Inhibition of Vanadium Cathodes Dissolution in Aqueous Zn-Ion Batteries

A bioimmune mechanism-inspired targeted elimination mechanism on the anode interface for zinc-iodine batteries

Alkaline byproducts at the zinc anode interface continue to exacerbate subsequent side reactions, so realizing timely salvage of electrodes is equally important compared to upfront prevention strategies. Although the utilization of acid electrolytes could eliminate by-products on the Zn anode, they inevitably exacerbate the undesired hydrogen evolution reaction. Therefore, achieving elimination of by-products without exacerbating other side reactions is urgently needed. Inspired by the immune protection mechanisms in organisms, facile cysteamine hydrochloride (Cy-H) additives were incorporated into the aqueous electrolyte to stabilize the anode. Concretely, the Cy-H additives can reconstruct the electrical double layer (EDL) on the Zn anode and inhibit drastic parasitic reactions and cooperate with electric fields and acidic environments, thus achieving the desired effect of targeted elimination of alkaline by-products. Ultimately, with a long calendar lifespan of 2000 h with a Zn anode carrying by-products and outstanding performance over 8000 cycles for the Zn‖I2 full cell, the assembled pouch battery also achieved 1000 cycles without capacity degradation. To further promote the practical applications, the inhibition mechanism of Cy-H additives on full-cell self-discharge was revealed. This work provides new insights for the use of strong acid electrolytes and the elimination of interfacial by-products in aqueous zinc-iodine batteries.

Layered Potassium Vanadate K0.5V2O5 as a Robust Cathode Material for Aqueous Zinc-Ion Batteries

Layered vanadates are promising cathode materials for aqueous zinc-ion batteries (AZIBs). Herein, a layered potassium vanadate K0.5V2O5 is reported as a promising cathode material for AZIBs. It provides a high reversible capacity of 471.1 mAh g-1 with unprecedent cycle life at a harsh low rate of 0.21 C (90.2% capacity retention after 400 cycles, running time 150 days), remarkable rate capability and decent long-term cycling stability (no capacity decay after 1700 cycles). According to a series of tests, it is revealed that the energy storage mechanism of K0.5V2O5 involves initial extraction of K+ followed by subsequent (de)intercalation of Zn2+/H+, in which the concomitant structure change and chemical state transition of vanadium possess high reversibility. Moreover, K0.5V2O5 exhibits rapid Zn2+/H+ ion diffusion, favoring its rate capability. Additionally, K0.5V2O5 also demonstrates excellent low-temperature adaptability, which can operate stably at -30 °C. The excellent electrochemical performance, facile preparation, and low cost of K0.5V2O5 promise it as an attractive cathode candidate for practical AZIBs.

Eliminating the "Dead By-Product" Effect Realizes Powerful Vanadium-Based Zinc-Ion Batteries: An Overlooked Case

The accumulation of inactive by-products caused by the parasitic side reaction on cathode side is an overlooked question leading to performance degradation of zinc-ion batteries. In this research, taking the MnV2O4 as a model, an amorphous carbon interphase is proposed as a pre-implanted cathode-electrolyte interphase (CEI) to design ultrafast-kinetics MnV2O4@C cathode. It is noted that such CEI integrates hydrophobic and conductive characteristics, contributing to dissolution shielding, continuous interfacial conductive channel, and thus preventing inactive by-product accumulation on the cathode interface. Unexpectedly, such electrode shows superior storage performance at a wide temperature range of -20-55 °C. It can deliver a specific capacity of 253.3 mAh g-1 at the high current density of 10 A g-1 even after 8000 cycles. Moreover, a high specific capacity of 393.8 mAh g-1 (0.1 A g-1) can be retained after 300 cycles at 55 °C, as well as 205.1 mAh g-1 at the condition of -20 °C and 5 A g-1. Beyond that, flexible solid-state zinc-ion batteries based on MnV2O4@C cathode with excellent wide temperature performance are demonstrated. This work highlights the importance of eliminating the dead by-product effect to design advanced cathode materials for zinc-ion batteries.

Critical issues and optimization strategies of vanadium dioxide-based cathodes towards high-performance aqueous Zn-ion batteries

Aqueous zinc-ion batteries (AZIBs) are gaining significant attention due to their excellent safety, cost-effectiveness, and environmental friendliness, making them highly competitive energy storage solutions. Despite these advantages, the commercial application of AZIBs faces substantial challenges, particularly those related to performance limitations of cathode materials. Among potential candidates, vanadium dioxide (VO2) stands out due to its exceptional electrochemical properties and unique crystal structure, rendering it a promising cathode material for AZIB applications. The review summarizes the recent research progress on VO2 in AZIBs, analyzes its crystal structures (tetragonal VO2(A), monoclinic VO2(B, D, M), and rutile VO2(R)), morphology and energy storage mechanisms (Zn2+ insertion/extraction, H+/Zn2+ co-insertion/extraction, and chemical reaction mechanism), and discusses the relationship between the structure and performance. The review also addresses key challenges associated with VO2 as a cathode material, including dissolution, by-product formation, and limited ion diffusion kinetics. To overcome these issues, various optimization strategies are systematically discussed, such as ion/molecule pre-intercalation, composite material fabrication, defect engineering, and elemental doping. Finally, potential research directions and strategies to further enhance the performance and commercial viability of VO2-based cathodes are proposed.

Anion-endowed high-dielectric water-deficient interface towards ultrastable Zn metal batteries

To achieve reversible metallic Zn anodes for aqueous rechargeable zinc batteries, regulating the electrolyte-Zn interface is the key to addressing the side reactions on Zn. Beyond water-deficiency, design rules for constructing the highly efficient electrochemical interface are still vague. Anions, as primary electrolyte constituents, not only play a role in solvation structure, but also influence the electrolyte-Zn interface. Here, the characteristics of representative anions in current aqueous zinc electrolytes are surveyed. A candidate combining polarizability, H-bond tuning ability and high solubility is proposed to construct a high-dielectric water-deficient electrolyte-Zn interface to regulate the interfacial chemistry on Zn. The anion-dominated electrochemical interface promotes the Zn deposition kinetics and achieves uniform Zn deposition with high stability, which further enables the in situ formation of an SEI for highly stable Zn stripping/plating, e.g., at 20 mA cm-2 and 20 mA h cm-2. Furthermore, this built-in interface exhibits an effect in stabilizing the V2O5 cathode, endowing the V2O5/Zn cell with ultra-stable long-term cycling, e.g., 10 000 cycles at 10 A g-1 with a high retention rate of 89.7%. Our design offers insight into guidelines for the development of novel electrolytes towards rationally designed electrochemical interfaces.

Surface- and interlayer-modified ammonium vanadate cathode for high-performance aqueous Zn-ion batteries

Vanadium-based compounds suffer from the poor intrinsic conductivity, unstable structure, and sluggish reaction kinetics as the cathode materials for aqueous zinc ion batteries. In this work, conductive polymer (polypyrrole, PPy) coating/pre-intercalation is proposed to achieve stable and reversible Zn2+ storage in ammonium vanadates (NH4V4O10, NVO). The PPy coating on the surface of the NVO nanobelts effectively suppresses material dissolution, and promotes the desolvation of hydrated zinc ions at the interface. The intercalated PPy within the layered structure expands the interlayer spacing, induces the formation of oxygen vacancies, and increases the electronic conductivity, thus accelerating zinc ion diffusion and electron transport kinetics. Benefiting from simultaneous optimization of the surface and interlayer structure, the PPy-NVO electrode demonstrates outstanding electrochemical properties, delivering a high discharge capacity of 455mAh g-1 at 0.1 A g-1 and 250mAh g-1 at 5 A g-1, maintaining 89 % of its initial capacity after 2500 cycles at 4 A g-1. Ex situ characterization techniques demonstrate the reversible Zn ions insertion/extraction storage mechanism in the PPy-NVO cathode.

