Unlocking the Interfacial Adsorption-Intercalation Pseudocapacitive Storage Limit to Enabling All-Climate, High Energy/Power Density and Durable Zn-Ion Batteries

Sluggish storage kinetics and insufficient performance are the major challenges that restrict the transition metal dichalcogenides (TMDs) applied for zinc ion storage, especially at the extreme temperature conditions. Herein, a multiscale interface structure-integrated modulation concept was presented, to unlock the omnidirectional storage kinetics-enhanced porous VSe2-x·nH2O host. Theory research indicated that the co-modulation of H2O intercalation and selenium vacancy enables enhancing the interfacial zinc ion capture ability and decreasing the zinc ion diffusion barrier. Moreover, an interfacial adsorption-intercalation pseudocapacitive storage mechanism was uncovered. Such cathode displayed remarkable storage performance at the wide temperature range (-40~60oC) in aqueous and solid electrolytes. In particular, it can retain a high specific capacity of 173 mAh g-1 after 5000 cycles at 10 A g-1, as well as a high energy density of 290 Wh kg-1 and a power density of 15.8 kW kg-1 at room temperature. Unexpectedly, a remarkably energy density of 465 Wh kg-1 and power density of 21.26 kW kg-1 at 60oC also can be achieved, as well as 258 Wh kg-1 and 10.8 kW kg-1 at -20oC. This work realizes a conceptual breakthrough for extending the interfacial storage limit of layered TMDs to construct all-climate high-performance Zn-ion batteries.

Polycation-Regulated Electrolyte and Interfacial Electric Fields for Stable Zinc Metal Batteries

Zn metal as one of promising anode materials for aqueous batteries but suffers from disreputable dendrite growth, grievous hydrogen evolution and corrosion. Here, a polycation additive, polydiallyl dimethylammonium chloride (PDD), is introduced to achieve long-term and highly reversible Zn plating/stripping. Specifically, the PDD can simultaneously regulate the electric fields of electrolyte and Zn/electrolyte interface to improve Zn2+ migration behaviors and guide dominant Zn (002) deposition, which is veritably detected by Zeta potential, Kelvin probe force microscopy and scanning electrochemical microscopy. Moreover, PDD also creates a positive charge-rich protective outer layer and a N-rich hybrid inner layer, which accelerates the Zn2+ desolvation during plating process and blocks the direct contact between water molecules and Zn anode. Thereby, the reversibility and long-term stability of Zn anodes are substantially improved, as certified by a higher average coulombic efficiency of 99.7% for Zn//Cu cells and 22 times longer life for Zn//Zn cells compared with that of PDD-free electrolyte.

Carbon Nitride Pillared Vanadate Via Chemical Pre-Intercalation Towards High-PerformanceAqueous Zinc-Ion Batteries

Vanadium compounds are promising cathode materials for aqueous zinc-ion batteries (AZIBs) due to their high specific capacity. However, the narrow interlayer spacing, low intrinsic conductivity and the vanadium dissolution still restrict their further application. Herein, we present an oxygen-deficient vanadate pillared by carbon nitrides (C3N4) as the cathode for AZIBs through a facile self-engaged hydrothermal strategy. Of note, C3N4 nanosheets can act as both the nitrogen source and pre-intercalation species to transform the orthorhombic V2O5 into layered NH4V4O10 with expanded interlayer spacing. Owing to the pillared structure and abundant oxygen vacancies, both the Zn2+ ion (de)intercalation kinetics and the ionic conductivity in the NH4V4O10 cathode are promoted. As a result, the NH4V4O10 cathode delivers exceptional Zn-ion storage ability with a high specific capacity of 398.7 mAh g-1 at 0.5 A g-1, a high-rate capability of 194.7 mAh g-1 at 20 A g-1 and a stable cycling performance of 10000 cycles.

