This study considers application-oriented models of lithium-sulfur (Li-S) cells. Existing ECN models often neglect self-discharge, but this can be important in applications. After describing the context in which control-oriented models and estimators are based, the self-discharge phenomenon is investigated for a new 21 Ah Li-S cell. As a contribution of this study, an equivalent-circuit-network (ECN) model was extended to account for cells' self-discharge. Formal system identification techniques were used to parameterize a model from experimental data. The original model was then extended by adding terms to represent a self-discharge resistance. To obtain the self-discharge resistance, a particular new series of experiments were designed and performed on the Li-S cell at various temperature and initial state-of-charge (SoC) levels. The results demonstrate the dependency of self-discharge rate on the SoC and temperature. The self-discharge rate is much higher at high SoC levels and it increases as temperature decreases. Much of today's research into lithium-sulfur (Li-S) batteries concerns the development and understanding of materials, construction and the fundamental scientific understanding of cell behavior. Many will recognize the importance of this, but lithium-sulfur is beginning to reach maturity, and there is a need to develop the engineering science and techniques necessary for deployment in practical applications. In particular, there is a need to devise algorithms that can be used to estimate state-of-charge and state-of-health measures in operando. Electrochemistry is of course key here, but it is equally vital to draw from other disciplines: in particular, control theory has much to offer, particularly in respect of state estimation.When electrochemists create models, they usually do so 'as scientists': the aim of a scientific model is to enhance understanding. Of course, no model is perfect, and the pure scientist uses model imperfections to identify gaps in present knowledge and as the inspiration for further research. The aim is to improve understanding and get a 'better model'. However, at some point, cells may be put to practical use, and at this point, the application engineer will often have to make do with the best models available at that time, despite the model's imperfections.Control systems engineers are well accustomed to dealing with model errors and 'uncertainty': there are many excellent text books on control, and any of them will give a short overview of the key principles of control; Aström and Murray's work 1 is a good example. Typically, a dynamic system is modelled as a set of dynamic equations: x, u, w) [1]where u and y represent observed system input and outputs (voltages, currents and temperatures, for example), x comprehensively accounts for past history by representing the system's non-or partlymeasurable dynamic 'states' (perhaps including state of charge in a simple model, or concentrations of chemical species in a complex one), h(·) and f (·) are known functions describ...

In this study, first-principles density functional theory (DFT) calculations of the structural and optoelectronic properties of Sn-based inorganic metal halide perovskite CsSnBr3 are carried out and discussed in details. The Wu-Cohen (WC)-Generalized Gradient Approximation (GGA) based on the full-potential linearized augmented plane-wave (FPLAPW) method is used to optimize the geometry structure of unit cell and then find the accurate optoelectronic properties of CsSnBr3. Analysis of structural optimization results revealed that the lattice parameters (𝑎0 = 5.776 Å) and unit cell volume of CsSnBr3 are exactly consistent with the experiments reports. Based on the results of band structures and density of states, CsSnBr3 is found to be nonmagnetic semiconductor with suitable direct band gap of (Eg = 0.610 eV) along the R symmetry point. In addition, the calculations of optical properties of CsSnBr3, such as the real 𝜀1 (𝜔) and imaginary 𝜀2 (𝜔) parts of the dielectric function, 𝜀(𝜔), absorption coefficient 𝛼(𝜔), reflectivity 𝑅(𝜔) and refractive index 𝑛(𝜔), have been performed in the photonic energy range of (0.0 – 15.0 eV). Finally, the results attained in the present study, which include the stable crystal structure and the high accurate optoelectronic properties such as appropriate direct band gap and high absorption of visible radiation, confirm the possible utilization of CsSnBr3 materials in novel optoelectronics applications as photovoltaic solar cells, photosensors, photodetectors, photodiodes and other related optoelectronics devices