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V.B.7 The Role of Surface Chemistry on the Cycling and Rate Capability of Lithium Positive Electrode Materials (MIT) Yang Shao-Horn Massachusetts Institute of Technology, 3-344 Mechanical Engineering and Materials Engineering 77 Massachusetts Avenue Cambridge, MA 02139 Phone: (617) 253-2259; Fax: (617) 258-7018 E-mail: shaohorn@mit.edu Subcontractor: A.N. Mansour, NSWCCD, West Bethesda, MD Start Date: June 1, 2010 Projected End Date: December 31, 2011 Objectives · Develop a fundamental understanding of processes associated with the interfacial instability between active materials and electrolyte. · Design low cost positive electrodes with stable electrode-electrolyte interface with improved cycling performance and rate capability over wider operating temperatures. · Develop a fundamental understanding of the role of catalyst on performance parameters of Li-O 2 cells. Technical Barriers This project addresses the following technical barriers in relation to positive electrode materials for lithium-ion batteries: (A) High Cost (B) Poor cycle life (C) Low specific energy (D) Abuse tolerance Technical Targets · PHEV: Specific energy 56-96 Wh/kg; Specific power 316-750 W/kg; 15-year life (40°C); 3,000-5,000 cycles · EV: Specific energy 200 Wh/kg; 1,000 cycles Accomplishments · Cycled bare LiCoO 2 and “AlPO 4 ”-coated LiCoO 2 electrodes in lithium cells with 1 M of LiPF 6 and 1M LiClO 4 in EC:DMC and characterized the surface chemistry by XPS using conventional Al X-rays (1487 eV) and monochromatic synchrotron X-rays (2555 eV) to increase the depth of the analyzed region. · Characterized the discharge products of cathodes and the role of catalysts in Li-O 2 cells by conventional Al X-rays and monochromatic synchrotron X-rays. · Evaluated the electrochemical activities of Li-rich (Li 2 O) x .(MO 2 ) y (where M = Mn, Co, Ni, etc.) system and improved the electrochemical activity by the application of non-precious Co 3 O 4 nanoparticles. · Characterized the atomic structure of layered-layered 0.5Li 2 MnO 3 +0.5LiNi 0.44 Co 0.25 Mn 0.31 O 2 composite materials by TEM (collaboration with M.M. Thackeray). Introduction Achieving a fundamental understanding of the role of coatings and synthesis conditions on the surface chemistry and structural integrity of positive electrode materials is necessary to design stable surfaces and structures for Liion batteries. The design of chemically and structurallystable surfaces of Li storage materials is key to the development of low cost, high-energy, high-power, longlife, and thermally-stable Li rechargeable batteries. Approach · Probe the surface chemistry of positive electrode materials before and after cycling using surfacesensitive electron microscopy, angle resolved X-ray photoelectron spectroscopy and electron-yield X-ray adsorption spectroscopy. · Study the bulk structure of positive electrode materials before and after cycling using synchrotron X-ray diffraction and transmission X-ray absorption spectroscopy. · Correlate surface chemistry and bulk structure information with electrochemical performance characteristics such as capacity retention and rate capability to determine the origin of surface instability. FY 2011 Annual Progress Report 495 Energy Storage R&D
V.B.7 Role of Surface Chemistry on the Cycling and Rate Capability of Li Positive Electrode Materials (MIT) Shao-Horn – MIT Apply the fundamental understanding gained from the project to design stable surfaces to improve the cycle life and efficiency of Li rechargeable batteries. Results Interfacial stability of “AlPO 4 ”-Coated LiCoO 2 . Our previous research has shown 1) that “AlPO 4 ” coating can induce fluoride formation in the cycled electrode with LiPF 6 -containing electrolyte and reduce the growth of high-impedance organic layer during cycling. To determine the role of the salt contribution toward the formation of metal fluorides, bare and “AlPO 4 ”-coated LiCoO 2 electrodes were cycled 20 times in 1 M LiPF 6 or LiClO 4 in EC:DMC (1:1) at the C/5 rate between 2.0-4.6 V vs. Li (V Li ) with 4 hour hold at 4.6 V Li . The coated electrodes cycled in LiPF 6 demonstrate higher capacity retention compared to electrodes cycled in LiClO 4 , as shown in Figure V - 30. Hence, the coating does not provide an advantage when cycling was performed in LiClO 4 electrolyte, which supports the hypothesis that the promotion of metal fluoride on the coated electrode surface with LiPF 6 salt is responsible for the improved capacity retention observed previously. It is interesting to note that the bare electrode cycled in LiClO 4 has higher capacity retention than the bare electrode cycled in LiPF 6 or the coated electrode cycled in LiClO 4 , as shown in Figure V - 31. The origin is currently not understood. 