Imaging the 4D Chemical Heterogeneity of Single V2O5 Particles During Charging/Discharging Processes

Microparticle cathode materials are widely used in secondary batteries. However, obtaining dynamic chemical heterogeneities of these microparticles is challenging, hindering in-depth mechanistic investigation of the underlying processes. For example, although vanadium pentoxide shows promise as an electrode material for zinc ion batteries, its poor performance's root cause is elusive. Herein, a fluorescence/scattering dual-mode spinning disk confocal microscopy-based approach is developed to visualize the 4D chemical heterogeneity of single V2O5 particles during cycling. Dual-mode in situ imaging identifies valence state changes of vanadium ions with high spatiotemporal resolution. A unique difference is observed between the scattering intensities of a particle's bottom electric contact points and the rest parts during the discharging process. In contrast, fluorescence intensity variation suggests high consistency across the particles. Correlative Raman, UV-Vis spectroscopy, and electrochemical impedance spectroscopy analyses suggest the precipitation of V3+ species at the bottom interface of the V2O5 electrode, leading to increased electron transfer resistance and compromised overall performance. A coordination strategy between ethylene diamine tetraacetic acid and V3+ is proposed for inhibiting V3+ precipitation, and its effectiveness is further verified by imaging and electrochemical impedance spectroscopy analyses. Insights from the imaging approach presented herein will enable the rational design of high-performance batteries.

Bilateral in-situ functionalization towards Ah-scale aqueous zinc metal batteries

Developing practical technical index of aqueous zinc metal batteries (ZMBs) is crucial to support safe large-scale energy storage. However, the realistic performance demonstration of ampere hour (Ah)-scale aqueous ZMBs under high mass loading and large areal capacity, which is the key to the industrial application of aqueous ZMBs, remains a critical challenge. In this paper, we propose a bilateral in-situ functionalization strategy in response to the issues that face high mass loading and large areal capacity of aqueous ZMBs. A gradient interface of Zn negative electrode was formed by directional adsorption and in-situ decomposition of organic sodium salt electrolyte additive. It avoids the influences from the fluctuation of electrolyte state and positive electrode dissolution, realizing uniform large-capacity plating/stripping in Ah-scale pouch cell. The positive electrode interface was also in-situ modified by electrolyte additive, which not only facilitated ion intercalation but also suppressed positive electrode dissolution through adsorption at the interface, thereby achieving high-loading stability. As a result, the cyclic stability in coin cell maintained more than 4000 cycles at 2 A g-1, underscoring the superior compared to its counterpart. More importantly, the Ah-scale pouch cell can last more than 680 cycles with an accumulated capacity of 319.6 Ah. This work offers a roadmap for designing practical Ah-scale ZMB pouch cells.

A Comprehensive Strategy Enables High-Loading BiOBr@BiOIO3 Cathodes for Quasi Ah-Level Aqueous Zn-Ion Batteries

Aqueous Zn-ion batteries (AZIBs) recently have attracted broad attention. To achieve high energy density of AZIBs, constructing high-loading cathodes is the prerequisite. However, the cycling stability of high-loading cathodes still faces great challenges. Herein, a comprehensive strategy is proposed to improve the structural stability of the cathode material and mechanical stability of the high-loading cathode. The BiOBr@BiOIO3 heterostructure are successfully constructed via sharing the interfacial oxygen atoms, in which the interfacial effect can effectively enhance the reaction dynamics and structural stability. Meanwhile, a biomimetic binder is skillfully designed via in situ dual cross-linking between guar gum and cation ions to achieve the application of water-based and sustainable polymer binder in AZIBs. Density functional theory calculations demonstrate the guar gum possesses strong affinity toward BiOBr@BiOIO3 to firmly adhere the active materials. Quantitative nanomechanic technology visually demonstrates the robust mechanical properties of the as-obtained BiOBr@BiOIO3 cathode. As a result, when the active material loading increases to as high as 100.71 mg cm-2, an ultrahigh areal capacity of 20.02 mAh cm-2 can be achieved. Specially, a quasi-Ah-level (0.244 Ah) pouch-type cell with a loading of 1.17 g can be constructed, showing the practical application potential.

Aqueous Biphasic Electrolyte Enabling Self-Adaptation of Mutually Exclusive Electrolyte Requirements for a Zn Anode and a Cathode

Aqueous Zn-based batteries, the coupling of a zinc anode and a cathode in aqueous electrolytes, are promising for large-scale energy storage. However, the preference of these two electrodes in aqueous zinc sulfate electrolytes with different concentrations exhibits inherent contradictions, which are enhanced rapidly at increased temperatures, impeding their sustainable applications. Herein, we took a zinc metal anode and a vanadium-based cathode as an example and developed an aqueous biphasic electrolyte (ABE) that utilized the distinct ion concentration contrast characteristics between the two phases to simultaneously fulfill the mutually exclusive environmental requirements for cathodes and anodes. The ABE substantially improved the stability of the full battery, which demonstrated a stable cycling performance for up to 1000 cycles at a current density of 5 A g-1 at an increased temperature of 60 °C. A battery prototype with high-voltage output and energy expandability was also developed, providing a promising model for future large-scale applications of ABEs.

Construction of high-performance aqueous zinc-ion batteries by guest pre-intercalation MnO2-based cathodes

In recent years, aqueous zinc ion batteries (AZIBs) with the benefits of high safety, low cost, high capacity and environmental protection, have broad development prospects in the area of massive energy storage. Among them, MnO2 materials are seen to be the most prospective cathode materials because of their low manufacturing costs, high operating voltage, and multi-valence state. Nevertheless, issues with low intrinsic conductivity, quick structural collapse and poor stability of MnO2 cathode materials during the charge/discharge process severely impede the development of AZIBs. Numerous investigations have demonstrated that the guest pre-intercalation MnO2 cathode structures can effectively alleviate the above problems and improve their electrochemical performance. Thus, this review summarizes the research progress of the guest pre-intercalation strategy applied to different Mn-based oxide cathode materials, focusing on α-MnO2, β-MnO2, ε-MnO2, δ-MnO2, and γ-MnO2. Meanwhile, the mechanism of performance improvement and electronic structure alteration of guest pre-intercalation in MnO2 cathode materials with different crystal structures are analyzed in detail. Finally, the challenges faced by this strategy and its development are summarized, and the future development direction of Mn-based cathode materials for high-performance AZIBs is prospected. The review describes the guest pre-intercalation strategy that promotes the commercialization and practical application of AZIBs, providing strong support for the development of renewable energy storage.

Electrolyte Decoupling Strategy for Metal Oxide-Based Zinc-Ion Batteries Free of Crosstalk Effect

The crosstalk of transition metal ions between the metal oxide cathode and Zn anode restricts the practical applications of aqueous zinc-ion batteries (ZIBs). Herein, we propose a decoupled electrolyte (DCE) consisting of a nonaqueous-phase (N-phase) anolyte and an aqueous-phase (A-phase) catholyte to prevent the crosstalk of Mn2+, thus extending the lifespan of MnO2-based ZIBs. Experimental measurements and theoretical modelling verify that trimethyl phosphate (TMP) not only synergistically works with NH4Cl in the N-phase anolyte to enable fast Zn2+ conduction while blocking Mn2+ diffusion toward anode, but also modifies the Zn2+ solvation structure to suppress the dendrite formation and corrosion on Zn anode. Meanwhile, the A-phase catholyte effectively accelerates the cathode reaction kinetics. The as-developed Zn|DCE|MnO2 cell delivers 80.13 % capacity retention after 900 cycles at 0.5 A g-1. This approach is applicable for other metal oxide cathode-based ZIBs, thereby opening a new avenue for developing ultrastable ZIBs.