Coupling Zn2+ doping and rich oxygen vacancies in MnO2 nanowire toward advanced aqueous zinc-ion batteries

Easy collapse of structure and sluggish reaction kinetics restrict the practical application of MnO₂ in the field of aqueous Zn-ion batteries (ZIBs). To circumvent these obstacles, Zn²⁺ doping MnO₂ nanowire electrode material with rich oxygen vacancies is prepared by one-step hydrothermal method combined with plasma technology. The experimental results indicate that Zn²⁺ doping MnO₂ nanowire not only stabilizes the interlayer structure of MnO₂, but also provide additional specific capacity as electrolyte ions. Meanwhile, plasma treatment technology induces the oxygen-deficient Zn-MnO₂ electrode optimizing the electronic structure to improve the electrochemical behavior of the cathode materials. Especially, the optimized Zn/Zn-MnO₂ batteries obtain outstanding specific capacity (546 mAh g^-1 at 1 A g^-1) and superior cycling durability (94% over 1000 continuous discharge/charge tests at 3 A g^-1). Greatly, the H⁺ and Zn²⁺ reversible co-insertion/extraction energy storage system of Zn//Zn-MnO₂-4 battery is further revealed by the various characterization analyses during the cycling test process. Further, from the perspective of reaction kinetics, plasma treatment also optimizes the diffusion control behavior of electrode materials. This research proposes a synergistic strategy of element doping and plasma technology, which has enhanced the electrochemical behaviors of MnO₂ cathode and shed light on the design of the high-performance manganese oxide-based cathodes for ZIBs.

A Liquid Metal Microdroplets Initialized Hemicellulose Composite for 3D Printing Anode Host in Zn-Ion Battery

Maintaining a steady affinity between gallium-based liquid metals (LM) and polymer binders, particularly under continuous mechanical deformation, such as extrusion-based 3D printing or plating/stripping of Zinc ion (Zn²⁺ ), is very challenging. Here, an LM-initialized polyacrylamide-hemicellulose/EGaIn microdroplets hydrogel is used as a multifunctional ink to 3D-print self-standing scaffolds and anode hosts for Zn-ion batteries. The LM microdroplets initiate acrylamide polymerization without additional initiators and cross-linkers, forming a double-covalent hydrogen-bonded network. The hydrogel acts as a framework for stress dissipation, enabling recovery from structural damage due to the cyclic plating/stripping of Zn²⁺ . The LM-microdroplet-initialized polymerization with hemicelluloses can facilitate the production of 3D printable inks for energy storage devices.

Bi-MOF Modulating MnO2 Deposition Enables Ultra-Stable Cathode-Free Aqueous Zinc-Ion Batteries

The Mn-based materials are considered as the most promising cathodes for zinc-ion batteries (ZIBs) due to their inherent advantages of safety, sustainability and high energy density, however suffer from poor cyclability caused by gradual Mn²⁺ dissolution and irreversible structural transformation. The mainstream solution is pre-adding Mn²⁺ into the electrolyte, nevertheless faces the challenge of irreversible Mn²⁺ consumption results from the MnO₂ electrodeposition reaction (Mn²⁺  → MnO₂ ). This work proposes a "MOFs as the electrodeposition surface" strategy, rather than blocking it. The bismuth (III) pyridine-3,5-dicarboxylate (Bi-PYDC) is selected as the typical electrodeposition surface to regulate the deposition reaction from Mn²⁺ to MnO₂ . Because of the unique less hydrophilic and manganophilic nature of Bi-PYDC for Mn²⁺ , a moderate MnO₂ deposition rate is achieved, preventing the electrolyte from rapidly exhausting Mn²⁺ . Simultaneously, the intrinsic stability of deposited R-MnO₂ is enhanced by the slowly released Bi³⁺ from Bi-PYDC reservoir. Furthermore, Bi-PYDC shows the ability to accommodate H⁺ insertion/extraction. Benefiting from these merits, the cathode-free ZIB using Bi-PYDC as the electrodeposition surface for MnO₂ shows an outstanding cycle lifespan of more than 10 000 cycles at 1 mA cm^-2 . This electrode design may stimulate a new pathway for developing cathode free long-life rechargeable ZIBs.

Reducing the Surface Tension of Zn Anodes by an Abietic Acid Layer for High Redox Kinetics and Reversibility

Aqueous zinc batteries are appealing devices for cost-effective and environmentally sustainable energy storage. However, the critical issues of uncontrolled dendrite propagation and side reactions with Zn anodes have hindered their practical applications. Inspired by the functions of the rosin flux in soldering, an abietic acid (ABA) layer is fabricated on the surface of Zn anodes (ABA@Zn). The ABA layer protects the Zn anode from corrosion and the concomitant hydrogen evolution reaction. It also facilitates fast interfacial charge transfer and horizontal growth of the deposited Zn by reducing the surface tension of the Zn anode. Consequently, promoted redox kinetics and reversibility are simultaneously achieved by the ABA@Zn. It demonstrates stable Zn plating/stripping cycling over 5100 h and a high critical current of 8.0 mA cm^-2. Moreover, the assembled ABA@Zn|(NH₄)₂V₆O₁₆ full cell delivers outstanding long-term cycling stability with an 89% capacity retention after 3000 cycles. This work provides a straightforward yet effective solution to the key issues of aqueous zinc batteries.

