Lithium Trivanadate Research Articles

Enhancing symmetric supercapacitor performance through spin-coated lithium trivanadate films modified with carbon

Enhancing symmetric supercapacitor performance through spin-coated lithium trivanadate films modified with carbon

Effects of lithium content on the electrochemical performance of Li1+xV3O8 cathode materials for lithium-ion batteries

Lithium trivanadate (LiV3O8) is of great interest due to its large capacity, low cost and easy preparation. However, it still suffers from an inferior cyclability and rate capability. To solve these shortcomings of LiV3O8, a small extra amount of lithium was introduced into Li sites of LiV3O8. Herein, Li-doped LiV3O8 (Li1+xV3O8) materials were prepared and the electrochemical performance of Li1+xV3O8 changes with x from 0 to 0.1, 0.2 and 0.3. The discharge capacity of Li1+xV3O8 increases from x = 0 to 0.2 and then decreases, and the change trend of cycle performance is the same as that of discharge capacity. The optimal Li-doped LiV3O8 sample, Li1.2V3O8, exhibits much higher capacity and better cyclability and rate capability than LiV3O8. Galvanostatically discharged and charged between 2.0 and 4.0 V, Li1.2V3O8 and LiV3O8 present the initial discharge capacities of 305 and 268 mAh g−1 at 0.1 C (30 mA g−1), respectively, and the corresponding capacity retentions are 87% and 80% after 50 cycles. Even at a high current rate of 2 C, Li1.2V3O8 exhibits high discharge capacity of 173 mAh g−1, much higher than the discharge capacity of 133.6 mAh g−1 for LiV3O8. The better electrochemical performance of Li1.2V3O8 can be ascribed to the doping of appropriate amount of Li+ in LiV3O8 and the resulted higher diffusion coefficients of Li+ in Li1.2V3O8.

Lithium trivanadate thin films by polymer-assisted spin coating method for supercapacitor applications

Lithium trivanadate (LiV3O8) thin films were prepared by polymer assisted spin coating method. Here, the effect on addition of the polymers PVA, PVP, PEG and their combination on the preparation step were explored. The structural and morphological changes were analyzed by varying the substrate temperature, and its effect on the electrical and electrochemical performances were also studied. The thin films exhibited mixed micro and nanorod morphology. The XPS spectrum shows the stable 5+ oxidation state for vanadium. The electrochemical performance of the LiV3O8 thin film made using PVA:PVP and PVA:PEG in the 1:1 ratio outperformed the material made using PVA alone. The aqueous LiNO3 solution served as the electrolyte in three-electrode system. A specific capacitance of 359 F g−1 for a current density of 0.5 A g−1 as well as an areal capacitance of 143.8 F cm−2 at 0.2 mA cm−2 current density was obtained for the material made with PVA:PVP (1:1).

Preparation and characterization of lithium trivanadate thin films by spray pyrolysis method for supercapacitor applications

The lithium trivanadate (LiV3O8) thin films were deposited over stainless steel (SS) substrates by spray pyrolysis method. The material deposited at an optimized substrate temperature of 350°C and at an annealing temperature of 500°C (LV350_500/SS) performed better in electrochemical properties. The structural and surface morphological characteristics of the as deposited materials were determined using the X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM) analyses. The stable V5+ state was observed for the as-prepared LiV3O8 thin film in the X-ray photoelectron (XPS) spectrum. The electrochemical performance of the thin films were characterized using a three-electrode configuration with Ag/AgCl as the reference electrode, thin film material as the working electrode, and the platinum wire as the counter electrode. The 1 M LiNO3 aqueous solution was taken to be the electrolyte. LV350_500/SS made using a Li/V molar concentration of 0.1: 0.3 displayed an initial specific discharge capacitance value of 695 Fg−1 at a current density of 0.25 Ag−1, in the voltage range of -0.4 V to 0.4 V. But, the LV350_500/SS prepared using Li/V molar concentration of (0.05: 0.15) showed a low specific capacitance value of 181 Fg−1. A symmetric supercapacitor device made with the LV350_500/SS thin film as the electrodes and poly(vinylidene fluoride-co-hexafluoropropylene)/2D Graphene Oxide (PVdF-HFP/GO) composite polymer membrane as the electrolyte showed an excellent specific discharge capacitance value of 31 Fg−1 for a current density of 0.25 Ag−1. The calculated specific energy density and specific power density values were found to be 69 Whkg−1 and 1002 Wkg−1 respectively, for the above symmetric device.

