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Hai-Lang Z.,Jiangnan University | Lei Z.,Jiangnan University | Shi-Wan Y.,Xinyang Vacational and Technical College
International Journal of Electrochemical Science | Year: 2014

Cathode material Li-Mn spinel materials LiMn2O4,LiAl0.05Mn1.95O3.95F0.05 and LiCo0.01Al0.05Mn1.94O3.95F0.05 for Li-ion battrry have been successfully synthsized by a citric acid sol-gel method. The crystalline structures of as-prepared cathode materials were characterized by XRD. The electrochemical performances of the materials were tested by constant-current cyclic testing and cyclic voltammogram. The results showed that the materials possessed pure spinel structure . By multiple co-doping with Al,Co and F elements, LiCo0.01Al0.05Mn1.94O3.95F0.05 exhibited very good electrochemical performance. Its initial specific discharge capacities were 122.9 mAh/g and 120.8 mAh/g at the room temperature (25 °C) and the high temperature (55 °C), respectively. Its capacity retentions were 96.8% and 92.5% after 40 cycles,respectively. It has been confirmed that multiple doping could improve the stability of spinel structure and cycle performance greatly. © 2014 The Authors.


Jian-Kun T.,Xinyang Vacational and Technical College | Fu-Cheng W.,Xinyang Vacational and Technical College | Battaglia V.S.,Lawrence Berkeley National Laboratory | Hai-Lang Z.,Lawrence Berkeley National Laboratory | Hai-Lang Z.,Jiangnan University
International Journal of Electrochemical Science | Year: 2014

Undoped and multiple doped Li-Mn spinel cathode materials for Li-ion battrry have been successfully synthsized by citric acid sol-gel method at a lower temperature 600 oC. The micro-structures for the materials were charactered by X-ray diffraction (XRD) and scanning electron microscope (SEM). All the synthesized materials are pure spinel phase with cubic structure and nano-sized. Their electrochemical properties were tested by galvanostatic charge-discharge cycling for the half-cells at at the current density 0.2mA·cm-2(equal to about C/3) between 3.0~4.5V (versus. Li/Li+) at room temperature. The undoped LiMn2O4 spinel has a high initial discharge specific capacity of 122.5 mAh.g-1 and a very high capacity retention of 92.4% after 40 cycles. The good result could be ascribed to its nano-scale size synthesized in lower temperature in a large part. By multiple doping, pure phase spinel Li1.03M0.06Mn1.91O4 (M= Zn0.03Mg0.03,Al0.03Zn0.03, Al0.03Mg0.03,Al0.03Mg0.015Zn 0.015) were obtained. Multiple doping could improve the Li-Mn spinel Li-ion battrry cathode materials furthermore. Among the synthesized materials, Li1.03Zn0.03Mg0.03Mn1.91O4 has the highest capacity retention of 97.4% after 40 cycles with an initial discharge specific capacity of 107.5mAh.g-1. © 2014 by ESG.


Fu-Cheng W.,Xinyang Vacational and Technical College | Jian-Kun T.,Xinyang Vacational and Technical College | Hai-Lang Z.,Jiangnan University
International Journal of Electrochemical Science | Year: 2014

A series of spinel Li1.02MgxMn1.98-xO4-yFy materials as cathode materials for Li-ion battery have been synthesized by one improved solid-state reaction method. Their structures and electrochemical performances are studied by XRD, CV and charge-discharge tests. Results show that the specific capacities of the materials have been increased with the co-doping of Mg and F, the stability of spinel structure and cycle performance were also improved by F-, Mg2+ and Li+ multiplex doping. The charge-discharge tests reveal that Li1.02Mg0.05Mn1.93O3.95F0.05 has the best cycling performance. Its first specific discharge capacity is 115.9mA.g-1 and 116.5 mAh.g-1 at 25°C and 55°C,respectively. The capacity retention ratios are 96.5% and 90.6% after 40 cycles at 25°C and 55°C, respectively. © 2014 The Authors. Published by ESG.

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