3D Cold-Trap Environment Printing for Long-Cycle Aqueous Zn-Ion Batteries

Zn powder (Zn-P)-based anodes are always regarded as ideal anode candidates for zinc ion batteries owing to their low cost and ease of processing. However, the intrinsic negative properties of Zn-P-based anodes such as easy corrosion and uncontrolled dendrite growth have limited their further applications. Herein, a novel 3D cold-trap environment printing (3DCEP) technology is proposed to achieve the MXene and Zn-P (3DCEP-MXene/Zn-P) anode with highly ordered arrangement. Benefitting from the unique inhibition mechanism of high lattice matching and physical confinement effects within the 3DCEP-MXene/Zn-P anode, it can effectively homogenize the Zn²⁺ flux and alleviate the Zn deposition rate of the 3DCEP-MXene/Zn-P anode during Zn plating-stripping. Consequently, the 3DCEP-MXene/Zn-P anode exhibits a superior cycling lifespan of 1400 h with high coulombic efficiency of ≈9.2% in symmetric batteries. More encouragingly, paired with MXene and Co doped MnHCF cathode via 3D cold-trap environment printing (3 DCEP-MXene/Co-MnHCF), the 3DCEP-MXene/Zn-P//3DCEP-MXene/Co-MnHCF full battery delivers high cyclic durability with the capacity retention of 95.7% after 1600 cycles. This study brings an inspired universal pathway to rapidly fabricate a reversible Zn anode with highly ordered arrangement in a cold environment for micro-zinc storage systems.

Rational Design of Flexible Zn-Based Batteries for Wearable Electronic Devices

The advent of 5G and the Internet of Things has spawned a demand for wearable electronic devices. However, the lack of a suitable flexible energy storage system has become the "Achilles' Heel" of wearable electronic devices. Additional problems during the transformation of the battery structure from conventional to flexible also present a severe challenge to the battery design. Flexible Zn-based batteries, including Zn-ion batteries and Zn-air batteries, have long been considered promising candidates due to their high safety, eco-efficiency, substantial reserve, and low cost. In the past decade, researchers have come up with elaborate designs for each portion of flexible Zn-based batteries to improve the ionic conductivities, mechanical properties, environment adaptabilities, and scalable productions. It would be helpful to summarize the reported strategies and compare their pros and cons to facilitate further research toward the commercialization of flexible Zn-based batteries. In this review, the current progress in developing flexible Zn-based batteries is comprehensively reviewed, including their electrolytes, cathodes, and anodes, and discussed in terms of their synthesis, characterization, and performance validation. By clarifying the challenges in flexible Zn-based battery design, we summarize the methodology from previous investigations and propose challenges for future development. In the end, a research paradigm of Zn-based batteries is summarized to fit the burgeoning requirement of wearable electronic devices in an iterative process, which will benefit the future development of Zn-based batteries.

Stable Zn Anodes with Triple Gradients

Aqueous zinc-ion batteries are highly desirable for sustainable energy storage, but the undesired Zn dendrites growth severely shortens the cycle life. Herein, a triple-gradient electrode that simultaneously integrates gradient conductivity, zincophilicity, and porosity is facilely constructed for a dendrite-free Zn anode. The simple mechanical rolling-induced triple-gradient design effectively optimizes the electric field distribution, Zn²⁺ ion flux, and Zn deposition paths in the Zn anode, thus synergistically achieving a bottom-up deposition behavior for Zn metals and preventing the short circuit from top dendrite growth. As a result, the electrode with triple gradients delivers a low overpotential of 35 mV and operates steadily over 400 h at 5 mA cm^-2 /2.5 mAh cm^-2 and 250 h at 10 mA cm^-2 /1 mAh cm^-2 , far surpassing the non-gradient, single-gradient and dual-gradient counterparts. The well-tunable materials and structures with the facile fabrication method of the triple-gradient strategy will bring inspiration for high-performance energy storage devices.

