Sodium Vanadium Research Articles

Simultaneous cation-anion regulation of sodium vanadium phosphate cathode materials for high-energy and cycle-stable sodium-ion batteries

Developing advanced Na3V2(PO4)3 (NVP) cathodes with both improved capacity and reversibility is of great importance for achieving next-generation sodium-ion batteries with high energy density and long lifespan, however, high-capacity cathode materials generally suffer from short cycle-life. In this study, a simultaneous cation-anion regulation strategy is put forward to design high-capacity and cycle-stable NVP cathode materials. Specifically, anionic silicate is introduced to substitute the phosphate and improve Na+-storage capacity, meanwhile, cationic K+ is introduced as pillar ions to stabilize the crystal structure and enhance the reversibility of the NVP cathodes. The as-achieved Na3.24K0.10V2.01(PO4)2.94(SiO4)0.14 (KSi-NVP) delivered a high capacity of 116.3 mAh g−1 at 0.5 C and an impressive structural stability with only an ultra-low capacity decay rate of 0.0056% per cycle at 20 C, outperformed pristine Na3V2(PO4)3 (109.4 mAh g−1 and 0.0290% under the same test conditions). After coupling a commercial hard carbon anode, the KSi-NVP cathode enabled an advanced full cell with high specific energy density of 348.2 Wh kg−1 and a long lifespan of 900 cycles at 5 C with a remarkable Coulomb efficiency (CE) of 99.99%.

High energy-power characteristics of microstructurally engineered sodium vanadium phosphate in full cell level

The demand for hybrid devices which can deliver high power with large storage capabilities are increasing day-by-day. Sodium based hybrid devices are an appropriate choice to meet the current necessities by considering the abundance, cost and performance. Sodium vanadium phosphate nanocomposite (NC-NVP) has been engineered by making the particles embedded within nitrogen doped mesoporous carbon matrix. Using NC-NVP, a hybrid cell has been devised with activated carbon in an asymmetric cell fashion and compared it with symmetric cell. Asymmetric and symmetric cells have demonstrated cell level energy densities of 77 & 65 and 59 & 46 Wh kg−1 at 0.1 and 1 A g−1 respectively, which are much higher than many reported values. At 2 A g−1, both configurations delivered high power (3722 and 3750 W kg−1) within 1.4 and 1.5 min at retentions of 63 and 51 % after 14,000 cycles respectively. Excellent electrochemical performance suggests that dual mechanism of intercalation in NC-NVP and surface/sub-surface charge storage in nitrogen-doped mesoporous carbon are playing major role. The obtained results are superior to different hybrid devices reported earlier which paves a way for demonstrating sodium-ion device for practical applications.

Proton-Induced Defect-Rich Vanadium Oxides as Reversible Polysulfide Conversion Sites for High-Performance Lithium Sulfur Batteries.

Lithium-sulfur (Li-S) batteries have attracted attention due to their high theoretical energy density, natural abundance, and low cost. However, the diffusion of polysulfides decreases the utilization and further degrades the battery's life. We have successfully fabricated a defect-rich layered sodium vanadium oxide with proton doping (HNVO) nanobelt and used it as the functional interface layer on the separator in Li-S batteries. Benefiting from the abundant defects of NVO and the catalytic activity of metal vanadium in the electrochemical process, the shuttle of polysulfides was greatly decreased by reversible chemical adsorption. Moreover, the extra graphene layer contributes to accelerating the charge carrier at high current densities. Therefore, a Li-S battery with G@HNVO delivers a high capacity of 1494.8 mAh g-1 at 0.2 C and a superior cycling stability over 700 cycles at 1 C. This work provides an effective strategy for designing the electrode/separator interface layer to achieve high-performance Li-S batteries.

