Energy Density Comparison of Li-ion Cathode Materials Using Dimensional Analysis

Abstract

A surrogate modeling framework is implemented to analyze the performance of a Li-ion cell with respect to four input variables: cycling rate, particle size, diffusivity, and electrical conductivity. Five different cathode materials (LiMn2O4, LiFePO4, LiCoO2, LiV6O13, and LiTiS2) are modeled, and ranges for all material properties are selected based on reported data from the literature. The relative impact of the variables is quantified using global sensitivity analysis, and critical diffusivity and conductivity values are calculated. Two dimensionless parameters based on relative time and conductivity scales are defined and found to separate operating conditions into distinct regimes in which the cell performance is limited by diffusion or conduction. Combining the two dimensionless parameters into a single quantity and non-dimensionalizing the energy performance yields a Pareto-efficient set of solutions that are described well by the generalized logistic function, which can be considered a reduced-order model of battery performance with a global analytical solution. (C) 2013 The Electrochemical Society.