Mesoscale Modeling of a Li-Ion Polymer Cell

Finite element models of a three-dimensional, porous cathode were constructed and analyzed by the COMSOL multiphysics package version 3.2 . Four types of cathode active material particles, arranged in both regular and random arrays, were modeled. Experimental studies of Li/PEO-LiClO4/Li1+xMn2O4 where 0 x 1 were used to validate simulation results. Two parameters, Li ion diffusivity into Li1+xMn2O4 particles, and contact resistance at the interface between cathode particles and the current collector, were obtained by curve-fitting discharge curves of simulation results of regular array models, with Li1+xMn2O4 particles 3.6 m with experimental results. Diffusivities of Li ions were found to be 4 10−13, 6 10−13, 1 10−12, and 5 10−12 cm2/s for Li1+xMn2O4 particles sintered at 800, 600, 500, and 450°C, respectively. Contact resistances were found to be 3.5 cm2 for Li1+xMn2O4 particles prepared at 600 and 800°C, and 10.5 cm 2 for particles prepared at 450 and 500°C. Regular arrays were shown to increase achievable capacity from 5 to 50% of the theoretical capacity, compared with random arrays, at C/10 for samples sintered at 500°C. Smaller particle sizes of active material particles were also shown to be beneficial for high power density applications and for low diffusivity active materials. © 2007 The Electrochemical Society. DOI: 10.1149/1.2778285 All rights reserved.