This thesis makes significant advances in the design of electrolytes and interfaces in electrochemical cells that utilize reactive metals as anodes. Such cells are of contemporary interest because they offer substantially higher charge storage capacity than state-of-the-art lithium-ion battery technology. Batteries based on metallic anodes are currently considered impractical and unsafe because recharge of the anode causes physical and chemical instabilities that produce dendritic deposition of the metal leading to catastrophic failure via thermal runaway. This thesis utilizes a combination of chemical synthesis, physical & electrochemical analysis, and materials theory to investigate structure, ion transport properties, and electrochemical behaviors of hybrid electrolytes and interfacial phases designed to prevent such instabilities. In particular, it demonstrates that relatively low-modulus electrolytes composed of cross-linked networks of polymer-grafted nanoparticles stabilize electrodeposition of reactive metals by multiple processes, including screening electrode electrolyte interactions at electrochemical interfaces and by regulating ion transport in tortuous nanopores. This discovery is significant because it overturns a longstanding perception in the field of nanoparticle-polymer hybrid electrolytes that only solid electrolytes with mechanical modulus higher than that of the metal electrode are able to stabilize electrodeposition of reactive metals.
This thesis makes significant advances in the design of electrolytes and interfaces in electrochemical cells that utilize reactive metals as anodes. Such cells are of contemporary interest because they offer substantially higher charge storage capacity than state-of-the-art lithium-ion battery technology. Batteries based on metallic anodes are currently considered impractical and unsafe because recharge of the anode causes physical and chemical instabilities that produce dendritic deposition of the metal leading to catastrophic failure via thermal runaway. This thesis utilizes a combination of chemical synthesis, physical & electrochemical analysis, and materials theory to investigate structure, ion transport properties, and electrochemical behaviors of hybrid electrolytes and interfacial phases designed to prevent such instabilities. In particular, it demonstrates that relatively low-modulus electrolytes composed of cross-linked networks of polymer-grafted nanoparticles stabilize electrodeposition of reactive metals by multiple processes, including screening electrode electrolyte interactions at electrochemical interfaces and by regulating ion transport in tortuous nanopores. This discovery is significant because it overturns a longstanding perception in the field of nanoparticle-polymer hybrid electrolytes that only solid electrolytes with mechanical modulus higher than that of the metal electrode are able to stabilize electrodeposition of reactive metals.
In recent years, continuous progress in electronic devices, especially in wearable devices, has attracted surging attention from the consumer market. Therefore, flexible energy storage was developed to fulfill the needs of new flexible devices with ultra-lightweight and small volume. The very recent products and concepts such as touch screens, roll-up displays, wearable sensors, and even implantable medical devices have shown great potential in flexible applications because of their extreme convenience. However, the development of corresponding power sources largely lags behind these emerging technologies of flexible devices. Lithium-ion batteries (LIBs), owing to high energy density and high operating voltage, have been serving as an ideal power source for flexible devices. Nevertheless, direct implementation of commercial LIBs leads to irreversible deformation of structural integrity, short-circuiting or even severe explosion hazard. Such dilemma originates from the poor flexibility of electrode and electrolyte. For electrode side, current electrode sheets used in LIBs are manufactured by holding active material particles and conductive agents by a small weight fraction of polymeric binders. Such fragile electrode structure could easily lose electrical contact under physical deformation, leading to disintegrated electrode sheets, drastic degradations of electrochemical performance, and even safety issue due to internal short-circuiting. For electrolyte side, LIBs employ nonaqueous liquid electrolyte with high ionic conductivity and excellent electrode wettability. However, the drawbacks of such electrolyte system are also evident: poor ion