Efficient electrochemical model for lithium-ion cells

Lithium-ion batteries are used to store energy in electric vehicles. Physical models based on electro-chemistry accurately predict the cell dynamics, in particular the state of charge. However, these models are nonlinear partial differential equations coupled to algebraic equations, and they are computationally intensive. Furthermore, a variable solid-state diffusivity model is recommended for cells with a lithium ion phosphate positive electrode to provide more accuracy. This variable structure adds more complexities to the model. However, a low-order model is required to represent the lithium-ion cells' dynamics for real-time applications. In this paper, a simplification of the electrochemical equations with variable solid-state diffusivity that preserves the key cells' dynamics is derived. The simplified model is transformed into a numerically efficient fully dynamical form. It is proved that the simplified model is well-posed and can be approximated by a low-order finite-dimensional model. Simulations are very quick and show good agreement with experimental data

Tin-graphene tubes as anodes for lithium-ion batteries with high volumetric and gravimetric energy densities.

Limited by the size of microelectronics, as well as the space of electrical vehicles, there are tremendous demands for lithium-ion batteries with high volumetric energy densities. Current lithium-ion batteries, however, adopt graphite-based anodes with low tap density and gravimetric capacity, resulting in poor volumetric performance metric. Here, by encapsulating nanoparticles of metallic tin in mechanically robust graphene tubes, we show tin anodes with high volumetric and gravimetric capacities, high rate performance, and long cycling life. Pairing with a commercial cathode material LiNi0.6Mn0.2Co0.2O2, full cells exhibit a gravimetric and volumetric energy density of 590 W h Kg-1 and 1,252 W h L-1, respectively, the latter of which doubles that of the cell based on graphite anodes. This work provides an effective route towards lithium-ion batteries with high energy density for a broad range of applications

Radiation damage and defect behavior in ion-implanted, lithium counterdoped silicon solar cells

Boron doped silicon n+p solar cells were counterdoped with lithium by ion implanation and the resultant n+p cells irradiated by 1 MeV electrons. The function of fluence and a Deep Level Transient Spectroscopy (DLTS) was studied to correlate defect behavior with cell performance. It was found that the lithium counterdoped cells exhibited significantly increased radiation resistance when compared to boron doped control cells. It is concluded that the annealing behavior is controlled by dissociation and recombination of defects. The DLTS studies show that counterdoping with lithium eliminates at least three deep level defects and results in three new defects. It is speculated that the increased radiation resistance of the counterdoped cells is due primarily to the interaction of lithium with oxygen, single vacancies and divacancies and that the lithium-oxygen interaction is the most effective in contributing to the increased radiation resistance

Effective fire extinguishing systems for lithium-ion battery

Lithium-ion batteries are a popular choice of power source for a variety of energy and power demanding applications for both stationary applications and electromobility. Among electrochemical storage systems, Lithium-ion batteries were found to be promising candidate, due to their high power and high energy density. In order to assemble high power batteries for plug-in hybrid electric vehicles and pure electric vehicles, several hundreds of large-format Lithium-ion cells will be required, and even more cells for power/energy demanding stationary applications. However, safety remains a significant concern, as battery failure leads to ejection of hazardous materials and rapid heat release. The failure of a single cell can generate a large amount of heat which can then initiate, in the worst case, the thermal runaway of neighbouring cells, leading to failure throughout the battery pack. The heat accumulation can also run into the venting of a cell, with the emission of flammable organic solvent inside the battery pack. Battery failure can be initiated via a number of different abuse scenarios, such as overheating, overcharging, puncture/crushing, water immersion, or external short circuit. Development of effective mitigation strategies necessitates a study on battery failure events and a better understanding of important characteristics relating to safety, such as heat release, hazardous materials ejection, and thermal propagation. On the other hand, when a fire event is initiated, proper intervention strategies have to be defined in order to avoid it becoming catastrophic. In this paper are reported the results of thermal abuse tests on single Lithium-ion cells and a battery pack. The tests were performed with the technical equipment and resources of National Fire Corps. Screening tests for battery fire extinguishing agents were also performed. The effectiveness of an agent was evaluated through experiments on the cooling effect of fire extinguishing agents. Among the various agents, water and foam were found to be the most effective

Stochastic model for the 3D microstructure of pristine and cyclically aged cathodes in Li-ion batteries

