Modelling stress-affected chemical reactions in non-linear viscoelastic solids with application to lithiation reaction in spherical Si particles

This paper aims at modelling stress-affected chemical reactions in spherical particles by adopting the chemomechanical framework based on the chemical affinity tensor and combining it with the finite-strain non-linear viscoelastic constitutive model. The model is applied to the chemical reaction between lithium (Li) ions and silicon (Si), which has been considered as promising successor to graphite for use as active material in lithium-ion battery (LIB) anodes. However, during charging of LIBs, Si enters into the chemical reaction with Li ions, causing large volumetric expansion of Si particles, which leads to the emergence of mechanical stresses, which, in turn, can affect the kinetics of the chemical reaction even up to the reaction arrest. In this paper, the propagation of the reaction front separating the chemically transformed and the untransformed phases is modelled, and the coupled stress-diffusion-reaction problem is solved using the finite element approach. The model predicts the retardation and the locking of the chemical reaction in Si depending on the values of the chemical energy parameter, which corresponds to experimental observations

Genome-wide association meta-analysis identifies 48 risk variants and highlights the role of the stria vascularis in hearing loss

Hearing loss is one of the top contributors to years lived with disability and is a risk factor for dementia. Molecular evidence on the cellular origins of hearing loss in humans is growing. Here, we performed a genome-wide association meta-analysis of clinically diagnosed and self-reported hearing impairment on 723,266 individuals and identified 48 significant loci, 10 of which are novel. A large proportion of associations comprised missense variants, half of which lie within known familial hearing loss loci. We used single-cell RNA-sequencing data from mouse cochlea and brain and mapped common-variant genomic results to spindle, root, and basal cells from the stria vascularis, a structure in the cochlea necessary for normal hearing. Our findings indicate the importance of the stria vascularis in the mechanism of hearing impairment, providing future paths for developing targets for therapeutic intervention in hearing loss

Micromechanical modelling of mechanochemical processes in heterogeneous materials

There is a range of practical problems where advanced engineering heterogeneous materials undergo chemical transformations. The primary example of such system is energy storage materials, in particular anodes of Li-ion batteries containing active Si particles. The exploitation of such anodes involves extreme volumetric expansion of the active particles during the chemical reaction. The expansion is causing mechanical stress, which, in turn, influences the kinetics of chemical reactions even up to their arrest. A particular reaction between Si and Li is localised, as well as a number of other reactions, such as oxidation or precipitate formation. The model presented in this paper accounts for the kinetics of the reactions in a collection of particles inside a matrix material. The microstructure is modelled using the multiscale mean-field framework based on the incremental Mori-Tanaka method. This is the first application of a multiscale mean-field technique to modelling reaction front kinetics in particles and linking the intra-particle kinetics with the response of the matrix. A number of physical effects arising from the influence of the deformation mechanisms of the matrix on the kinetics of the intra-particle reactions is investigated. Furthermore, the applicability of the proposed model and the incremental Mori-Tanaka homogenisation scheme is studied by comparison to the full-field simulations in the cases of small and finite strains

On chemical reaction planar fronts in an elastic–viscoelastic mechanical framework

A stress-affected chemical reaction front propagation is considered using the concept of a chemical affinity tensor. A reaction between an elastic solid constituent and a diffusing constituent, localized at the reaction front, is considered. As a result of the reaction, the elastic constituent transforms into viscoelastic one. The reaction is accompanied by volume expansion that in turn may result in stresses at the reaction front, which affect the front velocity through the normal component of the chemical affinity tensor. Considering a plane strain problem with a planar chemical reaction front propagation under uniaxial deformation, we focus on the studies of the reaction front kinetics in dependence on external strains and material parameters with the use of the notion of the equilibrium concentration. Then, stress relaxation behind the propagating reaction front is modeled. A standard linear solid model is used for the reaction product, and its particular cases are also considered. Analytical solutions are obtained which allow to study in explicit form the strain influence and material parameters on the front retardation or acceleration and stress relaxation. Keywords Mechanochemistry • Chemical affinity tensor • Reaction front kinetics • Stress relaxation • Standard linear solid model Communicated by Andreas Öchsner

Si Nanopowder Based Anode Material for the Lithium Ion Battery Cell

Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG geförderten) Allianz- bzw. Nationallizenz frei zugänglich.This publication is with permission of the rights owner freely accessible due to an Alliance licence and a national licence (funded by the DFG, German Research Foundation) respectively.We consider a silicon nanopowder based anode for a lithium ion battery cell. We present the design of the battery cell ready for in situ Raman and X-ray experiments and a technical procedure for the cell manufacturing. From the continuum mechanics point of view, this type of anode can be represented by a spherical nanoparticle surrounded by viscoelastic matrix. During the charging process this nanoparticle undergoes a chemical reaction. Based on the chemical affinity concept we describe how the mechanical properties of the matrix material influence the kinetics of the charging process. We study spherically symmetry problems numerically for different sets of matrix material parameters and show their influence on the reaction front kinetics

Modeling chemical reaction front propagation by using an isogeometric analysis

We develop a numerical procedure for solving boundary value problems for elastic solids undergoing chemical transformations. The kinetic equation for the reaction front propagation is based on an expression for the chemical affinity tensor, which allows us to study the influence of stresses and strains on the chemical reaction rate and the normal component of the reaction front velocity. Isogeometric analysis provides a high accuracy when finding the normal to the reaction front, and it is applied with the use of Abaqus to a numerical simulation of the front propagation. In order to test and demonstrate the capabilities of the developed procedure a hollow cylinder undergoing a chemical transformation is considered. First, an axially-symmetric problem is solved and a good agreement between numerical simulations and analytical results is demonstrated. Then a case is considered where the initial front configuration does not have axial symmetry. Reaction front acceleration, retardation, and even reaction blocking due to mechanical stresses are investigated.Peer reviewe