Predicting Electrochemical Stability Window of Polymer Electrolytes with First-Principles Approaches

Polymer electrolytes in lithium-ion batteries represent an emerging paradigm for energy storage by offering numerous advantages over liquid or solid electrolytes through enhanced resistance to variations in volume of electrodes during charge/discharge process, safety, flexibility, and processability. Overcoming the current limitations of polymer electrolytes necessitates a fundamental understanding of their electrochemical stability window (ESW), which controls polymer electrolyte performance and degradation during charge/discharge cycles. First-principles simulations can provide valuable insights into such properties. However, the widely used density functional theory (DFT) unfortunately engender foundational errors, resulting in incorrect frontier-orbital and band gaps. Here, we carry out a systematic study to accurately and efficiently predict ESW of selected polymer electrolytes. We first identify the most accurate correlated wavefunction (CW) theory methods in predicting ESW of polymers of which experimental data is available. We then develop DFT approximations with enhanced predictive capabilities validated using the CW-predicted properties. These efforts pave the way to reconcile DFT against more computationally demanding approaches and thereby retrieve higher level of accuracy with low computational cost. Our work also assists in the rational design of novel polymer electrolytes with improved electrochemical and physical properties.