高容量锂离子电电极材料研究新进展.ppt

What’are the major players of the cathode materials Electrode materials 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…. Li2MnSiO4正极材料循环性能的研究 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?? What’s the reaction step and mechanism for mixed system, i.e. Li2Fe1-xMnxSiO4 (0 ≤x≤1) In-situ or ex-situ XAS, Solid MAS NMR, Mossbauer …… In-situ Mn K-edge XANES spectra during the first charging process 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, * * * At our synthesis conditions, two modifications of Li2CoSiO4 (βⅡ, and βⅠ) which are derivatives of low temperature Li3PO4 were obtained. a: βⅡ; Oorthorhombic and space-group Pmn21. b: βⅠ orthorhombic The XRD profiles of the Li2CoSiO4 powers prepared at different conditions. Co-silicates-- Li2CoSiO4 L. Gong, Y. X. Li, Y. Yang; J Power Sources, 2007, 174(2), 524-527, S. Q. Wu, J. H. Zhang,