Ammonium-Ion Storage Using Electrodeposited Manganese Oxides

Mo modulating the structure of monoclinic vanadium dioxide boosting the aqueous ammonium-ion storage for high-performance supercapacitor

Supercapacitors (SCs) using ammonium-ion (NH4+) as the charge carrier (NH4+-SCs) have attracted continuous attention and vanadium-based materials are proved to have high-efficient NH4+-storage properties. Monoclinic vanadium dioxide, VO2(B), as an anode material applied to SCs has been rarely reported and modulating its electronic structure for boosted NH4+-storage is full of challenge. In this work, molybdenum-doped VO2(B) (Mo-doped VO2(B)) is designed and synthesize to enhance its NH4+-storage. The introduction of Mo atom into the crystal structure of VO2(B) can modulate its crystal structure and bring in some defects. Experimental results manifest that Mo-doped VO2(B) with 2 % Mo-doping shows the best electrochemical properties. Mo-doped VO2(B) achieves the specific capacitance of 1403 F g-1 (390 mAh g-1) at 0.1 A g-1 and the capacitance retention of about 98 % after 5000 cycle, superior to that of VO2(B) (893 F g-1, 248 mAh g-1 at 0.1 A g-1 and 60 % capacitance retention. The hybrid supercapacitor (HSC) assembled by Mo-doped VO2(B) and active carbon delivers good electrochemical performance with the energy density of 38.6 Wh kg-1 at power density of 208.3 W kg-1. This work proves that the Mo-doping is an efficient strategy for boosted NH4+-storage of VO2(B) and this strategy is like a Chinese idiom "like adding wings to a tiger" to guide the design of electrode materials for high-efficient NH4+-storage.

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.

Topochemical behavior of ferrocene embedded in V2O5·nH2O with weak hydrogen bonding enhancing ammonium-ion storage

Aqueous ammonium ion batteries (AAIBs) are garnering increasing attention due to their utilization of abundant resources, cost-effectiveness, safety, and unique energy storage mechanism. The pursuit of high-performance cathode materials has become a pressing issue. In this study, we propose and synthesize ferrocene-embedded hydrated vanadium pentoxide (Fer/VOH) for implementation in AAIBs. The inclusion of ferrocene serves to expand the interlayer spacing, mitigate interlayer forces, and introduce the electron-rich environment characteristic of ferrocene. This augmentation facilitates the creation of additional oxygen vacancies, substantially enhancing the capacity and efficiency of ammonium ion storage. Notably, our investigation reveals that the incorporation of ferrocene attenuates the hydrogen bonding interactions associated with ammonium ions, rendering them more amenable to the interlayer embedding and release processes. Building upon these advantages, Fer/VOH exhibits a specific capacity of 313 mAh/g at a current density of 0.2 A/g, representing the highest reported performance among vanadium oxides utilized in AAIBs to date. Even after 2000 charge/discharge cycles at a current density of 2 A/g, Fer/VOH maintains a reversible specific capacity of 89 mAh/g, with a capacity retention rate of 54.8%. This study confirms the viability of Fer/VOH as a cathode material for AAIBs and offers a novel approach to enhancing the electrical conductivity and diminishing the hydrogen bonding forces in vanadium oxide intercalation through the embedding of electron-rich species and positronic groups.

An Ultrastable Aqueous Ammonium-Ion Battery Using a Covalent Organic Framework Anode

Aqueous ammonium ion batteries have garnered significant research interest due to their safety and sustainability advantages. However, the development of reliable ammonium-based full batteries with consistent electrochemical performance, particularly in terms of cycling stability, remains challenging. A primary issue stems from the lack of suitable anode materials, as the relatively large NH4 + ions can cause structural damage and material dissolution during battery operation. To address this challenge, an Aza-based covalent organic framework (COF) material is introduced as an anode for aqueous ammonium ion batteries. This material exhibits superior ammonium storage capabilities compared to existing anode materials. It operates effectively within a negative potential range of 0.3 to‒1.0 V versus SCE, achieves high capacity even at elevated current densities (≈74 mAh g-1 at 10 A g-1), and demonstrates exceptional stability, retaining a capacity over 20 000 cycles at 1.0 A g-1. Furthermore, by pairing this COF anode with a Prussian blue cathode, an ammonium rocking-chair full battery is developedd that maintains 89% capacity over 20 000 cycles at 1.0 A g-1, surpassing all previously reported ammonium ion full batteries. This study offers insights for the design of future anodes for ammonium ion batteries and holds promise for high-energy storage solutions.

Emerging Two-Dimensional Materials for Proton-Based Energy Storage

The rapid diffusion kinetics and smallest ion radius make protons the ideal cations toward the ultimate energy storage technology combining the ultrafast charging capabilities of supercapacitors and the high energy densities of batteries. Despite the concept existing for centuries, the lack of satisfactory electrode materials hinders its practical development. Recently, the rapid advancement of the emerging two-dimensional (2D) materials, characterized by their ultrathin morphology, interlayer van der Waals gaps, and distinctive electrochemical properties, injects promises into future proton-based energy storage systems. In this perspective, we comprehensively summarize the current advances in proton-based energy storage based on 2D materials. We begin by providing an overview of proton-based energy storage systems, including proton batteries, pseudocapacitors and electrical double layer capacitors. We then elucidate the fundamental knowledge about proton transport characteristics, including in electrolytes, at electrolyte/electrode interfaces, and within electrode materials, particularly in 2D material systems. We comprehensively summarize specific cases of 2D materials as proton electrodes, detailing their design concepts, proton transport mechanism and electrochemical performance. Finally, we provide insights into the prospects of proton-based energy storage systems, emphasizing the importance of rational design of 2D electrode materials and matching electrolyte systems.

Investigating the NH4+ Preintercalation and Surface Coordination Effects on MnO2 for Ammonium-Ion Supercapacitors

Ion preintercalation is an effective method for fine-tuning the electrochemical characteristics of electrode materials, thereby enhancing the performance of aqueous ammonium-ion hybrid supercapacitors (A-HSCs). However, much of the current research on ion preintercalation lacks controllability, and the underlying mechanisms remain unclear. In this study, we employ a two-step electrochemical activation approach, involving galvanostatic charge-discharge and cyclic voltammetry, to modulate the preintercalation of NH4+ in MnO2. An in-depth analysis of the electrochemical activation mechanism is presented. This two-step electrochemical activation approach endows the final MnO2/AC electrode with a high capacitance of 917.4 F g-1, approximately 2.4 times higher than that of original MnO2. Furthermore, the MnO2/AC electrode retains approximately 93.4% of its capacitance after 10 000 cycles at a current density of 25 mA cm-2. Additionally, aqueous A-HSC, comprising MnO2/AC and P-MoO3, achieves a maximum energy density of 87.6 Wh kg-1. This study offers novel insights into the controllable ion preintercalation approach via electrochemical activation.

