Implementing Realistic Geometry and Measured Diffusion Coefficients into Single Particle Electrode Modeling Based on Experiments with Single LiMn2O4 Spinel Particles

Abstract

Realistic geometry and diffusion coefficients were measured from a single particle LiMn 2 O 4 electrode and implemented into a three-dimensional multiphysics simulation of a single particle, in order to demonstrate a novel approach to electrode material study. Dispersed particles were used, and electrochemical techniques and atomic force microscopy were performed on isolated single particles. Diffusion coefficients measured from both cyclic voltammetry and the potentiostatic intermittent titration technique ranged between 3.2 Â 10 À12 and 1.2 Â 10 À11 cm 2 /s, which was similar to values measured from thin film LiMn 2 O 4 electrodes. The trend of diffusivity change over potential (versus lithium counter electrode) was similar to those observed from both composite cells and thin film electrodes. The measured diffusion coefficients were then used in simulation of discharge of the irregular particle, by importing the particle morphology into a finite element simulation, in order to simulate intercalation-induced stress generation. Simulation results showed a higher maximum stress generation due to altering diffusivity around the peak current potentials and high local stress concentration on the sharply indented surface area, suggesting that particle irregularities are important in studying both electrochemical performance and local failure mechanisms in cathode materials.

Na0.44MnO2 with very fast sodium diffusion and stable cycling synthesized via polyvinylpyrrolidone-combustion method

“…9. The sodium diffusion values vary considerably with concentration from 1.5 Â 10 À12 cm 2 s À1 to 2.7 Â 10 À10 cm 2 s À1 which are much higher than previous reports and comparable with LiMn 2 O 4 [57]. From 2 V to 3.46 V, the D Na þ values vary around 3 Â 10 À12 cm 2 s À1 with small amplitude.…”

Synthesis of spinel LiNi0.5Mn1.5O4 cathode material with excellent cycle stability using urea-based sol–gel method

“…where n is the number of electrons involved in the electrochemical reaction (n¼ 2), A is the surface area of the electrode, and C 0 Li is the bulk concentration of Li þ in the electrode (0.0244 mol cm À 3 ) [1,14], u is the potential sweeping rate (V s À 1 ). The calculated D Li in this case is 3.2 Â 10 À 11 cm 2 s À 1 which is identical with the values reported previously and even better than some [1,15], indicating higher lithium ion diffusion kinetics in the material.…”

Li transport in fresh and aged LiMn2O4 cathodes via electrochemical strain microscopy

“…Taking into account a complex dependence of the Li diffusion coefficient on Li concentration, 33 the observed change of the loop's shape can indicate also a wider variation of the Li diffusion coefficient over the dc voltage cycle in the aged sample.…”