Impact of Structure and Defect Modification on Vanadium Oxide For
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Impact of Structure and Defect Modification on Vanadium Oxide for Alkali-ion Battery Electrodes Evan Uchaker A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Washington 2015 Reading Committee: Professor Guozhong Cao, Chair Professor Lucien N. Brush Professor Jihui Yang Program Authorized to Offer Degree: Materials Science and Engineering c Copyright by Evan Uchaker, 2015. All rights reserved. University of Washington Abstract Impact of structure and defect modification on vanadium oxide for alkali-ion battery electrodes Evan Uchaker Chair of the Supervisory Committee: Professor Guozhong Cao Materials Science and Engineering The proliferation of portable electronics and electric vehicles paired with the updating of an antiquated grid system has driven the rapid progression of improved technologies related to energy distribution and storage. However, energy storage materials and devices have come to be viewed as a crux impeding advanced device development. Alkali-ion, namely lithium and sodium, batteries are a robust technology that has seen gains in performance based on materials chemistry over the past several decades. Despite years of intensive research ac- companied with significant progress, the cathode remains a limiting factor towards improved battery performance because of its low capacity and exasperated degradation over long term cycling; the cathode is also one of the most expensive material components of the overall cell. Thus, research concerning new cathode material development and the improvement of already well-established cathode materials should be a top priority. Within this context, vanadium oxide is an ideally suited model material showcasing how structural or chemical alterations can have tremendous impact on device performance. As a means towards improving electrochemical performance, the role of kinetics and thermodynamics were investigated through structural and defect chemistry manipulation in the vanadium oxide system. Structural modification, as a means towards achieving kinetic stabilization, can be utilized to develop electrodes with the chemical stability of microsized iii particles that simultaneously exploit the beneficial properties associated with nanoparticles. Defect modification is a powerful means towards improving material intercalation capabilities by reducing the stress and localized electrostatic contributions which directly alter the mi- gration energy and diffusion barriers the alkali-ion must overcome. Lithium-ion was chosen for structural (kinetic) examination as it is a mature technology that has been extensively investigated; sodium-ion was chosen for defect manipulation because the larger size and dif- ferent transport characteristics of sodium ions influence the thermodynamic (and to a lesser extent the kinetic properties) of sodium-ion batteries, and can lead to unexpected electro- chemical behavior. The findings gained are by no means limited to the originally investigated systems, and should be taken into consideration for an assortment of electrode materials. iv Contents Abstract . iii Acknowledgements . v List of Tables . xi List of Figures . xii 1 Motivation and Context 1 1.1 Energy Demands . 1 1.2 Energy Storage Systems . 2 1.2.1 Mechanical Energy Storage . 3 1.2.2 Electrochemical Energy Storage . 4 1.3 Scope and Objective . 12 2 Alkali-ion Battery 16 2.1 Overview . 16 2.1.1 Li-ion Battery . 19 2.1.2 Na-ion Battery . 20 2.2 Electrode Thermodynamics . 21 2.2.1 Governing Thermodynamic Considerations . 22 2.2.2 Gibbs Phase Rule . 24 2.3 Electrode Kinetics . 25 2.3.1 Arrhenius Relation . 25 vii 2.3.2 Nernst Equation and Tafel Equation on Electrodes . 26 2.3.3 Marcus Theory of Electron Transfer . 27 2.3.4 Fick's Laws . 29 2.3.5 Electrolyte Conductivity . 30 2.3.6 Tortuosity in Porous Electrodes . 30 2.4 Electrode Material Selection . 31 2.4.1 Solid Electrolyte Interphase . 35 2.5 Electrode Material Performance . 36 2.5.1 Performance Metrics . 39 2.5.2 Overview of Vanadium Oxide . 