碳纳米材料课件.ppt

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1、关于碳纳米材料现在学习的是第1页，共28页Four partsv1.Introduction v2.Experiment v3.Results and discussionv4.Conclusions 现在学习的是第2页，共28页Introduction vtransition metal oxides have attracted great attention as anode materials for lithium ion batteries,due to 1 their high theoretical capacity 2 safety 3 low cost 4 natural

2、abundance 现在学习的是第3页，共28页vSome obstacle 1 poor cycling performance(large volume expansion due to the generation of Li2O)2 poor electronic conductivity(electrode materials with designed nanostructure can improve it)现在学习的是第4页，共28页vMnO shows relatively low electromotive force电动势(emf)value(1.032 V vs.Li+

3、/Li)and high density(5.43 g cm3).However,this kind of material has seldom been reported as an anode material vnanocrystalline MnO thin film,and MnO powder as anode has shown low overpotential超电势 and good cycling performance 现在学习的是第5页，共28页vIn this paper The prepared MnO/C coreshell nanorods much high

4、er specific capacity than that of MnO microparticles and MnO2 nanowires as anode material of lithium ion battery.返回现在学习的是第6页，共28页Experiment 合成部分vMnO/C coreshell nanorods were synthesized by the reduction of carbon precursor coated MnO2 nanowires.vThe MnO2 nanowires were synthesized by a typical hydr

5、othermal reaction 现在学习的是第7页，共28页Experiment表征vX-ray diffraction v Field emission scanning electron microscopy(FESEM）v transmission electron microscopy(TEM)vSAED现在学习的是第8页，共28页Experiment电化学实验部分vperforming using 2032 coin-type cells assembled in an argon-filled glove box vslurry:active materials(70 wt%)

6、,acetylene black乙炔黑(20 wt%),and polyvinylidene fluoride 聚偏二氟乙烯(PVDF 10 wt%)in N-methyl-2-pyrrolidone 氮甲基二吡咯烷酮(NMP).vThe slurry was spread onto the Cu foil with a doctor blade刮墨刀片 and dried at 120 C overnight under vacuum 现在学习的是第9页，共28页Experimentvelectrode area is 1 cm2 vloading of active material is

7、 1.01.2 mg cm2 v electrolyte:a solution of 1 M LiPF6 in ethylene carbonate 碳酸亚乙酯(EC)and dimethyl carbonate 碳酸二甲酯(DMC)with a weight ratio of 1:1 现在学习的是第10页，共28页ExperimentvPure lithium foil was used as counter and reference electrodevCyclic voltammetry循环伏安法(CV)vChargedischarge testing was performed in

8、 the range of 0.013.0 V vspecific capacity 返回现在学习的是第11页，共28页Results and discussionv 1、MnO2 nanowires were synthesized by hydrothermal reaction.The crystal structure of the as-prepared MnO2 nanowires was confirmed by XRD(Fig.1)v All the diffraction peaks can be indexed to the body-centered tetragonal

9、-MnO2 phase 现在学习的是第12页，共28页Results and discussionv2、MnO/C coreshell nanorods were obtained through sintering the carbon precursor coated MnO2 nanowires in flowing Ar containing 5 vol.%H2.As shown in Fig.1v the crystal structure of MnO/C coreshell nanorods can be indexed to the face-centered cubic ph

10、ase of MnO vlow intensity diffraction peak in the range of 2030 is likely associated with the presence of amorphous carbon无定形碳(originated from the decomposition of the copolymer surfactant).现在学习的是第13页，共28页Results and discussion 现在学习的是第14页，共28页Results and discussionFESEM:nanowire structure with diame

11、ters ranging from 2050 nm and There is no significant change in diameter 现在学习的是第15页，共28页Results and discussionTEM 现在学习的是第16页，共28页The nanorods show polycrystalline feature and are agglomerated into bundles with a length extending to a few hundred nanometers.The fracturing of the nanowire structure in

12、to nanorods may be caused by the reduction from MnO2 to MnO.An individual nanorod consists of nanoparticles with diameters from 20 nm to 30 nm.Results and discussion现在学习的是第17页，共28页Results and discussion All the diffraction rings can be indexed to the face-centered cubic Fm-3m crystal structure.现在学习的

13、是第18页，共28页Results and discussion HRTEM现在学习的是第19页，共28页Results and discussionvIn the region A:the surface of the MnO crystal,and the lattice can be clearly resolved with a d-spacing of 0.255 nm for the(1 1 1)planes.vin the region B:carbon layer,which presents numerous black spots,indicating that the s

14、urface of the nanorod is covered with a thin layer of amorphous carbon.On the edge of the nanorod,a thin carbon layer with a thickness of 12 nm is clearly visible.现在学习的是第20页，共28页Results and discussioncyclic voltammetry(CV)现在学习的是第21页，共28页Results and discussion现在学习的是第22页，共28页Results and discussion现在学习

15、的是第23页，共28页Results and discussionCycling performance 现在学习的是第24页，共28页Results and discussionvThis nanorod electrode exhibited higher capacity than that of MnO2 nanowire electrode after 40 cycles.vThe good electrochemical performance is a result of the combined advantages of the nanorod structure and t

16、he porous carbon coating layer.现在学习的是第25页，共28页Results and discussionv Nanosize materials with large surface area can provide more active sites for Li+intercalation/de-intercalation and shorten the diffusion length for lithium ions in the solid phase.v The nanoporous carbon coating layer with mesopor

17、es can form a mixed conducting 3D network that facilitates the migration of both the Li+and the e,so that they reach each surface of the MnO nanorods.返回现在学习的是第26页，共28页Conclusions 1、Using block copolymer F127 as the carbon source,MnO/C coreshell nanorods were successfully prepared from MnO2 nanowires by calcination in a gas flow of 5 vol.%H2 in Ar.2、The XRD pattern shows that the product has a face-centered cubic phase structure.FESEM and TEM images show that a thin carbon layer was coated on the surfaces of the MnO nanorods.现在学习的是第27页，共28页感谢大家观看感谢大家观看现在学习的是第28页，共28页