'Beyond Li-ion technology'-a status review

Li-ion battery is currently considered to be the most proven technology for energy storage systems when it comes to the overall combination of energy, power, cyclability and cost. However, there are continuous expectations for cost reduction in large-scale applications, especially in electric vehicles and grids, alongside growing concerns over safety, availability of natural resources for lithium, and environmental remediation. Therefore, industry and academia have consequently shifted their focus towards 'beyond Li-ion technologies'. In this respect, other non-Li-based alkali-ion/polyvalent-ion batteries, non-Li-based all solid-state batteries, fluoride-ion/ammonium-ion batteries, redox-flow batteries, sand batteries and hydrogen fuel cells etc. are becoming potential cost-effective alternatives. While there has been notable swift advancement across various materials, chemistries, architectures, and applications in this field, a comprehensive overview encompassing high-energy 'beyond Li-ion' technologies, along with considerations of commercial viability, is currently lacking. Therefore, in this review article, a rationalized approach is adopted to identify notable 'post-Li' candidates. Their pros and cons are comprehensively presented by discussing the fundamental principles in terms of material characteristics, relevant chemistries, and architectural developments that make a good high-energy 'beyond Li' storage system. Furthermore, a concise summary outlining the primary challenges of each system is provided, alongside the potential strategies being implemented to mitigate these issues. Additionally, the extent to which these strategies have positively influenced the performance of these 'post-Li' technologies is discussed.

One-step hydrothermal synthesis of vanadium dioxide/carbon core-shell composite with improved ammonium ion storage for aqueous ammonium-ion battery

Aqueous nonmetallic ion batteries have garnered significant interest due to their cost-effectiveness, environmental sustainability, and inherent safety features. Specifically, ammonium ion (NH4+) as a charge carrier has garnered more and more attention recently. However, one of the persistent challenges is enhancing the electrochemical properties of vanadium dioxide (VO2) with a tunnel structure, which serves as a highly efficient NH4+ (de)intercalation host material. Herein, a novel architecture, wherein carbon-coated VO2 nanobelts (VO2@C) with a core-shell structure are engineered to augment NH4+ storage capabilities of VO2. In detail, VO2@C is synthesized via the glucose reduction of vanadium pentoxide under hydrothermal conditions. Experimental results manifest that the introduction of the carbon layer on VO2 nanobelts can enhance mass transfer, ion transport and electrochemical kinetics, thereby culminating in the improved NH4+ storage efficiency. VO2@C core-shell composite exhibits a remarkable specific capacity of ∼300 mAh/g at 0.1 A/g, which is superior to that of VO2 (∼238 mAh/g) and various other electrode materials used for NH4+ storage. The NH4+ storage mechanism can be elucidated by the reversible NH4+ (de)intercalation within the tunnel of VO2, facilitated by the dynamic formation and dissociation of hydrogen bonds. Furthermore, when integrated into a full battery with polyaniline (PANI) cathode, the VO2@C//PANI full battery demonstrates robust electrochemical performances, including a specific capacity of ∼185 mAh·g-1 at 0.2 A·g-1, remarkable durability of 93 % retention after 1500 cycles, as well as high energy density of 58 Wh·kg-1 at 5354 W·kg-1. This work provides a pioneering approach to design and explore composite materials for efficient NH4+ storage, offering significant implications for future battery technology enhancements.

Regulation of Electron Delocalization Region in 2D Heteroligand-Based Copper-Organic Framework to Enhance NH 4 + $ \rm {NH_{4}}{^+}$ Charge Storage

The rechargeable aqueous ammonium ion battery shows great potential in low-cost energy storage system because of its long life and environmental friendliness. However, most inorganic host materials used in ammonium ion batteries are still limited by slow diffusion kinetics. Herein, it is identified that a 2D heteroligand-based copper-organic framework featuring numerous ammonium ion adsorption site in the π-conjugated periodic skeleton supplies multiple accessible redox-active sites for high-performance ammonium storage. Benefitting from the effective regulation of electron delocalization by heteroligand and the inherent hydrogen bond cage mechanism between ammonium ions, the resultant full battery delivers a large specific energy density of 211.84 Wh kg-1, and it can be stably operated for 12000 cycles at 5 A g-1 for over 80 days. This explanatory understanding provides a new idea for the rational design of high-performance MOF-based ammonium ion battery cathode materials for efficient energy storage and conversion in the future.

Enhancing ammonium-ion storage in Mo-doped VO2 (B) nanobelt-bundles anode for aqueous ammonium-ion batteries

The recent surge in interest in aqueous ammonium ion rechargeable batteries (AAIBs) has been fueled by their eco-friendliness, efficiency, safety, and sustainability. However, finding the optimal anode material for effective ammonium ion (NH4+) storage remains a nascent and significant challenge. The research presented here focuses on the enhancement of aqueous ammonium rechargeable batteries by incorporating Mo atoms into VO2 (B) (denote as MVO), a material that has shown promise as an anode for NH4+ storage. The introduction of Mo ions was found to optimize the electronic structure and morphology of pristine VO2 (B) (label as PVO), resulting in the transformation of its nanobelts into thin nanobelt-bundles. This alteration exposes more active sites and increases oxygen vacancies, which in turn improve the conductivity and diffusion rate of NH4+ ions, thereby enhancing the overall electrochemical performance of the material. The MVO material demonstrates a high initial capacity of 283.5 mA h g-1 at 0.3 A g-1, and maintained 86.7% of its capacity after 4500 cycles, indicating excellent long-term stability. To further validate the practical application, a full cell was garnered utilizing MVO as the anode and Cu3[Fe(CN)6]2 (CuHCF) as the cathode. The resulting AAIB displays remarkable cycling stability, with 81.5% capacity preservation after 1000 cycles and large energy density of 57.9 W h kg-1. The study reveals that the doping of Mo ions can significantly improve both the stability and NH4+ storage capacity of PVO, offering a promising new direction for the exploitation of efficacious and sustainable NH4+ host materials for rechargeable batteries.

