Cations-Pillared and Polyaniline-Encapsulated Vanadate Cathode for High-Performance Aqueous Zinc-Ion Batteries.

Layered vanadium-based oxides have emerged as highly promising candidates for aqueous zinc-ion batteries (AZIBs) due to their open-framework layer structure and high theoretical capacity among the diverse cathode materials investigated. However, the susceptibility to structural collapse during charge-discharge cycling severely hampers their advancement. Herein, we propose an effective strategy to enhance the cycling stability of vanadium oxides. Initially, the structural integrity of the host material is significantly reinforced by incorporating bi-cations Na+ and NH4+ as "pillars" between the V2O5 layers (NaNVO). Subsequently, surface coating with polyaniline (PA) is employed to further improve the conductivity of the active material. As anticipated, the assembled Zn//NaNVO@PA cell exhibits a remarkable discharge capacity of 492 mAh g-1 at 0.1 A g-1 and exceptional capacity retention up to 89.2% after 1000 cycles at a current density of 5 A g-1. Moreover, a series of in-situ and ex-situ characterization techniques were utilized to investigate both Zn ions insertion/extraction storage mechanism and the contribution of polyaniline protonation process towards enhancing capacity.

Single [0001]-oriented zinc metal anode enables sustainable zinc batteries.

The optimization of crystalline orientation of a Zn metal substrate to expose more Zn(0002) planes has been recognized as an effective strategy in pursuit of highly reversible Zn metal anodes. However, the lattice mismatch between substrate and overgrowth crystals has hampered the epitaxial sustainability of Zn metal. Herein, we discover that the presence of crystal grains deviating from [0001] orientation within a Zn(0002) metal anode leads to the failure of epitaxial mechanism. The electrodeposited [0001]-uniaxial oriented Zn metal anodes with a single (0002) texture fundamentally eliminate the lattice mismatch and achieve ultra-sustainable homoepitaxial growth. Using high-angle angular dark-filed scanning transmission electron microscopy, we elucidate the homoepitaxial growth of the deposited Zn following the "~ABABAB~" arrangement on the Zn(0002) metal from an atomic-level perspective. Such consistently epitaxial behavior of Zn metal retards dendrite formation and enables improved cycling, even in Zn||NH4V4O10 pouch cells, with a high capacity of 220 mAh g-1 for over 450 cycles. The insights gained from this work on the [0001]-oriented Zn metal anode and its persistently homoepitaxial mechanism pave the way for other metal electrodes with high reversibility.

Low-current-density stability of vanadium-based cathodes for aqueous zinc-ion batteries.

Vanadium-based cathodes have received widespread attention in the field of aqueous zinc-ion batteries, presenting a promising prospect for stationary energy storage applications. However, the rapid capacity decay at low current densities has hampered their development. In particular, capacity stability at low current densities is a requisite in numerous practical applications, typically encompassing peak load regulation of the electricity grid, household energy storage systems, and uninterrupted power supplies. Despite possessing notably high specific capacities, vanadium-based materials exhibit severe instability at low current densities. Moreover, the issue of stabilizing electrode reactions at these densities for vanadium-based materials has been explored insufficiently in existing research. This review aims to investigate the matter of stability in vanadium-based materials at low current densities by concentrating on the mechanisms of capacity fading and optimization strategies. It proposes a comprehensive approach that includes electrolyte optimization, electrode modulation, and electrochemical operational conditions. Finally, we presented several crucial prospects for advancing the practical development of vanadium-based aqueous zinc-ion batteries.

Validating Operating Stability and Biocompatibility Toward Safer Zinc-Based Batteries.

Wearable and implantable electronics are standing at the frontiers of science and technology, driven by the increasing demands from modernized lifestyles. Zinc-based batteries (ZBs) are regarded as ideal energy suppliers for these biocompatible electronics, but the corresponding biocompatibility validation is still in the initial stage. Meanwhile, complicated working conditions and some extreme electrolyte environments raise strict challenges, leaving less choices for safe ZBs. Toward higher operating stability and biocompatibility, this work proposes a hydrogel electrolyte featuring the moisture maintaining ability and a robust interface, which could further provide a milder environment for Zn-MnO2 batteries and Zn-air batteries. The cytotoxicity and tissue injury of batteries are evaluated with human cell lines and battery implantations on the animal models, which demonstrate the high biocompatibility of ZBs, while preliminary wearable devices implementation further verifies their operating stability. This work may provide a pathway for developing and validating biocompatible ZBs, contributing to their future practical employment in relevant fields.

