Smoothed particle hydrodynamics prediction of effective transport coefficients of lithium-ion battery electrodes (original) (raw)
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Modeling of the transport processes in electrodes showing composition-dependent diffusivity
Solid State Ionics, 2004
The work is concerned with the numerical analysis of kinetics and thermodynamics of lithium insertion into electrode materials. The two methods for simulating diffusion in electrode material are shown. The Nernst-Planck flux formula and the law of mass conservation were chosen as the governing equations in a variable diffusivity model (VDM). These equations were solved for the planar electrode and for the different initial and boundary value conditions by means of the finite difference method. The distribution of lithium in the electrode material and the change of the Li + /Li y M half-cell potential are computed. The VDM is compared with a constant diffusivity model (CDM), the results confirm that dependence of the chemical diffusivity of Li on thermodynamics in binary system, M-Li y M, cannot be neglected in practical computations.
Li-ion electrolyte modeling: The impact of adding supportive salts
Journal of Power Sources, 2009
In recent work the ionic transportation properties of organic electrolyte in Li-ion batteries has been described in detail by the present authors, taking into account ionic diffusion and migration processes. Advanced battery electrolytes may, however, be composed of various salts. Therefore the ionic transport properties of such complex electrolytes have been investigated from a theoretical point of view. Detailed information about transient and steady-state behavior of the electrolyte has been simulated, including potential gradients and the diffusion and migration fluxes for all ions. It was found that supportive electrolytes are an effective way to reduce the electric field and, consequently, the migration overpotential. Simultaneously, the diffusion overpotential, in general, increases. Nethertheless, supportive salts reduce the total overpotential across the electrolyte, especially when high currents are applied for short periods of time.
Solid State Ionics, 2016
Numerical models play a vital role in the developing and performance optimization of lithium-ion batteries. The key factor to the prediction accuracy of macro-scale models is the specification of effective transport properties. This study, based on the anisotropic microstructure of graphite anode reconstructed by an ellipsoid-based simulated annealing method (SAM), established a mesoscopic model of diffusion process to predict the effective electric and species transport properties of lithium-ion battery graphite anode via lattice-Boltzmann (LB) method. The effect of particle size on the transport properties of graphite anode was discussed in detail. In the electrode through-plane direction, if the ellipsoidal particles are thinner and flatter, both the effective electric and species transport properties decrease; in the other two directions, the effective electronic charge transport properties barely change with the change of particle size while the effective species transport properties increase along with the increase of the size of particles. In addition, to get a more accurate replica of the real graphite anode, we assumed the sizes of solid particles follow a normal distribution and reconstructed the microstructure of electrode. The LB calculation results reveal that the normal distribution of particle size increases the electronic charge conductivity in the electrode through-plane direction and decreases in the other two directions, compared to the electrode of constant-sized particles; the effective species diffusivities (or ionic charge conductivities) in electrode through-plane direction for different microstructures are closer.
Electrochimica Acta, 2022
The solid-state diffusion coefficient of the electrode active material is one of the key parameters in lithiumion battery modelling. Conventionally, this diffusion coefficient is estimated through the galvanostatic intermittent titration technique (GITT). In this work, the validity of GITT and a faster alternative technique, intermittent current interruption (ICI), are investigated regarding their effectiveness through a black-box testing approach. A Doyle-Fuller-Newman model with parameters for a LiNi0.8Mn0.1Co0.1O2 electrode is used as a fairly faithful representation as a real battery system, and the GITT and ICI experiments are simulated to extract the diffusion coefficient. With the parameters used in this work, the results show that both the GITT and ICI methods can identify the solid-state diffusion coefficient very well compared to the value used as input into the simulation model. The ICI method allows more frequent measurement but the experiment time is 85 % less than what takes to perform a GITT test. Different fitting approaches and fitting length affected the estimation accuracy, however not significantly. Moreover, a thinner electrode, a higher Crate and a greater electrolyte diffusion coefficient will lead to an estimation of a higher solid-state diffusion coefficient, generally closer to the target value.
A Mesoscale Smoothed Particle Hydrodynamics Model for Lithium-Ion Batteries
ACTA PHYSICO-CHIMICA SINICA
We develop a model for the multi-disciplinary transport coupled electrochemical reaction processes in lithium-ion batteries via a smoothed particle hydrodynamics numerical approach. This model is based on a mesoscopic treatment to the micropore structures of electrodes. Focusing on the effects of solid active particle size, this work explores the feasibility of using this model for electrode microstructure design. The model results provide detailed distributive information of all the primary and participating parameters, including Li+ concentration in the electrolyte, Li concentration in solid active particles, solid/electrolyte phase potential, and transfer current density. Furthermore, macroscopic parameters such as the output voltage are also determined. Based on the simulation results, the underlying physicochemical fundamentals are analyzed and the relationships between the macroscopic performance of the battery and the size of solid active particles are revealed. The battery h...
