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Lv B.,Henan Polytechnic University | Wang X.,Henan Polytechnic University | Wang X.,Huadong Institute of Lithium Ion Battery | Hu A.,Henan Polytechnic University
Journal of Computational and Theoretical Nanoscience | Year: 2016

Based on an analytical formula of the Tolman length, some estimations of the Tolman length were obtained. The Tolman length is non-negative. The Tolman length of the fluid is zero while isothermal compression rate of the fluid is zero. The Tolman length is divergent at the critical point. The curvature dependence of surface tensions of spherical droplets can be further gotten based on this analytical formula of the Tolman length. The surface tensions increase as the radii of spherical droplets increase. Two estimations of the Tolman length are obtained based on Egelstaff-Widom formula and Sanchez's equation. Based on the results of molecular dynamics simulations, it can be calculated that the value of dimensionless structure constant A of droplets consisted of argon molecular system is 1.9398 when the temperature is 96 K. An estimation of the Tolman length is obtained based on a relationship between the isothermal compressibility, liquid density and speed of sound in a liquid. © Copyright 2016 American Scientific Publishers All rights reserved.


Cao J.,Tsinghua University | Cao J.,University of South China | Wang L.,Tsinghua University | Wang L.,Huadong Institute of Lithium Ion Battery | And 10 more authors.
Electrochimica Acta | Year: 2013

Interfacial compatibility of composite polymer electrolyte and electrode is the key factor to affect the performance of polymer Li-ion batteries. In this work, liquid electrolyte, pristine PVDF-HFP (poly(vinylidene fluoride-co-hexafluoropropylene)) gel polymer electrolyte (GPE) and nano-TiO2-poly(methyl methacrylate) (PMMA) hybrid doped PVDF-HFP composite polymer electrolyte (CPE) are used to investigate the interfacial compatibility between electrolyte and electrode on performance of LiCoO 2/Li cells. The electrochemical performances of cells are studied by charge/discharge tests and electrochemical impedance. The interfacial compatibility coefficient (λ) that related to the interface of electrolyte and electrode is evaluated in terms of the fitting (i = e, sf, b and ct) with equivalent circuit and diffusion resistance (Rdiff). The results confirm that the C-rare performance of cells with GPE is more significantly associated with the interfacial compatibility than the ionic conductivity of GPE. © 2013 Elsevier Ltd.


Cao J.,University of South China | Cao J.,Tsinghua University | Wang L.,Tsinghua University | Shang Y.,Tsinghua University | And 8 more authors.
Electrochimica Acta | Year: 2013

The presented contribution aims at investigating the role of nano-TiO 2 dispersibility in affecting the performance of PVDF-HFP based composite polymer electrolytes (CPEs) for Li-ion cells. Four types of polymer electrolytes containing pristine PVDF-HFP gel polymer electrolyte (GPE), PVDF-HFP/nano-TiO2 CPE, PVDF-HFP/nano-TiO2-PMMA CPE and PVDF-HFP/high-dispersed nano-TiO2-PMMA CPE membranes are obtained by phase inversion. The effect of nano-TiO2 dispersibility on performances of PVDF-HFP based CPEs in terms of ionic conductivity, C-rate and cycling performance is investigated. The results demonstrate that the dispersibility of nano-TiO2 is a key factor to affect the performance of PVDF-HFP based CPEs, and the improvement of the dispersibility of nano-TiO2 can remarkably enhance the electrochemical performances of cells assembled with the corresponding CPEs. © 2013 Elsevier Ltd. All rights reserved.


Cao J.,University of South China | Cao J.,Tsinghua University | Wang L.,Tsinghua University | Wang L.,Huadong Institute of Lithium Ion Battery | And 11 more authors.
Journal of Power Sources | Year: 2014

Titania-poly(methyl methacrylate) (PMMA) organic-inorganic hybrid material is synthesized via in situ polymerization. The hybrid material is employed to prepare poly vinylidene fluoride-hexafluoropropylene (PVdF-HFP) composite polymer electrolyte. The effect of the hybrid material is investigated by SEM, TG-DSC, AC impedance and charge/discharge cycling tests. The results demonstrate that the inorganic-organic hybrid material as additive increases the porosity, pore size and electrolyte uptake of the PVdF-HFP composite polymer electrolyte membrane, so that the ionic conductivity of the composite polymer electrolyte membrane is improved. The performance enhancement of the composite polymer electrolyte is confirmed by an electrochemical test using LiCoO2/Li cells in the voltage range of 2.75-4.4 V. This study shows that titania-PMMA hybrid material is a promising additive for PVDF-HFP composite polymer electrolyte for Li-ion batteries. © 2013 Elsevier B.V. All rights reserved.


