Electrochemical Properties Of Li3V2 Research Articles

Synthesis and Electrochemical Properties of Li3V2(PO4)3/Graphene Composites

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Rheological phase synthesis and characterization of Li3V2(PO4)3/C composites as cathode materials for lithium ion batteries

Li3V2(PO4)3/C composites as cathode materials for lithium ion batteries were successfully synthesized through the rheological phase reaction method using LiOH·H2O, V2O5, NH4H2PO4, and C6H8O7·H2O as raw materials. The as-prepared powders were characterized by means of powder X-ray diffraction (XRD), scan electron microscope (SEM), and transmission electron microscope (TEM). The electrochemical properties of Li3V2(PO4)3/C composites were examined by the galvanostatic charge/discharge, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The results indicate that the sintering temperatures have a significant effect on the crystal structure, morphology, and electrochemical performances of Li3V2(PO4)3/C composites. XRD reveals that Li3V2(PO4)3/C composites are well crystallized single phase, where Li3V2(PO4)3/C composite synthesized at 800°C for 8h displays the maximum cell volume and uniformly distributed particles. It can be seen from TEM that there is a carbon layer of about 200-500nm thick on the particle surface. The apparent DLi+ calculated from CV is in the order of magnitude of 10−7 cm2 s−1. Electrochemical tests show that Li3V2(PO4)3/C composite synthesized at 800°C for 8h exhibits excellent cycling performance of 129.149 mAh g−1 after 60 cycles at the current of 15mAg−1 and a superior rate capability of 112.101 mAh g−1 after 60 cycles at the current of 90mAg−1.

Effect of Amount of Water Dispersant on Morphological and Electrochemical Properties of Li3V2(PO4)3/C Prepared with Carbothermic Reduction Method

Li3V2(PO4)3/C (LVP/C) cathode materials were synthesized via a carbothermic reduction method at different solid/liquid ratios, where the solid stood for mass of raw materials (g) and liquid represented the volume of pure water (mL) that was used as the ballmilling dispersant. The crystalline phases and morphologies of the prepared samples were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The electrochemical properties were evaluated by electrochemical impedance spectroscopy (EIS) and galvanostatic charge/discharge tests. The results reveal that the Li3V2(PO4)3/C cathode material synthesized at a ballmilling solid/liquid (by mass/volume, g/mL) ratio of 3:10 exhibited an architecture of small LVP grains encapsulated by thick, uniform and interconnected carbon layers, which can enlarge the electrochemical reaction interface, enhance the electrical conductivity and favor the solid diffusion of lithium ions. Because of this unique morphology, this sample (with a solid/liquid ratio of 3:10) showed the best electrochemical performance (i.e. discharge capacities, cyclability, and low temperature performance) among samples prepared at different solid/liquid ratios (3:5, 3:10, and 3:15).

Synthesis and electrochemical properties of Li3V2(PO4)3/C cathode material with an improved sol–gel method by changing pH value

Abstract An improved sol–gel method by changing pH value is developed to synthesize high performance Li3V2(PO4)3/C cathode material. Li3V2(PO4)3/C powders are prepared by a conventional sol–gel process without special controlling pH value and the improved sol–gel process, respectively. They are characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), galvanostatic charge/discharge test, cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and potential step chronoamperometry (PSCA). Not only the cycle performance for the samples prepared by the improved sol–gel method shows obvious enhancement compared with that for the sample prepared via a conventional sol–gel process, but also initial specific capacities have been improved markedly. In the voltage range of 3.0–4.8 V, the sample prepared at pH value of 4 exhibits an optimum capability at low-rate. The sample prepared at pH value of 9 possesses a good performance at high-rate. The enhanced electrochemical performance can be attributed to the microstructure of the powders, which can make the lithium ion diffusion and electron transfer easier across the Li3V2(PO4)3/C interfaces, thus resulting in enhanced electrode reaction kinetics and improved electrochemical performance.

