to the overall property of a ZIB device. This review provides an overview of the impact of SEIs on ZIB performance recently and provides an SEI design strategy based on the formation mechanism, type, and characteristics of the SEI. Finally, future investigational directions for SEIs in ZIBs are expected to lead to a deep understanding of the SEI, enhance ZIB performance, and facilitate their extensive implementation.

Self-Discharge Processes in Symmetrical Supercapacitors with Activated Carbon Electrodes

The self-discharge of an electric double-layer capacitor with composite activated carbon electrodes and aqueous electrolyte (1 M MgSO4) was studied in detail. Under a long-term potentiostatic charge (stabilization), a decrease in the discharge capacity was observed in the region of voltages exceeding 0.8 V. The self-discharge process consists of two phases. In the initial phase, the cell voltage drop is due to the charge redistribution inside electrodes. During the main phase, the charge transfer between the electrodes determines the voltage drop. The optimal stabilization time of the self-discharge was found to be 50 min at 1.4 V. Hydrophilization of the negative electrode occurred during long-term polarization due to the formation of epoxy functional groups.

Zinc-Bromine Rechargeable Batteries: From Device Configuration, Electrochemistry, Material to Performance Evaluation

Zinc-bromine rechargeable batteries (ZBRBs) are one of the most powerful candidates for next-generation energy storage due to their potentially lower material cost, deep discharge capability, non-flammable electrolytes, relatively long lifetime and good reversibility. However, many opportunities remain to improve the efficiency and stability of these batteries for long-life operation. Here, we discuss the device configurations, working mechanisms and performance evaluation of ZBRBs. Both non-flow (static) and flow-type cells are highlighted in detail in this review. The fundamental electrochemical aspects, including the key challenges and promising solutions, are discussed, with particular attention paid to zinc and bromine half-cells, as their performance plays a critical role in determining the electrochemical performance of the battery system. The following sections examine the key performance metrics of ZBRBs and assessment methods using various ex situ and in situ/operando techniques. The review concludes with insights into future developments and prospects for high-performance ZBRBs.

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

The last several years have witnessed the prosperous development of zinc-ion batteries (ZIBs), which are considered as a promising competitor of energy storage systems thanks to their low cost and high safety. However, the reversibility and availability of this system are blighted by problems such as uncontrollable dendritic growth, hydrogen evolution, and corrosion passivation on anode side. A functionally and structurally well-designed anode current collectors (CCs) is believed as a viable solution for those problems, with a lack of summarization according to its working mechanisms. Herein, this review focuses on the challenges of zinc anode and the mechanisms of modified anode CCs, which can be divided into zincophilic modification, structural design, and steering the preferred crystal facet orientation. The possible prospects and directions on zinc anode research and design are proposed at the end to hopefully promote the practical application of ZIBs.

Aqueous Zinc Batteries with Ultra-Fast Redox Kinetics and High Iodine Utilization Enabled by Iron Single Atom Catalysts

Rechargeable aqueous zinc iodine (ZnǀǀI2) batteries have been promising energy storage technologies due to low-cost position and constitutional safety of zinc anode, iodine cathode and aqueous electrolytes. Whereas, on one hand, the low-fraction utilization of electrochemically inert host causes severe shuttle of soluble polyiodides, deficient iodine utilization and sluggish reaction kinetics. On the other hand, the usage of high mass polar electrocatalysts occupies mass and volume of electrode materials and sacrifices device-level energy density. Here, we propose a "confinement-catalysis" host composed of Fe single atom catalyst embedding inside ordered mesoporous carbon host, which can effectively confine and catalytically convert I2/I- couple and polyiodide intermediates. Consequently, the cathode enables the high capacity of 188.2 mAh g-1 at 0.3 A g-1, excellent rate capability with a capacity of 139.6 mAh g-1 delivered at high current density of 15 A g-1 and ultra-long cyclic stability over 50,000 cycles with 80.5% initial capacity retained under high iodine loading of 76.72 wt%. Furthermore, the electrocatalytic host can also accelerate the [Formula: see text] conversion. The greatly improved electrochemical performance originates from the modulation of physicochemical confinement and the decrease of energy barrier for reversible I-/I2 and I2/I+ couples, and polyiodide intermediates conversions.

Interfacial Engineering Boosts Highly Reversible Zinc Metal for Aqueous Zinc-Ion Batteries

Zinc metal is emerging as the promising anode for aqueous Zn-ion batteries. However, corrosion and undesirable Zn dendrite growth limit their practical application in the large-scale energy storage area. Herein, a mountain-valley micro/nanostructure is successfully fabricated on the surface of the Zn anode via a femtosecond-laser filament texturing (FsLFT) technique. Beneficial from the large surface area and spontaneously generated ZnO coating layer, the FsLFT-Zn electrode demonstrates a slow corrosion rate with a current density of 0.62 mA cm^-2 and a stable cycle life over 3000 h under 1 mA cm^-2, superior to the original Zn anode. Simulation of the electric fields reveals that the enlarged surface area is responsible for the outstanding performance of the FsLFT-Zn electrode. This study not only proposes a novel strategy to suppress dendrite growth toward highly stable AZIBs but also opens a new avenue to solve similar issues in other metal batteries.

Quasi-Solid Electrolyte Interphase Boosting Charge and Mass Transfer for Dendrite-Free Zinc Battery

The practical applications of zinc metal batteries are plagued by the dendritic propagation of its metal anodes due to the limited transfer rate of charge and mass at the electrode/electrolyte interphase. To enhance the reversibility of Zn metal, a quasi-solid interphase composed by defective metal-organic framework (MOF) nanoparticles (D-UiO-66) and two kinds of zinc salts electrolytes is fabricated on the Zn surface served as a zinc ions reservoir. Particularly, anions in the aqueous electrolytes could be spontaneously anchored onto the Lewis acidic sites in defective MOF channels. With the synergistic effect between the MOF channels and the anchored anions, Zn2+ transport is prompted significantly. Simultaneously, such quasi-solid interphase boost charge and mass transfer of Zn2+, leading to a high zinc transference number, good ionic conductivity, and high Zn2+ concentration near the anode, which mitigates Zn dendrite growth obviously. Encouragingly, unprecedented average coulombic efficiency of 99.8% is achieved in the Zn||Cu cell with the proposed quasi-solid interphase. The cycling performance of D-UiO-66@Zn||MnO2 (~ 92.9% capacity retention after 2000 cycles) and D-UiO-66@Zn||NH4V4O10 (~ 84.0% capacity retention after 800 cycles) prove the feasibility of the quasi-solid interphase.

Novel LiAlO2 Material for Scalable and Facile Lithium Recovery Using Electrochemical Ion Pumping

In this study, α-LiAlO₂ was investigated for the first time as a Li-capturing positive electrode material to recover Li from aqueous Li resources. The material was synthesized using hydrothermal synthesis and air annealing, which is a low-cost and low-energy fabrication process. The physical characterization showed that the material formed an α-LiAlO₂ phase, and electrochemical activation revealed the presence of AlO₂* as a Li deficient form that can intercalate Li⁺. The AlO₂*/activated carbon electrode pair showed selective capture of Li⁺ ions when the concentrations were between 100 mM and 25 mM. In mono salt solution comprising 25 mM LiCl, the adsorption capacity was 8.25 mg g^-1, and the energy consumption was 27.98 Wh mol Li^-1. The system can also handle complex solutions such as first-pass seawater reverse osmosis brine, which has a slightly higher concentration of Li than seawater at 0.34 ppm.