Rechargeable Sodium-Ion Battery: High-Capacity Ammonium Vanadate Cathode with Enhanced Stability at High Rate

Enhanced sulfamethoxazole photodegradation by N-SrTiO3/NH4V4O10 S-scheme photocatalyst: DFT calculation and photocatalytic mechanism insight

In this study, we synthesized a N-SrTiO₃/NH₄V₄O₁₀ S-scheme photocatalyst by modifying NH₄V₄O₁₀ nanosheets with various proportions of N-doped SrTiO₃ nanoparticles using a mild hydrothermal method.Density Functional Theory(DFT) calculations were employed to elucidate thephotocatalytic mechanism, while the electron-hole transfer and separation of the S-type heterojunction were further characterized experimentally. The photocatalyst was applied to the photodegradation of sulfamethoxazole (SMX), a common water pollutant. Among all the prepared photocatalysts, 30 wt% N-SrTiO₃/NH₄V₄O₁₀ (NSN-30) displayed the highest photocatalytic performance. This was attributed to the facile electron transfer mechanism of the S-scheme heterojunction, which facilitated the effective separation of electron-holes and preserved the strong redox property of the catalyst. The possible intermediates anddegradation pathwaysin thephotocatalytic systemwere explored usingelectron paramagnetic resonance(EPR) and DFT calculations. Our findings demonstrate the potential of semiconductor catalysts to remove antibiotics from aqueous environments usinggreen energy.

How About Vanadium-Based Compounds as Cathode Materials for Aqueous Zinc Ion Batteries?

Aqueous zinc-ion batteries (AZIBs) stand out among many monovalent/multivalent metal-ion batteries as promising new energy storage devices because of their good safety, low cost, and environmental friendliness. Nevertheless, there are still many great challenges to exploring new-type cathode materials that are suitable for Zn²⁺ intercalation. Vanadium-based compounds with various structures, large layer spacing, and different oxidation states are considered suitable cathode candidates for AZIBs. Herein, the research advances in vanadium-based compounds in recent years are systematically reviewed. The preparation methods, crystal structures, electrochemical performances, and energy storage mechanisms of vanadium-based compounds (e.g., vanadium phosphates, vanadium oxides, vanadates, vanadium sulfides, and vanadium nitrides) are mainly introduced. Finally, the limitations and development prospects of vanadium-based compounds are pointed out. Vanadium-based compounds as cathode materials for AZIBs are hoped to flourish in the coming years and attract more and more researchers' attention.

A full flexible NH4+ ion battery based on the concentrated hydrogel electrolyte for enhanced performance

Nonmetal ammonium  NH 4 +  ions have recently been explored as effective charge carriers in battery systems due to their abundancy, light weight, small hydration shells in water. The research concerning the use of NH 4 +  ion redox chemistry in flexible batteries, is still in its infancy. For the first time, we report a flexible full  NH 4 +  ion battery (AIB) composed of a concentrated hydrogel electrolyte sandwiched between NH4V3O8·2.9H2O nanobelts cathode and polyaniline (PANI) anode. The hydrogel electrolyte is simply synthesized by using ammonium sulfate, xanthan gum and water. As a reference, AIB based on the liquid aqueous electrolyte is prepared first, which exhibits a capacity of 121 mAh g-1  and capacity retention of 95% after 400 cycles at a specific current of 0.1 A g -1. The full flexible AIBs are then fabricated using hydrogel electrolytes with varied salt concentrations, to maximize the electrochemical performance. It is found that the battery based on the hydrogel electrolyte prepared from 3 M ammonium sulfate solution shows the best electrochemical performance i.e., a capacity of 60 mAh g-1 while maintaining a capacity retention of 88% after 250 cycles at a specific current of 0.1 A g  -1. Moreover, the flexible AIB retains excellent electrochemical performance when bent at different angles, demonstrating remarkable mechanical strength and flexibility. Therefore, this study sheds new light on the utilization of concentrated hydrogel electrolyte in the AIB chemistry, for future developments of new electrochemical energy storage technology.

