Guangxi Colleges and Universities Key Laboratory of Novel Energy Materials and Related Technology

Nanning, China

Guangxi Colleges and Universities Key Laboratory of Novel Energy Materials and Related Technology

Nanning, China
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Wu Z.,Guangxi University | Long Y.F.,Guangxi University | Long Y.F.,Guangxi Colleges and Universities Key Laboratory of Novel Energy Materials and Related Technology | Lv X.Y.,Guangxi University | And 4 more authors.
Ceramics International | Year: 2017

Orthorhombic structure LiMnPO4/C with space group Pnmb was synthesized using a microwave heating process in a chloride/ethylene glycol-based deep eutectic solvent (DES) at 130°C for 30min under atmospheric pressure. The prepared sample was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and electrochemical tests. LiMnPO4/C prepared in a DES has a nano-spindle form coated with a carbon layer (approximately 3nm thick). This spindle-like LiMnPO4/C material delivers a discharge capacity of 129mAhg-1 with a capacity retention ratio of approximately 96.1% after 100 cycles at 1C. Even at 5C, it still gives a discharge capacity of 106mAhg-1, exhibiting good rate performance and cycle stability. The results of this work show that the chloride/ethylene glycol-based DES can act as a crystal-face inhibitor to adjust the oriented growth and morphology of LiMnPO4. Furthermore, deep eutectic solvents could find a wide application in the synthesis of electrode materials with special morphologies for lithium ion batteries. © 2017 Elsevier Ltd and Techna Group S.r.l.


Long Y.,Guangxi University | Long Y.,Guangxi Colleges and Universities Key Laboratory of Novel Energy Materials and Related Technology | Zhang Z.,Guangxi University | Wu Z.,Guangxi University | And 5 more authors.
Particuology | Year: 2017

We synthesized LiMnPO4/C with an ordered olivine structure by using a microwave-assisted polyol process in 2:15 (v/v) water-diethylene glycol mixed solvents at 130°C for 30min. We also studied how three surfactants-hexadecyltrimethylammonium bromide, polyvinylpyrrolidone k30 (PVPk30), and polyvinylpyrrolidone k90 (PVPk90)-affected the structure, morphology, and performance of the prepared samples, characterizing them by using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, charge/discharge tests, and electrochemical impedance spectroscopy. All the samples prepared with or without surfactant had orthorhombic structures with the Pnmb space group. Surfactant molecules may have acted as crystal-face inhibitors to adjust the oriented growth, morphology, and particle size of LiMnPO4. The microwave effects could accelerate the reaction and nucleation rates of LiMnPO4 at a lower reaction temperature. The LiMnPO4/C sample prepared with PVPk30 exhibited a flaky structure coated with a carbon layer (∼2nm thick), and it delivered a discharge capacity of 126mAh/g with a capacity retention ratio of ∼99.9% after 50 cycles at 1C. Even at 5C, this sample still had a high discharge capacity of 110mAh/g, demonstrating good rate performance and cycle performance. The improved performance of LiMnPO4 likely came from its nanoflake structure and the thin carbon layer coating its LiMnPO4 particles. Compared with the conventional polyol method, the microwave-assisted polyol method had a much lower reaction time. © 2017 Chinese Society of Particuology and Institute of Process Engineering, Chinese Academy of Sciences.


Wu Z.,Guangxi University | Huang R.-R.,Guangxi University | Yu H.,Guangxi University | Xie Y.-C.,Guangxi University | And 7 more authors.
Materials | Year: 2017

Olivine-type LiMnPO4/C nanorods were successfully synthesized in a chloride/ethylene glycol-based deep eutectic solvent (DES) at 130 °C for 4 h under atmospheric pressure. As-synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, Fourier transform infrared spectroscopy (FTIR) and electrochemical tests. The prepared LiMnPO4/C nanorods were coated with a thin carbon layer (approximately 3 nm thick) on the surface and had a length of 100-150 nm and a diameter of 40-55 nm. The prepared rod-like LiMnPO4/C delivered a discharge capacity of 128 mAh·g-1 with a capacity retention ratio of approximately 93% after 100 cycles at 1 C. Even at 5 C, it still had a discharge capacity of 106 mAh·g-1, thus exhibiting good rate performance and cycle stability. These results demonstrate that the chloride/ethylene glycol-based deep eutectic solvents (DES) can act as a new crystal-face inhibitor to adjust the oriented growth and morphology of LiMnPO4. Furthermore, deep eutectic solvents provide a new approach in which to control the size and morphology of the particles, which has a wide application in the synthesis of electrode materials with special morphology. © 2017 by the authors.


Lv X.-Y.,Guangxi University | Huang Q.-Y.,Guangxi University | Wu Z.,Guangxi University | Su J.,Guangxi University | And 5 more authors.
Journal of Solid State Electrochemistry | Year: 2017

Li0.995Nb0.005Mn0.85Fe0.15PO4/C was prepared and characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), and electrochemical tests. The results of XRD and XPS show that Nb5+ and Fe2+ are introduced into the lattice of LiMnPO4 to form solid solution and generate a synergistic effect on the shrinkage of lattice and the formation of metal ion-vacancy pairs. When charged/discharged at 1 C, Li0.995Nb0.005Mn0.85Fe0.15PO4/C delivers a discharge capacity of 146 and 161 mAh g−1 with a capacity retention ratio of ∼100 % after 50 cycles at 25 and 60 °C, respectively. Even charged/discharged at 5 C, this sample still gives a discharge capacity of 100 mAh g−1, exhibiting good rate capability and cycling stability. The improved electrochemical performance can be ascribed to the synergistic effect between Nb5+ and Fe2+, which significantly enhances the dynamic stability of the olivine structure, Li+ diffusion, and electrochemical kinetics. These results further prove that the electrochemical properties of lithium manganese phosphate can be effectively enhanced by Fe2+ and Nb5+ co-doping. © 2017 Springer-Verlag Berlin Heidelberg