Effects of Sintering Temperatures on the Solid-Phase Synthesis of Lithium Vanadium Phosphate for Lithium-Ion Cathode Materials

Li3V2(PO4)3/C composite cathode material was prepared by carbothermal reduction using LiOHH2O, NH4H2PO4, NH4VO3 as raw material, sucrose as a coated carbon source, respectively. The electrochemical properties of Li3V2(PO4)3/C composite material prepared at different sintering temperature between 750°C and 900°C were investigated. The results demonstrated that by adjusting the sintering temperature, the electrochemical performance of the Li3V2(PO4)3/C material tends to be excellent, and when the temperature reaches 750°C, the Li3V2(PO4)3/C composite cathode material with the best electrochemical properties can be obtained.

Synthesis and electrochemical properties of Li3V2(PO4)3/C with one-dimensional (1D) nanorod structure for cathode materials of lithium-ion batteries

A series of Li3V2(PO4)3/C cathode materials with different morphologies were successfully prepared by controlling temperatures using maleic acid as carbon source via a simple sol–gel reaction method. The Li3V2(PO4)3/C nanorods synthesized at 700 °C with diameters of about 30–50 nm and lengths of about 800 nm show the highest initial discharge capacity of 179.8 and 154.6 mA h g−1 between 3.0 and 4.8 V at 0.1 and 0.5 C, respectively. Even at a discharge rate of 0.5 C over 50 cycles, the products still can deliver a discharge capacity of 140.2 mA h g−1 in the potential region of 3.0–4.8 V. The excellent electrochemical performance can be attributed to one-dimensional nanorod structure and uniform particle size distribution. All these results indicate that the resulting Li3V2(PO4)3/C is a very strong candidate to be a cathode in a next-generation Li-ion battery for electric-vehicle applications.

The effect of doping Mg2+ on the structure and electrochemical properties of Li3V2(PO4)3 cathode materials for lithium-ion batteries

The Mg-doped Li3V2−xMgx(PO4)3 (x=0.00, 0.01, 0.02, 0.05, 0.10, 0.20, 0.30, 0.33, 0.50, 1.00 and 1.33) compounds have been prepared by a sol–gel method in reducing atmosphere (70%Ar+30%H2) using citric acid as a chelating agent and a carbon source coated on the samples. The Mg-doped effects on the structural and electrochemical performance of Li3V2(PO4)3 are investigated by X-ray diffraction, galvanostatic, charge/discharge and four-point probe measurement method. The Li3V2−xMgx(PO4)3 solid solution phase can exist stable in the composition range between x=0.00 and 0.27. The simple improve mechanism of the electrochemical performance for Mg-doped Li3V2−xMgx(PO4)3 system is discussed too. In the Mg-doped Li3V2−xMgx(PO4)3 system, at a lower charge/discharge rate (0.1C), the cycle performance has no much improvement with the increasing Mg doping content. However, at higher rates, there has an excited improvement in both cycle performance and rate capability due to the increase of electrical conductivity (more than one order of magnitude). At 5C charge/discharge rate, for the Li3V1.95Mg0.05(PO4)3 sample, the discharge capacities for the 1st and 100th cycle were 138.9 and 123.3mAhg−1. The discharge capacity retention reached to 89% (more than 51% for undoped Li3V2(PO4)3 system). More important is that, except for the first 15 cycles, the discharge capacities kept almost a constant. Based on the excellent electrochemical performance, Li3V1.95Mg0.05(PO4)3 will be a promising cathode material for rechargeable lithium-ion batteries.

Synthesis and electrochemical properties of monoclinic Li3V2(PO4)3/C composite cathode material prepared from a sucrose-containing precursor

Monoclinic structure Li3V2(PO4)3/C composite powders are synthesized via a novel homogeneous mixing route followed by a one-step heat treatment. The composites were characterized by X-ray diffraction (XRD) and galvanostatic charge/discharge, CV measurements. The influence of the heat treatment on the electrochemical properties of Li3V2(PO4)3/C composites was investigated. To examine the effect of residual carbon content on the properties of the composites, six samples with 1.2, 2.3, 3.4, 4.4, 5.8, and 7.0 wt% carbon were prepared. The sample with 4.4 wt% carbon exhibited good cycling performance and rate capability in the range of 3.0–4.8 V.