Lattice Breathing Inhibited Layered Vanadium Oxide Ultrathin Nanobelts for Enhanced Sodium Storage

Cobalt Ion-Stabilized VO2 for Aqueous Ammonium Ion Hybrid Supercapacitors

Aqueous ammonium ion hybrid supercapacitor (A-HSC) is an efficient energy storage device based on nonmetallic ion carriers (NH4+), which combines advantages such as low cost, safety, and sustainability. However, unstable electrode structures are prone to structural collapse in aqueous electrolytes, leading to fast capacitance decay, especially in host materials represented by vanadium-based oxidation. Here, the Co2+ preintercalation strategy is used to stabilize the VO2 tunnel structure and improve the electrochemical stability of the fast NH4+ storage process. In addition, the understanding of the NH4+ storage mechanism has been deepened through ex situ structural characterization and electrochemical analysis. The results indicate that Co2+ preintercalation effectively enhances the conductivity and structural stability of VO2, and inhibits the dissolution of V in aqueous electrolytes. In addition, the charge storage mechanisms of NH4+ intercalation/deintercalation and the reversible formation/fracture of hydrogen bonds were revealed.

Controllable fabrication of vanadium selenium nanosheets for a high-performance Na-ion battery anode

Vanadium selenium has gained attention as a potential anode for sodium-ion batteries (SIBs) due to the tunable crystal structure, effective channels for Na+ diffusion, and high theoretical specific capacity. However, the pursuit of vanadium selenium remains an enormous challenge. Herein, we demonstrated that V2Se9 nanosheets could be fabricated facilely and efficiently via a one-pot synthesis method with the careful selection of the solvent/surfactant. The V2Se9 anode have demonstrated excellent electrochemical performance for SIBs. An intercalation and conversion mechanism of Na-storage in V2Se9 were clarified by ex situ X-ray diffraction. This work develops an effective strategy to fabricate transition metal chalcogenides for high-performance sodium storage.

Vanadium and Niobium MXenes-Bilayered V2 O5 Asymmetric Supercapacitors

MXenes offer high metallic conductivity and redox capacitance that are attractive for high-power, high-energy storage devices. However, they operate limitedly under high anodic potentials due to irreversible oxidation. Pairing them with oxides to design asymmetric supercapacitors may expand the voltage window and increase the energy storage capabilities. Hydrated lithium preintercalated bilayered V2 O5 ( δ-Lix V2 O5 ·nH2 O) is attractive for aqueous energy storage due to its high Li capacity at high potentials; however, its poor cyclability remains a challenge. To overcome its limitations and achieve a wide voltage window and excellent cyclability, it is combined with V2 C and Nb4 C3 MXenes. Asymmetric supercapacitors employing lithium intercalated V2 C (Li-V2 C) or tetramethylammonium intercalated Nb4 C3 (TMA-Nb4 C3 ) MXenes as the negative electrode, and a δ-Lix V2 O5 ·nH2 O composite with carbon nanotubes as the positive electrode in 5 m LiCl electrolyte operate over wide voltage windows of 2 and 1.6 V, respectively. The latter shows remarkably high cyclability-capacitance retention of ≈95% after 10 000 cycles. This work highlights the importance of selecting appropriate MXenes to achieve a wide voltage window and a long cycle life in combination with oxide anodes to demonstrate the potential of MXenes beyond Ti3 C2 in energy storage.

Chemical Preintercalation Synthesis of Versatile Electrode Materials for Electrochemical Energy Storage

ConspectusThe widespread use of electrical plants and grids to generate, transmit, and deliver power to consumers makes electricity the most convenient form of energy to transport, control, and use. Balancing electricity demand with electricity supply requires a mechanism for energy storage, which is enabled by electrical energy storage devices such as batteries and supercapacitors. In addition to the grid-level energy storage, we have all witnessed the quick growth of a number of applications that require autonomous power, illustrated by the Internet of Things, and electrification of transport. Batteries, when developed for targeted applications with specific requirements, require new materials with improved performance enabled by rational design on the atomic level. The material tunability knobs include chemical composition, structure, morphology, and heterointerfaces, among others. Synthesis methods that could enable control of these parameters while offering versatility and being facile are highly desired.In this Account, we describe a synthesis strategy for the creation of new intercalation host oxides, hybrid materials, and compounds with oxide/carbon heterointerfaces for use as electrodes in intercalation batteries. We begin by introducing a strategy called the chemical preintercalation synthesis approach and describing processing steps that can be used to tune the material's chemical composition, structure, and morphology. We then show how the chemical preintercalation of inorganic ions can be used to improve the ion diffusion and stability of the synthesized materials. We reveal how confined interlayer water can be controlled and how the degree of hydration affects the electrochemical performance. This is followed by a demonstration of the chemical preintercalation of organic molecules leading to unprecedented expansion of the interlayer region up to ∼30 Å and initial electrochemical characterization of the obtained hybrid materials. We then present evidence that the carbonization of the interlayer organic molecules is an efficient synthetic pathway for creating oxide/carbon heterointerfaces and improving the electronic conductivity of oxides, which leads to improved stability and rate capability during electrochemical cycling. The examples discussed in this Account show that the chemical preintercalation synthesis approach opens pathways for the preparation of materials that have not been synthesized previously, such as new phases, hybrid materials, and 2D heterostructures with advanced functionalities. We demonstrate that chemical preintercalation can be used to effectively tune the chemistry of the confined interlayer region in layered phases and form tight oxide/carbon heterointerfaces enabling control of the material properties at the atomic level.