Liu Z.,Guangxi University | Huang Q.,Guangxi University | Yao H.,Guangxi University | Su J.,Guangxi University | And 7 more authors.
Gongneng Cailiao/Journal of Functional Materials | Year: 2016

LiMnPO4/C composites were prepared by a microwave solvothermal method using MnSO4·H2O and Li3PO4 precursor as source materials, water and diethylene glycol mixed solvents as reaction solvents. The effects of temperature on the structure and electrochemical performances of samples were investigated by XRD, SEM, CV, EIS charge/discharge tests. As the temperature increased, block like Li3PO4 precursor gradually transformed into a flaky LiMnPO4. The sample prepared at 190℃ formed the olivine structure with the space group Pmnb. The prepared LiMnPO4/C delivered an initial discharge capacity of 108.3 mAh/g with a capacity retention of 99.9% after 50 cycles at 1 C. © 2016, Chongqing Functional Materials Periodical Press Co. Ltd. All right reserved.


Li Y.-N.,Guangxi University | Su J.,Guangxi University | Su J.,Guangxi Colleges and Universities Key Laboratory of Novel Energy Materials and Related Technology | Lv X.-Y.,Guangxi University | And 7 more authors.
Ceramics International | Year: 2017

To improve the performance of anatase TiO2 as an anode material for sodium-ion batteries, Zn2+-doped TiO2/C composites are synthesized by a co-precipitation method. The results of XRD, EPR and XPS demonstrate that Zn2+ occupies at the Ti4+ site of TiO2 to form a solid-solution, resulting in an expansion of lattice and an increase of Ti3+ content. The expansion of lattice can enhance the stability of the crystal structure of TiO2. The increase of Ti3+ content can improve the conductivity of TiO2. Therefore, Ti0.94Zn0.06O2/C delivers a reversible capacity of 160mAhg-1 with a capacity retention of 96% after 100 cycles at 5C. Even charged/discharged at 10C, this sample still exhibits a reversible capacity of 117mAhg-1, comparing to 86mAhg-1 for TiO2/C. The enhanced electrochemical performances can be ascribed to the improvement of the conductivity and the structural stability of TiO2 due to Zn2+-doping. Therefore, Ti0.94Zn0.06O2/C is an attractive anode material of sodium-ion batteries. © 2017 Elsevier Ltd and Techna Group S.r.l.


Li Y.-N.,Guangxi University | Su J.,Guangxi University | Su J.,Guangxi Colleges and Universities Key Laboratory of Novel Energy Materials and Related Technology | Lv X.-Y.,Guangxi University | And 5 more authors.
Electrochimica Acta | Year: 2015

Porous anatase TiO2 samples have been prepared by a bio-template route using low-cost yeast cells as templates. The structure, morphology and electrochemical performance of the prepared samples have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) analysis, galvanostatic charge/discharge tests and cyclic voltammograms (CV). The results showed that the prepared samples have a hierarchical porous structure replicated from the microstructure of yeast template, which combines macropores (1.5-2.5 μm) and thin pore wall (0.2-0.7 μm) composed by mesopore (9.78 nm) and 10-20 nm active material. The prepared porous TiO2 delivered a discharge capacity of about 255.98 mAh g-1 and its capacity retention was about 80% after 100 cycles at 1/3C. Remarkably, it still showed a high discharge capacity of 112.93 and 84.65 mAh g-1 even at 5 and 10C, respectively. The good rate performance can be ascribed to the hierarchical porous structure, which provided good access of the electrolyte to the electrode interface, reducing path lengths for ion diffusion and accommodating volume changes during cycling. © 2015 Elsevier Ltd. All rights reserved.


Su J.,Guangxi University | Su J.,Guangxi Colleges and Universities Key Laboratory of Novel Energy Materials and Related Technology | Liu Z.-Z.,Guangxi University | Long Y.-F.,Guangxi University | And 6 more authors.
Electrochimica Acta | Year: 2015

An LiMnPO4/C composite material with ordered olivine structure was synthesized by a microwave-assisted solvothermal process in 2:5 (v/v) water-diethylene glycol mixed solvents at 190 °C for 5 min. The sample was characterized by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy, charge/discharge tests, cyclic voltammetry, and electrochemical impedance spectroscopy. The prepared LiMnPO4/C particles exhibited an irregular flaky form coated with a uniform carbon layer (approximately 2-3 nm thick). The prepared LiMnPO4/C composite exhibited a discharge capacity of 131.4 and 85.2 mAh·g-1 at 0.1C and 5C, respectively. It delivered a discharge capacity of 109.2 mAh·g-1 with a capacity retention ratio of approximately 99% after 50 cycles at 1C. Furthermore, this microwave-assisted solvothermal approach led to a significant decrease in the reaction time as compared to conventional hydrothermal/ solvothermal processes. © 2015 Elsevier Ltd. All rights reserved.

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