Spinel LiMn2O4 microspheres and hollow microspheres with adjustable wall thickness have been prepared using controllable oxidation of MnCO3 microspheres precursors and following solid reactions with lithium salts. Sca...Spinel LiMn2O4 microspheres and hollow microspheres with adjustable wall thickness have been prepared using controllable oxidation of MnCO3 microspheres precursors and following solid reactions with lithium salts. Scanning electron microscopy （SEM） investigations demonstrate that the microsphere morphology and hollow structure of precursors are inherited. The effect of hollow structure properties of as-prepared LiMn2O4 on their performance as cathode materials for lithium-ion batteries has been studied. Electrochemical performance tests show that LiMn2O4 hollow microspheres with small wall thickness exhibit both superior rate capability and better cycle performance than LiMn2O4 solid microspheres and LiMn2O4 hollow microspheres with thick wall. The LiMn2O4 hollow microspheres with thin wall have discharge capacity of 132.7 mA.h-g^-1 at C/10 （14.8 mA.g^-1） in the first cycle, 94.1% capacity retention at C/10 after 40 cycles and discharge capacity of 116.5 mAh-gq at a high rate of 5C. The apparent lithium-ion diffusion coefficient （Dapp） of as-prepared LiMn2O4 determined by capacity intermittent titration technique （CITT） varies from 10-11 to 10-8.5 cm2.s^-1 showing a regular ＂W＂ shape curve plotted with test voltages. The D app of LiMn2O4 hollow microspheres with thin wall has the largest value among all the prepared samples. Both the superior rate capability and cycle stability of LiMn2O4 hollow microspheres with thin wall can be ascribed to the facile ion diffusion in the hollow structures and the robust of hollow structures during repeated cycling.展开更多
We report a facile method for the synthesis of manganese oxide（Mn3O4） nanorods via the direct reaction of MnCl2 and H2 O2 by doping Yb3＋ ions at room temperature and air atmosphere. The Mn3O4：Yb3＋ samples were ch...We report a facile method for the synthesis of manganese oxide（Mn3O4） nanorods via the direct reaction of MnCl2 and H2 O2 by doping Yb3＋ ions at room temperature and air atmosphere. The Mn3O4：Yb3＋ samples were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, cyclic voltammetry（CVs）, electrochemical impedance spectroscopy（EIS）, and charging-discharging test（CD）. The results show that trace Yb3＋ doping（6 at%） could effectively induce crystalline transformation of Mn3O4 from cubic system（space group Fd-3 m） to tetragonal system（space group I41/amd） and incite the morphology changing from irregular particles to uniform nanorods. When Yb3＋ doping amount is 3%, the capacitance of Mn3O4 reaches the maximum, 246 F/g, which is related to the morphology change and the corresponding decrease of impedance.展开更多
在乙醇胺和水组成的混合溶剂中,Mn(Ac)_2与氧化石墨烯一步反应得到还原石墨烯(RGO)与黑锰矿纳米颗粒(Mn_3O_4)组成的复合材料Mn_3O_4@RGO。以Mn_3O_4@RGO为正极,RGO为负极,组装得到了具有优良储能性能的非对称型超级电容器Mn_3O_4@RGO//...在乙醇胺和水组成的混合溶剂中,Mn(Ac)_2与氧化石墨烯一步反应得到还原石墨烯(RGO)与黑锰矿纳米颗粒(Mn_3O_4)组成的复合材料Mn_3O_4@RGO。以Mn_3O_4@RGO为正极,RGO为负极,组装得到了具有优良储能性能的非对称型超级电容器Mn_3O_4@RGO//RGO。基于活性物质的总质量,电容器的最大能量密度可达21.7 Wh/kg,相应的功率密度为0.5 k W/kg;同时,最大功率密度为8 k W/kg时,对应的能量密度为11.1 Wh/kg。Mn_3O_4@RGO//RGO还表现出良好的循环稳定性,在经历5000次循环后,比电容依然保持88.4%。电容器的良好储能性能可归因于在RGO表面生长的高密度Mn_3O_4纳米颗粒和RGO的良好导电性能。展开更多
