Tingfeng Yi

Improved electrochemical performance of Ag-modified Li4Ti5O12 anode material in a broad voltage window

AbstractLi4Ti5O12/Ag composites were synthesized by a solid-state method. The effect of Ag modification on the physical and electrochemical properties is discussed by the characterizations of X-ray diffraction, scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, cycling and rate tests. The lattice parameter of Li4Ti5O12 with a low Ag content is almost not changed, but the lattice parameter becomes larger due to the high content of Ag. Li4Ti5O12/Ag material has a uniform particle size which is about 1

Effect of temperature on lithium-ion intercalation kinetics of LiMn1.5Ni0.5O4-positive-electrode material

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Effects of Al, F dual substitutions on the structure and electrochemical properties of lithium manganese oxide

m. Modification of appropriate Ag is beneficial to the reversible intercalation and deintercalation of Li + . Modification of Ag not only decreases the charge transfer resistance of Li4Ti5O12 material, but also improves the diffusion coefficient of lithium ion. Li4Ti5O12/Ag (3 mass%) material has the lowest charge transfer resistance, the highest diffusion coefficient of lithium ion and the best rate cycling performance. Graphical AbstractLi4Ti5O12/Ag composites were synthesized by a solid-state method, and the remarkably improved rate properties of the Ag-modified samples are due to high conductivity of Ag at the surface of Li4Ti5O12, and faster kinetics of both the Li+ diffusion and the charge transfer reaction.

Measuration of Nanometer Grain Content for Complex Material by Spectrophotometric Method

LiMn1.5Ni0.5O4 is synthesized by a sol–gel method and the intercalation kinetics as positive electrode for lithium-ion batteries is investigated by EIS. LiMn1.5Ni0.5O4 particles prepared via sol–gel process possess spinel phase with Fd-3m space group. The charge-transfer resistance, the exchange-current density and the solid-phase diffusion are found as a function of temperature. The apparent activation energy of the exchange current, the charge transfer, and the lithium diffusion in solid phase are also determined, respectively. This result indicates that the effect of the temperature on the cell capacity and the current dependence of the capacity results mainly from the enhancement of the lithium diffusion at elevated temperatures. It can be concluded that LiMn1.5Ni0.5O4 cell has a bad rate cycling performance at elevated temperatures before any modification due to the high diffusion apparent activation energy. The relevant theoretical elucidations thus provide us some useful insights into the design of novel LiMn1.5Ni0.5O4-based positive-electrode materials.

Crystal structures of electrospun PVDF membranes and its separator application for rechargeable lithium metal cells

Abstract Spinel LiMn2O4 and F, Al-doped spinel LiAl0.05Mn1.95O3.98F0.02 have been synthesized by a soft chemistry method using adipic acid as the chelating agent. The synthesized spinel materials were characterized by differential thermal analysis (DTA) and thermogravimetery (TG), X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), and charge-discharge testing. The results indicate that all the samples have high phase purity, and fluorine is important in controlling the morphology; the doped aluminum enhances the stability of spinel LiMn2O4. The charge-discharge tests indicate that LiAl0.05Mn1.95O4 has high capacity retention, which is 92.60% of the initial after 50 cycles. It is found that the novel compound LiAl0.05Mn1.95O3.98F0.02 with smaller particles can offer much higher capacity, whose initial discharge capacity is 126.5 mAh·g−1. The cyclic voltammetric experiments disclose the enhanced reversibility of the F, Al3+-modified spinel as compared with the undoped spinel.

PE-g-MMA polymer electrolyte membrane for lithium polymer battery

The relation of direct proportion between absorbance and nanometer grain content is educed by analysing the extinction law which the monochromatic light passes turbid solution of nanometer grain. The feasibility mensurating nanometer grain content for complex material by spectrophotometric method is verified according to the composite deposit of Ni-P/alpha-Al2O3 (30nm). The results show that the standard curve of relation between the concentration of turbid solution of nanometer grain and absorbance is a straight line, and the linear correlative degree of the data reaches 99.96%. The measuring condition which the incident light wave is 500nm, and the concentration range of alpha-Al2O3 is 8-40mgmiddotL-1 is determined; moreover, the effect of ultrasonic wave dispersion on absorbency of nanometer particle is also studied. So it offers a better method to mensurate nanometer grain content for complex material