Molecular-Level Zn-Ion Transfer Pump Specifically Functioning on (002) Facets Enables Durable Zn Anodes

The modification of metallic Zn anode contributes to solving the cycling issue of Zn-ion batteries (ZIBs) by restraining the dendrite growth and side reactions. In this regard, modulating (002) Zn is an effective way to prolong the lifespan of ZIBs with a parallel arrangement of Zn deposition. Herein, the authors propose to add trace amounts of Zn(BF₄ )₂ additive in 3 M ZnSO₄ to promote in-plane Zn deposition by forming a BF₄ ^- -[Zn(H₂ O)₆ ]²⁺ -[Zn(BF₄ )₃ ]^- transfer process and specifically functioning on (002) facets. In this way, the optimized electrolyte highly boosts the cycling stability of Zn anodes with a long lifespan at 34.2% Zn utilization (500 h/10 mA cm^-2 ) and 51.3% Zn utilization (360 h/10 mA cm^-2 ; 834 h/1 mA cm^-2 ). Moreover, the electroplated Zn on Cu substrate exhibits a competitive cumulative plating capacity (CPC) of 2.87 Ah cm^-2 under harsh conditions. The assembled Zn|(NH₄ )₂ V₆ O₁₆ ·3H₂ O full cells with a high cathode loading of 29.12 mg cm^-2 also realizes almost no capacity degradation even after 2000 cycles at 2 A g^-1 . With this cost-effective strategy, it is promising to push the development of aqueous ZIBs as well as provide inspiration for metal anode optimization in other energy storage systems.

Heterostructures Stimulate Electric-Field to Facilitate Optimal Zn2+ Intercalation in MoS2 Cathode

The electric-field effect is an important factor to enhance the charge diffusion and transfer kinetics of interfacial electrode materials. Herein, by designing a heterojunction, the influence of the electric-field effect on the kinetics of the MoS₂ as cathode materials for aqueous Zn-ion batteries (AZIBs) is deeply investigated. The hybrid heterojunction is developed by hydrothermal growth of MoS₂ nanosheets on robust titanium-based transition metal compound ([titanium nitride, TiN] and [titanium oxide, TiO₂ ]) nanowires, denoted TNC@MoS₂ and TOC@MoS₂ NWS, respectively. Benefiting from the heterostructure architecture and electric-field effect, the TNC@MoS₂ electrodes exhibit an impressive rate performance of 200 mAh g^-1 at 50 mA g^-1 and cycling stability over 3000 cycles. Theoretical studies reveal that the hybrid architecture exhibits a large-scale electric-field effect at the interface between TiN and MoS₂ , enhances the adsorption energy of Zn-ions, and increases their charge transfer, which leads to accelerated diffusion kinetics. In addition, the electric-field effect can also be effectively applied to TiO₂ and MoS₂ , confirming that the concept of heterostructures stimulating electric-field can provide a relevant understanding for the architecture of other cathode materials for AZIBs and beyond.

Interspace and Vacancy Modulation: Promoting the Zinc Storage of an Alcohol-Based Organic-Inorganic Cathode in a Water-Organic Electrolyte

Expanding interspace and introducing vacancies are desired to promote the mobility of Zn ions and unlock the inactive sites of layered cathodes. However, this two-point modulation has not yet been achieved simultaneously in vanadium phosphate. Here, a strategy is proposed for fabricating an alcohol-based organic-inorganic hybrid material, VO_{1- x} PO₄ ·0.56C₆ H₁₄ O₄ , to realize the conjoint modulation of the d-interspace and oxygen vacancies. Peculiar triglycol molecules with an inclined orientation in the interlayer also boost the improvement in the conversion rate of V⁵⁺ to V⁴⁺ and the intensity of the PO bond. Their synergism can ensure steerable adjustment for intercalation kinetics and electron transport, as well as realize high chemical reactivity and redox-center optimization, leading to at least 200% increase in capacity. Using a water-organic electrolyte, the designed Zn-ion batteries with an ultrahigh-rate profile deliver a long-term durability (fivefold greater than pristine material) and an excellent energy density of ≈142 Wh kg^-1 (including masses of cathode and anode), thereby substantially outstripping most of the recently reported state-of-the-art zinc-ion batteries. This work proves the feasibility to realize the two-point modulation by using organic intercalants for exploiting high-performance new 2D materials.

