A Pseudo-Two-Dimensional (P2D) Model for FeS2 Conversion Cathode Batteries

TL;DR

This paper introduces a pseudo-two-dimensional model for FeS2 conversion cathodes, highlighting key loss mechanisms and providing an open-source tool to analyze performance limitations in such batteries.

Contribution

The paper develops a novel P2D model for conversion cathodes, incorporating polydispersity and resistance effects, and offers an open-source implementation for broader application.

Findings

Solid-state diffusion and electrical transport limit performance.

Polydispersity affects capacity loss during conversion.

Model code is available as open-source PyBaMM.

Abstract

Conversion cathode materials are gaining interest for secondary batteries due to their high theoretical energy and power density. However, practical application as a secondary battery material is currently limited by practical issues such as poor cyclability. To better understand these materials, we have developed a pseudo-two-dimensional model for conversion cathodes. We apply this model to FeS2 - a material that undergoes intercalation followed by conversion during discharge. The model is derived from the half-cell Doyle-Fuller-Newman model with additional loss terms added to reflect the converted shell resistance as the reaction progresses. We also account for polydisperse active material particles by incorporating a variable active surface area and effective particle radius. Using the model, we show that the leading loss mechanisms for FeS2 are associated with solid-state diffusion and electrical transport limitations through the converted shell material. The polydisperse simulations are also compared to a monodisperse system, and we show that polydispersity has very little effect on the intercalation behavior yet leads to capacity loss during the conversion reaction. We provide the code as an open-source Python Battery Mathematical Modelling (PyBaMM) model that can be used to identify performance limitations for other conversion cathode materials.