It is well-known that the microstructure of electrodes in lithium-ion batteries strongly affects their performance. Vice versa, the microstructure can exhibit strong changes during the usage of the battery due to aging effects. For a better understanding of these effects, mathematical analysis and modeling has turned out to be of great help. In particular, stochastic 3D microstructure models have proven to be a powerful and very flexible tool to generate various kinds of particle-based structures. Recently, such models have been proposed for the microstructure of anodes in lithium-ion energy and power cells. In the present paper, we describe a stochastic modeling approach for the 3D microstructure of cathodes in a lithium-ion energy cell, which differs significantly from the one observed in anodes. The model for the cathode data enhances the ideas of the anode models, which have been developed so far. It is calibrated using 3D tomographic image data from pristine as well as two aged cathodes. A validation based on morphological image characteristics shows that the model is able to realistically describe both, the microstructure of pristine and aged cathodes. Thus, we conclude that the model is suitable to generate virtual, but realistic microstructures of lithium-ion cathodes

Characterization of Iron Phthalocyanine as the Cathode Active Material for Lithium-Ion Batteries

This project presents the characterization of iron phthalocyanine (FePc) as the cathode active material to be used in higher specific lithium storage and energy density lithium-ion cells/batteries. Theoretical work suggested the control of the active material particle size for its optimum utilization during the discharge of lithium-ion cells. Also, the experimental work reported the lithium storage in FePc is equivalent to 2050 mAh/g FePc that was encouraging to characterize FePc as a potential cathode material. In experimental work, two types of cells were tested: 1) high temperature polyethylene oxide electrolyte-based lithium/FePc cells and 2) room temperature organic liquid electrolyte-based lithium/FePc cells. Estimating the theoretical lithium storage capacity of the cathode active material, and the experimental results from the ongoing research/development work on the lithium/iron phthalocyanine cells are included in this project.https://ecommons.udayton.edu/stander_posters/1638/thumbnail.jp

The effects of lithium counterdoping on radiation damage and annealing in n(+)p silicon solar cells

Boron-doped silicon n(+)p solar cells were counterdoped with lithium by ion implantation and the resultant n(+)p cells irradiated by 1 MeV electrons. Performance parameters were determined as a function of fluence and a deep level transient spectroscopy (DLTS) study was conducted. The lithium counterdoped cells exhibited significantly increased radiation resistance when compared to boron doped control cells. Isochronal annealing studies of cell performance indicate that significant annealing occurs at 100 C. Isochronal annealing of the deep level defects showed a correlation between a single defect at E sub v + 0.43 eV and the annealing behavior of short circuit current in the counterdoped cells. The annealing behavior was controlled by dissociation and recombination of this defect. The DLTS studies showed that counterdoping with lithium eliminated three deep level defects and resulted in three new defects. The increased radiation resistance of the counterdoped cells is due to the interaction of lithium with oxygen, single vacancies and divacancies. The lithium-oxygen interaction is the most effective in contributing to the increased radiation resistance

Applying different configurations for the thermal management of a lithium titanate oxide battery pack

This investigation’s primary purpose was to illustrate the cooling mechanism within a lithium titanate oxide lithium-ion battery pack through the experimental measurement of heat generation inside lithium titanate oxide batteries. Dielectric water/glycol (50/50), air and dielectric mineral oil were selected for the lithium titanate oxide battery pack’s cooling purpose. Different flow configurations were considered to study their thermal effects. Within the lithium-ion battery cells in the lithium titanate oxide battery pack, a time-dependent amount of heat generation, which operated as a volumetric heat source, was employed. It was assumed that the lithium-ion batteries within the battery pack had identical initial temperature conditions in all of the simulations. The lithium-ion battery pack was simulated by ANSYS to determine the temperature gradient of the cooling system and lithium-ion batteries. Simulation outcomes demonstrated that the lithium-ion battery pack’s temperature distributions could be remarkably influenced by the flow arrangement and fluid coolant type

Performance of nanocrystalline Ni3N as a negative electrode for sodium-ion batteries

Nickel nitride is synthesised by high temperature ammonolysis of nickel(II) hexamine and tris(ethylenediamine) salts. Its electrochemical characteristics are examined in half-cells vs. lithium and sodium. Samples with high surface area are found to have significant reversible charge storage capacity in sodium cells and hence to be a promising negative electrode material for sodium-ion batteries