Electrolyte Salts and Additives Regulation Enables High Performance Aqueous Zinc Ion Batteries: A Mini Review

Aqueous zinc ion batteries (ZIBs) are regarded as one of the most ideally suited candidates for large-scale energy storage applications owning to their obvious advantages, that is, low cost, high safety, high ionic conductivity, abundant raw material resources, and eco-friendliness. Much effort has been devoted to the exploration of cathode materials design, cathode storage mechanisms, anode protection as well as failure mechanisms, while inadequate attentions are paid on the performance enhancement through modifying the electrolyte salts and additives. Herein, to fulfill a comprehensive aqueous ZIBs research database, a range of recently published electrolyte salts and additives research is reviewed and discussed. Furthermore, the remaining challenges and future directions of electrolytes in aqueous ZIBs are also suggested, which can provide insights to push ZIBs' commercialization.

Design and Synthesis of a π-Conjugated N-Heteroaromatic Material for Aqueous Zinc-Organic Batteries with Ultrahigh Rate and Extremely Long Life

Electroactive organic materials with tailored functional groups are of great importance for aqueous Zn-organic batteries due to their green and renewable nature. Herein, a completely new N-heteroaromatic material, hexaazatrinaphthalene-phenazine (HATN-PNZ) is designed and synthesized, by an acid-catalyzed condensation reaction, and its use as an ultrahigh performance cathode for Zn-ion batteries demonstrated. Compared with phenazine monomer, it is revealed that the π-conjugated structure of N-heteroaromatics can effectively increase electron delocalization, thereby improving its electrical conductivity. Furthermore, the enlarged aromatic structure noticeably suppresses its dissolution in aqueous electrolytes, thus enabling high structural stability. As expected, the HATN-PNZ cathode delivers a large reversible capacity of 257 mAh g^-1 at 5 A g^-1 , ultrahigh rate capability of 144 mAh g^-1 at 100 A g^-1 , and an extremely long cycle life of 45 000 cycles at 50 A g^-1 . Investigation of the charge-storage mechanism demonstrates the synergistic coordination of both Zn²⁺ and H⁺ cations with the phenanthroline groups, with Zn²⁺ first followed by H⁺ , accompanying the reversible formation of zinc hydroxide sulfate hydrate. This work provides a molecular-engineering strategy for superior organic materials and adds new insights to understand the charge-storage behavior of aqueous Zn-organic batteries.

Manipulating Hierarchical Orientation of Wet-Spun Hybrid Fibers via Rheological Engineering for Zn-Ion Fiber Batteries

Wet-spinning is a promising strategy to fabricate fiber electrodes for real commercial fiber battery applications, according to its great compatibility with large-scale fiber production. However, engineering the rheological properties of the electrochemical active materials to accommodate the viscoelasticity or liquid crystalline requirements for continuous wet-spinning remains a daunting challenge. Here, with entropy-driven volume-exclusion effects, the rheological behavior of vanadium pentoxide (V₂ O₅ ) nanowire dispersions is regulated through introducing 2D graphene oxide (GO) flakes in an optimal ratio. By optimizing the viscoelasticity and liquid-crystalline behavior of the spinning dope, the wet-spun hybrid fibers display controlled hierarchical orientation. The wet-spun V₂ O₅ /rGO hybrid fiber with the optimal 10:1 mass fraction (V₂ O₅ /rGO_10:1 ) exhibits a highly oriented nanoblock arrangement, enabling efficient Zn-ion migration and an excellent Zn-ion storage capacity of 486.03 mAh g^-1 at 0.1 A g^-1 . A half-meter long quasi-solid-state fiber Zn-ion battery is assembled with a polyacrylamide gel electrolyte and biocompatible Ecoflex encapsulation. The thus-derived fiber Zn-ion battery is integrated into a wearable self-powered system, incorporating a highly efficient GaAs solar cell, which delivers a record-high overall efficiency (9.80%) for flexible solar charging systems.

