Effect of Misfit Dislocation on Li Diffusion and Stress in a Phase Transforming Spherical Electrode

Abstract

The Li-ion battery electrode materials generally experience significant volume change during lithium diffusion. These volume changes lead to diffusion induced stress. Diffusion induced stress(DIS) will cause fracture and nucleation in the electrode. Many electrode materials undergo formation of two or more phases during lithium insertion. By analyzing the process of lithiation, the DIS in phase transforming electrodes using a core-shell model structural is investigated. The new model considering the misfit dislocation effect is established to analyze the stress distribution in the nanoparticle electrode. We observe that the magnitude of DIS can be affected by the misfit dislocation. In addition, the concentration jumps is also affected by the misfit at phase boundaries that result in stress discontinuities, which in turn can cause cracking. The influence of the mechanical properties of the two phases on stress evolution, stress discontinuity, and misfit dislocation effect are clarified. What's more, the Tresca stress is also expounded in the Li-ion battery. The effect of misfit dislocation and the phase transforming on the Tresca stress is clarified. The trends obtained with the model may be used to help tune electrode materials with appropriate interfacial and the misfit dislocation so as to increase the durability of battery electrodes. Li-ion battery is widely used in portable equipment because of their high energy density, high efficiency of charging and low weight compared to conventional cells.1-3 To achieve a higher energy density in the Li-ion battery, new anode materials are being intensively studied as potential such as silicon. However, many investigations [4][5] found that there exist very large stress and volume change during lithiation. Si 6-9 is one of the most promising anode materials used in Li-ion battery electrode because of a theoretical capacity of 4200 mAhg −1 with the formation of Li 4.4 Si. However, owing to volume change (up to 400%), [10][11][12] there is a large stress which leads to serious electrode irreversible capacity and poor cyclability during lithiation. 13So a large number of literature had been devoted to the modeling of Li-ion battery using volume-averaged methods to analyze the fracture phenomena in the electrode particle.14-16 Recently, we [17][18][19] have analyzed the effects of dislocation and bend of nano-scaled electrodes on the stresses or strain energy and proposed fracture criteria for insertion electrodes.However, It is known that lithium insertion often leads to the formation of lithiation and delithiation phase depending on electrode materials and the state of charge in Li-ion battery. In studying the stress evolution during electrochemical cycling, the current research approach used in the community of Li-ion battery has strongly relied on DIS, which is based on the theory of linear elasticity. Many of these models assume that the electrode particle remains in single phase during lithiation. Aifantis et al. 20 adopted Griffith's criteria to estimate the critic...

Current and deformation induced by voltage in the single LiNi0.8Co0.1Mn0.1O2 particle from atomic force microscopy technique and phase field simulation

“…Based on the SEM morphology shown in figure 1, the majority of particles have an irregular geometric shape. Meanwhile, the diffusion rule of lithium-ion inside the particle is unaffected by local small changes in particle surface morphology [22]. As a result, for computational purposes, the individual grains are approximated to be spherical.…”

Interaction between dislocation mechanics on diffusion induced stress and electrochemical reaction in a spherical lithium ion battery electrode

“…20 Sanboh Lee et al studied DIS in a hollow cylinder. 26 Chen et al 27,28 analyzed the distribution of dislocation in nanostructured thin film electrode and the effect of misfit dislocation on Li-ion diffusion and stress in spherical electrode. 22 Bucci et al analyzed two separate electrochemical reactions at the Si/electrolyte interface to characterize the mechanical and electrochemical response of thin film amorphous Si electrodes during cyclic lithiation.…”

“…25 Li et al provided an analytical modeling of dislocation effect on DIS in a cylindrical lithium ion battery electrode. 26 Chen et al 27,28 analyzed the distribution of dislocation in a nanostructured thin lm electrode and the effect of mist dislocation on Li-ion diffusion and stress in a spherical electrode. Cheng et al used a thermal stress analysis approach to investigate DIS evolution at the two-phase boundary during the lithiation process.…”

Computational Modeling of Heterogeneity of Stress, Charge, and Cyclic Damage in Composite Electrodes of Li-Ion Batteries

“…Early work of single-particle active materials started from Christensen and Newman 29 who studied the effect of mechanical stresses on Li diffusion in a free-standing spherical particle. Refined work since then has been reported incorporating other relevant mechanisms such as the effects of large deformation, 30,31 particle size and shape, 32 phase transformation, 33,34 plasticity, 24 and varying material properties. 35 The single-particle/phase models can provide an understanding of the first-order effect of stress in regulating the Li transport and surface charge transfer, but the model is apparently oversimplified and cannot capture the electrochemical response and the mechanics field in real composite electrodes.…”