Hydrated lithium ions intercalated V2O5 with dual-ion synergistic insertion mechanism for high-performance aqueous zinc-ion batteries

Li_0.45V₂O₅·0.89H₂O (LVO) was successfully synthesized by wet-mixing of LiOH·H₂O and V₂O₅, with subsequent hydrothermal method for the first time. The hydrated lithium ions as the intercalated guest species were inserted into the V₂O₅ interlayer. The as-obtained LVO with a stable lamellar structure, enlarged interlayer space, weak interlayer repulsive force and low molecular weight, which shows a specific capacitance of 403 mAh g^-1 at 0.1 A g^-1, excellent rate capability and longlifespan with capacity retention of 86% over 1000 cycles at 10 A g^-1. Furthermore, the LVO-based AZIBs possess a synergistic insertion mechanism of Zn²⁺ and H⁺, that is the reason for its superior performance. This work provides an efficient design strategy for synthesizing advanced cathode materials for the high-performance Zn²⁺ energy storage system.

MWCNT synergy for boosting the electrochemical kinetics of V2O5 cathode for lithium-ion batteries

V2O5/MWCNT hybrid system has been developed and investigated as cathode in LIBs. The developed electrode shows superior performance as compare to pristine V2O5 and V2O5/rGO hybrid structure due to the synergy between V2O5 and MWCNT.

Carbon Quantum Dots Promote Coupled Valence Engineering of V2 O5 Nanobelts for High-Performance Aqueous Zinc-Ion Batteries

Aqueous Zn-ion batteries (ZIBs) have acquired the researchers' curiosity owing to their harmlessness, cost effectiveness and high theoretical capacity of Zn anode. However, desirable cathode materials with high-capacity and high-rate are still scarce. In this work, the formation of carbon quantum dots induced vanadium pentoxide nanobelts was demonstrated via a facile one-step hydrothermal method for ZIBs. It exhibited an excellent Zn ion storage capacity of 460 mA h g^-1 at 0.1 A g^-1 , superior rate capability and stable cycling performance (above 85 % capacity retention over 1500 cycles at 4 A g^-1 ). The electrochemical kinetics and zinc ion storage mechanism were also considered. An efficient architecture-coupled valence engineering in the hybrid cathode was proposed to improve the electric conductivity, Zn ion diffusion rate, and cycling stability for ZIBs. This work may be a great motivation for further research on V₂ O₅ or other vanadium-based materials for high-performance ZIBs.

Melamine-assisted synthesis of porous V2O3/N-doped carbon hollow nanospheres for efficient sodium-ion storage

Vanadium-based oxides with relatively high theoretical capacity have been regarded as promising electrode materials for boosting energy conversion and storage. However, their poor electrical conductivity usually leads to unsatisfied performance and poor cycling stability. Herein, uniform V₂O₃/N-doped carbon hollow nanospheres (V₂O₃/NC HSs) with mesoporous structures were successfully synthesized through a melamine-assisted simple hydrothermal reaction and carbonization treatment. We demonstrated that the introduction of melamine played an essential role in the construction of V₂O₃/NC HSs. Benefitting from the special mesoporous structure and large specific surface area, the as-obtained sample exhibited enhanced conductivity and structural stability. As a proof of concept, well-defined V₂O₃/NC HSs exhibited excellent cycling stability and rate performance for sodium-ion batteries, and achieved a discharge capacity of 263.8 mA h g^-1 at a current density of 1.0 A g^-1 after 1000 cycles, one of the best performances of V-based compounds. The enhanced performance could be attributed to the synergistic effect of the hollow structure and surface carbon coating. The present work describes the design of the morphology and structure of vanadium-based oxides for energy storage devices.

