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1、Exploration research of new cathode materials with high capacity for Li-ion battery,Yong YangState Key Lab of Physical Chemistry of Solid Surface, Xiamen University China,Whatare the major players of the cathode materials,Electrode materials,High energy density,High power density,Layered oxide catho
2、de materials,Polyanion: LFePO4,Spinel, LiMn2O4,High energy density,Li2FeMnSiO4; Organic-type Fluorides,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;
3、 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 suit
4、able anode systems.,High-Capacity LiLi(1-x)/3Mn(2-x)/3Nix/3Co3/xO2 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 LiCoO2.,Layered Oxide-type Cathode Materials,High energy density batteries,Layered oxide cathode material
5、s Li2MnO3. LiNixCoyMn1-x-y O2 : 270mAh/g or even higher,Gas evolution, e.g. O2, CO2,High capacity cathode materials,Charging to high voltage,In-situ Electrochemical Mass spectroscopic techniques and Its use in Li-ion batteries,AlF3 coating layer provides a buffer layer to make oxygen atoms with high
6、 activity combine together to form O2 molecules with low oxidation capability to electrolytes.,1/4,5 times,Advantages: Low cost excellent thermal stability no oxygen evolved at low amount Li+ intercalatedDisadvantages: Lower capacity and low electronic conductivity,Phosphate should be developed as H
7、igh 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,Olivine type: LiMPO4 (PO4)3- Orthosilicates: Li2MSiO4 (SiO4)4-The redox potential of Mn+/n+1 can be modu
8、lated by the coordinated polyanion group Lower inductive effects of silicate anions compared with phosphate anion, but higher inductive effects than oxide anion is expected.,Why do we choose Silicates ? orthosilicate materials (Li2MSiO4):Two lithium ions should be reversible extracted or inserted in
9、 principle without distinctively changes of the crystal structure.,A novel cathode materials with more than one electron exchange: Li2MnSiO4,Rietveld plot of Li2MnSiO4/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 200610
10、005329,Li2MnSiO4正极材料循环性能的研究,Cyclic stability of Li2MnSiO4 material is poor!,The first charge/discharge profiles of Li2Mn1-xFexSiO4/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.,Li2Mn1-xFexSiO4/C,Cyclic performance of improved Li2Mn
11、0.5Fe0.5SiO4,Current density：10mA/g (C/16)， Temperature：30 oC,Evidence for fading mechanism of Li2MnSiO4,870cm-1,SiO44-,SiO44-,SiO44-,SiO32-,Solid MAS 7Li NMR of Li2MnSiO4 at differentcharged states,From ex-situ NMR spectra, it is proposed that the rate of deintercalation of Li+ at different sites a
12、re different, and some Li2SiO3 are newly formed,Questions,Can we get better cyclic performance in SiO44- 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
13、 for mixed system, i.e. Li2Fe1-xMnxSiO4 (0 x1)In-situ or ex-situ XAS, Solid MAS NMR, Mossbauer ,XRD pattern of Li2Fe0.5MnSiO4,SEM images of Li2Fe0.5Mn0.5SiO4,Structure and morphology of Li2Fe0.5Mn0.5SiO4/C,Electrochemical performances of Li2 Fe0.5Mn0.5SiO4,The initial two cycles at 5 mA/g between 1.
14、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.,Cyclic performances of Li2Fe0.5Mn0.5SiO4 at 5, 10 and 150 mA/g, and Li2MnSiO4 at 5 mA/g,i=20 mA/g, 1.5-4.8 V,Electrode Reaction Mechanism Study- In-situ XANES,The first cha
15、rge-discharge curves of Li2Fe0.5Mn0.5SiO4 during in-situ measurement,SSRF Shanghai, China 上海同步辐射光源,In-situ Fe K-edge XANES spectra during the first charging process,In-situ Mn K-edge XANES spectra during the first charging process,Evolution of absorption edge of Fe and Mn of Li2Mn0.5Fe0.5SiO4 inthe
16、first charging and discharging processes.,Nano-structured Li2FeSiO4 with excellent rate capabilities and cyclic stability,Space group: Orthorhombic Pmn21,X-ray diffraction patterns of the carbon coated Li2FeSiO4. 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).,Structure, Morphology and Microstructure of Carbon-coated Li2FeSiO4,
