Computational Design Of Novel Electrodes For Alkali Ion Batteries

The alkali-ion batteries are the key to unlock the bottleneck of the renewable energy storage and pave the way for a renewable-powered future. Battery technologies for grid-scale energy storage systems requires low costs, safety, high efficiency and high sustainability. In this dissertation, we present not only in-depth understandings of the electrode working mechanism but also develop novel cathode materials for alkali-ion batteries using first principles calculations. We divide the dissertation into four project-based parts. In the first project, we performed a comprehensive study of Prussian blue and its analogues (PBAs) cathodes in aqueous sodium-ion batteries. Using density functional theory calculations, we proposed a general rule of the phase transition that dry PBAs generally undergo a phase transition from a rhombohedral Na2PR(CN)6 (where P and R are transition metals) to a tetragonal/cubic PR(CN)6 during Na extraction, which is in line with experimental observations. Using a grand potential phase diagram construction, we show that existence of lattice water and Na co-intercalation contribute to both higher energy density and better cycling stability. We also identified four new PBA compositions {Na2CoMn(CN)6, Na2NiMn(CN)6, Na2CuMn(CN)6 and Na2ZnMn(CN)6--that show great promise as cathodes for aqueous rechargeable Na-ion batteries. In the second project, we developed design rules for aqueous sodium-ion battery cathodes through a comprehensive density functional theory study of the working potential and aqueous stability of known cathode materials. These design rules were applied in a high-throughput screening of Na-ion battery cathode materials for application in aqueous electrolytes. Five promising cathode materials--NASICON-Na3Fe2(PO4)3, Na2FePO4F, Na3FeCO3PO4, alluadite-Na2Fe3(PO4)3 and Na3MnCO3PO4, were identified as hitherto unexplored aqueous sodium-ion battery cathodes, with high voltage, good capacity, high stability in aqueous environments and facile Na-ion migration. These findings pave the way the practical cathode development for large-scale energy storage systems based on aqueous Na-ion battery chemistry. Then in the third project, we constructed a large database of aqueous Na-ion battery cathodes (Na-ion Aqueous Electrode Database, or NAED) based on the developed design rules in the second project. By screening and analyze the data in the database, we identified two promising candidates, NaMn2O4 and Na2(FeVO4)3 for synthesis and experimentation in aqueous sodium-ion batteries. The final project presents a comprehensive study of Li insertion mechanism in DRX-Li3V2O5 anode in Li-ion batteries. Using a combination of first-principles calculations, cluster expansion and machine learning methods, we show that during discharge, Li ions mainly intercalate into tetrahedral sites, while the majority of Li and V ions in octahedral sites remain stable. Furthermore, its fast-charging nature is attributed to the facile diffusivity of Li ions via a correlated "octahedral-tetrahedral-octahedral" Li diffusion.

The facile conduction of alkali ions in a crystal host is of crucial importance in rechargeable alkali-ion batteries, the dominant form of energy storage today. In this review, we provide a comprehensive survey of computational approaches to study solid-state alkali diffusion. We demonstrate how these methods have provided useful insights into the design of materials that form the main components of a rechargeable alkali-ion battery, namely the electrodes, superionic conductor solid electrolytes and interfaces. We will also provide a perspective on future challenges and directions. Here, the scope of this review includes the monovalent lithium- and sodium-ion chemistries that are currently of the most commercial interest.

Owing to outstanding energy density, Li-ion batteries have dominated the portable electronic industry for the past 20 years and they are now moving forward powering electric vehicles. In light of concerns over limited lithium reserve and rising lithium costs in the future, Na-ion batteries have re-emerged as potential alternatives for large scale energy storage. On the other hand, though both sodium and lithium are alkali metals sharing many chemical similarities, research on Na-ion batteries is still facing many challenges due to the larger size and unique bonding characteristics of Na ions. In this thesis, a series of sodium transition metal oxides are investigated as cathode materials for Na-ion batteries. P2 - Na2/3[Ni1/3Mn2/3]O2 is firstly studied with a combination of first principles calculation and experiment, and battery performance is improved by excluding the phase transformation region. Li substituted compound, P2-Na0.8[Li0.12Ni0.22Mn0.66]O2, is then explored. Its crystal / electronic structure evolution upon cycling is tracked by combing in situ synchrotron X-ray diffraction, ex situ X-ray absorption spectroscopy and solid state NMR. It is revealed that the presence of Li-ions in the transition metal layer allows increased amount of Na-ions to maintain the P2 structure during cycling. The design principles for the P2 type Na cathodes are devised based on this in-depth understanding and an optimized composition is proposed. The idea of Li substitution is then transferred to O3 type cathode. The new material, O3 - Na0.78Li0.18Ni0.25Mn0.583O2, shows discharge capacity of 240 mAh/g, which is the highest capacity and highest energy density so far among cathode materials in Na-ion batteries. With significant progress on cathode materials, a comprehensive understanding of Na2Ti3O7 as anode for Na-ion batteries is discussed. The electrochemical performance is enhanced, due to increased electronic conductivity and reduced SEI formation with carbon coating. Na full cell with high operating voltage is demonstrated by taking advantage of the ultra-low voltage of Na2Ti3O7 anode. The self-relaxation for fully intercalated phase, Na4Ti3O7, is shown for the first time, which results from structural instability as suggested by first principles calculation. Ti4+ / Ti3+ is the active redox couple upon cycling based on XANES characterization. These findings unravel the underlying relation between unique properties and battery performance of Na2Ti3O7 anode, which should ultimately shed light on possible strategies for future improvement.

