Physics based modeling of LiFePO4 cathodes: effects of electrode parameters on cell performance during fast charging

Abstract

Lithium-iron phosphate (LFP) has emerged as a potential cathode material due to its lower cost and higher stabilities. This work investigates LFP cell behavior at higher C-rates via a detailed simulation study. To facilitate this investigation, a physics-based electrochemical model is calibrated and validated with in-house experimental data. The validated model is used to study the effect of particle size, lithium diffusivity, and electrode thickness on the charge-discharge capacity of Li-LFP cells for a range of C-rates up to 5 C. A detailed discussion is carried out to explain the results of parametric studies, in terms of transport limitations, irreversible losses (overpotentials) and their dependence on different electrode parameters. The model helps us to depict the effect of these parameters on internal profiles of SOC and overpotentials, allowing for a deeper understanding of the cell behavior. Overall, the simulations show that the LFP cell is able to exhibit good capacity at higher C-rates by tuning the particle size and lithium diffusivity. An optimal combination of material and physical parameters is identified to maximize the possible capacity of LFP electrodes.

Keywords

• physics
• LiFePO4
• cathodes
• energy storage
• lithium-ion batteries
• fast charging