1、ACS Appl. Mater. Interfaces 2016, 8, 3172231728,Carbon-Free Porous Zn2GeO4 Nanofibers as Advanced Anode Materials for High-Performance Lithium Ion Batteries, Faculty of Chemistry, National & Local United Engineering Laboratory for Power Batteries, Northeast Normal University, Changchun, Jilin 130024
2、, China School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore,Reporter：HaHaHa 2016-12-10,Huan-Huan Li, , Xing-Long Wu, , Lin-Lin Zhang, Chao-Ying Fan, Hai-Feng Wang, Xiao-Ying Li, Hai-Zhu Sun,* , Jing-Ping Zhang,* , and Qingyu Yan* ,Abstract,Intro
3、duction,Experimental Section,Results and Discussion,Conclusions,2,Main contents,Abstract,In this work, carbon-free, porous, and micro/nano-structural Zn2GeO4 nanofibers (p-ZGONFs) have been prepared via a dissolution-recrystallization-assisted electrospinning technology.Electrochemical tests demonst
4、rate that the as-prepared p-ZGONFs exhibit superior Li-storage properties in terms of high initial reversible capacity, outstanding cycling stability, and excellent high-rate capabilities.The much enhanced Li-storage properties should be attributed to its distinctive structural characteristics inclu
5、ding the carbon-free composition, plentiful pores, and micro/nanostructures.Carbon-free composition promises its high theoretical Li-storage capacity.Plentiful pores cannot only accommodate the volumetric variations during the successive lithiation/ delithiation but can also serve as the electrolyte
6、 reservoirs to facilitate Li interaction with electrode materials.,1. Introduction,With todays modern technology, lithium ion batteries (LIBs) have been widely used as a main energy storage system to power portable electronics and electric vehicles.,requirements of the rapidly developed applications
7、,higher power and energy densities,Zn2GeO4,promising anode materials for LIBs,Advantage This high value originates from the dual Li-alloying reactions of Zn and Ge atoms in addition to the conversion reaction in comparison to other Ge-containing metal oxides, such as Ca2Ge7O16, Co2GeO4, and BaGe4O9,
8、 in which only Ge atoms can alloy with Li.,Drawbacks Zn2GeO4 anode will also encounter large volumetric variations and sluggish kinetics of ionic transports and conversion reactions during the successive Li-uptake/release processes.,To improve the cycling performance of TMOs,(1)prepare diverse nanos
9、cale structures,two strategies,(2)construct conductive carbonaceous networks,(1)But there are several severe issues: Hard to handle for electrode preparation during scalable processes; Easy coalescence during the longterm successive lithiation/delithiation; Inability to stack densely in the electrod
10、e; The complex, expensive, and low-yielding preparation procedures of nanostructures, limiting their practical applications. (2)For the much lower theoretical capacity (372 mAh g1) of the carbon anode compared to that of the TMOs, sometimes decreases the overall Li-storage capacity.,Electrospinning
11、technology has been demonstrated as an effective approach to fabricate micro/nanostructures with uniform one-dimensional (1D) morphology.A long continuous nanofiberstructure with evenly distributed porosity for Zn2GeO4 is still absent up to now, because almost all of the Ge-containing precursors(Ge,
12、 GeO2) are insoluble or can hydrolyze easily to become solid state in the precursor solution. In this work, author, for the first time, prepare the uniform 1D porous Zn2GeO4 nanofibers(p-ZGONFs) with the characteristics of carbon-free, porous, and micro/nanostructures via the dissolution-recrystalli
13、zation-assisted electrospinning technology. And all these Li-storage properties are much better than those of Zn2GeO4 nanorods(ZGONRs) prepared by a commonly employed hydrothermal process.,Figure S1. Schematic illustration for the preparation processes of p-ZGONFs,2. Experimental Section,Preparation
14、 of ZGONRs,Zn-(CH3COOH)22H2O,GeO2,distilled water,suspension,ultrasonication,185 20h,products,centrifugation,precipitate,dried at 80 overnight,ZGONRs,Preparation of p-ZGONFs,as-prepared ZGONRs,7.5 wt % aqueous PAA solution,stirred for 1 hroom temperature,mixed solution,citric acid,viscous solution,e
15、lectrospun,precursor solution,calcination,ZGONRs/PAA- CA fibers (p-ZGONFs),Electrochemical Measurement The working electrodes were prepared by mixing the active materials, acetylene black, and polyvinyldifluoride(PVDF), mass ratio 70:15:15 in N-methylpyrrolidone to form a slurry.Counter electrode- P
16、ure lithium foil Electrolyte- 1.0 mol L1 LiPF6 in ethylene carbonate (EC碳酸次乙酯)/dimethyl carbonate (DMC碳酸二甲酯) Galvanostatic cycling measurements-from 0.005 to 2.9 V at room temperatureCyclic voltammetry (CV) curves- 0.0052.9 V at a scan rate of 0.1 mV s1,Figure S3 XPS spectrum of the p-ZGONFs: (a) su
17、rvey spectrum, (b) Zn 2p, (c) Ge 3d, and (d) O 1s.,3. Results and discussion,Figure 1. (a, b) SEM images of p-ZGONFs under different magnifications. (c) SEM image of p-ZGONFs and corresponding energy-dispersive system (EDS) mapping for Zn, Ge, and O elements.,Figure 2. (a, b) Low- and high-magnifica
18、tion TEM images of pZGONFs. (c) Nitrogen adsorptiondesorption isotherms and (d) corresponding pore size distribution curves for p-ZGONFs.,Figure 3. (a) CV curves of the initial five cycles and (b) galvanostatic profiles for the p-ZGONFs. (c) The comparison of cycling performances between p-ZGONFs an
19、d ZGONRs at 200 mA g1. (d) The difference of specific capacity between p-ZGONFs and ZGONRs cycled at 200 mA g1. (e, f) High-rate capabilities of p-ZGONFs at various current densities from 0.2 A g1 to 10 A g1.,4.Conclusions,In summary, we have successfully developed a dissolution-recrystallization-as
20、sisted electrospinning technology to prepare the carbon-free, porous, and micro/nanostructural 1D Zn2GeO4 fibers.The as-prepared p-ZGONFs exhibit much improved Li-storage properties in terms of higher specific capacity, outstanding cycling stability, and high-rate performance compared to the common
21、ZGONRs.These superior electrochemical properties should be attributed to their unique carbon-free porous micro/nanostructures composed of smaller Zn2GeO4 NPs.The present work may pave a new way for the large-scale preparation of other carbon-free TMO nanofibers with porous structures composed of pri
22、mary nanoparticles.,Thanks for your attention !,Weekly Report,CdSe QDs,HDA TOPO SA CdO:0.05g (0.375mmol),140 keep1h,300 CdO disslove completely,260,Se powder:0.03g (0.375mmol) dissloved in 1.5mL TOP,reaction,final product,PL peak: 499nm; FWHM: 103nm,0min, 1min, 3min, 7min, 10min, 20min,1mL,+ 1mL graphene-COOH,ultrasonic dispersed for 10min,HDA TOPO SA + CdO:0.05g (0.375mmol),Se powder:0.03g (0.375mmol) dissloved in 1.5mL TOP,200,CdSe QDs,Plan of next week,1 try to read more literatures 2 reprepare CdSe QDs,Thanks a lot,