This book provides state-of-the-art computational approaches for accelerating materials discovery, synthesis, and processing using thermodynamics and kinetics. The authors deliver an overview of current practical computational tools for materials design in the field. They describe ways to integrate thermodynamics and kinetics and how the two can supplement each other.

Computer models are helping to accelerate the design and validation of next generation batteries and provide valuable insights not possible through experimental testing alone. Validated 3-D physics-based models exist for predicting electrochemical performance, thermal and mechanical response of cells and packs under normal and abuse scenarios. The talk describes present efforts to make the models better suited for engineering design, including improving their computation speed, developing faster processes for model parameter identification including under aging, and predicting the performance of a proposed electrode material recipe a priori using microstructure models.

In order to realize the commercialization of alkali-ion batteries (AIB) in electric vehicles and smart grid systems, further improvements are demanded in multiple aspects, especially the energy/power density, safety and cycle life. Due to the complexity of the system, besides each separate component, surface and interface are critical in understanding and optimizing the system. In this dissertation, systematic studies are performed on the nanosizing effect, the surface phase transformation and surface coating of Li-intercalation cathode materials by a combination of first principles and experimental studies. In the first part, the surface spin transition of LiCoO2 (LCO) was found based on first principles calculations. Different sizes of LCO were synthesized and the spin transition on the surface was confirmed by other characterization techniques. The OER/ORR activities profoundly increased at the spin-transited surfaces. The study shed lights on the electronic properties tuning in nanosizing process, which would affect functional properties. In the second part, the structural and chemical evolutions during electrochemical process of the Li-excess compound was probed by a combination of high-end characterization techniques especially STEM/EELS. A second phase generation together with oxygen vacancy formation and microstrain formation was found at the first cycle plateau region. A novel oxygen vacancy assisted transition metal migration mechanism was proposed using first principles calculations. These findings lead to an increased understanding of the performance fading mechanism of Li-excess family compounds, providing new insights in optimization their rate performances. In the third part, the surface coating of LLTO has been investigated for an improved electrochemical performance of the NCA combining computation with other electrochemical tests. The good ionic conductor LLTO increases the system's ion conductivity thus the electrochemical performance. Similar investigations have also been carried out in AlF3 coatings. These studies help the understanding of coating effect of electrode materials. In the fourth part, a detailed STEM/EELS study on the P2 type Na cathode material was carried out.

This book provides a broad and nuanced overview of the achievements and legacy of Professor William (“Bill”) Goddard in the field of computational materials and molecular science. Leading researchers from around the globe discuss Goddard’s work and its lasting impacts, which can be seen in today’s cutting-edge chemistry, materials science, and biology techniques. Each section of the book closes with an outline of the prospects for future developments. In the course of a career spanning more than 50 years, Goddard’s seminal work has led to dramatic advances in a diverse range of science and engineering fields. Presenting scientific essays and reflections by students, postdoctoral associates, collaborators and colleagues, the book describes the contributions of one of the world’s greatest materials and molecular scientists in the context of theory, experimentation, and applications, and examines his legacy in each area, from conceptualization (the first mile) to developments and extensions aimed at applications, and lastly to de novo design (the last mile). Goddard’s passion for science, his insights, and his ability to actively engage with his collaborators in bold initiatives is a model for us all. As he enters his second half-century of scientific research and education, this book inspires future generations of students and researchers to employ and extend these powerful techniques and insights to tackle today’s critical problems in biology, chemistry, and materials. Examples highlighted in the book include new materials for photocatalysts to convert water and CO2 into fuels, novel catalysts for the highly selective and active catalysis of alkanes to valuable organics, simulating the chemistry in film growth to develop two-dimensional functional films, and predicting ligand–protein binding and activation to enable the design of targeted drugs with minimal side effects.

"This is the first machine-generated scientific book in chemistry published by Springer Nature. Serving as an innovative prototype defining the current status of the technology, it also provides an overview about the latest trends of lithium-ion batteries research. This book explores future ways of informing researchers and professionals. State-of-the-art computer algorithms were applied to: select relevant sources from Springer Nature publications, arrange these in a topical order, and provide succinct summaries of these articles. The result is a cross-corpora auto-summarization of current texts, organized by means of a similarity-based clustering routine in coherent chapters and sections. This book summarizes more than 150 research articles published from 2016 to 2018 and provides an informative and concise overview of recent research into anode and cathode materials as well as further aspects such as separators, polymer electrolytes, thermal behavior and modelling. With this prototype, Springer Nature has begun an innovative journey to explore the field of machine-generated content and to find answers to the manifold questions on this fascinating topic. Therefore it was intentionally decided not to manually polish or copy-edit any of the texts so as to highlight the current status and remaining boundaries of machine-generated content. Our goal is to initiate a broad discussion, together with the research community and domain experts, about the future opportunities, challenges and limitations of this technology."--Publisher's website.