Direct Numerical Simulation Modeling of Multidisciplinary Transport during Li-Ion Battery Charge/Discharge Processes

We develop a direct numerical simulation (DNS) model of multidisciplinary transport coupled with electrochemical reactions during Li-ion battery charge/discharge processes based on the finite volume (FV) numerical technique. Different from macroscopic models, the DNS model is based on microstructure of composite electrodes and solves component-wise transport equations. During DNS, the input physical properties are intrinsic material properties, not effective physical properties for macroscopic models. Since the interface of solid and electrolyte phase is evidently differentiated in DNS, the occurrence of electrochemical reactions is prescribed exactly on the interface of solid and electrolyte phase. Therefore, the DNS model has the potential to unravel the underlying mesoscopic pore-scale mechanisms of multi-disciplinary transport coupled with electrochemical reactions and thus can provide insightful information of the involved processes, as well as enables the design and optimization of electrodes, including microstructures inside electrodes. One test case, in which the electrode microstructure is reconstructed with a purely random reconstruction method, is considered. Simulation results corroborate the validity of the DNS model

Direct Numerical Simulation Modeling of Multidisciplinary Transport during Li-Ion Battery Charge/Discharge Processes

We develop a direct numerical simulation (DNS) model of multidisciplinary transport coupled with electrochemical reactions during Li-ion battery charge/discharge processes based on the finite volume (FV) numerical technique. Different from macroscopic models, the DNS model is based on microstructure of composite electrodes and solves component-wise transport equations. During DNS, the input physical properties are intrinsic material properties, not effective physical properties for macroscopic models. Since the interface of solid and electrolyte phase is evidently differentiated in DNS, the occurrence of electrochemical reactions is prescribed exactly on the interface of solid and electrolyte phase. Therefore, the DNS model has the potential to unravel the underlying mesoscopic pore-scale mechanisms of multi-disciplinary transport coupled with electrochemical reactions and thus can provide insightful information of the involved processes, as well as enables the design and optimization of electrodes, including microstructures inside electrodes. One test case, in which the electrode microstructure is reconstructed with a purely random reconstruction method, is considered. Simulation results corroborate the validity of the DNS model

Numerical reconstruction of microstructure of graphite anode of lithium-ion battery

Due to the presence of graphite flake cascades, the real graphite anode of Li-ion battery shows non-isotropic characteristic. The present work developed an ellipsoid-based simulated annealing method and numerically reconstructed the three-dimensional microstructure of a graphite anode. The reconstructed anode is a composite of three clearly distinguished phases: pore (or electrolyte), graphite, and solid additives, well representing the non-isotropic heterogeneous characteristic of real graphite anode. Characterization analysis of the reconstructed electrode gives information such as the connectivity of individual phase, the specific interfacial area between solid and pore phase, and the pore size distribution. The effects of the ellipsoid size on the structural characteristics of graphite anode were particularly studied. As the size of the ellipsoidal particle slightly increases, the average pore diameter increases and as a result the specific interfacial area between the solid and pore phase in the reconstructed area decreases; compared with the equatorial radius, the polar radius of ellipsoidal graphite particles has more significant influence on the characteristics of electrode microstructure

Numerical reconstruction of microstructure of graphite anode of lithium-ion battery

Due to the presence of graphite flake cascades, the real graphite anode of Li-ion battery shows non-isotropic characteristic. The present work developed an ellipsoid-based simulated annealing method and numerically reconstructed the three-dimensional microstructure of a graphite anode. The reconstructed anode is a composite of three clearly distinguished phases: pore (or electrolyte), graphite, and solid additives, well representing the non-isotropic heterogeneous characteristic of real graphite anode. Characterization analysis of the reconstructed electrode gives information such as the connectivity of individual phase, the specific interfacial area between solid and pore phase, and the pore size distribution. The effects of the ellipsoid size on the structural characteristics of graphite anode were particularly studied. As the size of the ellipsoidal particle slightly increases, the average pore diameter increases and as a result the specific interfacial area between the solid and pore phase in the reconstructed area decreases; compared with the equatorial radius, the polar radius of ellipsoidal graphite particles has more significant influence on the characteristics of electrode microstructure

Associations between time-weighted personal air pollution exposure and amino acid metabolism in healthy adults

The molecular mechanisms underlying the associations between air pollution exposure and adverse cardiopulmonary effects remain to be better understood. Altered amino acid metabolism may plays an important role in the development of cardiopulmonary diseases and may be perturbed by air pollution exposure. To test this hypothesized molecular mechanism, we conducted an association analysis from an existing intervention study to examine the relations of air pollution exposures with amino acids in 43 Chinese healthy adults. Plasma levels of amino acids were measured using a UPLC-QqQ-MS system. Time-weighted personal exposure to O3, PM2.5, NO2, and SO2 over four time windows, i.e., 12 h, 24 h, 1 week, and 2 weeks, were calculated using the measured indoor and outdoor concentrations coupled with the time-activity data for each participant. Linear mixed-effects models were used to estimate the associations between air pollutants at each exposure window and amino acids by controlling for potential confounders. We observed significant associations between exposures and plasma concentrations of amino acids, with the direction of associations varying by amino acid and air pollutant. While there is little evidence of associations for NO2 and SO2, the associations with amino acids were fairly pronounced for exposure to PM2.5 and O3. In particular, independent O3 (12- and 24-hour) associations were observed with changes in the amino acids that were related to the urea cycle, including aspartate, asparagine, glutamate, arginine, citrulline, and ornithine. Our findings indicated that air pollution may cause acute perturbation of amino acid metabolism, and that O3 and PM2.5 may affect the metabolism of amino acids in different pathways.Main finding: Acute air pollution exposure might affect the perturbation of amino acid metabolism, and in particular, was associated with amino acids in relation to the urea cycle

In Situ Self-Assembled FeWO₄/Graphene Mesoporous Composites for Li-Ion and Na-Ion Batteries

With the growing demands for large-scale applications, rechargeable batteries with cost-effective and environmental-friendly characteristics have gained much attention in recent years. However, some practical challenges still exist in getting ideal electrode materials. In this work, three-dimensional FeWO₄/graphene mesoporous composites with incredibly tiny nanospheres of 5–15 nm in diameter have been synthesized by an in situ self-assembled hydrothermal route. First-principles density functional theory has been used to theoretically investigate the crystal structure change and the insertion/extraction mechanism of Li and Na ions. Unlike most graphene-coated materials, which suffer the restacking of graphene layers and experience significant irreversible capacity losses during charge and discharge process, the as-prepared composites have alleviated this issue by incorporating tiny solid nanospheres into the graphene layers to reduce the restacking degree. High capacity and excellent cyclic stability have been achieved for both Li-ion and Na-ion batteries. At the current density of 100 mA g^–1, the discharge capacity for Li-ion batteries remains as high as 597 mAh g^–1 after 100 cycles. The Na-ion batteries also exhibit good electrochemical performance with a capacity of 377 mAh g^–1 at 20 mA g^–1 over 50 cycles. The synthetic procedure is simple, cost-effective and scalable for mass production, representing a step further toward the realization of sustainable batteries for efficient stationary energy storage