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,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,单击此处编辑母版标题样式,单击此处编辑母版文本样式,第二级,第三级,第四级,第五级,*,Exploration research of new cathode materials with high capacity for Li-ion battery,Yong Yang,State Key Lab of Physical Chemistry of Solid Surface,Xiamen University,China,1,Whatare the major players of the cathode materials,Electrode materials,High energy density,High power density,Layered oxide cathode materials,Polyanion:,LFePO,4,Spinel, LiMn,2,O,4,High energy density,Li,2,FeMnSiO,4,;,Organic-type,Fluorides,2,Further improvement of layered oxide-based cathode materials,1) Nickel-based layered cathode materials:,Lattice-doping,Surface coating,1) H. S. Liu, et al ; Electrochimica Acta, 2004, 49:1151-1159; Solid State Ionics, 2004, 166:317-325,2) Z.R.Zhang, et al; J Power Sources, 2004, 129(1):101-106; J. Phys. Chem. B; 2004, 108, 17546-17552,2) Li-rich Li-Ni-Co-Mn-O system;,Very promising system, still more study are needed. E.g. first cycle efficiency, rate capability, safety issues, how choose suitable anode systems.,3,High-Capacity,LiLi,(1-x)/3,Mn,(2-x)/3,Ni,x/3,Co,3/x,O,2,Cathode,Charge/discharge at 18 mA/g, 2.0 4.8 V,The initial discharge capacity is,249 mAh/g,about 100 mAh/g higher than that of LiCoO,2,.,0.1 C,Bare,AlF,3,-coated,Charge (mAh/g),324.5,314.0,Discharge (mAh/g),249,263.1,ICL (mAh/g),75.5,50.9,4,Layered Oxide-type Cathode Materials,High energy density batteries,Layered oxide cathode materials,Li,2,MnO,3,.,LiNi,x,Co,y,Mn,1-x-y,O,2 :,270mAh/g or even higher,Gas evolution,e.g. O,2, CO,2,High capacity,cathode materials,Charging to high voltage,5,In-situ Electrochemical Mass spectroscopic techniques and Its use in Li-ion batteries,AlF,3,coating layer provides,a buffer layer,to,make,oxygen atoms with high activity combine together to form O,2,molecules with low oxidation capability to electrolytes.,1/4,5 times,6,Advantages:,Low cost,excellent thermal stability,no oxygen evolved at low,amount Li,+,intercalated,Disadvantages: Lower capacity and low electronic conductivity,Phosphate should be developed as High Power Density and Safe Cathode Materials,Polyanion compounds(i.e. LiFePO4) with stable framework is one of the excellent candidate as new generation cathode materials in lithium-ion batteries,7,Olivine type: LiMPO,4,(PO,4,),3-,Orthosilicates: Li,2,MSiO,4,(SiO,4,),4-,The redox potential of M,n+/n+1,can be modulated by the coordinated polyanion group,Lower inductive effects of silicate anions compared with phosphate anion, but higher inductive effects than oxide anion is expected.,8,Why do we choose Silicates ?,orthosilicate materials (,Li,2,MSiO,4,):,Two lithium ions,should be reversible extracted or inserted in principle without distinctively changes of the crystal structure,.,9,A novel cathode materials with more than,one electron exchange: Li,2,MnSiO,4,Rietveld plot of Li,2,MnSiO,4,/C composite.,Y. X. Li, Z.L.Gong, Y. Yang; J. Power Sources, 174(2), 528-532, 2007,Y.Yang, Y.X.Li, Z.L.Gong; Chinese Patent CN 2,10,Li,2,MnSiO,4,正极材料循环性能的研究,Cyclic stability of Li,2,MnSiO,4,material is poor!,11,The first charge/discharge profiles of Li,2,Mn,1-x,Fe,x,SiO,4,/C at a current density of 10 mA g,-1,.,*,*,Z.L. Gong, Y.X. Li, Y. Yang, Electrochem. Solid-State Lett. 9 (2006) A542.,A capacity of 214 mAh/g (86% of the theoretical capacity, 1.29 electrons per unit formula) was,achieved,for Li,2,Mn,x,Fe,1-,x,SiO,4,(,x,= 0.5) sample,.,Li,2,Mn,1,-x,Fe,x,SiO,4,/C,12,Cyclic performance,of improved Li,2,Mn,0.5,Fe,0.5,SiO,4,Current density,：,10mA/g (C/16),，,Temperature,：,30,o,C,13,Evidence for fading mechanism of Li,2,MnSiO,4,870cm-1,SiO,4,4-,SiO,4,4-,SiO,4,4-,SiO,3,2-,14,Solid MAS,7,Li NMR of Li,2,MnSiO,4,at different,charged states,From ex-situ NMR spectra, it is proposed that the rate of deintercalation of Li+ at different sites are different, and some Li,2,SiO,3,are newly formed,15,Questions,Can we get better cyclic performance in SiO,4,4-,framework with more than one electron for transition metal ions ?,What are main factors control the capacity and cyclic stability of the silicates materials?,Whats the reaction step and mechanism for mixed system, i.e. Li,2,Fe,1-x,Mn,x,SiO,4,(0,x1),In-situ or ex-situ XAS, Solid MAS NMR, Mossbauer ,16,XRD pattern of Li,2,Fe,0.5,MnSiO,4,SEM images of Li,2,Fe,0.5,Mn,0.5,SiO,4,Structure and,morphology,of,Li,2,Fe,0.5,Mn,0.5,SiO,4,/C,17,Electrochemical performances of