Exploring interfacial electrocatalysis for iodine redox conversion in zinc-iodine battery

The challenges posed by the non-conductive nature of iodine, coupled with the easy formation of soluble polyiodides in water, impede its integration with zinc for the development of advanced rechargeable batteries. Here we demonstrate the in-situ loading of molybdenum carbide nanoclusters (MoC) and zinc single atoms (Zn-SA) into porous carbon fibers to invoke electrocatalytic conversion of iodine at the interface. The electronic interactions between MoC and Zn-SA lead to an upshift in the d-band center of Mo relative to the Fermi level, thus promoting the interfacial interactions with iodine species to suppress shuttle effects. Notably, the optimal charge delocalization, induced by d-p orbital hybridization between molybdenum and iodine, also lowers the redox energy barrier to promote the interfacial conversion. With interfacial electrocatalysis minimizing polyiodide intermediates via a favorable redox conversion pathway, zinc-iodine batteries therefore demonstrate a large specific capacity of 230.6 mAh g-1 and the good capacity retention for 20,000 cycles.

Hydrogen/Electron Amphiphilic Bi-Functional Water Molecular Inactivator-Assisted Interface Stabilization in Highly Reversible Zn Metal Batteries

Continuous hydrogen-bond-network in aqueous electrolytes can lead to uncontrollable hydrogen transfer, and combining the interfacial parasitic electron consumption cause the side reaction in aqueous zinc metal batteries (AZMBs). Herein, hydrogen/electron amphiphilic bi-functional 1,5-Pentanediol (PD) molecule was introduced to stabilize the electrode/electrolyte interface. Stronger proton affinity of -OH in PD can break bulk-H2O hydrogen-bond-network to inhibit the activity of water, and electron affinity can enhance electron acceptation capability, which ensures that PD is preferentially bound to electrode material over H2O. Besides, the participation of PD in the Zn2+ solvation structure reduces water content at the solid-liquid interface and promotes uniform deposition process by optimizing Zn2+ de-solvation energy. Accordingly, dense and vertical zinc texture based on intrinsic steric hindrance effect of PD and formed SEI protective layer to induce stable Zinc anode-electrolyte interface. Moreover, an organic-inorganic shielding water layer was formed at the cathode side to suppress vanadium dissolution in vanadium Oxide. Consequently, Zn//Zn symmetric cell could cycle for more than 5600 hours at 1 mAh cm-2@1 mA cm-2 (more than 250 hours at 50 °C). Besides, the VO2 and I2 cathode all achieved stable cycling performance and former pouch cell could reach average capacity of 0.13 Ah.

Sandwich-Like MXene@Mn3O4@PPy Hollow Microspheres Synergistically Enabled Ultra-long Cycling Life in Aqueous Zinc Ion Batteries

Manganese-based oxides are be regarded as one of the most promising cathode materials for aqueous zinc ion batteries (AZIBs). A major restriction of manganese-based oxides in practical applications is their unsatisfied structural stability due to the irreversible manganese dissolution. Additionally, the poor electrical conductivity also limits the rate capability. Herein, the sandwich-like MXene@Mn3O4@PPy hollow microspheres are constructed via self-sacrificial template and surface coating method to improve the cycling life of AZIBs. Benefiting from the unique sandwich-like hollow structure and the surface coating of PPy, the MXene@Mn3O4@PPy cathode possesses high electronic/ionic conductivity and satisfied structural stability. The sandwich-like MXene@Mn3O4@PPy hollow microspheres deliver excellent electrochemical performance, including an impressive rate capability and ultra-long cycling life with a capacity of 120 mAh g-1 at 5 A g-1 after 9000 cycles. In addition, the systematic ex situ XRD and HRTEM characterizations verify the highly reversible Zn2+ and H+ insertion/desertion in the sandwich-like MXene@Mn3O4@PPy hollow microspheres. This work combines hollow structure design and surface coating method to provide an effective strategy for improving the structural stability of manganese-based oxides in AZIBs.

NH4+-Modulated Cathodic Interfacial Spatial Charge Redistribution for High-Performance Dual-Ion Capacitors

Compared with Zn2+, the current mainly reported charge carrier for zinc hybrid capacitors, small-hydrated-sized and light-weight NH4+ is expected as a better one to mediate cathodic interfacial electrochemical behaviors, yet has not been unraveled. Here we propose an NH4+-modulated cationic solvation strategy to optimize cathodic spatial charge distribution and achieve dynamic Zn2+/NH4+ co-storage for boosting Zinc hybrid capacitors. Owing to the hierarchical cationic solvated structure in hybrid Zn(CF3SO3)2-NH4CF3SO3 electrolyte, high-reactive Zn2+ and small-hydrate-sized NH4(H2O)4+ induce cathodic interfacial Helmholtz plane reconfiguration, thus effectively enhancing the spatial charge density to activate 20% capacity enhancement. Furthermore, cathodic interfacial adsorbed hydrated NH4+ ions afford high-kinetics and ultrastable C‧‧‧H (NH4+) charge storage process due to a much lower desolvation energy barrier compared with heavy and rigid Zn(H2O)62+ (5.81 vs. 14.90 eV). Consequently, physical uptake and multielectron redox of Zn2+/NH4+ in carbon cathode enable the zinc capacitor to deliver high capacity (240 mAh g-1 at 0.5 A g-1), large-current tolerance (130 mAh g-1 at 50 A g-1) and ultralong lifespan (400,000 cycles). This study gives new insights into the design of cathode-electrolyte interfaces toward advanced zinc-based energy storage.

Synergistic Regulation of Anode and Cathode Interphases via an Alum Electrolyte Additive for High-Performance Aqueous Zinc-Vanadium Batteries

A zinc (Zn) metal anode paired with a vanadium oxide (VOx) cathode is a promising system for aqueous Zn-ion batteries (AZIBs); however, side reactions proliferating on the Zn anode surface and the infinite dissolution of the VOx cathode destabilise the battery system. Here, we introduce a multi-functional additive into the ZnSO4 (ZS) electrolyte, KAl(SO4)2 (KASO), to synchronise the in situ construction of the protective layer on the surface of the Zn anode and the VOx cathode. Theoretical calculations and synchrotron radiation have verified that the high-valence Al3+ plays dual roles of competing with Zn2+ for solvation and forming a Zn-Al alloy layer with a homogeneous electric field on the anode surface to mitigate the side reactions and dendrite generation. The Al-containing cathode-electrolyte interface (CEI) considerably alleviates the irreversible dissolution of the VOx cathode and the accumulation of byproducts. Consequently, the Zn||Zn cell with KASO exhibits an ultra-long cycle of 6000 h at 2 mA cm-2. Importantly, the VOx cathodes (VO2, V2O5 and NH4V4O10) in the ZS-KASO electrolyte showed excellent cycling stability, including Zn powder||VO2 cells and Zn||VO2 pouch cells. Even better, the full cell exhibits excellent cycling stability at low negative/positive (N/P) ratio of 2.83 and high mass loading (~16 mg cm-2). This study offers a straightforward and practical reference for concurrently addressing challenges at the anode and cathode of AZIBs.