Tailoring grain boundary stability of zinc-titanium alloy for long-lasting aqueous zinc batteries.

The detrimental parasitic reactions and uncontrolled deposition behavior derived from inherently unstable interface have largely impeded the practical application of aqueous zinc batteries. So far, tremendous efforts have been devoted to tailoring interfaces, while stabilization of grain boundaries has received less attention. Here, we demonstrate that preferential distribution of intermetallic compounds at grain boundaries via an alloying strategy can substantially suppress intergranular corrosion. In-depth morphology analysis reveals their thermodynamic stability, ensuring sustainable potency. Furthermore, the hybrid nucleation and growth mode resulting from reduced Gibbs free energy contributes to the spatially uniform distribution of Zn nuclei, promoting the dense Zn deposition. These integrated merits enable a high Zn reversibility of 99.85% for over 4000 cycles, steady charge-discharge at 10 mA cm-2, and impressive cyclability for roughly 3500 cycles in Zn-Ti//NH4V4O10 full cell. Notably, the multi-layer pouch cell of 34 mAh maintains stable cycling for 500 cycles. This work highlights a fundamental understanding of microstructure and motivates the precise tuning of grain boundary characteristics to achieve highly reversible Zn anodes.

Reconstructing interfacial manganese deposition for durable aqueous zinc-manganese batteries.

Low-cost, high-safety, and broad-prospect aqueous zinc-manganese batteries (ZMBs) are limited by complex interfacial reactions. The solid-liquid interfacial state of the cathode dominates the Mn dissolution/deposition process of aqueous ZMBs, especially the important influence on the mass and charge transfer behavior of Zn2+ and Mn2+. We proposed a quasi-eutectic electrolyte (QEE) that would stabilize the reversible behavior of interfacial deposition and favorable interfacial reaction kinetic of manganese-based cathodes in a long cycle process by optimizing mass and charge transfer. We emphasize that the initial interfacial reaction energy barrier is not the main factor affecting cycling performance, and the good reaction kinetics induced by interfacial deposition during the cycling process is more conducive to the stable cycling of the battery, which has been confirmed by theoretical analysis, quartz crystal microbalance with dissipation monitoring, depth etching X-ray photon-electron spectroscopy, etc. As a result, the QEE electrolyte maintained a stable specific capacity of 250 mAh g-1 at 0.5 A g-1 after 350 cycles in zinc-manganese batteries. The energy density retention rate of the ZMB with QEE increased by 174% compared to that of conventional aqueous electrolyte. Furthermore, the multi-stacked soft-pack battery with a cathodic mass load of 54.4 mg maintained a stable specific capacity of 200 mAh g-1 for 100 cycles, demonstrating its commercial potential. This work proves the feasibility of adapting lean-water QEE to the stable aqueous ZMBs.

Reversible Multielectron Redox Chemistry in a NASICON-Type Cathode toward High-Energy-Density and Long-Life Sodium-Ion Full Batteries.

Na-superionic-conductor (NASICON)-type cathodes (e.g., Na3 V2 (PO4 )3 ) have attracted extensive attention due to their open and robust framework, fast Na+ mobility, and superior thermal stability. To commercialize sodium-ion batteries (SIBs), higher energy density and lower cost requirements are urgently needed for NASICON-type cathodes. Herein, Na3.5 V1.5 Fe0.5 (PO4 )3 (NVFP) is designed by an Fe-substitution strategy, which not only reduces the exorbitant cost of vanadium, but also realizes high-voltage multielectron reactions. The NVFP cathode can deliver extraordinary capacity (148.2 mAh g-1 ), and decent cycling durability up to 84% after 10 000 cycles at 100 C. In situ X-ray diffraction and ex situ X-ray photoelectron spectroscopy characterizations reveal reversible structural evolution and redox processes (Fe2+ /Fe3+ , V3+ /V4+ , and V4+ /V5+ ) during electrochemical reactions. The low ionic-migration energy barrier and ideal Na+ -diffusion kinetics are elucidated by density functional theory calculations. Combined with electron paramagnetic resonance spectroscopy, Fe with unpaired electrons in the 3d orbital is inseparable from the higher-valence redox activation. More competitively, coupling with a hard carbon (HC) anode, HC//NVFP full cells demonstrate high-rate capability and long-duration cycling lifespan (3000 stable cycles at 50 C), along with material-level energy density up to 304 Wh kg-1 . The present work can provide new perspectives to accelerate the commercialization of SIBs.

