Yang Chen,Chengji Deng,Chao Yu,Jun Ding,Hongxi Zhu
ZrN nanopowders were obtained by using ZrO 2 and Mg as the main raw materials in a molten salt environment and a high-purity nitrogen atmosphere. The effects of ZrO 2 / Mg mole ratio, nitriding temperature , and holding time on the synthesis of ZrN were investigated. ZrN was formed at 700 °C for 3 h. When the nitriding temperature increased to 1000 °C, pure phase ZrN was formed. The specific surface area of ZrN was 20.92 m 2 /g. When the temperature rose to 1100 °C, the resulting ZrN particles were finer; the average size of ZrN decreased from 71.60 to 49.65 nm. Further, an excessively long holding time led to evaporation of the molten salt, ZrO 2 , which was not fully nitrided. Finally, a possible formation mechanism of ZrN is proposed.
As a promising anode material for next-generation high-energy density lithium-ion batteries (LIBs), one of the main technical issues for silicon (Si) electrodes is the low initial Coulombic efficiency (ICE). By a pre-lithiation process, preparation of lithium–silicon (Li–Si) alloy electrodes can efficiently improve the ICE, thus leading to excellent electrochemical performance. Herein, with solid wastes as precursors, we report a cost-efficient approach for the fabrication of Li3.25Si anode materials via simple magnesiothermic reduction and then mechanical alloy reaction methods, combining the advantages of low-cost and high ICE. The prepared Li3.25Si@acetylene black (Li3.25Si@A) electrode exhibits excellent electrochemical performance with a high reversible capacity of 1138.9 mA h g−1 over 90 cycles at a current density of 100 mA g−1 and its ICE is as high as 107.7%, which is superior to that of the commercial Li3.25Si@A electrode. With a simple and low-cost manufacturing process and high ICE, the fabrication process will be definitely meaningful in achieving low-cost and high-capacity anode materials with a prolonged cycle life.
Xiangyang Zhuang,Yao Zhang,Lingxiao He,Yunfeng Zhu,Quan Shi,Quan Wang,Guanzhou Song,Xiaoxiao Yan,Liquan Li
Overheating caused by exothermic effect of magnesiothermic reduction reaction is usually considered as a drawback in preparing porous silicon anode materials for Li-ion batteries. However, in the present work, thermal effect is available in facile preparation of macroporous Si by tabletting pretreatment . The released heat in magnesiothermic reaction is easily accumulated on the tablet with high density, leading to the collapse of the mesoporous structure of the precursor and formation of uniform macroporous silicon . Such macroporous silicon shows a higher initial Coulomb efficiency (86.5%) and enhanced cycling stability in comparison with mesoporous silicon prepared without tabletting treatment. XRD analysis indicates that the reaction temperature decreases to 430–435 °C (based on set temperature), much lower than that of the reaction without pretreatment. Since the structure of product has less dependency on precursor, a wide variety of precursors can be used to synthesize macroporous silicon, e.g. low cost biosilica. Being ascribed to low reaction temperature, heating rate insensitivity, less dependency on precursor, enhanced cycling performance and high initial Coulomb efficiency of the Si products, the modified magnesiothermic reduction method is promising for application in fabricating Si anode.
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