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A GUIDE TO LITHIUM-SULFUR BATTERIES THAT EXPLORES THEIR MATERIALS, ELECTROCHEMICAL MECHANISMS AND MODELLING, AND INCLUDES RECENT SCIENTIFIC DEVELOPMENTS Lithium-Sulfur Batteries offers a comprehensive examination of Lithium-Sulfur (Li-S) batteries from the viewpoint of the materials used in their construction, the underlying electrochemical mechanisms and how this translates into the characteristics of Li-S batteries. The authors - noted experts in the field - outline the approaches and techniques required to model Li-S batteries. Lithium-Sulfur Batteries reviews the application of Li-S batteries for commercial use and explores many broader issues including the development of battery management systems to control the unique characteristics of Li-S batteries. The authors include information on sulfur cathodes, electrolytes and other components used in making Li-S batteries and examine the role of lithium sulfide, the shuttle mechanism and its effects, and degradation mechanisms. The book contains a review of battery design and: Discusses electrochemistry of Li-S batteries and the analytical techniques used to study Li-S batteries Offers information on the application of Li-S batteries for commercial use Distills years of research on Li-S batteries into one comprehensive volume Includes contributions from many leading scientists in the field of Li-S batteries Explores the potential of Li-S batteries to power larger battery applications such as automobiles, aviation and space vehicles Written for academic researchers, industrial scientists and engineers with an interest in the research, development, manufacture and application of next generation battery technologies, Lithium-Sulfur Batteries is an essential resource for accessing information on the construction and application of Li-S batteries.

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A GUIDE TO LITHIUM-SULFUR BATTERIES THAT EXPLORES THEIR MATERIALS, ELECTROCHEMICAL MECHANISMS AND MODELLING, AND INCLUDES RECENT SCIENTIFIC DEVELOPMENTS Lithium-Sulfur Batteries offers a comprehensive examination of Lithium-Sulfur (Li-S) batteries from the viewpoint of the materials used in their construction, the underlying electrochemical mechanisms and how this translates into the characteristics of Li-S batteries. The authors - noted experts in the field - outline the approaches and techniques required to model Li-S batteries. Lithium-Sulfur Batteries reviews the application of Li-S batteries for commercial use and explores many broader issues including the development of battery management systems to control the unique characteristics of Li-S batteries. The authors include information on sulfur cathodes, electrolytes and other components used in making Li-S batteries and examine the role of lithium sulfide, the shuttle mechanism and its effects, and degradation mechanisms. The book contains a review of battery design and: Discusses electrochemistry of Li-S batteries and the analytical techniques used to study Li-S batteries Offers information on the application of Li-S batteries for commercial use Distills years of research on Li-S batteries into one comprehensive volume Includes contributions from many leading scientists in the field of Li-S batteries Explores the potential of Li-S batteries to power larger battery applications such as automobiles, aviation and space vehicles Written for academic researchers, industrial scientists and engineers with an interest in the research, development, manufacture and application of next generation battery technologies, Lithium-Sulfur Batteries is an essential resource for accessing information on the construction and application of Li-S batteries.

Author Biography

DR. MARK WILD is Senior Production Manager at OXIS Energy, leading a diverse team manufacturing electrolytes and electrodes for Lithium Sulfur pouch cells, but involved in all aspects of developing this new technology. OXIS Energy is a UK SME devoted to the global commercialization of Lithium–Sulfur batteries. DR. GREGORY J. OFFER is Reader in the Department of Mechanical Engineering at Imperial College London. He leads a group of researchers working on understanding and using electrochemical devices.

