This repository accompanies the paper Computational Investigation of Copper Phosphides as Conversion Anodes for Lithium-Ion Batteries by Angela Harper, Matthew Evans & Andrew Morris (ChemMater and arXiv 2005.05375).

The notebook CuP_results.ipynb can be explored interactively with Binder, which provides functionality to pull the raw data from the University of Cambridge repository once it has been made available.

Paper abstract

Using first principles structure searching we identify a novel Fm-3m phase of Cu₂P and two low-lying metastable structures, an I43d-Cu₃P phase, and a Cm-Cu₃P₁₁ phase. Pair distribution functions of the novel Cm-Cu₃P₁₁ phase show its structural similarity to the experimentally identified Cm-Cu₂P₇ phase. The relative stability of all Cu-P phases at finite temperatures is determined by calculating the Gibbs Free energy using vibrational effects from phonon modes at 0 K. From this, a finite-temperature convex hull is created, on which Fm-3m-Cu₂P is dynamically stable and the Cu_(3-x)P (x<<2) defect phase Cmc2₁-Cu₈P₃ remains metastable (within 10 meV/atom of the convex hull) across a temperature range from 0 K to 600 K. Both CuP₂ and Cu₃P exhibit theoretical gravimetric capacities higher than contemporary graphite anodes. The predicted Cu₂P composition has a theoretical gravimetric capacity of 508 mAh/g as a Li-ion battery electrode, greater than both Cu₃P (363 mAh/g) and graphite (372 mAh/g). Cu₂P is also predicted to be both non-magnetic and metallic, which should promote efficient electron transfer in the anode. Cu₂P's favorable properties as a metallic, high-capacity material suggest its use as a future conversion anode for Li-ion batteries; with a volume expansion of 99% during complete cycling, Cu₂P anodes could be more durable than other conversion anodes in the Cu-P system with volume expansions greater than 150%.