Ab Initio Prediction of Metal Phosphide Anode Materials for Li and Beyond Li Batteries

The growing need for sustainable energy storage devices demands research into rechargeable batteries. While Li-ion batteries (LIBs) currently dominate the field, LIB technology contains two main limitations: first, the dwindling abundance of Li, and second the efficiency of the electrode materials used. Thus, Na-ion batteries (SIBs) have received increased attention, given the relatively high abundance of Na, and metal phosphide anodes have been shown experimentally to undergo a favorable conversion mechanism and good conduction in both NIBs and SIBs.
To address both issues, an automated computational approach is employed which predicts novel anode materials from first principles calculations. The ab initio Random Structure Searching method (AIRSS) is used to search for the initial anode structures, and a ternary convex hull is constructed between these transition metals, phosphides, and either Li or Na. All the calculations are performed using plane-wave density-functional theory (DFT) with the CASTEP code. Structures close to the hull are further studied to elucidate the chemical transformations undergone during lithiation or sodiation. From this high-throughput method we are able to predict and understand the chemical mechanisms of novel transition metal phosphide anodes.