Constructing Superionic Heterointerface via Multiphase Engineering to Achieve Stable Oxyhalide‐Based All‐Solid‐State Batteries

ABSTRACT Amorphous oxyhalides attract great interest as solid‐state electrolytes (SSEs) in all‐solid‐state batteries (ASSBs) because of their oxidative stability, low cost, and mechanical deformability. But the limited room‐temperature ionic conductivity and the parasitic reactions on cathode/halide interfaces impede their practical applications. Herein, we adopt a facile multiphase regulation strategy by incorporating ZrB 2 and ZrN into an amorphous 1.3Li 2 O‐ZrCl 4 (LZCO) matrix to simultaneously enhance Li + transport and interfacial stability. ZrB 2 and ZrN regulate the bridging‐oxygen/non‐bridging‐oxygen ratio to promote amorphization and create superionic heterointerfaces, which enables a more continuous Li + conduction network while preserving overall electronic insulation. The multiphase architecture mitigates the interfacial side reactions, improves the interface compatibility due to the formation of B‐O and N‐O bonds, and homogenizes electron transport pathways in the composite cathode. As a result, 1.3Li 2 O‐0.8ZrCl 4 ‐0.1ZrB 2 ‐0.1ZrN (LZCOBN 0.1 ) shows a high room‐temperature ionic conductivity of 2.41 mS cm −1 , compared with 1.3 mS cm −1 for pristine LZCO. ASSBs employing LZCOBN 0.1 and LiNi 0.90 Co 0.05 Mn 0.05 O 2 deliver a high initial capacity of 210 mAh g −1 at 0.1 C and retain 82.7% capacity after 2000 cycles at 3 C, demonstrating ultrahigh cycling stability. This work highlights the potential of phase engineering regulation in developing high‐performance amorphous oxyhalide‐based ASSBs.