Yang J.,Tsinghua University | Zhao P.,Tsinghua University | Shang Y.,Tsinghua University | Shang Y.,Huadong Institute of Lithium Ion Battery | And 5 more authors.
Electrochimica Acta | Year: 2014

N,N′-4,4′-diphenylmethane-bismaleimide (BMI) is attempted to enhance the high-voltage performance for lithium-ion batteries. When 0.1% (m/v) BMI is added into the control electrolyte, the high-voltage cycling performance of LiCoO2/Li cells is improved evidently while charging the cell up to 4.5 V rather than the conventional 4.2 V. Analysis of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) demonstrate that an interface film forms on the cathode surface from BMI in electrolyte. AC impedance spectra and charge/discharge test were tested after incubation of the charged cell at 60 C. Linear sweep voltammetry (LSV) is used to test the electrochemical stability window of the electrolyte with BMI addition. The results demonstrate that the improvement of high-voltage performance is attributed to the surface film on cathode. In addition, the BMI addition does not cause damage in conventional performance with 4.2 V electrochemical window. The BMI-containing electrolyte provides high-voltage cycling performance with 4.5 V electrochemical window, making LiCoO2 battery a simple and promising system for applications with high energy density. © 2014 Elsevier Ltd.


Dai Z.,Tsinghua University | Dai Z.,Huadong Institute of Lithium Ion Battery | Wang L.,Tsinghua University | Wang L.,Huadong Institute of Lithium Ion Battery | And 7 more authors.
Electrochimica Acta | Year: 2014

Anion species are proved to have a significant influence on orientation, agglomeration and defect control of crystal growth for LiMn0.9Fe 0.1PO4 nano-particles prepared by solvothermal synthesis. SO4 2- is helpful for high dispersity, while Cl- benefits accurate molar ratio control of transition metals in LiMn 0.9Fe0.1PO4. Various LiMn0.9Fe 0.1PO4 particles, being agglomerative spindles or mono-dispersed uniform nano-flakes, can be obtained by just tuning [Cl -]:[SO4 2-] ratio, and present dramatically different electrochemical performances. Though the as-prepared samples possess similar reversible capacities around 130 mAh g-1 at low C-rate, they show very different rate performances depending on morphology of the particles. © 2014 Elsevier Ltd.


Ye F.,Tsinghua University | Ye F.,University of Science and Technology Beijing | Wang L.,Tsinghua University | Wang L.,Huadong Institute of Lithium Ion Battery | And 10 more authors.
Journal of Power Sources | Year: 2014

Solvothermal approach is used to synthesize LiMn0.9Fe 0.1PO4 (LMFP) nanomaterial for Li-ion batteries (LIBs). Experimental parameters such as feeding sequences, reaction time and reaction temperature are discussed and the obtained LMFP are characterized by XRD, SEM and TEM. To understand the formation of LMFP, a reaction mechanism is proposed. The proposed mechanism indicates that the suitable concentration of M Li (M = Fe, Mn) antisite defect can improve the electrochemical performance of the material. The charge-discharge data of obtained LMFP shows that the LiMn0.9Fe0.1PO4 material synthesized at 180 C for 4 h and then sintering with sucrose at 650 C for 5 h under argon protection has the highest discharge capacity, which is 149.2 mAh g-1 at 0.1C rate. © 2013 Elsevier B.V. All rights reserved.


Jin Y.,Tsinghua University | Wang L.,Tsinghua University | Shang Y.,Tsinghua University | Gao J.,Tsinghua University | And 3 more authors.
Electrochimica Acta | Year: 2015

The monodisperse Co3O4 mesoporous microdisks have been successfully prepared through a facile solvothermal synthesis method and subsequent heating treatment. The Co3O4 microdisks are polycrystalline, and have an average diameter of around 2 μm with an thickness of 300 nm. The specific surface area of Co3O4 mesoporous microdisks is about 108.9 m2 g-1 with a narrow pore size distribution centered at round 9.68 nm. The as-prepared Co3O4 mesoporous microdisks as anode material in lithium ion batteries exhibit a stable specific discharge-charge capacity of 765 and 749 mAh g-1 after 30 cycles at a current density of 100 mA g-1. The good electrochemical properties could be attributed to the unique mesoporous structure of Co3O4 materials. © 2014 Elsevier Ltd. All rights reserved.


Wang X.-S.,Henan Polytechnic University | Wang X.-S.,Tsinghua University | Wang X.-S.,Huadong Institute of Lithium Ion Battery | Cui S.-W.,Hebei Normal University | And 4 more authors.
Journal of Adhesion Science and Technology | Year: 2014

Using Gibbs method of dividing surfaces, the contact angle of a drop on a flat homogeneous rough non-deformable solid substrate is investigated. For this system, a new generalized Youngs equation for the contact angle, including the influences of line tension and which valid for any dividing surface between liquid phase and vapor phase is derived. Under some assumptions, this generalized Youngs equation reduces to the Wenzels equation or Rosanovs equation valid for the surface of tension. © 2013 © 2013 Taylor & Francis.


Huang C.,Tsinghua University | Huang C.,Huadong Institute of Lithium Ion Battery | Ai D.,Tsinghua University | Wang L.,Tsinghua University | And 2 more authors.
Chemistry Letters | Year: 2013

LiFePO4 nanoplates with an average thickness of less than 50 nm are synthesized through a simple coprecipitation in ethylene glycol solution at 180 °C. The evolution of the product species and intensity distribution of XRD patterns during coprecipitation are investigated to verify the formation and growth of the LiFePO4 nanoplates. The results indicate that the time for the formation of LiFePO4 nanoplates with high crystallinity is only 20 min. It is found that the feeding sequence has an important influence on LiFePO4 crystal growth and is useful for the tuning of crystal orientation and particle size. © 2013 The Chemical Society of Japan.

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