A novel synthesis towards a vanadium pentoxide porous nanodisk film as a cathode material for advanced Li-ion hybrid capacitors

A V2O5 porous nanodisk thin film is synthesized through a simple hydrothermal and subsequent VO2 template oxidation strategy. For the first time, V2O5 is employed as a cathode rather than an anode to construct lithium-ion hybrid capacitors. This design effectively utilizes the intrinsic layered structure of V2O5 for facile Li+ intercalation and facilitates the charge balance with the capacitive electrode, enabling superior performance of the device.

Strongly Coupled Pyridine-V2 O5 ·nH2 O Nanowires with Intercalation Pseudocapacitance and Stabilized Layer for High Energy Sodium Ion Capacitors

Developing pseudocapacitive cathodes for sodium ion capacitors (SICs) is very significant for enhancing energy density of SICs. Vanadium oxides cathodes with pseudocapacitive behavior are able to offer high capacity. However, the capacity fading caused by the irreversible collapse of layer structure remains a major issue. Herein, based on the Acid-Base Proton theory, a strongly coupled layered pyridine-V₂ O₅ ·nH₂ O nanowires cathode is reported for highly efficient sodium ion storage. By density functional theory calculations, in situ X-ray diffraction, and ex situ Fourier-transform infrared spectroscopy, a strong interaction between protonated pyridine and VO group is confirmed and stable during cycling. The pyridine-V₂ O₅ ·nH₂ O nanowires deliver long-term cyclability (over 3000 cycles), large pseudocapacitive behavior (78% capacitive contribution at 1 mV s^-1 ) and outstanding rate capability. The assembled pyridine-V₂ O₅ ·nH₂ O//graphitic mesocarbon microbead SIC delivers high energy density of ≈96 Wh kg^-1 (at 59 W kg^-1 ) and power density of 14 kW kg^-1 (at 37.5 Wh kg^-1 ). The present work highlights the strategy of realizing strong interaction in the interlayer of V₂ O₅ ·nH₂ O to enhance the electrochemical performance of vanadium oxides cathodes. The strategy could be extended for improving the electrochemical performance of other layered materials.

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.

Novel layered iron vanadate cathode for high-capacity aqueous rechargeable zinc batteries

A layered iron vanadate Fe5V15O39(OH)9·9H2O nanosheet is first introduced to an aqueous zinc battery system as a cathode material, which delivers a high capacity of 385 mA h g-1 at 0.1 A g-1 and remarkable cycling performance at high current density (over 80% capacity retention after 300 cycles at 5 A g-1).

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.

Large interlayer spacing vanadium oxide nanotubes as cathodes for high performance sodium ion batteries

Sodium ion batteries (SIBs), as a potential alternative to Li-ion batteries (LIBs), have attracted great attention from researchers.

H2V3O8 Nanowires as High-Capacity Cathode Materials for Magnesium-Based Battery

Magnesium-based batteries have received much attention as promising candidates to next-generation batteries because of high volumetric capacity, low price, and dendrite-free property of Mg metal. Herein, we reported H₂V₃O₈ nanowire cathode with excellent electrochemical property in magnesium-based batteries. First, it shows a satisfactory magnesium storage ability with 304.2 mA h g^-1 capacity at 50 mA g^-1. Second, it possesses a high-voltage platform of ∼2.0 V vs Mg/Mg²⁺. Furthermore, when evaluated as a cathode material for magnesium-based hybrid Mg²⁺/Li⁺ battery, it exhibits a high specific capacity of 305.4 mA h g^-1 at 25 mA g^-1 and can be performed in a wide working temperature range (-20 to 55 °C). Notably, the insertion-type ion storage mechanism of H₂V₃O₈ nanowires in hybrid Mg²⁺/Li⁺ batteries are investigated by ex situ X-ray diffraction and Fourier transform infrared. This research demonstrates that the H₂V₃O₈ nanowire cathode is a potential candidate for high-performance magnesium-based batteries.

Strategies for improving the lithium-storage performance of 2D nanomaterials

2D nanomaterials, including graphene, transition metal oxide (TMO) nanosheets, transition metal dichalcogenide (TMD) nanosheets, etc., have offered an appealing and unprecedented opportunity for the development of high-performance electrode materials for lithium-ion batteries (LIBs). Although significant progress has been made on 2D nanomaterials for LIB applications in the recent years, some major challenges still exist for the direct use of these sheet-like nanomaterials, such as their serious self-agglomerating tendency during electrode fabrication and low conductivity as well as the large volume changes over repeated charging–discharging cycles for most TMOs/TMDs, which have resulted in large irreversible capacity, low initial Coulombic efficiency and fast capacity fading. To address these issues, considerable progress has been made in the exploitation of 2D nanosheets for enhanced lithium storage. In this review, we intend to summarize the recent progress on the strategies for enhancing the lithium-storage performance of 2D nanomaterials, including hybridization with conductive materials, surface/edge functionalization and structural optimization. These strategies for manipulating the structures and properties of 2D nanomaterials are expected to meet the grand challenges for advanced nanomaterials in clean energy applications and thus provide access to exciting materials for achieving high-performance next-generation energy-storage devices.

