Multi-Ion Engineering Strategies toward High Performance Aqueous Zinc-Based Batteries

Insights into Mechanistic Aspect of Organic Materials for Aluminum-Ion Batteries

Rechargeable aluminum-ion batteries (AIBs) with organic electrode materials have garnered significant attention due to their excellent safety profile, cost-effectiveness, and eco-friendly nature. This review examines the fundamental properties of organic compounds and their effects on battery performance, with a primary focus on how changes in ion interactions and charge storage mechanisms at active sites influence overall performance. The aim is to propose innovative design approaches for AIBs that overcome the constraints associated with various types of organic materials. The review also discusses the application of advanced analytical tools, providing insights to better understand the electrochemical process of AIBs.

Epitaxial Electrodeposition of Zinc on Different Single Crystal Copper Substrates for High Performance Aqueous Batteries

The aqueous zinc metal battery holds great potential for large-scale energy storage due to its safety, low cost, and high theoretical capacity. However, challenges such as corrosion and dendritic growth necessitate controlled zinc deposition. This study employs epitaxy to achieve large-area, dense, and ultraflat zinc plating on textured copper foil. High-quality copper foils with Cu(100), Cu(110), and Cu(111) facets were prepared and systematically compared. The results show that Cu(111) is the most favorable for zinc deposition, offering the lowest nucleation overpotential, diffusion energy, and interfacial energy with a Coulombic efficiency (CE) of 99.93%. The study sets a record for flat-zinc areal loading at 20 mAh/cm2. These findings provide some clarity on the best-performing copper and zinc crystalline facets, with Cu(111)/Zn(0002) ranking the highest. Using a MnO2-Zn full cell model, the research achieved an exceptional cycle life of over 800 cycles in a cathode-anode-free battery configuration.

Achieving Uniform Deposition of Zn with Amide Additives for Metal Anodes Stabilization

The practical applications of aqueous zinc-ion batteries (AZIBs) are hindered by detrimental effects such as dendrites formation at the Zn metal anode interface and parasitic side reactions induced by H2O. Hence, we propose adding amide additives to the Zn sulfate electrolyte (ZSO) to regulate the composition and properties of the electrolytes, thereby stabilizing the Zn anode interface. Different amide molecules containing formamide (FA), acetamide (AA), or trifluoroacetamide (TFA) are discussed. The polar C═O group shared by amide molecules can interact with Zn2+, forming their solvation shells. The molecules can also facilitate the transport of Zn2+ and increase the conductivity of the electrolytes. Additionally, amide molecules can interact with H2O through hydrogen bonds to limit the erosion of active H2O on the Zn anode. The unique -H, -CH3, and -CF3 groups of the molecules result in different polarities and varying numbers of interaction sites with H2O and Zn2+, leading to some differences in the protective effects of the Zn anode. The stability and lifespan of Zn||Zn batteries assembled with amide electrolytes have significantly improved, especially those with TFA. Moreover, the Zn||NH4V4O10 full cells demonstrate remarkable capacity retention, and the overall performance of the batteries has also been enhanced.

Towards Superior Aqueous Zinc-Ion Batteries: The Insights of Artificial Protective Interfaces

Aqueous zinc ion batteries (AZIBs) with metallic Zn anode have the potential for large-scale energy storage application due to their cost-effectiveness, safety, environmental-friendliness, and ease of preparation. However, the concerns regarding dendrite growth and side reactions on Zn anode surface hamper the commercialization of AZIBs. This review aims to give a comprehensive evaluation of the protective interphase construction and provide guidance to further improve the electrochemical performance of AZIBs. The failure behaviors of the Zn metal anode including dendrite growth, corrosion, and hydrogen evolution are analyzed. Then, the applications and mechanisms of the constructed interphases are introduced, which are classified by the material species. The fabrication methods of the artificial interfaces are summarized and evaluated, including the in-situ strategy and ex-situ strategy. Finally, the characterization means are discussed to give a full view for the study of Zn anode protection. Based on the analysis of this review, a stable and high-performance Zn anode could be designed by carefully choosing applied material, corresponding protective mechanism, and appropriate construction technique. Additionally, this review for Zn anode modification and construction techniques for anode protection in AZIBs may be helpful in other aqueous metal batteries with similar problems.

