Search results for: Jiequn Liu

Items from 1 to 20 out of 20 results

article

The electrochemical properties of nano-LiFeBO₃/C as cathode materials for Li-ion batteries

Wei Chen, Ling Wu, Xiaoping Zhang, Jiequn Liu, more

Journal of Solid State Electrochemistry > 2018 > 22 > 6 > 1677-1687

Carbon-coated LiFeBO₃ is prepared by sol-gel method, and polyethylene glycol 6000 (PEG-6000) is chosen as carbon source. Compared with conventional solid-state method, the LiFeBO₃/C nano-particles were obtained at a relatively lower temperature (500 °C). It was demonstrated that the prepared LiFeBO₃ is a highly pure monoclinic structure with space group of C2/c, the primary particle size of the carbon-coated...

article

Synthesis and electrochemical performance of carbon-coated LiCoBO₃ as cathode materials for lithium-ion batteries

Wei Chen, Jiequn Liu, Xiaoping Zhang, Shijun Liu, more

Ionics > 2018 > 24 > 6 > 1571-1577

Carbon-coated LiCoBO₃ (LiCoBO₃/C) is prepared by sol-gel method and polyethylene glycol 6000 (PEG-6000) is chosen as carbon source. The LiCoBO₃/C sample exhibits an initial discharge capacity of 76.7 mAh g⁻¹ at 0.1 C, and it can deliver a discharge capacity of 65.9 mAh g⁻¹ after 50 cycles, while the LiCoBO₃ sample only presents a first discharge capacity of 34.3 and 16.8 mAh g⁻¹ at the 50th cycle,...

article

High performance of hexagonal plates P2-Na2/3Fe1/2Mn1/2O2 cathode material synthesized by an improved solid-state method

Jiabin Chen, Shengkui Zhong, Xiaoping Zhang, Jiequn Liu, more

Materials Letters > 2017 > 202 > C > 21-24

P2-type Na_2/3Fe_1/2Mn_1/2O₂ cathode material is synthesized by a modified solid-state method with organic metal salts as raw materials, which can reduce the temperature and time of heat treatment, and highly enhance the electrochemical performance. XRD results indicate that the sample is a pure P2-type Na_2/3Fe_1/2Mn_1/2O₂ phase with well-developed crystal structure. Furthermore, a regular hexagon plate...

article

Na3V2(PO4)3/C cathode material synthesized by normal temperature chemical reduction and sodiation method

Shaonan Shi, Ling Wu, Yong Hu, Jiabin Chen, more

Materials Letters > 2017 > 198 > C > 128-131

Na₃V₂(PO₄)₃/C cathode material is synthesized through a novel normal temperature chemical reduction and sodiation method, by using oxalic acid as both a reducing agent and a carbon source. During the mechanical activation process, the color of raw materials changes from buff to green indicating that the pentavalent vanadium ion is reduced. The XRD results show that the amorphous precursor can be transformed...

article

Synthesis and electrochemical performance of carbon-coated LiMnBO₃ as cathode materials for lithium-ion batteries

Wei Chen, Hua Zhang, Xiaoping Zhang, Ling Wu, more

Ionics > 2018 > 24 > 1 > 73-81

Carbon-coated LiMnBO₃/C is synthesized by a sol-gel method using polyethylene glycol 6000 (PEG-6000) as carbon source. The influences of different sintering temperatures on the crystal structure, morphology, and electrochemical performance of LiMnBO₃/C composites are investigated. XRD results indicate that the samples consist of the monoclinic phase LiMnBO₃ (m-LiMnBO₃) and the hexagonal phase LiMnBO...

article

Secure Transmission of Wireless Relaying Systems With Jammer and Multiple-User Selection

Yijun Yang, Jin Chen, Yuzhen Huang, Ximing Wang, more

IEEE Access > 2017 > 5 > 8771 - 8779

In this paper, we investigate the secure transmission of wireless relaying systems with multi-destinations and an eavesdropper (Eve) in Nakagami-

$m$

fading channels. To protect the confidential message from leaking to the Eve, an intentional interference is sent from a selected destination. We propose two jammer selection schemes under two typical communication scenarios: 1) the channel state information...

article

Synthesis of xLiVPO₄F·yLi₃V₂(PO₄)₃/C composite as a potential cathode material for Li-ion batteries

Shengkui Zhong, Wei Hong, Xiaoping Zhang, Jiequn Liu, more

Ionics > 2017 > 23 > 4 > 813-819

xLiVPO₄F·yLi₃V₂(PO₄)₃/C cathode materials are prepared by a two-step carbon coating method. XRD results show that all the xLiVPO₄F·yLi₃V₂(PO₄)₃/C composites (x:y ≠ 0) contain both LiVPO₄F and Li₃V₂(PO₄)₃ phases, and no impurities are detected. SEM results show that the average primary size of the composites is 0.3–1 μm. All the composites show less aggregation than the single LiVPO₄F/C and Li₃V₂(PO...