Magnesium Ion Storage Properties in a Layered (NH4)2V6O16·1.5H2O Nanobelt Cathode Material Activated by Lattice Water

Magnesium ion batteries have attracted increasing attention as a promising energy storage device due to the high safety, high volumetric capacity, and low cost of Mg. However, the strong Coulombic interactions between Mg²⁺ ions and cathode materials seriously hinder the electrochemical performance of the batteries. To seek a promising cathode material for magnesium ion batteries, in this work, (NH₄)₂V₆O₁₆·1.5H₂O and water-free (NH₄)₂V₆O₁₆ materials are synthesized by a one-step hydrothermal method. The effects of NH₄⁺ and lattice water on the Mg²⁺ storage properties in these kinds of layered cathode materials are investigated by experiments and first-principles calculations. Lattice water is demonstrated to be of vital importance for Mg²⁺ storage, which not only stabilizes the layered structure of (NH₄)₂V₆O₁₆·1.5H₂O but also promotes the transport kinetics of Mg²⁺. Electrochemical experiments of (NH₄)₂V₆O₁₆·1.5H₂O show a specific capacity of 100 mA·h·g^-1 with an average discharge voltage of 2.16 V vs Mg²⁺/Mg, highlighting the potential of (NH₄)₂V₆O₁₆·1.5H₂O as a high-voltage cathode material for magnesium ion batteries.

Enhanced Reversible Zinc Ion Intercalation in Deficient Ammonium Vanadate for High-Performance Aqueous Zinc-Ion Battery

Ammonium vanadate with bronze structure (NH4V4O10) is a promising cathode material for zinc-ion batteries due to its high specific capacity and low cost. However, the extraction of [Formula: see text] at a high voltage during charge/discharge processes leads to irreversible reaction and structure degradation. In this work, partial [Formula: see text] ions were pre-removed from NH4V4O10 through heat treatment; NH4V4O10 nanosheets were directly grown on carbon cloth through hydrothermal method. Deficient NH4V4O10 (denoted as NVO), with enlarged interlayer spacing, facilitated fast zinc ions transport and high storage capacity and ensured the highly reversible electrochemical reaction and the good stability of layered structure. The NVO nanosheets delivered a high specific capacity of 457 mAh g-1 at a current density of 100 mA g-1 and a capacity retention of 81% over 1000 cycles at 2 A g-1. The initial Coulombic efficiency of NVO could reach up to 97% compared to 85% of NH4V4O10 and maintain almost 100% during cycling, indicating the high reaction reversibility in NVO electrode.

NH4V4O10 nanobelts vertically grown on 3D TiN nanotube arrays as high-performance electrode materials of supercapacitors

High performance supercapacitor without binders has attracted wide attention as an energy storage device. In this work, novel NH4V4O10 nanobelts were successfully synthesized and decorated into TiN nanotube arrays by a simple hydrothermal method. The as-prepared no-binder electrode hybrids exhibited excellent electrochemical performances with a specific capacitance of 749.0 F g-1 at 5 mV s-1 and a capacity retention of 85.7% after 200 cycles, which makes it an appealing candidate for electrode materials of supercapacitors.

Freestanding Sodium Vanadate/Carbon Nanotube Composite Cathodes with Excellent Structural Stability and High Rate Capability for Sodium-Ion Batteries