selectivity, flammability, and leakage issue while being deformed render unsuitability of liquid electrolyte for flexible device application. To fabricate flexible LIBs, the current state-of-the-art research employs two design strategies involving electrode structure. One popular strategy is constructing scaffolding structure using carbonaceous materials to function as supportive matrix for active materials. Given carbon nanotubes (CNTs) as an example, the CNTs possess remarkable electrical conductivity and mechanical strength (elastic modulus: 1 TPa, tensile strength: 100 GPa), which contribute to conductive and flexible electrodes as the high-aspect ratio of CNTs can serve as threading materials. Another strategy is rational architecture design of active materials that are conventionally particulate. For example, vanadium pentoxide nanowires can be readily fabricated into free-standing and binder-free electrode membrane. Nevertheless, the most of strategies above still fall short of practicality due to reduced portion of active materials and consequently compromised energy density. In comparison with the mobile liquid electrolyte, the emerging solid-state electrolytes could largely solve circumventing issues of ion selectivity, flammability and leakage. As one prevailing category, solid polymer electrolytes comprising polymers and lithium salts feature decent manufacturing flexibility. Meanwhile, their poor ionic conductivity (10 8 ~ 10 5S cm 1) could be ameliorated by gel polymer electrolytes with organic solvents (plasticizers) and/or inorganic solid fillers (e.g., SiO2). Nevertheless, the non-conductive fillers block ion-transport pathways while allow partial electrical conduction, limiting the interfacial engineering and compatibility with electrodes. In this dissertation, we tackle the aforementioned critical issues of flexible batteries in two aspects. Firstly, we design and synthesize flexible electrode from prospective of material and architecture. A novel cathode constructed by entangling networks of V2O5, CNTs and polytetrafluoroethylene (PTFE) is design and fabricated. Notably, the resulting flexible battery simultaneously achieves excellent mechanical strength (800 MPa young's module), superior cycle durability (86% retention after 1000 times bending) and intriguing capacity (300 mAh g-1 at 0.25C). Furthermore, a Zr-based metal-organic framework (MOF) possessing open-metal sites (OMSs) was used as the microporous filler to facilitate cation (Li+) conduction in GPL. Compared with the state-of-the-art research, our work significantly enhanced tLi+ of GLP from 0.39 up to 0.66 while maintained 1.5 mS cm 1 ionic conductivity. Notably, a reduced thermal activation energy (from 113 to 76 meV) was observed, suggesting diffusion energy barriers was eased by selective promotion of Li+ conduction. To conclude, flexible Li-ion batterie system research is still at early developing stage. Above work provides rational design and improvement of the current FLIBs system in rather facile and cost-effective way. The methodology we proposed are hoped to bring further innovation toward FLIBs field and be extended to numerous applications in the future.
This book discusses the roles of nanostructures and nanomaterials in the development of battery materials for state-of-the-art electrochemical energy storage systems, and provides detailed insights into the fundamentals of why batteries need nanostructures and nanomaterials. It explores the advantages offered by nanostructure electrode materials, the challenges of using nanostructured materials in batteries, as well as the rational design of nanostructures and nanomaterials to achieve optimal battery performance. Further, it closely examines the latest advances in the application of nanostructures and nanomaterials for future rechargeable batteries, including high-energy and high-power lithium ion batteries, lithium metal batteries (Li-O2, Li-S, Li-Se, etc.), all-solid-state batteries, and other metal batteries (Na, Mg, Al, etc.). It is a valuable reference resource for readers interested in or involved in research on energy storage, energy materials, electrochemistry and nanotechnology.
Recent years has seen a tremendous growth in interest for solid state batteries based on polymer electrolytes, with advantages of higher safety, energy density, and ease of processing. The book explains which polymer properties guide the performance of the solid-state device, and how these properties are best determined. It is an excellent guide for students, newcomers and experts in the area of solid polymer electrolytes.
