23 research outputs found
Battery data integrity and usability: Navigating datasets and equipment limitations for efficient and accurate research into battery aging
A tremendous commitment of resources is needed to acquire, understand and apply battery data in terms of performance and aging behavior. There are many state of performance (SOP) and state of health (SOH) metrics that are useful to guide alignment of batteries to end-use, yet how these metrics are measured or extracted can make the difference between usable, valuable datasets versus data that lacks the necessary integrity to meet baseline confidence levels for SOP/SOH quantification. This work will speak to 1) types of data that support SOP and SOH evaluations on mechanistic terms, 2) measurement conditions needed to assure high data integrity, 3) equipment limitations that can compromise data high fidelity, and 4) the impact of cell polarization on data quality. A common goal in battery research and field use is to work from a data platform that supports economical paths of data capture while minimizing down-time for battery diagnostics. An ideal situation would be to utilize data obtained during normal daily use (“pulses or cycles of convenience”) without stopping the daily duty cycles to perform dedicated SOP/SOH diagnostic routines. However, difficulties arise in trying to make use of daily duty cycle data (denoted as cycle-by-cycle, CBC) that underscores the need for standardization of conditions: temperature and duty cycles can vary over the course of a day and throughout a week, month and year; polarization can develop within an immediate cycle and throughout successive cycles as a hysteresis. If CBC data is envisioned as a data source to determine performance and aging trends, it should be recognized that polarization is a frequent consequence of CBC and thus makes it difficult to separate reversible and irreversible components to metrics such as capacity loss and resistance increase over aging. Since CBC conditions can have a major impact on data usability, we will devote part of this paper to CBC data conditioning and management. Differential analyses will also be discussed as a means to detect changing trends in data quality. Our target cell chemistries will be lithium-ion types NMC/graphite and LMO/LTO
Glassy Li Metal Anode for High-Performance Rechargeable Li Batteries
Controlling nanostructure from molecular, crystal lattice to the electrode
level remains as arts in practice, where nucleation and growth of the crystals
still require more fundamental understanding and precise control to shape the
microstructure of metal deposits and their properties. This is vital to achieve
dendrite-free Li metal anodes with high electrochemical reversibility for
practical high-energy rechargeable Li batteries. Here, cryogenic-transmission
electron microscopy was used to capture the dynamic growth and atomic structure
of Li metal deposits at the early nucleation stage, in which a phase transition
from amorphous, disordered states to a crystalline, ordered one was revealed as
a function of current density and deposition time. The real-time atomic
interaction over wide spatial and temporal scales was depicted by the
reactive-molecular dynamics simulations. The results show that the condensation
accompanied with the amorphous-to-crystalline phase transition requires
sufficient exergy, mobility and time to carry out, contrary to what the
classical nucleation theory predicts. These variabilities give rise to
different kinetic pathways and temporal evolutions, resulting in various
degrees of order and disorder nanostructure in nano-sized domains that dominate
in the morphological evolution and reversibility of Li metal electrode.
Compared to crystalline Li, amorphous/glassy Li outperforms in cycle life in
high-energy rechargeable batteries and is the desired structure to achieve high
kinetic stability for long cycle life.Comment: 29 pages, 8 figure
Localized High-Concentration Electrolytes Get More Localized Through Micelle-Like Structures
Liquid electrolytes in batteries are typically treated as macroscopically
homogeneous ionic transport media despite having complex chemical composition
and atomistic solvation structures, leaving a knowledge gap of microstructural
characteristics. Here, we reveal a unique micelle-like structure in a localized
high-concentration electrolyte (LHCE), in which the solvent acts as a
surfactant between an insoluble salt in diluent. The miscibility of the solvent
with the diluent and simultaneous solubility of the salt results in a
micelle-like structure with a smeared interface and an increased salt
concentration at the centre of the salt-solvent clusters that extends the salt
solubility. These intermingling miscibility effects have temperature
dependencies, wherein an exemplified LHCE peaks in localized cluster salt
concentration near room temperature and is utilized to form a stable
solid-electrolyte interphase (SEI) on Li-metal anode. These findings serve as a
guide to predicting a stable ternary phase diagram and connecting the
electrolyte microstructure with electrolyte formulation and formation protocols
to form stable SEI for enhanced battery cyclability
Nature of Oxygen Adsorption on Defective Carbonaceous Materials