Study on sodium storage properties of manganese‐doped sodium vanadium phosphate cathode materials

AbstractNa+ superionic conductor (NASICON)‐structured Na4VMn(PO4)3 (NVMP) possesses stable cycling performance at 2.5–3.8 V by replacing V with lower cost Mn but suffers rapid capacity decay when further widening the voltage to 2.5–4.2 V, owing to a less stable V4+/V5+ redox couple. Herein, to stabilize the V4+/V5+ couple and improve the reversibility, a series of carbon‐coated NVMP (NVMP@C) with different V/Mn ratios are compared, among which, Na3.25V1.75Mn0.25(PO4)3@C delivers an additional reversible V4+/V5+ capacity of 7 mAh g−1 at the voltage of 3.9–4.2 V. Based on this, to further activate the capacity of V4+/V5+, Al‐doped Na3.25V1.75−yMn0.25Aly(PO4)3 structures are synthesized. When 0.5 Al is doped, 15 mAh g−1 capacity corresponding to V4+/V5+ can be released. In addition, it is found that the activation of V4+/V5+ is not conducive to electrochemical reversibility and C‐rate performance, owing to the shrinkage of the whole framework structure with the oxidization of V4+ to V5+.

Na‐Rich Na3V2(PO4)3 Cathodes for Long Cycling Rechargeable Sodium Full Cells

AbstractNASICON‐type sodium vanadium phosphate (Na3V2(PO4)3, or NVP) cathode materials have great potential for fast charging and long cycling sodium‐ion batteries (SIBs) similar to lithium iron phosphate (LiFePO4, or LFP) cathode materials used in lithium‐ion batteries (LIBs). However, the cycle life and energy density in the full cell using NVP materials need to be significantly improved. This paper investigates the degradation mechanisms of NVP‐based SIBs and identifies the Na loss from the cathode to the anode solid electrolyte interphase (SEI) reactions as the main cause of capacity degradation. A new Na‐rich NVP cathode (e.g., Na4V2(PO4)3, or Na4VP) is developed to address the Na loss problem. Conventional NVP can be easily transformed into the Na4VP by a facile and fast chemical solution treatment (30 s). Na‐free‐anode Na4VP and hard carbon‐Na4VP full cells are assembled to evaluate the electrochemical properties of the Na‐rich NVP cathode. The Na4VP cathode provides excess Na to compensate for the Na loss, resulting much longer cycle life in the full cells (>400 cycles) and a high specific energy and power density. Good low‐temperature performance is also observed.

Mixed Valanced V3+,V2+ Phosphate Na7V4(PO4)6: A Structural Analogue of Mineral Yurmarinite

Two sodium vanadium phosphates, synthetic analogues of the minerals kosnarite, Na3V2(PO4)3, and yurmarinite, Na7V4(PO4)6, were obtained by hydrothermal synthesis simulating a natural hydrothermal solution. While the Na3V2(PO4)3 phase belongs to the NASICON family and is well-known for its high-ionic conductivity, the new Na7V4(PO4)6 compound is a rare case of V2+-containing oxosalts, which are hard to prepare due to their instability in air. Here we report the crystal structure of heterovalent vanadium phosphate studied by single crystal X-ray diffraction, XANES spectroscopy, and topological ion migration modelling. A discussion of divalent vanadium compounds of both natural and synthetic origin is also given, with a review of the methods for their synthesis and a comparative analysis of V–O bond lengths.

Sodium-ion conducting pseudosolid electrolyte for energy-dense, sodium-metal batteries

A liquid electrolyte based on the addition of a sodium salt in glyme solvent is encapsulated within a polymer-modified mesoporous silica matrix enabling the fabrication of a pseudosolid, sodium-ion electrolyte. This ionogel electrolyte is stable in contact with sodium metal leading to low overpotentials for sodium metal plating/stripping along with high Na+ conductivity and > 4 V electrochemical stability window. Sodium-metal batteries with sodium vanadium fluorophosphate positive electrode achieve over 400 Wh kg−1 at 0.5C.