Rheological Phase Reaction (RPR) as an Industrial Method for the Production of High Quality Metal Oxides towards Battery Applications

Although research on the preparation of metal oxides and other materials for various applications increases exponentially, it is more important to understand the need for eco-friendly methods of preparation to preserve the environment. Most of the methods available today are expensive, environmentally harmful, and inefficient with respect to mass production. The present review has explored the Rheological Phase Reaction (RPR) method, which has been extensively utilized as an eco-friendly industrial method for the preparation of metal oxides and metal oxide/carbon composite for lithium ion battery applications. Based on the literature reports, this review has two motivations: to identify the Rheological Phase Reaction (RPR) as the mass production method for preparing metal oxides, metal oxide/carbon composites, and other materials for different applications, to discuss the preparation steps involved, its advantages, the drawbacks associated; and to give a detailed review of the electrochemical performance of different metal oxides by the RPR method for application on the lithium ion battery, with particular emphasis on lithium trivanadate (LiV3O8).

Physics-based Models, Machine Learning, and Experiment: Towards Understanding Complex Electrode Degradation

Degradation phenomena in Li-ion batteries are highly complex, coupled, and sensitive to use history and operating conditions. In this study, we show how tracking model parameters in continuum-level physics-based models, expedited by machine learning, can be useful in testing hypotheses for degradation mechanisms. An exemplary analysis using this approach is presented for a set of lithium trivanadate () cathodes cycled over a range of current rates. A simple cell revival process is combined with the parameter estimates over the course of cycling to extract valuable insights into cathode evolution and eliminate hypothesized degradation mechanisms for these cathodes. The presented approach is expected to be broadly applicable for degradation analysis of other electrodes.

Parameter Estimation for Electrode Degradation: Learning in the Face of Model-Experiment Discrepancies

Use of physics-based models to interpret battery degradation data over the course of cycling can provide deeper physical insight into the internal states of the system and how they evolve. We present a neural network trained on simulations generated by a previously published physics-based model for a lithium trivanadate (LVO) cathode to estimate parameters that evolve over the course of cycling. We focus on the robustness of the neural network through two case studies that probe different kinds of discrepancies between model and experiment: nonideal data and imperfect model. In the former, the experimental protocols do not meet the assumption made in the training data generated by the physics-based model, while in the latter, the physics-based model fails to describe all of the measured cathode behavior even under ideal conditions. When there is total model-experiment agreement, a neural network estimates parameters with improved accuracy compared to a maximum likelihood analysis using the same set of simulations. However, in both types of model-experiment discrepancy, the neural network returned biased parameter estimates. We introduce a data augmentation procedure into the neural network training to mitigate these effects and improve robustness, and employ it to estimate parameters for a cycling LVO cathode.

Understanding Evolution of Lithium Trivanadate Cathodes During Cycling via Reformulated Physics-Based Models and Experiments

Degradation of lithium trivanadate (Li x V 3 O 8) cathodes has been widely reported in the literature, but studies have offered little insight towards developing a detailed understanding of the evolution of the active material, and have been inconclusive as to the root cause of degradation. Here, we refit a validated physics-based model to discharge curves over the course of cycling at C/5, and use the evolution of the model parameters to track evolution of the cathode. A regularization penalty for adjusting model parameters from the validated model is introduced as a framework to identify which model parameters can explain a significant portion of the observed change in the voltage profile over the course of cycling. SEM reveals that lithium trivandate particles fracture upon cycling at C/5, consistent with the results of the parameter estimation, deactivation of lithium trivanadate and faster diffusion of lithium within the active particles. The physics-based model is then used to design modified cycling protocols which identify the phase transformation during discharge of lithium trivanadate as the driver of the particle fracture and capacity fade.

