Hydrogen Bond-Assisted Ultra-Stable and Fast Aqueous NH4+ Storage

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.

Berlin Green with tunable iron content as ultra-high rate host for efficient aqueous ammonium ion storage

Prussian blue analogues (PBAs) are regarded as promising cathode materials for ammonium-ion batteries (AIBs) because of their low cost and superb theoretical capacity. However, its inherently poor conductivity and structural collapse can significantly limit the enhancement of rate property and cycling stability. In this work, Berlin Green (BG) electrode materials with similar wool-like clusters were constructed by direct precipitation method to accelerate the kinetic, which realizes outstanding cycling stability. Berlin Green with the appropriate amount of iron (BG-2) has a fast ion transport channel, enhanced structure stability, highly reversible insertion/extraction of NH4+, and fine electrochemical reaction activity. Benefiting from the unique architecture and component, the BG-2 electrode shows an excellent rate performance with a discharge/charge specific capacity of 60.1/59.3 mAh g-1 at 5 A g-1. Even at 5 A g-1, BG-2 exhibits remarkable cycling stability with an initial discharge capacity of 59.5 mAh g-1 and a capacity retention rate of approximately 76% after 30,000 cycles. The BG-2 reveals exceedingly good electrochemical reversibility during the process of NH4+ (de)insertion. BG materials indicate huge potential as a cathode material for the next generation of high-performance aqueous batteries.

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.

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.

Optimizing Mn in Prussian blue analogs with double redox active sites to induce boosted Zn2+ storage

Prussian Blue analogs (PBAs) are a suitable aqueous zinc-ion batteries (AZIBs) cathode material, but they face issues related to low specific capacity and cycling lifespan due to insufficient active sites and poor ion de-intercalation structural stability. In this study, Mn-Prussian Blue Analog (Mn-PBA) is fabricated using a simple co-precipitation method and the morphology of Mn-PBA is further optimized through artificially manipulating concentration gradients strategy, effectively enhancing the structural stability of Zn2+ de-intercalation. Furthermore, the introduction of Mn established dual Zn2+ active centers in Mn-PBA (Mn-O and Fe(CN)6]4-/[Fe(CN)6]3-), leading to an increased specific capacity. As a proof of concept for AZIBs, the optimized Mn-PBA-3 cathode exhibits a high reversible specific capacity of 143.5 mAh/g and maintains a capacity retention of 88.5 % after 250 cycles at 1 A/g, surpassing commercial MnO2 (30.5 mAh/g after 100 cycles). Mn-PBA-3 also delivers a high capacity of 79.0 mA h g-1 after 2000 cycles of 10 A/g. The mechanism of the Zn2+ double redox reaction of Mn-PBA-3 has been revealed in detail by in situ Raman and a series of ex situ techniques. Under a high operating voltage window of 0-1.9 V, Zn//Mn-PBA-3 demonstrates a capacity of 99.3 mAh/g after 800 cycles (5 A/g) by assembling zinc ion button battery. This work has reference significance for structurally modulated PBAs used in high performance AZIBs.

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.

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.

Metal-Free Eutectic Electrolyte with Weak Hydrogen Bonds for High-Rate and Ultra-Stable Ammonium-Ion Batteries

As the need for sustainable battery chemistry grows, non-metallic ammonium ion (NH4 + ) batteries are receiving considerable attention because of their unique properties, such as low cost, nontoxicity, and environmental sustainability. In this study, the solvation interactions between NH4 + and solvents are elucidated and design principles for NH4 + weakly solvated electrolytes are proposed. Given that hydrogen bond interactions dominate the solvation of NH4 + and solvents, the strength of the solvent's electrostatic potential directly determines the strength of its solvating power. As a proof of concept, succinonitrile with relatively weak electronegativity is selected to construct a metal-free eutectic electrolyte (MEE). As expected, this MEE is able to significantly broaden the electrochemical stability window and reduce the solvent binding energy in the solvation shell, which leads to a lower desolvation energy barrier and a fast charge transfer process. As a result, the as-constructed NH4 -ion batteries exhibit superior reversible rate capability (energy density of 65 Wh kg-1 total active mass at 600 W kg-1 ) and unprecedent long-term cycling performance (retention of 90.2% after 1000 cycles at 1.0 A g-1 ). The proposed methodology for constructing weakly hydrogen bonded electrolytes will provide guidelines for implementing high-rate and ultra-stable NH4 + -based energy storage systems.

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.

Metal-Free Perovskites for X-Ray Detection

Metal-free perovskites are a promising class of materials for X-ray detection due to their unique structural, optical, and electrical properties. Here, we first delve into the stoichiometry and geometric argument of metal-free perovskites. Followed, the alternative A/B/X ions and hydrogen-bonding are clearly introduced to further optimize the materials' stability and properties. Finally, we provide a comprehensive overview of their potential applications for flexible X-ray images and prospects for metal-free perovskite development. In conclusion, metal-free perovskite is a promising material for X-ray detection. Its stoichiometric and geometric parameters, ion, and hydrogen bond selection, and application prospects are worthy of further study.