5.0 4.5 20th 10th 5th 5.0 4.5 E [ V vs. Li ] 4.0 3.5 3.0 15th 1st E [ V vs. Li ] 15th 20th 2.5 2.5 Coated LiCoO 2 -LiPF 6 Coated LiCoO 2 -LiClO 4 2.0 2.0 0 50 100 150 200 250 0 50 100 150 200 250 Q [mAh/g] Q [mAh/g] 4.0 3.5 3.0 10th 5th 1st Figure V - 30: Voltage capacity profiles for "AlPO4" -coated LiCoO2 electrodes cycled in lithium cells with LiPF6 and LiClO4 in EC:DMC, C/5. 5.0 5.0 4.5 4.5 E [ V vs. Li ] 4.0 3.5 3.0 10th 15th 20th 5th 1st E [ V vs. Li ] 10th 5th 15th 2.5 2.5 Bare LiCoO 2 -LiPF Bare LiCoO 6 2 -LiClO 4 2.0 2.0 0 50 100 150 200 250 0 50 100 150 200 250 Q [mAh/g] Q [mAh/g] 4.0 3.5 3.0 20th 1st Figure V - 31: Voltage capacity profiles for bare LiCoO2 electrodes cycled in lithium cells with LiPF6 and LiClO4 in EC:DMC, C/5. In an effort to increase the depth of information region increased from ~4 to ~11 nm for photoelectrons analyzed by XPS, we have taken advantage of synchrotron associated with the Co 2p region. Half of each electrode radiation on beamline X24A at NSLS and collected the was analyzed by conventional X-rays while the other half spectra utilizing monochromatic X-rays with energy of was analyzed using synchrotron X-rays. The spectra 2555 eV compared to conventional Al K α X-rays with collected with conventional X-rays are consistent with energy of 1487 eV. In this way, the depth of the analyzed spectra reported earlier and will not be shown here. The Energy Storage R &D 496 FY 2011 Annual Progress Report
Page 1 and 2: V. FOCUSED FUNDAMENTAL RESEARCH Int
Page 3 and 4: V.A Introduction Duong - DOE, Srini
Page 5 and 6: V.B Cathode Development V.B.1 First
Page 7 and 8: V.B.1 First Principles Calculations
Page 9 and 10: V.B.1 First Principles Calculations
Page 11 and 12: V.B.2 Cell Analysis, High-energy De
Page 13 and 14: V.B.3 Olivines and Substituted Laye
Page 19 and 20: V.B.4 Stabilized Spinels and Nano O
Page 21 and 22: V.B.4 Stabilized Spinels and Nano O
Page 23 and 24: V.B.5 The Synthesis and Characteriz
Page 25 and 26: V.B.5 Synthesis & Characterization
Page 27 and 28: V.B.6 Cell Analysis-Interfacial Pro
Page 29: V.B.6 Cell Analysis-Interfacial Pro
Page 33 and 34: V.B.7 Role of Surface Chemistry on
Page 39 and 40: V.B.8 Characterization of New Catho
Page 41 and 42: V.B.8 Characterization of New Catho
Page 43 and 44: V.B.9 Layered Cathode Materials (AN
Page 49 and 50: V.B.10 Development of High Energy C
Page 51 and 52: V.B.10 Development of High Energy C
Page 53 and 54: V.B.11 Crystal Studies on High-ener
Page 59 and 60: V.B.12 Developing Materials for Lit
Page 65 and 66: V.B.13 Studies on the Local SOC and
Page 67 and 68: V.B.13 Studies on the Local SOC and
Page 69 and 70: V.B.14 New Cathode Projects (LBNL)
Page 71 and 72: V.C.1 Nanoscale Composite Hetero-st
Page 73 and 74: V.C.1 Nanoscale Composite Hetero-st
Page 75 and 76: V.C.2 Interfacial Processes - Diagn
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V.C.3 Search for New Anode Material
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V.C.4 Nano-structured Materials as
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V.C.4 Nano-structured Materials as
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V.C.5 Development of High Capacity
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V.C.5 Development of High Capacity
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V.C.6 Advanced Binder for Electrode
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V.C.6 Advanced Binder for Electrode
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V.C.7 Three-Dimensional Anode Archi
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ARGONNE2_CDJ403T me Pro ile V.C.7 T
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V.C.8 Metal-Based High-Capacity Li-
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V.C.8 Metal-Based High-Capacity Li-