Table of Contents

Preface xiii Part I Materials 1 1 Electrochemical Theory and Physics 3
Geraint Minton 1.1 Overview of a LiS cell 3 1.2 The Development of the Cell Voltage 5 1.2.1 Using the Electrochemical Potential 7 1.2.2 Electrochemical Reactions 10 1.2.3 The Electric Double Layer 13 1.2.4 Reaction Equilibrium 15 1.2.5 A Finite Electrolyte 17 1.2.6 The Need for a Second Electrode 17 1.3 Allowing a Current to Flow 19 1.3.1 The Reaction Overpotential 20 1.3.2 The Transport Overpotential 21 1.3.3 General Comments on the Overpotentials 22 1.4 Additional Processes Which Define the Behavior of a LiS Cell 22 1.4.1 Multiple Electrochemical Reactions at One Surface 22 1.4.2 Chemical Reactions 23 1.4.3 Species Solubility and Indirect Reaction Effects 25 1.4.4 Transport Limitations in the Cathode 25 1.4.5 The Active Surface Area 26 1.4.6 Precipitate Accumulation 27 1.4.7 Electrolyte Viscosity, Conductivity, and Species Transport 27 1.4.8 Side Reactions and SEI Formation at the Anode 28 1.4.9 Anode Morphological Changes 29 1.4.10 Polysulfide Shuttle 29 1.5 Summary 30 References 30 2 Sulfur Cathodes 33
Holger Althues, Susanne Dörfler, Sören Thieme, Patrick Strubel and Stefan Kaskel 2.1 Cathode Design Criteria 33 2.1.1 Overview of Cathode Components and Composition 33 2.1.2 Cathode Design: Role of Electrolyte in Sulfur Cathode Chemistry 34 2.1.3 Cathode Design: Impact on Energy Density on Cell Level 35 2.1.4 Cathode Design: Impact on Cycle Life and Self-discharge 36 2.1.5 Cathode Design: Impact on Rate Capability 37 2.2 Cathode Materials 37 2.2.1 Properties of Sulfur 37 2.2.2 Porous and Nanostructured Carbons as Conductive Cathode Scaffolds 39 2.2.2.1 Graphite-Like Carbons 39 2.2.2.2 Synthesis of Graphite-like Carbons 39 2.2.2.3 Carbon Black 40 2.2.2.4 Activated Carbons 41 2.2.2.5 Carbide-Derived Carbon 42 2.2.2.6 Hard-Template-Assisted Carbon Synthesis 42 2.2.2.7 Carbon Surface Chemistry 43 2.2.3 Carbon/Sulfur Composite Cathodes 43 2.2.3.1 Microporous Carbons 44 2.2.3.2 Mesoporous Carbons 45 2.2.3.3 Macroporous Carbons and Nanotube–based Cathode Systems 46 2.2.3.4 Hierarchical Mesoporous Carbons 47 2.2.3.5 Hierarchical Microporous Carbons 49 2.2.3.6 Hollow Carbon Spheres 50 2.2.3.7 Graphene 51 2.2.4 Retention of LiPS by Surface Modifications and Coating 51 2.2.4.1 Metal Oxides as Adsorbents for Lithium Polysulfides 56 2.3 Cathode Processing 57 2.3.1 Methods for C/S Composite Preparation 57 2.3.2 Wet (Organic, Aqueous) and Dry Coating for Cathode Production 58 2.3.3 Alternative Cathode Support Concepts (Carbon Current Collectors, Binder-free Electrodes) 59 2.3.4 Processing Perspective for Carbons, Binders, and Additives 59 2.4 Conclusions 59 References 61 3 Electrolyte for Lithium–Sulfur Batteries 71
Marzieh Barghamadi, Mustafa Musameh, Thomas Rüther, Anand I. Bhatt, Anthony F. Hollenkamp and Adam S. Best 3.1 The Case for Better Batteries 71 3.2 Li–S Battery: Origins and Principles 72 3.3 Solubility of Species and Electrochemistry 74 3.4 Liquid Electrolyte Solutions 75 3.5 Modified Liquid Electrolyte Solutions 91 3.5.1 Variation in Electrolyte Salt Concentration 91 3.5.2 Mixed Organic–Ionic Liquid Electrolyte Solutions 91 3.5.3 Ionic Liquid Electrolyte Solutions 93 3.6 Solid and Solidified Electrolyte Configurations 96 3.6.1 Polymer Electrolytes 96 3.6.1.1 Absorbed Liquid/Gelled Electrolyte 96 3.6.1.2 Solid Polymer Electrolytes 98 3.6.2 Non-polymer Solid Electrolytes 100 3.7 Challenges of the Cathode and Solvent for Device Engineering 102 3.7.1 The Cathode Loading Challenge 102 3.7.2 Cathode Wetting Challenge 104 3.8 Concluding Remarks and Outlook 108 References 111 4 Anode–Electrolyte Interface 121