Biomolecular Regulation of Zinc Deposition to Achieve Ultra-Long Life and High-Rate Zn Metal Anodes

Aqueous zinc-ion batteries (ZIBs) have been extensively studied due to their inherent safety and high energy density for large-scale energy storage. However, the practical application is significantly limited by the growing Zn dendrites on metallic Zn anode during cycling. Herein, an environmental biomolecular electrolyte additive, fibroin (FI), is proposed to guide the homogeneous Zn deposition and stabilize Zn anode. This work demonstrates that the FI molecules with abundant electron-rich groups (NH, OH, and CO) can anchor on Zn anode surface to provide more nucleation sites and suppress the side reactions, and the strong interaction with water molecules can simultaneously regulate the Zn²⁺ coordination environment facilitating the uniform deposition of Zn. As a consequence, only 0.5 wt% FI additive enables a highly reversible Zn plating/stripping over 4000 h at 1 mA cm^-2 , indicating a sufficient advance in performance over state-of-the-art Zn anodes. Furthermore, when applied to a full battery (NaVO/Zn), the cell exhibits excellent capacity retention of 98.4% after 1000 cycles as well as high Coulombic efficiency of 99%, whereas the cell only operates for 68 cycles without FI additive. This work offers a non-toxic, low-cost, effective additive strategy to solve dendrites problems and achieve long-life and high-performance rechargeable aqueous ZIBs.

The Dopamine Assisted Synthesis of MoO3/Carbon Electrodes With Enhanced Capacitance in Aqueous Electrolyte

A capacitance increase phenomenon is observed for MoO₃ electrodes synthesized via a sol-gel process in the presence of dopamine hydrochloride (Dopa HCl) as compared to α-MoO₃ electrodes in 5M ZnCl₂ aqueous electrolyte. The synthesis approach is based on a hydrogen peroxide-initiated sol-gel reaction to which the Dopa HCl is added. The powder precursor (Dopa)_xMoO_y, is isolated from the metastable gel using freeze-drying. Hydrothermal treatment (HT) of the precursor results in the formation of MoO₃ accompanied by carbonization of the organic molecules; designated as HT-MoO₃/C. HT of the precipitate formed in the absence of dopamine in the reaction produced α-MoO₃, which was used as a reference material in this study (α-MoO₃-ref). Scanning electron microscopy (SEM) images show a nanobelt morphology for both HT-MoO₃/C and α-MoO₃-ref powders, but with distinct differences in the shape of the nanobelts. The presence of carbonaceous content in the structure of HT-MoO₃/C is confirmed by FTIR and Raman spectroscopy measurements. X-ray diffraction (XRD) and Rietveld refinement analysis demonstrate the presence of α-MoO₃ and h-MoO₃ phases in the structure of HT-MoO₃/C. The increased specific capacitance delivered by the HT-MoO₃/C electrode as compared to the α-MoO₃-ref electrode in 5M ZnCl₂ electrolyte in a −0.25–0.70 V vs. Ag/AgCl potential window triggered a more detailed study in an expanded potential window. In the 5M ZnCl₂ electrolyte at a scan rate of 2 mV s⁻¹, the HT-MoO₃/C electrode shows a second cycle capacitance of 347.6 F g⁻¹. The higher electrochemical performance of the HT-MoO₃/C electrode can be attributed to the presence of carbon in its structure, which can facilitate electron transport. Our study provides a new route for further development of metal oxides for energy storage applications.

Highly Reversible Zinc Anode Enabled by a Cation-Exchange Coating with Zn-Ion Selective Channels

Rechargeable aqueous zinc-ion batteries (ZIBs) have attracted extensive attention due to their low cost and high safety. However, the critical issues of dendrite growth and side reactions on the Zn metal anode hinder the commercialization of ZIBs. Herein, we demonstrated that the formation of Zn₄SO₄(OH)₆·5H₂O byproducts is closely relevant to the direct contact between the Zn electrode and SO₄^2-/H₂O. On the basis of this finding, we developed a cation-exchange membrane of perfluorosulfonic acid (PFSA) coated on the Zn surface to regulate the Zn plating/stripping behavior. Importantly, the PFSA film with abundant sulfonic acid groups could simultaneously block the access of SO₄^2- and H₂O, accelerate the Zn²⁺ ion transport kinetics, and uniformize the electrical and Zn²⁺ ion concentration field on the Zn surface, thus achieving a highly reversible Zn plating/stripping process with corrosion-free and dendrite-free behavior. Consequently, the PFSA-modified Zn anode exhibits high reversibility with 99.5% Coulombic efficiency and excellent plating/stripping stability (over 1500 h), subsequently enabling a highly rechargeable Zn-MnO₂ full cell. The strategy of the cation-exchange membrane proposed in this work provides a simple but efficient method for suppression of side reactions.