(Digital Presentation) Advanced Intercalation Electrode Materials for Calcium Rechargeable Batteries

The growing demand for electric vehicles and stationary energy storage systems calls for developing next-generation batteries that combine high energy, high power and low cost. Among many post lithium-ion batteries, calcium rechargeable batteries utilizing divalent Ca2+ ion charge carriers are expected to offer clear benefits in affordability of batteries along with the potentially high energy density, due to the abundance of calcium in earth crust (46600 ppm versus 20 ppm for lithium) and the low redox potential of Ca/Ca2+ (-2.9 V vs. standard hydrogen electrode). Recent efforts on the development of negative electrodes, such as elemental calcium metal and natural graphite, has brought the rechargeable calcium chemistries a step closer to a practically feasible battery system. However, the lack of suitable cathode is the Achille’s heal of the calcium rechargeable battery technology.[1] The relatively large ionic radius and divalent nature of Ca ions make the intercalation kinetics generally sluggish in intercalation hosts. Moreover, a large Ca2+ intercalation is supposed to cause extended volume changes of the host, triggering a premature degradation of the electrode structure. In this talk, I would like to present our recent findings in graphite anode and polyanionic cathode materials as intercalation electrodes in high performance non-aqueous calcium rechargeable batteries. We demonstrated that a large amount of Ca ions can be reversibly (de)intercalation in graphite for Ca ion batteries by identifying a proper electrolyte to promote the solvated-ion co-intercalation reactions.[2] The solvated-Ca-ion co-intercalation chemistry is comprehensively investigated by combining first principle calculations and synchrotron in-situ X-ray diffraction. For cathodes, we find that the open-framework sodium vanadium fluorophosphate can function as a stable and fast-kinetic Ca2+ intercalation host with an extremely low capacity degradation rate of 0.02% per cycle over 500 cycles.[3] This value records the best stability reported for Ca ion battery cathodes so far. Through this talk, it is believed that the new findings in discovering novel materials or intercalation chemistries will be of great interest of the community working on multivalent ion batteries and other energy storage technologies.Reference:[1] C Chen, F Shi, ZL Xu, Advanced electrode materials for nonaqueous calcium rechargeable batteries, J. Mater. Chem. A, 2021, 9, 11908-11930[2] Z.L. Xu, J. Park, J. Wang, H. Moon, G. Yoon, J. Lim, Y.J. Ko, S.P. Cho, S.Y. Lee and K. Kang, A new high-voltage calcium intercalation host for ultra-stable and high-power calcium rechargeable batteries, Nat. Commun. 2021, doi:10.1038/s41467-021-23703-x.[3] J. Park,† Z.L. Xu,† G. Yoon,† S.K. Park, J. Wang, H. Hyun, H. Park, J. Lim, Y.J. Ko and K. Kang, Stable and High power calcium ion batteries enabled by calcium intercalation in graphite, Adv. Mater. 2020, 32.4: 1904411.

Ti3C2Tx film current collectors for high-performance sodium-ion batteries

Sodium-ion batteries (SIBs) are ideal technologies for large-scale energy storage systems because of their abundant resources and low cost. However, Al foil, the current collector of sodium-ion battery, has a great influence on the performance of the battery, but it has rarely been studied. In this paper, we prove that the Ti3C2Tx MXene current collector can make a stronger connection with the electrode, lowering the electrode-collector interface resistance considerably. When compared to Al current collectors in SIBs, the Ti3C2Tx MXene current collector reduces polarization and enhances performance. the sodium vanadium phosphate(NVP) electrode with Ti3C2Tx MXene current collector exhibits significantly enhanced rate capability (81.9 mAh g−1 at 500 mA g−1) and cycling performance (81.5% over 200 cycles at 1C) than Al foil. The results show that Ti3C2Tx MXene current collector has a broad prospect in the application of high power SIB battery.

Recovery of Tungsten and Vanadium from Spent Selective Catalytic Reduction Catalysts by Soda Roasting: A Mechanistic Study

This research investigated how soda roasting, which alters the roasting temperature and sodium carbonate concentration, recovers tungsten and vanadium from used selective catalytic reduction (SCR) catalysts. The ideal sodium carbonate content and roasting temperature were determined to be 800 °C and 30 wt%, respectively. Under these circumstances, tungsten and vanadium recoveries were 82.63% and 90.07%, respectively. In order to understand the roasting process, the compositions and morphologies of the original catalyst and specimens after roasting were examined by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. In addition, the thermodynamic parameters associated with this process were calculated using the HSC 6.0 program to confirm compositional changes during roasting, the result shows that the chemical reactions among vanadium, tungsten, titanium and sulfur with sodium carbonate have priority in this system, as V2O5= SO3> WO3> TiO2; And the phases formation of vanadium and titanium are different at different temperatures and the amount of sodium carbonate, such as Na2V2O6, NaVO3, Na3VO4, VO2, Na2O* TiO2, Na2O* 3TiO2, 4Na2O* 5TiO2, and so on. Therefore, the recovery of vanadium and tungsten is significantly influenced by the other catalyst components as well as the reaction conditions. Based on this combination of experimental study and theoretical calculations, a technique for recovering tungsten and vanadium from spent SCR catalysts by soda roasting is suggested.