Aligned Dipoles Induced Electric-Field Promoting Zinc-Ion De-Solvation toward Highly Stable Dendrite-Free Zinc-Metal Batteries.

Water-induced parasitic reactions and uncontrolled dendritic Zn growth are long-lasting tricky problems that severely hinder the development of aqueous zinc-metal batteries. Those notorious issues are closely related to electrolyte configuration and zinc-ion transport behavior. Herein, through constructing aligned dipoles induced electric-field on Zn surface, both the solvation structure and transport behavior of zinc-ions are fundamentally changed. The vertically ordered zinc-ion migration trajectory and gradually concentrated zinc-ion achieved inside the polarized electric-field remarkably eliminate water related side-reactions and Zn dendrites. Zn-metal under the polarized electric-field demonstrated significantly improve reversibility and a dendrite-free surface with strong (002) Zn deposition texturing. Zn||Zn symmetric cell delivers greatly prolonged lifespan up to 1400 h (17 times longer than that of the cell based on bare Zn) while the Zn||Cu half-cell demonstrate ultrahigh 99.9% coulombic efficiency. NH4 V4 O10 ||Zn half-cell delivered exceptional-high 132 mAh g-1 capacity after ultralong 2000 cycles (≈100% capacity retention). In addition, MnO2 ||Zn pouch-cell under aligned dipoles induced electric-field maintains 87.9% capacity retention after 150 cycles under practical condition of high MnO2 mass loading (≈10 mg cm-2 ) and limited N/P ratio. It is considered that this new strategy can also be implemented to other metallic batteries and spur the development of batteries with long-lifespan and high-energy-density.

Constructing Ionic Self-Concentrated Electrolyte via Introducing Montmorillonite Toward High-Performance Aqueous Zn-MnO2 Batteries.

Aqueous zinc metal batteries are regarded as one of the most promising alternatives to lithium-ion batteries for large-scale energy storage due to the abundant zinc resources, high safety, and low cost. Herein, an ionic self-concentrated electrolyte (ISCE) is proposed to enable uniform Zn deposition and reversible reaction of MnO2 cathode. Benefitting from the compatibility of ISCE with electrodes and its adsorption on the electrode surface for guidance, the Zn/Zn symmetrical batteries exhibit the long-life cycle stability with more than 5000 and 1500 h at 0.2 and 5 mA cm-2 , respectively. The Zn/MnO2 battery also exhibits a high capacity of 351 mA h g-1 at 0.1 A g-1 and can enable a stability over 2000 cycles at 1 A g-1 . This work provides a new insight into electrolyte design for stable aqueous Zn-MnO2 battery.

Achieving Highly Proton-Resistant Zn-Pb Anode through Low Hydrogen Affinity and Strong Bonding for Long-Life Electrolytic Zn//MnO2 Battery.

High-energy electrolytic Zn//MnO2 batteries show potential for grid-scale energy storage, but the severe hydrogen evolution corrosion (HEC) caused by acidic electrolytes results in subdued durability. Here, an all-around protection strategy is reported for achieving stable Zn metal anodes. First, a proton-resistant Pb-containing (Pb and Pb(OH)2 ) interface is constructed on a Zn anode (denoted as Zn@Pb), which in situ forms PbSO4 during H2 SO4 corrosion and protects the Zn substrate from HEC. Second, to improve the plating/stripping reversibility of Zn@Pb, Pb(CH3 COO)2 an additive (denoted as Zn@Pb-Ad) is introduced, which triggers PbSO4 precipitation and releases trace Pb2+ that can dynamically deposit a Pb layer on the Zn plating layer to suppress HEC. The superior HEC resistance stems from the low affinity of PbSO4 and Pb for H+ , as well as strong bonding between Pb-Zn or Pb-Pb, which increase the hydrogen evolution reaction overpotential and the H+ corrosion energy barrier. Consequently, the Zn@Pb-Ad//MnO2 battery runs stably for 630 and 795 h in 0.2 and 0.1 m H2 SO4 electrolytes, respectively, which are >40 times better than that of bare Zn. The as-prepared A h-level battery achieves a one-month calendar life, opening the door to the next generation of high-durable grid-scale Zn batteries.

