Simulation study of rate limiting factors of Li-ion batteries using experimental functions of electronic and ionic resistances

Abstract

The balance between the electronic and ionic resistances in electrodes is an important factor that governs the rate performance of Li-ion batteries. However, most battery simulation models reported to date use impractical formulas. We therefore conducted a simulation study using the Newman model under the constraint condition of constant energy density (250 Wh/kg), using the experimental functions of electronic and ionic resistances depending on the electrode structure. In addition to obtaining a battery design guideline that provides the best rate performance, we considered the rate-limiting factors. Using the conductive carbon weight ratio and the porosity and thickness of the positive electrode as the design parameters, we carried out a parametric study of the discharge properties. The batteries comprising a thin, low-porosity positive electrode exhibited better rate performances than those with a thick positive electrode of higher porosity for the design parameter sets with the same designed specific energy. Furthermore, the results revealed that the dependence on the electrode thickness of the diffusion-limiting behavior and thus, of the discharge rate performance was determined by the diffusivity of both the positive and negative electrodes.