Kinematic hardening analysis of Li-ion battery with concentration-dependent material behaviours under cyclic charging and discharging

Abstract

Variation of stress and deformation in Li-ion batteries with a bilayer anode structure is studied in this research. Material properties vary due to the lithiation and delithiation. This important effect is considered in the modelling of elastic and plastic deformation. The diffusion equation with the variable coefficient is solved numerically, and the effect of the variable diffusion coefficient is investigated. Mechanical properties of the silicon, as a function of the lithium concentration, are characterized by using the available experimental and the molecular dynamics simulations results. Stress and deformation variation across the thickness and during the charging-discharging operations are obtained by using variable mechanical properties and Chaboche's nonlinear kinematic hardening model. Numerical results compare well with the experimental results, and it is elucidated that considering plastic deformation has a significant influence on the battery deformation and stress distribution. The cyclic loading answer of the electrodes is also studied. Shakedown or ratcheting answers can occur. Finally, it is shown that the thickness ratio of the electrode layers has an essential effect on the maximum stress and deformation in the bilayer electrode.