Self-reporting electroswitchable colorimetric platform for smart ammonium recovery from wastewater

Recovery of ammonium from wastewater represents a sustainable strategy within the context of global resource depletion, environmental pollution and carbon neutralization. The present study developed an advanced self-reporting electroswitchable colorimetric platform (SECP) to realize smart ammonium recovery based on the electrically stimulated transformation of Prussian blue/Prussian white (PB/PW) redox couple. The key to SECP was the selectivity of ammonium adsorption, sensitivity of desorption to electric signals and visualability of color change during switchable adsorption/desorption transformation. The results demonstrated the electrochemical intercalation-induced selective adsorption of NH4+ (selectivity coefficient of 3-19 versus other cations) and deintercalation-induced desorption on the PB-film electrode. At applied voltage of 1.2 V for 20 min, the negatively charged PB-film electrode achieved the maximum adsorption capacity of 3.2 mmol g-1. Reversing voltage to -0.2 V for 20 min resulted in desorption efficiency as high as 99%, indicating high adsorption/desorption reversibility and cyclic stability. The Fe(III)/Fe(II) redox dynamics were responsible for PB/PW transformation during reversible intercalation/deintercalation of NH4+. Based on the blue/transparence color change of PB/PW, the quantitative relationship was established between amounts of NH4+ adsorbed and extracted RGB values by multiple linear regression (R2 = 0.986, RMSE = 0.095). Then, the SECP was created upon the unique capability of real-time monitoring and feedback of color change of electrode to realize the automatic control of NH4+ adsorption/desorption. During five cycles of tests, the adsorption process consistently peaked at an average value of 3.15±0.04 mmol g-1, while desorption reliably approached the near-zero average of 0.06±0.04 mmol g-1. The average time of duration was 19.6±1.67 min for adsorption and 18.8±1.10 min for desorption, respectively. With electroswitchability, selectivity and self-reporting functionalities, the SECP represents a paradigm shift in smart ammonium recovery from wastewater, making wastewater treatment and resource recovery more efficient, more intelligent and more sustainable.

A Short-Range Ordered α-MoO3 with Modulated Interlayer Structure via Hydrogen Bond Chemistry for NH4 + Storage

The layered orthorhombic molybdenum trioxide (α-MoO3) is a promising host material for NH4 + storage. But its electrochemical performances are still unsatisfactory due to the absence of fundamental understanding on the relationship between structure and property. Herein, NH4 + storage properties of α-MoO3 are elaborately studied. Electrochemistry together with ex situ physical characterizations uncover that irreversible H+/NH4 + co-intercalation in the initial cycle confines the electrochemically reactive domain to the near surface of α-MoO3 thus resulting in a low reversible NH4 + storage capacity. This issue can be resolved by decreasing ion diffusion pathway to construct short-range ordered α-MoO3 (SMO), which improves the specific capacity to 185 mAh g-1. SMO suffers from dissolution issue. In view of this the interlayer structure of SMO is reconstructed via hydrogen bond chemistry to reinforce the structural stability and it is discovered that the hydrogen bond network only with moderate intensity endows SMO with both high capacity and ability against dissolution. This work presents a new avenue to improve the NH4 + storage properties of α-MoO3 and highlights the important role of hydrogen bond intensity in optimizing electrochemical properties.

Investigations on Tunnel-Structure MnO2 for Utilization as a High-Voltage and Long-Life Cathode Material in Aqueous Ammonium-Ion and Hybrid-Ion Batteries

Recently, nonmetal NH4 + ions have attracted extensive attention for use as charge carries in the field of energy storage due to their abundant resources, environmental friendliness, and low cost. However, the development of aqueous ammonium-ion batteries (AAIBs) is constrained by the absence of high-voltage and long-life materials. Herein, different tunnel-structure MnO2 materials (α-, β-, and γ-MnO2) are utilized as cathodes for AAIBs and hybrid-ion batteries and compared, and α-MnO2 is demonstrated to exhibit the most remarkable electrochemical performance. The α-MnO2 cathode material delivers the highest discharge capacity of 219 mAh g-1 at a current density of 0.1 A g-1 and the best cyclability with a capacity retention of 95.4% after 10 000 cycles at 1.0 A g-1. Moreover, aqueous ammonium-ion and hybrid-ion (ammonium/sodium ions) full batteries are successfully constructed using α-MnO2 cathodes. This work provides a novel direction for the development of aqueous energy storage for practical applications.

Ammonium Ion-Pre-Intercalated MnO2 on Carbon Cloth for High-Energy Density Asymmetric Supercapacitors

With the continuous development of green energy, society is increasingly demanding advanced energy storage devices. Manganese-based asymmetric supercapacitors (ASCs) can deliver high energy density while possessing high power density. However, the structural instability hampers the wider application of manganese dioxide in ASCs. A novel MnO2-based electrode material was designed in this study. We synthesized a MnO2/carbon cloth electrode, CC@NMO, with NH4+ ion pre-intercalation through a one-step hydrothermal method. The pre-intercalation of NH4+ stabilizes the MnO2 interlayer structure, expanding the electrode stable working potential window to 0-1.1 V and achieving a remarkable mass specific capacitance of 181.4 F g-1. Furthermore, the ASC device fabricated using the CC@NMO electrode and activated carbon electrode exhibits excellent electrochemical properties. The CC@NMO//AC achieves a high energy density of 63.49 Wh kg-1 and a power density of 949.8 W kg-1. Even after cycling 10,000 times at 10 A g-1, the device retains 81.2% of its capacitance. This work sheds new light on manganese dioxide-based asymmetric supercapacitors and represents a significant contribution for future research on them.

MBene with Redox-Active Terminal Groups for an Energy-Dense Cascade Aqueous Battery

Two-dimensional (2D) transition metal borides (MBenes), new members of the 2D materials family, hold great promise for use in the electrocatalytic and energy storage fields because of their high specific area, high chemical activity, and fast charge carrier mobility. Although various types of MBenes are reported, layered MBenes featuring redox-active terminal groups for high energy output are not yet produced. A facile and energy-efficient method for synthesizing MBenes equipped with redox-active terminal groups for cascade Zn||I2 batteries is presented. Layered MBenes have ordered metal vacancies and ─Br terminal groups, enabling the sequential reactions of I-/I0 and Br-/Br0. The I2-hosting MBene-Br cathode results in a specific energy as high as 485.8 Wh kg-1 at 899.7 W kg-1 and a specific power as high as 6007.7 W kg-1 at 180.2 Wh kg-1, far exceeding the best records for Zn||I2 batteries. The results of this study demonstrate that the challenges of MBene synthesis can be overcome and reveal an efficient path for producing high-performance redox-active electrode materials for energy-dense cascade aqueous batteries.

