Guofeng Xu
University of Science and Technology Beijing
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Featured researches published by Guofeng Xu.
Journal of Materials Chemistry | 2014
Qingrui Xue; Jianling Li; Guofeng Xu; Hongwei. Zhou; Xindong Wang; Feiyu Kang
Lithium-rich layered Li[Li0.2Mn0.54Ni0.13Co0.13]O2 is prepared by a fast co-precipitation method and surface modified with conducting polyaniline (PANI, 5 wt%, 10 wt%, 15 wt%, 20 wt%, 30 wt% theoretically) via in situ chemical oxidation polymerization to optimize the electrochemical properties. The uniform PANI layer with a thickness of 5 nm (10 wt%) has been successfully coated on the surface of Li[Li0.2Mn0.54Ni0.13Co0.13]O2 particles, as observed by field-emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM). The X-ray powder diffraction (XRD) results show that all the prepared samples have a typical layered hexagonal α-NaFeO2 structure. The PANI layer maintains the integrity of the surface material crystal structure of the Li[Li0.2Mn0.54Ni0.13Co0.13]O2 particles by protecting the electrodes from external erosion during continuous charge–discharge cycles. PANI-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O2 electrodes present excellent electrochemical properties at room temperature. The initial discharge capacity is 313.5 mA h g−1 (0.05 C) with a coulombic efficiency of 89.01% (PANI, 10 wt%), compared with 291.9 mA h g−1 (0.05 C) for the pristine Li[Li0.2Mn0.54Ni0.13Co0.13]O2 with a coulombic efficiency of 81.31% in the potential range 2.0–4.8 V (vs. Li/Li+). The discharge capacity is retained at 282.1 mA h g−1 after 80 cycles at 0.1 C. Moreover, the PANI-coated Li[Li0.2Mn0.54Ni0.13Co0.13]O2 exhibits an excellent high rate capacity of 198.6 mA h g−1 at 10 C. The electrochemical impedance spectra (EIS) measurements reveal that the thin PANI coating layer significantly optimizes the interfacial electrochemical reaction activity by reducing the charge transfer resistance. Moreover, the special H+/Li+ exchange reaction during the proton acid doping procedure also promotes the improvement of the electrochemical performance.
ACS Applied Materials & Interfaces | 2017
Feixiang Ding; Jianling Li; Fuhai Deng; Guofeng Xu; Yanying Liu; Kai Yang; Feiyu Kang
Lithium-rich layered oxides (LLOs) have been attractive cathode materials for lithium-ion batteries because of their high reversible capacity. However, they suffer from low initial Coulombic efficiency and capacity/voltage decay upon cycling. Herein, facile surface modification of Li1.2Mn0.54Ni0.13Co0.13O2 cathode material is designed to overcome these defects by the protective effect of a surface heterostructure composed of an induced spinel layer and a PrPO4 modification layer. As anticipated, a sample modified with 3 wt % PrPO4 (PrP3) shows an enhanced initial Coulombic efficiency of 90% compared to 81.8% for the pristine one, more excellent cycling stability with a capacity retention of 89.3% after 100 cycles compared to only 71.7% for the pristine one, and less average discharge voltage fading from 0.6353 to 0.2881 V. These results can be attributed to the fact that the modification nanolayers have moved amounts of oxygen and lithium from the lattice in the bulk crystal structure, leading to a chemical activation of the Li2MnO3 component previously and forming a spinel interphase with a 3D fast Li+ diffusion channel and stable structure. Moreover, the elaborate surface heterostructure on a lithium-rich cathode material can effectively curb the undesired side reactions with the electrolyte and may also extend to other layered oxides to improve their cycling stability at high voltage.
RSC Advances | 2015
Hongwei Zhou; Xianan Ding; Guicheng Liu; Zhan Gao; Guofeng Xu; Xindong Wang
Ni substituted LiMn2O4 nanofiber cathode materials (LiNixMn2−xO4, x = 0.2, 0.3, 0.4, 0.5) have been prepared by a combination of electrospinning and sol–gel techniques. The nanofiber cathode materials appear to have a porous “network-like” morphology with nanosized diameters of ∼120 nm and microsized lengths of >5 μm. The structure provides short lithium diffusion paths and a large surface area, facilitating rapid charge–discharge characteristics. The Ni substitution not only mitigated the Jahn–Teller distortion effect but also greatly suppressed the Mn dissolution, which improved the rate capability and cycle performance. The LiNi0.4Mn1.6O4 nanofiber cathode exhibits excellent rate capability and cycle performance both at room temperature and at 55 °C. Thus, the LiNi0.4Mn1.6O4 nanofibers may be a potential cathode material for high rate discharge lithium ion batteries.
Electrochimica Acta | 2013
Yu Chen; Guofeng Xu; Jianling Li; Yakun Zhang; Zhong Chen; Feiyu Kang
Journal of Power Sources | 2014
Guofeng Xu; Jianling Li; Qingrui Xue; Xianping Ren; Gang Yan; Xindong Wang; Feiyu Kang
Journal of Alloys and Compounds | 2015
Yu Dai; Jianling Li; Gang Yan; Guofeng Xu; Qingrui Xue; Feiyu Kang
Electrochimica Acta | 2014
Guofeng Xu; Jianling Li; Qingrui Xue; Yu Dai; Hongwei. Zhou; Xindong Wang; Feiyu Kang
Materials Letters | 2014
Hongwei Zhou; Xianan Ding; Zhuang Yin; Guofeng Xu; Qingrui Xue; Jianling Li; Shuqiang Jiao; Xindong Wang
Electrochimica Acta | 2015
Guofeng Xu; Jianling Li; X.G. Li; Hongwei Zhou; Xianan Ding; Xindong Wang; Feiyu Kang
Particuology | 2014
Zhong Chen; Jianling Li; Yu Chen; Yakun Zhang; Guofeng Xu; Jun Yang; Ye Feng