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.

Unlocking High-Performance Ammonium-Ion Batteries: Activation of In-Layer Channels for Enhanced Ion Storage and Migration

Ammonium-ion batteries, leveraging non-metallic ammonium ions, have arisen as a promising electrochemical energy storage system; however, their advancement has been hindered by the scarcity of high-performance ammonium-ion storage materials. In this study, an electrochemical phase transformation approach is proposed for the in situ synthesis of layered VOPO4 ·2H2 O (E-VOPO) with predominant growth on the (200) plane, corresponding to the tetragonal channels on the (001) layers. The findings reveal that these tetragonal in-layer channels not only furnish NH4 + storage sites but also enhance transfer kinetics by providing rapid cross-layer migration pathways. This crucial aspect has been largely overlooked in previous studies. The E-VOPO electrode exhibits exceptional ammonium-ion storage performance, including significantly increased specific capacity, enhanced rate capability, and robust cycling stability. The resulting full cell can be stably operated for 12 500 charge-discharge cycles at 2 A g-1 for over 70 days. The proposed approach offers a new strategy for meticulously engineering electrode materials with facilitated ion storage and migration, thereby paving the way for developing more efficient and sustainable energy storage systems.

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.

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 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.

Coupling dual metal active sites and low-solvation architecture toward high-performance aqueous ammonium-ion batteries

Aqueous rechargeable ammonium-ion batteries (AIBs) possess the characteristics of safety, low cost, environmental friendliness, and fast diffusion kinetics. However, their energy density is often limited due to the low specific capacity of cathode materials and narrow electrochemical stability windows of electrolytes. Herein, high-performance aqueous AIBs were designed by coupling Fe-substituted manganese-based Prussian blue analog (FeMnHCF) cathodes and highly concentrated NH₄CF₃SO₃ electrolytes. In FeMnHCF, Mn³⁺/Mn²⁺-N redox reaction at high potential was introduced, and two metal active redox species of Mn and Fe were achieved. To match such FeMnHCF cathodes, highly concentrated NH₄CF₃SO₃ electrolyte was further developed, where NH₄⁺ ion displays low-solvation structure because of the increased coordination number of CF₃SO₃^- anions. Furthermore, the water molecules are confined by NH₄⁺ and CF₃SO₃^- ions in their solvation sheath, leading to weak interaction between water molecules and thus effectively extending the voltage window of electrolyte. Consequently, the FeMnHCF electrodes present high reversibility during the charge/discharge process. Moreover, owing to a small amount of free water in concentrated electrolyte, the dissolution of FeMnHCF is also inhibited. As a result, the assembled aqueous AIBs exhibit enhanced energy density, excellent rate capability, and stable cycling behavior. This work provides a creative route to construct high-performance aqueous AIBs.

Unlocking the High Capacity Ammonium-Ion Storage in Defective Vanadium Dioxide

Aqueous ammonium-ion storage has been considered a promising energy storage competitor to meet the requirements of safety, affordability, and sustainability. However, ammonium-ion storage is still in its infancy in the absence of reliable electrode materials. Here, defective VO₂ (d-VO) is employed as an anode material for ammonium-ion batteries with a moderate transport pathway and high reversible capacity of ≈200 mAh g^-1 . Notably, an anisotropic or anisotropic behavior of structural change of d-VO between c-axis and ab planes depends on the state of charge (SOC). Compared with potassium-ion storage, ammonium-ion storage delivers a higher diffusion coefficient and better electrochemical performance. A full cell is further fabricated by d-VO anode and MnO₂ cathode, which delivers a high energy density of 96 Wh kg^-1 (based on the mass of VO₂ ), and a peak energy density of 3254 W kg^-1 . In addition, capacity retention of 70% can be obtained after 10 000 cycles at a current density of 1 A g^-1 . What's more, the resultant quasi-solid-state MnO₂ //d-VO full cell based on hydrogel electrolyte also delivers high safety and decent electrochemical performance. This work will broaden the potential applications of the ammonium-ion battery for sustainable energy storage.

Concentrated Electrolytes Enabling Stable Aqueous Ammonium-Ion Batteries

Rechargeable aqueous batteries are promising devices for large-scale energy-storage applications because of their low-cost, inherent safety, and environmental friendliness. Among them, aqueous ammonium-ion (NH₄ ⁺ ) batteries (AAIB) are currently emerging owing to the fast diffusion kinetics of NH₄ ⁺ . Nevertheless, it is still a challenge to obtain stable AAIB with relatively high output potential, considering the instability of many electrode materials in an aqueous environment. Herein, a cell based on a concentrated (5.8 m) aqueous (NH₄ )₂ SO₄ electrolyte, ammonium copper hexacyanoferrate (N-CuHCF) as the positive electrode (cathode), and 3,4,9,10-perylene-bis(dicarboximide) (PTCDI) as the negative electrode (anode) is reported. The solvation structure, electrochemical properties, as well as the electrode-electrolyte interface and interphase are systematically investigated by the combination of theoretical and experimental methods. The results indicate a remarkable cycling performance of the low-cost rocking-chair AAIB, which offers a capacity retention of ≈72% after 1000 cycles and an average output potential of ≈1.0 V.