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

Zn-ion batteries (ZIBs) using aqueous electrolyte, recently, have been a hot topic owing to the high safety, low cost, and high specific energy capacity. However, the formation of dendrite and side reactions on the Zn anode during cycling inhibit the application of ZIBs. An advanced Zn anode by alloying a small amount of Li and Mn with Zn is hereby reported. It is found that Li and Mn can form cationic ions which restrain lateral diffusion of Zn ions and regulate zinc electrodeposition through the electrostatic shield mechanism. As a result, the formation of Zn dendrite is greatly inhibited. This process also mitigates the formation of Zn-based byproduct and Zn passivation. Consequently, the symmetric ZnLiMn/ZnLiMn cell presents a small overpotential of 30 mV at 1 mA cm^-2 , greatly enhanced cycling durability (1000 h at a current density of 1 mA cm^-2 ), and a dendrite-free morphology after cycles. Moreover, the authors find that the ZnLiMn alloy has greatly enhanced mechanical properties. The assembled ZnLiMn/MnO₂ full cell can retain 96% capacity after 400 cycles at 1 C. Thus, the alloying low-cost Li/Mn strategy is very promising for large-scale production of dendrite-free Zn electrode in rechargeable ZIBs.

Reunderstanding the Reaction Mechanism of Aqueous Zn-Mn Batteries with Sulfate Electrolytes: Role of the Zinc Sulfate Hydroxide

Rechargeable aqueous Zn-Mn batteries have garnered extensive attention for next-generation high-safety energy storage. However, the charge-storage chemistry of Zn-Mn batteries remains controversial. Prevailing mechanisms include conversion reaction and cation (de)intercalation in mild acid or neutral electrolytes, and a MnO₂ /Mn²⁺ dissolution-deposition reaction in strong acidic electrolytes. Herein, a Zn₄ SO₄ ·(OH)₆ ·xH₂ O (ZSH)-assisted deposition-dissolution model is proposed to elucidate the reaction mechanism and capacity origin in Zn-Mn batteries based on mild acidic sulfate electrolytes. In this new model, the reversible capacity originates from a reversible conversion reaction between ZSH and Zn_x MnO(OH)₂ nanosheets in which the MnO₂ initiates the formation of ZSH but contributes negligibly to the apparent capacity. The role of ZSH in this new model is confirmed by a series of operando characterizations and by constructing Zn batteries using other cathode materials (including ZSH, ZnO, MgO, and CaO). This research may refresh the understanding of the most promising Zn-Mn batteries and guide the design of high-capacity aqueous Zn batteries.

A Biomimetic Polymer-Based Composite Coating Inhibits Zinc Dendrite Growth for High-Performance Zinc-Ion Batteries

Because of their low cost, safety, and green nature, aqueous Zn-ion batteries are promising candidates for energy storage. However, the appearance of Zn dendrites, hydrogen evolution reaction (HER), and corrosion limit the development of the aqueous Zn-ion batteries. Here, inspired by fibrous cartilage, a biomimetic poly(vinylidene fluoride) (PVDF)-based composite polymer coating layer, including aramid nanofiber (ANF) and zinc trifluoromethanesulfonate [Zn(CF₃SO₃)₂], called ANFZ, was designed and fabricated. The high ionic conductivity (3.84 mS cm^-1) of the flexible PVDF matrix, optimized by Zn(CF₃SO₃)₂, combined with the highly mechanical ANF network can effectively guide the rate of Zn stripping/plating, homogenize the Zn²⁺ distribution, and suppress the dendrites. In addition, the high Coulombic efficiency is obtained due to the suppression of HER and corrosion by the biomimetic coating layer. Symmetric ANFZ@Zn//ANFZ@Zn can steadily work over 1000 h at 1 mA cm^-2 with a high degree of reversibility, which is greater than that of bare Zn//bare Zn. Furthermore, the ANFZ@Zn//MVO batteries show a high specific capacity (400.2 mAh g^-1, 0.1 A g^-1) and a long cycle life. This work presents a novel method combined with bionics for designing and assembling Zn anodes without dendrites for zinc-ion batteries.