Emulating "Curvature-Enhanced Adsorbate Coverage" for Superconformal and Orientated Zn Electrodeposition in Zinc-ion-Batteries

Uneven Zn deposition and unfavorable side reactions have prevented the reversibility of the Zn anode. Herein, we design a rearranged (002) textured Zn anode inspired by a traditional curvature-enhanced adsorbate coverage (CEAC) process to realize the highly reversible Zn anode. The rearranged (002) textured structure directs superconformal Zn deposition by controlling the spatial deposition rate of the rearranged crystal planes, thereby promoting bottom-up "superfilling" of the 3D Zn skeletons. Meanwhile, our designed anode also induces the epitaxial Zn deposition, alleviating the parasitic reactions owing to the lowest surface energy of the (002) plane. Attributed to these superiorities, uniform and oriented Zn deposition can be obtained, exhibiting an ultra-long lifespan over 479 hrs at an ultrahigh depth of discharge (DOD) of 82.12 %. The Zn|Na2V6O16 ⋅ 3H2O battery delivers an improved cycling performance, even at a high area capacity of 5.15 mAh/cm2 with a low negative/positive (N/P) capacity ratio of 1.63. The superconformal deposition approach for Zn anodes paves the way for the practical application of high-performance zinc-ion batteries.

Untangling the Role of Capping Agents in Manipulating Electrochemical Behaviors Toward Practical Aqueous Zinc-Ion Batteries

Long-standing challenges including notorious side reactions at the Zn anode, low Zn anode utilization, and rapid cathode degradation at low current densities hinder the advancement of aqueous zinc-ion batteries (AZIBs). Inspired by the critical role of capping agents in nanomaterials synthesis and bulk crystal growth, a series of capping agents are employed to demonstrate their applicability in AZIBs. Here, it is shown that the preferential adsorption of capping agents on different Zn crystal planes, coordination between capping agents and Zn2+ ions, and interactions with metal oxide cathodes enable preferred Zn (002) deposition, water-deficient Zn2+ ion solvation structure, and a dynamic cathode-electrolyte interface. Benefiting from the multi-functional role of capping agents, dendrite-free Zn plating and stripping with an improved Coulombic efficiency of 99.2% and enhanced long-term cycling stability are realized. Remarkable capacity retention of 91% is achieved for cathodes after more than 500 cycles under a low current density of 200 mA g-1, marking one of the best cycling stabilities to date. This work provides a proof-of-concept of capping agents in manipulating electrochemical behaviors, which should inspire and pave a new avenue of research to address the challenges in practical energy storage beyond AZIBs.

Ultrafast Tailoring Amorphous Zn0.25V2O5 with Precision-Engineered Artificial Atomic-Layer 1T'-MoS2 Cathode Electrolyte Interphase for Advanced Aqueous Zinc-Ion Batteries

Vanadium (V)-based oxides as cathode materials for aqueous zinc-ion batteries (AZIBs) still encounter challenges such as sluggish Zn2+ diffusion kinetics and V-dissolution, thus leading to severe capacity fading and limited life span. Here, we designed an ultrafast and facile colloidal chemical synthesis strategy based on crystalline Zn0.25V2O5 (c-ZVO) to successfully prepare a-ZVO@MoS2 core@shell heterostructures, where atomic-layer MoS2 uniformly coats on the surface of amorphous a-ZVO. The tailored amorphous structure of a-ZVO provides more isotropic pathways and active sites for Zn2+, thus significantly enhancing the Zn2+ diffusion kinetics during charge-discharge processes. Meanwhile, as an efficient artificial cathode electrolyte interphase, the precision-engineered atomic-layer MoS2 with semi-metallic 1T' phase not only contributes to improved electron transport but also effectively inhibits the V-dissolution of a-ZVO. Therefore, the prepared a-ZVO@MoS2 and conceptually validated a-V2O5@MoS2 derived from commercial c-V2O5 exhibit excellent cycling stability at an ultralow current density (0.05 A g-1) while maintaining good rate capability and capacity retention. This research achievement provides a new effective strategy for various amorphous cathode designs for AZIBs with superior performance.

Simultaneous Inhibition of Vanadium Dissolution and Zinc Dendrites by Mineral-Derived Solid-State Electrolyte for High-Performance Zinc Metal Batteries

Designing solid electrolyte is deemed as an effective approach to suppress the side reaction of zinc anode and active material dissolution of cathodes in liquid electrolytes for zinc metal batteries (ZMBs). Herein, kaolin is comprehensively investigated as raw material to prepare solid electrolyte (KL-Zn) for ZMBs. As demonstrated, KL-Zn electrolyte is an excellent electronic insulator and zinc ionic conductor, which presents wide voltage window of 2.73 V, high ionic conductivity of 5.08 mS cm-1, and high Zn2+ transference number of 0.79. For the Zn//Zn cells, superior cyclic stability lasting for 2200 h can be achieved at 0.2 mA cm-2. For the Zn//NH4V4O10 batteries, stable capacity of 245.8 mAh g-1 can be maintained at 0.2 A g-1 after 200 cycles along with high retention ratio of 81 %, manifesting KL-Zn electrolyte contributes to stabilize the crystal structure of NH4V4O10 cathode. These satisfying performances can be attributed to the enlarged interlayer spacing, zinc (de)solvation-free mechanism and fast diffusion kinetics of KL-Zn electrolyte, availably guaranteeing uniform zinc deposition for zinc anode and reversible zinc (de)intercalation for NH4V4O10 cathode. Additionally, this work also verifies the application possibility of KL-Zn electrolyte for Zn//MnO2 batteries and Zn//I2 batteries, suggesting the universality of mineral-based solid electrolyte.

Proton Storage Chemistry in Aqueous Zinc-Inorganic Batteries with Moderate Electrolytes

The proton (H+) has been proved to be another important energy storage ion besides Zn2+ in aqueous zinc-inorganic batteries with moderate electrolytes. H+ storage usually possesses better thermodynamics and reaction kinetics than Zn2+, and is found to be an important addition for Zn2+ storage. Thus, understanding, characterizing, and modulating H+ storage in inorganic cathode materials is particularly important. In this review, recent advances regarding the proton storage chemistry in aqueous zinc-inorganic batteries with moderate electrolytes are systematically reviewed. First, the four proton storage reaction patterns of H+ insertion, H+/Zn2+ co-insertion, H+-dependent conversion, and H+-dependent dissolution/deposition reaction are explicitly presented. Meanwhile, the proton storage processes of multi-sites and multi-steps, and the Hopping and Grotthuss proton transport mechanisms are carefully introduced. Second, the characterization techniques of proton storage are systematically classified into four types of electrochemical characterization techniques of batteries, structural characterization techniques of inorganic cathodes, pH characterization technique of electrolyte, and quantitative analysis technologies of H+ storage contribution. Third, the structural engineering of proton storage modulation is preliminarily refined to be interlayer engineering, doping engineering, defect engineering, composite engineering, and other engineering. Finally, the emerging challenges and perspectives about future directions of proton storage chemistry are proposed.

