First‐Principles Study on the Interfacial Cathode‐Contact Stability and Li Diffusivity of N‐Doped Li₆Zr₂O₇ for All‐Solid‐State Li‐Ion Batteries

Here, N‐doped Li 6 Zr 2 O 7 (LZON) is investigated using first‐principles density functional theory (DFT) methods to evaluate its (electro)chemical stability and Li‐ion transport 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). Thermodynamic free energy calculations showed that LZO, as CCL and SE, is chemically stable versus most known cathode materials. Focusing on LiCoO 2 (LCO) cathode, explicit hetero‐interface modeling analysis of the low‐energy LCO(104)|LZO(001) interface revealed that LZO can form a strongly adhered and a low‐strain contact with LCO. The electronic structure of this interface has LCO‐side states (Co‐3d, O‐2p) occupying the highest occupied states, thereby facilitating a stable cell charging. Climbing‐image nudged elastic band calculations results suggested that the LCO(104)|LZO(001) interface also has interface‐normal diffusion pathways with low Li ion migration energy. Meanwhile, ab‐initio ‐ and machine‐learning‐based molecular dynamics simulation results confirmed that Li diffusivity in bulk LZO can be greatly enhanced by several orders of magnitude via aliovalent N‐doping with Li interstitial addition. For the LCO(104)|LZON(001) interface, the N dopant is determined to energetically prefer the LZON bulk region, the corresponding interface electronic structure that can also facilitate a stable ASSB cell charging.