Sharif Digital Repository

Charge-discharge rate capability is one of the most important properties of cathode materials for lithium batteries, in particular when envisaging high power density applications such as automotive applications. Efforts to modify rate have been carried out by carbon coating and decreasing particle size in order to modify electronic and ionic conductivity. However, this approach cannot justify all experimental data reported in the literature. Here, we investigated the rate capability of cathode materials by considering their density of states (DOS) calculated by several density functional theory (DFT) methods, in both the lithiated and the delithiated case. We suggested that these structures... 

Transition metal lithium orthosilicates are of interest as cathode materials for lithium batteries. Density functional theory (DFT) calculations were performed to evaluate the structural and electrochemical properties of the different polymorphs of Li2MnSiO4. Our computational studies predict superior properties for the Pmn21 polymorph even after extraction of two Li per formula unit. We state that the shortcomings observed for Li2MnSiO4 as a cathode are caused by two mechanisms. Switching of the magnetic state occurs during the first cycles. The subsequent transition, under delithiated conditions, from the Pmn21 or Pmnb polymorphs to the electrochemically weakest P21/n polymorph is the... 

In this paper, similarity solution of free convection from inclined permeable wall embedded in a stratified porous medium is investigated. It is assumed that the heated wall has constant temperature and permeability along the wall is variable. Energy equation and Darcy's law as momentum have been used. Due to similarity solution we consider only large wall inclination angle. Effects of mass flux, permeability variation function, and wall inclination angle on thermal and velocity boundary layer thickness and heat transfer at the wall are investigated. Copyright © 2005 by ASME  

According to the importance of polyanion cathode materials in intercalation batteries, they may play a significant role in energy-storage systems. Here, evaluations of LiMBO3 and NaMBO3 (M = Mn, Fe, Co, Ni) as cathode materials of Li-ion and Na-ion batteries, respectively, are performed in the density functional theory (DFT) framework. The structural properties, structural stability after deintercalation, cell voltage, electrical conductivity, and rate capability of the cathodes are assessed. As a result, Li compounds have more structural stability and energy density than Na compounds in the C2/c frame structure. Cell voltage is increased by increasing the atomic number of the transition... 

Li2MSiO4 (M = Fe, Mn, etc.) are promising cathode materials for Li-ion batteries. One appealing strategy for improving their cathode properties is to develop mixed transition metal compounds. Density Functional Theory calculations were performed to evaluate the structural, magnetic and electrochemical properties of Li2M0.5N 0.5SiO4 compounds. Our theoretical study allows us to individuate the most promising candidates for practical applications in lithium batteries. © 2013 the Owner Societies  

The performance of a quartz crystal microbalance (QCM) used as a sensor/detector relies on the performance and quality of the film coated onto the quartz crystal sensor. This study focuses on the sensor coating preparation for the detection of glycine. Cellulose nanofibrils (CNFs), natural polymers, were coated on a quartz crystal (QC) surface by a spin-coating method. The prepared CNF-coated QC was characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), cyclic voltammetry (CV), Fourier transform infrared spectrophotometry-attenuated total reflectance (FTIR-ATR), Raman spectroscopy, and water contact angle (WCA). The stable and fully covered QCs without further... 

One of the most relevant negative characteristics of high-capacity cathodes for lithium batteries is indeed non-flat voltage-time (V-t) or voltage-capacity (V-C) behaviour during charge-discharge. A clear rationale for this behaviour has not yet been addressed in the literature. Here, by means of density functional theory (DFT) calculations corroborated by basic experimental electrochemical characterization, we investigated both the thermodynamic and the kinetic aspects relevant to voltage variations during charge-discharge of Li2FeSiO4 intended as a model case. A simple physical model allowed us to take into account all the experimental evidence. We suggested that voltage deviations from...