Amorphous Structure Benefits in MgV2O4/V2O3 Composites for Zinc-Ion Storage: An Integration of Computational and Experimental Studies

This study investigates the electrochemical properties of MgV2O4/V2O3 composites for Aqueous Zinc-Ion Batteries (AZIBs) using both Density Functional Theory (DFT) calculations and experimental validation. DFT analysis reveals significant electron mobility and reactivity at the MgV2O4/V2O3 interface, enhancing Zn2+ storage capabilities. This theoretical prediction is confirmed experimentally by synthesizing a novel MgV2O4/V2O3 composite that demonstrates superior electrochemical performance compared to pristine phases. Notably, the transition of the MgV2O4/V2O3 composite into an amorphous structure during electrochemical cycling is pivotal, providing enhanced diffusion pathways and increased conductivity. The composite delivers a consistent specific capacity of 330.2 mAh g-1 over 50 cycles at 0.1 A g-1 and maintains 152.7 mAh g-1 at an elevated current density of 20 A g-1 after 2000 cycles, validating the synergy between DFT insights and experimental outcomes, and underscoring the potential of amorphous structures in enhancing battery performance.

Ambient Synthesis of Vanadium-Based Prussian Blue Analogues Nanocubes for High-Performance and Durable Aqueous Zinc-Ion Batteries with Eutectic Electrolytes

Prussian blue analogues (PBAs) have been widely studied in aqueous zinc-ion batteries (AZIBs) due to the characteristics of large specific surface area, open aperture, and straightforward synthesis. In this work, vanadium-based PBA nanocubes were firstly prepared using a mild in situ conversion strategy at room temperature without the protection of noble gas. Benefiting from the multiple-redox active sites of V3+/V4+, V4+/V5+, and Fe2+/Fe3+, the cathode exhibited an excellent discharge specific capacity of 200 mAh g-1 in AZIBs, which is much higher than those of other metal-based PBAs nanocubes. To further improve the long-term cycling stability of the V-PBA cathode, a high concentration water-in-salt electrolyte (4.5 M ZnSO4+3 M Zn(OTf)2), and a water-based eutectic electrolyte (5.55 M glucose+3 M Zn(OTf)2) were designed to successfully inhibit the dissolution of vanadium and improve the deposition of Zn2+ onto the zinc anode. More importantly, the assembled AZIBs maintained 55 % of their highest discharge specific capacity even after 10000 cycles at 10 A g-1 with superior rate capability. This study provides a new strategy for the preparation of pure PBA nanostructures and a new direction for enhancing the long-term cycling stability of PBA-based AZIBs at high current densities for industrialization prospects.

Modulation of Electron Push-Pull by Redox Non-Innocent Additives for Long Cycle Life Zinc Anode

Application of an aqueous Zn-ion battery is plagued by a water-induced hydrogen evolution reaction (HER), resulting in local pH variations and an unstable electrode-electrolyte interface (EEI) with uncontrolled Zn plating and side reactions. Here, 4-methyl pyridine N-oxide (PNO) is introduced as a redox non-innocent additive that comprises a hydrophilic bipolar N+-O- ion pair as a coordinating ligand for Zn and a hydrophobic ─CH3 group at the para position of the pyridine ring that reduces water activity at the EEI, thereby enhancing stability. The N+-O- moiety of PNO possesses the unique functionality of an efficient push electron donor and pull electron acceptor, thus maintaining the desired pH during charging/discharging. Intriguingly, replacing ─CH3 (electron pushing +I effect) by ─CF3 group (electron pulling ─I effect), however, does not improve the reversibility; instead, it degrades the cell performance. The electrolyte with 2 m ZnSO4 + 15 mm PNO enables symmetric cell Zn plating/stripping for a remarkable > 10 000 h at 0.5 mA cm-2 and exhibits coulombic efficiency (CE) ≈99.61% at 0.8 mA cm-2 in Zn/Cu asymmetric cell. This work showcases the immense interplay of the electron push-pull of the additives on the cycling.

Decoupling "Cling-Cover-Capture" Triple Effects on Stable Zn Anode/Electrolyte Interface

The electrochemical performance of the Zn anode in a water-based electrolyte is influenced by the Zn anode/electrolyte interface. In the present work, a distinctive interfacial chemistry is enabled by introducing synergistic "cling-cover-capture" effects of different components in aspartame (APM) molecule, which can be described in detail as clinging to the surface of Zn anode by incompletely coordinated nitrogen and oxygen atoms in the main chain, covering the surface by the benzene rings and capturing Zn2+ by the side chains. Benefiting from its triple effects, this steady anode/electrolyte interface homogenizes Zn2+ flux and excludes interfacial active water, thus effectively suppressing both dendrite growth and side reactions. Consequently, the stability and reversibility of Zn anode experience an enhancement, leading to a long cycle lifespan of 5100 h at 1 mA cm-2 and 1 mA h cm-2, and an average Coulombic efficiency of 99.73% at 1 mA cm-2 and 0.5 mA h cm-2 over 1600 cycles. The improved rate capability and cycling durability of Zn||NH4V4O10 full cells further confirm the important role of APM in stabilizing the Zn anode.

Flash Joule Heating Synthesis of Layer-Stacked Vanadium Oxide/Graphene Hybrids within Seconds for High-Performance Aqueous Zinc-Ion Batteries

Vanadium oxides have been regarded as highly promising cathodes for aqueous zinc-ion batteries (ZIBs). However, obtaining high-performance vanadium oxide-based cathodes suitable for industrial application remains a significant challenge due to the need for cost-effective, straightforward, and efficient preparation methods. Herein, we present a facile and rapid synthesis of a composite cathode, consisting of layer-stacked VO2/V2O5 and graphene-like carbon nanosheets, in just 2.5 s by treating the commercial V2O5 powder via a flash Joule heating strategy. When employed as the cathode for ZIBs, the resulting composite delivers a comparable rate capacity of 459 mA h g-1 at 0.2 A g-1 and remarkable cycle stabilities of 355.5 mA h g-1 after 2500 cycles at 1.0 A g-1 and 169.5 mA h g-1 after 10,000 cycles at 10 A g-1, respectively. Further electrochemical analysis reveals that the impressive performance is attributed to the accelerated charge transfer and the alleviated structure degradation, facilitated by the abundant sites and a built-in electric field of the layer-stacked VO2/V2O5 heterostructure, as well as the excellent conductivity of graphene-like carbon nanosheets. This work introduces a unique approach for ultrafast and low-cost fabrication of high-performance vanadium oxide-based composite cathodes toward efficient ZIBs.

Charged organic ligands inserting/supporting the nanolayer spacing of vanadium oxides for high-stability/efficiency zinc-ion batteries

Given their high safety, environmental friendliness and low cost, aqueous zinc-ion batteries (AZIBs) have the potential for high-performance energy storage. However, issues with the structural stability and electrochemical kinetics during discharge/charge limit the development of AZIBs. In this study, vanadium oxide electrodes with organic molecular intercalation were designed based on intercalating 11 kinds of charged organic carboxylic acid ligands between 2D layers to regulate the interlayer spacing. The negatively charged carboxylic acid group can neutralize Zn2+, reduce electrostatic repulsion and enhance electrochemical kinetics. The intercalated organic molecules increased the interlayer spacing. Among them, the 0.028EDTA · 0.28NH4 + · V2O5 · 0.069H2O was employed as the cathode with a high specific capacity (464.6 mAh g-1 at 0.5 A g-1) and excellent rate performance (324.4 mAh g-1 at 10 A g-1). Even at a current density of 20 A g-1, the specific capacity after 2000 charge/discharge cycles was 215.2 mAh g-1 (capacity retention of 78%). The results of this study demonstrate that modulation of the electrostatic repulsion and interlayer spacing through the intercalation of organic ligands can enhance the properties of vanadium-based materials.

