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Shedding light onto the processes that limit the fast charging of alkali-ion battery cells constitutes a hotspot area. In the present work, we study two of the most important ones at the microscopic level: charge transfer at the interface and diffusion of ions inside the electrodes, focusing on how the geometry of particles regulates these kinetic limitations. The results are presented in maps of reversibility and finiteness of diffusion constructed from hundreds of voltammetric numerical simulations at different operating conditions. The diagrams obtained with different geometries are given a straightforward physical interpretation. This helps to understand in depth the phenomena that regulate the charging of cells, and so to promote a rational design of fast-charging electrode materials. [ABSTRACT FROM AUTHOR]

Here, we report on a novel study for battery application regarding the impact of interactions in charge transfer and diffusional features in finite-size systems. An easy way to represent these features is the construction of a map called zone diagram for voltammetry simulations, where different domains are related with a characteristic charge transfer-diffusional limitation. This is particularly relevant for alkali-ion intercalation into hosts, since interactions between inserted ions have demonstrated to have a strong influence on the electrochemical behaviour of these systems. The Frumkin isotherm is used here as a general model to understand the simplest scenarios, which introduces interactions between inserted particles in their thermodynamic descriptions. We show how the impact of these interactions becomes more evident for systems that present a reversible charge transfer. On the contrary, for irreversible reactions, features tend to become independent of interactions. Finally, we apply the methodology to understand some features of Li-ion intercalation in graphite films. It comes out that for this system, a surface wave (adsorption like) behaviour could only be reached in experiments lasting more than a year. This explains the large hysteresis found in experiments. We also constructed a sweep rate-film thickness zone diagram, to present the results in a more straightforward fashion to experimentalists. [ABSTRACT FROM AUTHOR]

In the present work we consider those theories that are obtained from a Lagrangian density ℒ T( R) = f( R)√{-g} + ℒ M, that depends on the curvature scalar and a matter Lagrangian that does not depend on the connection, and apply Palatini's method to obtain the field equations. We start with a brief discussion of the field equations of the theory and apply them to a cosmological model described by the FRW metric. Then, we introduce an auxiliary metric to put the resultant equations into the form of GR with cosmological constant and coupling constant that are curvature depending. We show that we reproduce known results for the quadratic case. We find relations among the present values of the cosmological parameters q0, H0, $$\mathop {(G/G)}\limits^ \circ _0$$ and $$\mathop {(G/G)}\limits^{ \circ \circ } _0 $$ . Next we use a simple perturbation scheme to find the departure in angular diameter distance with respect to General Relativity. Finally, we use the observational data to estimate the order of magnitude of what is essentially the departure of f( R) from linearity. The bound that we find for f″ (0) is so huge that permit almost any f( R). This is in the nature of things: the effect of higher order terms in f( R) are strongly suppressed by power of Planck's time 8π G0. In order to improve these bounds more research on mathematical aspects of these theories and experimental consequences is necessary. [ABSTRACT FROM AUTHOR]

We consider a class of fourth order theories of gravity with arbitrary matter fields arising from a diffeomorphism invariant Lagrangian density $$\mathcal{L}_T = \mathcal{L}_G + \mathcal{L}_M$$ , with $$\mathcal{L}_G = \sqrt { - g} \left[ {R + h\left( R \right)} \right]$$ and $$\mathcal{L}_M$$ the phenomenological representation of the nongravitational fields. We derive first the generalization of the Einstein pseudotensor and the von Freud superpotential. We then show, using the arbitrariness that is always present in the choice of pseudotensor and superpotential, that we can choose these superpotentials to have the same form as those for the Hilbert Lagrangian of general relativity (GR). In particular we may introduce the Moller superpotential of GR as associated with a double-index differential conservation law. Similarly, using the Moller superpotential we prove that we can choose the Komar vector of GR to construct a conserved quantity for isolated asymptotically flat systems. For the example R + R2theory we prove then, that the active mass is equal to the total energy (or inertial mass) of the system. [ABSTRACT FROM AUTHOR]

The present article comments on the article of Stephen Fletcher (Journal of Solid State Electrochemistry Volume 18, Issue 5, pp 1231-1238). The analysis deals with the validity of equation (31 or 40) of the latter for an ideally polarisable interface. [ABSTRACT FROM AUTHOR]

In this work, we evaluate the reliability of a recently developed model for estimating kinetic parameters for different materials used in lithium-ion batteries. This model considers non-interacting Li-ions being inserted under constant current conditions, assuming finite diffusion inside the particles and charge transfer limitations at the electrode/electrolyte interface. Here, we are interested in evaluating the effect of neglecting the particular insertion isotherms of the materials on the fittings made for diffusion coefficients and electrochemical rate constants. With this purpose, equilibrium isotherms of different materials are extracted from an open-access Li-ion battery parameter database. This thermodynamic information is introduced into the model to perform simulations and obtain the maximum state of charge reached as a function of C-rate. This data is then fitted to the model without interactions using our open-source Python package. The fitted values obtained for the diffusion coefficients are finally compared with the reference values from the database to estimate the accuracy of the model for different real-world systems. [ABSTRACT FROM AUTHOR]