Introducing 3 s/p-3p orbital hybridization to stabilize and activate Ni3S4 for efficient hydroxyl ion storage

Abstract

Transition metal sulfides have been identified as promising battery type electrode materials for supercapacitor (SC) owing to their exceptional conductivity and substantial theoretical capacities. However, the fast SC capacity decay often occurs, which is attributed to the instability of the sulfur framework caused by the presence of metal cations with strong Jahn-Teller distortion and/or limited orbital interactions between cations and sulfur (primarily involving 3d–3p interaction). Herein, we successfully develop a robust and durable sulfur framework through incorporating intense 3 s/p–3p orbital hybridization into the structure, with Ni₃S₄ serving as a representative example. The modified sulfide exhibits exceptional stability in SC performance, achieving 93.1% capacity retention after 10,000 cycles at a higher current density of 20 A g^-1. Moreover, this orbital hybridization strategy also well regulates the d-band center of Ni and introduces the S vacancies, which not only promotes adsorption of the OH^- ions but also renders lower diffusion barrier, thus realizing larger specific capacity of 295 mAh g^-1 at a current density of 1 A g^-1 and fast reaction kinetics. This study provides a new perspective to understand the structural stability and offers new opportunities to extend sulfide electrodes enabling high performance through modification in orbital interaction.