42 3 Nanostructured Electrodes for Rechargeable Battery 50 3.1 Introduction . 51 3.2 Exposure of Specific Surface Facets . 56 3.3 Micro/nano-structured Electrode Materials . 60 3.4 Hollow micro/nano-structures . 62 3.4.1 Mesocrystals . 69 3.4.2 Vanadium Oxide . 71 3.4.3 Titanium Oxide . 72 3.4.4 Lithium Iron Phosphate . 74 3.5 Surface Chemistry and Defects . 76 3.5.1 Surface Modification . 76 3.5.2 Role of Defects . 78 3.6 Limitations of Nanostructured Electrode Materials for Li-ion Batteries . 81 3.7 Remarks . 85 4 Polyol-mediated Solvothermal Synthesis and Electrochemical Performance of Nanostructured V2O5 Hollow Microspheres 87 viii 4.1 Introduction . 88 4.2 Experimental Procedure . 90 4.2.1 Materials and Synthesis . 90 4.2.2 Characterization . 90 4.2.3 Electrochemical Measurements . 91 4.3 Results and Discussion . 91 4.4 Conclusions . 102 5 Enhanced Intercalation Dynamics and Stability of Engineered Micro/nano- structured Electrode Materials: Vanadium Oxide Mesocrystals 104 5.1 Introduction . 105 5.2 Experimental Procedure . 107 5.2.1 Materials and Synthesis . 107 5.2.2 Characterization . 107 5.2.3 Electrochemical Measurements . 108 5.3 Results and Discussion . 108 5.4 Conclusions . 120 6 Amorphous Vanadium Oxide Electrode for Sodium-Ion Battery 121 6.1 Introduction . 122 6.2 Experimental Procedure . 124 6.2.1 Gel Synthesis . 124 6.2.2 Deposition . 125 6.2.3 Characterization . 125 6.2.4 Electrochemical Analysis . 126 6.3 Results and Discussion . 127 6.4 Conclusions . 145 ix 7 Elucidating the Role of Defects in Sodium Vanadium Oxide for use as Sodium Ion Battery Electrode 146 7.1 Introduction . 147 7.2 Experimental Procedure . 150 7.2.1 Material Synthesis . 150 7.2.2 Characterization . 150 7.2.3 Electrochemical Analysis . 151 7.3 Results and Discussion . 152 7.4 Conclusions . 166 8 Conclusions 168 Bibliography 171 x List of Tables 1.1 Range for total system levelized costs of new generation resources, (2012 USD/MWh). 2 2.1 Comparative qualities of lithium, sodium, and potassium for alkali-ion battery application. 18 5.1 Primary facet surfaces and corresponding dangling bond energy upon cleaving (surface relaxation effects not considered). 117 5.2 Computed surface energies (γ) for the un/relaxed low-index surfaces of VO2(B) and their fractional abundance. 118 6.1 Comparison of metallic lithium and sodium. 123 6.2 FTIR peak position data for the as-processed, 180◦C/vac annealed, and ◦ 450 C/air annealed V2O5 samples. 132 6.3 XPS peak fit values for the as-processed, 180◦C/vac annealed, and 450◦C/air annealed V2O5 samples. 134 7.1 Physical properties of NaxV3O8 products with deficient, ideal, and excess sodium stoichiometry. 153 7.2 Rietveld refinement of NaxV3O8 products with deficient, ideal, and excess sodium stoichiometry. 156 7.3 FTIR peak locations of NaxV3O8 products with deficient, ideal, and excess sodium stoichiometry. 157 xi List of Figures 1.1 Application range of different energy storage technologies based on power output and energy stored. 3 1.2 Comparison of the different battery technologies in terms of gravimetric and volumetric energy density. 7 2.1 Abundance (atom fraction) of the chemical elements in Earth's upper conti- nental crust as a function of atomic number. 17 2.2 Schematic illustration of a typical alkali-ion cell and simplified charge processes. 18 2.3 Material cost breakdown for a typical 96 Wh PHEV cell. 20 2.4 Periodic palette available for the design of new electrode materials. 32 2.5 Schematic illustration of the open-circuit energy diagram for a typical alkali- ion electrochemical cell. 34 2.6 Proposed schematic of the SEI layer with the left most edge representing the interface with the electrode surface. 36 2.7 A schematic representation of the different reaction mechanisms observed in electrode materials for alkali-ion batteries. 37 2.8 Voltage versus capacity for LIB electrode materials. 40 2.9 Voltage versus capacity for NIB electrode materials. 40 2.10 The colorful oxidation states of vanadium, increasing from left to right. 43 2.11 Coordination geometries of vanadium species. ..