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Changxing, China

Yi T.-F.,Anhui University of Technology | Yi T.-F.,Harbin Institute of Technology | Yi T.-F.,Chilwee Power Co. | Yang S.-Y.,Anhui University of Technology | And 4 more authors.
Journal of Power Sources | Year: 2014

The spinel Li4Ti5O12 has been doped by Na for the purpose of improving its cycle performance as an anode. The lattice parameter of Li4Ti5O12 increases due to the Na doping. SEM shows that all materials are well crystallized with a particle size in the range of 400-600 nm. The pristine Li4Ti5O 12 sample has a bigger particle size than that of Na-doped samples. Although the doping does not change the crystallographic structure of Li 4Ti5O12, they exhibit better cyclability at high charge-discharge rate compared with pristine Li4Ti 5O12. Li3.85Na0.15Ti 5O12 gives the best cycling performance, only 11.1% loss of capacity after 80 cycles at 2 C charge-discharge rate. Na-doped Li 4Ti5O12 exhibits lower potential separation, indicating faster electron transfer kinetics and cycling reversibility. Electrochemical impedance spectroscopy demonstrates that the improved performance of the Na-doped Li4Ti5O12 is due to a small decrease in the charge transfer resistance, indicating high electrochemical activity during cycling. The excellent cycling and safety performance of the Na-doped Li4Ti5O12 electrodes are found to be due to the significantly increased ionic and electronic conductivity. Since fast charge-discharge performance is an important factor that needs to be considered in fabricating power batteries in industry, the Na-doped Li4Ti5O12 materials moves closer to real and large scale applications. © 2013 Elsevier B.V. All rights reserved.


Liu B.-S.,Harbin Institute of Technology | Wang Z.-B.,Harbin Institute of Technology | Zhang Y.,Harbin Institute of Technology | Yu F.-D.,Harbin Institute of Technology | And 4 more authors.
Journal of Alloys and Compounds | Year: 2014

Spinel LiMn2O4 has been synthesized by solid state reaction with industrial grade Mn3O4 and Li2CO3 as precursors without purification, and its electrochemical performance for lithium ion battery has been investigated by CR2025 coin cell. The results of X-ray diffraction (XRD) patterns and scanning electron microscope (SEM) images show that the size of LiMn2O4 particles grow up with increasing temperature of calcination, and the sample synthesized at 800°C for 12 h has the best crystallinity with a submicron size. It can deliver initial capacity of 112.9 mA h/g with capacity retention ratio of 89.1% after 200 cycles at charge/discharge rate of 1 C. The results of cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) also show that it has the highest electrochemical activity and lowest charge transfer impedance. © 2014 Elsevier B.V. All rights reserved.


Zhu Y.-R.,Anhui University of Technology | Yi T.-F.,Anhui University of Technology | Yi T.-F.,Harbin Institute of Technology | Yi T.-F.,Chilwee Power Co. | And 4 more authors.
Journal of Chemical Sciences | Year: 2014

Li4Ti5O12/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 Li 4Ti5O12 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 μm. 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 Li4Ti 5O12 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. © Indian Academy of Sciences.


Yi T.-F.,Anhui University of Technology | Yi T.-F.,Harbin Institute of Technology | Yi T.-F.,Chilwee Power Co. | Chen B.,Anhui University of Technology | And 3 more authors.
Journal of Power Sources | Year: 2014

The Mo-doped LiNi0.5Mn1.5O4 cathodes are successfully synthesized by citric acid-assisted sol-gel method. The result demonstrates that the Mo-doped LiMn1.4Ni0.55Mo 0.05O4 cathodes present the improved electrochemical performance over pristine LiNi0.5Mn1.5O4. At the 2 C rate after 80 cycles, the discharge capacities are 68.5 mAh g -1 for the pristine LiNi0.5Mn1.5O4 material (53.9% of the capacity at 0.1 C), 107.4 mAh g-1 for the LiMn1.425Ni0.5Mo0.05O4 material (82.1% at 0.1 C), and 122.7 mAh g-1 for the LiMn1.4Ni 0.55Mo0.05O4 material (90.5% at 0.1 C). Mo-doping is favorable for reducing the electrode polarization, suggesting that Mo-doped LiNi0.5Mn1.5O4 electrodes have faster lithium insertion/extraction kinetics during cycling. Mo-doped LiNi 0.5Mn1.5O4 electrodes show lower charge-transfer resistance and higher lithium diffusion coefficients. In addition, LiMn1.4Ni0.55Mo0.05O4 cathode exhibits the smallest particle size, the lowest charge-transfer resistance and the highest lithium diffusion coefficient among all samples, indicating that it has a high reversibility and good rate capability. © 2013 Elsevier B.V. All rights reserved.


Yi T.-F.,Anhui University of Technology | Yi T.-F.,Harbin Institute of Technology | Yi T.-F.,Chilwee Power Co. | Chen B.,Anhui University of Technology | And 4 more authors.
Journal of Alloys and Compounds | Year: 2013

Spinel Li4Ti5-xZrxO 12 (0 ≤ x ≤ 0.25) materials were prepared by a solid-state reaction method using Li2CO3, ZrO2 and TiO 2 as raw material, and the structure and electrochemical performance of the material were investigated by TG-DTA, XRD, SEM, CV, EIS and charge-discharge tests. The Zr-doped Li4Ti5O12 materials show much improved rate capability and specific capacity compared with pristine Li4Ti5O12. Especially, the pristine Li4Ti5O12 offers about 111 mA h g-1, but Li4Ti4.9Zr0.1O12 delivers a remarkable capacity of 172 mA h g-1 at 2 C charge-discharge rate. Li4Ti4.9Zr0.1O12 sample delivers a capacity of 155 mA h g-1 even after 150 cycles at 5 C charge-discharge rates, implying the possibility for high power applications, such as HEV and PHEV. The rate capability of the anode material made from the modified powder is significantly improved when discharged at high current rates due to the reduced charge transfer resistance and fast lithium insertion/extraction kinetics. © 2012 Elsevier B.V. All rights reserved.

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