Facilitating the Electrochemical Oxidation of ZnS through Iodide Catalysis for Aqueous Zinc-Sulfur Batteries

Aqueous zinc-sulfur (Zn-S) batteries show great potential for unlocking high energy and safety aqueous batteries. Yet, the sluggish kinetic and poor redox reversibility of the sulfur conversion reaction in aqueous solution challenge the development of Zn-S batteries. Here, we fabricate a high-performance Zn-S battery using highly water-soluble ZnI2 as an effective catalyst. In situ experimental characterizations and theoretical calculations reveal that the strong interaction between I- and the ZnS nanoparticles (discharge product) leads to the atomic rearrangement of ZnS, weakening the Zn-S bonding, and thus facilitating the electrochemical oxidation reaction of ZnS to S. The aqueous Zn-S battery exhibited a high energy density of 742 Wh kg(sulfur) -1 at the power density of 210.8 W kg(sulfur) -1 and good cycling stability over 550 cycles. Our findings provide new insights about the iodide catalytic effect for cathode conversion reaction in Zn-S batteries, which is conducive to promoting the future development of high-performance aqueous batteries.

Percolating Network of Anionic Vacancies in Prussian Blue: Origin of Superior Ammonium-Ion Storage Performance

Emerging aqueous ammonium-ion batteries (AIBs) are considered inexpensive, highly safe, ecofriendly, and sustainable energy storage systems. Although some high-performance electrode materials have been reported for AIBs, a comprehensive understanding of the origin of the high ammonium-ion storage performance is still lacking. Herein, the percolating network of anionic vacancies is determined to be the origin of the superior ammonium-ion storage properties of the Prussian blue analogues based on ab initio molecular dynamics simulation and electrochemical kinetic analyses. Fe[Fe(CN)6] with a percolating anionic vacancy network delivers an outstanding rate of 64.7 mAh g-1 at 2000 mA g-1 in addition to a capacity retention of 94.5% after 10 000 cycles. The low-strain intercalation ammonium-ion storage mechanism of highly deficient Fe Prussian blue with Fe as the redox center is revealed by in situ X-ray diffraction and ex situ X-ray absorption fine structure analysis. The results provide insights into the mechanism of ammonium-ion storage in Prussian blue analogues and guidance in the development of aqueous AIBs.

Comprehensive Understandings of Hydrogen Bond Chemistry in Aqueous Batteries

Aqueous batteries are emerging as highly promising contenders for large-scale grid energy storage because of uncomplicated assembly, exceptional safety, and cost-effectiveness. The unique aqueous electrolyte with a rich hydrogen bond (HB) environment inevitably has a significant impact on the electrode materials and electrochemical processes. While numerous reviews have focused on the materials design and assembly of aqueous batteries, the utilization of HB chemistry is overlooked. Herein, instead of merely compiling recent advancements, this review presents a comprehensive summary and analysis of the profound implication exerted by HB on all components of the aqueous batteries. Intricate links between the novel HB chemistry and various aqueous batteries are ingeniously constructed within the critical aspects, such as self-discharge, structural stability of electrode materials, pulverization, solvation structures, charge carrier diffusion, corrosion reactions, pH sensitivity, water splitting, polysulfides shuttle, and H2 S evolution. By adopting a vantage point that encompasses material design, binder and separator functionalization, electrolyte regulation, and HB optimization, a critical examination of the key factors that impede electrochemical performance in diverse aqueous batteries is conducted. Finally, insights are rendered properly based on HB chemistry, with the aim of propelling the advancement of state-of-the-art aqueous batteries.

Oxygen Vacancy-Enriched Bi2SeO5 Nanosheets with Dual Mechanism for Ammonium-Ion Batteries

Ammonium ions feature a light molar mass and small hydrated radius, and the interesting interaction between NH4+ and host materials has attracted widespread attention in aqueous energy storage, while few studies focus on high-performance NH4+ storage anodes. Herein, we present a high-performance inset-type anode for aqueous ammonium-ion batteries (AIBs) based on Bi2SeO5 nanosheets. A reversible NH4+/H+ co-intercalation/deintercalation accompanied by hydrogen bond formation/breaking and a conversion reaction mechanism in layered Bi2SeO5 is proposed according to ex situ characterizations. Accordingly, the optimized Bi2SeO5 anode has a high reversible capacity of 341.03 mAh g-1 at 0.3 A g-1 in 1 M NH4Cl electrolyte and an impressive capacity retention of 86.7% after 7000 cycles at 3 A g-1, which is related to the existence of oxygen vacancies that enhance ion/electron transfer and promote the formation of hydrogen bonds between NH4+ and the host material. When the rocking-chair ammonium-ion battery is assembled using a MnO2 cathode, the device delivers an ultrahigh capacity of 140.73 mAh g-1 at 0.15 A g-1 and energy density of 207.13 Wh kg-1 at the power density of 2985.07 W kg-1. This work provides a promising strategy for designing high-performance anodes for next-generation AIBs.

Robust Interfacial Effect in Multi-interface Environment through Hybrid Reconstruction Chemistry for Enhanced Energy Storage

Electrochemical-oxidation-driven reconstruction has emerged as an efficient approach for developing advanced materials, but the reconstructed microstructure still faces challenges including inferior conductivity, unsatisfying intrinsic activity, and active-species dissolution. Herein, we present hybrid reconstruction chemistry that synergistically couples electrochemical oxidation with electrochemical polymerization (EOEP) to overcome these constraints. During the EOEP process, the metal hydroxides undergo rapid reconstruction and dynamically couple with polypyrrole (PPy), resulting in an interface-enriched microenvironment. We observe that the interaction between PPy and the reconstructed metal center (i.e., Mn > Ni, Co) is strongly correlated. Theoretical calculation results demonstrate that the strong interaction between Mn sites and PPy breaks the intrinsic limitation of MnO2, rendering MnO2 with a metallic property for fast charge transfer and enhancing the ion-adsorption dynamics. Operando Raman measurement confirms the promise of EOEP-treated Mn(OH)2 (E-MO/PPy) to stably work under a 1.2 V potential window. The tailored E-MO/PPy exhibits a high capacitance of 296 F g-1 at a large current density of 100 A g-1. Our strategy presents breakthroughs in upgrading the electrochemical reconstruction technique, which enables both activity and kinetics engineering of electrode materials for better performance in energy-related fields.