article

Novel synthesis of LiCoPO4–Li3V2(PO4)3 composite cathode material for Li-ion batteries

Ling Wu, Shaonan Shi, Xiaoping Zhang, Jiequn Liu, more

Materials Letters > 2015 > 152 > C > 228-231

LiCoPO₄–Li₃V₂(PO₄)₃ composite cathode material is synthesized by a chemical lithiation method, with Co₃V₂O₈ as the precursor and oxalic acid as the reductant. XRD result indicates that the composite is composed of olivine-type LiCoPO₄ and monoclinic Li₃V₂(PO₄)₃. TEM, HRTEM and FFT results show that the LiCoPO₄–Li₃V₂(PO₄)₃ particles are wrapped with nano-carbon webs, and the crystal particles contain...

article

Li3V2(PO4)3/C microspheres with high tap density and high performance synthesized by a two-step ball milling combined with the spray drying method

Ling Wu, Shengkui Zhong, Jiajia Lu, Fan Lv, more

Materials Letters > 2014 > 115 > Complete > 60-63

Li ₃ V ₂ (PO ₄ ) ₃ /C microspheres are synthesized by a two-step ball milling combined with spray drying method. XRD results reveal that the sample exhibits a single monoclinic Li ₃ V ₂ (PO ₄ ) ₃ phase, and no impurity phases are detected. SEM and TEM results indicate that the Li ₃ V ₂ (PO ₄ ) ₃ /C microspheres...

article

Improving the electrochemical performance of LiMnPO4/C by liquid nitrogen quenching

Ling Wu, Shengkui Zhong, Fan Lv, Jiequn Liu

Materials Letters > 2013 > 110 > Complete > 38-41

LiMnPO ₄ /C cathode material is prepared by a sol–gel combined ball milling and liquid nitrogen quenching method. XRD results reveal that quenching does not destroy the structure of LiMnPO ₄ . The quenched sample, which is well crystallized with a single olivine type LiMnPO ₄ phase, shows a slightly contracted lattice parameters of a, b and c compared with the un-quenched sample...

article

Synthesis of Cr-doped LiMnPO₄/C cathode materials by sol–gel combined ball milling method and its electrochemical properties

Ling Wu, Shengkui Zhong, Jiajia Lu, Jiequn Liu, more

Ionics > 2013 > 19 > 7 > 1061-1065

LiMn_1-xCr_xPO₄/C (x = 0, 0.01, 0.03, and 0.05) compounds are synthesized by a sol–gel combined ball milling method. The effects of Cr doping on the structure, morphology, and electrochemical performance of LiMnPO₄ are investigated. XRD analysis results indicate that all the samples exhibit the single LiMnPO₄ phase and Cr ions substitute on Mn site (x ≤ 0.03), with charge compensating vacancies on...

article

Preparation of high tap-density 9LiFePO4·Li3V2(PO4)3/C composite cathode material by spray drying and post-calcining method

Shengkui Zhong, Ling Wu, Junchao Zheng, Jiequn Liu

Powder Technology > 2012 > 219 > Complete > 45-48

The 9LiFePO ₄ ·Li ₃ V ₂ (PO ₄ ) ₃ /C composite cathode material is synthesized by spray-drying and post-calcining method based on citrate. The composite is well crystallized, and contains olivine-type LiFePO ₄ and monoclinic Li ₃ V ₂ (PO ₄ ) ₃ phases. The composite material exhibits spherical particles in the size of 0...

article

A PEG-assisted rheological phase reaction synthesis of 5LiFePO₄⋅Li₃V₂(PO₄)₃/C as cathode material for lithium ion cells

Shengkui Zhong, Wei Chen, Ling Wu, Jiequn Liu

Ionics > 2012 > 18 > 5 > 523-527

5LiFePO₄⋅Li₃V₂(PO₄)₃/C composite cathode material is synthesized by a polyethylene glycol (PEG)-assisted rheological phase method. As a surfactant and dispersing agent, PEG can effectively inhabit the aggregation of colloidal particles during the formation of the gel. Meanwhile, PEG will coat on the particles to play the role of carbon source during the sintering. The samples are characterized by...

article

Synthesis and electrochemical properties of Ce-doped LiNi1/3Mn1/3Co1/3O2 cathode material for Li-ion batteries

