1、1 Exploration research of new cathode materials with high capacity for Li-ion batteryYong YangState Key Lab of Physical Chemistry of Solid Surface, Xiamen UniversityChina2Whatare the major players of the cathode materials Electrode materialsHigh energy densityHigh power densityLayered oxide cathode

2、materialsPolyanion: LFePO4, Spinel, LiMn2O4High energy densityLi2FeMnSiO4;Organic-typeFluorides3Further improvement of layered oxide-based cathode materials1) Nickel-based layered cathode materials:Lattice-dopingSurface coating1) H. S. Liu, et al ; Electrochimica Acta, 2004, 49:1151-1159; Solid Stat

3、e Ionics, 2004, 166:317-3252) 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

4、systems.4LiLi(1-x)/3Mn(2-x)/3Nix/3Co3/xO2 Cathode0501001502002503002.02.53.03.54.04.5Voltage / VSpecific Capacity / mAh/g pristine AlF3 coating0.1 CCharge/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 LiCoO2.0501001502002503003502.02

5、.53.03.54.04.55.02nd249 mAh/g324.5 mAh/gVoltage / V as-prepared1stCapacity / mAh/g5Layered Oxide-type Cathode MaterialsGas evolution, e.g. O2, CO2High capacity cathode materialsCharging to high voltage 6050100150200250300350-0.50.00.51.01.52.02.53.03.03.54.04.55.0AlF3-coatedVoltage / VIon current /

6、10-11 A/gTime / minO2(m/e = 32)050100150200250300350-0.50.00.51.01.52.02.53.03.03.54.04.55.0O2Voltage / VIon current / 10-11 A/gTime / min(m/e = 32)pristine0501001502002503003500123453.03.54.04.55.0Voltage / VIon current / 10-11 A/gTime / minCO2(m/e = 44)AlF3-coated0501001502002503003500123453.03.54

7、.04.55.0(m/e = 44)Voltage / VIon current / 10-11 A/gTime / minpristineCO2 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.1/45 times7Advantages: Low cost excellent thermal stability

8、 no oxygen evolved at low amount Li+ intercalatedDisadvantages: Lower capacity and low electronic conductivityPhosphate 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 cat

9、hode materials in lithium-ion batteries8Olivine 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

10、anion is expected.910A novel cathode materials with more than one electron exchange: Li2MnSiO4 Rietveld plot of Li2MnSiO4/C composite.102030405060708090010002000300040005000600070008000900010000intensity2theta (deg) obs cal diffRF=3.14%RWP=4.21%orthorhombicPmn21a = 6.308(3) b = 5.377(7) c = 4.988(9)

11、 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 20501001502002503001.01.52.02.53.03.54.04.55.0 150 mA/g 30 mA/g 5 mA/gVoltage/V vs. Li+/Li Specific Capacity/mAhg-111Li2MnSiO4正極材料循環性能的研正極材料循環性能的研究究0501001502002501.21.41.61.82.02.22.42.

12、62.83.03.23.43.63.84.04.24.44.64.85.0 Votage / VCapacity / mAhg-1 a 1 cycle b 5 cycles c 10 cycles d 20 cycles e 40 cyclesabcdei=30mAg-10102030406080100120140160180200220240 充電放電Capacity/mAhg-1Cycle Numberi=30mAg-1Cyclic stability of Li2MnSiO4 material is poor!12The first charge/discharge profiles o

13、f 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) A542.0501001502002501.01.52.02.53.03.54.04.55.0d cba Voltage/V vs. Li+/LiSpecific capacity/mAh/gea:x=0.9b:x=0.7c:x=0.5d:x=0.2e:x=0 A capacity of 214 mAh/g (86% of the theoreti

14、cal capacity, 1.29 electrons per unit formula) was achieved for Li2MnxFe1-xSiO4 (x = 0.5) sample .Li2Mn1-xFexSiO4/C13 Cyclic performance of improved Li2Mn0.5Fe0.5SiO4 02468101214161820050100150200250300350 Cycle number Charge DischargeCapacity/mAh/gCurrent density：10mA/g (C/16)， Temperature：30 oC144

15、00030002000100004550556065707580859095100105110/cm-1 1 cycle 3 cycles 5 cycles10cycles 20 cycles 40 cycles4788709701431870cm-1 SiO44-40003500300025002000150010005000.400.350.300.250.200.150.100.050.00Wavenumbers /cm-1Intensity 73589010301115 abcdefcycle number:a:0, b:1, c:5, d:10, e:20, f:40SiO44-Si

16、O44-SiO32-15Charge 140mAh/gCharge 100mAh/gLi2MnSiO4(yx)ppm500-50-100-150-200Solid MAS 7Li NMR of Li2MnSiO4 at different charged statesFrom ex-situ NMR spectra, it is proposed that the rate of deintercalation of Li+ at different sites are different, and some Li2SiO3 are newly formed16Questions Can we

