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

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.