1、,第十四屆搖籃杯“北京科技大學大學生課外學術科技作品賽,2015,材料合成化學PPT競賽,Synthesis of LiNi0.5Mn1.5O4,Advantages: high energy densities, obtained either by high voltage or high capacity,Spinel structure,Positive electrode materia of lithium batteries,LiNi0.5Mn1.5O4,Approaches to synthesize,Solid-state reactions Solgel technolog

2、y Coprecipitations Emulsion drying Molten salt technology Spray pyrolysis,5,Synthesis of precursor,Sintering process,Co-precipitation,6,Stoichiometric amounts of Mn, Li, and Ni acetates were dissolved in H2O and stirred for 1h，Oxalic-acid solution was then added dropwise under stirring.,The precipit

3、ate solution was stirred for 1h before being dried at 50 over night with constant stirring.,The dried precipitate was preheated at 500 for 6h and then ground for 30min,The preheated powder was pressed into pellets (20mm dia. and ca. 5mm thick) and annealed at 900 for 24h in air,Precipitate,Drying,Pr

4、eheat,Sintering,Preparation Process,7,The advantages and disadvantages,Advantages: Easy to control reaction process The product of particles generally small and uniform,Good electrochemical properties,Disadvantage: Need to adjust the proportion of Li, Ni, Mn,Organic coprecipitation,Schematic Illustr

5、ation of 8-Hydroxyquinoline Coprecipitation Route,A,B,Ni(Ac)26H2O Mn(Ac)24H2O LiAc ambient temperature,water,8-hydroxyquinoline 60C,ethanol,solidliquid dispersion (brown flocculent precipitation),stir for 2h,evaporate at 80C without filtration,drying in air,100C,preheat at 470C for 5 h,dark power pr

6、ecursor,Preparation Process,To compare, samples were prepared using solid-state method (marked as SS) and normal coprecipitation method with KOH as precipitant (marked as HC) as well.,Preparation Process,SEM images of (a) samples SS, (b) samples HC, and (c) samples QC.,Characterization-morphology,Th

7、e organic precipitator can be easily removed The formation of LixNi1-xO impurities and oxygen deficient can be greatly restrained Avoid the deviation introduced by the oxidation of some Ni2+ during drying,Improvement,Rapid heating,High Uniformity,Precise temperature controlling,Microwave sintering,M

8、icrowave tube furnance,Preparation Process,Characterization-morphology,Electrical performance,Requiring much shorter time Growing to octahedral during the preferential and rapid crystal growth Tuning the Mn3+ content of the spinel for enhanced electrochemical performance.,Improvement,Pulsed laser de

9、position is a physical vapor deposition process, carried out in a vacuum system, that shares some process characteristics common with molecular beam epitaxy and some with sputter deposition.,Pulsed laser depsition(PLD),1.Pulsed laser is focused onto a target 2.Laser pulse vaporizes or ablates creati

10、ng a plasma plume 3.Ablation plume provides the material flux for film growth,Preparation Process,Electrical performance,SEM of LiNi0.5Mn1.5O4 Film,(a)and (b) initial discharge curves (c)and (d) coulombic efficiency curves,Characterization-morphology,Improvement,High deposition rate Good crystallini

11、ty Easy to control thickness Uniformity Direct stoichiometry transfer from the target to the film,Advantages,High deposition rate Good crystallinity Easy to control thickness Uniformity Direct stoichiometry transfer from the target to the film,Electrospinning,Characterization-morphology,Electrical p

12、erformance,Electrochemical characterizationreversible capacity：102mA.h/g1 Operating potential：2.8V Capacity retention：86% after 400 cycles.,Advantages,Shorter ion diffusion distance Accurater stoichiometric ratio of LiNi0.5Mn1.5O4 Inhibit the aggregation of particles,References,1 D. Liu et al. / Str

13、ucture, morphology, and cathode performance of Li1xNi0.5Mn1.5O4prepared by coprecipitation with oxalic acidJournal of Power Sources 195 (2010) 29182923. 2 Feng J, Huang Z, Guo C, et al. An organic coprecipitation route to synthesize high voltage LiNi0. 5Mn1. 5O4J. ACS applied materials & interfaces,

14、2013, 5(20): 10227-10232. 3PoGao,etc.MicrowaverapidpreparationofLiNi0.5Mn1.5O4andtheimprovedhighrateperformanceforlithium-ionbatteriesJ.ElectrochimicaActa100(2013)125-132. 4CharlJ.Jafta,etc.Microwave-assistedsynthesisofhigh-voltagenanostructuredLiNi0.5Mn1.5O4Spinel:tuningtheMn3+contentandelectrochem

15、icalperformanceJ.ACSAppl.Mater.Interfaces2013,5,7592-7598.,References,5J. Jian, Y. Y. Zhu, Q. Su, H. Wang. A new approach to investigate Li2MnO3 andLi(Ni0.5Mn0.3Co0.2)O2 mixed phase cathode materialsJ, J. Mater. Chem. A., 2014, 2: 2283. 6 H. Xia, Y. S. Meng, L. Lu, and G. Ceder. Electrochemical Properties of NonstoichiometricLiNi0.5Mn1.5O4-Thin-Film Electrodes Prepared by Pulsed Laser Deposition, Electrochem. Soc., 2007, 158(8): 737-743. 7Eiji Hosono, etc. Synthesis of LiNi0.5Mn1.5O4 and 0.5Li2MnO30.5LiNi1/3Co1/3Mn1/3O2 hollow nanowires by electrospinningJ.CrystEngCom