A scheme for the generation of Fe-P networks to search for low-energy LiFePO4 crystal structures

Herein we present a network generation scheme to explore the structural diversity of LiFePO4, which is an important cathode material in Li-ion batteries. With our scheme, networks of Fe and P atoms were initially constructed as the backbone structures using structural motifs for the FePx and FePx configurations, obtained from existing structural databases. Then, O atoms were added, resulting in the formation of PO4 tetrahedra and different types of Fe-O polyhedra. Finally, Li atoms were inserted into the vacancies within the generated FePO4 structures. We searched structures with FeO4, FeO5, or FeO6 polyhedra (unit cell with sizes of up to 4 formula units) and obtained similar to 8 times more low-energy structures through our database than through existing databases. Furthermore, using our more comprehensive structural database, we unveiled a number of rules for identifying low-energy structures. These improved results complement the existing databases and are valuable for further research on structural transformations in similar materials by changing lithium or sodium cation populations.