Mark Wild 4.1 Introduction 121 4.2 SEI Formation 121 4.3 Anode Morphology 122 4.4 Polysulfide Shuttle 123 4.5 Electrolyte Additives for Stable SEI Formation 123 4.6 Barrier Layers on the Anode 125 4.7 A Systemic Approach 126 References 126 Part II Mechanisms 129 Reference 131 5 Molecular Level Understanding of the Interactions Between Reaction Intermediates of Li–S Energy Storage Systems and Ether Solvents 133
Rajeev S. Assary and Larry A. Curtiss 5.1 Introduction 133 5.2 Computational Details 135 5.3 Results and Discussions 135 5.3.1 Reactivity of Li–S Intermediates with Dimethoxy Ethane (DME) 136 5.3.2 Kinetic Stability of Ethers in the Presence of Lithium Polysulfide 138 5.3.3 Linear Fluorinated Ethers 140 5.4 Summary and Conclusions 144 Acknowledgments 144 References 144 6 Lithium Sulfide 147
Sylwia Walu´s 6.1 Introduction 147 6.2 Li2S as the End Discharge Product 148 6.2.1 General 148 6.2.2 Discharge Product: Li2S or Li2S2/Li2S? 151 6.2.3 A Survey of Experimental andTheoretical Findings Involving Li2S and Li2S2 Formation and Proposed Reduction Pathways 153 6.2.4 Mechanistic Insight into Li2S/Li2S2 Nucleation and Growth 157 6.2.5 Strategies to Limit Li2S Precipitation and Enhance the Capacity 160 6.2.6 Charge Mechanism and its Difficulties 161 6.3 Li2S-Based Cathodes: Toward a Li Ion System 164 6.3.1 General 164 6.3.2 Initial Activation of Li2S – Mechanism of First Charge 165 6.3.3 Recent Developments in Li2S Cathodes for Improved Performances 171 6.4 Summary 176 References 176 7 Degradation in Lithium–Sulfur Batteries 185
Rajlakshmi Purkayastha 7.1 Introduction 185 7.2 Degradation Processes Within a Lithium–Sulfur Cell 190 7.2.1 Degradation at Cathode 190 7.2.2 Degradation at Anode 194 7.2.3 Degradation in Electrolyte 197 7.2.4 Degradation Due to Operating Conditions: Temperature, C-Rates, and Pressure 200 7.2.5 Degradation Due to Geometry: Scale-Up and Topology 205 7.3 Capacity Fade Models 209 7.3.1 Dendrite Models 211 7.3.2 Equivalent Circuit Network Models 213 7.4 Methods of Detecting and Measuring Degradation 214 7.4.1 Incremental Capacity Analysis 215 7.4.2 Differential Thermal Voltammetry 215 7.4.3 Electrochemical Impedance Spectroscopy 215 7.4.4 Resistance Curves 216 7.4.5 Macroscopic Indicators 217 7.5 Methods for Countering Degradation 218 7.6 Future Direction 221 References 222 Part III Modeling 227 8 Lithium–Sulfur Model Development 229
Teng Zhang, Monica Marinescu and Gregory J. Offer 8.1 Introduction 229 8.2 Zero-Dimensional Model 231 8.2.1 Model Formulation 231 8.2.1.1 Electrochemical Reactions 231 8.2.1.2 Shuttle and Precipitation 232 8.2.1.3 Time Evolution of Species 233 8.2.1.4 Model Implementation 233 8.2.2 Basic Charge/Discharge Behaviors 233 8.3 Modeling Voltage Loss in Li–S Cells 236 8.3.1 Electrolyte Resistance 237 8.3.2 Anode Potential 238 8.3.3 Surface Passivation 239 8.3.4 Transport Limitation 240 8.4 Higher Dimensional Models 242 8.4.1 One-Dimensional Models 242 8.4.2 Multi-Scale Models 244 8.5 Summary 245 References 246 9 Battery Management Systems – State Estimation for Lithium–Sulfur Batteries 249