Storage of electrical energy is a cornerstone in the global endeavor to lower greenhouse gas emissions-in particular, electrochemical energy storage in the form of batteries can enable the electrification of transport through electric vehicles, as well as aid the transition to renewable energy generation such as wind and solar through stabilizing the grid and mitigating intermittency. Lithium-ion batteries, a pioneering technology to enable portable electronics, are seeing increased use in transportation and grid-scale applications due to their high energy density, and greatly decreasing production costs over the past decade. However, current lithium-ion batteries are reaching the theoretical energy density and must adhere to higher safety standards as they see use in larger scale formats. The next generation of cheaper, safer, and more energy-dense batteries will be enabled by advances in electrolytes which are the focus of this work. In this thesis, we focus on solid polymer electrolytes, which have the potential to enable more energy-dense batteries, and display improved safety compared to the highly flammable and toxic liquid electrolytes in use today. We detail our work in two main areas: the rational design of highly dissociative ionenes, and the development of a high throughput platform to increase the scale and speed of polymer electrolyte research. In the former, we investigate the impact of anion dissociation energy on ion conduction in solid polymer electrolytes via a novel class of ionenes prepared using acyclic diene metathesis polymerization of highly dissociative, liquid crystalline, fluorinated aryl sulfonimide-tagged ("FAST") anion monomers. These polyanions form well-ordered lamellae that are thermally stable and provide anionic channels for ion hopping. Electrochemical impedance spectroscopy and differential scanning calorimetry experiments, along with nudged elastic band calculations, suggest that cation motion in these materials operates via an ion hopping mechanism, which is enabled by the highly dissociative nature of FAST anions. In parallel, we developed a high throughput platform to accelerate electrolyte research. We detail the engineering problems and solutions which resulted in an estimated 100X increase in sample throughput with vastly less researcher effort. The platform is then leveraged in two case studies, first by performing the largest one-to-one comparison of lithium and sodium ion conduction in poly(ethylene oxide) to date, and secondly, the platform is employed in a machine learning-guided Bayesian optimization system to explore and optimize the ionic conductivity of electrolytes based upon poly(caprolactone). This work sets the stage for continued automation and data-driven design of polymer electrolytes for safer and more energy-dense batteries.
Volume 3 of a 4-volume series is a concise, authoritative and an eminently readable and enjoyable experience related to lithium ion battery design, characterization and usage for portable and stationary power. Although the major focus is on lithium metal oxides or transition metal oxide as alloys, the discussion of fossil fuels is also presented where appropriate. This monograph is written by recognized experts in the field, and is both timely and appropriate as this decade will see application of lithium as an energy carrier, for example in the transportation sector. This Volume focuses on the fundamentals related to batteries using the latest research in the field of battery physics, chemistry, and electrochemistry. The research summarised in this book by leading experts is laid out in an easy-to-understand format to enable the layperson to grasp the essence of the technology, its pitfalls and current challenges in high-power Lithium battery research. After introductory remarks on policy and battery safety, a series of monographs are offered related to fundamentals of lithium batteries, including, theoretical modeling, simulation and experimental techniques used to characterize electrode materials, both at the material composition, and also at the device level. The different properties specific to each component of the batteries are discussed in order to offer tradeoffs between power and energy density, energy cycling, safety and where appropriate end-of-life disposal. Parameters affecting battery performance and cost, longevity using newer metal oxides, different electrolytes are also reviewed in the context of safety concerns and in relation to the solid-electrolyte interface. Separators, membranes, solid-state electrolytes, and electrolyte additives are also reviewed in light of safety, recycling, and high energy endurance issues. The book is intended for a wide audience, such as scientists who are new to the field, practitioners, as well as students in the STEM and STEP fields, as well as students working on batteries. The sections on safety and policy would be of great interest to engineers and technologists who want to obtain a solid grounding in the fundamentals of battery science arising from the interaction of electrochemistry, solid-state materials science, surfaces, and interfaces.
Ceramic and Specialty Electrolytes for Energy Storage Devices, Volume II, investigates recent progress and challenges in a wide range of ceramic solid and quasi-solid electrolytes and specialty electrolytes for energy storage devices. The influence of these electrolyte properties on the performance of different energy storage devices is discussed in detail. Features: • Offers a detailed outlook on the performance requirements and ion transportation mechanism in solid polymer electrolytes • Covers solid-state electrolytes based on oxides (perovskite, anti-perovskite) and sulfide-type ion conductor electrolytes for lithium-ion batteries followed by solid-state electrolytes based on NASICON and garnet-type ionic conductors • Discusses electrolytes employed for high-temperature lithium-ion batteries, low-temperature lithium-ion batteries, and magnesium-ion batteries • Describes sodium-ion batteries, transparent electrolytes for energy storage devices, non-platinum-based cathode electrocatalyst for direct methanol fuel cells, non-platinum-based anode electrocatalyst for direct methanol fuel cells, and ionic liquid-based electrolytes for supercapacitor applications • Suitable for readers with experience in batteries as well as newcomers to the field This book will be invaluable to researchers and engineers working on the development of next-generation energy storage devices, including materials and chemical engineers, as well as those involved in related disciplines.
