A pore-scale smoothed particle hydrodynamics model for lithiumion batteries

A mesoscopic pore-scale model of multi-disciplinary processes coupled with electrochemical reactions in lithium-ion batteries is established via a relatively novel numerical method—smoothed particle hydrodynamics(SPH)method.This model is based on mesoscopic treatment to the electrode(including separator)micro-pore structures and solves a group of inter-coupled SPH equations,including charge(ion in electrolyte phase and electron in solid phase),species(Li+ in electrolyte phase and lithium in solid active materials),and energy conservation equations.Model parameters,e.g.the physicochemical properties are location-dependent,directly associated with the local component of the medium.The electrochemical reactions are prescribed to occur exactly at the interface of solid active materials and electrolyte.Simulations to isothermal discharge processes of a battery of 2-dimensional idealized micro-pore structure in electrodes and separator preliminarily corroborate the reasonability and capability of the developed SPH model

A pore-scale smoothed particle hydrodynamics model for lithium-ion batteries

A mesoscopic pore-scale model of multi-disciplinary processes coupled with electrochemical reactions in lithium-ion batteries is established via a relatively novel numerical method-smoothed particle hydrodynamics (SPH) method. This model is based on mesoscopic treatment to the electrode (including separator) micro-pore structures and solves a group of inter-coupled SPH equations, including charge (ion in electrolyte phase and electron in solid phase), species (Li+ in electrolyte phase and lithium in solid active materials), and energy conservation equations. Model parameters, e.g. the physicochemical properties are location-dependent, directly associated with the local component of the medium. The electrochemical reactions are prescribed to occur exactly at the interface of solid active materials and electrolyte. Simulations to isothermal discharge processes of a battery of 2-dimensional idealized micro-pore structure in electrodes and separator preliminarily corroborate the reasonability and capability of the developed SPH model

Smoothed particle hydrodynamics prediction of effective transport coefficients of lithium-ion battery electrodes

We develop a three-dimensional virtual physical property test platform based on the smoothed particle hydrodynamics (SPH) method for the prediction of the effective transport coefficients, including the effective thermal conductivity, effective electronic conductivity, and effective Li+ species diffusivity of LiCoO2 electrodes of various microstructures. The three-dimensional microstructure of the LiCoO2 electrode is reconstructed by a sphere-based simulated annealing method. SPH simulation results corroborate that the transport processes are strongly affected by the electrode microstructure. The calculated effective thermal conductivity by SPH model agrees well with the theoretical predictions by a semi-empirical effective medium model, while the effective medium model generally gives smaller effective electronic conductivity of the electrode than the SPH model. Comparing the SPH-predicted effective Li+ species diffusivity with the commonly-used Bruggeman approximation finds that the latter generally overestimates the effective Li+ species diffusivity of the electrode. Furthermore, we derive the formation factor of electrolyte phase in the reconstructed electrode. It is found that the formation factors calculated from SPH results are in good agreement with former experimental data. (C) 2014 Elsevier B.V. All rights reserved

Direct Numerical Simulation Modeling of Multidisciplinary Transport during Li-Ion Battery Charge/Discharge Processes

We develop a direct numerical simulation (DNS) model of multidisciplinary transport coupled with electrochemical reactions during Li-ion battery charge/discharge processes based on the finite volume (FV) numerical technique. Different from macroscopic models, the DNS model is based on microstructure of composite electrodes and solves component-wise transport equations. During DNS, the input physical properties are intrinsic material properties, not effective physical properties for macroscopic models. Since the interface of solid and electrolyte phase is evidently differentiated in DNS, the occurrence of electrochemical reactions is prescribed exactly on the interface of solid and electrolyte phase. Therefore, the DNS model has the potential to unravel the underlying mesoscopic pore-scale mechanisms of multi-disciplinary transport coupled with electrochemical reactions and thus can provide insightful information of the involved processes, as well as enables the design and optimization of electrodes, including microstructures inside electrodes. One test case, in which the electrode microstructure is reconstructed with a purely random reconstruction method, is considered. Simulation results corroborate the validity of the DNS model

Direct Numerical Simulation Modeling of Multidisciplinary Transport during Li-Ion Battery Charge/Discharge Processes

We develop a direct numerical simulation (DNS) model of multidisciplinary transport coupled with electrochemical reactions during Li-ion battery charge/discharge processes based on the finite volume (FV) numerical technique. Different from macroscopic models, the DNS model is based on microstructure of composite electrodes and solves component-wise transport equations. During DNS, the input physical properties are intrinsic material properties, not effective physical properties for macroscopic models. Since the interface of solid and electrolyte phase is evidently differentiated in DNS, the occurrence of electrochemical reactions is prescribed exactly on the interface of solid and electrolyte phase. Therefore, the DNS model has the potential to unravel the underlying mesoscopic pore-scale mechanisms of multi-disciplinary transport coupled with electrochemical reactions and thus can provide insightful information of the involved processes, as well as enables the design and optimization of electrodes, including microstructures inside electrodes. One test case, in which the electrode microstructure is reconstructed with a purely random reconstruction method, is considered. Simulation results corroborate the validity of the DNS model