Pre-intercalation of Ammonium Ions in Layered δ-MnO2 Nanosheets for High-Performance Aqueous Zinc-Ion Batteries

Layered manganese dioxide is a promising cathode candidate for aqueous Zn-ion batteries. However, the narrow interlayer spacing, inferior intrinsic electronic conductivity and poor structural stability still limit its practical application. Herein, we report a two-step strategy to incorporate ammonium ions into manganese dioxide (named as AMO) nanosheets as a cathode for boosted Zn ion storage. K+ -intercalated δ-MnO2 nanosheets (KMO) grown on carbon cloth are chosen as the self-involved precursor. Of note, ammonium ions could replace K+ ions via a facile hydrothermal reaction to enlarge the lattice space and form hydrogen-bond networks. Compared with KMO, the structural stability and the ion transfer kinetics of the layered AMO are enhanced. As expected, the obtained AMO cathode exhibits remarkable electrochemical properties in terms of high reversible capacity, decent rate performance and superior cycling stability over 10000 cycles.

Regulating Zinc Storage Behaviors of Tunnel Structure Cathodes Via Tungsten Induction

Aqueous zinc-ion batteries have received continuous interests because of applying low-cost and eco-friendly aqueous electrolytes and having high safety. Beyond energetically to explore new-type cathode materials, it is of great significance to regulate the zinc storage behavior of the existing cathodes in order to understand the underlying working mechanism. Therefore, as a proof of concept, this work achieves the regulation of zinc storage behaviors of the tunnel structure tunnel structure B-phase vanadium dioxide (VO2 (B)) and vanadium oxide (V6 O13 ) cathodes via a simple chemical tungsten-doping induction approach. Under low-concentration tungsten-doping induction of 1, 2 and 3 at.%, the tunnel sizes of VO2 (B) can be controlled readily. Moreover, the V6 O13 with large size tunnels can be achieved by medium-concentration tungsten induction of 6 and 9 at.%. It is demonstrated that tungsten induced VO2 (B) can achieve zinc storage without lattice structure change via operando X-ray diffraction analyses. Remarkably, via operando and non-operando analyses, tungsten induced V6 O13 with lager size tunnels can realize the oriented 1D zinc ion intercalation/deintercalation. The further kinetics analysis shows that the zinc storage is mainly diffusion control, which is different from most of vanadium-based cathodes with capacitance control. This viable tungsten-doping induction strategy provides a new insight into achieving the controllable regulation of zinc storage behaviors.

Triple-function Hydrated Eutectic Electrolyte for Enhanced Aqueous Zinc Batteries

Aqueous rechargeable zinc-ion batteries (ARZBs) are impeded by the mutual problems of unstable cathode, electrolyte parasitic reactions, and dendritic growth of zinc (Zn) anode. Herein, a triple-functional strategy by introducing the tetramethylene sulfone (TMS) to form a hydrated eutectic electrolyte is reported to ameliorate these issues. The activity of H2 O is inhibited by reconstructing hydrogen bonds due to the strong interaction between TMS and H2 O. Meanwhile, the preferentially adsorbed TMS on the Zn surface increases the thickness of double electric layer (EDL) structure, which provides a shielding buffer layer to suppress dendrite growth. Interestingly, TMS modulates the primary solvation shell of Zn2+ ultimately to achieve a novel solvent co-intercalation ((Zn-TMS)2+ ) mechanism, and the intercalated TMS works as a "pillar" that provides more zincophilic sites and stabilizes the structure of cathode (NH4 V4 O10 , (NVO)). Consequently, the Zn||NVO battery exhibits a remarkably high specific capacity of 515.6 mAh g-1 at a low current density of 0.2 A g-1 for over 40 days. This multi-functional electrolytes and solvent co-intercalation mechanism will significantly propel the practical development of aqueous batteries.

2D Conjugated Metal-Organic Frameworks Embedded with Iodine for High-Performance Ammonium-Ion Hybrid Supercapacitors

Ammonium ions (NH4 + ) are emerging non-metallic charge carriers for advanced electrochemical energy storage devices, due to their low cost, elemental abundance, and environmental benignity. However, finding suitable electrode materials to achieve rapid diffusion kinetics for NH4 + storage remains a great challenge. Herein, a 2D conjugated metal-organic framework (2D c-MOF) for immobilizing iodine, as a high-performance cathode material for NH4 + hybrid supercapacitors, is reported. Cu-HHB (HHB = hexahydroxybenzene) MOF embedded with iodine (Cu-HHB/I2 ) features excellent electrical conductivity, highly porous structure, and rich accessible active sites of copper-bis(dihydroxy) (Cu─O4 ) and iodide species, resulting in a remarkable areal capacitance of 111.7 mF cm-2 at 0.4 mA cm-2 . Experimental results and theoretical calculations indicate that the Cu─O4 species in Cu-HHB play a critical role in binding polyiodide and suppressing its dissolution, as well as contributing to a large pseudocapacitance with adsorbed iodide. In combination with a porous MXene anode, the full NH4 + hybrid supercapacitors deliver an excellent energy density of 31.5 mWh cm-2 and long-term cycling stability with 89.5% capacitance retention after 10 000 cycles, superior to those of the state-of-the-art NH4 + hybrid supercapacitors. This study sheds light on the material design for NH4 + storage, enabling the development of novel high-performance energy storage devices.

MoS2 @Polyaniline for Aqueous Ammonium-Ion Supercapacitors

Ammonium-ion aqueous supercapacitors are raising notable attention owing to their cost, safety, and environmental advantages, but the development of optimized electrode materials for ammonium-ion storage still lacks behind expectations. To overcome current challenges, here, a sulfide-based composite electrode based on MoS2 and polyaniline (MoS2 @PANI) is proposed as an ammonium-ion host. The optimized composite possesses specific capacitances above 450 F g-1 at 1 A g-1 , and 86.3% capacitance retention after 5000 cycles in a three-electrode configuration. PANI not only contributes to the electrochemical performance but also plays a key role in defining the final MoS2 architecture. Symmetric supercapacitors assembled with such electrodes display energy densities above 60 Wh kg-1 at a power density of 725 W kg-1 . Compared with Li+ and K+ ions, the surface capacitive contribution in NH4 + -based devices is lower at every scan rate, which points to an effective generation/breaking of H-bonds as the mechanism controlling the rate of NH4 + insertion/de-insertion. This result is supported by density functional theory calculations, which also show that sulfur vacancies effectively enhance the NH4 + adsorption energy and improve the electrical conductivity of the whole composite. Overall, this work demonstrates the great potential of composite engineering in optimizing the performance of ammonium-ion insertion electrodes.