Peering into Batteries: Electrochemical Insight Through In Situ and Operando Methods over Multiple Length Scales

Summary In order to overcome the limitations of static and destructive characterizations of Li-ion battery materials and components, comprehensive investigation peering into batteries over various length and time scales is essential. In this regard, emerging in situ and operando characterization methodologies focusing on multiple size domains become a powerful approach to resolve current challenges and navigate future directions. This perspective provides a series of illustrative examples of in situ and operando characterizations over atomic, crystallite/particle, electrode, and battery system length scales with a focus on two electrode material classes: insertion and conversion materials. The operating principles, features, analysis methods, and information gained from each characterization method are discussed. Herein, we present the necessity and opportunity for in situ and operando characterization of electrochemical energy storage materials and systems. Further, we suggest future directions to gain the insight needed to tackle currently intractable issues on Li-ion battery application, failure, and emerging design concepts.

Design Principles to Govern Electrode Fabrication for the Lithium Trivanadate Cathode

A full depth of discharge mathematical model for the lithium trivanadate cathode, considering lithiation of the layered α-phase, phase change, and lithiation of the rock-salt like β-phase at lower potentials, is developed. The coupled electrode-scale and crystal-scale model is fit to electrochemical data, and additionally validated with operando EDXRD. There is good agreement between the simulated and measured spatial variation of the volume fraction of the β-phase. This mathematical model is used to guide electrode fabrication, accounting for both ionic and electronic transport effects. Values of three design parameters—electrode thickness, porosity, and volume fraction of conductor—are identified, and the sensitivity of the energy density to these design parameters is quantified. The model is also used to investigate electrode design to create electrodes that deliver the maximum achievable energy density under the constraint that the α to β-phase transition is avoided, since phase change has been demonstrated to reduce cycle life. The energy density sacrificed to avoid phase change decreases at higher discharge rates, but the target values for electrode fabrication remain the same as those when optimizing the electrode for the full depth of discharge.

Structure and Electrochemistry of LiV3O8 Thin Film Electrode: Effect of Diffusion Rate and Concentration on Cell Polarization

Electrochemistry of lithium trivanadate (LiV3O8, LVO) has been extensively studied due to its large capacity and high rate capability. The material undergoes both insertion/extraction and phase transform reactions during discharge and charge in a Li-ion battery. However, the rate limiting factors of the material are unclear over the cycling window of 2.0 -3.8 V. In this work, LVO thin films are fabricated from RF magnetron sputtering and annealed at different temperatures of 260, 350, 400 and 500°C. Crystallinity, crystallite size and preferred orientation of the thin films are analyzed by x-ray diffraction. All solid-state thin film batteries are fabricated with LVO cathodes annealed at different temperatures of 260, 350 and 400°C. The electrochemical properties are investigated at two different test temperatures to compare the rate limiting process for discharge and charge. AC impedance is applied on the 260 and 350°C cells to characterize the voltage dependence of the diffusion coefficient during both discharge and charge. Our work correlates the cell polarization with both the diffusion coefficient and the Li+ concentration, showing that these parameters play different roles in the insertion and phase transform reactions, and shows the structural dependence of these parameters. Figure 1

Design and analysis of an optimal cathode for Li-LiV3O8 secondary cells

Lithium trivanadate (LiV3O8) and lithium vanadate (LiXV2O5) composites were synthesized by a solid-state method in order to obtain higher capacity and electrical conductivity. Two types of LiXV2O5 combined with LiV3O8 were obtained depending on the heating temperature. To determine the optimal ratio of the two materials, the cells assembled with these composites were cycled at a rate of 0.2C, and each component was analyzed by the Rietveld refinement. The LiV3O8/LiXV2O5 composites synthesized at 600 °C showed a higher discharge capacity and better capacity retention (259 mA h g−1 and 85%, respectively, after the 50th cycle) compared to those synthesized at other temperatures. The composites were characterized by thermogravimetric analysis, X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy, and particle size analysis. The electrochemical performance was analyzed using a battery testing system and impedance spectroscopy. The composites have increased intrinsic electrical conductivity with high lithium-ion coefficients, reduced electrochemical reaction resistance, and homogeneous particle size distributions with large surface areas. Therefore, the optimally synthesized composites are promising cathode materials for direct application in new battery systems using lithium.

