Concentration-Dependent Chemical Expansion in Lithium-Ion Battery Cathode Particles

Abstract

In this work, the effect of the concentration-dependent chemical-expansion coefficient, /?, on the chemo-elastic field in lithium-ion cathode particles is examined. To accomplish this, an isotropic linear-elastic model is developed for a single idealistic particle sub jected to potentiostatic-discharge and charge conditions. It is shown that p can be a key parameter in demarcating the chemo-stress-strain state of the cathode material under going nonlinear volumetric strains. As an example, such strains develop in the hexagonal-to-monoclinic-phase region of LixCoO 2 (0.37 < x< 0.55) and, subsequently, the corresponding p is a linear function of concentration. Previous studies have assumed a constant value for p. Findings suggest that the composition-generated chemo-elastic field that is based on a linear-p dramatically affects both the interdiffusion and the me chanical behavior of the LixCo02 cathode particle. Because the chemo-elastic phenom ena emanate in a reciprocal fashion, the resulting linear P-based hydrostatic-stress gradients significantly aid the diffusion of lithium. Thus, diffusion is accelerated in either electrochemical process that the cathode material undergoes.

Diffusion-induced stress in a functionally graded incompressible elastic sphere

“…Note that in (18) the boundedness of the solution at R = 0 has been considered, as well as condition (14) and that such solution is consistent with that obtained for the equivalent thermal-stress problem [16] (although the reference refers to the compressible case). By denoting the derivative with respect to R also by the 'prime'symbol, the displacement u is related to its first and second space derivative by…”

“…The potential given in ( 8) is widely employed in the context of LIBs (see for example [23,69,70] or the recent review [5] and references therein for further details and its derivation, which is beyond the scope of this investigation). When potential ( 8) is stress-independent, the classical Fickian diffusion law in 6 can be recovered (see [14] for further details).…”

“…This stress field is known as diffusion-induced stress (DIS)(see [7,8,9,10,5] and references therein). To investigate DIS, several models (see [11,12,13,14,15,10] to name but a few more recent works), have adopted methods similar to the thermal stress models [16,17] following the pioneering work of Prussin [18].…”

Computational modeling of Li-ion batteries

“…The microscopic arrangement of active particles, carbon, binder and pores can be recovered from statistical analyses of 2D cross sections of the electrode achieved through scanning electron microscope with focused ion beam. The particle geometry can either be a simplified abstraction of reality -for example using cluster of spherical [74,145] or ellipsoidal [146] particles that yet represent challenges for computational discretization [147,148] -or be digital reconstruction of realistic morphology [149,150,151,152,153,154,155] -generally restricted to single-particle analyses.…”

“…A few attempts only accounted for realistic microstructure of porous electrodes considering the temperature field and the hot spots formation under extreme conditions in a multi-scale and multi-physics framework [170,62,153].…”