Charge-Assisted Hydrogen-Bonded Organic Frameworks with Inorganic Ammonium Regulated Switchable Open Polar Sites

Surface open polar sites within the voids of porous molecular crystals define the localized physicochemical environment for critical functions such as gas separation and molecular recognition. This study presents a new charge-assisted hydrogen bonding (H-bonding) motif, by exploiting inorganic ammonium (NH₄ ⁺ ) cations as H-bond donors, to regulate the assembly of C₂ -symmetric carboxylic tectons for building robust H-bonded frameworks with permanent ultra-micropores and open oxygen sites. Diverse building blocks are bridged by tetrahedral NH₄ ⁺ to expand distinctive H-bonded networks with varied pore architectures. Particularly, the open polar oxygen sites can be switched by altering NH₄ ⁺ sources to tune the deprotonation of carboxyl-containing tectons. The activated porous PTBA·NH₄ ·DMF preserves the pore architecture and open polar oxygen sites, exhibiting remarkably selective sorption of CO₂ (107.8 cm³ g^-1 ,195 K) over N₂ (11.2 cm³ g^-1 , 77 K) and H₂ (1.4 cm³ g^-1 , 77 K).

The Emerging Layered Hydroxide Plates with Record Thickness for Enhanced High-Mass-Loading Energy Storage

The past decade has witnessed the development of layered-hydroxide-based self-supporting electrodes, but the low active mass ratio impedes its all-around energy-storage applications. Herein, the intrinsic limit of layered hydroxides is broken by engineering F-substituted β-Ni(OH)₂ (Ni-F-OH) plates with a sub-micrometer thickness (over 700 nm), producing a superhigh mass loading of 29.8 mg cm^-2 on the carbon substrate. Theoretical calculation and X-ray absorption spectroscopy analysis demonstrate that Ni-F-OH shares the β-Ni(OH)₂ -like structure with slightly tuned lattice parameters. More interestingly, the synergy modulation of NH₄ ⁺ and F^- is found to serve as the key enabler to tailor these sub-micrometer-thickness 2D plates thanks to the modification effects on the (001) plane surface energy and local OH^- concentration. Guided by this mechanism, the superstructures of bimetallic hydroxides and their derivatives are further developed, revealing they are a versatile family with great promise. The tailored ultrathick phosphide superstructure achieves a superhigh specific capacity of 7144 mC cm^-2 and a superior rate capability (79% at 50 mA cm^-2 ). This work highlights a multiscale understanding of how exceptional structure modulation happens in low-dimensional layered materials. The as-built unique methodology and mechanisms will boost the development of advanced materials to better meet future energy demands.

Valence Engineering Enhancing NH4 + Storage Capacity of Manganese Oxides

Ammonium ions (NH₄ ⁺ ), as non-metallic charge carriers, are attracting attention in aqueous batteries due to its low molar mass, element sufficiency, and non-toxicity. However, the host materials for NH₄ ⁺ storage are still limited. Herein, an oxygen defects-rich manganese oxide (MnO_2-x ) for NH₄ ⁺ storage are reported. The oxygen defects can endow the MnO_2-x sample with improved electric conductivity and low interface activation energy. The electrochemical reaction mechanism is also verified by using ex situ X-ray photoelectron spectroscopy (XPS) and fourier transform infrared spectroscopy (FT-IR), demonstrating the insertion and extraction of NH₄ ⁺ in the MnO_2-x by formation/breaking of a hydrogen bond. As a result, MnO_2-x delivers a high capacity of 109.9 mAh g^-1 at the current density of 0.5 A g^-1 and retention of 24 mAh g^-1 after 1000 cycles at the current density of 4 A g^-1 , outperforming the pristine MnO₂ sample.

Vanadium Oxides with Amorphous-Crystalline Heterointerface Network for Aqueous Zinc-Ion Batteries

Rechargeable aqueous Zn-VO_x batteries are attracting attention in large scale energy storage applications. Yet, the sluggish Zn²⁺ diffusion kinetics and ambiguous structure-property relationship are always challenging to fulfil the great potential of the batteries. Here we electrodeposit vanadium oxide nanobelts (VO-E) with highly disordered structure. The electrode achieves high capacities (e.g., ≈5 mAh cm^-2 , 516 mAh g^-1 ), good rate and cycling performances. Detailed structure analysis indicates VO-E is composed of integrated amorphous-crystalline nanoscale domains, forming an efficient heterointerface network in the bulk electrode, which accounts for the good electrochemical properties. Theoretical calculations indicate that the amorphous-crystalline heterostructure exhibits the favorable cation adsorption and lower ion diffusion energy barriers compared to the amorphous and crystalline counterparts, thus accelerating charge carrier mobility and electrochemical activity of the electrode.

Flexible Ammonium-Ion Pouch Cells Based on a Tunneled Manganese Dioxide Cathode

Aqueous ammonium-ion (NH₄⁺) batteries are becoming the competitive energy storage candidate on account of their safety, affordability, sustainability, and intrinsically peculiar properties. Herein, an aqueous NH₄⁺-ion pouch cell is investigated based on a tunneled manganese dioxide (α-MnO₂) cathode and a 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) anode. The MnO₂ electrode possesses a high specific capacity of ∼190 mA h g^-1 at 0.1 A g^-1 and displays excellent long cycling performance after 50,000 cycles in 1 M (NH₄)₂SO₄, which outperforms the most reported ammonium-ion host materials. Besides, a solid-solution behavior is revealed about the migration of NH₄⁺ in the tunnel-like α-MnO₂. The battery displays a splendid rate capacity of 83.2 mA h g^-1 even at 10 A g^-1. It also exhibits a high energy density of ∼78 W h kg^-1 as well as a high power density of ∼8212 W kg^-1 (based on the mass of MnO₂). What is more, the flexible MnO₂//PTCDA pouch cell based on the hydrogel electrolyte shows excellent flexibility and good electrochemical properties. The topochemistry results of MnO₂//PTCDA point to the potential practicability of ammonium-ion energy storage.