Regulating Interfacial Ion Migration via Wool Keratin Mediated Biogel Electrolyte toward Robust Flexible Zn-Ion Batteries

Aqueous Zn-ion batteries (ZIBs) have emerged as a promising energy supply for next-generation wearable electronics, yet they are still impeded by the notorious growth of zinc dendrite and uncontrollable side reaction. While the rational design of electrolyte composition or separator decoration can effectively restrain zinc dendrite growth, synchronously regulating the interfacial electrochemical performance by tackling the physical delamination venture between electrode and electrolyte remains a major obstacle for high-performance wearable aqueous ZIB. Herein, a category of hybrid biogel electrolyte containing carrageenan and wool keratin (CWK) is put forward to regulate the interfacial electrochemistry in aqueous ZIB. Systematic electrochemical kinetics analyses and ex situ scanning electrochemical microscopy (SECM) characterizations achieve comprehensive understanding of the keratin enhanced interfacial Zn²⁺ redox reaction. Thanks to the keratin triggered selective ion permeability, the as-designed CWK hybrid biogel electrolyte manifests a promoted Zn²⁺ transference number and excellent reversibility of Zn plating/stripping and outstanding Zn utilization (average Coulombic efficiency ≈98%). More impressively, the CWK hybrid biogel electrolyte also demonstrates cathode side-reaction depression and strengthened interfacial adhesion while assembled into a quasi-solid-state flexible ZIB. This work offers a strategy to synchronously solve concurrent challenges for both of Zn anode and cathode toward realistic wearable aqueous ZIB.

Electrostatic Shielding Regulation of Magnetron Sputtered Al-Based Alloy Protective Coatings Enables Highly Reversible Zinc Anodes

The uncontrolled zinc dendrite growth during plating leads to quick battery failure, which hinders the widespread applications of aqueous zinc-ion batteries. The growth of Zn dendrites is often promoted by the "tip effect". In this work, we propose a generate strategy to eliminate the "tip effect" by utilizing the electrostatic shielding effect, which is achieved by coating Zn anodes with magnetron sputtered Al-based alloy protective layers. The Al can form a surface insulating Al₂O₃ layer and by manipulating the Al content of Zn-Al alloy films, we are able to control the strength of the electrostatic shield, therefore realizing a long lifespan of Zn anodes up to 3000 h at a practical operating condition of 1.0 mA cm^-2 and 1.0 mAh cm^-2. In addition, the concept can be extended to other Al-based systems such as Ti-Al alloy and achieve enhanced stability of Zn anodes, demonstrating the generality and efficacy of our strategy.

Hexagonal WO3/3D Porous Graphene as a Novel Zinc Intercalation Anode for Aqueous Zinc-Ion Batteries

Aqueous Zn-ion batteries (ZIBs) have acquired great attention because of their high safety and environmentally friendly properties. However, the uncontrollable Zn dendrites and the irreversibility of electrodes seriously affect their practical application. Herein, hexagonal WO₃/three-dimensional porous graphene (h-WO₃/3DG) is investigated as an intercalation anode for ZIBs. As a result, the h-WO₃/3DG//Zn half-battery shows excellent electrochemical performance with a high capacity of 115.6 mAh g^-1 at 0.1 A g^-1 and 89% capacity retention at 2.0 A g^-1 after 10 000 cycles. The reason could be that the crystalline structure of WO₃, which has hexagonal channels, with a diameter of 5.36 Å, much higher than the diameter of Zn²⁺ (0.73 Å), accelerating the insertion/extraction of Zn ions. A zinc metal-free full battery using h-WO₃/3DG as the anode and ZnMn₂O₄/carbon black (ZnMn₂O₄/CB) as the cathode is constructed, exhibiting an initial capacity of 66.8 mAh g^-1 at 0.1 A g^-1 corresponding to an energy density of 73.5 W h kg^-1 (based on the total mass of anode and cathode-active materials) and a capacity retention of 76.6% after 1000 cycles at 0.5 A g^-1. This work demonstrates the high potential of hexagonal WO₃ as an advanced intercalation anode material for Zn metal-free batteries and may inspire new ideas for the development of other intercalation anode hosts for ZIBs.