Sodium vanadate NaV₆O₁₅ (NVO) is one of the most promising cathode materials for sodium-ion batteries because of its low cost and high theoretical capacity. Nevertheless, NVO suffers from fast capacity fading and poor rate capability. Herein, a novel free-standing NVO/multiwalled carbon nanotube (MWCNT) composite film cathode was synthesized and designed by a simple hydrothermal method followed by a dispersion technique with high safety and low cost. The kinetics analysis based on cyclic voltammetry measurements reveals that the intimate integration of the MWCNT 3D porous conductive network with the 3D pillaring tunnel structure of NVO nanorods enhances the Na⁺ intercalation pseudocapacitive behavior, thus leading to exceptional rate capability and long lifespan. Furthermore, the NVO/MWCNT composite exhibits excellent structural stability during the charge/discharge process. With these benefits, the composite delivers a high discharge capacity of 217.2 mA h g^-1 at 0.1 A g^-1 in a potential region of 1.5-4.0 V. It demonstrates a superior rate capability of 123.7 mA h g^-1 at 10 A g^-1. More encouragingly, it displays long lifespan; impressively, 96% of the initial capacity is retained at 5 A g^-1 for over 500 cycles. Our work presents a promising strategy for developing electrode materials with a high rate capability and a long cycle life.

Vanadium oxide bronzes as cathode active materials for non-lithium-based batteries

Lithium as critical resource prompted interest for non-lithium-based batteries. This highlight review discusses vanadium oxide bronzes as one of the material families being considered as cathode for non-lithium-based batteries.

A Review of Battery Materials as CDI Electrodes for Desalination

The world is suffering from chronic water shortage due to the increasing population, water pollution and industrialization. Desalinating saline water offers a rational choice to produce fresh water thus resolving the crisis. Among various kinds of desalination technologies, capacitive deionization (CDI) is of significant potential owing to the facile process, low energy consumption, mild working conditions, easy regeneration, low cost and the absence of secondary pollution. The electrode material is an essential component for desalination performance. The most used electrode material is carbon-based material, which suffers from low desalination capacity (under 15 mg·g−1). However, the desalination of saline water with the CDI method is usually the charging process of a battery or supercapacitor. The electrochemical capacity of battery electrode material is relatively high because of the larger scale of charge transfer due to the redox reaction, thus leading to a larger desalination capacity in the CDI system. A variety of battery materials have been developed due to the urgent demand for energy storage, which increases the choices of CDI electrode materials largely. Sodium-ion battery materials, lithium-ion battery materials, chloride-ion battery materials, conducting polymers, radical polymers, and flow battery electrode materials have appeared in the literature of CDI research, many of which enhanced the deionization performances of CDI, revealing a bright future of integrating battery materials with CDI technology.

In Operando Synchrotron Studies of NH4+ Preintercalated V2O5·nH2O Nanobelts as the Cathode Material for Aqueous Rechargeable Zinc Batteries

NH₄⁺ preintercalated V₂O₅·nH₂O nanobelts with a large interlayer distance of 10.9 Å were prepared by the hydrothermal method. The material showed a large specific capacity of 391 mA·h·g^-1 at the 500 mA·g^-1 current density in aqueous rechargeable zinc batteries. In operando synchrotron X-ray diffraction demonstrated that the material experienced reversible solid-solution reaction and two-phase transition during charge-discharge cycling, accompanied by the reversible formation/decomposition of a ZnSO₄Zn₃(OH)₆·5H₂O byproduct. In operando X-ray absorption spectroscopy confirmed the reversible reduction/oxidation of V, together with small changes in the VO₆ local structure. The formation of byproduct was attributed to the dehydration of [Zn(H₂O)₆]²⁺, which concurrently improved the desolvation of [Zn(H₂O)₆]²⁺ into Zn²⁺. Bond valence sum map analysis and electrochemical impedance spectroscopy demonstrated that the byproduct improved the charge transfer kinetics of the electrode. Cyclic voltammetry and galvanostatic intermittent titration technique showed that the electrode reaction was dominated by ionic intercalation where the discharge capacity in the voltage window of 1.4-0.85 V was attributed to the intercalation of [Zn(H₂O)₆]²⁺, followed by the intercalation of Zn²⁺ at 0.85-0.4 V.

