Representative elementary volume

About: Representative elementary volume is a research topic. Over the lifetime, 4105 publications have been published within this topic receiving 86863 citations.

A consistently coupled multiscale mechanical–electrochemical battery model with particle interaction and its validation

Abstract: As an inherent multiscale structure, a continuum scale battery electrode is composed of many microscale particles. Currently it is generally assumed that each particle is isolated while the stress in a particle only affects solid diffusion. The lack of mechanical interaction between particles and effect of stress on the electrochemical reaction rate makes mechanics and electrochemistry uncoupled at the continuum scale: an applied continuum scale stress in the electrode has no effect on the spatial distribution of electrochemical reaction in the electrode and vice versa. This paper first presents a multiscale model that couples mechanics and electrochemistry consistently at the microscopic and continuum scales. The microscopic particle stress is a superposition of the intra-particle concentration gradient-induced stress and the particle interaction stress, with the latter being related to the continuum scale stress through a representative volume element. The electrochemical charge transfer kinetics is generalized with the stress effect. Diffusion in a particle is described by a chemical potential that includes stress and phase transition. In a parallel effort, we develop a direct three-dimensional particle network model, which consists of realistic active material particles. Unlike the multiscale model, there is no scale separation and homogenization in the particle network model: all particles are modeled explicitly with fully coupled three-dimensional mechanical-electrochemical equations and the finite element method. The results from the particle network model are accurate and can serve as a standard, but the size of particle network that can be calculated is limited due to high computational cost. Comparison of results from the multiscale model and from the particle network model shows that the multiscale model gives good, satisfying accuracy while reducing the computational cost dramatically in comparison to the three-dimensional particle network model. The multiscale model is a power tool to address various coupled problems in the electrode, from inter-particle crack growth to electrode structure design for high performance and long cycle life.

Predictive Model of Graphene Based Polymer Nanocomposites: Electrical Performance

Abstract: In this computational work, a new simulation tool on the graphene/polymer nanocomposites electrical response is developed based on the finite element method (FEM). This approach is built on the multi-scale multi-physics format, consisting of a unit cell and a representative volume element (RVE). The FE methodology is proven to be a reliable and flexible tool on the simulation of the electrical response without inducing the complexity of raw programming codes, while it is able to model any geometry, thus the response of any component. This characteristic is supported by its ability in preliminary stage to predict accurately the percolation threshold of experimental material structures and its sensitivity on the effect of different manufacturing methodologies. Especially, the percolation threshold of two material structures of the same constituents (PVDF/Graphene) prepared with different methods was predicted highlighting the effect of the material preparation on the filler distribution, percolation probability and percolation threshold. The assumption of the random filler distribution was proven to be efficient on modelling material structures obtained by solution methods, while the through-the –thickness normal particle distribution was more appropriate for nanocomposites constructed by film hot-pressing. Moreover, the parametrical analysis examine the effect of each parameter on the variables of the percolation law. These graphs could be used as a preliminary design tool for more effective material system manufacturing.