Biocompatible zinc battery with programmable electro-cross-linked electrolyte.

Aqueous zinc batteries (ZBs) attract increasing attention for potential applications in modern wearable and implantable devices due to their safety and stability. However, challenges associated with biosafety designs and the intrinsic electrochemistry of ZBs emerge when moving to practice, especially for biomedical devices. Here, we propose a green and programmable electro-cross-linking strategy to in situ prepare a multi-layer hierarchical Zn-alginate polymer electrolyte (Zn-Alg) via the superionic binds between the carboxylate groups and Zn2+. Consequently, the Zn-Alg electrolyte provides high reversibility of 99.65% Coulombic efficiency (CE), >500 h of long-time stability and high biocompatibility (no damage to gastric and duodenal mucosa) in the body. A wire-shaped Zn/Zn-Alg/α-MnO2 full battery affords 95% capacity retention after 100 cycles at 1 A g-1 and good flexibility. The new strategy has three prominent advantages over the conventional methods: (i) the cross-linking process for the synthesis of electrolytes avoids the introduction of any chemical reagents or initiators; (ii) a highly reversible Zn battery is easily provided from a micrometer to large scales through automatic programmable functions; and (iii) high biocompatibility is capable of implanted and bio-integrated devices to ensure body safety.

Design Strategies toward High-Performance Zn Metal Anode.

Rechargeable aqueous Zn-ion batteries (AZIBs) are one of the most promising alternatives for traditional energy-storage devices because of their low cost, abundant resources, environmental friendliness, and inherent safety. However, several detrimental issues with Zn metal anodes including Zn dendrite formation, hydrogen evolution, corrosion and passivation, should be considered when designing advanced AZIBs. Moreover, these thorny issues are not independent but mutually reinforcing, covering many technical and processing parameters. Therefore, it is necessary to comprehensively summarize the issues facing Zn anodes and the corresponding strategies to develop roadmaps for the development of high-performance Zn anodes. Herein, the failure mechanisms of Zn anodes and their corresponding impacts are outlined. Recent progress on improving the stability of Zn anode is summarized, including structurally designed Zn anodes, Zn alloy anodes, surface modification, electrolyte optimization, and separator design. Finally, this review provides brilliant and insightful perspectives for stable Zn metal anodes and promotes the large-scale application of AZIBs in power grid systems.

Enzyme-Triggered Size-Switchable Nanosystem for Deep Tumor Penetration and Hydrogen Therapy.

The poor penetration of nanocarriers within tumor dense extracellular matrices (ECM) greatly restricts the access of anticancer drugs to the deep tumor cells, resulting in low therapeutic efficacy. Moreover, the high toxicity of the traditional chemotherapeutics inevitably causes undesirable side effects. Herein, taking the advantages of biosafe H2 and small-sized nanoparticles in diffusion within tumor ECM, we develop a matrix metalloprotease 2 (MMP-2) responsive size-switchable nanoparticle (UAMSN@Gel-PEG) that is composed of ultrasmall amino-modified mesoporous silica nanoparticles (UAMSN) wrapped within a PEG-conjugated gelatin to deliver H2 to the deep part of tumors for effective gas therapy. Ammonia borane (AB) is chosen as the H2 prodrug that can be effectively loaded into UAMSN by hydrogen-bonding adsorption. Gelatin is used as the substrate of MMP-2 to trigger size change and block AB inside UAMSN during blood circulation. PEG is introduced to further increase the particle size and endow the nanoparticle with long blood circulation to achieve effective tumor accumulation via the EPR effect. After accumulation into the tumor site, MMP-2 promptly digests gelatin to expose UAMSN loading AB for deep tumor penetration. Upon stimulation by the acidic tumor microenvironment, AB decomposes into H2 for further intratumor diffusion to achieve effective hydrogen therapy. Consequently, such a simultaneous deep tumor penetration of nanocarriers and H2 results in an evident suppression on tumor growth in a 4T1 tumor-bearing model without any obvious toxicity on normal tissues. Our synthetic nanosystem provides a promising strategy for the development of nanomedicines with enhanced tumor permeability and good biosafety for efficient tumor treatment.