Exploring new hydrated delta type vanadium oxides for lithium intercalation

Three hydrated double layered vanadium oxides, namely Na_0.35V₂O₅·0.8(H₂O), K_0.36(H₃O)_0.15V₂O₅ and (NH₄)_0.37V₂O₅·0.15(H₂O), were obtained by using mild hydrothermal conditions. Their delta type structural frameworks were solved by high-resolution synchrotron X-ray powder diffraction and the interlayer spacings were interpreted from difference Fourier maps. The inter-slab distances are modulated by the water content and the special arrangements of the alkali and ammonium cations. The XPS measurements denote mixed valence systems with high contents of V⁴⁺ ions up to 40%. The monitoring of the V⁴⁺ EPR signal over time suggests a reduction of the electronic delocalization on account of the partial oxidation to V⁵⁺. The electrochemical performance of the active phases is strongly conditioned by the vacuum-drying process of the electrodes, showing better capacity retention when vacuum is not applied. In situ X-ray diffraction shows a structural mechanism of contraction/expansion of the bilayers upon lithium insertion/extraction where the alkali ions behave as structural stabilizers. Galvanostatic cycling at very low current density implies migration of the alkali "pillars" triggering the collapse of the structure.

Practical Aqueous Calcium-Ion Battery Full-Cells for Future Stationary Storage

There is a pressing need for high-rate cycling and cost-effective stationary energy storage systems in concomitance with the fast development of solar, wind, and other types of renewable sources of energy. Aqueous rechargeable Ca-ion batteries have the potential to meet the growing demands of stationary energy storage devices because they are abundant and safe; they can also be manufactured at a low-cost and have a higher volumetric capacity. In this study, we have demonstrated a low-cost, safe, aqueous Ca-ion battery that is based on a low potential, lower specific weight, in situ polymerized polyaniline as an anode, and a high redox-potential open-framework structured potassium copper hexacyanoferrate as a cathode. The charge-discharge mechanism of this battery includes doping/dedoping of NO₃^- at the anode, and intercalation and deintercalation of Ca-ion at the cathode. This Ca-ion battery works successfully in a 2.5 M Ca(NO₃)₂ aqueous electrolyte that exhibits 70 Wh kg^-1 specific energy at 250 W kg^-1 and even maintains a high energy density of 53 Wh kg^-1 at a higher rate of 950 W kg^-1; this indicates a good rate capability (calculation based on anode active mass). At 0.8 A g^-1, the battery provides an average specific capacity of 130 mA h g^-1, exhibiting high Coulombic efficiency (∼96%), with 95% capacity retention of over 200 cycles across its life span, which is a new achievement in the electrochemical performance of aqueous Ca-ion batteries. Furthermore, the calcium-ion storage mechanism is investigated using high-end X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) measurements. Thus, this significant electrochemical performance of the anode and the cathode renders the battery a promising candidate in grid-scale storage applications.

A High-Capacity Ammonium Vanadate Cathode for Zinc-Ion Battery

Given the advantages of being abundant in resources, environmental benign and highly safe, rechargeable zinc-ion batteries (ZIBs) enter the global spotlight for their potential utilization in large-scale energy storage. Despite their preliminary success, zinc-ion storage that is able to deliver capacity > 400 mAh g-1 remains a great challenge. Here, we demonstrate the viability of NH4V4O10 (NVO) as high-capacity cathode that breaks through the bottleneck of ZIBs in limited capacity. The first-principles calculations reveal that layered NVO is a good host to provide fast Zn2+ ions diffusion channel along its [010] direction in the interlayer space. On the other hand, to further enhance Zn2+ ion intercalation kinetics and long-term cycling stability, a three-dimensional (3D) flower-like architecture that is self-assembled by NVO nanobelts (3D-NVO) is rationally designed and fabricated through a microwave-assisted hydrothermal method. As a result, such 3D-NVO cathode possesses high capacity (485 mAh g-1) and superior long-term cycling performance (3000 times) at 10 A g-1 (~ 50 s to full discharge/charge). Additionally, based on the excellent 3D-NVO cathode, a quasi-solid-state ZIB with capacity of 378 mAh g-1 is developed.