Free-standing vanadium oxide hydration/reduced graphene oxide film for ammonium ion supercapacitors

Aqueous ammonium-ion energy storage systems have recently gained continuous attention owing to the advantages of sustainability and environmental-friendliness in the grid-scale application. However, ammonium-ion supercapacitors are still in their infancy, and it is of great challenge in developing suitable materials for application in wearable energy storage devices. Herein, we develop a vanadium oxide hydration (V₂O₅·nH₂O)/reduced graphene oxide (rGO) composite film (denoted as VGF) as a free-standing paper-like electrode for ammonium-ion storage, where V₂O₅·nH₂O shows an expanded interlayer spacing and is sandwiched by rGO through chemical bonds. As a result, the designed VGF exhibits a capacitance of 600F·g^-1 at 0.2 A·g^-1 and good cyclability of over 10,000 cycles with a retention of 93 % using PVA/NH₄Cl gel electrolyte. Meanwhile, the ammonium-ion storage mechanism in VGF electrode is further verified to be dominated by the intercalation pseudocapacitance and electric double-layer capacitance. Furthermore, the quasi-solid-state symmetric supercapacitor (SSC) has been also assembled to assess the feasibility of practical applications in wearable devices. As expected, the SSC possesses an areal capacitance of 241 mF·cm^-2 at 0.1 mA·cm^-2 (0.82 Wh·m^-2 at 0.09 W·m^-2) and an excellent cyclability of 20,000 cycles with a retention of 92 %, which is comparable to that achieved in the vanadium oxides powder-made electrodes and the SSC made of. Together with the excellent flexibility and feasibility of parallel/series combination, the VGF SSC devices shows great possibility for the applications in wearable devices, which further proves the great potential of this designed VGF free-standing electrode for ammonium-ion storage.

Quantitative Regulation of Interlayer Space of NH4 V4 O10 for Fast and Durable Zn2+ and NH4 + Storage

Layered vanadium-based oxides are the promising cathode materials for aqueous zinc-ion batteries (AZIBs). Herein, an in situ electrochemical strategy that can effectively regulate the interlayer distance of layered NH₄ V₄ O₁₀ quantitatively is proposed and a close relationship between the optimal performances with interlayer space is revealed. Specifically, via increasing the cutoff voltage from 1.4, 1.6 to 1.8 V, the interlayer space of NH₄ V₄ O₁₀ can be well-controlled and enlarged to 10.21, 11.86, and 12.08 Å, respectively, much larger than the pristine one (9.5 Å). Among them, the cathode being charging to 1.6 V (NH₄ V₄ O₁₀ -C1.6), demonstrates the best Zn²⁺ storage performances including high capacity of 223 mA h g^-1 at 10 A g^-1 and long-term stability with capacity retention of 97.5% over 1000 cycles. Such superior performances can be attributed to a good balance among active redox sites, charge transfer kinetics, and crystal structure stability, enabled by careful control of the interlayer space. Moreover, NH₄ V₄ O₁₀ -C1.6 delivers NH₄ ⁺ storage performances whose capacity reaches 296 mA h g^-1 at 0.1 A g^-1 and lifespan lasts over 3000 cycles at 5 A g^-1 . This study provides new insights into understand the limitation of interlayer space for ion storage in aqueous media and guides exploration of high-performance cathode materials.

Screening of electrode materials for ammonium ion batteries by high throughput calculation

Ammonium-ion batteries (AIBs) have attracted intense interest lately as promising energy storage systems due to their light weight, safe, inexpensive, and widely available advantages. It is of great significance to find a fast ammonium ion conductor for the electrode of AIBs that directly affects the electrochemical performance of the battery. Using high-throughput bond-valence calculation, we screened the electrode materials of AIBs with a low diffusion barrier from more than 8000 compounds in the ICSD database. Twenty-seven candidate materials were finally identified by the bond-valence sum method and density functional theory. Their electrochemical properties were further analyzed. Our results, which give the relationship between the structure and electrochemical properties of various important electrode materials which are suitable for AIBs development, may pave the way for next-generation energy storage systems.

Electrodepositing amorphous molybdenum oxides for aqueous NH4+ storage

The limited choice of anode materials always challenges the development of high performance aqueous ammonium-ion batteries (AAIBs). Herein, we fabricate amorphous molybdenum oxide (MoO_x) materials and study the NH₄⁺ storage performances. The results indicate that the optimized electrode exhibits high gravimetric/areal capacities of 175 mA h g^-1/1.30 mA h cm^-2, outperforming state-of-the-art anode materials for AAIBs. Our findings indicate that the valence state of Mo and the Mo-O-H content in MoO_x synergistically control the NH₄⁺ storage performances, offering new understanding for rational design of MoO_x materials for energy storage applications.

A Sustainable NH4 + Ion Battery by Electrolyte Engineering

Aqueous ammonium ion battery is a promising sustainable energy storage system. However, the side reactions originating from electrolytes (the water decomposition and host material dissolution) preclude its practical applications. Unlike the metal-based aqueous batteries, the idea of "ultrahigh concentrated electrolyte" is not feasible due to the strong hydrolysis of ammonium ions. Therefore, we propose an effective and sustainable strategy for the water hydrogen bond network modulation by adding sucrose into the electrolytes. The sucrose can form sucrose-water hydrogen bond networks to break the continuous water hydrogen bond network, thereby inhibiting water decomposition significantly. Moreover, the weak hydrogen bond interaction between ammonium and sucrose facilitates rapid ion migration, leading to an improved ionic conductivity. This work presents a new electrolyte modulating strategy for the practical application of aqueous ammonium ion batteries.

A 2.75 V ammonium-based dual-ion battery

The popular metal-ion batteries (MIBs) suffer from environmental and economic issues because of their heavy dependency on nonrenewable metals. Here, we propose a metal-free ammonium (NH₄ ⁺ )-based dual-ion battery with a record-breaking operation voltage of 2.75 V. The working mechanism of this sustainable battery involves the reversible anion (PF₆ ^- ) intercalation chemistry in graphite cathode and NH₄ ⁺ intercalation behavior in PTCDI (3,4,9,10-perylenetetracarboxylic diimide) anode. This new battery configuration successfully circumvented the reduction susceptibility of NH₄ ⁺ and the lack of mature NH₄ ⁺ -rich cathodes for NH₄ ⁺ ion batteries (AIBs). The customized organic NH₄ ⁺ electrolyte endows the graphite||PTCDI full battery with durable longevity (over 1000 cycles) and a high energy density (200 Wh kg^-1 ). We show that the development of AIBs should be high-voltage-oriented while circumventing low operation potential to avoid NH₄ ⁺ reduction.