Design of antimony nanocomposite for high areal capacity sodium battery anodes

Antimony (Sb) is attractive as a high-capacity anode for sodium-ion batteries, but undergoes structural degradation and instability of the solid-electrolyte interphase caused by the large volume change during cycling. Here, we demonstrate a unique Sb-based composite anode by embedding the Sb nanoparticles into the conductive hierarchical porous graphitic carbon (HPGC) that leaves enough room for volume change and is further encapsulated by a uniform conductive nitrogen-doped carbon (NC) layer to act as an electrolyte barrier. Such a design enables the [email protected]/NC composite to exhibit a high capacity of 639 mAh g−1, stable cycling stability, and a commercial-level areal capacity of 3.11 mAh cm−2. In addition, full cells by coupling with sodium vanadium phosphate cathode deliver a high energy density of 223.4 Wh kg−1 with superior rate performance. This work provides a bright way for the rational design and construction of Sb-based anode materials for advanced SIBs.

Sodium-ion batteries: Chemistry of biomass derived disordered carbon in carbonate and ether-based electrolytes

Lightweight and low temperature processing carbon material as an anode are of attraction in upcoming sodium battery technology. Biomass is a natural resource and converting them to hard carbons (HC) is well known for their application as anode material. It favour's the cost and performance proposition in battery technology, however, suffers many fundamental problems like irreversible loss of sodium-ions in the first cycle, long-life stabilization, and quantification of defects on the carbon and electrochemical property correlation, etc. Many such factors are notably dependent on the electrolyte used, defects in hard carbons, so in consideration of that, the focus of our research is to spotlight this by studying the electrochemistry of biomass-derived carbon anode in two different electrolyte solvent systems namely, Carbonate-based(CB) and Ether-based(EB) electrolytes. The results obtained here suggest that the EB electrolyte is more efficient compared to the CB electrolyte and that the creation of a thin and homogenous SEI layer increased reversibility and storage performance. Further, a full-cell has been fabricated using our biomass-derived carbon anode against a known [Na 3 V 2 (PO 4 ) 3 (NVP)] sodium vanadium phosphate in the role of cathode with the optimized EB as an electrolyte and electrochemical performance has also been documented. SEI growth on the electrode surface has a big impact on cell performance and life. When comparing the performance of cells cycled in CB electrolyte and EB electrolyte, the latter showed promising results. The reason for the improved performance was examined, and two main reasons were found: unifrom SEI formation and reduced thickness of SEI formed on the electrode surface.

Sodium vanadium oxides: From nanostructured design to high-performance energy storage materials

· Be the first to have an overview of NVO materials family, which is a promising materials category for energy storage systems. · Summarize with an insight into crystal structures, morphologies, mechanisms and the electrochemical energy storage performances. · Discuss the electrochemical behaviors, which provide further insight into metal-ion storage mechanisms in NVO materials family. Developing high-capacity and low-cost cathode materials for metal-ion rechargeable batteries is the mainstream trend and is also the key to providing breakthroughs in making high-energy rechargeable batteries. Vanadium has a variety of valence states and can form a variety of vanadate structures. As a typical positive electrode material, vanadate has abundant ion adsorption sites, a unique “pillar” framework, and a typical layered structure. Therefore, it has the advantages of high specific capacity and excellent rate performance, possessing the prospect of being a large-capacity energy storage material. In this review, we focus on applications of sodium vanadium oxides (NVO) in electrical energy storage (EES) devices and summarize sodium vanadate materials from three aspects, including crystal structure, electrochemical performance, and energy storage mechanism. The recent progress of NVO-based high-performance energy storage materials along with nanostructured design strategies was provided and discussed as well. This review is intended to serve as general guidance for researchers to develop desirable sodium vanadate materials.