Unveiling Intercalation Chemistry via Interference-Free Characterization Toward Advanced Aqueous Zinc/Vanadium Pentoxide Batteries

Aqueous Zn/V2O5 batteries are featured for high safety, low cost, and environmental compatibility. However, complex electrode components in real batteries impede the fundamental understanding of phase transition processes and intercalation chemistry. Here, model batteries based on V2O5 film electrodes which show similar electrochemical behaviors as the real ones are built. Advanced surface science characterizations of the film electrodes allow to identify intercalation trajectories of Zn2+, H2O, and H+ during V2O5 phase transition processes. Protons serve as the vanguard of intercalated species, facilitating the subsequent intercalation of Zn2+ and H2O. The increase of capacity in the activation process is mainly due to the transition from V2O5 to more active V2O5·nH2O structure caused by the partial irreversible deintercalation of H2O rather than the increase of active sites induced by the grain refinement of electrode materials. Eventually, accumulation of Zn species within the oxide electrode results in the formation of inactive (Zn3(OH)2V2O7·2H2O) structure. The established intercalation chemistry helps to design high-performance electrode materials.

Boosting Zn2+ Storage Kinetics by K-Doping of Sodium Vanadate for Zinc-Ion Batteries

Na5V12O32 is an attractive cathode candidate for aqueous zinc-ion batteries (AZIBs) by virtue of its low-cost and high specific capacity (>300 mAh g-1). However, its intrinsically inferior electronic conductivity and structural instability result in an unfavorable rate performance and cyclability. Herein, K-doped Na5V12O32 (KNVO) was developed to promote its ionic/electronic migration, and thus enhance the Zn2+ storage capability. The as-produced KNVO displays a superior capacity of 353.5 mAh g-1 at 0.1 A g-1 and an excellent retentive capacity of 231.8 mAh g-1 after 1000 cycles at 5 A g-1. Even under a high mass of 5.3 mg cm-2, the KNVO cathode can still maintain a capacity of 220.5 mAh g-1 at 0.1 A g-1 and outstanding cyclability without apparent capacity decay after 2000 cycles. In addition, the Zn2+ storage kinetics of the KNVO cathode is investigated through multiple analyses.

Anion Chemistry towards On-Site Construction of Solid-Electrolyte Interface for Highly Stable Metallic Zn Anode

Reversibility of metallic Zn anode serves as the corner stone for the development of aqueous Zn metal battery, which motivates scrutinizing the electrolyte-Zn interface. As the representative organic zinc salt, zinc trifluorosulfonate (Zn(OTf)2) facilitates a broad class of aqueous electrolytes, however, the stability issue of Zn anode remains crucial. The great challenge lies in the lack of Zn anode protection by the pristinely formed surface structure in aqueous Zn(OTf)2 electrolytes. Accordingly, an electrochemical route was developed to grow a uniform zinc trifluorosulfonate hydroxide (ZTH) layer on Zn anode as an artificial SEI, via regulation on metal dissolution and strong coordination ability of zinc ions. Co-precipitation was proposed to be the formation mechanism for the artificial SEI, where the reduction stability of OTf- anion and the low-symmetry layer structure of ZTH was unmasked. This artificial SEI favors interfacial kinetics, depresses side reactions, and well maintains its integrity during cycling, leading to a prolonged lifespan of Zn stripping/plating with a high DOD of ~85 %, and an improved cycling stability of ~92 % retention rate for V2O5/Zn cell at 1 A g-1. The unveiled role of anion on Zn anode drives the contemplation on the surface chemistry for the blooming aqueous rechargeable battery.

A Stable High-Performance Zn-Ion Batteries Enabled by Highly Compatible Polar Co-Solvent

Uncontrollable growth of Zn dendrites, irreversible dissolution of cathode material and solidification of aqueous electrolyte at low temperatures severely restrict the development of aqueous Zn-ion batteries. In this work, 2,2,2-trifluoroethanol (TFEA) with a volume fraction of 50% as a highly compatible polar-solvent is introduced to 1.3 M Zn(CF3SO3)2 aqueous electrolyte, achieving stable high-performance Zn-ion batteries. Massive theoretical calculations and characterization analysis demonstrate that TFEA weakens the tip effect of Zn anode and restrains the growth of Zn dendrites due to electrostatic adsorption and coordinate with H2O to disrupt the hydrogen bonding network in water. Furthermore, TFEA increases the wettability of the cathode and alleviates the dissolution of V2O5, thus improving the capacity of the full battery. Based on those positive effects of TFEA on Zn anode, V2O5 cathode, and aqueous electrolyte, the Zn//Zn symmetric cell delivers a long cycle-life of 782 h at 5 mA cm-2 and 2 mA h cm-2. The full battery still declares an initial capacity of 116.78 mA h g-1, and persists 87.73% capacity in 2000 cycles at -25 °C. This work presents an effective strategy for fully compatible co-solvent to promote the stability of Zn anode, V2O5 cathode and aqueous electrolyte for high-performance Zn-ion batteries.

Modulating Solvation Shell with Acrylamide Electrolyte Additives for Reversible Zn Anodes

The reconsideration of aqueous zinc-ion batteries (ZIBs) has been motivated by the attractive zinc metal, which stands out for its high theoretical capacity and cost efficiency. Nonetheless, detrimental side reactions triggered by the remarkable reactivity of H2O molecules and rampant dendrite growth significantly compromise the stability of the zinc metal anode. Herein, a novel approach was proposed by leveraging the unique properties of acrylamide (AM) molecules to increase the driving force for nucleation and parasitic reactions. Combined with experimental data and theoretical simulations, it is demonstrated that the incorporation of AM additive can reconstruct the solvation shell around Zn2+ and reduce the number of active H2O molecules, thereby effectively reducing the H2O molecule decomposition. Consequently, the Zn//Zn symmetric batteries with AM-containing ZnSO4 electrolytes can attain excellent long-term performances over 2000 h at 1 mA cm-2 and nearly 500 h at 10 mA cm-2. The Zn//VO2 full batteries still display improved cycling performances and a high initial discharging capacity of 227 mA h g-1 at 3 A g-1 compared to the ZnSO4 electrolyte. This electrolyte optimization strategy offers new insights for achieving long-term ZIBs and advances the progress of ZIBs in energy storage.

Engineering VOx structure by integrating oxygen vacancies for improved zinc-ion storage based on cation-doping regulation with electric density

Aqueous zinc-ion batteries (ZIBs) have attracted enormous attention for future energy-storage devices owing to their high theoretical capacity and environmental friendliness. However, obtaining cathodes with a high specific capacity and fast reaction kinetics remains a huge challenge. Herein, Cu-VOx material with a thin sheet microsphere structure composed of nanoparticles was prepared by a simple hydrothermal reaction, which improved reaction kinetics and specific capacity. Pre-embedding Cu2+ into V2O5 to introduce abundant oxygen vacancies extended the interlayer distance to 1.16 nm, weakened the effect of the V-O bonds, and improved the electrical conductivity and structural stability. At the same time, the influence of different valence metal ions (M = K+, Cu2+, Fe3+, Sn4+, Nb5+, and W6+) pre-embedded in V2O5 was studied. Benefiting from a large interlayer spacing, high electrical conductivity, and excellent structural stability, the Cu-VOx electrode demonstrated a high specific capacity of 455.9 mA h g-1 at 0.1 A g-1. Importantly, when the current density was increased to 6 A g-1, the Cu-VOx electrode still achieved a high specific capacity of 178.8 mA h g-1 and maintained a high capacity retention of 76.5% over 2000 cycles.

