Smoothed particle hydrodynamics prediction of effective transport coefficients of lithium-ion battery electrodes (original) (raw)
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.
A review of conduction phenomena in Li-ion batteries
Journal of Power Sources, 2010
Conduction has been one of the main barriers to further improvements in Li-ion batteries and is expected to remain so for the foreseeable future. In an effort to gain a better understanding of the conduction phenomena in Li-ion batteries and enable breakthrough technologies, a comprehensive survey of conduction phenomena in all components of a Li-ion cell incorporating theoretical, experimental, and simulation studies, is presented here. Included are a survey of the fundamentals of electrical and ionic conduction theories; a survey of the critical results, issues and challenges with respect to ionic and electronic conduction in the cathode, anode and electrolyte; a review of the relationship between electrical and ionic conduction for three cathode materials: LiCoO2, LiMn2O4, LiFePO4; a discussion of phase change in graphitic anodes and how it relates to diffusivity and conductivity; and the key conduction issues with organic liquid, solid-state and ionic liquid electrolytes.
Charge and mass transport properties of LiI-P(EO) n Al 2O 3-based composite polymer electrolytes
Electrochimica Acta, 1998
AbstractÐWe recently demonstrated that LiI-P(EO) n -Al 2 O 3 -based composite polymer electrolytes (CPE) appear to be good candidates for use in lithium batteries, providing high conductivity and good electrochemical and thermal stability. The main goals of the present investigation were to study and analyze with the use of linear-sweep-voltametry LSV and AC techniques, charge and mass transport properties of a broad spectrum of CPEs (80 r nr 1.5). The following parameters were determined at 1208C, conductivity (s), Warburg impedance (Z d (0), apparent t + , apparent diusion coecient (D) and limiting-current density for Li deposition. Several assumptions were made: (1) The salt is fully dissociated in the electrolyte, (2) Only the salt cation M + is being reduced, (3) The reaction M + +e 4 M(s) is reversible, (4) There are no adsorption phenomena. It was found that these assumptions are not completely valid at least for concentrated CPEs. An additional arc appears in the Nyquist plot at a low frequency range, indicating the formation of ion pairs or aggregates. However, there were similar dependencies of D and s on n, each going through a maximum at n = 20. The limiting current density, measured for 100 mm thick CPEs increased monotonically from 0.3 to 2.3 mA/cm 2 with n varying from 80 to 9. The calculated values of the limitingcurrent density (with the use of D values determined by AC) and experimental linear-sweep-voltammetry data are in a good agreement. #
Scientific reports, 2016
Underutilization due to performance limitations imposed by species and charge transports is one of the key issues that persist with various lithium-ion batteries. To elucidate the relevant mechanisms, two groups of characteristic parameters were proposed. The first group contains three characteristic time parameters, namely: (1) te, which characterizes the Li-ion transport rate in the electrolyte phase, (2) ts, characterizing the lithium diffusion rate in the solid active materials, and (3) tc, describing the local Li-ion depletion rate in electrolyte phase at the electrolyte/electrode interface due to electrochemical reactions. The second group contains two electric resistance parameters: Re and Rs, which represent respectively, the equivalent ionic transport resistance and the effective electronic transport resistance in the electrode. Electrochemical modeling and simulations to the discharge process of LiCoO2 cells reveal that: (1) if te, ts and tc are on the same order of magnit...