N-Doped Carbon Nanofibers with Interweaved Nanochannels for High-Performance Sodium-Ion Storage

Although graphite materials have been applied as commercial anodes in lithium-ion batteries (LIBs), there still remain abundant spaces in the development of carbon-based anode materials for sodium-ion batteries (SIBs). Herein, an electrospinning route is reported to fabricate nitrogen-doped carbon nanofibers with interweaved nanochannels (NCNFs-IWNC) that contain robust interconnected 1D porous channels, produced by removal of a Te nanowire template that is coelectrospun within carbon nanofibers during the electrospinning process. The NCNFs-IWNC features favorable properties, including a conductive 1D interconnected porous structure, a large specific surface area, expanded interlayer graphite-like spacing, enriched N-doped defects and active sites, toward rapid access and transport of electrolyte and electron/sodium ions. Systematic electrochemical studies indicate that the NCNFs-IWNC exhibits an impressively high rate capability, delivering a capacity of 148 mA h g^-1 at current density of as high as 10 A g^-1 , and has an attractively stable performance over 5000 cycles. The practical application of the as-designed NCNFs-IWNC for a full SIBs cell is further verified by coupling the NCNFs-IWNC anode with a FeFe(CN)₆ cathode, which displays a desirable cycle performance, maintaining acapacity of 97 mA h g^-1 over 100 cycles.

Superior Sodium Storage of Carbon-Coated NaV6O15 Nanotube Cathode: Pseudocapacitance Versus Intercalation

To realize the effect of Na⁺ pseudocapacitance on the sodium storage of cathode materials, clewlike carbon-coated sodium vanadium bronze (NaV₆O₁₅) nanotubes (Na-VBNT@C) were synthesized via a facile combined sol-gel/hydrothermal method. The resultant Na-VBNT@C delivers high reversible capacities of 209 and 105 mA h g^-1 at the rates of 0.1 and 10 C, respectively. Notably, at the higher rate of 5 C (1250 mA g^-1), it can retain 94% of the initial capacity after 3000 cycles. It was found that the outstanding rate performance and the long-term cycling life of Na-VBNT@C are primarily due to the Na⁺ pseudocapacitance. Our study reveals that the design of Na⁺ pseudocapacitance is beneficial for harvesting the superior performance of NaV₆O₁₅ cathode material in sodium-ion batteries.

A 3D interconnected NH4Fe0.6V2.4O7.4@C nanocomposite with superior sodium storage properties

A novel 3D interconnected NH4Fe0.6V2.4O7.4@C nanocomposite was in situ synthesized through a facile hydrothermal reaction at low temperature (98 °C), and its electrochemical performance as a cathode for sodium-ion batteries (SIBs) was investigated for the first time. Under the intercalation of Fe3+ and carbon-coating, as-prepared samples turned to 3D interconnected structures, which were composed of NH4Fe0.6V2.4O7.4 nanoparticles and carbon chains. The 3D interconnected NH4Fe0.6V2.4O7.4@0.5 wt%C nanocomposite exhibits a high discharge specific capacity of 306 mA h g-1 at a current density of 20 mA g-1 and a high-rate capacity of 130 mA h g-1 at 0.4 A g-1. The results of EIS and ex situ SEM indicated that the 3D interconnected NH4Fe0.6V2.4O7.4@0.5 wt%C nanocomposite possesses good electrical conductivity and structural stability. The ex situ XRD results suggest that NH4Fe0.6V2.4O7.4@0.5 wt%C undergoes a reversible insertion/de-insertion mechanism during a charge/discharge process. Our work demonstrates that the 3D interconnected NH4Fe0.6V2.4O7.4@C nanocomposite material could be considered as a potential cathode for sodium ion batteries.

Structural transformation during Li/Na insertion and theoretical cyclic voltammetry of the δ-NH4V4O10 electrode: a first-principles study

A double layer δ-NH₄V₄O₁₀, due to its high energy storage capacity and excellent rate capability, is a very promising cathode material for Li-ion and Na-ion batteries for large-scale renewable energy storage in transportation and smart grids.