Sodium vanadate microflowers as cathode for high-capacity and long-life aqueous zinc-ion battery

Aqueous zinc-ion batteries (ZIBs) have become increasingly popular in energy storage devices on account of their high safety, low cost, high theoretical specific capacity and low redox potential. However, the practical application of ZIBs has been hindered by cathode materials that usually exhibit low capacity or poor cycling performance. In our work, sodium vanadium oxide (NaV8O20) microflowers with nanosheet structure were prepared by hydrothermal method. As cathode materials of ZIBs, NaV8O20 microflowers deliver a high initial specific capacity of 427.6 mAh g−1 at 0.1 A g−1. Surprisingly, the capacity retention rate is about 77% after 7000 cycles at a high current density of 15 A g−1. These excellent electrochemical performances can be attributed to the pre-intercalation of Na+ ions to enhance the electrode stability and the nanosheet structure to increase the number of active sites, indicating that the aqueous ZIBs based on NaV8O20 microflowers has potential application value for large-scale energy storage.

Artificial Organo-Fluoro-Rich Anode Electrolyte Interface and Partially Sodiated Hard Carbon Anode for Improved Cycle Life and Practical Sodium-Ion Batteries.

In this work, a strategy is introduced wherein without keeping any excess cathode, a practical full-cell sodium-ion battery has been demonstrated by utilizing a hard carbon (HC) anode and sodium vanadium fluorophosphate and carbon nanotube composite (NVPF@C@CNT) cathode. A thin, robust, and durable solid electrolyte interface (SEI) is created on the surface of HC through its incubation wetted with a fluoroethylene carbonate (FEC)-rich warm electrolyte in direct contact with Na metal. During the incubation, the HC anode is partially sodiated and passivated with a thin SEI layer. The sodium-ion full cell fabricated while maintaining N/P ∼1.1 showed the first cycle Coulombic efficiency of ∼97% and delivered a stable areal capacity of 1.4 mAh cm-2 at a current rate of 0.1 mA cm-2 realized for the first time to the best of our knowledge. The full cell also showed a good rate capability, retaining 1.18 mAh cm-2 of its initial capacity even at a high current rate of 0.5 mA cm-2, and excellent cycling stability, giving a capacity of ∼1.0 mAh cm-2 after 500 cycles. The current strategy presents a practical way to make a sodium-ion full cell, utilizing no excess cathode material, significantly saving cost and time.

(Invited) Potentiometric Entropy and Operando Calorimetric Measurements to Assess the Performance of Heterogeneous Lithium Ion Battery Electrodes

This talk presents new efforts to use potentiometric entropy and operando isothermal calorimetric measurements to gain insight into the charging mechanisms as well as the thermodynamics and ion transport in lithium ion battery electrodes. Electrodes consisted of particles of different sizes - from a few nanometers to a few microns - synthesized by solid state or sol gel methods and using different conducting polymer binders. Promising battery materials such as lithium sodium vanadium fluorophosphate LixNa1.5-xVOPO4F0.5, tungsten vanadium oxide (W0.2V0.8)3O7, and titanium niobium oxide Ti2Nb2O9 were considered. The effect of particle size and binder on the specific capacity, polarization, thermodynamic behavior, and lithium transport were investigated. Particular attention was paid to various phenomena occurring during charging/discharging including solid solution intercalation, phase transition, and two phase coexistence region. Finally, the heat generation rates associated with (i) Joule heating cause be polarization, (ii) heat of mixing due to ion concentration gradient, and (iii) reversible entropy changes observed at different C-rates were identified and discussed.

Sodium vanadium hexacyanoferrate as a high-rate capability and long-life cathode material for Na-ion batteries

Na-ion batteries have gradually begun to be commercialized due to their advantages of lower cost and wide source of raw materials, but more excellent electrochemical performance is required to compete with lithium-ion batteries. In this work, sodium vanadium hexacyanoferrate (NaVHCF) was designed and synthesized as a Na-ion cathode material to exhibit excellent electrochemical performance. The results show that the capacity retention rate of 1000 cycles at 2.5C rate is 72 %, the Coulombic efficiency is 100 %, and the capacity retention rate of 5000 cycles at 25C high rate is 65 %. After activating at a low current density of 2.5C, it still has a capacity of 42 mAh g−1 after 2000 cycles at a high rate of 25C, and the capacity retention rate is 92 %. The analysis shows that the excellent rate and long cycling ability are related to the three-dimensional open structure and microporous structure of NaVHCF. During the long cycle, the diffusion coefficient of sodium ions gradually increases and the charge transfer resistance gradually decreases, which improves the battery lifespan. These results suggest that sodium-ion batteries are one step closer to commercial application.