Benchmarking of electrolyte mass transport in next generation lithium batteries
Journal of Electrochemical Science and Engineering, 2017
Beyond conductivity and viscosity, little is often known about the mass transport properties of next generation lithium battery electrolytes, thus, making performance estimation uncertain when concentration gradients are present, as conductivity only describes performance in the absence of these gradients. This study experimentally measured the diffusion resistivity, originating from voltage loss due to a concentration gradient, together with the ohmic resistivity, obtained from ionic conductivity measurements, hence, evaluating electrolytes both with and without the presence of concentration gradients. Under galvanostatic conditions, the concentration gradients, of all electrolytes examined, developed quickly and the diffusion resistivity rapidly dominated the ohmic resistivity. The electrolytes investigated consisted of lithium salt in: room temperature ionic liquids (RTIL), RTIL mixed organic carbonates, dimethyl sulfoxide (DMSO), and a conventional Li-ion battery electrolyte. At steady state the RTIL electrolytes displayed a diffusion resistivity ~ 20 times greater than the ohmic resistivity. The DMSObased electrolyte showed mass transport properties similar to the conventional Li-ion battery electrolyte. In conclusion, the results presented in this study show that the diffusion polarization must be considered in applications where high energy and power density are desired.
Journal of Physical Chemistry B, 2003
This paper describes the mechanisms of ion and electron transport in nanostructured insertion electrode materials such as metal oxide electrochromics and/or Li ion batteries. A general description is given of cases of insertion into a short path region predicted by the geometric disposition of insertion materials in nanostructural electrodes, designed mainly by connected spherical-like particles and nanofibers, both protruding from the current collector substrate. The short path scheme for ion diffusion (nanometer length) permits an ion storage mechanism to be treated as a capacitance charge rather than a diffusion process, an effect that is dubbed the "nanoscale effect". As a result of heterogeneous charge-transfer resistance, the intercalation sites may be seen as the occupation of an ion immobilized-like state. A scheme of an ion trapping-like state represents, in the present case, an ion-binding process occurring during the intercalation reaction, like Li + forming a bond to a bridgingtype oxygen in metal oxide based insertion materials. The model predicts a relaxation process for the intercalation reaction which is more clearly visible in cases of fast transport (occurring throughout the solid and liquid/electrolyte phases of a nanosized macrohomogeneous medium) and/or high state-of-charge. The characteristic frequency of this relaxation process can be used to predict the rate of Li ion intercalation reaction in different nanosized host materials.
Characterisation and modelling of the transport properties in lithium battery gel electrolytes
Electrochimica Acta, 2004
A recent development trend for rechargeable lithium batteries is the use of ternary gel electrolytes. The main advantage of the gels is the mechanical rigidity, which improves as the polymer content is increased. However, the transport properties deteriorate with increasing polymer amount. This dualistic optimisation problem has caused an increased interest in understanding the transport processes in gels, however no full characterisation or modelling study could be found in the literature. In this paper, which is the first part of a study of the transport in the ternary gel system PMMA/PC/LiClO 4 , the liquid electrolyte PC/LiClO 4 is characterised and modelled for concentrations between 0.1 and 2 M according to a previously employed methodology, based on electrochemical measurements. A model using concentration dependent interaction parameters proved to describe the results in the whole concentration region well. The cationic transport number and salt diffusivity were determined to be approximately 0.3 and 1e−10 m 2 /s, respectively. The mean ionic activity factor variations prove to be substantial. Furthermore, it was demonstrated that the inter-ionic friction was important to consider at concentrations above 1 M. The fundamental friction parameters determined in this part will be used in the following part of the study to describe the friction between ions and solvent.
Energies, 2017
Researchers are in search of parameters inside Li-ion batteries that can be utilized to control their external behavior. Physics-based electrochemical model could bridge the gap between Li+ transportation and distribution inside battery and battery performance outside. In this paper, two commercially available Li-ion anode materials: graphite and Lithium titanate (Li 4 Ti 5 O 12 or LTO) were selected and a physics-based electrochemical model was developed based on half-cell assembly and testing. It is found that LTO has a smaller diffusion coefficient (D s) than graphite, which causes a larger overpotential, leading to a smaller capacity utilization and, correspondingly, a shorter duration of constant current charge or discharge. However, in large current applications, LTO performs better than graphite because its effective particle radius decreases with increasing current, leading to enhanced diffusion. In addition, LTO has a higher activation overpotential in its side reactions; its degradation rate is expected to be much smaller than graphite, indicating a longer life span.