Shengkui ZHONG, You WANG, Jiequn LIU, Kang WAN, more

Journal of Rare Earths > 2011 > 29 > 9 > 891-895

The layered material of Ce-doped LiNi _1/3 Mn _1/3 Co _1/3 O ₂ with α-NaFeO ₂ was synthesized by a co-precipitation method. X-ray diffraction (XRD) showed that Ce-doped LiNi _1/3 Mn _1/3 Co _1/3 O ₂ had the same layered structure as the undoped LiNi _1/3 Mn _1/3 Co _1/3 O ₂ . The scanning electron microscopy...

article

Investigations on the synthesis and electrochemical performance of Li₃V₂(PO₄)₃/C by different methods

Shengkui Zhong, Jian Wang, Letong Liu, Jiequn Liu, more

Ionics > 2010 > 16 > 2 > 117-121

Li₃V₂(PO₄)₃/C samples were synthesized by two different synthesis methods. Their influence on electrochemical performances of Li₃V₂(PO₄)₃/C as cathode materials for lithium-ion batteries was investigated. The structure and morphology of Li₃V₂(PO₄)₃/C samples were characterized by X-ray diffraction and scanning electron microscopy. Electrochemical performance was characterized by charge/discharge,...

article

High-rate characteristic of F-substitution Li3V2(PO4)3 cathode materials for Li–ion batteries

Shengkui Zhong, Letong Liu, Jiequn Liu, Jian Wang, more

Solid State Communications > 2009 > 149 > 39-40 > 1679-1683

The effect of fluorine substitution on the electrochemical properties of Li ₃ V ₂ (PO ₄ ) ₃ cathode materials was studied. Samples with stoichiometric proportions of Li ₃ V ₂ (PO ₄ ) _3−x F _x (x=0,0.05,0.10,0.15) were prepared by adding LiF in the starting materials of Li ₃ V ₂ (PO ₄ ) ₃ . XRD studies...

article

A novel method to synthesize LiVPO4F/C composite materials and its electrochemical Li-intercalation performances

Qian Zhang, Shengkui Zhong, Letong Liu, Jiequn Liu, more

Journal of Physics and Chemistry of Solids > 2009 > 70 > 7 > 1080-1082

Triclinic LiVPO ₄ F/C composite materials were prepared from a sucrose-containing precursor by one-step heat treatment. As-prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical measurements. XRD studies showed that Li ₃ PO ₄ impurity phase appeared in the sample synthesized at 600°C and pure LiVPO ₄ ...

article

Preparation and electrochemical properties of Y-doped Li3V2(PO4)3 cathode materials for lithium batteries

Shengkui ZHONG, Letong LIU, Jiqiong JIANG, Yanwei LI, more

Journal of Rare Earths > 2009 > 27 > 1 > 134-137

Y-doped Li ₃ V ₂ (PO ₄ ) ₃ cathode materials were prepared by a carbothermal reduction(CTR) process. The properties of the Y-doped Li ₃ V ₂ (PO ₄ ) ₃ were investigated by X-ray diffraction (XRD) and electrochemical measurements. XRD studies showed that the Y-doped Li ₃ V ₂ (PO ₄ ) ₃ had the same monoclinic...

article

Synthesis and electrochemical properties of Cr-doped Li₃V₂(PO₄)₃ cathode materials for lithium-ion batteries

Shengkui Zhong, Bo Zhao, Yanhang Li, Yongpin Liu, more

Journal of Wuhan University of Technology-Mater. Sci. Ed. > 2009 > 24 > 3 > 343-346

Cr-doped Li₃V₂(PO₄)₃ cathode materials Li₃V_2−xCr_x(PO₄)₃ were prepared by a carbothermal reduction(CTR) process. The properties of the Cr-doped Li₃V₂(PO₄)₃ were investigated by X-ray diffraction (XRD), scanning electron microscopic (SEM), and electrochemical measurements. Results show that the Cr-doped Li₃V₂(PO₄)₃ has the same monoclinic structure as the undoped Li₃V₂(PO₄)₃, and the particle size...

article

Preparation and electrochemical studies of Y-doped LiVPO₄F cathode materials for lithium-ion batteries

Shengkui Zhong, Fengpeng Li, Jiequn Liu, Yanhong Li, more

Journal of Wuhan University of Technology-Mater. Sci. Ed. > 2009 > 24 > 4 > 552-556

Y-doped LiVPO₄F cathode materials were prepared by a carbothermal reduction(CTR) process. The properties of the Y-doped LiVPO₄F samples were investigated by X-ray diffraction (XRD) and electrochemical measurements. XRD studies show that the Y-doped LiVPO₄F samples have the same triclinic structure as the undoped LiVPO₄F. The Li extraction/insertion performances of Y-doped LiVPO₄F samples were investigated...

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