Electro-Chemo-Mechanical Model for Polymer Electrolytes

Abstract

Polymer electrolytes (PEs) are promising candidates for use in next-generation high-voltage batteries, as they possess advantageous elastic and electrochemical properties. However, PEs still suffer from low ionic conductivity and need to be operated at higher temperatures. Furthermore, the wide variety of different types of PEs and the complexity of the internal interactions constitute challenging tasks for progressing towards a systematic understanding of PEs. Here, we present a continuum transport theory which enables a straight-forward and thermodynamically consistent method to couple different aspects of PEs relevant for battery performance. Our approach combines mechanics and electrochemistry in non-equilibrium thermodynamics, and is based on modeling the free energy, which comprises all relevant bulk properties. In our model, the dynamics of the polymer-based electrolyte are formulated relative to the highly elastic structure of the polymer. For validation, we discuss a benchmark polymer electrolyte. Based on our theoretical description, we perform numerical simulations and compare the results with data from the literature. In addition, we apply our theoretical framework to a novel type of single-ion conducting PE and derive a detailed understanding of the internal dynamics.