Li,2,Fe,0.5,Mn,0.5,SiO,4,The initial two cycles at 5 mA/g between 1.5 and 4.8 V.,The initial two cycles at 10 mA/g between 1.5 and 4.8 V.,The initial two cycles at 150 mA/g between 1.5 and 4.8 V.,18,Cyclic performances of Li,2,Fe,0.5,Mn,0.5,SiO,4,at 5, 10 and 150 mA/g, and Li,2,MnSiO4 at 5 mA/g,19,i=20 mA/g, 1.5-4.8,V,Electrode Reaction Mechanism Study- In-situ XANES,The first charge-discharge curves of Li,2,Fe,0.5,Mn,0.5,SiO,4,during in-situ measurement,SSRF Shanghai, China,上海同步辐射光源,20,In-situ Fe K-edge XANES spectra during the first charging process,21,In-situ Mn K-edge XANES spectra during the first charging process,22,Evolution of absorption edge of Fe and Mn of Li,2,Mn,0.5,Fe,0.5,SiO,4,in,the first charging and discharging processes.,23,Nano-structured Li,2,FeSiO,4,with excellent,rate capabilities and cyclic stability,Space group:,Orthorhombic,Pmn2,1,X-ray diffraction patterns of,the carbon coated Li,2,FeSiO,4,.,Insert:,TEM image,of,the,material.,Z. L. Gong, Y. X. Li, G. N. He, J. Li, Y. Yang*,Electrochem. Solid State Lett., 11, A60-63 (2008).,24,Structure, Morphology and Microstructure of,Carbon-coated Li,2,FeSiO,4,Nanostructured characteristic of the Li,2,FeSiO,4,make it as high-rate cathode materials feasible,25,The inverse of the magnetic susceptibility with temperature agrees well with paramagnetism for pure sample. The arrow point out the anomalies characteristics of an antiferromagnetic ordering of Li,2,FeSiO,4,below,T,N,= 20 K. The curve agree well with Curie-Weiss law in the whole paramagnetic region.,26,Electrochemical performance of the Li,2,FeSiO,4,cathodes,at different cycles,1.54.8 V versus Li,+,/Li; 1/16 C,Z. L. Gong, Y. X. Li, G. N. He, J. Li, Y. Yang*,Electrochem. Solid State Lett., 11, A60-63 (2008).,27,Excellent rate-performance of the silicate cathode materials,Z. L. Gong, Y. X. Li, G. N. He, J. Li, Y. Yang*,Electrochem. Solid State Lett., 11, A60-63 (2008).,Reasons: P,orous nanostructure, and improved electronic conductivity through carbon connection.,28,Excellent cyclic stability of Li,2,FeSiO,4,29,Excellent thermal stability,No extra heat give off during heating process!,30,At our synthesis conditions, two modifications of Li,2,CoSiO,4,(, and ,) which are derivatives of low temperature Li,3,PO,4,were obtained.,a:,; O,orthorhombic and space-group,Pmn2,1,.,b:,orthorhombic,The XRD profiles of the Li,2,CoSiO,4,powers prepared at different conditions.,Co-silicates- Li,2,CoSiO,4,L. Gong, Y. X. Li, Y. Yang; J Power Sources, 2007, 174(2), 524-527,S. Q. Wu, J. H. Zhang, Z. Z. Zhu and Y. Yang,Curr. Appl. Phys.,2007, 7, 611,31,The temperature dependence of the inverse molar magnetic susceptibility 1/,m,for Li,2,CoSiO,4,powers prepared at 873 K.,The magnetization curves,M,(,H,) at 2 K for Li,2,CoSiO,4,powers prepared at 873 K.,Magnetic property,32,Galvanostatic chargedischarge curves for Li,2,CoSiO,4,-based cathodes at current rate 16 mA/g.,Electrochemical performance,33,space-group: Pmn2,1,SiO,4,-,MO,4,LiO,4,SiO,4,-,MO,4,Corrugated layer,First-principles investigations on the structural and electronic properties,Structure of Li,2,MSiO,4,Reference:,S.Q.Wu, et al; Computational Materials Science, 2009, 44, 1243-1251,O Co - O,O Si - O,34,Conclusions,A series of,silicates cathode materials such as Li,2,FeSiO,4, LiFe,x,Mn,1-x,SiO,4, Li,2,CoSiO,4,with and without carbon coating have been synthesized, some of them could achieve more than 1-1.6 Li,+,reversible exchange. e.g. Li,2,Mn,0.5,Fe,0.5,SiO,4,with 235 mAh/g has been achieved.,We have made a c,arbon-coated nanostructured Li,2,FeSiO,4,material with e,xcellent rate performance, it,shows,a promise as,cathode materials for high-power lithium-ion batteries.,Phase-pure Li,2,CoSiO,4,has been prepared successfully and its physical properties and electrochemical performance were characterized,.,35,Some comments,We have made some promising progress about silicates in the last few years, but due to several phases or even impurity may be formed during the synthesis, we need to refine our synthesis route and get well-controlled and phase-purifed products with satisfied electrochemical performance.,Silicates system is quite complex than we imagine, we need to more techniques to characterize it, esp. in-situ techniques for characterization of intercalation/de-intercalation process including bulk and local crystal and electronic structure,36,37,
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