Hydrophobic Ion Barrier-Enabled Ultradurable Zn (002) Plane Orientation towards Long-Life Anode-Less Zn Batteries

Gradual disability of Zn anode and high negative/positive electrode (N/P) ratio usually depreciate calendar life and energy density of aqueous Zn batteries (AZBs). Herein, within original Zn2+-free hydrated electrolytes, a steric hindrance/electric field shielding-driven "hydrophobic ion barrier" is engineered towards ultradurable (002) plane-exposed Zn stripping/plating to solve this issue. Guided by theoretical simulations, hydrophobic adiponitrile (ADN) is employed as a steric hindrance agent to ally with inert electric field shielding additive (Mn2+) for plane adsorption priority manipulation, thereby constructing the "hydrophobic ion barrier". This design robustly suppresses the (002) plane/dendrite growth, enabling ultradurable (002) plane-exposed dendrite-free Zn stripping/plating. Even being cycled in Zn‖Zn symmetric cell over 2150 h at 0.5 mA cm-2, the efficacy remains well-kept. Additionally, Zn‖Zn symmetric cells can be also stably cycled over 918 h at 1 mA cm-2, verifying uncompromised Zn stripping/plating kinetics. As-assembled anode-less Zn‖VOPO4 ⋅ 2H2O full cells with a low N/P ratio (2 : 1) show a high energy density of 75.2 Wh kg-1 full electrode after 842 cycles at 1 A g-1, far surpassing counterparts with thick Zn anode and low cathode loading mass, featuring excellent practicality. This study opens a new avenue by robust "hydrophobic ion barrier" design to develop long-life anode-less Zn batteries.

Tunneling Proton Grotthuss Transfer Channels by Hydrophilic-Zincophobic Heterointerface Shielding for High-Performance Zn-MnO2 Batteries

Hollandite-type manganese dioxide (α-MnO2) is recognized as a promising cathode material upon high-performance aqueous zinc-ion batteries (ZIBs) owing to the high theoretical capacities, high working potentials, unique Zn2+/H+ co-insertion chemistry, and environmental friendliness. However, its practical applications limited by Zn2+ accommodation, where the strong coulombic interaction and sluggish kinetics cause significant lattice deformation, fast capacity degradation, insufficient rate capability, and undesired interface degradation. It remains challenging to accurately modulate H+ intercalation while suppressing Zn2+ insertion for better lattice stability and electrochemical kinetics. Herein, proton Grotthuss transfer channels are first tunneled by shielding MnO2 with hydrophilic-zincophobic heterointerface, fulfilling the H+-dominating diffusion with the state-of-the-art ZIBs performance. Local atomic structure and theoretical simulation confirm that surface-engineered α-MnO2 affords to the synergy of Mn electron t2g-eg activation, oxygen vacancy enrichment, selective H+ Grotthuss transfer, and accelerated desolvation kinetics. Consequently, fortified α-MnO2 achieves prominent low current density cycle stability (≈100% capacity retention at 1 C after 400 cycles), remarkable long-lifespan cycling performance (98% capacity retention at 20 C after 12 000 cycles), and ultrafast rate performance (up to 30 C). The study exemplifies a new approach of heterointerface engineering for regulation of H+-dominating Grotthuss transfer and lattice stabilization in α-MnO2 toward reliable ZIBs.

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.

Spin Symmetry Breaking-Induced Hubbard Gap Near-Closure in N-Coordinated MnO2 for Enhanced Aqueous Zinc-Ion Battery Performance

Transition metal oxides (TMOs) are promising cathode materials for aqueous zinc ion batteries (ZIBs), however, their performance is hindered by a substantial Hubbard gap, which limits electron transfer and battery cyclability. Addressing this, we introduce a heteroatom coordination approach, using triethanolamine to induce axial N coordination on Mn centers in MnO2, yielding N-coordinated MnO2 (TEAMO). This approach leverages the change of electronegativity disparity between Mn and ligands (O and N) to disrupt spin symmetry and augment spin polarization. This enhancement leads to the closure of the Hubbard gap, primarily driven by the intensified occupancy of the Mn eg orbitals. The resultant TEAMO exhibit a significant increase in storage capacity, reaching 351 mAh g-1 at 0.1 A g-1. Our findings suggest a viable strategy for optimizing the electronic structure of TMO cathodes, enhancing the potential of ZIBs in energy storage technology.

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.

Insights into the cycling stability of manganese-based zinc-ion batteries: from energy storage mechanisms to capacity fluctuation and optimization strategies

Manganese-based materials are considered as one of the most promising cathodes in zinc-ion batteries (ZIBs) for large-scale energy storage applications owing to their cost-effectiveness, natural availability, low toxicity, multivalent states, high operation voltage, and satisfactory capacity. However, their intricate energy storage mechanisms coupled with unsatisfactory cycling stability hinder their commercial applications. Previous reviews have primarily focused on optimization strategies for achieving high capacity and fast reaction kinetics, while overlooking capacity fluctuation and lacking a systematic discussion on strategies to enhance the cycling stability of these materials. Thus, in this review, the energy storage mechanisms of manganese-based ZIBs with different structures are systematically elucidated and summarized. Next, the capacity fluctuation in manganese-based ZIBs, including capacity activation, degradation, and dynamic evolution in the whole cycle calendar are comprehensively analyzed. Finally, the constructive optimization strategies based on the reaction chemistry of one-electron and two-electron transfers for achieving durable cycling performance in manganese-based ZIBs are proposed.