Properties of Lithium Trivanadate Film Electrodes Formed on Garnet-Type Oxide Solid Electrolyte by Aerosol Deposition.

We fabricated lithium trivanadate LiV3O8 (LVO) film electrodes for the first time on a garnet-type Ta-doped Li7La3Zr2O12 (LLZT) solid electrolyte using the aerosol deposition (AD) method. Ball-milled LVO powder with sizes in the range of 0.5–2 µm was used as a raw material for LVO film fabrication via impact consolidation at room temperature. LVO film (thickness = 5 µm) formed by AD has a dense structure composed of deformed and fractured LVO particles and pores were not observed at the LVO/LLZT interface. For electrochemical characterization of LVO film electrodes, lithium (Li) metal foil was attached on the other end face of a LLZT pellet to comprise a LVO/LLZT/Li all-solid-state cell. From impedance measurements, the charge transfer resistance at the LVO/LLZT interface is estimated to be around 103 Ω cm2 at room temperature, which is much higher than at the Li/LLZT interface. Reversible charge and discharge reactions in the LVO/LLZT/Li cell were demonstrated and the specific capacities were 100 and 290 mAh g−1 at 50 and 100 °C. Good cycling stability of electrode reaction indicates strong adhesion between the LVO film electrode formed via impact consolidation and LLZT.

Operando Study of the LiV3O8 Cathode: Coupling Electrochemical and EDXRD Measurements with Mathematical Models

Building upon a previously validated crystal-scale model, a coupled electrode/crystal-scale mathematical model is used to compare phase-change behavior and electrochemical performance of lithium trivanadate (LiV3O8). The agreement between simulated and observed electrochemical performance is compelling. Observations about the phase-change dynamics of the material were gathered using time and space-resolved operando EDXRD measurements. These observations were compared with simulated concentration and phase profiles. Both simulation and experiment reveal that during lithiation, phase transformations preferentially occur near the separator, while during delithiation the disappearance of the lithium-rich β-phase occurs uniformly across the electrode.

Impact of Electrical Conductivity on the Electrochemical Performances of Layered Structure Lithium Trivanadate (LiV3-x M x O8, M= Zn/Co/Fe/Sn/Ti/Zr/Nb/Mo, x = 0.01-0.1) as Cathode Materials for Energy Storage.

Pristine trivanadate (LiV3O8) and doped lithium trivanadate (LiV3–xMxO8, M = Zn/Co/Fe/Sn/Ti/Zr/Nb/Mo, x = 0.01/0.05/0.1 M) compounds were prepared by a simple reflux method in the presence of the polymer, Pluronic P123, as the chelating agent. For comparison, pristine LiV3O8 alone was also prepared in the absence of the chelating agent. The Rietveld-refined X-ray diffraction patterns shows all compounds to exist in the layered monoclinic LiV3O8 phase belonging to the space group of P21/m. Scanning electron microscopy analysis shows the particles to exhibit layers of submicron-sized particles. The electrochemical performances of the coin cells were compared at a current density of 30 mA/g in the voltage window of 2–4 V. The cells made with compounds LiV2.99Zr0.01O8 and LiV2.95Sn0.05O8 show a high discharge capacity of 245 ± 5 mA h/g, with an excellent stability of 98% at the end of the 50th cycle. The second cycle discharge capacity of 398 mA h/g was obtained for the compound LiV2.99Fe0.01O8, and its capacity retention was found to be 58% after 50 cycles. The electrochemical performances of the cells were correlated with the electrical properties and the changes in the structural parameters of the compounds.

