Computational Design of Cation-Disordered Li₃Ta₂O₅ with Fast Ion Diffusion Dynamics and Rich Redox Chemistry for a High-Rate Li-Ion Battery Anode Material

Abstract

Disordered rock salt transition-metal oxides have emerged recently as promising electrodes for Li-ion batteries (LIBs). However, only two disordered rock salt (DRX) materials, Li 3 V 2 O 5 and Li 3 Nb 2 O 5 , have been studied as anodes so far, leaving numerous DRX compounds with vast compositions and exotic battery-related performance unexplored. Here, based on theoretical analyses and calculations, we propose a Ta pentoxide-based DRX anode with rich electrochemical properties, where the thermodynamic stability, average voltage, energy density, redox chemistry, and cation mobility are studied. Our results show that DRX-Li 3 Ta 2 O 5 can cycle three Li ions at an average voltage of 1.27 V, which is higher than that of DRX-Li 3 V 2 O 5 (0.73 V) but lower than that of DRX-Li 3 Nb 2 O 5 (1.76 V), falling in the optimal range for the high rate performance. More importantly, DRX-Li 3 Ta 2 O 5 exhibits a superhigh volumetric capacity of 1336 mAh cm −3 , which surpasses that of graphite, Li 4 Ti 5 O 12 , and DRX-Li 3 V 2 O 5 . Meanwhile, the unique geometry of DRX-Li 3 Ta 2 O 5 allows Li + to diffuse rapidly through channels with low diffusion energy barriers, and Ta 2 O 5 is electronically activated by inserting Li + into the available octahedral sites with enhanced orbital overlapping. Our work expands the family of DRX anode materials with new features.