基金Funded by the National Natural Science Foundation of China(Nos.20803056,11474226)the Fundamental Research Funds for the Central Universities(WUT:2015-IB-001,WUT:2016-IB-005)
文摘Spinel LiMn2O4 microspheres and hollow microspheres with adjustable wall thickness have been prepared using controllable oxidation of MnCO3 microspheres precursors and following solid reactions with lithium salts. Scanning electron microscopy （SEM） investigations demonstrate that the microsphere morphology and hollow structure of precursors are inherited. The effect of hollow structure properties of as-prepared LiMn2O4 on their performance as cathode materials for lithium-ion batteries has been studied. Electrochemical performance tests show that LiMn2O4 hollow microspheres with small wall thickness exhibit both superior rate capability and better cycle performance than LiMn2O4 solid microspheres and LiMn2O4 hollow microspheres with thick wall. The LiMn2O4 hollow microspheres with thin wall have discharge capacity of 132.7 mA.h-g^-1 at C/10 （14.8 mA.g^-1） in the first cycle, 94.1% capacity retention at C/10 after 40 cycles and discharge capacity of 116.5 mAh-gq at a high rate of 5C. The apparent lithium-ion diffusion coefficient （Dapp） of as-prepared LiMn2O4 determined by capacity intermittent titration technique （CITT） varies from 10-11 to 10-8.5 cm2.s^-1 showing a regular ＂W＂ shape curve plotted with test voltages. The D app of LiMn2O4 hollow microspheres with thin wall has the largest value among all the prepared samples. Both the superior rate capability and cycle stability of LiMn2O4 hollow microspheres with thin wall can be ascribed to the facile ion diffusion in the hollow structures and the robust of hollow structures during repeated cycling.
基金Supported by the National Natural Science Funds Youth Project of China(No.51704064)the Fundamental Research Funds for the Central Universities(No.N162302001)+3 种基金Hebei Province Higher Education Science and Technology Research Project(No.ZD2017309)the Scientific and Technological Research and Development Plan of Qinhuangdao City(201701B063)the further support fund of Key Laboratory of Nanomaterials and Photoelectrocatalysis in Qinhuangdao City(201705B021)the Northeastern University at Qinhuangdao Campus Research Fund(XNK201602)
文摘We report a facile method for the synthesis of manganese oxide（Mn3O4） nanorods via the direct reaction of MnCl2 and H2 O2 by doping Yb3＋ ions at room temperature and air atmosphere. The Mn3O4：Yb3＋ samples were characterized by X-ray diffraction（XRD）, scanning electron microscopy（SEM）, cyclic voltammetry（CVs）, electrochemical impedance spectroscopy（EIS）, and charging-discharging test（CD）. The results show that trace Yb3＋ doping（6 at%） could effectively induce crystalline transformation of Mn3O4 from cubic system（space group Fd-3 m） to tetragonal system（space group I41/amd） and incite the morphology changing from irregular particles to uniform nanorods. When Yb3＋ doping amount is 3%, the capacitance of Mn3O4 reaches the maximum, 246 F/g, which is related to the morphology change and the corresponding decrease of impedance.
文摘在乙醇胺和水组成的混合溶剂中,Mn(Ac)_2与氧化石墨烯一步反应得到还原石墨烯(RGO)与黑锰矿纳米颗粒(Mn_3O_4)组成的复合材料Mn_3O_4@RGO。以Mn_3O_4@RGO为正极,RGO为负极,组装得到了具有优良储能性能的非对称型超级电容器Mn_3O_4@RGO//RGO。基于活性物质的总质量,电容器的最大能量密度可达21.7 Wh/kg,相应的功率密度为0.5 k W/kg;同时,最大功率密度为8 k W/kg时,对应的能量密度为11.1 Wh/kg。Mn_3O_4@RGO//RGO还表现出良好的循环稳定性,在经历5000次循环后,比电容依然保持88.4%。电容器的良好储能性能可归因于在RGO表面生长的高密度Mn_3O_4纳米颗粒和RGO的良好导电性能。