Hydrogen Bond Shielding Effect for High-Performance Aqueous Zinc Ion Batteries

Manganese oxides are highly desirable for the cathode of rechargeable aqueous zinc ion batteries (AZIBs) owing to their low cost and high abundance. However, the terrible structure stability of manganese oxide limits its practical application. Here, it is demonstrated that the hydrogen-bond shielding effect can improve the electrochemical performance of manganese oxide. Briefly, (NH₄ )_0.125 MnO₂ (NHMO) is prepared by introducing NH₄ ⁺ into the tunnel structure of α-MnO₂ . The robust hydrogen bonds between N-H and host O atoms can stabilize the lattice structure of α-MnO₂ and suppress the dissolution of Mn element. More importantly, it can also accelerate ions mobility kinetics by weakening the electrostatic interaction of host O atoms. Thus, the fabricated Zn||NHMO battery possesses impressive cycling life (99.5% of capacity retention over 10 000 cycles) and rate capability (109 mA h g^-1 of discharge capacity at 6000 mA g^-1 ). Comprehensive analyses reveal the essences of interfacial charge and bulk ions transfer. This finding opens new opportunities for the development of high-performance AZIBs.

Zinc hexacyanoferrate with a highly reversible open framework for fast aqueous nickel-ion storage

K2Zn3[Fe(CN)6]2 with a highly reversible open framework displays excellent cycle and rate performance for Ni ion storage in aqueous rechargeable batteries.

Nickel Ferrocyanides for Aqueous Ammonium Ion Batteries

In this report, we design a structural optimization in Ni2Fe(CN)6 through a partial substitution of nickel by sodium, and investigate the electrochemical performance of a series of Na2xNi2-xFe(CN)6 (x =...

The emerging aqueous ammonium-ion batteries

Aqueous ammonium‐ion (NH₄⁺) batteries (AAIB) are a recently emerging technology that utilize the abundant electrode resources and the fast diffusion kinetics of NH₄⁺ to deliver an excellent rate performance at a low cost. Although significant progress has been made on AAIBs, the technology is still limited by various challenges. In this Minireview, the most recent advances are comprehensively summarized and discussed, including cathode and anode materials as well as the electrolytes. Finally, a perspective on possible solutions for the current limitations of AAIBs is provided.

Copper niobate nanowires boosted by a N, S co-doped carbon coating for superior lithium storage

With the development of electric vehicles, more and more attention has been paid to the kinetic performance of batteries, which is related to rapid charge/discharge and safety issues. To improve this aspect, Cu₂Nb₃₄O₈₇ nanowires covered by nitrogen and sulfur co-doped carbon (Cu₂Nb₃₄O₈₇/NSC nanowires) are prepared by electrospinning combined with surface coating. As-prepared Cu₂Nb₃₄O₈₇/NSC nanowires present a high ion diffusion coefficient and electronic conductivity, showing good a kinetic performance. Specifically, they deliver a splendid capacity of 311.2 mA h g^-1 at 1 C and a superior cycling stability with a capacity fading of 0.031% per cycle upon 1000 cycles. At the same time, the electrochemical and structural reversibility is fully discussed and demonstrated by ex situ XRD, ex situ SEM and ex situ XPS based on the redox couples of Cu²⁺/Cu⁺, Nb⁵⁺/Nb⁴⁺, and Nb⁴⁺/Nb³⁺. Contributing to peculiar physico-chemical properties, Cu₂Nb₃₄O₈₇/NSC nanowires are expected to be a candidate material for the anode in lithium-ion batteries.

Prussian Blue Analogues in Aqueous Batteries and Desalination Batteries

In the applications of large-scale energy storage, aqueous batteries are considered as rivals for organic batteries due to their environmentally friendly and low-cost nature. However, carrier ions always exhibit huge hydrated radius in aqueous electrolyte, which brings difficulty to find suitable host materials that can achieve highly reversible insertion and extraction of cations. Owing to open three-dimensional rigid framework and facile synthesis, Prussian blue analogues (PBAs) receive the most extensive attention among various host candidates in aqueous system. Herein, a comprehensive review on recent progresses of PBAs in aqueous batteries is presented. Based on the application in different aqueous systems, the relationship between electrochemical behaviors (redox potential, capacity, cycling stability and rate performance) and structural characteristics (preparation method, structure type, particle size, morphology, crystallinity, defect, metal atom in high-spin state and chemical composition) is analyzed and summarized thoroughly. It can be concluded that the required type of PBAs is different for various carrier ions. In particular, the desalination batteries worked with the same mechanism as aqueous batteries are also discussed in detail to introduce the application of PBAs in aqueous systems comprehensively. This report can help the readers to understand the relationship between physical/chemical characteristics and electrochemical properties for PBAs and find a way to fabricate high-performance PBAs in aqueous batteries and desalination batteries.