Numerical reconstruction of microstructure of graphite anode of lithium-ion battery

Due to the presence of graphite flake cascades, the real graphite anode of Li-ion battery shows non-isotropic characteristic. The present work developed an ellipsoid-based simulated annealing method and numerically reconstructed the three-dimensional microstructure of a graphite anode. The reconstructed anode is a composite of three clearly distinguished phases: pore (or electrolyte), graphite, and solid additives, well representing the non-isotropic heterogeneous characteristic of real graphite anode. Characterization analysis of the reconstructed electrode gives information such as the connectivity of individual phase, the specific interfacial area between solid and pore phase, and the pore size distribution. The effects of the ellipsoid size on the structural characteristics of graphite anode were particularly studied. As the size of the ellipsoidal particle slightly increases, the average pore diameter increases and as a result the specific interfacial area between the solid and pore phase in the reconstructed area decreases; compared with the equatorial radius, the polar radius of ellipsoidal graphite particles has more significant influence on the characteristics of electrode microstructure

Numerical reconstruction of microstructure of graphite anode of lithium-ion battery

Due to the presence of graphite flake cascades, the real graphite anode of Li-ion battery shows non-isotropic characteristic. The present work developed an ellipsoid-based simulated annealing method and numerically reconstructed the three-dimensional microstructure of a graphite anode. The reconstructed anode is a composite of three clearly distinguished phases: pore (or electrolyte), graphite, and solid additives, well representing the non-isotropic heterogeneous characteristic of real graphite anode. Characterization analysis of the reconstructed electrode gives information such as the connectivity of individual phase, the specific interfacial area between solid and pore phase, and the pore size distribution. The effects of the ellipsoid size on the structural characteristics of graphite anode were particularly studied. As the size of the ellipsoidal particle slightly increases, the average pore diameter increases and as a result the specific interfacial area between the solid and pore phase in the reconstructed area decreases; compared with the equatorial radius, the polar radius of ellipsoidal graphite particles has more significant influence on the characteristics of electrode microstructure

SIMULATION OF FLOW BOILING OF NANOFLUID IN TUBE BASED ON LATTICE BOLTZMANN MODEL

In this study, a lattice Boltzmann model of bubble flow boiling in a tube is established. The bubble growth, integration, and departure of 3% Al2O3-water nanofluid in the process of flow boiling are selected to simulate. The effects of different bubble distances and lateral accelerations a on the bubble growth process and the effect of heat transfer are investigated. Results showed that with an increase in the bubble distance, the bubble coalescence and the effect of heat transfer become gradual. With an increase in lateral acceleration a, the bubble growth is different. When a = 0.5e-7 and a = 0.5e-6, the bubble growth includes the process of bubble growth, coalescence, detachment, and fusion with the top bubble and when a = 0.5e-5 and a = 0.5e-4, the bubbles only experience growth and fusion, and the bubbles do not merge with the top bubble directly to the right movement because the lateral acceleration is too large, resulting in the enhanced effect of heat transfer in the tube

On equations of state in pseudo-potential multiphase lattice Boltzmann model with large density ratio

In this paper, a single-component pseudo-potential model is analyzed by modifying corresponding equation of state. Simulation results show that with the modified vdW equation, this model is capable to simulate the multiphase flow with greater range of density ratio than other existing multiphase models and some drawbacks of pseudo-potential model such as large spurious currents are avoided as well. Besides, the influences of the modified method on surface tension are studied. Also, two other typical equations of state are employed, and the simulation results show that both of them work very well under any characteristic temperature and the greatest density ratio could be up to 10(9). (C) 2013 Elsevier Ltd. All rights reserved

THE STUDY OF NATURAL CONVECTION HEAT TRANSFER OF NANOFLUIDS IN A PARTIALLY POROUS CAVITY BASED ON LATTICE BOLTZMANN METHOD

This article used the lattice Boltzmann method to study the heat transmission of natural convective of nanofluids in a 2-D square cavity partially filled with porous medium. The nanoparticles volume fraction of A1203, Cu, and Si02 were 0.5%, 1%, 1.5%, 2%,.5/,06, and 4%, which were mixed with water and 70% of ethylene glycol aqueous solution as the base fluid, and made up six kinds of nanofluids as the research object. Using nanofluids coupled double distribution lattice Boltzmann method model, this paper studied the rules of natural convection heat transfer of different nanofluids with the changing of Rayleigh number and the concentration of the nanoparticles in the 2-D square cavity partially filled with porous medium. The results showed that the average Nusselt number of the hot wall will increase with the increase of Rayleigh number number, and under different heat transfer conditions, there are two different critical Rayleigh numbers. In the case of different concentrations of the same concentration, the critical Rayleigh number is about 105, when Ra > Rae, the average Nusselt number of water is higher; when Ra Rae, there is a slight decreasing in the average Nusselt number with the increasing of concentration. The critical Rayleigh number of water as the base fluid is smaller than that of ethylene glycol as the base fluid