Transition Metal Oxides as Cathodes in Li-O2 battery: A First Principles Investigation

Li-O2 batteries have traditionally used carbon based electrodes (graphite, buckypaper) as the cathode of choice due to its good electrical conductivity, stability against non-aqueous electrolytes like Dimethyl ether (DME) and ease of handling. But, the carbon cathode also leads to formation of carbonate by-products that increase overpotentials during charging leading to degradation of cathode and reduction of cyclability. In this work, we investigate some of the well-known oxides as cathodes with focus on the interface between the oxide surfaces and the discharge product: Li2O2, in the Li-O2 battery using first principles computations. Our results show that attention must be paid on choosing the appropriate surface of the oxides. We extend the analysis to suggest other possible oxide chemistries that should be investigated as cathodes in Li-O2 batteries

Study of Defects in Aluminium using Large Scale Electronic Structure Calculations.

Defects in materials play an important role in determining their behavior. Defects, such as vacancies, dislocations, surfaces, dopants, interstitials, though present in small concentrations of the order of few parts per million (ppm), can influence properties of the materials at macroscopic scales. Various computational techniques have been used to model the influence of defects on the properties of materials. Density functional theory based electronic structure calculations have been very accurate in predicting material properties. Electronic structure calculations have provided various insights into the properties of materials such as bulk properties, surface energetics and phase transformations. But, their applicability in studying defect properties is restricted due to limitations on simulation cell-size, to the order of a few hundred to thousand atoms. Recently developed coarse graining technique Quasi Continuum orbital free density functional theory (QCOFDFT) addresses these issues using a real-space local variational formulation of the orbital free density functional theory, finite element discretization of the formulation and an adaptive coarse graining technique. Using this technique, multi-million atom simulations with arbitrary boundary conditions are accessible, which are instrumental in modeling defects in crystalline materials. In this thesis, we extend the QCOFDFT technique to the more accurate non-local kinetic energy functionals that describe materials systems whose electronic structure is close to that of a free electron gas. First, we present a local variational reformulation of the non-local functionals. The accuracy of this local formulation is validated with calculations on bulk properties of Aluminium and compared against plane-wave basis implementations. The coarse graining technique, QCOFDFT, is then used with this local reformulation to achieve multi-million atom simulations of vacancies in Aluminium. Cell-size studies are performed on mono and di-vacancies to underscore the need of large scale electronic structure calculations for an accurate understanding of the eneregtics of defects. The real-space formulation is then used to study an isolated edge dislocation to characterize the defect core and investigate the influence of external deformations on defect-core energetics. Finally, we use QCOFDFT to study vacancy clustering and nucleation of dislocation loops which have important consequences in embrittlement of metals due to radiation damage and quenching processes.PHDMechanical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/107189/1/grbala_1.pd

Transparent Conducting Oxides as Cathodes in Li-O2 Batteries: A First Principles Computational Investigation

Li-O2 batteries have traditionally used carbon based electrodes (graphite, buckypaper) as the cathode of choice due toits good electrical conductivity, stability against non-aqueous electrolytes like dimethoxyethane (DME) and ease ofhandling. But, the carbon cathode also leads to formation of carbonate by-products that increase overpotentials duringcharging leading to degradation of the cathode and reduction of cyclability. Recent investigations have focused on using metal-oxides like SnO2, TiO2 as viable cathodes-alternatives in Li-O2 systems. In this paper, we investigate transparent conducting oxides (TCOs) as cathodes with focus on the interface between the TCO surfaces and the discharge product, Li2O2, in the Li-O2 battery using first principles computations

Ecology of mudbanks - Phytoplankton productivity in Alleppey mudbank

The standing crop of phytcplankton, in terms of biomass, chloropliyll a and total ceils, recorded high values during the rise as well as maturity of the mudbank. However, the primary production showed high values only before, and not during or after, the formation of the mudbank Qualitatively, a total of 58 species of phytoplankters were present. A no'abie feature seen in association with the mud bank was the blooming of Noctiluca miliaris, at the time of dissipation of the mudbank during both the seasons'of 1971 and 1972. The possible relation ship of phytoplankton to and the role it plays at the mudbank is briefly discussed

Controllability of nonlinear differential evolution systems in a separable Banach space

In this article, we study the controllability of semilinear evolution differential systems with nonlocal initial conditions in a separable Banach space. The results are obtained by using Hausdorff measure of noncompactness and a new calculation method

Quality Implications of Warranties in a Supply Chain

We examine a supply chain in which the final product consists of components made by a buyer and a supplier. In the single moral-hazard case, the buyer's quality is observable, whereas in the double moral-hazard case, the buyer's quality is not observable. The supplier's quality is not observable in both the single and double moral-hazard cases. In each case, we examine a warranty/penalty contract between the buyer and the supplier based on information from incoming inspection and external failures. When the warranty contract is based on information from external failures in the single moral-hazard case, the first-best quality is achieved, whereas in the double moral-hazard case, the first-best quality is achieved if the supplier is not held responsible for the buyer's defects. When the warranty contract is based on information from incoming inspection, the first-best is achieved in both the single and double moral-hazard cases, even when the incoming inspection does not identify all of the supplier's defectives. An analysis of whether the penalty on the supplier in each case meets a fairness criterion---that is, the penalty does not exceed the manufacturer's external failure cost---indicates that the fairness criterion is met by the warranty contract based on information from incoming inspection when the first-best incoming inspection is sufficiently high. However, if the first-best incoming inspection is low and the precision of pinpointing the supplier's responsibility for external failure is sufficiently high, the warranty contract based on external failures could satisfy the fairness criterion.incentives, supply chain, moral hazard, warranty, fairness criterion, legal constraint, quality management