Plane-wave density functional theory has been used to study oxygen adsorption on graphene, graphite, and (12,0) zigzag single-walled carbon nanotubes with and without Stone–Wales (SW) and single-vacancy (SV) defects to understand the role of defects on carbonaceous material reactivity. Atomic oxygen adsorption leads to the formation of an epoxide on defect-free graphene and graphite and an ether on the exterior wall of carbon nanotubes and SW-defected materials. O2 chemisorption is endothermic on defect-free graphene and graphite and slightly exothermic on defect-free nanotubes. O2 chemisorption energies are predicted to be −1.1 to −1.4 eV on an SW defect and −6.0 to −8.0 eV on an SV defect. An SW defect lowers the energy barriers by 0.90 and 0.50 eV for O2 chemisorption on graphene and nanotubes, respectively. The formation of a C–O–O–C group is important for O2 dissociation on defect-free and SW-defected materials. The energy barrier is less than 0.30 eV on an SV defect. The more reactive SW defect toward O adsorption on graphene is mostly due to the strained defective carbon atoms being able to donate more electrons to an O to form an ether. The larger 2s character in the hybrid orbitals in an ether than in an epoxide makes the ether C–O bond stronger. Stronger C–O binding on an SW-defective carbon nanotube than on a defect-free nanotube is in part due to more flexibility of the defect to release the epoxide ring strain to form an ether
Physical properties of pyroclastic density currents: relevance, challenges and future directions
International audiencePyroclastic density currents (PDCs) are hazardous and destructive phenomena that pose a significant threat to communities living in the proximity of active volcanoes. PDCs are ground-hugging density currents comprised of high temperature mixtures of pyroclasts, lithics, and gas that can propagate kilometres away from their source. The physical properties of the solid particles, such as their grain size distribution, morphology, density, and componentry play a crucial role in determining the dynamics and impact of these flows. The modification of these properties during transport also records the causative physical processes such as deposition and particle fragmentation. Understanding these processes from the study of deposits from PDCs and related co-PDC plumes is essential for developing effective hazard assessment and risk management strategies. In this article, we describe the importance and relevance of the physical properties of PDC deposits and provide a perspective on the challenges associated with their measurement and characterization. We also discuss emerging topics and future research directions such as electrical charging, granular rheology, ultra-fine ash and thermal and surface properties that are underpinned by the characterization of pyroclasts and their interactions at the micro-scale. We highlight the need to systematically integrate experiments, field observations, and laboratory measurements into numerical modelling approaches for improving our understanding of PDCs. Additionally, we outline a need for the development of standardised protocols and methodologies for the measurement and reporting of physical properties of PDC deposits. This will ensure comparability, reproducibility of results from field studies and also ensure the data are sufficient to benchmark future numerical models of PDCs. This will support more accurate simulations that guide hazard and risk assessments
Physical properties of pyroclastic density currents : relevance, challenges and future directions
Pyroclastic density currents (PDCs) are hazardous and destructive phenomena that pose a significant threat to communities living in the proximity of active volcanoes. PDCs are ground-hugging density currents comprised of high temperature mixtures of pyroclasts, lithics, and gas that can propagate kilometres away from their source. The physical properties of the solid particles, such as their grain size distribution, morphology, density, and componentry play a crucial role in determining the dynamics and impact of these flows. The modification of these properties during transport also records the causative physical processes such as deposition and particle fragmentation. Understanding these processes from the study of deposits from PDCs and related co-PDC plumes is essential for developing effective hazard assessment and risk management strategies. In this article, we describe the importance and relevance of the physical properties of PDC deposits and provide a perspective on the challenges associated with their measurement and characterization. We also discuss emerging topics and future research directions such as electrical charging, granular rheology, ultra-fine ash and thermal and surface properties that are underpinned by the characterization of pyroclasts and their interactions at the micro-scale. We highlight the need to systematically integrate experiments, field observations, and laboratory measurements into numerical modelling approaches for improving our understanding of PDCs. Additionally, we outline a need for the development of standardised protocols and methodologies for the measurement and reporting of physical properties of PDC deposits. This will ensure comparability, reproducibility of results from field studies and also ensure the data are sufficient to benchmark future numerical models of PDCs. This will support more accurate simulations that guide hazard and risk assessments
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