Zincophilic Electrode Interphase with Appended Proton Reservoir Ability Stabilizes Zn Metal Anodes.

The rampant dendrites and hydrogen evolution reaction (HER) resulting from the turbulent interfacial evolution at the anode/electrolyte are the main culprits of short lifespan and low Coulombic efficiency of Zn metal batteries. In this work, a versatile protective coating with excellent zincophilic and amphoteric features is constructed on the surface of Zn metal (ZP@Zn) as dendrite-free anodes. This kind of protective coating possesses the advantages of reversible proton storage and rapid desolvation kinetics, thereby mitigating the HER and facilitating homogeneous nucleation concomitantly. Furthermore, the space charge polarization effect promotes charge redistribution to achieve uniform Zn deposition. Accordingly, the ZP@Zn symmetric cell manifests excellent reversibility at an ultrahigh cumulative plating capacity of 4700 mAh cm-2 and stable cycling at 80 % depth of discharge (DOD). The ZP@Zn//V6 O13 pouch cell also reveals superior cycling stability with a high capacity of 326.6 mAh g-1 .

Interfacial thermodynamics-inspired electrolyte strategy to regulate output voltage and energy density of battery chemistry.

The electrochemical behaviors of battery chemistry, especially the operating voltage, are greatly affected by the complex electrode/electrolyte interface, but the corresponding basis understanding is still largely unclear. Herein, the concept of regulating electrode potential by interface thermodynamics is proposed, which guides the improvement of the energy density of Zn-MnO2 battery. A cationic electrolyte strategy is adopted to adjust the charge density of electrical double layer, as well as entropy change caused by desolvation, thus, achieving an output voltage of 1.6 V (vs. Zn2+/Zn) and a capacity of 400 mAh g-1. The detailed energy storage behaviors are also analyzed in terms of crystal field and energy level splitting. Furthermore, the electrolyte optimization benefits the efficient operation of Zn-MnO2 battery by enabling a high energy density of 532 Wh kg-1 based on the mass of cathode and a long cyclic life of more than 500 cycles. This work provides a path for designing high-energy-density aqueous battery via electrolyte strategy, which is expected to be extended to other battery systems.

Tuning Zn2+ coordination tunnel by hierarchical gel electrolyte for dendrite-free zinc anode.

Aqueous zinc-ion batteries (ZIBs) are perceived as one of the most upcoming grid-scale storage systems. However, the issues of electrode dissolution, dendrite formation, and corrosion in traditional liquid electrolytes have plagued its progress. In this work, Zn dendrite growth and side reactions are effectively suppressed by a highly-confined tannic acid (TA) modified sodium alginate (SA) composite gel electrolyte (TA-SA). The ion-confinement effect is enhanced by divalent zinc ions coordinated with carboxyl groups and chelated with phenolic hydroxyl groups, thus guiding and regulating Zn deposition to achieve steady zinc plating/stripping behavior. As a consequence, the Zn/TA-SA/NH4V4O10 full cells deliver a high specific capacity of 238.6 mAh g-1 and maintain 94.51% over 900 cycles at 2 A g-1. Notably, after resting over 5 d, the capacity can be stabilized with a capacity retention of 97.25% after 200 cycles at 2 A g-1. This highly-confined and hydrogen bond-strengthened gel electrolyte may provide an effective strategy for the future development of quasi-solid-state metal batteries.

A smelting-rolling strategy for ZnIn bulk phase alloy anodes.

Reversibility and stability are considered as the key indicators for Zn metal anodes in aqueous Zn-ion batteries, yet they are severely hindered by uncontrolled Zn stripping/plating and side reactions. Herein, we fabricate a bulk phase ZnIn alloy anode containing trace indium by a typical smelting-rolling process. A uniformly dispersed bulk phase of the whole Zn anode is constructed rather than only a protective layer on the surface. The Zn deposition can be regarded as instantaneous nucleation due to the adsorption of the evenly dispersed indium, and formation of the exclusion zone for further nucleation can be prevented at the same time. Owing to the bulk phase structure of ZnIn alloy, the indium not only plays a crucial role in Zn deposition, but also improves the Zn stripping. Consequently, the as-designed ZnIn alloy anode can sustain stable Zn stripping/plating for over 2500 h at 4.4 mA cm-2 with nearly 6 times smaller voltage hysteresis than that of pure Zn. Moreover, it enables a substantially stable ZnIn//NH4V4O10 battery with 96.44% capacity retention after 1000 cycles at 5 A g-1. This method of regulating the Zn nucleation by preparing a Zn-based alloy provides a potential solution to the critical problem of Zn dendrite growth and by-product generation fundamentally.

