Cathode-Contact Stability and Li Diffusivity of N-Doped Li₆Zr₂O₇ for All-Solid-State Li-Ion Batteries by First-Principles Density Functional Theory Methods

Oxide-type solid electrolytes with high lithium ionic conductivity, good (electro)chemical stability, and excellent safety are key towards unlocking the full commercialization of all-solid-state Li-ion batteries. Here, N-doped Li₆Zr₂O₇ (LZON) is studied by first-principles density functional theory methods to evaluate the material’s chemical and electrochemical stability and Li-ion diffusion properties for its novel design as a practical dual-use Li ionic conductor, both as a cathode-coating layer (CCL) and solid electrolyte (SE) in all-solid-state Li-ion batteries (ASSBs).¹ Thermodynamic free energy calculations reveal that pristine LZO is chemically stable versus most known cathode materials. Focusing on LiCoO₂ (LCO) cathode, the low-energy LCO(104)|LZO(001) interface is predicted to demonstrate strong adherence and a low strain, its electronic structure has LCO-side states (Co-3d, O-2p) occupying the highest occupied states, resulting to cathode-CCL/SE interface that can facilitate stable cell charging. Climbing-image nudged elastic band calculations results show that the LCO(104)|LZO(001) interface also has interface-perpendicular local migration pathways with low Li ion migration energy. On the other hand, first-principles- and machine-learning-based molecular dynamics simulations show that the Li diffusivity in bulk LZO can be significantly increased by several orders of magnitude via aliovalent N-doping at the O site. Also, for the LCO(104)|LZON(001) interface, the N dopant anion is determined to energetically prefer to stay away from the interface, making the interface’s electronic structure similar to that of the LCO(104)|LZO(001) interface.

Reference:

1. Randy Jalem, Yoshitaka Tateyama, Kazunori Takada, Tetsuya Yamada, Katsuya Teshima. First-principles study on the interfacial cathode-contact stability and Li diffusivity of N-doped Li₆Zr₂O₇ for all-solid-state Li-ion batteries. Small Methods 2025, e01289.