高容量锂离子电池电极材料研究的新进展.ppt

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 Whatare the major players of the cathode materials Electrod e material s High energy density High power density Layered oxide cathode 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; 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. High-CapacityHigh-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. 0.1 C0.1 CBare Bare AlFAlF 3 3 -coated-coated Charge Charge ( (mAh/gmAh/g) ) 324.5324.5314.0314.0 Discharge Discharge ( (mAh/gmAh/g) ) 249249263.1263.1 ICL (ICL (mAh/gmAh/g) )75.575.550.950.9 Layered Oxide-type Cathode Materials High energy High energy density density batteriesbatteries Layered oxide cathode materials Layered oxide cathode materials LiLi 2 2 MnOMnO 3 3 . . LiNiLiNi x x CoCo y y MnMn1-x-y 1-x-y O O2 : 2 : 270mAh/g or even higher, 270mAh/g or even higher, Gas evolution, e.g. O2, CO2 High capacity cathode materials Charging to high voltage In-situ Electrochemical Mass spectroscopic In-situ Electrochemical Mass spectroscopic techniques and Its use in Li-ion batteriestechniques and Its use in Li-ion batteries AlF3 coating layer provides a buffer layer to make oxygen atoms with high 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+ 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 Olivine type: LiMPO4 (PO4)3- Orthosilicates: Li2MSiO4 (SiO4)4- The redox potential of Mn+/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. Why do we choose Silicates ? Why do we choose Silicates ? orthosilicateorthosilicate materials ( materials (LiLi 2 2 MSiOMSiO 4 4): ): Two lithium ionsTwo lithium ions should be reversible extracted or inserted in should be reversible extracted or inserted in principle without distinctively changes of the crystal principle without distinctively changes of the crystal structurestructure . . Theo. (mAh g-1)Exp. (mAh g-1) LiCoO2274140 LiNiO2275200 LiNi1-xCoxO2275170180 LiNi1/2Mn1/2O2280180190 LiFePO4170150 Li2FeSiO4331165 Li2MnSiO4333209 (1st cycle) Li2MnxFe1-xSiO4332235 (x=0.5) 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 200610005329 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. A capacity of 214 mAh/g (86% of the theoretical capacity, 1.29 electrons per unit formula) was achieved for Li2MnxFe1-xSiO4 (x = 0.5) sample . Li2Mn1-xFexSiO4/C Cyclic performance of improved Li2Mn0.5Fe0.5SiO4 Current density： 10mA/g (C/16)， Temperature：30 oC CapacityCapacity（mAh/gmAh/g) ) The changes in Valence The changes in Valence of of MnMn ions ions LiLi 2 2 MnSiOMnSiO 4 4 209209+2+2 +3.25 +3.25 LiLi 2 2 MnMn0.5 0.5Fe Fe0.5 0.5SiO SiO 4 4 235235+2+2 +3.84+3.84 Evidence for fading mechanism of LiEvidence for fading mechanism of Li 2 2 MnSiOMnSiO 4 4 870cm-1 SiO44- SiO44- SiO44- SiO32- Solid MAS 7Li NMR of Li2MnSiO4 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 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 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 1.5 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 charge-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 in the 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 Structure, Morphology and Microstructure of Carbon-coated LiCarbon-coated Li 2 2 FeSiOFeSiO 4 4 Nanostructured characteristic of the Li2FeSiO4 make it as high- rate cathode materials feasible 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 Li2FeSiO4 below TN = 20 K. The curve agree well with Curie-Weiss law in the whole paramagnetic region. Electrochemical performance of the Li2FeSiO4 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). 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: Porous nanostructure, and improved electronic conductivity through carbon connection. Excellent cyclic stability of Li2FeSiO4 Excellent thermal stabilityExcellent thermal stability No extra heat give off during heating process! At our synthesis conditions, two modifications of Li2CoSiO4 (, and ) which are derivatives of low temperature Li3PO4 were obtained. a: ; Oorthorhombic and space- group Pmn21. b: 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, Z. Z. Zhu and Y. Yang, Curr. Appl. Phys. 2007, 7, 611 The temperature dependence of the inverse molar magnetic susceptibility 1/m for Li2CoSiO4 powers prepared at 873 K. The magnetization curves M (H) at 2 K for Li2CoSiO4 powers prepared at 873 K. Magnetic property Galvanostatic chargedischarge curves for Li2CoSiO4-based cathodes at current rate 16 mA/g. Electrochemical performance space-group: Pmn21 SiO4 - MO4 LiO4 SiO4 - MO4 Corrugated layer First-principles investigations on the First-principles investigations on the structural and electronic propertiesstructural and electronic properties Structure of Li2MSiO4 Reference: 1) S.Q.Wu, et al; Computational Materials Science, 2009, 44, 1243-1251 O Co - O O Si - O ConclusionsConclusions A series of silicates cathode materials such as Li2FeSiO4, LiFexMn1-xSiO4, Li2CoSiO4 with and without carbon coating have been synthesized, some of them could achieve more than 1-1.6 Li+ reversible exchange. e.g. Li2Mn0.5Fe0.5SiO4 with 235 mAh/g has been achieved. We have made a carbon-coated nanostructured Li2FeSiO4 material with excellent rat