Mass Transfer Limitation within Molecular Crowding Electrolyte Reorienting (100) and (101) Texture for Dendrite-Free Zinc Metal Batteries

Aqueous zinc metal batteries are emerging as a promising alternative for energy storage due to their high safety and low cost. However, their development is hindered by the formation of Zn dendrites and side reactions. Herein, a macromolecular crowding electrolyte (MCE40) is prepared by incorporating polyvinylpyrrolidone (PVP) into the aqueous solutions, exhibiting an enlarged electrochemical stability window and anti-freezing properties. Notably, through electrochemical measurements and characterizations, it is discovered that the mass transfer limitation near the electrode surface within the MCE40 electrolyte inhibits the (002) facets. This leads to the crystallographic reorientation of Zn deposition to expose the (100) and (101) textures, which undergo a "nucleation-merge-growth" process to form a uniform and compact Zn deposition. Consequently, the MCE40 enables highly reversible and stable Zn plating/stripping in Zn/Cu half cells over 600 cycles and in Zn/Zn symmetric cells for over 3000 hours at 1.0 mA cm-2. Furthermore, Na0.33V2O5/Zn and α-MnO2/Zn full cells display promising capacity and sustained stability over 500 cycles at room and sub-zero temperatures. This study highlights a novel electrochemical mechanism for achieving preferential Zn deposition, introducing a unique strategy for fabricating dendrite-free zinc metal batteries.

Sodium compensation: a critical technology for transforming batteries from sodium-starved to sodium-rich systems

Sodium-ion batteries (SIBs) have attracted wide attention from academia and industry due to the low cost and abundant sodium resources. Despite the rapid industrialization development of SIBs, it still faces problems such as a low initial coulombic efficiency (ICE) leading to a significant decrease in battery energy density (e.g., 20%). Sodium compensation technology (SCT) has emerged as a promising strategy to effectively increase the ICE to 100% and drastically boost battery cycling performance. In this review, we emphasize the importance of SCT in high-performance SIBs and introduce its working principle. The up-to-date advances in different SCTs are underlined in this review. In addition, we elaborate the current merits and demerits of different SCTs. This review also provides insights into possible future research directions in SCT for high-energy SIBs.

Single-atom catalysts for electrocatalytic nitrate reduction into ammonia

Ammonia (NH3) is a versatile and important compound with a wide range of uses, which is currently produced through the demanding Haber-Bosch process. Electrocatalytic nitrate reduction into ammonia (NRA) has recently emerged as a sustainable approach for NH3synthesis under ambient conditions. However, the NRA catalysis is a complex multistep electrochemical process with competitive hydrogen evolution reaction that usually results in poor selectivity and low yield rate for NH3synthesis. With maximum atom utilization and well-defined catalytic sites, single atom catalysts (SACs) display high activity, selectivity and stability toward various catalytic reactions. Very recently, a number of SACs have been developed as promising NRA electrocatalysts, but systematical discussion about the key factors that affect their NRA performance is not yet to be summarized to date. This review focuses on the latest breakthroughs of SACs toward NRA catalysis, including catalyst preparation, catalyst characterization and theoretical insights. Moreover, the challenges and opportunities for improving the NRA performance of SACs are discussed, with an aim to achieve further advancement in developing high-performance SACs for efficient NH3synthesis.

Tailoring Versatile Cathodes and Induced Anodes for Zn-Se Batteries: Anisotropic Orientation of Tin-Based Materials within Bowl-In-Ball Carbon

The advancement of Zn-Se batteries has been hindered by significant challenges, such as the sluggish kinetics of Se cathodes, limited Se loading, and uncontrollable formation of Zn dendrites. In this study, a bidirectional optimization strategy is devised for both cathode and anode to bolster the performance of Zn-Se batteries. A novel bowl-in-ball structured carbon (BIBCs) material is synthesized to serve as a nanoreactor, in which tin-based materials are grown and derived in situ to construct cathodes and anodes. Within the cathode, the multifunctional host material (SnSe@BIBCs) exhibits large adsorption capacity for selenium, and demonstrates supreme catalytic properties and spatially confined characteristics toward the selenium reduction reaction (SeRR). On the anode, Sn@BIBCs displays triple-induced properties, including the zincophilic of the internal metallic Sn, the homogenized spatial electric field from the 3D spatial structure, and the curvature effect of the bowl-shaped carbon. Collectively, these factors induce preferential nucleation of Zn, ensuring its uniform deposition. As a result, the integrated Zn-Se battery system achieves a remarkable specific capacity of up to 603 mAh g-1 and an impressive energy density of 581 W kg-1, highlighting its tremendous potential for practical applications.

Ultrathin NiO nanosheets anchored to a nitrogen-doped dodecahedral carbon framework for aqueous potassium-ion hybrid capacitors

Hierarchical porous structures and well-modulated interfacial interactions are essential for the performance of electrode materials. The energy storage performance can be promoted by regulating the diffusion behavior of the electrolyte and constructing a coupled interaction at heterogeneous interfaces. Herein, we have synthesized ultrathin NiO nanosheets anchored to nitrogen-doped hierarchical porous carbon (NiO/N-HPC) and applied it to construct aqueous potassium ion hybrid capacitors (APIHCs). The abundant and interconnected porous architecture promotes electrolyte penetration/diffusion and shortens the ion transport path, thereby accelerating storage reaction kinetics. The nitrogen-doped carbon support can achieve optimized metal oxides-carbon interaction and enhance the adsorption ability for the electrolyte ions, leading to earning higher storage capacity. Consequently, the prepared NiO/N-HPC exhibits a superior capacitance of 126.4 F g-1 at a current density of 0.5 A g-1, and the as-fabricated NiO/N-HPC//N-HPC APIHC achieves an ultra-high capacitance retention of 91.6% over 8000 cycles at a current density of 2 A g-1. Meanwhile, the APIHC device shows an excellent energy density of 21.95 W h kg-1 and a power density of 9000 W kg-1.

A quasi-solid-state self-healing flexible zinc-ion battery using a dual-crosslinked hybrid hydrogel as the electrolyte and Prussian blue analogue as the cathode material

Due to their excellent safety and lower cost, aqueous Zn-ion batteries (AZIBs) have garnered extensive interest among various energy-storage systems. Here we report a quasi-solid-state self-healing AZIB by using a hybrid hydrogel which consists of dual-crosslinked polyacrylamide and polyvinyl alcohol as a flexible electrolyte and a cobalt hexacyanoferrate (K3.24Co3[Fe(CN)6]2·12.6H2O) Prussian blue analogue as the cathode material. The obtained hybrid hydrogel showed a superhigh fracture strain of up to 1490%, which was almost 15 times higher than that of the original size. Due to the fast formation of hydrogen bonds, the self-healed hydrogel from two pieces still displayed 1165% strain upon failure. As a result, the self-healed battery delivered stable capacities of 119.1, 108.6 and 103.0 mA h g-1 even after being completely cut into 2, 3 and 4 pieces, respectively. The battery capacity recovery rates for each bending cycle exceeded 99.5%, 99.8%, 98.6% and 98.9% during four continuous bending cycles (30 times bending at 90° for each cycle), which indicates outstanding flexibility and self-healing capability. In parallel, the hydrogel electrolyte displayed a broader electrochemically stable window of 3.37 V due to the suppression of water splitting and low overvoltage during the 500 h cycling in a symmetric cell. Zinc dendrites were also suppressed as evidenced in symmetric cell measurements. The assembled AZIB exhibited an initial capacity of 176 mA h g-1 upon vertical bending. The battery showed a reliable capacity of 140.7 mA h g-1 at 0.2 A g-1 after 100 cycles along with a coulombic efficiency of >99%. A reliable capacity of nearly 100 mA h g-1 was retained after 300 cycles at 1.0 A g-1. The highly flexible and self-healing AZIB demonstrates great potential in various wearable electronic devices.