Engineering NiCo2S4 nanoparticles anchored on carbon nanotubes as superior energy-storage materials for supercapacitors

Fabricating high-capacity electrode materials toward supercapacitors has attracted increasing attention. Here we report a three-dimensional CNTs/NiCo2S4 nanocomposite material synthesized successfully by a facile one-step hydrothermal technique. As expected, a CNTs/NiCo2S4 electrode shows remarkable capacitive properties with a high specific capacitance of 890 C g-1 at 1 A g-1. It also demonstrates excellent cycle stability with an 83.5% capacitance retention rate after 5000 cycles at 10 A g-1. Importantly, when assembled into a asymmetric supercapacitor, it exhibits a high energy density (43.3 W h kg-1) and power density (800 W kg-1). The exceptional electrochemical capacity is attributed to the structural features, refined grains, and enhanced conductivity. The above results indicate that CNTs/NiCo2S4 composite electrode materials have great potential application in energy-storage devices.

A Honeycomb-like Ammonium-Ion Fiber Battery with High and Stable Performance for Wearable Energy Storage

Aqueous ammonium-ion batteries have attracted intense interest lately as promising energy storage systems due to the price advantage and fast charge/discharge capability of ammonium-ion redox reactions. However, the research on the strength and energy storage characteristics of ammonium-ion fiber batteries is still limited. In this study, an ammonium-ion fiber battery with excellent mechanical strength, flexibility, high specific capacity, and long cycle-life has been developed with a robust honeycomb-like ammonium vanadate@carbon nanotube (NH₄V₄O₁₀@CNT) cathode. The fiber electrode delivers a steady specific capacity of 241.06 mAh cm^-3 at a current of 0.2 mA. Moreover, a fiber full cell consisting of an NH₄V₄O₁₀@CNT cathode and a PANI@CNT anode exhibits a specific capacity of 7.27 mAh cm^-3 at a current of 0.3 mA and retains a high capacity retention of 72.1% after 1000 cycles. Meanwhile, it shows good flexibility and superior electrochemical performance after 500 times bending or at different deformation states. This work offers a reference for long-cycle, flexible fibrous ammonium-ion batteries.

Recent Progress in Aqueous Ammonium-Ion Batteries

Batteries using a water-based electrolyte have the potential to be safer, more durable, less prone to thermal runaways, and less costly than current lithium batteries using an organic solvent. Among the possible aqueous battery options, ammonium-ion batteries (AIBs) are very appealing because the base materials are light, safe, inexpensive, and widely available. This review gives a concise and useful survey of recent progress on emerging AIBs, starting with a brief overview of AIBs, followed by cathode materials, anode materials, electrolytes, and various devices based on ammonium-ion storage. Aside from summarizing the most updated electrodes/electrolytes in AIBs, this review highlights fundamental mechanistic studies in AIBs and state-of-the art applications of ammonium-ion storage. The present work reviews various theoretical efforts and the spectrum studies that have been used to explore ionic transport kinetics, electrolyte structure, solvation behavior of ammonium ions, and the intercalation mechanism in the host structure. Furthermore, diverse applications of ammonium-ion storage apart from aqueous AIBs are discussed, including flexible AIBs, AIBs that can operate across a wide temperature range, ammonium-ion supercapacitors, and battery-supercapacitor hybrid devices. Finally, the review is concluded with perspectives of AIBs, challenges remaining in the field, and possible research directions to address these challenges to boost the performance of AIBs for real-world practical applications.

Arrayed Heterostructures of MoS2 Nanosheets Anchored TiN Nanowires as Efficient Pseudocapacitive Anodes for Fiber-Shaped Ammonium-Ion Asymmetric Supercapacitors

Nonmetallic ammonium ions that feature high safety, low molar mass, and small hydrated radius properties have shown great advantages in wearable aqueous supercapacitors. The construction of high-energy-density flexible ammonium-ion asymmetric supercapacitors (AASCs) is promising but still challenging due to the lack of high-capacitance pseudocapacitive anodes. Herein, freestanding core-shell heterostructures supported on carbon nanotube fibers were designed by anchoring MoS₂ nanosheets on nanowires (MoS₂@TiN/CNTF) as anodes for AASCs. With contributions of abundant active sites and conspicuous synergistic effects of multiple components for arrayed heterostructure engineering, the developed MoS₂@TiN/CNTF anodes exhibit a specific capacitance of 1102.5 mF cm^-2 at 2 mA cm^-2. Theoretical calculations confirm the dramatic enhancement of the binding strength of ammonium ions on the MoS₂ shell layer at the heterostructure, where a built-in electric field exists to accelerate the charge transfer. By utilizing a MnO₂/CNTF cathode and NH₄Cl/poly(vinyl alcohol) (PVA) as a gel electrolyte, quasi-solid-state fiber-shaped AASCs were successfully constructed, achieving a specific capacitance of 351.2 mF cm^-2 and an energy density of 195.1 μWh cm^-2, outperforming most recently reported fiber-shaped supercapacitors. This work provides a promising strategy to rationally design heterostructure engineering of MoS₂@TiN nanoarrays toward advanced anodes for application in next-generation AASCs.

Methods for Rational Design of Advanced Zn-Based Batteries

Rechargeable aqueous zinc-based batteries (AZBs) have received massive attention as promising contenders for the future large-scale energy storage due to their low cost, inherent safety, and abundant resources. However, the insufficient energy density and poor stability have become the key to hinder their further application. As is well known, the energy densities (E, Wh kg^-1 ) of AZBs are determined by the specific capacity (mAh g^-1 ) and output voltage (V). Given the fixed redox potential and capacity of the Zn metal anode, the energy density of AZBs is mainly determined by the cathode material, and the rich material systems of the cathode provide more possibilities to this field. Meanwhile, the methods to improve the stability and performance of the Zn anodes have gained more and more attention due to the severe Zn dendrite growth that can pierce the separator and lead to short-circuiting of the cell. Therefore, in this review, we comprehensively summarize the rational design methods in optimizing the cathode, anode, and device architecture, and classic examples of each catalogue are discussed in details as well. Last, the issues and outlook for further development of high performance AZBs are also presented.

Recent Advances of Carbon Materials in Anodes for Aqueous Zinc Ion Batteries

Carbon-based materials have been successfully applied in the zinc ion batteries to improve the energy storage capability and durability of zinc anodes. In this review, four types of carbon materials (conventional carbons, fiber-like carbons, carbon nanotubes, graphene and other 2D carbon materials) are introduced based on the electrode preparation, physicochemical property and battery performance. Several modification strategies are also illustrated, such as heteroatom doping, hierarchical design and metal/carbon composites. Besides the discussion of existing issues of zinc anodes, the structure-performance relationships are analyzed in depth. Finally, conclusive remarks of this review are summarized and prospects of the future improvement are proposed.