In/Ce Co-doped Li3VO4 and Nitrogen-modified Carbon Nanofiber Composites as Advanced Anode Materials for Lithium-ion Batteries.

Li3VO4 (LVO) is considered as a novel alternative anode material for lithium-ion batteries (LIBs) due to its high capacity and good safety. However, the inferior electronic conductivity impedes its further application. Here, nanofibers (nLICVO/NC) with In/Ce co-doped Li3VO4 strengthened by nitrogen-modified carbon are prepared. Density functional theory calculations demonstrate that In/Ce co-doping can substantially reduce the LVO band gap and achieve orders of magnitude increase (from 2.79 × 10-4 to 1.38 × 10-2 S cm-1) in the electronic conductivity of LVO. Moreover, the carbon-based nanofibers incorporated with 5LICVO nanoparticles can not only buffer the structural strain but also form a good framework for electron transport. This 5LICVO/NC material delivers high reversible capacities of 386.3 and 277.9 mA h g-1 at 0.1 and 5 A g-1, respectively. Furthermore, high discharge capacities of 335 and 259.5 mA h g-1 can be retained after 1200 and 4000 cycles at 0.5 and 1.6 A g-1, respectively (with the corresponding capacity retention of 98.4 and 78.7%, respectively). When the 5LICVO/NC anode assembles with commercial LiNi1/3Co1/3Mn1/3O2 (NCM111) into a full cell, a high discharge capacity of 191.9 mA h g-1 can be retained after 600 cycles at 1 A g-1, implying an inspiring potential for practical application in high-efficiency LIBs.

Balanced Interfacial Ion Concentration and Migration Steric Hindrance Promoting High-Efficiency Deposition/Dissolution Battery Chemistry.

The solid-liquid transition reaction lays the foundation of electrochemical energy storage systems with high capacity, but realizing high efficiency remains a challenge. Herein, in terms of thermodynamics and dynamics, this work demonstrates the significant role of both interfacial H+ concentration and Mn2+ migration steric hindrance for the high-efficiency deposition/dissolution chemistry of zinc-manganese batteries. Specially, the introduction of formate anions can buffer the generated interfacial H+ to stabilize interfacial potential according to the Nernst equation, which stimulates high capacity. Compared with acetate and propionate anions, the formate anion also provides high adsorption density on the cathode surface to shield the electrostatic repulsion due to the small spatial hindrance. Particularly for the solvated Mn2+ , the formate-anion-induced lower energy barrier of the rate-determining step during the step-by-step desolvation process results in lower polarization and higher electrochemical reversibility. In situ tests and theoretical calculations verify that the electrolyte with formate anions achieve a good balance between ion concentration and ion-migration steric hindrance. It exhibits both the high energy density of 531.26 W h kg-1  and long cycle life of more than 300 cycles without obvious decay.

Recent Progress on Phosphate Cathode Materials for Aqueous Zinc-Ion Batteries.

Rechargeable zinc-ion batteries (ZIBs) are attractive for large-scale energy storage due to their superiority in resources, safety, and environmental friendliness. However, the lack of suitable ZIBs cathode materials limits their practical applications. In consideration of the excellent electrochemical performance of phosphate materials in monovalent ion (Li+ , Na+ ) batteries, they were also employed as ZIBs cathode materials recently and performed well with high potential. But they also suffer from low capacity and poor conductivity, and the energy storage mechanism is not clear yet. This Review provides a state-of-the art overview on the developments of phosphate cathode materials in ZIBs, including NASICON-type phosphates, fluorophosphates, olivine-structured, layered-structured, and novel-structured phosphate materials mainly. This study presents the reaction mechanism and electrochemical performance of phosphate cathode materials in aqueous ZIBs, and future research directions are discussed, which are intended to provide guidance for exploring high-potential cathode materials for ZIBs.