Effect of heteroatom doping on the charge storage and operating voltage window of nickel-based sulfide composite electrodes in alkaline electrolytes

Broadening the voltage window of nickel-based sulfide composite electrodes in alkaline electrolytes is enormously challenging. In prior work, the voltage window of nickel-based sulfide composite electrodes was broadened to 1.8 V (−0.5–1.3 V. vs SCE). Herein, the voltage window widening mechanism of nickel-based sulfide composite electrodes in alkaline electrolytes is discussed in detail. Our results show that co-doped boron and nitrogen atoms and sulfur vacancies increase the number of electrochemical energy storage sites and accelerate the electrochemical reaction, thereby enhancing charge storage. Additionally, heteroatom doping and the presence of sulfur vacancies can effectively inhibit the water decomposition reaction, broadening the voltage window of nickel-based sulfide composite electrodes in alkaline electrolytes and even exceeding the thermodynamic limit of water. Introducing a mesoporous structure increases the electrolyte storage space, accelerating the OH− transfer and charge transfer dynamics. Aqueous and all-solid-state asymmetric supercapacitor devices are assembled, and at a power density of 1800 W kg−1, the aqueous asymmetric device can obtain a high energy density of 56 Wh kg−1. The all-solid-state asymmetric device shows a high energy density of 49.72 Wh kg−1 at a power density of 1000 W kg−1. A theoretical basis is provided for preparing high-energy nickel-based sulfide supercapacitors with a wide voltage window.