MOF-modified dendrite-free gel polymer electrolyte for zinc-ion batteries

Zinc-ion batteries are promising candidates for large-scale energy storage, and gel polymer electrolytes (GPEs) play an important role in zinc-ion battery applications. Metal-organic frameworks (MOFs) are characterized by large specific surface areas and ordered pores. This highly ordered microporous structure provides a continuous transport channel for ions, thus realizing the high-speed transmission of ions. In this paper, an MOF-modified dendrite-free GPE was designed. The incorporation of MOF particles not only reduces the crystallinity of the polymer, increases the motility of the molecular chains, and facilitates the transfer of Zn2+, but also attracts anions to reduce polarization during electrochemical reactions. It was shown that this MOF-modified gel polymer electrolyte has a higher ionic conductivity compared to other PVDF-based polymer electrolytes (approximate range of 2 × 10-4 to 3 × 10-3 S cm-1), with a very high conductivity (1.63 mS cm-1) even at -20 °C. The Zn/Zn symmetric cell could maintain operation for more than 3600 h at a current density of 1 mA cm-2, and SEM showed that the MOF-modified gel electrolyte had uniform Zn2+ deposition.

Non-Metal Ion Storage in Zinc-Organic Batteries

Zinc-organic batteries (ZOBs) are receiving widespread attention as up-and-coming energy-storage systems due to their sustainability, operational safety and low cost. Charge carrier is one of the critical factors affecting the redox kinetics and electrochemical performances of ZOBs. Compared with conventional large-sized and sluggish Zn2+ storage, non-metallic charge carriers with small hydrated size and light weight show accelerated interfacial dehydration and fast reaction kinetics, enabling superior electrochemical metrics for ZOBs. Thus, it is valuable and ongoing works to build better ZOBs with non-metallic ion storage. In this review, versatile non-metallic cationic (H+, NH4 +) and anionic (Cl-, OH-, CF3SO3 -, SO4 2-) charge carriers of ZOBs are first categorized with a brief comparison of their respective physicochemical properties and chemical interactions with redox-active organic materials. Furthermore, this work highlights the implementation effectiveness of non-metallic ions in ZOBs, giving insights into the impact of ion types on the metrics (capacity, rate capability, operation voltage, and cycle life) of organic cathodes. Finally, the challenges and perspectives of non-metal-ion-based ZOBs are outlined to guild the future development of next-generation energy communities.

Na+ Preintercalated MoO3 Microrods for Aqueous Zinc/Sodium Batteries with Enhanced Performance

Layered molybdenum trioxide (MoO3) is being investigated as a cathode material with high theoretical capacity and holds promise for aqueous secondary batteries. Unfortunately, the severe structural degradation of MoO3 and insufficient intrinsic properties hinder its practical application. Herein, a Na+ preintercalation strategy is reported as an effective method to construct cathodes with high performance for aqueous zinc/sodium batteries (AZSBs). Compared with pristine MoO3, the Na+ preintercalated Na0.25MoO3 cathode delivers a reversible capacity of 251.1 mAh g-1 at 1 A g-1, achieves a capacity retention of 79.2% after 500 cycles, and exhibits a high rate capability (121.5 mAh g-1 at 20 A g-1), which is superior to that in most of the previous reports. Through the experimental measurements and density functional theory (DFT) calculations, the preintercalation method could shorten the forbidden band gap and modulate the electronic structure and hence effectively inhibit the structural collapse of MoO3 microrods, induce reversible Na+ insertion, and enhance the discharge potential. This work is of significance for further research on molybdenum-based compounds as cathode materials for aqueous secondary batteries.

Hybrid Superlattice-Triggered Selective Proton Grotthuss Intercalation in δ-MnO2 for High-Performance Zinc-Ion Battery

A great deal of attention has been paid on layered manganese dioxide (δ-MnO2 ) as promising cathode candidate for aqueous zinc-ion battery (ZIB) due to the excellent theoretical capacity, high working voltage and Zn2+ /H+ co-intercalation mechanism. However, caused by the insertion of Zn2+ , the strong coulomb interaction and sluggish diffusion kinetics have resulted in significant structure deformation, insufficient cycle stability and limited rate capability. And it is still far from satisfactory to accurately modulate H+ intercalation for superior electrochemical kinetics. Herein, the terrace-shape δ-MnO2 hybrid superlattice by polyvinylpyrrolidone (PVP) pre-intercalation (PVP-MnO2 ) was proposed with the state-of-the-art ZIBs performance. Local atomic structure characterization and theoretical calculations have been pioneering in confirming the hybrid superlattice-triggered synergy of electron entropy stimulation and selective H+ Grotthuss intercalation. Accordingly, PVP-MnO2 hybrid superlattice exhibits prominent specific capacity (317.2 mAh g-1 at 0.125 A g-1 ), significant rate performance (106.1 mAh g-1 at 12.5 A g-1 ), and remarkable cycle stability at high rate (≈100 % capacity retention after 20,000 cycles at 10 A g-1 ). Therefore, rational design of interlayer configuration paves the pathways to the development of MnO2 superlattice for advanced Zn-MnO2 batteries.