17、 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-sit

18、u XAS, Solid MAS NMR, Mossbauer 17XRD pattern of Li2Fe0.5MnSiO4SEM images of Li2Fe0.5Mn0.5SiO4Structure and morphology of Li2Fe0.5Mn0.5SiO4/C180501001502002503003501.52.02.53.03.54.04.55.0 1st cycle 2nd cycleVoltage(V)Specific capacity (mAh/g)i = 5 mA/g 0501001502002501.01.52.02.53.03.54.04.55.0 1st

19、 cycle 2nd cycleVoltage(V)Specific capacity (mAh/g)i = 10 mA/g 0501001502001.01.52.02.53.03.54.04.55.0 1st cycle 2nd cycleVoltage(V)Specific capacity (mAh/g)i = 150 mA/g Electrochemical performances of Li2 Fe0.5Mn0.5SiO4The initial two cycles at 5 mA/g between 1.5 and 4.8 V.The initial two cycles at

20、 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.1901234567891011050100150200250 5 mA/g 10 mA/g150 mA/g Li2MnSiO4 at 5 mA/gSpecific capacity (mAh/g)Cyclic numberCyclic performances of Li2Fe0.5Mn0.5SiO4 at 5, 10 and 150 mA/g, and Li2MnSiO4 at 5 mA/g200306090 120

21、 150 180 210 240 270 3001.62.02.42.83.23.64.04.44.8jihfgbedcVoltage(V)Specific capacity (mAh/g)ai=20 mA/g, 1.5-4.8 VElectrode Reaction Mechanism Study- In-situ XANESThe first charge-discharge curves of Li2Fe0.5Mn0.5SiO4 during in-situ measurementSSRF Shanghai, China上海同步輻射光源上海同步輻射光源217110712071307140

22、715071600.00.40.81.21.62.0 Li2Mn0.5Fe0.5SiO4 charge 3.8 V charge 4.2 V charge 4.6 V charge 4.8 V FeO Fe2O3 Absorption Coefficient (a.u.) Energy (eV)In-situ Fe K-edge XANES spectra during the first charging process2265406550656065706580659066000.00.51.01.5654065456550655565600.00.30.60.91.21.5 Li2Fe0

23、.5Mn0.5SiO4 charge 3.8 V charge 4.2 V charge 4.6 V charge 4.8 V MnO Mn2O3 Absorption Coefficient (a.u.) Energy (eV) Absorption Coefficient (a.u.) Energy (eV) Li2Fe0.5Mn0.5SiO4 charge 3.8 V charge 4.2 V charge 4.6 V charge 4.8 V MnO Mn2O3In-situ Mn K-edge XANES spectra during the first charging proce

24、ss236545.06545.56546.06546.56547.06547.56548.06548.56549.06549.56550.01.2 1.8 2.4 3.0 3.6 4.2 4.87120.07120.57121.07121.57122.07122.57123.07123.57124.07124.57125.0 Absorption edge (eV) Absorption edge (eV)Step voltage (V) Fe K edgeFeO (7120.37 eV)Fe2O3(7123.08 eV)charge4.8 4.2 3.6 3.0 2.4 1.8 1.2 Mn

25、 K edge discharge MnO (6545.37 eV)Mn2O3(6548.74 eV)Evolution of absorption edge of Fe and Mn of Li2Mn0.5Fe0.5SiO4 in the first charging and discharging processes.24Nano-structured Li2FeSiO4 with excellent rate capabilities and cyclic stability102030405060708090 2 Theta (o)Space group:OrthorhombicPmn

26、21 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). 25Nanostructured characteristic of the Li2FeSiO4 make it as high-rate cathode materials feasible26The inv

27、erse 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.27Electroch

28、emical performance of the Li2FeSiO4 cathodes at different cycles0501001502001.01.52.02.53.03.54.04.55.0 1st 2nd 10th Specific capacity (mAh/g)Voltage (V)1.54.8 V versus Li+/Li; 1/16 CZ. L. Gong, Y. X. Li, G. N. He, J. Li, Y. Yang* Electrochem. Solid State Lett., 11, A60-63 (2008). 2805010015012345C/

29、1610 C 5 C2 C Specific capacity (mAh/g)Voltage (V)C/1610 C5 C2 CExcellent rate-performance of the silicate cathode materialsZ. 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 c

30、arbon connection.2901020304050020406080100120140160180200 2 C 5 C10 C Cycle numberDischarge Capacity (mAh/g)Excellent cyclic stability of Li2FeSiO40204060800204060801001201401601802002C10C Cycle numberDischarge Capacity (mAh/g)2C5C30050100 150 200 250 300 350 400 450-10-8-6-4-20246810 ExoDSC/(mW/mg)

31、Temperature/oC uncycle Charge to 4.8 VLi2FeSiO4+ElectrolyteNo extra heat give off during heating process!31 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 Th

32、e 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, 61132The temperature dependence of the inverse molar magnetic

33、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 property33Galvanostatic chargedischarge curves for Li2CoSiO4-based cathodes at current rate 16 mA/g. Electrochemical performance34space-group: Pmn21SiO4 -

34、 MO4LiO4SiO4 - MO4Corrugated layerStructure of Li2MSiO4Reference:1)S.Q.Wu, et al; Computational Materials Science, 2009, 44, 1243-1251 O Co - OO Si - O35 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