Daniel J. Auger, Abbas Fotouhi, Karsten Propp and Stefano Longo 9.1 Motivation 249 9.1.1 Capacity 249 9.1.2 State of Charge (SoC) 251 9.1.3 State of Health (SoH) 251 9.1.4 Limitations of Existing Battery State Estimation Techniques 252 9.1.4.1 SoC Estimation from "Coulomb Counting" 252 9.1.4.2 SoC Estimation from Open-Circuit Voltage (OCV) 253 9.1.5 Direction of Current Work 253 9.2 Experimental Environment for Li–S Algorithm Development 254 9.2.1 Pulse Discharge Tests 255 9.2.2 Driving Cycle Tests 255 9.3 State Estimation Techniques from Control Theory 256 9.3.1 Electrochemical Models 257 9.3.2 Equivalent Circuit Network (ECN) Models 258 9.3.3 Kalman Filters and Their Derivatives 259 9.4 State Estimation Techniques from Computer Science 261 9.4.1 ANFIS as a Modeling Tool 261 9.4.2 Human Knowledge and Fuzzy Inference Systems (FIS) 263 9.4.3 Adaptive Neuro-Fuzzy Inference Systems 266 9.4.4 State-of-Charge Estimation Using ANFIS 268 9.5 Conclusions and Further Directions 269 Acknowledgments 270 References 270 Part IV Application 273 10 Commercial Markets for Li–S 275
Mark Crittenden 10.1 Technology Strengths Meet Market Needs 275 10.1.1 Weight 275 10.1.2 Safety 276 10.1.3 Cost 276 10.1.4 Temperature Tolerance 276 10.1.5 Shipment and Storage 277 10.1.6 Power Characteristics 277 10.1.7 Environmentally Friendly Technology (Clean Tech) 278 10.1.8 Pressure Tolerance 278 10.1.9 Control 278 10.2 Electric Aircraft 278 10.3 Satellites 280 10.4 Cars 280 10.5 Buses 282 10.6 Trucks 283 10.7 Electric Scooter and Electric Bikes 284 10.8 Marine 285 10.9 Energy Storage 285 10.10 Low-Temperature Applications 286 10.11 Defense 286 10.12 Looking Ahead 286 10.13 Conclusion 287 11 Battery Engineering 289
Gregory J. Offer 11.1 Mechanical Considerations 289 11.2 Thermal and Electrical Considerations 289 References 292 12 Case Study 293
Paul Brooks 12.1 Introduction 293 12.2 A Potted History of Eternal Solar Flight 293 12.3 Why Has It Been So Difficult? 295 12.4 Objectives of HALE UAV 297 12.4.1 Stay Above the Cloud 298 12.4.2 Stay Above the Wind 298 12.4.3 Stay in the Sun 299 12.4.4 Year-Round Markets 300 12.4.5 Seasonal Markets 303 12.4.6 How Valuable Are These Markets and What Does That Mean for the Battery? 303 12.5 Worked Example – HALE UAV 303 12.6 Cells, Batteries, and Real Life 305 12.6.1 Cycle Life, Charge, and Discharge Rates 305 12.6.2 Payload 306 12.6.3 Avionics 306 12.6.4 Temperature 306 12.6.5 End-of-Life Performance 306 12.6.6 Protection 306 12.6.7 Balancing – Useful Capacity 307 12.6.8 Summary of Real-World Issues 307 12.7 A Quick Aside on Regenerative Fuel Cells 308 12.8 So What Do We Need from Our Battery Suppliers? 309 12.9 The Challenges for Battery Developers 310 12.10 The Answer to the Title 310 12.11 Summary 310 Acknowledgments 311 References 311 Index 313

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