Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 35 for “"Delithiation"”.
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Structural evolution of α-Fe2O3 nanowires during lithiation/delithiation and electrochemical property improvement
… material at various stages of lithiation and delithiation. The phase and morphological evolution demonstrate the conversion reaction process in α-Fe2O3. The process was initiated through the reduction of Fe2O3 to Fe3O4 nanocrystals, which form 4-nm-nanoparticles within the nanowire. Further …
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Electrochemical lithiation and delithiation for control of magnetic properties of nanoscale transition metal oxides
Transition metal oxides comprise a fascinating class of materials displaying a variety of magnetic and electronic properties, ranging from half-metallic ferromagnets like CrO2, ferrimagnetic semiconductors like Fey's, and antiferromagnetic insulators like rocksalt-structured FeO. The accessibility …
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Operando investigations of mechanical changes in lithium-ion batteries
… of the active materials during lithiation and delithiation, degradation of the electrodes, decomposition of the electrolyte, and external cell pressure. The work presented here seeks to describe and understand the interplay between electrochemical cycling and mechanical changes within Li-ion …
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Understanding initial capacity loss in substituted layered oxide cathodes for lithium-ion batteries
… 0.08–0.11 Li is “irreversibly” lost after delithiation, resulting in a substantial capacity loss of 10–15%. This loss is conventionally attributed to bulk lithium transport limitations arising from three interrelated factors: (1) contraction of the c-axis lattice during lithiation, (2) …
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Understanding the intrinsic electrochemistry of ni-rich layered cathodes
… NCA is capable of high states of delithiation with minimal structural transitions. Furthermore, commercially available NCA has little to no transition metals in the Li layer. X-ray spectroscopies are an ideal tool for studying cathodes at high states of delithiation due their …
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High-nickel layered oxide cathodes for high-performance lithium-ion batteries
… different Ni contents at identical degrees of delithiation. The overall stabilities of two representative cathodes, LiNi₀.₈Mn₀.₁Co₀.₁O₂ and LiNiO₂, are evaluated with a rigorous control of an identical 70 mol % delithiation. The results suggest that NMC cathodes with higher-Ni contents may have …
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Understanding two-phase reaction processes in electrodes for Li-ion batteries
… the Li-composition phase diagram dictates that delithiation takes place by a kinetically limited nucleation and growth process. It remains controversial as to whether the delithiation process is fundamentally different than expected from thermodynamics. This dissertation is set out to resolve …
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Multinuclear NMR Investigations of Local Structure, Distortions and Redox Mechanisms in Layered Lithium Ion Battery Cathode Materials
… this thesis the local structure, distortions and delithiation behaviours of two intriguing compounds are investigated: LiNi_{0.8}Co_{0.15}Al_{0.05}O_{2} (NCA)—a commercial cathode material with complex redox behaviour—and Li_2RuO_3—a model compound for the highly promising Li excess family of …
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Operando Optical Tracking of Ion Dynamics and Degradation in Battery Electrodes
… LiNixMnyCo<sub>(1−x−y)</sub>O₂ (NMC). Upon delithiation, a rapid increase in lithium diffusivity at the beginning of charge results in particles with lithium-poor peripheries and lithium-rich cores. Finite-element modelling confirms that a SOC-dependent ion diffusivity is necessary to …
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Interfacial processes in Li-ion batteries
… the potential back to 2.0 V vs. Li/Li+ through delithiation of the surface alloy. Lithiation of the Au electrode during Li bulk alloy formation at potentials < 0.2 V vs. Li/Li+ results in compressive stress, as expected. However, in this case residual tensile stress is observed following …
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Three dimensional characterization of failure evolution of tin and silicon in lithium ion battery electrodes
… during the critical early cycles of lithiation/delithiation (i.e., the insertion and extraction of Li+, respectively). Combining in-house algorithms with commercial software, 3D visualizations and measurements were made of particle/wire expansion and cracking. To portray the Li intercalation …
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Thin Film Energy Devices
… on the mechanisms of cyclic lithiation and delithiation of RuO2. RuO2 is a candidate cathode material for next-generation thin film lithium ion batteries (TF-LIBs), due to its relatively large capacity (~5x LiCoO2) and its very good cyclability and rate capability, as well as compatibility …
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Investigating Chemical and Structural Heterogeneities of High-Voltage Spinel Cathode Material for Li-ion Batteries
… lattice distortion evolution upon chemical delithiation, Mn dissolution behaviors, and evaluate the chemical delithiation method as a means to replicate electrochemical cycling conditions. We further investigate lattice distortion spatially via in situ nanodiffraction during battery cycling …
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Stress evolution of thin film RuO₂ Li-ion battery electrodes
… previous experiment, exhibiting near zero stress delithiation and linear increase in stress during lithiation. These results point to a mode of failure of RuO₂ which does not occur in other materials currently being studied.
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Simulations of silicon-graphene anodes using machine-learning-based interatomic potentials
… silicon-carbon systems with a full lithiation-delithiation cycle remains unexplored. This research approaches the aim by developing a Machine Learning Interatomic Potential (MLIP) using the Gaussian Approximation Potential (GAP) framework. The study represents the first comprehensive effort to …
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Electrochemical and microstructural studies of AlPO₄-nanoparticle coated LiCoO₂ for lithium-ion batteries
… LiCoO₂ has a more rapid decrease in Re with delithiation, and both materials show a rise in Re above 4.5V. Structurally, SEM images show pitted surface morphology only on the edges of the layers of coated LiCoO₂.
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Lithium intercalation reactions with transition metal oxides
… The near-cubic symmetry is maintained on delithiation. Neutron and X-ray powder diffraction refinement of the LT-LiCoO₂ sample has shown it to be best described as a layered structure (R3m symmetry) with approximately 6% of the cobalt cations in the predominantly lithium layer and vice …
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Designing new electrode materials for energy devices by integrating ab initio computations with experiments
… and its electrochemical behavior upon delithiation was evaluated. The material shows a high specific charge capacity of about 320 mAh/g and discharge capacity of about 240 mAh/g at the first cycle. The stability of Li2NiO2 in the Immm structure is attributed to the more favorable Li …
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Novel Magnetic Resonance Techniques as Applied to Metallic Phases in Lithium-Ion Battery Electrodes
… from an insulating to a metallic phase on delithiation. Understanding the electronic structures of these systems—and how these structures impact the redox, degradation and failure mechanisms—is critical to the development of the next generation of LIB electrode materials. In this thesis, …
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Diffusional lithium trapping as a failure mechanism of aluminum foil anodes in lithium-ion batteries
… lithium trapping is exacerbated by both higher delithiation rates and higher areal capacity, presenting a challenge towards commercialization of aluminum foil anodes. We further demonstrate that diffusional trapping in aluminum foil anodes can be mitigated through alloy design, with the addition …
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