Operando Study of LiV3O8 Cathode: Coupling EDXRD Measurements to Simulations

The electrochemical and phase-change behavior of lithium trivanadate during lithiation and delithiation is analyzed by comparing a coupled electrode/crystal-scale mathematical model to operando experiments. The model expands on a previously published crystal-scale model by adding descriptions for electrode-scale resistances. Agreement between simulated and observed electrochemical measurements is compelling. Time and space-resolved operando EDXRD measurements on the cathode are compared with simulated concentration profiles. Both simulation and experiment reveal that during lithiation, phase transformations preferentially occur near the separator, while during delithiation the disappearance of the lithium-rich β-phase occurs uniformly across the electrode.

Improving the Electrochemical Performance of Lithium Metal Batteries with Hollow Shell Microspheres and Polypyrrole Vapor Phase-Coated LiV3O8 Cathodes

New hollow shell structured lithium trivanadate (LiV3O8) microspheres were synthesized by a spray drying method, and the effect of a vapor-phase-polypyrrole coating on the surface of this active material was studied. A thin and uniform coating layer could form by a simple vapor-phase-polymerization (VPP) method. The polypyrrole coating layer not only compensates for the low conductivity of the active material but also prevents its direct contact with the electrolyte and reduces vanadium dissolution. The LiV3O8 morphology and presence of the coating layer were confirmed using Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and transmission electron microscopy. The electrochemical performance was analyzed using a battery testing system and impedance spectroscopy. The cycle performance of the Li-powder/polypyrrole-VPP-coated hollow shell LiV3O8 cell showed a higher capacity and greater capacity retention (LiV3O8: 160.80 mA h g−1, 62.31%; coated LiV3O8: 206.55 mA h g−1, 82.02%) in the range of 1.8–4.0 V at a 0.2 C-rate, even after 200 cycles. The rate capability at various current densities was also high. Further, it had a low charge transfer resistance, which remained low even after many cycles. Thus, the combined effect of hollow-shell-structure and polypyrrole-VPP coating, led LiV3O8 to its improved electrochemical performance.

Electrochemical Properties of Li Metal Batteries with P(PEGMA)-Coated Lithium Trivanadate Cathode and Li Powder Anode

Electrochemical Properties of Li Metal Batteries with P(PEGMA)-Coated Lithium Trivanadate Cathode and Li Powder Anode

Interest in broadband dielectric spectroscopy to study the electronic transport in materials for lithium batteries

Broadband dielectric spectroscopy (BDS) is used to measure complex permittivity and conductivity of conducting materials for lithium batteries at frequencies from a few Hz to several GHz with network and impedance analysers. Under the influence of an electric field, there will be charge density fluctuations in the conductor mainly due to electronic transfer. These fluctuations result in dielectric relaxations for frequencies below 100GHz. The materials are compacted powders in which each element (particles, agglomerates of particles) can have different sizes and morphologies. In the present review, studies are reported on the influence of surface states in LiNiO2 (ageing and degradation in air) and LiFePO4 (carbon coating thin layer), and on a composite electrode based on the lithium trivanadate (Li1.1V3O8) active material. The results have shown that the BDS technique is very sensitive to the different scales of materials architectures involved in electronic transport, from interatomic distances to macroscopic sizes.

Studies on Capacity Fading of Lvo Cathode for Li-Metal Batteries

Lithium Trivanadate(LVO) cathode has a theoretically high specific capacity of 280 mAh/g, which one of higher energy capacity batteries than commercial LCO battery. However, Li-LVO batteries have problems resulting from the vanadium dissolution into the electrolyte, volumetric extension of LVO. We are planning an experiment to clear relationship between vanadium dissolution and volumetric extension in charge/discharge process. To analyze the main reason of LVO fading, Lithiation amount was different during cell test. Cells were tested at the current densities of 0.2 C-rate and 2 C-rate with 1.8V to 4.0V. And we were a time cut in cell test to control the lithiation amount. The interfacial characteristics and electrolyte after cycles were examined by SEM, EDS, ICP-mass and FT-IR. The results surely confirm that main reason of LVO fading between vanadium dissolution and volumetric extension.