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V.C.9 New Layered Nanolaminates for
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V.C.9 New Layered Nanolaminates for
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V.C.10 Atomic Layer Deposition for
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V.C.10 Atomic Layer Deposition for
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V.C.11 Synthesis and Characterizati
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V.C.11 Polymer-Coated Layered SiOx-
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V.C.12 Synthesis and Characterizati
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V.C.12 Silicon Clathrates for Anode
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V.C.12 Silicon Clathrates for Anode
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V.C.13 Wiring Up Silicon Nanopartic
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V.C.13 Wiring Up Silicon Nanopartic
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V.C.14 Hard Carbon Materials for Hi
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V.C.14 Hard Carbon Materials for Hi
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V.D.1 Polymer Electrolytes for Adva
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V.D.1 Polymer Electrolytes for Adva
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V.D.2 Interfacial Behavior of Elect
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V.D.2 Interfacial Behavior of Elect
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V.D.3 Molecular Dynamics Simulation
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V.D.3 Molecular Dynamics Simulation
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V.D.4 Bi-functional Electrolytes fo
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V.D.4 Bi-functional Electrolytes fo
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V.D.5 Advanced Electrolyte and Elec
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V.D.6 Inexpensive, Nonfluorinated (
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V.D.6 Nonfluorinated (or Partially
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V.D.7 Development of Electrolytes f
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V.D.8 Sulfones with Additives as El
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V.D.8 Sulfones with Additives as El
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V.D.9 Long-lived Polymer Electrolyt
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V.E Cell Analysis, Modeling, and Fa
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V.E.1 Electrode Fabrication and Fai
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V.E.2 Modeling-Thermo-electrochemis
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V.E.2 Thermo-electrochemistry, Capa
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V.E.3 Intercalation Kinetics and Io
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V.E.4 Mathematical Modeling of Next
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V.E.5 Analysis and Simulation of El
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V.E.5 Analysis and Simulation of El
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V.E.6 Investigation of Critical Par
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V.E.6 Investigation of Critical Par
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V.E.7 Predicting/Understanding New
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V.E.8 New Electrode Designs for Ult
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V.E.8 New Electrode Designs for Ult
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V.E.9 In Situ Electron Spectroscopy
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V.E.9 In situ Electron Spectroscopy
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V.F.1 Energy Frontier Research Cent
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V.F.1 Energy Frontier Research Cent
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V.F.2 Novel In Situ Diagnostics Too
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V.F.2 Novel In Situ Diagnostics Too
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V.G Integrated Lab-Industry Researc
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