Energy storage through intercalation reactions: electrodes for rechargeable batteries

Electrochemical energy storage has been an important enabling technology for modern electronics of all kinds, and will grow in importance as more electric vehicles and grid-scale storage systems are deployed. We briefly review the history of intercalation electrodes and basic concepts pertaining to batteries based on intercalation reactions. Then we summarize how the critical performance metrics—energy density, power density, safety and stability—relate back to electrode materials properties, and how these materials properties are related to fundamental chemical and physical structure relationships highlighted with the most recent research advancement. Challenges and avenues for further research have been highlighted throughout.

Ultrafine Nb2O5 Nanocrystal Coating on Reduced Graphene Oxide as Anode Material for High Performance Sodium Ion Battery

Ultrafine niobium oxide nanocrystals/reduced graphene oxide (Nb2O5 NCs/rGO) was demonstrated as a promising anode material for sodium ion battery with high rate performance and high cycle durability. Nb2O5 NCs/rGO was synthesized by controllable hydrolysis of niobium ethoxide and followed by heat treatment at 450 °C in flowing forming gas. Transmission electron microscopy images showed that Nb2O5 NCs with average particle size of 3 nm were uniformly deposited on rGO sheets and voids among Nb2O5 NCs existed. The architecture of ultrafine Nb2O5 NCs anchored on a highly conductive rGO network can not only enhance charge transfer and buffer the volume change during sodiation/desodiation process but also provide more active surface area for sodium ion storage, resulting in superior rate and cycle performance. Ex situ XPS analysis revealed that the sodium ion storage mechanism in Nb2O5 could be accompanied by Nb(5+)/Nb(4+) redox reaction and the ultrafine Nb2O5 NCs provide more surface area to accomplish the redox reaction.

Correlating Lithium Hydroxyl Accumulation with Capacity Retention in V2O5 Aerogel Cathodes

V2O5 aerogels are capable of reversibly intercalating more than 5 Li(+)/V2O5 but suffer from lifetime issues due to their poor capacity retention upon cycling. We employed a range of material characterization and electrochemical techniques along with atomic pair distribution function, X-ray photoelectron spectroscopy, and density functional theory to determine the origin of the capacity fading in V2O5 aerogel cathodes. In addition to the expected vanadium redox due to intercalation, we observed LiOH species that formed upon discharge and were only partially removed after charging, resulting in an accumulation of electrochemically inactive LiOH over each cycle. Our results indicate that the tightly bound water that is necessary for maintaining the aerogel structure is also inherently responsible for the capacity fade.

Investigation of the Na Intercalation Mechanism into Nanosized V2O5/C Composite Cathode Material for Na-Ion Batteries

There is a significant interest to develop high-performance and cost-effective electrode materials for next-generation sodium ion batteries. Herein, we report a facile synthesis method for nanosized V2O5/C composite cathodes and their electrochemical performance as well as energy storage mechanism. The composite exhibits a discharge capacity of 255 mAh g(-1) at a current density of 0.05 C, which surpasses that of previously reported layered oxide materials. Furthermore, the electrode shows good rate capability; discharge capacity of 160 mAh g(-1) at a current density of 1 C. The reaction mechanism of V2O5 upon sodium insertion/extraction is investigated using ex situ X-ray diffraction (XRD) and synchrotron based near edge X-ray absorption fine structure (NEXAFS) spectroscopy. Ex situ XRD result of the fully discharged state reveals the appearance of NaV2O5 as a major phase with minor Na2V2O5 phase. Upon insertion of sodium into the array of parallel ladders of V2O5, it was confirmed that lattice parameter of c is increased by 9.09%, corresponding to the increase in the unit-cell volume of 9.2%. NEXAFS results suggest that the charge compensation during de/sodiation process accompanied by the reversible changes in the oxidation state of vanadium (V(4+) ↔ V(5+)).

Flexible additive free H2V3O8nanowire membrane as cathode for sodium ion batteries

A flexible additive free H₂V₃O₈nanowire membrane is presented as a promising sodium-ion battery cathode.

Rational selection of amorphous or crystalline V2O5 cathode for sodium-ion batteries

Amorphous and crystalline V₂O₅ cathodes in sodium ion batteries express inverse capacity values at low and high current densities.