Heterojunction tunnelled vanadium-based cathode materials for high-performance aqueous zinc ion batteries

Rechargeable aqueous zinc ion batteries (ZIBs) have emerged as a promising alternative to lithium-ion batteries due to their inherent safety, abundant availability, environmental friendliness and cost-effectiveness. However, the cathodes in ZIBs encounter challenges such as structural instability, low capacity, and sluggish kinetics. In this study, we constructed BiVO4@VO2 (BVO@VO) heterojunction cathode material with bismuth vanadate and vanadium dioxide phases for ZIBs, which demonstrate significant advancements in both aqueous and quasi-solid-state ZIBs. Benefitting from the heterojunction structure, the materials present a high capacity of 262 mAh g-1 at 0.1 A g-1, superb cyclic stability with 96% capacity retention after 1000 cycles at 2 A g-1, and outstanding rate property with a specific capacity of 218 mAh g-1 even at a high rate of 5.0 A g-1. Furthermore, the flexible quasi-solid-state ZIBs incorporating the BVO@VO cathode demonstrate prolonged cyclic life performance with a remarkable specific capacity of 234 mAh g-1 over 100 cycles at a current density of 0.1 A g-1. This study potentially paves the way for the utilization of heterointerface-enhanced zinc ion diffusion for vanadium-based materials in ZIBs, thereby providing a new approach for the design and investigation of high-performance zinc-ion systems.

Hydrophobic Two-Dimensional Layered Superstructure of a Polyoxometalate Cluster as the Cathode Material for Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries hold promise for sustainable energy storage, yet challenges in finding high-performance cathode materials persist. Polyoxovanadates (POVs) are emerging as potential candidates due to their structural diversity and robust redox activity. Despite their potential, issues like dissolution in electrolytes, structural degradation, and byproduct accumulation persist. This work introduces a POV-based hydrophobic two-dimensional (2D) layered superstructure that addresses these challenges. The hydrophobic nature minimizes POV dissolution, enhancing structural stability and inhibiting phase transitions during cycling. The 2D arrangement ensures a larger surface area and improved electronic conductivity, resulting in faster kinetics and higher specific capacity. The superstructure demonstrates improved cycle life and an increased operating voltage, marking a significant advancement in POV-based cathode materials for aqueous zinc-ion batteries.

Structure regulation and synchrotron radiation investigation of cathode materials for aqueous Zn-ion batteries

In view of the advantages of low cost, environmental sustainability, and high safety, aqueous Zn-ion batteries (AZIBs) are widely expected to hold significant promise and increasingly infiltrate various applications in the near future. The development of AZIBs closely relates to the properties of cathode materials, which depend on their structures and corresponding dynamic evolution processes. Synchrotron radiation light sources, with their rich advanced experimental methods, serve as a comprehensive characterization platform capable of elucidating the intricate microstructure of cathode materials for AZIBs. In this review, we initially examine available cathode materials and discuss effective strategies for structural regulation to boost the storage capability of Zn2+. We then explore the synchrotron radiation techniques for investigating the microstructure of the designed materials, particularly through in situ synchrotron radiation techniques that can track the dynamic evolution process of the structures. Finally, the summary and future prospects for the further development of cathode materials of AZIBs and advanced synchrotron radiation techniques are discussed.

In Situ Construction of a Hydrophobic Honeycomb-like Structured ZnMoO4 Coating Applied for Enhancing Zinc Anode Performance

Aqueous zinc-ion batteries (AZIBs) suffer from sharp cycling deterioration due to serious interfacial side reactions and corrosion problems on the zinc anode. Herein, an efficacious approach to construct hydrophobic ZnMoO4 coatings on Zn (denoted as Zn@ZMO) is proposed to mitigate direct contact between the zinc anode and electrolyte and enhance its cycle life. The hydrophobic ZnMoO4 layer (contact angle = 128°) with a honeycomb-like structure is prepared by an in situ liquid phase deposition method. The as-prepared ZnMoO4 coating exhibits persistent corrosion protection for Zn through 30 days of immersion in a 2 M ZnSO4 electrolyte, indicating excellent stability of the ZnMoO4 layer and ensuring its available application in AZIBs. Unique microchannels in this kind of honeycomb-like structured coating favor Zn2+ ion diffusion and ease of ion transport, especially at high current cycling. Its robust surface exclusion can effectively counter other side reactions induced by water, simultaneously. As a result, the Zn@ZMO symmetrical cell shows a remarkable cycle lifespan exceeding 2700 h at 1 mA cm-2/1 mA h cm-2, surpassing that of the bare zinc cell by more than 100 folds. At a current density of 5 A g-1, the Zn@ZMO//V2O5 cell can still achieve a specific capacity of 167.0 mA h g-1 after 500 cycles with a capacity retention rate of 88%, which demonstrates its long-term cycling stability.

Ultrasmall, Amorphous V2O3 Intimately Anchored on a Carbon Nanofiber Aerogel Toward High-Rate Zinc-Ion Batteries

When considered as a cathode candidate for aqueous Zn-ion batteries, V2O3 faces several problems, such as inherently unsuitable structure, fast structural degradation, and sluggish charge transport kinetics. In this paper, we report the synthesis of a V2O3 intimately coupled carbon aerogel by a controllable ion impregnation and solid-state reaction strategy using bacterial cellulose and ammonium metavanadate as raw materials. In this newly designed structure, the carbonized carbon fiber network provides fast ion and electron transport channels. More importantly, the cellulose aerogel functions as a dispersing and supporting skeleton to realize the particle size reduction, uniform distribution, and amorphous features of V2O3. These advantages work together to realize adequate electrochemical activation during the initial charging process and shorter transport distance and faster transport kinetics of Zn2+. The batteries based on the V2O3/CNF aerogel exhibit a high-rate performance and an excellent cycling stability. At a current density of 20 A g-1, the V2O3/CNF aerogel delivers a specific capacity of 159.8 mAh g-1, and it demonstrates an exceptionally long life span over 2000 cycles at 12 A g-1. Furthermore, the electrodes with active material loadings as high as 10 mg cm-2 still deliver appreciable specific capacities of 257 mAh g-1 at 0.1 A g-1.

Chitosan-induced NH4V4O10 hierarchical hybrids as high-capacity cathode for aqueous zinc ion batteries

Aqueous zinc ion batteries (AZIBs) have been widely investigated due to their characteristics of convenient operation and intrinsic safety. However, there are several issues to be addressed in AZIBs, such as slow diffusion kinetics of Zn2+, cathode material dissolution and the dendrite formation of zinc anodes. Thus, it is challenging to prepare a high-performance cathode material. In this work, we prepare NH4V4O10 flower-like structures by a facile hydrothermal route. The introduction of chitosan significantly enlarges the layer spacing of the (001) crystal plane. The assembled Zn//NVO-0.15C batteries deliver a specific capacity of 520.54 mA h g-1 at a current density of 0.2 A g-1. Furthermore, they maintain 91% of the retention rate at 5.0 A g-1 after 1000 times cycling. It demonstrates the excellent zinc ion storage behavior of ammonium vanadate electrode materials for AZIBs.