Atomic‐Level Coupled Interfaces and Lattice Distortion on CuS/NiS2 Nanocrystals Boost Oxygen Catalysis for Flexible Zn‐Air Batteries

Abstract The exploration of highly efficient nonprecious metal bifunctional electrocatalysts to boost oxygen evolution reaction and oxygen reduction reaction is critical for development of high energy density metal‐air batteries. Herein, a class of CuS/NiS 2 interface nanocrystals (INs) catalysts with atomic‐level coupled nanointerface, subtle lattice distortion, and plentiful vacancy defects is reported. The results from temperature‐dependent in situ synchrotron‐based X‐ray absorption fine spectroscopy and electron spin resonance spectroscopy demonstrate that the lattice distortion of 14.7% in CuS/NiS 2 caused by the strong Jahn–Teller effect of Cu, the strong atomic‐level coupled interface of CuS and NiS 2 domains, and distinct vacancy defects can provide numerous effective active sites for their excellent bifunctional performance. A liquid Zn‐air battery with the CuS/NiS 2 INs as air electrode displays a large peak power density (172.4 mW cm −2 ), a high specific capacity (775 mAh g Zn −1 ), and long cycle life (up to 83 h), making the CuS/NiS 2 INs among the best bifunctional catalysts for Zn‐air battery. More remarkably, the flexible CuS/NiS 2 INs‐based solid‐state Zn‐air batteries can power the LED after twisting, making them be promising in portable and wearable electronic devices.