Fe 2 O 3 nanoparticles are employed as a coating material to optimize the electrochemical performance of LiCoO 2 at high voltage. When the current rate is 1 C with the cutoff potential at 4.5 V, the 5 wt.% Fe 2 O 3 -coated LiCoO 2 delivers an initial capacity of 168.7 mAh g −1 . More importantly, its capacity retention after 50 cycles reaches up to 92.6%, whereas the value for pristine LiCoO 2 is only 58.5%. The electrochemistry impedance spectroscopy analysis demonstrates that Fe 2 O 3 coating plays an important role in decreasing the charge transfer resistance of cell. Compared with the performance of the Fe 2 O 3 -mixed and Fe-doped LiCoO 2 samples, it is found that the role of Fe 2 O 3 coating is unique, which may change the characteristic of the surface of LiCoO 2 particles. This technique may provide an effective and convenient way for optimizing other electrode materials .
Electrophoretic deposition (EPD) is a promising method for fast-preparing thermite (Al/MO x ) coatings and other energetic coatings with the advantages of simplicity, low cost, and wide adoptability for complex shapes. However, post-sintering treatment is unsuitable for enhancing the poor adhesion of electrophoretic Al/MO x coating and other energetic coatings because of the contradiction between the sintering temperature and the trigger temperature of thermite reaction. In this work, electrophoretic Al/MO x (i.e., Fe 2 O 3 ) coatings with high adhesion were designed by using other MO x nanoparticles (i.e., NiO) prepared via oil-phase synthesis (named as O-MO x ) as an outer coating. DSC curves show that the value of heat release in the electrophoretic NiO-Al/Fe 2 O 3 coating is 2568 J g −1 . The combustion test successfully confirms a violent and quick energy releasing of the designed Al/Fe 2 O 3 coating. More attractively, this strategy can also be employed to prepare many other kinds of Al/MO x coating (i.e., CuO, MoO 3 , WO 3 , Bi 2 O 3 ) or energetic coating (i.e., B/Ti) with good adhesion via EPD. In summary, this study provides a general strategy for electrophoretic preparation of Al/MO x coatings with high adhesion, excellent thermodynamic properties and electrical explosion performance, which would solve the key issue for preparing Al/MO x coatings through EPD technology.
Zigui Luo,Xi’an Fan,Wentao Hu,Fan Luo,Jian Wang,Zhaoyang Wu,Xin Liu,Guangqiang Li,Yawei Li
In this work, Fe–Si/Fe 2 SiO 4 soft magnetic composites (SMCs) are prepared successfully via sintering Fe-6.5 wt%Si/α-Fe 2 O 3 core-shell composite powders obtained by ball milling. The transformation mechanism from Fe-6.5 wt%Si/α-Fe 2 O 3 to Fe–Si/Fe 2 SiO 4 is revealed in detail. The effect of α-Fe 2 O 3 coating content on microstructure and magnetic properties for the Fe–Si/Fe 2 SiO 4 SMCs is also investigated. During the high temperature sintering process, α-Fe 2 O 3 coating will in situ react with diffused Si from Fe–Si alloy cores, and result in the generation of Fe 2 SiO 4 insulating layer and Fe atoms. When the α-Fe 2 O 3 coating content increases from 0.0 wt% to 7.5 wt%, the insulating layer becomes thicker. Nevertheless, with further increasing the α-Fe 2 O 3 coating content from 7.5 wt% to 12.5 wt%, the generation of excessive Fe breaks the continuity of the insulation layer. As a result, the saturation magnetization decreases gradually, while the coercivity exhibits an opposite trend. The core loss decreases firstly and then increases. Therefore, the Fe–Si/Fe 2 SiO 4 SMCs coated with 7.5 wt% α-Fe 2 O 3 exhibit superior comprehensive performance such as very low core loss (39.6 mW/cm 3 at 50 kHz), very high saturation magnetization (191.4 emu/g) and stable permeability (44) from 50 Hz to 200 kHz.
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