Carbon-coated sodium vanadium phosphate for high-performance sodium-ion batteries

Room temperature sodium ion batteries are feasible for large energy storage equipment because they are both safe and inexpensive. However, the low electronic conductivity of sodium ion battery cathode material is an inherent flaw. Here, the solid-phase carbothermal reduction method was used to create Na3V2(PO4)3/C composites coated with four different carbon sources (Vc, maltose, sucrose, and PEG-2000). XRD and SEM were used to examine the crystal structure and microstructure; the electrochemical properties of four samples were examined using a constant current charge discharge test and AC impedance spectroscopy. As a result, the samples coated with PEG-2000 were identified to have an excellent microstructure and good electrochemical properties. Specifically, the discharge capacity decays from 103.9 mAh/g to 93.4 mAh/g after 340 cycles, and the corresponding capacity retention rate is 89.89%. Moreover, the outstanding electrochemical performance of Na3V2(PO4)3/C composites demonstrates that it is a promising material for the practical application of sodium-ion batteries.

Optimizing quasi-solid-state sodium storage performance of Na3V2(PO4)2F2.5O0.5 cathode by structural design plus nitrogen doping

Sodium vanadium fluorophosphate has been extensively explored for the cathode of sodium ion batteries (SIBs), which is known for its high voltage platform, three-dimensional framework structure and minor volume deformation. However, low intrinsic electronic conductivity restricts its practical charge/discharge performances. Accelerating the electron/ion transport process of sodium vanadium fluorophosphate is the vital point to realize high performances of SIBs. Herein, a well-designed nitrogen doped three-dimensional (3D) nanosheet flower-like Na3V2(PO4)2F2.5O0.5 composite (N-NVPFO) is proposed by optimizing nanostructure plus heteroatom doping. The 3D flower-like structure of N-NVPFO provides a great deal of active sites and guarantees the structure stability. In addition, the N-doping in Na3V2(PO4)2F2.5O0.5 bulk phase could enhance the intrinsic electronic conductivity by narrowing the energy gap, which is confirmed through the density functional theoretical (DFT) calculation. The N-NVPFO electrode delivers excellent rate capability (84 mAh g−1 at 10C) and long cycling life (86% capacity retention up to 2000 cycles). Furthermore, the quasi-solid-state SIBs using NaTi2(PO4)3 anode also exhibits good electrochemical performances.

Size and composition regulated sodium vanadium fluorophosphate wrapped in rGO as an efficient cathode for brackish and seawater desalination

The discovery of novel electrode materials with durable ion removal functionality for a designed capacitive deionization architecture is critical to enable seawater desalination. NASICON-based material, although having high theoretical capacity and fast sodium conductivity and thus a promising electrode material for sodium-ion removal, its desalination performance is limited by the poor electrical conductivity and aqueous electrolyte susceptibility. Herein, nano-sized sodium vanadium fluorophosphate Na3V2(PO4)2F3 at reduced graphene oxide (NVPF@rGO) is synthesized to improve electroconductivity and shorten the ion diffusion path, while fluorine content in its composition is regulated to lower the ions' diffusion barrier as a result of larger volume of the crystal. Moreover, the electrolyte concentration-controlled strategy is thoroughly investigated to minimize the dissolubility of the cathode over time. A proposed dual-ion electrochemical deionization system (DEDI) consisting of NVPF@rGO cathode and AgCl@rGO anode shows superior desalination stability in a highly concentrated synthetic seawater environment with ~98% capacity retention in over 500 cycles. Moreover, the salt removal capacity of 60 mg/g and desalination rate of 3.7 mg/g/min were achieved at a current density of 200 mA/g.